HomeMy WebLinkAboutCT 00-06; BRESSI RANCH MASTER; INDUSTRIAL CONCEPT WATER QUALITY; 2002-04-01INDUSTRIAL CONCEPT WATER
OUALITY PLAN
FOR
BRESSI RANCH, TM CT 00-06
CITY OF CARLSBAD, CA
APRIL 2002
Prepared For:
LENNAR COMMUNITIES
c/o LENNAR BRESSI VENTURE, LLC
5780 Fleet Street, Suite 320
Carlsbad, CA 92008
Prepared By:
PROJECTDESIGN CONSULTANTS
701 B Street, Suite 800
San Diego, CA 92101
Job No. 1325.00
TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1
2.0 NPDES INDUSTRIAL AND MUNICIPAL PERMIT PROCESS 4
3.0 INDUSTRIAL POLLUTANT LOADS 5
4.0 BMP POLLUTANT REMOVAL EFFICIENCY 7
5.0 PROJECT BMP DESIGN CRITERIA 8
6.0 PROJECT BMP DESIGN RESULTS 9
7.0 INDUSTRIAL BMP PLAN IMPLEMENTATION 10
7.1 Project BMP Source Control Options 11
7.2 Project BMP Treatment Control Options 12
8.0 CONCLUSION 14
FIGURES
1 Vicinity Map 3
TABLES
1 Industrial Land Use Pollutants and Concentrations 6
2 PA Industrial Pollutant Loads A-l
3 BMP Treatment Controls 7
4 BMP Pollutant Removal Efficiency 8
5 BMP Design Criteria 9
6 Grass Lined Biofilter BMP Discharge and Treatment Area A-3
7 Individual Planning Area Wet Pond/Retention Basin Treatment Volumes A-4
and Basin Geometries
8 Combined Planning Area Wet Pond/Retention Basin Treatment Volumes A-5
and Basin Geometries
REPORT/1325ICWQP.DOC jj
APPENDICES
1 Planning Area Pollutant Loads and Support Documentation
2 Nationwide BMP Treatment Controls
3 Table 6: Grass Lined Biofilter BMP Discharge and Treatment Area
4 Table 7: Individual Planning Area Wet Pond/Retention Basin Treatment
Volumes and Basin Geometries
5 Table 8: Combined Planning Area Wet Pond/Retention Basin Treatment
Volumes and Basin Geometries
6 Industrial Storm Water Source Control BMPs
7 Industrial/Municipal Storm Water Treatment Controls
8 Industrial/Municipal Proprietary BMPs
EXHIBITS
A Site Layout Map
REPORT/1325ICWQP.DOC jjj
1.0 INTRODUCTION
This report provides a "concept" water quality plan for the industrial land use component of the
Bressi Ranch environmental document. The property, which totals approximately 585.1 acres, is
located southeast of the intersection of El Camino Real and Palomar Airport Road in the City of
Carlsbad, Califomia (see Figure 1: Vicinity Map on page 3)). The site consists of an irregular-
shaped piece of property, which is bound by: 1) Palomar Airport Road to the north; 2) El Camino
Real to the west; 3) undeveloped property to the south; and 4) the Rancho Carrillo development
to the east. The Tentative Map proposes to develop 623 dwelling units and 2,160,000 square feet
of industrial space. The industrial PAs are identified as PA-1, PA-2, PA-3a, PA-3b, and PA-4
and PA-5 on Exhibit A.
From a drainage perspective, existing land use conditions (open space) generate approximately
705- and 52-cubic feet per second (cfs), which drain to Batiquitos Lagoon and the Encinas Creek
watershed, respectively. Under developed land use conditions the entire Bressi Ranch
development drains to Batiquitos Lagoon. This includes 444 cfs from the industrial PAs and 621
cfs from the residential PAs. Note that detention basins, located along the southerly edge of the
Bressi Ranch boundary, will be used to attenuate storm runoff back to existing conditions. The
preceding storm water runoff information was acquired from the, "Preliminary Drainage Report
for Bressi Ranch Planning Area 1-14 and Open Space 1-6", March 2000, prepared by
ProjectDesign Consultants. Note that storm runoff under both existing and proposed site
conditions do not drain to Agua Hedionda Lagoon.
Conceming water quality, the industrial PAs will generate approximately 26.7 cfs of storm water
treatment mnoff and approximately 306,444 cubic feet of treatment volume, per the numeric
sizing criteria presented in San Diego Regional Water Quality Control Board (RWQCB) Order
Number 2001-01 (Order 2001-01). Section 2.0 provides a detailed discussion of the numeric
sizing criteria.
It is important to note that during final engineering other treatment control BMPs may be
included in the BMP plan options presented herein. In effect, this documents lays the
REPORT/1325ICWQP.DOC 1
groundwork for the development of future industrial water quality plans by each Planning Area
(PA) industrial user. In general, this report includes the following:
An overview of the industrial and municipal permit process;
Existing and proposed land use condition pollutant load analysis;
"Concept" Best Management Practices (BMP) volume- and flow-based) design
hydrology;
"Concept" geometric requirements for retention and grass-lined BMPs, per the design
hydrology;
Selection of additional source and treatment control industrial BMPs that may be
evaluated for use by the industrial users during final engineering;
"Concept" project BMP water quality plan options for this project; and
Manufactures information for proprietary industrial BMP devices.
REPORT/13251CWQP.DOC
Project site.
-MELROSE
DRIVE
-POINSEniA
LANE
Figure 1. Vicinity Map
REP/I3255PDR.DOC
2.0 NPDES INDUSTRIAL AND MUNICIPAL PERMIT PROCESS
The Califomia State Water Quality Control Board (SWQCB) Order Number 97-03-DWQ (Order
97-03), National Pollutant Discharge Elimination System (NPDES) General Permit Number
CASOOOOOl, will regulate storm water discharges from the proposed industrial Planning Areas
(PA) associated with the Bressi Ranch Development. Order 97-03 generally requires industrial
facility operators to:
Eliminate unauthorized non-storm water discharges;
Develop and implement a storm water pollution prevention plan (SWPPP); and
Perform monitoring of storm water discharges and authorized non-storm water
discharges.
In addition, industrial storm water discharges from the PAs that enter the public, or municipal
storm drain system, are also regulated by Order 2001-01 that specifies storm water discharge
requirements for discharges of urban runoff from municipal storm drain systems. From a design
perspective. Order 2001-01 sets hydrologic criteria required for the evaluation and design of
industrial and municipal Best Management Practices (BMPs).
The BMP hydrologic design criteria, pursuant to regional Order 2001-01, are either volume- or
flow-based. Specifically, volume-based BMPs must be designed to treat the volume of runoff
produced from a 24-hour 85* percentile storm event. In general, this is equal to 0.6 inches of
mnoff for San Diego County. Examples of volume based BMPs are retention/wetland ponds and
extended duration detention basins.
Flow-based BMPs must be designed to treat a flow rate of 0.2 inches of rainfall per hour. In
general, regardless of the criteria used, storm flow must be removed and treated before re-
entering the storm drain system. Examples of flow based treatment control BMPs include grass-
lined swales and CDS units.
REP0RT/13251CWQP.D0C
In addition to treatment controls, source controls BMPs are a key component of the industrial
water quality SWPPP. Good house keeping practices are the key source control BMPs, which are
primarily used to prevent or mitigate the exposure of industrial materials, i.e. significant
pollutants, to rain. These BMPs may primarily include indoor storage, outdoor covered storage,
and containment structure.
3.0 INDUSTRIAL POLLUTANT LOADS
The "Guidance Manual for the Preparation of Part lof the NPDES Permit Application for the
Discharges from Municipal Separate Storm Sewer Systems, EPA 1991, outlines an analytical
methodology for the evaluation of seasonal and/or annual pollutant loads. This approach
accounts for land use, impervious area, and anticipated mean pollutant concentrations for a given
the land use. Note that the pollutant concentration is primarily based on Nationwide Urban
Runoff Program (NURP) data and Camp Dresser McKee Inc. (CDM) pilot studies. The
equations used in the analysis are as follows:
RL=[CP+(CI-CP)IMPL]*I (1)
Where: RL = total average annual surface mnoff from land use L (in/yr)
IMPL = fractional imperviousness of land use L from Table 2
I = long-term average annual precipitation (in/yr)
Cp = pervious area mnoff coefficient = 0.15
Cl = impervious area mnoff coefficient = 0.90
And;
ML=[EMCL*RL*K*AL]*I (2)
Where: ML= loading factor for land use L (Ib/yr)
EMCL=event mean concentration of mnoff for the lands use (mg/L): varies by
land use and pollutant
RL=total average annual surface mnoff from land use L computed from equation
1 (in/yr)
REPORT/1325ICWQP.DOC r
K=0.226 (unit conversion)
AL=area of land use L (acres)
Conceming existing and developed conditions pollutant loading for this project. Table 1 below
lists anticipated pollutants and concentrations that could be generated from the existing drainage
areas (as defined by the boundary limits of PAs 1-5) and PAs 1-5. The types and concentrations
of pollutants, per the NURP and CDM data, are documented in the Municipal Califomia Storm
Water Best Management Practice Handbook (Municipal Manual). See Appendix 1, Table 2, for
pollutant load estimates for each land use condition. Also, Appendix 1 contains the support
documentation for the EPA pollutant load analysis methodology, and the existing open space and
industrial land use pollutant concentrations shown in Table 1 below.
Table 1: Existing and Industrial Land Use Poiiutants and Concentrations
Description Open Space Industrial
Mg/L Mg/L
Oxygen Demand and Sediment: BOD 8.0 9.7
COD 51.0 61.0
TSS 216.0 91.0
TDS 100.0 100.0
Nutrients: TP 0.23 0.24
SP 0.06 0.10
TKN 1.36 1.28
N02/N03 0.73 0.63
Heavy Metals: Pb 0.00 0.13
Cu 0.00 0.04
Zn 0.00 0.33
Cd 0.00 0.002
0.00
Total: 377.4 mg/ 264.5 mg/L
*The pollutant loads are based on a commercial/office/industrial development with 70%
to 90% imperviousness.
REPORT/1325ICWQP.DOC
Table 1 shows that the total pollutant load under existing land use conditions is higher than under
developed conditions. This is primarily due to the high TSS concentration (sediment) that is
generated under existing open space conditions. This value may be high due to the good quality
of the vegetative cover, which protects the watershed from erosion. Note; however, that the
remaining pollutants loads under developed conditions are higher than those identified under
existing conditions. This is typically of an open space watershed that is developed for residential
and/or industrial land use. The results of the pollutant load analysis show that the existing open
space and industrial land uses generate pollutant loads of 18,543 Ib/yr and 63,292 Ib/yr,
respectively. See Appendix 1, Table 2, for the analysis.
The following Sections address project specific BMPs and BMP plan implementation. However,
Table 3 below lists a variety of effective treatment control BMPs for each pollutant category
above. In addition, more detailed BMP technical backup information is included in Appendix 5.
Table 3: BMP Treatment Controls
Description Most Effective BMP Adequate BMP
Oxygen Demand and Sediment: Infiltration
Constmcted Wetlands
Wet ponds
Biofilters
Extended Ponds
Media filtration
Oil/water sep.
Multiple systems
Nutrients Constmcted Wetlands Infiltration
Wet ponds
Biofilters
Extended ponds
Media filtration
Oil/water sep.
Multiple systems
Heavy Metals Infiltration
Constmcted wetlands
Wet ponds
Biofilters
Extended ponds
Media filtration
Oil/water sep.
Multiple systems
Oil and Grease Infiltration
Constmcted Wetlands
Oil/water sep.
Wet ponds & Biofilters
Extended ponds
Media filtration
Multiple systems
REPORT/1325ICWQP.DOC
4.0 BMP POLLUTANT REMOVAL EFFICIENCY
In general, a number of engineering and climatic conditions ultimately affect the selection of MP
treatment controls used in a project water quality SWPPP plan. A critical path item in the BMP
selection process is the contaminant removal efficiency associated with treatment control BMPs.
Table 4 below identifies typical contaminant removal rates for a number of BMPs. In addition.
Appendix 2 contains a matrix that includes a detailed list of BMP treatment controls and
associated benefits and pollutant removal efficiencies. Listed at the end of this document are the
references used in the development of the data.
Table 4: BMP Pollutant Removal Efficiency
BMP Type Suspended
Solids
Nitrogen Phosphorous Pathogens Metals
Dry Detention
Basin
30-65 15-45 15-45 <30 15-45
Retention
Basins
50-80 30-65 30-65 <30 50-80
Constructed
Wetlands
50-80 <30 15-45 <30 50-80
Inflitration
Basins
50-80 50-80 50-80 65-100 50-80
Porous
Pavement
65-100 65-100 30-65 65-100 65-100
Grass swales 30-65 15-45 15-45 <30 15-45
Vegetated
Filter Strips
50-80 50-80 50-80 <30 30-65
5.0 PROJECT BMP DESIGN CRITERIA
Grass-lined bio-filters/strips and retention/wetland basins have been identified as potential BMP
candidates for this project. The design of these BMPs is primarily based on the numeric sizing
criteria defined in Section 2.0. In general. Table 5: below summarizes the criteria that should be
implemented in the design of these BMPs:
REPORT/I325ICWQP.DOC
Table 5: BMP Design Criteria
BMP BMP Hydrology Treatment Area/Volume Design Constraints
Grass-hned
Biofilter/Strip
Flow-based: 0=CIA
1 = 2 in/hour over
C= mnoff coefficient
A = PA acreage
1000 sqft. of biofilter/acre
of impervious area.
Use geometry and
longitudinal slope that
maintain sheet flow and low
conveyance velocities.
Retention
Basin/Wetland
Pond
Volume based: .6-
inches of mnoff
.6-inches of mnoff over
the impervious portion of
the drainage area.
Potential soil and ground
water constraints must be
addressed before selecting
this BMP. Geotechical and
City must be consulted
regarding these issues.
Retention time should range
between 40 and 72 hours to
promote treatment efficiency
and control for vector control.
6.0 PROJECT BMP DESIGN RESULTS
Biofilter/Strips
The Rational Method was used to determine the biofilter flow-based design discharge for each
individual PA. The hydrologic analyses, which are located Appendix 3, Table 6, were used to
determine the required biofilter treatment area and length required to treat the storm water within
a 50-foot buffer zone (width) that is located along the northerly edge of the project. The biofilter
treatment area and length are also included in Table 6.
The results of the analysis show that a biofilter, if used as the sole BMP for the project PAs, will
require a significant amount of area to effectively treat storm water. PA design options to reduce
biofilter treatment area would be to: 1) increase pervious area throughout the industrial complex
with planters and gravel walkways etc.; and/or 2) incorporate mechanical treatment control
BMPs such as CDS units etc. into the water quality plan. Note that the BMP hydrology
calculations in Appendix 3, Table 6, included a 20 percent reduction in impervious area due to
anticipated landscaping.
REPORT/13251CWQP.DOC
Currently, Order 2001-01 states that only a portion of the storm drain design flow, i.e. .2
inches/hr (first flush)), may be used in the design of flow-based BMPs. However, it may be
possible to treat the entire storm flow within the biofilter if sheet flow (minimal depth) and low
velocities are maintained, so as not to suspend the first flush pollutants. This type pf BMP design
would have to be approved by the City and RWQCB.
Retention Basins (Wetland Ponds)
Wetland Pond/retention basin volumes were determined for both individual and combined PAs
using the volume-based BMP design criteria. The results of this "concept" analysis also show
that the basins, if used as the sole BMP for the project, would require a significant amount of
area to effectively treat the storm water. PA design options to reduce basin volumes, i.e. surface
area, are similar to those identified above under the discussion on biofilters above.
Appendix 4, Table 7, and Appendix 5, Table 8, show the "concept" treatment volumes that
would be required if each PA constmcted its own basin, or if a single joint-use basin were
constmcted to treat storm water runoff from more than one PA. In addition. Tables 3 and 4 also
include a matrix that shows the surface dimensions of the basin for a number of basin depths.
7.0 PROJECT INDUSTRIAL BMP PLAN IMPLEMENTATION
This section identifies several "concepts" BMP plan options for the Bressi Ranch industrial PAs
that should meet the applicable stormwater and water quality ordinance requirements for
industrial sites. This includes incorporating BMPs that minimize runoff contamination and storm
water runoff from the site. These plans were developed per the proposed and PA layout shown
on Exhibit A.
BMPs other than those identified herein, may be selected during final engineering. Note that the
City has yet to implement its policy for compliance with the Order 2001-01, or develop specific
BMP Standard Drawings. This may ultimately affect the selection of industrial BMP treatment
REPORT/I325ICWQP.DOC
controls for the project. Therefore, the following BMP plan is "conceptual" and subject to
change pending City review and implementation of future policy requirements.
Per City of Carlsbad comments on the previously sumbitted version of this report dated July
2001, it should be noted that:
Each Planning Area is responsible for on-site control of pollutants. Basins, landscaped
filters, or improved BMPs shall be located onsite of each planning area and should be
maintained by the respective owner.
The following assumptions were used in the development of the BMP Plan for this project:
• Only onsite flows will be treated. All offsite flow treatment will be the responsibility of
the upstream owners.
• Runoff coefficients, 'C values, of 0.95 were used in the mnoff calculations for industrial
areas.
CDS units will be accepted for use in the City of Carlsbad.
• The following sections address the use of industrial/municipal BMPs only. During
constmction, BMPs such as desilting basins and other erosion control measures will be
employed, consistent with the Constmction NPDES permit Storm water program.
7.1 Project BMP Source Control Options
Source controls BMPs are operational practices that prevent pollution by reducing the pollutants
at the source by not allowing the pollutants to enter the storm water or non-storm water runoff.
Treatment control BMPs are typically stmctural methods for removing pollutants from the
mnoff While, source control BMPs are typically less expensive to install and maintain than
treatment control BMPs, they may not be sufficient to effectively reduce pollutants in the mnoff.
Typically for large project sites such as Bressi Ranch source control BMPs are used in
conjunction with treatment control BMPs to provide effective BMP storm water treatment.
Source control BMPs considered for use in the industrial areas includes, but are not limited to:
Standard good-housekeeping principles;
REPORT/1325ICWQP.DOC j
Standard good-housekeeping principles;
Storm drain system inlet stenciling;
Employee training;
Spill containment methods;
Properly designed covered materials and trash storage areas;
Properly designed vehicle and equipment loading, fueling, maintenance, and washing areas
to prevent mnoff contamination or non-storm mnoff;
Minimize directly connected impervious areas where applicable; and
Erosion protection.
See Appendix 7 for additional treatment control BMPs, per the Industrial Califomia Storm Water
BMP Handbook.
7.2 Project BMP Treatment Control Options
The BMP Plan Options below address the use of treatment control methods using flow based and
volume based BMPs. The following BMPs address general non-point source site mnoff issues
and do not address industry specific point source discharges, which are covered under separate
state and regional regulations.
Option 1: Grass Biofilters and Strips
This option includes the use of onsite grass-lined swales (biofilters) to provide runoff treatment.
Table 6 in Appendix 3 provides the treatment discharge and the minimum treatment surface area
for each individual PA. The treatment areas are based on an assumed impervious area of 80
percent for each PA and minimum design criteria of 1000 sq-ft. of vegetative treatment area per
acre of impervious acre (see Municipal Manual). Review of the project layout shows that a grass-
lined swale may be placed in the 50-foot buffer zone along Palomar Airport Road. This would
require either grading and/or a storm drain system that conveys the runoff to the buffer zone.
REPORT/1325ICWQP.DOC 12
Option 2: Wetland Pond/Retention Basins
Retention basins are a volume based BMP that may be employed to treat the site runoff Tables
7 and 8 in Appendices 4 and 5, respectively, provide treatment volumes for each individual PA
and various scenarios of combined PAs. In addition, the tables provide preliminary basin depths,
widths, and lengths.
The basin volumes presented in this report are intended as a preliminary design aid that can be
used to determine the location of the basin(s) during final engineering. Retention basins could be
provided for each individual planning area or combinations of areas. For example, a joint use
basin could be constmcted at the southeast comer of Palomar Airport Road and El Camino Real
to provide treatment for PAs 3 through 5.
The use of retention basins assumes that proper infiltration can be achieved within 40-to 72-
hours, which promotes storm water treatment efficiency and controls vectors such as mosquitoes
and rodents. Based on information from the geotechnical/soils engineer, the soil within the
industrial planning areas is predominately Tertiary Torrey Sandstone, which has a generally
medium infiltration capacity.
Note that further evaluation of Options 1 and 2 is required during final engineering due to
uncertainty associated with the final site plan and type of industry. The use of these BMP options
are also dependent on: 1) the ability to direct first-flush flows to the BMPs, 2) the space required
by the BMP, 3) soil infiltration rates, and 4) the co-mingling of treated versus untreated flows.
Option 3; CDS Units
An altemative to swales and retention basins, in-line flow based BMPs such as CDS Pollutant
Trap Treatment Units (Units) may be installed at strategic locations prior to discharging the
onsite mnoff to the storm drain system (see Appendix 8 for more information on these devices).
REPORT/1325ICWQP.DOC 13
The CDS Units may be located 1) within in each planning area or subarea prior to discharging to
the publicly maintained storm drain system, 2) at central locations designed to treat a
combination of industrial area flows, or 3) at central locations designed to treat a combination of
industrial, residential, and mixed-use area flows.
Note that Fossil Filter Inlet Inserts were provided as an option in the July 2001 version of this
report. Based on City comments, the Fossil Filter Inlet Inserts have been removed as a BMP
option. The City does not consider Inlet Inserts as a favored BMP for tentative map stage design
and planning.
Option 4; Combination of BMP Options 1 through 3
Due to the uncertainty associated with the industry user and final site layout for each PA,
flexibility is required in the selection of the BMPs. As a result, combination of the above BMP
options may be needed to provide the most efficient and cost-effective BMP water quality plan.
In addition, during final engineering other treatment control BMPs may compliment the options
presented herein. In effect, this documents lays the groundwork for the development of future
industrial SWPPPs, or water quality plans, by each PA industrial user.
Some of these options include the possibility of combining BMPs for several Planning Areas.
The combination of Planning Area BMPs will require futher study in light of the City's request
that each Planning Area be individually responsible for on-site pollutant control. In some
specifically approved cases, BMPs for different Planning Areas could possibly be combined.
8.0 CONCLUSION
This report provides a "concept" water quality plan for the industrial land use component of the
Bressi Ranch environmental document. This "concept" water quality report provides BMP
options, or schemes, for the Bressi Ranch industrial PAs that should satisfy the requirements
identified in the following documents: 1) Carlsbad Municipal Code Stormwater Management
REPORT/1325ICWQP.DOC 14
and Discharge Control Ordinance, 2) Standard Specifications for Public Works Construction,
and 3) State NPDES Orders 97-03-DWQ, and 2001 -01.
In general, this report includes the following:
An overview of the industrial and municipal permit process;
Existing and proposed land use condition pollutant load analysis;
"Concept" Best Management Practices (BMP) volume- and flow-based) design
hydrology;
"Concept" geometric requirements for retention and grass-lined BMPs, per the design
hydrology;
Selection of additional source and treatment control industrial BMPs that may be
evaluated for use by the industrial users during final engineering;
"Concept" project BMP water quality plan options for this project; and
Manufactures information for proprietary industrial BMP devices.
It is important to note that during final engineering other treatment control BMPs may be
included in the BMP plan options presented herein. In effect, this documents lays the
groundwork for the development of future industrial water quality plans by each PA.
Each Planning Area is responsible for on-site control of pollutants. Basins, landscaped
filters, or improved BMPs shall be located onsite of each planning area and should be
maintained by the respective owner.
REPORT/1325ICWQP.DOC
APPENDIX 1
PA POLLUTANT LOADS
AND
SUPPORT DOCUMENTATION
REPORT/1325ICWQP.IX)C
TABLE 2
BRESSI RANCH
PLANNING AREA EXISTING CONDITION OPEN SPACE
AND
DEVELOPED CONDITION INDUSTRIAL POLLUTANT LOADS
AVERAGE ANNUAL SURFACE RUNOFF (R)
Cp Ci IMP 1
(in.)
R(l)
in/yr
0.15 0.9 0.8 10 7.5
LOADING FACTOR FOR INDUSTRIAL LAND USE (M,)
PA EMC Rl K Area Ml
(mg/1) (in/yr) (conv. factor) ib/yr
1 264.5 7.5 0.2266 2.3 1034
2 264.5 7.5 0.2266 22 9889
3a 264.5 7.5 0.2266 25.5 11463
3b 264.5 7.5 0.2266 21 9440
4 264.5 7.5 0.2266 39 17531
5 264.5 7.5 0.2266 31 13935
Total 140.8 63292
AVERAGE ANNUAL SURFACE RUNOFF (R)
Cp Ci IMP 1
(in.)
R(l)
in/yr
0.15 0.9 0.005 10 1.54
LOADING FACTOR FOR EXISTING LAND USE (M,)
Drainage
Basin
EMC
(mq/l)
Rl
(in/yr)
K
(conv. factor)
Area
(acres)
Ml
Ib/yr
1 377.4 1.54 0.2266 140.8 18543
Step 4 - Select BMPs
The most cost-effective BMP scenario is selected using Worksheet 2 in Chapter 3. The first
step in setting up Worksheet 2 is to detennine the average annual pollutant loading from the
site prior to development (i.e, pasture with no BMPs), the aimual pollutant load increase due to
the development, and the average annual pollutant loading under each of the three BMP
scenarios identified in Step 3. The purpose is to compare projected non-point source pollutant
loads before and after development in order to identify the load reductions that could be
achieved by placing different BMP options. The NURP data and/or other local studies could
be used for pollutant load estimates, mnoff estimates, or removal efficiencies.
For this example, pollutant loads were simulated using the Camp Dresser & McKee Inc.
(CDM) Watershed Management Model (WMM). WMM is a spreadsheet-based tool for annual
and/or seasonal load evaluations based on the methodology outlined in the Guidance Manual
for the Preparation of Part 1 of the NPDES Permit Application for Discharges from Municipal
Separate Storm Sewer Svstems. EPA, 1991. EMCs and impervious values for WMM are
shovra in Table 2. These are based upon NURP data and CDM experience. For WMM,
annual runoff volumes for the pervious/impervious areas in each land use category are
calculated by multiplying the average annual rainfall volume by a runoff coefficient. A runoff
coefficient of 0.9 is typically used for impervious areas (i.e., 90 percent of the rainfall is
assumed to be converted to mnoff from the impervious fiiction of each land use). A pervious
area mnoff coefficient of 0.15 is typically used. The total average annual surface mnoff from
a given land use L is calculated by weighting the impervious and pervious area mnoff factors
for each land use category as follows:
Ri.= [ Cf-i- (C,- Cf) IMPl, ] *I Equation 1
Where: = total average annual surface ranoff firom land use L (in/yr)
IMPL = fractional imperviousness of land use L from Table 2
I = long-term average annual precipitation (in/yr)
Cp = pervious area runoff coefficient = 0.15
Ci = impervious area runoff coefficient = 0.90.
The WMM generates nonpoint source pollution loads (expressed as Ibs/yr) that vary by land
use and the percent imperviousness assodated with each land use. The pollution loading
factor Ml is computed for land use L by the following equation:
ML = EMCL *RL*K*AL Equation 2
Where: M^ = loading factor for land use L Gb/yr)
EMCL = event mean concentration of ninoff firom land use L (mg/L);
EMCL varies by land use and by pollutant
RL = total average annual surface runoff from land use L computed from
Equation 1 (in/yr)
K = 02266, a unit conversion constant
AL = area of land use L (acres).
The loads are then summed for a given area or scenario to produce summary results without
BMPs. BMP efficiencies are then applied as fractional removal coefficients to reduce annual
loads.
Municipal Handbook B - 4 March, 1993
t
I Event Mean Concentrations And Impervious Percentages
Assigned For The Watershed Management Model
Land Use I^erccnt
Impervious
Oxygen DemantI & Sediment Nutrients Heavy Metals
Land Use I^erccnt
Impervious
BOD
mg/L
COD
mg/L
TSS
ing/L
tt)S
mg/L
TP
mg/L
SP
mg/L
TKN
mg/L
N023
mg/L
Pb
mg/L
Cu
mg/L
Zn
mg/L
Cd
mg/L
Forest/Open 0.5% 8.0 51 216 100 0.23 0.06 1.36 0.73 0.00 0.00 0.00 0.00
Agriculture/Pasture 0.5% to 51 216 100 0.23 0.06 1.36 0.73 0.00 0.00 0.00 0.00
Cropland 0.5% 6.0 51 216 100 0.23 0.06 1.36 0.73 0.00 0.00 0.00 0.00
Low Density Residential 10.0% 10.8 8i 140 100 0.47 0.16 2.35 0.96 0.18 0.05 0.18 0.002
Medium Density
Residential 30.0% 10.8 83 140 100 0.47 0.16 2.35 0.96 0.18 0.05 0.18 0.002
High Density Residential 50.0% 10.8 83 140 100 0.47 0.16 2.35 0.96 0.18 0.05 0.18 0.002
Commeix:ial 90.0% ^.1 61 01 100 0.24 0.10 1.28 0.63 0.13 0.04 0.33 0.002
(>ffice/Llght Industrial 70.0% 0.7 61 01 100 0.24 0.10 1.28 0.63 0.13 0.04 0.33 0.002
Heavy Industrial 80.0% ^.1 61 01 100 0.i4 0.10 1.28 0.63 0.13 0.04 0.33 0.002
Water 10 22 i6 100 0.03 O.Ol 0.60 0.60 0.00 0.00 0.11 0.000
Wetlands 0.^9i 8.0 51 ii6 100 0.23 0.06 1.36 0.73 0.00 0.00 0.00 0.00
Major Highway 90.0% 9.7 103 14i 100 0.44 0.17 1.78 0.83 0.53 0.05 0.37 0.002 1
I
in
I
Source: EPA, 1983 and CDM experience
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Conlrol (Source)
Biofilters - Syslems designed to pass
storm water runoff slowly over a
vegetated surface in the fbrm ofa swale
or strip to filler pollulanis and lo infillrute
Ihe runoff. (19)
Limilalions Benefits Removal Efficiency Capital Cost
(approximate)
O&M Cosl
(approximale)
Bioretention - sysiem designed lo treal
runoff. The runoff is conveyed as sheet
tlow 10 the treatment area, which consists
ofa grass buffer slrip, sand bed, ponding
area, organic layer or mulch layer,
planling soil, and plants. (33)
*cold climate may hinder
infiltrative capacity. (33)
*not suitable for slopes
greater than 20 percenl. (33)
*clogging may occur in high
sedimenl load areas. (33)
•enhance qualily of
downslream water bodies.
(33)
•improves area's
landscaping. (33)
•provide shade and wind
breaks. (33)
* total Phosphorus 70 lo
83%.. (33)
* metals (copper, lead,
zinc) 93 10 98%. (33)
* TKN 68%' 10 80%. (33)
* lolal suspended solids
90%'. (33)
* organics 90%. (33)
* bacleria 90%. (33)
$500 for new
development ofa
biorelenlion,
.$6,500 for
retrofitting a site
into a bioretetion
area (33)
Vegetated Swale - is a broad, shallow
channel (typically trapezoidal shaped)
wilh a dense stand of vegetation covering
the side slopes and boltom. (29)
Useful life is around 50 years. (20)
^generally incapable of
removing nutrients. (2)
*can become drowning
hazards, mosquito breeding
areas. (29)
>not appropriale for sleep
topography, very flat grades.
(29)
.hIribuiary area limiled lo a
maximum of 5 acres. (19)
difficult U) avoid
channelization. (19)
*ineffeclive in large slorms
due lo high velocily flows.
(29)
Jl design to convey runoff
of 2 year slorm, with
freeboard of 10 year slorm.
(19)
• low land requirement.
(20)
/isuilable for small
residential areas. (1)
>can removes paniculate
pollutants at rates similar lo
wel ponds. (1)
•reduction of peak flows.
(29)
•lower capilal cost. (29)
•promotion of runoff
infiltration. (29)
• low land requirements.
(20)
• nilrogen 0 to 60%' (2)
• total nitrogen 10%. (20)
• phosphorus 0 to 60% (2)
• total phosphorus 9%' (29)
& 20%. (20).
• COD 25%'. (20)
• oxygen demanding
substances 67%. (29)
• lotal suspended solids
81%. (29) & 60%. (20).
• nilrate 38%. (29)
• hydrocarbons 62%. (29)
• cadmium 42%-. (29)
• lead 67% (29) & 70%.
(20).
• zinc 71% (29) & 60%
(20).
• copper 51%'. (29)
• $6.80 to $12.50
per linear foot
(prorated using
ENR index from
1987 cosO- (29)
• $10.80 to $63.40
per linear foot
(prorated using
ENR index from
1991 cost). (29)
• typical tolal for
a 1.5 fl. deep. 10 ft
wide, 1,000 li long
Low-$8,100
Moderate -
$14,870
High-$21,640
Prorated using
ENR index from
1991 cosO-
(29)
• $0.73 - $0.95
per linear foot
(prorated using
ENR index from
1991 cosO. (29)
• $1/1 inear fool
9prorated using
ENR index from
1987 cosl). (20)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Conlrol (Source) Limitations Benefits Removal Efficiency Capital Cosl
(approximale)
O&M Cost
(approximate)
Infiltration (Vegetative Filter) Strip - are
broad surfaces wilh a full grass cover lhat
allows storm water lo flow in a relatively
thin sheets (21)
Useful life is around 50 years (20).
•sheet flow may be difficult
10 attain. (1)
•nol appropriale for steep
slopes. (19)
•tributary area limited to 5
acres. (19)
•suitable for parking lots.
(1)
•slows runoff tlow. (1)
•removes particulate
pollutants. (1)
• nilrogen Olo 40%'. (2)
• phosphorus 0 lo 40%. (2)
• lotal suspended solids
65%. (20)
• total phosphorous 40%.
(20)
• total nitrogen 40%. (20)
• COD 40%. (20)
• lead 45%. (20)
• zinc 60%.. (20)
• $3,100/acre
(prorated using
ENR index from
1992 cost).
(5)
• $310/acie/yr
(prorated using
ENR index from
1992 cost). (5)
• $139 to
$l,100/ac re/year
(prorated using
ENR index from
1987 cost). (20)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Conlrol (Source) Limilations Benefits Removal Efficiency Capital Cost
(approximate)
O&M Cosl
(approximale)
Extended Detention Basins - consist ofa
settling basin with an oullel sized lo
remove particulate matter by slowly
releasing accumulated runoff over a 24 lo
40 hour period. "Dry" detention basins
may be designed to empty between
usages. (19)
Useful life is usually 50 years. (20)
•occasional nuisance in
inundated poriion. (19)
•inability lo vegetation may
result in erosion and re-
suspension. (1)
•limited orifice diameter
preclude use in small
watersheds. (1)
•requiies differential in
elevation al inlel and outlet.
(1)
•frequent sediment
maintenance. (19)
• High land requirement.
(20)
•creation of local wildlife
habitat. (2)
•recreational use in
inundated portion. (2)
•can remove soluble
nutrients by shallow marsh
or permanenl pool. (2)
•suitable for sites over 10
acres. (10)
•lemporary storage of
runoff. (1)
•no need of supplemental
waler. (1)
•protection for downstream
channel erosion. (2)
• nilrogen 20% lo 60'7f..
(2)
• phosphorus 20%. lo 80%
(2) & 10% 10 30%. (10)
• nitrogen and phosphorus
30%. to 70%. (depending on
volume ralio). (8)
• soluble nulrienls - low or
negative. (10)
• lolal suspended solids
45% (20) & 88% (44).
• nilrale 15% (44).
• nitrite 61% (44).
• oil and grease 56%.. (44)
• fecal coliform 45%.. (44)
tolal petroleum
hydrocarbons 17% lo 20%..
(44)
• TKN 40%. (44)
• ammonia 5%.. (440
•tolal phosphorous 25%
(20) & 57% (44).
• tolal nitrogen 30%. (20)
•COD 20%. (20) & (44).
• lead 20%. (20) & 55%
(44).
• zinc 20% (20) & 47%
(44).
• chromium 68%. (44)
• copper 37%.. (44)
• nickel 62%. (44)
$123,000/million
gallons
(prorated using
ENR index from
1992 cosl).
(5)
• $l,230/million
gallons/year
(proraled using
ENR index from
1992 cosl).
(5)
* 4%. of capilal
cost. (20)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Conlrol (Source) Limitations Benefits Removal Efficiency Capilal Cosl
(approximale)
O&M Cost
(approximale)
Modular Trealment Systems
StormTreal™ System (STS) - treatment
technology consisting of a series of
sedimentation chambers and constructed
wetlands. The 9.5 feet diameter recycled
polyethylene modular treals slorm water
wilh sedimentation chambers, where
pollutants are removed through
sedimentation and fillration, then the
waler is conveyed lo a surrounding
constructed wetland. Vegetation in the
wetland varies depending on local
conditions. Because the system is
relatively new, there is no data available
on lifetime of the system. It is eslimaied
that the plants and the gravel in the
system need to be replaced every 10-20
years. (32)
•may require modifications
to function in different
environments. (32)
* relatively new and remains
to be tested in different
geographical localions.
•proiect groundwater by
removing pollutants prior
lo infiltration. (32)
•high removal rales. (32)
•spill containment feature.
(32)
•soil types and high water
table won't limil
effectiveness. (32)
• fecal coliform bacteria
97%'. (32)
• total suspended solids
99% (32)
• COD 82%. (32)
• lotal dissolved nitrogen
77%.. (32)
• phosphorus 90%.. (32)
• tolal petroleum
hydrocarbons 90%. (32)
• lead 77%. (32)
• chromium 98%. (32)
• zinc 90%. (32)
$4,900 per unit -i-
$500 to $ 1,000
inslallalion cost -i-
$350 to $400 for
additionai malerial
(32)
$80 10$ 120 per
lank for removal
of sediment (32)
Hydrodynamic Separators - are tlow-
ihrough structures with a settling or
.separation unit lo remove sediments and
other pollutants that are widely used.
With proper upkeep, useful life is over 30
years. (2^)
Downstream Defender™ - designed to
capture setlleable solids, floatables and oil
and grease. It utilizes a sloping base, a dip
plale and internal components lo aid in
pollutant removal. (25)
• requires frequent
inspections and maintenance
is site-specific. (25)
Can achieve 90%. particle
removal for flows from
0.75 cfs to 13 cfs (25)
$10,000 to
$35,000 per pre
cast unit (23)
Continuous Deflection Separator (CDS) -
pre cast units placed downstream of
freeway drain inlets to capture sedimenl
and debris. These underground unils
create a vortex of waler lhal allows waler
to escape through the screen, while
contaminants are deflected into the sump.
(21)
• suitable for gross pollutant
removal. (21)
Jl intended lo screen litter,
fine sand and larger
particles. (21)
Jiact as a first screen
influence for trash and
debris, vegetative material
oil and grease, heavy
melals. (21)
oil and grease - 77% (34) $2,300 to $7,200
per cubic feet
second capacity
(23)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Trealment Control (Souice) Limitations Benefils Removal Efficiency Capilal Cost
(approximate)
O&M Cost
(approximale)
Continuous Deflection Separator (CDS)
with Sorbents. Applicalion of different
types of sorbenis in the CDS units.
OARS^^* - is a rubber type off sorbent
(34)
Rubberizer - is composed of a
mixture of hydrocarbon polymers
and additives. (34)
Aluminum Silicate:
Xsorb™ is made from a natural
blend of silica minerals, which
when expanded in our unique
manufacturing process, make a
white granular malerial lhal
absorbs spills instantly on
conlact (web)
Sponge Rok™ - primarily sold as
a soil bulking agent (34)
Nanofiber™ - is a polypropylene
adsorbent. (34)
• requires frequenl
inspections and maintenance
is site-specific. (25)
•sorbents remove many
limes Iheir own weight (34)
•could be used oil spill
conlrol. (34)
OARS:
oil and grease - 82%, 83%,
86%, 94% (34)
Rubberizer:
oil and grease 86%. (34)
Xsorb:
oil and grease 79%. (34)
Sponge Rok:
oil and grease 41%. (34)
Nanofiber:
oil and grease 87%.. (34)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Control (Source)
Stormceptor® - This system is a
stormwater interceptor that efficiently
removes sediment and oil from
stormwater runoff and stores these
pollutants for safe and easy removal.
Units are available in prefabricated sizes
up to 12 feet in diameter by 6 to 8 feet
deep. They re designed to trap and retain
a variety of non-point source pollulanis,
using a by-pass chamber and trealment
chamber. A fiberglass insert separates the
upper (by-pass) and lower
(separation/holding) chambers. (25)
Limitations
• requires frequenl
inspections and maintenance
is site-specific. (25)
Benefils
•use for redevelopment
projecis of more lhan 2,500
sq. feet where there was no
pervious slorm water
management. (25)
•projecis lhat double the
impervious layer. (25)
•easy to design in new or
retrofit applications. (35)
•inexpensive to service and
maintain. (35)
•inlernal bypass prevents
release of trapped
pollutants. (35)
•Ideal for highways,
industrial properlies, gus
stations, parking lots and
sites where there is a
potential for oil or chemical
spills.
Removal Efficiency
• tolal suspended solids
80%. (35)
• free oils 95%.. (35)
•oil 98.5%. (36)
• inorganic sediment 80%..
(36)
• organic sediment 70%.
(36)
• tolal suspended solids
51.5%.. (36)
• oil and grease 43.2%..
(36)
•zinc 39.1%. (36)
• total organic carbon
31.4%. (36)
• chemical oxygen demand
26.0%.. (36)
• lead 51.2%. (36)
• chromium 40.7%.. (36)
•copper21.5%. (36)
• iron 52.7%. (36)
• calcium 17.9%. (36)
Capilal Cost
(approximale)
$7,600 to $33,560
per unit (23)
O&M Cost
(approximate)
$ 1,000/year per
slructure (23)
Vortechs™ - a major advancement in oil
and grit separalor technology, Vortechs
unils removes grit, contaminated
sediments, heavy metals, and oily floating
pollulanis from surface runoff, ll is a
stormwater treatment system consisting of
four structures to treat stormwater: a
baffle wall, a grit chamber, an oil
chamber and a flow control chamber.
This system combines swirl-concentralor
and flow-control technologies. (25)
•most effective when
separation of heavy
particulate or lloalable from
wel weather runoff. (25)
•suspended solids are not
effectively removed. (25)
• requires frequent
inspections and maintenance
is site-specific. (25)
•suited for areas with
limiled land available (25)
•good for "hotspots" such
as gas stations (high
concentrations). (25)
•able lo treat runoff flows
from 1.6 cfs to 25 cfs. (25)
• total suspended solids
84%. (37)
$10,000 to
$40,000 per unit
(nol including
inslallalion) (23)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Control (Source) Limitations Benefils Removal Efficiency Capital Cost
(approximale)
O&M Cosl
(approximale)
Multi-Cliainbered Treatinent Trains
(MCTT) - consist of a three treatment
mechanisms in three different chambers.
1) catch basin - screening process to
remove large, grit sized material, 2)
settling chamber - removing settleable
solids and associaied constituents with
plate separators and sorbent pads, 3)
media filter - uses a combinaiion of
sorption (layers of sand and peat covered
by filter fabric) and ion exchange for the
removal of .soluble constituents, (21)
•high maintenance - require
renewing sorbent pads,
removing sediment,
replacing clogged media.
(21)
•treats storm water at
critical source areas with
limiled space. (21)
• loxicily 70% lo 100%.
(24)
• chemical oxygen demand
0%. to 100%. (24)
• total suspended solids
70% to 90% (24)
• approx.
$375,000 to
$900,000
(depending on
drainage area)
Media Filtration - these are usually two
or three stage constructed treatment
systems, composed of a pretreatment
settling basin and a filter bed containing
filter media (and a discharge chamber).
(19)
Sand Filter - the filter is designed to hold
and treat the first one half inch of runoff
and the pollutant removal ability of Ihe
sand filter has been found to be very
good. (3)
•not effective treating liquid
or dissolved pollutants (19)
Jiioutine maintenance
requirement. (19)
Jisignificani headloss. (19)
Jl severe clogging potential.
(19)
•media may be replaced 3 lo
5 years. (30)
•climate condilions may
limit filter's performance.
(.30)
Jihigh removal rates for
sedimenl, BOD, and fecal
coliform bacteria. (30)
•can reduce groundwater
contamination. (30)
Jl requires less land, can be
placed underground. (19)
Jisuilable for individual
developmenls. (1)
Jiminimum depth of 18
inches. (1)
Jl Iribuiary areas of up lo
100 acres. (19)
• fecal coliform 76%. (30)
• BOD 70 %. (30)
• total suspended solids
70 %. (30)
• lotal organic carbon 48%.
(30)
• tolal nilrogen 219!.. (30)
• lolal phosphorus 33'/('.
(30)
• Lead 45%.. (30)
• zinc 45%.. (30)
• iron 45%. (30)
•$18,500(1 acre
drainage area)
(1997). (30)
• $6,940 to
$11,600 (less lhan
1 acre - casl in
place) (proraled
from 1997 prices
using ENR index).
(30)
• sand filler vault
$ 1,790 (proraled
from 1997 prices
using ENR index).
(18)
• sand filter basin
$3,370 (proraled
from 1997 prices
using ENR index).
(18)
• 5 percenl of the
initial construciion
cosl. (30)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Control (Source) Limitations Benefits Removal Efficiency Capital Cost
(approximate)
O&M Cost
(approximate)
Activated Carbon - has long been used in
the chemical process industry and in
hazardous waste cleanup as an effective
method for removing trace organics from
a liquid. (3)
•heavy maintenance
requirement. (19)
•severe clogging potential.
(19)
•limiled by the number of
adsorption sites in Ihe
media. (3)
•small nel surface charge
and ineffective at removing
free hydrated metal ions. (3)
•can be placed
underground. (19)
•less space required. (1)
•effective in removing
Irace organics from liquid.
(3)
•suitable for individual
developmenls. (1)
• $l/lbor$315/cy
(prorated from
1997 prices using
ENR index).
(18)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Conlrol (Source) Limilalions Benefils Removal EITiciency Capilal Cosl O&M Cosl
(approximate) (approximale)
Composted Leaves - made from yard •heavy maintenance •can be placed * lolal suspended solids • $ 130/cy • $2,400/year
wasle, primarily leaves, have been requirement. (19) underground. (19) 84%. (3),-155% to 72%. (prorated from (proraled from
advertised to have a very high capaciiy •severe clogging potential. •no vegetation required. (22). 1997 prices using 1998 prices using
for adsorbing heavy metals, oils, greases. (19) (19) • petroleum hydrocarbons ENR index). ENR index). (22)
nutrients and organic toxins due to the •in some cases, negative •smaller land area required. 87% (3), 4%. lo64%. (22). (18)
humic conient of the compost. (3) removal efficiencies with (3) • chemical oxygen demand • $27,000 to treal humic conient of the compost. (3)
increased loads have been •suitable for individual 67% (3), 32% to 38%. (22). 1 cfs (prorated
reported. (22) developments. (1) • tolal Phosphorus 40% (3) from 1998 prices reported. (22)
& -320% to 28% (22). using ENR index).
•TKN-133%. to 43%. (22) (22)
• fecal coliform 6%. to
80%. (22)
• oil and grease 0% to
44%. (22)
• lotal petroleum
hydrocarbons 33% to 64%.
(22)
• ammonia 41% to 64%.
(22)
• nitrate-172%to7%. (22)
* nitrite -233%. lo 29%..
(22)
• chromium 0% to 25%.
(22)
• copper 67% (3) & 4%. lo
9% (22).
• zinc 88%. (3) & 46% to
65% (22).
• aluminum 87%. (3)
• nickel 33'X. to 50%. (22)
• lead 0% to 17%. (22)
Nationwide Examples of Treatment Control (Structural) Best Managenient Practices (BMPs)
Treatment Control (Source) Limitations Benefits Removal Efficiency Capital Cosl
(approximale)
O&M Cosl
(approximale)
Peal Moss - is partially decomposed
organic material, excluding coal, that is
formed from dead plant remains in waler
in the absence of air. The physical
structure and chemical composiiion of
peal is determined by the types of plants
from which il is formed. Peat is
physically and chemically complex and is
highly organic. (3)
•heavy maintenance
requirement. (19)
•severe clogging potential.
(19)
•can have a high hydraulic
conductivity. (3)
•can be placed
underground. (19)
•no vegetation required.
(19)
•smaller land area required.
(3)
•polar and has a high
specific adsorption for
dissolved solids. (3)
•excellent natural capaciiy
for ion exchange. (3)
•excellent substrate for
microbial growth and
assimilation of nutrients
and organic wasle malerial.
(3)
$25 to$105/cy
(prorated from
1997 prices using
ENR Index). (18)
Peat-Sand Filter - man made filtration
device, has good grass cover on the top
underlain by twelve to eighteen inches of
peal. The peal layer is supported by a 4
inch layer of peat and sand mixture which
supported by a 20 to 24 inch layer of fine
to medium sand. Under Ihe sand is gravel
and the drainage pipe. (3)
•heavy maintenance
requirement. (19)
•severe clogging potential.
(19)
•can be placed
underground. (19)
•less space required (1)
•suitable for individual
developments. (1)
•works best during
growing season as grass
cover can provide
additional nutrient removal
(3)
• suspended Solids 90%
(3) & 80%. (20).
• lotal phosphorus 70% (3)
& 50% (22).
• tolal nitrogen 50% (3) &
35% (20).
• BOD 90%.. (3)
• bacteria 90%. (3)
• trace metals 80%.. (3)
• lead 60%. (20)
• zinc 65%.. (20)
• COD 55%.. (20)
$6.50 per cubic
foot of material
(prorated from
1990 prices using
ENR index). (20)
7 % of
consiruction cosl.
(20)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatinent Conlrol (Source) Limilations Benefits Removal Efficiency Capilal Cost
(approximate)
O&M Cosl
(approximate)
Waler Quality Inlets - commonly known
as oil/gril or oil/waler separators. These
devices typically consist ofa series of
chambers, a sedimentation chamber, an
oil separation chamber and a discharge
chamber. (31)
U.seful life is usually 50 years. (20)
•limited drainage area (1
acre or less). (31)
•high sedimenl loads can
inlerfere abilily to separate
oil and grease. (31)
•limiled hydraulic and
residual storage. (31)
•frequenl mainlenance. (31)
•residual may be considered
loo toxic for landfill
disposal. (31)
•recommended oil/waler
separalors be used for spill
control as their primary
application. (42)
•re-suspension of pollutants.
(36)
• small tlow capaciiy. (31)
•reduction of hydrocarbon
contamination. (31)
•effectively trap Irash,
debris, oil and grease (31)
•ideal for small, highly
impervious area. (31)
•ideal for mainlenance
stations. (36)
• low land requirement.
(20)
• sedimenis 20%. lo 40%.
(31)
• efficiency directly
proportional to discharge
rale. (31)
• lolal suspended solids
15%. to 35%. (20)
• lotal phosphorous 5%.
(20)
• total nilrogen 5% to 20%.
(20)
• COD 5%'. (20)
• lead 15%. (20)
• zinc 5%. (20)
.$5,900 10$ 18,900
for casl in place
waler qualily
inleis (proraled
from 1993 prices
using ENR Index).
(31)
Catch Basin Inlet Devices - devices that
are inserted into storm drain inlets to filter
or absorb sediment, pollutants, and oil
and grease (21)
• nol feasible for larger lhan
5 acres. (20)
• high removal efficiency
for large particles and
debris for pretreatment.
(20)
• low land requirement.
(20)
• flexibility for retrofit of
existing systems. (20)
Slream Guard Inserts - are sock-type
in.serts that allow collected waler lo filler
through the geotextile fabric. (21)
•maintenance includes
removal of sedimenl and
dcliris. (21)
•configured lo remove
sedimenl. constituents
adsorbed lo sediment, and
oil and grease. (21)
approx. $50,000 to
$100,000 per
calch basin. (21)
Fo-uil Filter Inserts - are trough-type of
inserts filled wilh granular amorphous
alumina silicate media. Removes
pollutants Ihrough .sorption. (21)
•maintenance includes
removal of .sediment and
debris. (21)
•configured to remove
sedimenl, consliliieiits
adsorbed lo sedimenl, and
oil and grease. (21)
appix)x. $50,000 to
$100,000 per
calch basin. (21)
1 C 1
OARS™ - is a rubber lype of sorbent
insert (34)
• free oil and grease 88%
10 91%. (.39)
• emulsified oil and grease
3%. (39)
Nanofiber™ - is a polypropylene
adsorbent type of insert. (34)
• free oil and grease 86%,
92%, 78%, 85%. (39)
Nationwide Examples of Treatment Control (Struclural) Best Management Practices (BMPs)
Treatment Conlrol (Source) Limitations Benefits Removal Efficiency Capital Cosl
(approximale)
O&M Cosl
(approximale)
Aluminum Silicate:
X.wrb™ is made from a natural
blend of silica minerals, which
when expanded in the unique
manufacturing process, makes a
white granular material thai
absorbs spills instantly on
contact.
Sponge Rok™ - primarily sold as
a soil bulking agent (34)
• free oil and grease 88%,
91%, 94%, 89%. (39)
• emulsified oil and grease
0%.. (39)
Curb Inlet Drain Diaper Insert - sorbent
type diaper placed al the calch basin
insert (40)
$125 per unit. (40)
Storm Clenz Filter and Multi Cell Flow
Through Filter - developed by Best
Management Technologies, the filters are
used typically in mainlenance facilities
and staging areas were sediment and
hydrocarbons are present. (41)
• multi cell flow
through fillers -
$786 to $1233
depending on pipe
size (6" to 12")
• storm clenz
filters - $339 to
$702 depending
on filler insert
size. (41)
• flow through
filler absorbents
$24 to $44
depending on size.
• slorm clenz
absorbents $24 to
$ 54 depending on
size. (41)
Some Examples ofTemporary Erosion and Sediment Control BMPs
activity)
(typically used during constiuction
Temporary Seeding of Stripped A reas -
The establishment of a temporary
vegetative cover on disturbed areas by
seeding with rapidly growing plants. This
provides temporary soil stabilization to
areas which would remain bare for more
than seven days where permanent cover is
nol necessary or appropriate. (42)
•Temporary seeding is only
viable when there is a
sufficient window in lime
for plants to grow and
establish cover. During the
establishment period the
bare soil should be protected
with mulch and/or plaslic
covering. (42)
•If sown on subsoil, growth
may be poor unless heavily
fertilized and limed
Because over-fertilization
can cause pollution of
stormwater runoff, other
practices such as mulching
alone may be more
appropriate. The potential
for over-fertilization is an
even worse problem in or
near aquatic systems. (42)
•Once seeded, areas cannot
be used for heavy traffic.
(42)
•May require regular
irrigation to flourish.
Regular irrigation is not
encouraged because of the
expense and the potential for
erosion in areas that are not
regularly inspected. The use
of low maintenance native
species should be
encouraged, and planling
should be limed to minimize
the need for irrigation. (42)
•This is a relatively
inexpensive form of
erosion conlrol but should
only be used on sites
awaiting permanenl
planting or grading. Tho.se
sites should have
permanenl measures used.
(42)
•Vegetation will nol only
prevent erosion from
occurring, but will also trap
sediment in runoff from
olher parts ofthe site. (42)
•Temporary seeding offers
fairly rapid proiection to
exposed areas. (42)
Mulching and Malting - Application of
plant residues or olher suitable materials
to the soil surface. This provides
immediaie protection to exposed soils
during Ihe period of short construciion
delays, or over winler months through the
application of planl residues, or other
suitable materials, to exposed soil areas.
Mulches also enhance plant establishment
by conserving moisture and moderating
soil temperatures. Mulch helps hold
fertilizer, seed, and lopsoil in place in ihe
presence of wind, rain, and runoff and
maintains moisture near the soil surface.
(42)
•Care must be taken to
apply mulch at the specified
ihickness, and on sleep
slopes mulch must be
supplemented with netting.
(42)
•Thick mulches can reduce
the soil temperature,
delaying seed germination.
(42)
•Mulching offers instant
proiection lo exposed areas.
(42)
•Mulches conserve
moisiure and reduce the
need fbr irrigation. (42)
•Neiiher mulching nor
matting requiie removal;
seeds can grow through
them unlike plaslic
coverings. (42)
Plastic Covering - The covering with
plastic sheeting of bare areas, which need
immediate protection from erosion. This
provides immediate temporary erosion
protection to slopes and disturbed areas
lhat cannot be covered by mulching, in
particular during the specified seeding
periods. Plastic is also used to protect
disturbed areas, which must be covered
during short periods of inactivity to meet
November 1 to March 31 cover
requirements. Because of many
disadvantages, plastic covering is Ihe least
preferred covering BMP. (42)
•There can be problems
with vandals and
maintenance. (42)
•The sheeting will result in
rapid, IOO percent runoff,
which may cause serious
erosion problems and/or
flooding at the base of
slopes unless the runoff is
properly intercepted and
safely conveyed by a
collecting drain. This is
strictly a temporary
measure, so permanent
stabilization is still required.
•The plastic may blow away
ifil is not adequately
overlapped and anchored,
(42)
•Ultraviolet light can cause
some types of plastic to
become brittle and easily
torn. (42)
•Plastic must be disposed of
at a landfill; it is nol easily
degradable in the
environment. (42)
•Plastic covering is a good
method of protecting bare
areas, which need
immediate cover and for
winler plantings. (42)
•May be relatively quickly
and easily placed. (42)
Nationwide Examples of Source Control (Non-Structural) Best Management Practices (BMPs)
Source Control (5) Benefit (5) Capital Cosl (5) O&M Cost (5)
Minimizing Effects from Highway Deicing
Public Education (billing inserts, news
releases, radio announcements, school
programs)
JiCan reduce improper disposal of painis and
chemicals.
$200,000/yr(1992) $257,000/yr(1992)
Employee Training - teaches employees aboul
slorm water management, potential sources of
contaminants, and BMPs. (43)
Jilow cost and easy to implement storm waler
management BMPs. (43)
Litter Control Jl Reduce poieniial clogging.
Jl proper disposal of paper, plastic and glass.
.$20 per trash cans (1992) $16/acre/yr(1992)
Recycling Program Jl reduction in potential clogging and harmful
discharge.
$200,000/yr $350,000 per 300,000
people
"No Littering" Ordinance Jl prevents litter from enter storm drain. $20,000 potential self
supporting
Identify and Prohibit Illegal or Illicit discharge
to Storm Drain
Jihall hazaidous and harmful discharge. $2/acre (assumes 1
sysiem monitored every
5 sq. miles)
$50/acre/yr (assumes
TV inspection)
Slreet Sweeping - Two types of street
sweepers are available for removal of solids
from highway surfaces. The commonly used
design is a mechanical slreet cleaner that
combines a rotating gutter broom with a large
cylindrical broom to carry the material onto a
conveyor belt and into a hopper.
The vacuum assisted sweepers, found to
potentially remove more fine particles from
the impervious surface, are impracticable due
to their slow speed in highway maintenance
operaiions. (42)
Jl reduction in potential clogging storm drain material.
Jisome oil and grease conlrol.
N/A $0.83/acre/yr
Sidewalk Cleaning Jl reduction of material entering storm drain. N/A $60/acie/yr
Clean and Maintain Storm Drain Channels Jl prevent erosion in channel.
Jl improve capaciiy by removing sedimentation.
Jl remove debris toxic to wildlife.
N/A $2 l/acre/yr
Clean and Maintain Slorm Inlet and Catch
Basins - Inlets, catch basins, and manholes are
to be periodically inspected and cleaned out
using a vacuum truck. (42)
J.removes sedimentation.
Jiinay pievenl local flooding.
N/A .$2 l/acre/yr
Snow and Ice Control Operations - Snow
conlrol operations consist of removing
accumulated snow from Ihe traveled
way, shoulders, widened areas and public
highway approaches wilhin the right-of-way.
(42)
Jl removes snow/ice before il requires ice control
operaiions. (42)
Clean and Inspect Debris Basin Jl flood control.
Jl proper drainage and prevent flooding.
N/A $2 l/acre/yr
Table References
1. Camp Dresser & McKee, el al. 1993. California Stonn Water Besr Management Handbook. Prepared for Storm
Water Quality Task Force. 4-8:4-77, 5-3:5-69.
2. Scheuler, Thomas R. 1987. Controlling Urban Runoff: A Practice Manual for Planning and Designing Urban
BMP's. Prepared for Washington Metropolitan Water Resources Board. 2.11:2.14, 5.1:7.25.
3. Pitt, R. et al. "The Use of Special Inlel Devices, Filter Media, and Filter Fabrics for the Treatment of Storm
Water." 9pp.
4. Eisenberg, Olivieri & Associates. 1996. Guidance for Monitoring the Effectiveness of Storm Water Treatment
Best Manageinent Practices. Prepared for the Bay Area Storm Water management Agencies Association. 5-6:5-
7.
5. JMM. 1992 A Study of Nationwide Costs to Implement Municipal Storm Water Best Manageinent Practices.
Prepared for the Water Resources Committee American Public Works Association Southern Califomia Chapter.
4-3:4-14.
6. Maine Department of Environmental Protection. Environmental management: A Guide forthe Town Officials.
16, 27.
7. Denver regional Council of Government. Nonpoint Source Demonstration Project. 7:14.
8. Environmental Protection Agency, 1990. Urban Targeting and BMP Selection. 25:31.
9. Strecker, Eric W. 1993. Assessment of Storm Drain Sources of Contaminants to Santa Monica Bay. 21:28, 32.
10. Metropolitan Washington Council of Governments. 1992. A Current Assessment of Urban Best management
practices. 7:13, 23:29,55:69, 105:109.
11. Unocal. '"More Down to Earth Talk from Unocal - Best Management Practices."
12. The Fertilizer Institute. 1985. Symposium: "Plant Nutrients Use and the Environment."
13. The Fertilizer Institute. 1988. Se5r Mfl/irt^e;?!^/?//"roc/Zcei.
14. 1994. Report of the Technical Advisory Committee for Plant Nutrient Management. 17:18.
15. Virainia State Water Control Board Planning Bulletin 321. 1979. Best Management Practices Handbook:
Urban. 111-1:111-9,111-45:111-48,111-63:111-69,111-163:111-229.
16. California Department of Transportation Environmental Program. 1997. Statewide Storm Water Management
Plan. B-14:B-53,C-I:C-22.
17. Caltrans Compost Storm Water Filters (CFSs), Bonita Canyon & North Hollywood Maintenance Yard. 1998.
Table 9-15.
18. Minion, Gary R. "Storm Water Treatment by Media Filter." Dec. 11-12, 1997.
19. Ventura Countywide Slorm Water Quality Management Program. "Draft Land Development Guidelines."
20. Environmental Protection Agency. 1993. Guidance Specifying Management Measures for Sources of Nonpoint
Pollulion in Coastal Waters.
21. Caltrans. Storm Water Program. BMP Retrofit Pilot Studies, Technical Information. 1999.
22. Caltrans. Compost Storm Water FUters (CSFs), Bonita Canyon & North Hollywood Maintenance Yard
1997/1998 Wet Season, Post Sampling Summary Report. 1998.
23. Environmental Protection Agency. 1999. Infiltration Trench. EPA 832-F-99-019.
24. Flan, Daryl R. and Himat Solanki. "Removal Efficiencies of Stormwater Control Structures."
25. Environmental Protection Agency. 1999. Hydrodynamic Separators. EPA 832-F-99-017.
26. Environmental Protection Agency. 1999. Storm Water Wetlands. EPA 832-F-99-025.
27. Environmental Protection Agency. 1999. Wet Detention Ponds. EPA 832-F-99-048.
28. Environmental Protection Agency. 1999. Infiltralion Drainfields. EP.A 832-F-99-018.
29. Environmental Protection Agency. 1999. Vegetated Swales. EPA 832-F-99-006.
30. Environmental Protection Agency. 1999. Sand Filters. EPA 832-F-99-007.
31. Environmental Protection Agency. 1999. Water Quality Inlets. EPA 832-F-99-029.
32. Environmental Protection Agency. 1999. Modular Treatment Systems. EPA 832-F-99-044.
33. Environmental Protection Agency. 1999. Bioretention. EPA 832-F-99-0I2.
34. Stenstrom, Michael K. and Sim-Lin Lau. "Oil and Grease Removal by Floating Sorbents in a CDS Device."
University of California, Los Angeles, 1998.
35. Stormceptor Performance Testing Results. http;//www.stormceptor.cona/monitor.html
Westmount Shopping Centre and Conventry University Testing Results.
36. Caltrans. Highway Design Manual. Chapter 890 - Storm Water Management. Table 892.3.1999.
37. Allen, Vaikko P. Results from the Vortechs Stormwater Treatment System Monitoring Program at Del-Orme
Publishing Company, Yarmouth, Maine. 1998.
38. Environmental Protection Agency and American Society of Civil Engineers. National Stormwater Best
Management Practices (BMP) Database. Version I.O, June 1999.
39. Lau, Sim-Lin and Michael K. Strenslrom. "Catch Basin Inserts to Reduce Pollution from Stormwater."
Comprehensive Stormwater and Aquatic Ecosystem Management Conference, Auckland, NZ, February 22-26,
1999.
40. Petro-Marine Co. Curb Inlet Drain Diaper Insert. Contact Ronald Isaacson. 28 Buckley Road, Marlboro, NJ
07746.
41. Best Management Technologies Brochure. Contact Rod Butler. 23 Balwin Ave, Crockett, CA 94525.
42. Washington State Department of Transportation. Highway Runoff Manual. February 1995.
43. Environmental Protection Agency. 1999. Employee Training. EPA 832-F-99-010.
44. Caltrans. El Toro Detention Basin Storm Water Monitoring 1997/1998 Wet Season, Post Sampling Summary
Repon. 1998-
Caltrans - Best Management Practices Pilot Studies
Removal Etl'iciency "/ '<•
BMPType Site
Localion
Approximate
Constiuction
Cosl
Drainage
Area
(acres)
Design
Storm
fin.)
Design
Peak Flow
(cfs)
Wcl
Season
Numher
of
Slorms
TSS Niliaic Niiriic Dissolved
Phosphorous
Tolal
Phosphorus
TKN Bcncl'lclal
Uses
Los Angeles Area
Bio Slrip
- are broad surfaces
wilh a full grass cover
that allows slorm water
to llow in a relalively
thin sheets.
Aliudcnu
Maint
Slalion
$218,000 1.7 1.0 1.2 N/A N/A N/A N/A N/A N/A N/A N/A RECl,
REC2
Infiltralion Trench
-a trench is a depression
used ID treal small
drainage areas by
detaining slorm water
I'or shorl periods until it
percolates to the
proundwaler table.
Altadena
Maint
Slalion
(built w/ bio
slrip)
1.7 1.0 1.2 N/A N/A N/A N/A N/A N/A N/A N/A RECl,
REC2
Bio Strip I-60.S/SR91 $193,000 0.5 1.0 O.I N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl.
REC2,
SPWN,
WILD,
GWR
Bio Swale
- ure vegetated
conveyance channels
(typically trapezoidal
shaped) whecre slorm
waler llow passes
ihrough ihc grass al a
specific depth.
1-60.S/SR9I (buill w/ bio
strip)
0.2 1.0 0.1 N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl,
REC2,
SPWN,
WILD.
GWR
Bio Swale Cerrilos
Mainl
Station
$.59,000 0.4 1.0 0.1 N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl,
REC2,
SPWN,
WILD.
GWR
Caltrans - Best Management Practices Pilot Studies
Removal EITiciency 'J h
BMPType Sile
Localion
Approximale
Construction
Cost
Drainage
Area
(acres)
Design
Slorm
(in.)
Design
Peak Flow
(cfs)
Wei
Season
Numbcr
of
Slorms
TSS Nilrale Nilrile Dissolved
Phosphorous
Tolal
Phosphorus
TKN Beneficial
Uses
Bio Swale 1-.5/1-605 $97,000 0.7 1.0 0.3 N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl,
REC2,
SPWN,
WILD,
GWR
Bio Swale l-605/Del
Amo Ave
$124,000 0.7 1.0 0.2 N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl,
REC2,
SPWN,
WILD,
GWR
Infiltration Basin
- a basin is a depression
used lo treat larger
drainage areas by
detaining slorm waler
lor short periods until il
pcrcolales to the
groundwaier lable.
1-605/SR9I $273,000 4.2 1.0 0.9 N/A N/A N/A N/A N/A N/A N/A N/A RARE.
RECl,
REC2.
SPWN,
WILD,
GWR
Drain Inlet Inserl
(slream guard)(a)
- sock type inserts lhal
allow collecled waler lo
filter Ihrough the
geotextile fabric.
Las Floras
Mainl
Station
$88,000 0.2 1.0 O.I N/A N/A N/A N/A N/A N/A N/A N/A WILD
Drain Inlel Inscil (fossil
filler)
- irough lype inserts
filled with granular
amorphous alumina
silicate media.
Las Flores
Mainl
Slalion
(built w/Dli
(a))
0.8 1.0 0.2 N/A N/A N/A N/A N/A N/A N/A N/A WILD
Drain Inlel Inserl
(stream guard)(a)
Rosemead
Maint
Station
$65,000 0.3 1.0 O.I N/A N/A N/A N/A N/A N/A N/A N/A WILD,
GWR,
RECl,
REC2,
WARM
Caltrans - Best Management Practices Pilot Studies
Removal Eincicncy ' 7(.
BMPType Site
Location
Approximale
Conslruclion
Cosl
Drainage
Area
(acres)
Design
Storm
(in.)
Design
Peak Flow
(cis)
Wcl
Season
Numbcr
of
Slorms
TSS Nilralc Nitrite Dissolved
Phosphorous
Tolal
Phosphorus
TKN Bcnellcial
Uses
Drain Inlel Inserl (fossil
filler)
Rosemead
Mainl
Station
(buill w/DM
(a))
1.2 1.0 0.5 N/A N/A N/A N/A N/A N/A N/A N/A WILD,
GWR,
RECl,
REC2,
WARM
Drain Inlel Inserl
(stream guard)(a)
Foothill
Maint
Slalion
$68,000 0.2 1.0 0.0 N/A N/A N/A N/A N/A N/A N/A N/A WILD,
GWR,
MUN,
RECl,
REC2,
WARM
Drain Inlet Insert (fossil
lllter)
Foolhill
Mainl
Slalion
(buill w/ DII
(a))
1.6 1.0 0.4 N/A N/A N/A N/A N/A N/A N/A N/A WILD,
GWR,
MUN.
RECl,
REC2,
WARM
Extended Dcienlion
Basin^
- is a depression lined
wilh cither vegclalcd
soils or concrete.
1-.VI-605
Inlerscclion
$142,000 6.8 1.0 5.3 1998-
1999
2 -89
lo
-71
-84 lo
23
N/A N/A -84 to
-81
-83
to
-92
RARE,
RECl,
REC2,
SPWN,
WILD,
GWR
lixleiided Dcienlion
Basin^
1-60.VSR9I
Inlerscclion
$137,000 0.8 1.0 1.2 1998-
1999
3 -8()
lo
-58
-54 lo
2
N/A N/A 15 to
222
-8 10
339
RARI-,
RECl,
REC2,
SPWN,
WILD,
GWR
Caltrans - Best Management Practices Pilot Studies
Removal EITiciency %
BMP Type Sile
Localion
Approximate
Consiruction
Cosl
Drainage
Area
(acres)
Design
Slorm
(in.)
Design
Peak Flow
(cts)
Wcl
Season
Numbcr
of
Slorms
TSS Nilralc Nilrile Dissolved
Phosphorous
Tolal
Phosphorus
TKN Beneficial
Uses
Media Filter^
- designed removes fine
sediment and particulate
pollutants ihrough Iwo
concrete lined vaults
(sedimentation vaull
and filtering vaull).
Three filler types 1)
Auslin - open lopped, 2)
Delaware - closed
lopped, 3) canister -
uses pearlite/zeolite
media.
Eastern
Reg. Mainl
Sla
$341,000 1.5 1.0 1.9 1998-
1999
1 -34 112 N/A N/A 10 108 WILD,
GWR,
REC2,
WARM
Media Filter^ Foolhill
Maint
Station
$479,000 1.8 1.0 3.0 1998-
1999
2 -42
lo
-34
285 to
289
N/A N/A -7 to
83
42 to
140
WILD,
GWR,
MUN.
RECl,
REC2,
WARM
Media Filler Terminatio
n Park &
Ride
$450,000 2.8 1.0 3.6 N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl,
REC2,
SPWN,
WILD,
GWR
Media Filler Paxton
Park &
Ride
.$331,000 1.3 1.0 1.7 N/A N/A N/A N/A N/A N/A N/A N/A GWR,
REC2
r
Caltrans - Best Management Practices Pilot Studies
BMPType Sile
Localion
Approximale
Consiruction
Cost
Drainage
Area
(acres)
Design
Storm
(in.)
Design
Peak Flow
(cfs)
Wet
Season
Numbcr
of
Storms
Removal Efficiency %
TSS Nilrale Nilrile Dissolved
Phosphorous
Tolal
Phosphorus
TKN Beneficial
Uses
Mulli-Chambered
Treatment Train
- Three chamber
mechanism 1) calch
basin, which functions
primarily as a screening
process, 2) sellling
chamber, which
removes settleable
solids with plate
separators and sorption
pads, 3) media filler,
which uses a
combinaiion of sorption
(through layers of sand
and peal covered by
filler malerial) and ion
exchange.
Via Verde
Park &
Ride
$375,000 1.1 .0 1.7 N/A N/A N/A N/A N/A N/A N/A N/A WILD,
WET,
GWR,
RECl,
REC2,
WARM
Multi-Chambered
Treatment Train
Metro
Mainl
Station
$893,000 4.6 6.6 N/A N/A N/A N/A N/A N/A N/A N/A GWR,
RECl,
REC2.
WARM
Mulli-Chambered
Treatment Train
Lakewood
Park &
Ride
$456,000 1.0 2.8 N/A N/A N/A N/A N/A N/A N/A N/A RARE,
RECl,
REC2,
SPWN,
WILD,
GWR
Caltrans - Best Management Practices Pilot Studies
Removal Efllcieney ' %
BMPType Sile
Localion
Approximale
Conslruclion
Cosl
Drainage
Area
(acres)
Design
Slorm
(in.)
Design
Peak Flow
(cfs)
Wcl
Season
Number
of
Slorms
TSS Nilrale Nilritc Dissolved
Phosphorous
Total
Phosphorus
TKN Bcnellcial
Uses
Continuous Dellection
Separalor
- a pre casl underground
unit placed downstieam
of Ireeway drain inlcls
lo caplure sedimenl and
debris. The unit creales
a vortex of water lhal
allows waler to escape
thiough screens, while
contaminanis are
dellccted into a sump,
and later removed.
1-210/Orcas
Ave
$62,000 l.l 1.0 0.3 N/A N/A N/A N/A N/A N/A N/A N/A WILD,
GWR,
RECl,
REC2,
WARM
Continuous Dellection
Separalor
1-
210/Filmor
eSl
$63,000 2.5 1.0 0.6 N/A N/A N/A N/A N/A N/A N/A N/A WILD,
GWR,
RECl,
REC2.
WARM
Media Filler (composl) N.
Hollywood
Maint Sta
$40,000 3.0 0.7 1.0 1997-
1998
5 -155 7 29 38' 28' 43
I.
Media Filler (compost) Bonita
Canyon
1.7 0.8 6.0 1997-
1998
5 72 -172 -233 -1633 -320 -133
Exiended Detention
Basm
El Toro 68 0.8 30.4 1997-
1998
5 88 15 61 22 57 40 RARE,
RECl,
REC2,
SPWN,
WILD,
GWR
San Diego Area
Caltrans - Best Management Practices Pilot Studies
Removal EITiciency '• /(.
BMPType Sile
Localion
Approximale
Conslruclion
Cosl
Diainage
Area
(acres)
Design
Slorm
(in.)
Design
Peak Flow
(cfs)
Wet
Season
Numbcr
of
Storms
TSS Nilrale Nilrile Dissolved
Phosphorous
Total
Phosphorus
TKN Beneficial
Uses
Exiended Delenlion
Basin
1-
.5/Manchesl
cr (casl)
$369,000 4.8 1.3 4.6 N/A N/A N/A N/A N/A N/A N/A N/A RECl,
REC2,
BIOL,
EST,
WILD,
RARE,
MAR,
MIGR
Exiendcd Detention
Basin
1-.5/SR56 $166,000 5.3 1.3 5.7 1998-
1999
5 23
10
80
-100
to 64
-65 to
68
-84
to 43
BIOL,
EST,
MAR,
MIGR,
RARE,
RECl,
REC2,
SHELL
WILD
Exiended Detention
Basin
1-I.5/SR78 $855,000 13.4 1.9 9.5 1998-
1999
4 45
lo
72
-240
10.58
-299 to -62 -101
10 19
AGR.
COLD,
MUN,
RECl,
REC2,
WARM,
WILD
Infiltration Basin l-.5/La
Cosla
(wesl)
$241,000 3.2 1.3 3.0 N/A N/A N/A N/A N/A N/A N/A N/A BIOL,
EST,
MAR,
MIGR,
RARE,
RECl,
REC2,
WARM
Caltrans - Best Management Practices Pilot Studies
Removal EITiciency %
BMP Type Sile
Localion
Approximale
Conslruclion
Cosl
Drainage
Area
(acres)
Design
Slorm
(in.)
Design
Peak Flow
(cfs)
Wcl
Season
Number
of
Slorms
TSS Nilralc Nilrile Dissolved
Phosphorous
Total
Phosphorus
TKN Beneficial
Uses
Wel Basin
- a basin consisting ofa
permanent pool of waler
surrounded by a variety
of wetland planl
species.
l-.5/La
Cosla (east)
$694,000 4.2 1.3 2.2 N/A N/A N/A N/A N/A N/A N/A N/A RECl,
REC2,
BIOL
EST.
WILD,
RARE,
MAR,
MIGR
Media Filter
(pearolile/zeolite)
Kearny
Mesa Maint
Sla
$340,000 1.5 0.9 2.7 1998-
1999
3 -27
lo
20
5 10
29
-115 10 46 5 10
32
REC2,
WARM,
WILD
Media Filler (sand lype
11)
Escondido
Maint
Station
$451,000 0.8 1.0 2.2 1998-
1999
3 Oto
66
1 1 10
70
-23 10 70 56 10
84
MUN,
AGR,
RECl,
REC2,
WARM
COLD.
WILD
Media Filler (sand lype
1)
La Cosla
Park &
Ride
$242,000 2.8 0.9 2.3 1998-
1999
3 54
10
98
-98 10
4
-113 10 26 -28
lo38
BIOL
EST,
AMR,
MIGR,
RARE,
RECl,
REC2,
WARM
Media Filler (sand lype
1)
SR78/1-5
Park &
Ride
$231,000 0.8 1.0 2.7 1998-
1999
2 54 -313 -7 10 28 7 10
11
BIOL,
MAR,
RARE,
RECl,
REC2,
WARM,
WILD
Bio Swale SR78/Mclr
ose Dr
$1.56,000 2.4 1.2 6.1 N/A N/A N/A N/A N/A N/A N/A N/A AGR,
OMD,
RECl,
REC2,
WARM,
WILD
Caltrans - Best Management Practices Pilot Studies
Removal Etficiency ' 7f.
BMPType Site
Localion
Approximate
Conslruclion
Cosl
Drainage
Area
(acres)
Design
Slorm
(in.)
Design
Peak Flow
(cfs)
Wcl
Season
Number
of
Slorms
TSS Nitrate Nilrile Dissolved
Phosphorous
Tolal
Phosphorus
TKN Beneficial
Uses
Bio Swale 1-5/Palomar
Airport Rd
$142,000 2.3 N/A 3.8 N/A N/A N/A N/A N/A N/A N/A N/A REC2,
WARM,
WILD
Bio Slrip Carlsbad
Mainl Sta
(west)
$196,000 0.7 N/A 1.3 N/A N/A N/A N/A N/A N/A N/A N/A REC2.
WARM,
WILD
Infiliralion Trench/Strip Carlsbad
Mainl Sla
(easi)
(buill w/ bio
slrip)
1.7 1.3 2.9 N/A N/A N/A N/A N/A N/A N/A N/A REC2,
WARM,
WILD
' Callrans. Compost Storm Water Filters (CSFs). Bonita Canyon <fi North Hollywood Maintenance Yard, Storm Water Monitoring. 1998,' Caltrans. El Toro Detention Basin.
Slorm Water Moniloring. 1998.
Dissolved Phosphorus higher than Tolal Phosphorus concentrations, due lo resuhs from slorm 4. Without storm 4, efficiencies are -36% tor dissolved phosphorus and 7% tor
total phosphorus,
N/A - Not Available al this time, • Preliminary Information.
APPENDIX 2
NATION WIDE BMP TREATMENT CONTROLS
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Control (Source) Limilations Benefits Removal Efficiency Capilal Cosl
(approximate)
O&M Cosl
(approximate)
Infiliralion - a family of treatment
systems in which the majority of the
runoff from small storms is infiltrated in
the ground ralher than discharged into a
surface water body. (1)
Infiltration Trench - is an excavated
trench (3 lo 12 feel deep), backfilled with
stone aggregate, and lined wilh filler
fabric. (23)
It is used to treal a small poriion of the
runoff by deiaining slorm water for shorl
periods until it percolates down to Ihe
groundwaier table. (21)
Useful life is usually around 10 years.
(20)
•potential loss of infiltrative
capacity. (1)
•applicability depends on
specific site
characlerislics/oppoitunilies
(slope, soil types, proximity
lo waler table). (23)
•potential groundwater
contamination. (1)
•not suitable for sites that
conlain chemical or
hazardous material. (23)
•may need to be preceded
by appropriate prelrealmenl.
(23)
•relalively short life span.
(23)
•efficient removal of
pollutants. (1)
•can recharge groundwater
supplies. (2)
•provides localized
streambank erosion control.
(2)
•easy lo fil inio unutilized
areas of developmenl sites.
(2)
•an effective runoff
control. (I)
•increases basetlow in
nearby streams. (23)
•Low land use
requirement, (20)
• nitrogen compounds
40% to 80%, (2)
• phosphorus compounds
40% to 80%, (2)
• combined nilrogen and
phosphorus compounds
45% lo 75% (depending on
design). (8)
• tolal suspended solids
75%. (20)
•tolal phosphorous 60%..
(20)
• lolal nilrogen 55%. (20)
•COD 65%. (20)
• Lead 65%. (20)
• Zinc 65%.. (20)
• $4,900/acre
(proraled using
ENR index from
1992 cosl). (5)
•$3.6 to
$10.70/cubic feel
slorage (prorated
using ENR index
from 1986 cost).
(20)
• $l,800/acre/year
(proraled using
ENR index from
1992 cost). (5)
•9% of Capilal
Cost (20)
Pond (Basin) - consist of shallow, flat
basins excavated in pervious ground, with
inlet and outlet structures to regulate
llow. (19)
Useful Life is usually around 25-years.
(20)
•potential loss of infiltrative
capacity. (1)
•low removal of dissolved
pollulanis in very coarse
.soils. (1)
•possible nuisance (odor,
mosquito). (2)
•frequent mainlenance
requirement. (2)
•risk of groundwater
contamination. (1)
• High land use requirement.
(20)
•achieves high levels of
parliculale pollutant
removal. (1)
• can recharge groundwater
supplies. (2)
•an effective runoff
conlrol. (1)
•can serve iribuiary areas
up to 50 acres. (1)
•provides localized
streambank erosion control.
(2)
•cosl effective. (2)
• nitrogen compounds
40%. to 80%. (2)
• phosphorus compounds
40% to 80%.. (2) r
• combined nitrogen and 1
phosphorus compounds \
45'/(. to 75% (depending on
design). (8)
• tolal suspended solids
75%. (20)
•lolal phosphorous 65%.
(20)
• tolal nitrogen 60%. (20)
•COD 65%.. (20)
• Lead 65%. (20)
• Zinc 65%. (20)
• $36,900/million
gallons (prorated
using ENR index
from 1992 cost).
(5)
• $0.60 to
$1/cubic feet
slorage (prorated
using ENR index
from 1986 cosl).
(20)
* $l,200/million
gallons/year
(proraled using
ENR index from
1992 cost). (5)
• 7%. of Capilal
Cosl (20)
Nationwide Examples of Treatment Control (Structural) Best Management Practices (BMPs)
Treatment Control (Source) Limilations Benefils Removal Ef ficiency Capital Cost
(approximate)
O&M Cost
(approximale)
Porous Pavement - is an alternative lo
convenlional pavement whereby runoff is
diverted Ihrough a porous asphalt layer
and into an underground stone reservoir.
(10)
Useful life is around 10 years. (20)
Jl potential loss of infiltrative
capacity. (1)
Ji75%' failure rate due to
clogging, resurfacing or just
failure afler construction,
(10)
Jihigh maintenance -
requires special vacuum
sweeping or jet hosing, (10)
Jimay require twice as much
material as without porous
pavement to achieve the
needed strength. (10)
Jl unsuitable in fill sites and
steep slopes, (5)
Jl potential risk of
groundwater contamination,
(1)
•limiled efficiency (6
months). (23)
J.achieves high levels of
pollulani removal. (1)
Jl groundwaier recharge. (2)
Jl localize streambank
erosion conlrol. (2)
J. reduced land
consumption. (2)
Jielimination of curbs and
gutters, (2)
Jl safer driving surface. (2)
• nitrogen compounds
60% to 80%. (2)
• phosphorus compounds
40%. lo 80%. (2)
•nilrogen and phosphorus
compounds 45%' lo 75%
(depending on design). (8)
• sedimem 82 to 95%. (23)
• tolal phosphorus
compounds 65%. (23)
• total nilrogen compounds
80 10 85%. (23)
• tolal suspended solids
90%. (20)
•tolal phosphorous. 65%
(20)
• lotal nilrogen 85%, (20)
•COD 80%. (20)
• Lead 100%. (20)
• Zinc 100%. (20)
• $123,000/acre
(prorated using
ENR index from
1992 cosO. (5)
* $2.IO/square
feet (prorated
using ENR index
from 1987 cost)
(incremental cost
beyond the
conventional
asphalt pavement).
(20)
• $250/acre/year
(prorated using
ENR index from
1992 cost). (5)
• $0.14/square
feet/year (proraled
using ENR index
from 1987 cost),
(incremental cosl
beyond the
conventional
asphalt pavement).
(20)
Concrele Grid Pavement - are lattice grid
structures with grassed or pervious
material placed in the grid openings. (I)
Useful life is usually around 20 years.
(20)
Jl require regular
mainlenance. (20)
Jinol suitable for high traffic
areas. (20)
J. potential groundwaier
contamination. (20)
Jionly feasible where soil is
permeable. (20)
Jl groundwaier recharge.
(20)
Jican provide peak tlow
conlrol. (20)
•lolal nilrogen 90%. (20)
• total phosphorus
compounds 90%. (20)
• lotal suspended solids
90%. (20)
•COD 90%. (20)
• Lead 90%. (20)
• Zinc 90%, (20)
• $1.7 -$3.5/tr
(prorated using
ENR index from
1981 cosO
(incremental cost
beyond the
conventional
asphalt pavement)
(20)
• -$0.07/tr feet
(proraled using
ENR index from
1981 cost)
(incremental cost
beyond the
conventional
asphalt pavement)
(20)
Infiltration Drainfields - a system
composed ofa pretreatment structure, a
manifold sy-stem, and a drainfield. (28)
•high mainlenance when
sedimenl loads are heavy.
(28)
•short life span if not well
maintained. (28)
•nol suitable in regions wilh
clay or silly soils. (28)
•anaerobic conditions could
clog the soil. (28)
•potential groundwaier
conlaminaiion. (28)
Jl groundwaier recharge.
(28)
•used lo control runoff,
(28)
• depends on design - little
monitoring data currenlly
available, Polenlially
100% of pollulani could be
prevented from entering
surface waler. (28)
Approx. $72,000
for a drainfield
wilh dimensions:
100 fl long, 50
feel wide, 8 feel
deep wilh 4 ft
cover. (28)
APPENDIX 3
TABLE 6: GRASS LINED BIOFILTER BMP DISCHARGE
AND
TREATMENT AREA
TABLE 6
GRASS LINED BIOFILTER BMP DISCHARGE AND TREATMENT AREA
Treatment Discharge
Location PA Area: A Runoff Intensity: l<^' Treatnnent Grass Swale Grass Swale
Coefficient: C Discharge Q Treatment Area Length
(ac) (in / hr) (cfs) (sqft) (ft)
PAI 2.3 0.95 0.2 0,4 1840 37
PA2 21.9 0.95 0.2 4.2 17520 350
PA3a 25.5 0.95 0.2 4.8 20400 408
PA3b 21.0 0.95 0.2 4,0 16800 336
PA4 39.0 0.95 0.2 7.4 31200 624
PAS 31.0 0.95 0.2 5.9 24800 496
Notes:
(1) Intensity, I = BMP design rainfall intensity per State Water Quality Control Board Order Num
(2) Treatment Discharge Q = CIA.
(3) Grass Swale Treatment Area assumes a minimum treatment area of 1000 sq-ft per impervious acre. The
industrial sites are assumed to be 80% impervious.
(4) Grass Swale length assumes a 50 foot wide swale.
APPENDIX 4
TABLE 7: INDIVIDUAL PLANNING AREA
WET POND/RETENTION BASIN TREATMENT VOLUMES
AND
BASIN GEOMETRIES
Table 7
Bressi Ranch
Basin Treatment Volumes
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-1 2.3 100188 0.60 0.05 5009
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
50
33
25
20
33
22
17
13
25
17
13
10
17
11
8
7
13
8
6
5
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-2 22 953964 0.60 0.05 47698
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth Calculated Basin Width or Lenath
(ft) (ft)
2 477 318 238 159 119
3 318 212 159 106 79
4 238 159 119 79 60
5 191 127 95 64 48
Table 7
Bressi Ranch
Basin Treatment Volumes
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-3a 25.5 1110780 0.60 0.05 55539
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenqth
(ft)
2
3
4
5
555
370
278
222
370
247
185
148
278
185
139
111
185
123
93
74
139
93
69
56
Treatment Vo ume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-3b 21 914760 0.60 0.05 45738
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
457
305
229
183
305
203
152
122
229
152
114
91
152
102
76
61
114
76
57
46
Table 7
Bressi Ranch
Basin Treatment Volumes
Treatment Vo ume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-4 39 1698840 0.60 0.05 84942
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
849
566
425
340
566
378
283
227
425
283
212
170
283
189
142
113
212
142
106
85
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-5 31 1350360 0.60 0.05 67518
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
675
450
338
270
450
300
225
180
338
225
169
135
225
150
113
90
169
113
84
68
APPENDIX 5
TABLE 8: COMBINED PLANNING AREA
WET POND/RETENTION BASIN TREATMENT VOLUMES
AND
BASIN GEOMETRIES
Table 8
Bressi Ranch
Basin Treatment Volumes
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-1-PA-5 140.7 6128892 0.60 0.05 306445
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenqth
(ft)
2
3
4
5
3064
2043
1532
1226
2043
1362
1021
817
1532
1021
766
613
1021
681
511
409
766
511
383
306
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-3a-PA-5 116.5 5074740 0.60 0.05 253737
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
2537
1692
1269
1015
1692
1128
846
677
1269
846
634
507
846
564
423
338
634
423
317
254
Table 8
Bressi Ranch
Basin Treatment Volumes
Treatment Volume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-3a+3b 46.5 2025540.0 0.6 0.05 101277
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
1013
675
506
405
675
450
338
270
506
338
253
203
338
225
169
135
253
169
127
101
Treatment Vo ume
Location PA area
(acres)
PA area
(ft)
Treatment
Precipitation
(in)
Treatment
Precipitation
(ft)
Treatment
Volume
(cuft)
PA-4-I-PA-5 70 3049200 0.60 0.05 152460
Basin Width or Lenqth
(ft)
50 75 100 150 200
Basin Depth
(ft)
Calculated Basin Width or Lenath
(ft)
2
3
4
5
1525
1016
762
610
1016
678
508
407
762
508
381
305
508
339
254
203
381
254
191
152
APPENDIX 6
INDUSTRIAL STORM WATER SOURCE CONTROL BMPS
4. SOURCE CONTROL BMPs
iNTRODUCnON
m This chapter
^ describes specific
source control
•MHH^B^M^BHHH Best
Management
Practices (BMPs) for common industrial
activities that may pollute storm water. Chapter
2 led you through the steps of identifying
activities at your facility that can pollute storm
water while Chapter 3 provided guidance on
selection of BMPs. This chapter provides you
with the BMPs that best fill your facility's need.
Best management practices for each of the
activities shown below are provided in the
following fact sheets.
Each fact sheet contains a cover sheet with:
• A description of the BMP
• Approach
• Requirements
- Cost, including capital costs, and
Operation and Maintenance (O&M)
- Maintenance (including administrative and
staffing)
• Limitations
The side bar presents information on where this
BMP applies, targeted constituents, and an
indication of the level of effort and cost to
implement
Further information is also provided in
additional sheets. This information includes a
more detailed description of the BMP,
requirements to implement, examples of
effective programs, and references.
BMPs are provided for each of die following
industrial activities consistent with Worksheet 4
in Chapter 2.
Industriai Activities Requiring BMPs
SCI Non-Sttxm Water Discharges to
Drains
SC2 Vehicle and Equipment Fueling
SCS Vehicle and Equipment Washing and
Steam Cleaning
SC4 Vehicle and Equipment Maintenance
and Repair
SCS Outdoor Loading/Unloading of
Materials
SC6 Outdoor Container Storage of Liquids
SC7 Outdoor Process Equipment
Operations and Maintenance
SCS Outdoor Storage of Raw Materials,
Products, and By-Products
SC9 Waste Handling and EHsposal
SCIO Contaminated or Erodible Surface
Areas
sen BuUding and Grounds Maintenance
SC12 Building Repair, Remodeling, and
Construction
SCB Over-Water Activities
SCM Employee Training
Fact sheet SCM, Employee Training, is a
compilation of the training aspects of the
individual source control fact sheets. Its
purpose is to facilitate the integration and
development of a comprehensive training
program for all industrial activities at a facility.
Industrial Handbook 4-1 March, 1993
ACTIVITY: NON-STORM WATER DISCHARGES TO DRAINS Applications
C^^^^Manufacturing^^^
Material Handling
CZyehicIe Maintenan^^
Caitstruction
C^ommerviaf Activit^^^
Roadways
.Waste Containrnent^
iousekeeping Practices^
DESCRIPTION
Eliminate non-storm water discharges to tbe storm water collection system. Non-stoim
water discharges may include: process wastewaters, cooling waters, wash waters, and
sanitary wastewater.
APPROACH
The foUowing approaches may be used to identify non-storm water discharges:
• Visual Inspecuon
The easiest method is to inspect each discharge point during dry weather.
Keep in mind tbat drainage from a storm event can continue for three days or
more and groundwater may infiltrate the underground stonn water coUection
system.
• Piping Schematic Review
The piping schematic is a map of pipes and drainage systems used to cany
wastewater, cooling water, sanitary wastes, etc.
A review of tbe **as-buUf* piping schematic is a way to determine if there are any
connections to the storm water collection system.
Inspea tbe path of floor drains in older buildings.
• Smdce Testing
Smoke testing of wastewater and storm water coUection systems is used to detea
connections between tbe two systems.
During dry weather tbe storm water coUection system is filled with smoke and
then traced to sources. Tbe :q>pearance of smoke at ttie base of a toUet indicates
that there may be a connection between the sanitaiy and the storm water system.
• Dye Testing
A dye test can be perfonned by simply releasing a dye mto eidier your sanitary
or process wastewater system and examining the discharge points from tbe stonn
water coUection system for discoloration.
REQUIREMENTS
Costs (Capital, O&M)
• Can be difficult to locate illicit connections especially if there is groundwater
infiltration.
LIMITATIONS
• Many Polities do not have accurate, up-to-date schematic drawings.
• TV and visual inspections can identify illicit connections to the stom sewer, but
fiirtber testing is sometimes required (e.g. dye, smoke) to identify sources.
Targeted Constituents
O Sediment
9 Nutrients
0 Heavy Metafs
9 Toxic Materiais
O Fhatable Materials
9 Oxygen Demand-
ing Substances
• OiVA Grease
0 Bacteria & Viruses
• UkeiytoHave
Significant Impact
O Proltabim Low or
Unlmown Impact
Implementation
Requirements
Q Capital Costs
O O&M Costs
O Maintenance
O Training
High O Low
SCI
Best'
Management
Practlces>
Industrial Handbook 4-2 March, 1993
Additional Information — Non-Storm Water Discharges to Drains
Facilities subject to storm water pennil requirements must include a certification that tbe storm water coUection system
has been tested or evaluated for the presence of non-stonn water discharges. Thc State's General Industrial Stonn Water
Permit requires tbat non-storm water discharges be eliminated prior to implementation of tbe faciUty's SWPPP.
Non-storm water discharges to the storm water collection system may include any water used directiy in die manufaour-
ing process (process wastewater), air conditioning condensate and coolant, non-contact cooUng water, cooling equipment
condensate, outdoor secondary contamment water, vehicie and equ^nnent wash water, sink and drinking fountain
wastewater, sanitary wastes, or other wastewaters. Tabic 4.1 presents disposal option infonnation for specific types of
wastewaters.
To ensure diat the storm water system discharge contains only storm water, industiy should:
• Locate discbarges to tbe municipal storm sewer system or waters of die United States from the industrial
stc»m sewer system fiom:
"as-buUt" pipeline schematics, and
visual observation (walk boundary of plam site).
• Locate and evaluate aU discbarges to the industrial storm sewer system (including wet weather flows) from:
"as-buiir pipeline schematics,
visual observation,
dye tests,
TV camera.
chemical field test kits, and
smdce tests.
• Devekip plan to eliminate illicit connectims:
rqilumb sewer lines,
isolate problem areas, and
plug iUicit discharge points.
• Develop disposal options.
• Document diat non-stonn water discharges have been eUminated by recording tests performed, methods
used, dates of testing, and any c»i-site drainage points observed.
REFERENCES
General Industrial Storm Water Permit, SWRCIB, 1992.
NPDES General Pennit for Discbarges of Stonn Water Assodated with Industrial Activity in Santa Claxa. County
to South San Francisco Bay or its Tributaries, SFBRWQCB, 1992.
Stonn Water Management for Industrial Activities: Devefoping PoUution Prevention Plans, and Best Manage-
ment Practices, EPA 832-R-92-<X)6, USEPA, 1992..
Industrial Handbook 4-3 March, 1993
5* a.
g
£
s a
TABLE 4.1 QUICK REFERENCE - DISPOSAL ALTERNATIVES
(Adopted from Santa Clara County Nonpoint Source Pollution Conu-ol Program - December 1992)
All of die waste products on tliis chart arc prohibited from discharge to die storm drain system. Use Uiis matrix lo decide which altemalive disposal sUategies to use.
ALTERNATIVES ARE LISTED IN PRIORITY ORDER.
Key: HHW Household hazardous waste (Government-sponsored drop-off events)
POTW Publically Owned Treatment Plant
Reg.Bd. Regional Water Quality Conti'ol Board (Oakland)
"Dispose to sanitary sewer" means dispose into sink, toilet, or sanitary sewer clean-out connecUon.
"Dispose as trash" means dispose in dumpsters or trash containers for pickup and/or eventual disposal in landfill.
"Dispose as hazardous waste" for business/commercial means conti'act wiUi a hazardous waste hauler to remove and dispose.
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL
Disposal Priorities Approval
RESIDENTIAL
Disposal Priorities
General Construction and PaintinK; Street and Utility Maintenance
Excess paint (oil-based) 1. Recycle/reuse.
2. Dispose as hazardous waste.
1. Recycle/reuse.
2. Take to HHW drop-off.
Excess paint (water-based) 1. Recycle/reuse.
2. Dry residue in cans, dispose ns trash.
3. If volume is (oo much to dry,
dispose as hazardous waste.
1. Recycle/reuse.
2. Dry residue in cans, dispose as trash.
3. If volume is too much to dry, take to
HHW drop-off
Point cleanup (oil-based) Wipe paint oul of brushes, tlien:
1. Filter & reuse Uiinners, solvents.
2. Dispose as hazardous waste.
Wipe paint out of brushes, tlien:
1. Filter & reuse lliiiiiiers, solvents.
2. Take to HHW drop-off.
Paint cleanup (water-based) Wipe paint out of brushes, dieii:
1. Rinse to smiitary sewer.
Wipe paint oul of brushes, then:
1. Rinse to siuiilary sewer.
Empty paint cans (dry) 1. Remove lids, dispose as u°nsh. 1. Remove lids, dispose as unsli.
Paint stripping (wiUi solvent) 1. Dispose as hazardous waste. 1. Take to HHW drop-olf.
Building exterior cleaning (high-
pressure water)
1. Prevent entry into storm drain and
remove offsite
2. Wash onto dirt area, spade in
3. Collect (e.g. mop up) and
discharge to sanitary sewer POTW
Cleaning of building exteriors which
have HAZARDOUS MATERIALS (e.g.
mercury, lead) in paints
1. Use dry cleaning methods
2. Conlain nnd dispose washwater as
hazardous wnste (Suggestion: dry
material first to reduce volume)
J^
J^
o
Table 4.1 (Continued)
Page 2
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL
Disposal Priorities Approval
RESIDENTIAL
Disposal Priorities
General ConstrucUon and Painting; Street and Utility Maintenance (cont'd)
Non-hazardous paint saaping/
sand blasting
1. Dry sweep, dispose as trash 1. Dry sweep, dispose as irash
HAZARDOUS paint scraping/sand blasting
(e.g. marine paints or paints containing
lead or tributyl tin)
1. Dry sweep, dispose as
hazardous waste
1. Dry sweep, take lo HHW drop-olf
Soil from excavations during periods
when storms are forecast
1. Should not be placed in street or
on paved areas
2. Remove from site or backfill by
end of day
3. Cover wiUi tarpaulin or surround
wiUi hay boles, or use oUier
runoff controls
4. Place niter mat over storm drain
Note: Thoroughly sweep following removal of
dirt in nil four altematives.
-
Soil from excavations placed on paved
surfaces during periods when stonns are not
forecast
1. Keep material out of storm conveyance
systems and tiioroughly remove via
sweeping following removal of dirt
Cleaning streets in construction areas 1. Dry sweep and minimize tracking of
mud
2. Use silt ponds and/or similar pollutant
reduction techniques when Uushing
pavement
Soil erosion, sediments 1. Cover disturbed soils, use erosion
controls, block entry to storm drain.
2. Seed or plant immediately.
Fresh cement, grout, mortar 1. Use/reuse excess
2. Dispose to trash
1. Use/reuse excess
2. Dispose ns trash
Washwater from concrele/mortar
(etc.) cleanup
1. Wash onto dirt area, spade in
2. Pump nnd remove to appropriate
disposal facilily
3. Settle, pump water to sanitary sewer POTW
1. Wash onto dirt area, spade in
2. Pump and remove to appropriate
disposal facilily
3. Settle, pump water to snnitnry sewer
Aggregate wash from driveway/patio
consuuction
1. Wash onto dirt area, spade in
2. Pump and remove to appropriate
disposal facility
3. Settle, pump water to snnitnrv sewer POTW
1. Wash onto din area, spade in
2. Pump nnd remove to nppropriate
disposal facilily
3. Settle, pump water to sanitary sewer
Table 4.1 (Coniinued)
Page 3
5*
CL
I
S!
H
9 Ou
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL
Disposal Priorities Approval
RESIDENTIAL
Disposal Priorities
General Construction and Painting; Street and Utility Maintenance (cont'd)
Rinsewater from concrete mixing uucks 1. Return truck to yard for rinsing
into pond or dirt area
2. Al consu-uction site, wash into pond
or dirl area
Non-hazardous consiruction and
demolition debris
1. Recycle/reuse (conaete, wood, etc.)
2. Dispose ns trash
1. Recycle/reuse (concrete, wood, etc.
2. Dispose ns uash
Hazardous demolition and
construction debris (e.g. asbestos)
1. Dispose as hazardous wasle 1. Do nol attempt to remove yourself.
Cpiitact asbestos removal service for
safe removal and disposal
2. Very small amounts (less tiian 5 lbs)
may be double-wrapped in plaslic and
taken lo HHW drop-off
Saw-cut slurry 1. Use dry cuuing technique and sweep
up residue
2. Vacuum slurry nnd dispose off-site.
3. Block Slonn drain or berm wiUi low
weir OS necessary to allow most solids
to settle. Shovel oul gutters; dispose
residue to dirl area, consU'uciion yard
or Inndfill.
Consuuction dewatering
(Nonturbid, uncontaminated groundwater)
1. Recycle/Reuse
2. Discluu-ge to stonn droin
Consuuction dewatering (Odier ilian
nonturbid, uncontaminated groundwater)
1, Recycle/reuse
2, Discluu-ge to sanitary sewer
3, As appropriate, Q-ent prior to discharge to stonn drain
POTW
Reg. Bd.
Portable toilet waste 1. Leasing company shall dispose
to sanitary sewer al POTW POTW
Leaks from garbage dumpsters 1. Collect, conlain leaking malerial.
Eliminate leak, keep covered,
retum lo leasing company for
immediate repair
2. If dumpster is used for liquid
waste, use plastic liner
4^
ft
Os
tr
C4
Table 4.1 (Continued)
Page 4
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL
Disposal Priorities Approval
RESIDENTIAL
Disposal Prtorities
General ConstrucUon and Painting; Street and Utility Maintenance (cont'd)
Leaks from consuuction debris bins 1. Insure dial bins are used for dry
nonhazardous materials only
(Suggestion: Fencing, covering help
prevent misuse)
Dumpster cleaning water 1. Clean al dumpster owner's facilily
nnd discharge waste Uirough grcnse
inierceptor to sanitary sewer
2. Clean on site and discharge Uirough
grease interceptor lo sanitary sewer
POTW
POTW
Cleaning driveways, paved areas *
(Special Focus = Restaurant alleys Grocery
dumpster areas)
* Note: Local drought ordinances may
contain additional resuictions
1. Sweep and dispose as U^ish
(Dry cleaning only).
2. For vehicle leaks, restaurant/grocery
alleys, follow tills 3-step process:
a. Clean up leaks wiUi rags or
absorbents.
b. Sweep, using granular
absorbent material (cat litter).
c. Mop and dispose of mopwater to
sanitary sewer (or collect rinsewater
and pump to tiie sanitnry sewer).
3. Same as 2 above, but wiUi rinsewater
(2c)(no saip) discharged lo stonn drain.
1. Sweep and dispose as ti^ash (Dry denning
only).
2. For vehicle leaks, follow this
3-stcp process:
a. Clean up leaks wiUi rags or
absorbents; dispose as hazardous
wnste.
b. Sweep, using granulnr
absorbenl material (cat litter).
c. Mop nnd dispose of mopwater
to sanitary sewer.
Steam cleaning of sidewalks, plazas *
* Note: Local droughl ordinances may
contain additional restrictions
1. Collect all water and pump to sanitary
sewer.
2. Follow Uiis 3-slep process:
a. Clean oii leaks wiUi rags or
adsorbents
b. Sweep (Use dry absorbent ns needed)
c. Use no soap, discharge to stonn drain
Potable water/line Hushing
Hydrant testing
1. Deactivate chlorine by
maximizing time waler will U-nvel
before reaching creeks
Super-chlorinated (above 1 ppm) waler
fnom line flushing
1. Discharge to sanitary sewer
2. Complete dechlorination required
before disclinrgc to stonn drain
Table 4.1 (Continued)
Page 5
5^ o.
6
E.
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL
Disposal Priorities Approval
RESIDENTIAL
Disposal Priorities
Landscape/Garden Maintenance
Pesticides 1. Use up. Rinse containers use
rinsewater as product. Dispose
rinsed containers as trash
2. Dispose unused pesticide as
hazardous waste
1. Use up. Rinse containers, use
rinsewater as pesticide. Dispose
rinsed container as b'ash.
2. Take unused pesticide to HHW drop-
off
Garden clippings 1. Compost
2. Take lo Landfill
1. Compost
2. Dispose ns tiusli.
Tree U'imming 1. Chip if necessary, before
composting or recycling
1. Chip if necessary, before composting
or recycling
Swiimning pool, spa. fountnin water
(emptying)
1. E>o nol use metal-based algicides (i.e.
Copper Sulfate)
2. Recycle/reuse (e.g. irrigation)
3. Detennine chlorine residual = 0, wail
24 hours and Uien discharge to stonn drain. POTW
1. Do not use nieuil-bascd algicides (i.e.
Copper Sullnte)
2. Recycle/reuse (e.g. irrigotion)
3. Detennine chlorine residual = 0, wait
24 hours and then discharge to stonn drain.
Acid or otiier pool/spa/fountoin cleaning 1. NeuU'alize and discharge to sanitary
sewer POTW
Swinuning pool, spa filter backwash 1. Reuse for irrigation
2. Dispose on dirl area
3. Seule, dispose to sanitary sewer
1. Use for ItUidsciipe imgation
2. Dispose on dirt area
3. SeUle, dispose to saniuvy sewer
Vehicle Wastes
Used motor oil 1. Use secondary contaiiunenl while
storing, send lo recycler.
1. Put out fur curbside recycling pickup
where available
2. Take lo Recycling Facility or aulo
service facility wiUi recycling program
3. Take lo HHW events accepting motor oil
Antifreeze 1. Use secondary containment while
storing, send lo recycler.
1. Take to Recycling Facility
OUier vehicle fluids and solvents 1. Dispose as hazardous waste 1. Take to HHW event
Automobile batteries 1. Send to auto battery recycler
2. Take lo Recycling Center
1. Exchmige nt relxiil ouUet
2. Take to Recycling Facility or HHW event
where batteries are accepted
Motor home/construction u-aller wasle 1. Use holding tank. Dispose to
saniuify sewer
1. Use holding tank, dispose to sanitary
sewer.
4>.
I
00
o a*
vo Oi
Table 4.1 (Continued)
Page 6
I
-1 E m u 3 a
r
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL RESIDENTIAL
Disposal Priorities Approvai Disposal Priorities
Vehicle Wastes (cont'd)
Vehicle Washing 1. Recycle
2. Discharge to saniuuy
sewer, never lo stonn drain
POTW
1. Take to Commercial Car Wash.
2. Wash over lawn or dirt area
3. If soap is used, use a bucket for soapy
waler and discharge remaining soapy
water to saniuuy sewer.
Mobile Vehicle Washing 1. Collect washwater and discharge lo
sanitary sewer. POTW
Rinsewater from dust removal at new cor
fleets
1. Discharge lo saniUuy sewer
2. If rinsing dust from exierior surfaces
from appearance purposes, use no soap
(water only); discharge to stonn drain. POTW
-
Vehicle leaks al Vehicle Repair Faciiities Follow Uiis 3-step process:
1. Clean up leaks witii rags or absorbents
2. Sweep, using granular absorbent
mnieriol (cat litter)
3. Mop nnd dispose of mopwater to
saniuu-y sewer.
Olher Wastes
Carpel cleaning solutions & oUier
mobile washing services
I. Dispose lo sanitary sewer POTW 1. Dispose to saiiiuu'y sewer
Roof drains 1. If roof is coiitiuninated wiUi
industiial waste producis,
discharge to sanitary sewer
2. If no contamination is preseni.
discharge lo storm drain
Cooling water
Ah- conditioning condensate
1. Recycle/reuse
2. Discharge to sanitiuy sewer POTW
Pumped groundwaier, infiitiation/
foundation drainage (contaminnled)
1. Recycle/reuse (landscaping, etc.)
2. Trent if necessary; discharge to
sanitary sewer
3. Treat and dischnrge to slonn drnin
Reg. Bd.
POTW
Reg. Bd.
Fire flgluing flows If containinuiion is present, Fire Dept.
will attempt lo prevent flow to stieain
or slonn drnin
vo
2
-1
n
vo vo
Table 4.1 (Continued)
Page 7
5* o.
•1
E
s
DISCHARGE/ACTIVITY BUSINESS/COMMERCIAL
Disposal Priorities Approval
RESIDENTIAL
Disposal Priorities
Olher Wastes (cont'd)
Kitchen Grease 1. Provide secondary conuiinmeiii. collect,
send to rccyler.
2. Provide secondary conUiiiiment, collect,
send to POTW via hauler.
POTW
1. CoUect, solidify, dispose as u-asli
Resuiurant cleaning of floor mats,
exhaust filters, etc. 1. Clean inside building witii discharge
Uirough grease tinp lo snnitnry sewer.
2. Clenn outside in coniaincr or benned
area wiUi dischnrge to snnitnry sewer.
Clean-up wnstewnter from sewer bnck-up 1. Follow tills procedure:
a. Block stonn drain, conuun, collect,
nnd return spilled matcrini to the
snniuu-y sewer.
b. Block storm drain, rinse remaining
material to collection point and
pump lo sanitary sewer, (no rinse-
water may flow to slonn droin)
vo VO Oi
ACTIV ITY: VEHICLE AND EQUIPMENT FUELING Applications
Manufacturing
JUaterial Handlin^^
"yehicle Maintenance
Construction
CQommercial Activiti^^
Roadways
Waste Containment
C^uselceeping Practi^s^
DESCRIPTION
Prevent fuel spills and leaks, and reduce their impacts to storm water.
APPROACH .
• Design the fueling area to prevent the runon of storm water and the runoff of spills:
Cover fueling area if possible.
Use a perimeter drain or slope pavement inward with drainage to sump.
Pave fueUng area with concrete rather tban asphalt
• Wbere covering is infeasible and the fuel island is surrounded by pavement, apply a
suitable sealant tbat protects tbe asphalt from spiUed fuels.
• If dead-end sump is not used to coUect spills, instaU an oil/water separator.
• InstaU vapor recovery nozzles to help control drips as well as air pollution.
• Discourage **topping-ofr of fuel tanks.
• Use secondary containment when transferring fuel from tbe tank truck to tbe fuel
tank.
• Use adsorbent materials on smaU spUIs and general cleaning ratiier tiian bosing down
die area. Remove tbe adsorbent materials prompdy.
• Carry out aU Federal and State requirements regarding underground sUKage tanks, or
instaU above ground tanks.
• Do not use mobUe fueling of mobUe industrial equipmoit around tbe facility; rather,
tian^n tbe equipment to designated fueling areas.
• Keep your SpiU Prevention Control and Countermeasure (SPCQ Plan up-to-date.
• Train employees in proper fueling and cleanup prtxxdures.
• Fbr a quick reference on disposal altematives for specific wastes see Table 4.1. SCL
REQUIREMENTS
• Costs (C:apital, O&M)
The retrofitting of existing fiieUng areas to minimize stonn water exposure or
spiU runo£f can be expensive. Good design must occur during tbe initial instaUa-
tion. Extruded curb along the "upstream" side of the fueling area to prevent
stonn water runon is of modest cost
• Mainlenance
CHean oil/water separators at the appropriate intervals.
Keep ample sui^Iies of spUl deanup materials on-site.
Inspect fueling areas and stcxage tanks on a regular schedule.
LIMITATIONS
• Oil/water separators are only as effective as their maintenance program.
Targeted Constituents
O Sediment
O Nutrients
% Heavy Metals
0 Toxic Materials
O Floatable Materials
O Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
• Ukely to Have
Significant Impact
O Proliable Low or Unknown Impact
Implementation
Requirements
Q Capital Costs
O O&M Costs
O Maintenance
O Training
High O Low
SC2
Best'
Management"^
Practices>
Industrial Handbook 4-11 March, 1993
Additional Information — vehicle and Equipment Fueling
SpiUs from fueling or from tbe transfer of fuels to the slorage tank can be a significant source of poUution. Fuels carry
contaminants of particular concem to humans and wUdUfe, such as heavy metals, tojcic materials, and oil and grease,
which are not easUy removed by storm water treatment devices. Consequentiy, control at the source is particularly
important. Adequate control can be achieved with careful design of tbe irutial installation, retrofitting of existing
instaUations, and proper spiU cootrol and cleanup procedures, as described bdow.
Design
Witii new installations, design tbe fueling area to prevent die runon of storm water and die runo£f of spills. This can be
achieved by contouring tbe site in tbe apixopriate fashion. Covering tiie site is tiie best approach but may not be feasible
if very large mobile equipment is being fueled. Storm water runon can lie diverted around tiie fueling area by an extruded
curb or with a "speed bump", if vehicle access is needed from this direction. SpiUs can be contained within the fiieling
area eitiier by using a perimeter drain or by sloping the pavement inward witii drainage to a sump. In both cases tiie
drain can be connected to the storm drain with a valve that is only closed during fueling operations and left open at aU
other times. Pave tiie fuding area witii Portland cement concrete rather than asphalt, since the latter wUl gradually
disintegrate and be washed from the site.
Snill Contml
Tbe foUowing spiU control measures wUl reduce spilling or reduce tiie loss of spiUed fuels fircHn tbe site:
• InstaU vapOT recovery nozzles.
Do not "top ofr tanks.
• Place secondary containment aiound tiie fuel truck when it is transferring fuel to the slorage tank. The truck
operator should remain with the tmck whUe the transfer is in progress.
• Place a stockpile of ^iU deanup materials where it wiU be readUy accessible.
• Use dry methods to clean the fueling area whenever possible. If you periodicaUy clean by pressure washing, place a
tempcvaiy plug in tbe downstieam drain and pump out tbe accumulated water. Properiy dispose the water.
Train employees on proper fiieling and deanup pnxedures.
DesinifUetl Ana
If your faciUty has large nimibers of mobUe equipment working throughout the site and you cunentiy fuel them with a
mobUe fuel truck, consider estabUshing a designated area for fueUng. With the exception of tracked equipment such as
buUdozers and perhaps smaU forklifts, most vehides sbodd be able to travd to a designated area witii Utile lost time.
Place temporary "caps" over nearby catch basins or manbole covers so that if a spiU occurs it is prevented firom entering
tbe storm drain.
ExnmnlCT nf Fffcirtive Pm<>Tani<;
Tbe SpiU Prevention Control and Countermeasure (SPCQ Plan, which is required by law for some facUities, is an
effective program to reduce tbe number of accidental ^Uls.
• The Citv of Palo Alio has an effective program for commerdal vehicle service fiacUities. Many of tbe program's
elements, including specific BMP guidance and lists of equipment suppUers, are also applicable to industrial
faciUties.
REFERENCES
Best Management Practices for Automotive-Related Industiies, Santa (Tiara Valley Nonpoint Source Pollutkin Control
Program, 1992.
Best Management Practices for Industrial S torm Water Pollution Control, Santa Clara
VaUey Nonpoint Source PoUutioa Controi Program, 1992.
Stotm Water Managemenl for Industrial Activities: Developing Pollution Prevention Plans, and Best
Managemenl Practices, EPA 832-R-92-006, USEPA, 1992.
Water QuaUty Best Managemenl Practices Manual, City of Seattie, 1989.
Industrial Handbook 4-12 March, 1993
ACTIVITY: VEHICLE AND EQUIPMENT WASHING & STEAM CLEANING
»-T0SUMP
Applications
Manufacturing
Material Handling
C^hicle Maintenance^
fOnstrucUon
(Commercial Activities^
Roadways
Waste Containment
^housekeeping Practic^^
DESCRIPTION
Prevent or reduce tbe discharge of poUutants to stonn water from vehicle and equipment
washing and steam cleaning.
APPROACH
• Consider off-site commercial washing and steam cleaiung businesses.
• Use designated wash areas, preferably covered to prevent contact with storm water
and bermed to contain wash water.
• Discharge wash water to saiutary sewer, after contacting local sewer autiiority to find
out if pretreatment is required.
• Educate empioyees on poUution prevention measures.
• Consider fUtering and recycUng wash water.
• Do not pemut steam deaning wash water to enter the storm draiiL
• For a quick reference on disposal alternatives for specific wastes see Table 4.1, SCI.
REQUIREMENTS
• Capital costs vary depending on measures implemented.
Low cosl ($500-1,000) for berm constraction.
Medium cost ($S,000-20,(X)0) for plumbing modifications (induding re-routing
discharge to sanitary sewer and instaUing simple sump).
- High cost ($30,000-150,000) for on-site treatment and recycUng.
• O&M costs increase witiii increasing capital investmenL
• Maintenance
Bexm repair and patching.
Inspection and maintenance of sumps, oil/water separators, and on-site treatment/
recyding units.
LIMITATIONS
• Some munidpaUties may require pretreatment and moiutoring of wash water dis-
charges to tiie sanitary sewer.
• Steam cleaning can generate significant poUutant concentrations requiring permitting,
monitoring, pretreatment, and inspections. The measures outlined in this fact sheet
are insufficient to address aU tbe environmental impacts and compliance issues related
to steam cleaning.
Targeted Constituents
% Sediment
9 Nutrients
9 Heavy Metals
% Toxic Materials
O Float^le Materials
% Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
W Ukely to Have
Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
Q Capital Costs
O O&M Costs
O Maintenance
O Training
High O Low
SC3
Best'
Management^
Practices'*
Industrial Handbook 4-13 March, 1993
Additional Information — Vehicle and Equipment Washing and Steam Cleaning
Washing vehicles and equipment outdoors or in areas wbere wash water flows onto the ground can pollute storm water.
If your faciUty washes or steam cleans a large number of vehicles or pieces of equipment, consider contracting out tiiis
work to a commeicial business. These businesses are better equipped to handle and dispose of tbe wash waters properly.
Contracting oul tiiis work can also be economical by eliminating the need for a separate washing/cleaning operation at
your faciUty.
If washing/cleaning must occur on-site, consider washing vehicles inside tiie buUding to control tiie targeted constituents
by directing tiiem to tbe sanitaiy sewer where they can be pretreated or sent directiy to tbe sanitaiy treatment faciUty.
Washing operations outside should be conducted in a designated wa^ aiea having the following characteristics:
• Paved with Portland cement concrete,
• Covered or bermed to prevent contact with storm water,
• Sloped for wash water coUection, ^
• Discharges wash water to the sanitary or process waste sewer, or to a dead-end sump. Discharge pipe should have a
positive control valve that allows switching between the storm drain and sanitary or process sewer,
• Clearly designated, and
• Equipped witb-an oil/water separator (see Chapter 5, TC7, OU/Water Separators and Water QuaUty Inlets).
Exampte nf Effective Pmyrams
The City of Palo Alto has an effective program for commercial vehide service fadUties. Many of tbe program's
elements, including specific BMP guidance and lists of equipment suppliers, are appUcable to industrial vehicle service
faciUties.
The U.S. Postal Service in West Sacramenio has a new vehide wash system that collects, fUters, and recycles tiie wash
water.
REFERENCES
Besl Management Practices for Automotive-Related Industries, Santa CHara VaUey Nonpoint Source PoUution Control
Program, 1992.
Best Managemenl Practices for Industiial Storm Watet PoUution Control, Santa (Tiara VaUey Nonpoint Source PoUution
Control Program, 1992.
Storm Water Managemenl for Industiial Activities: Developing PoUutioa Invention Plans, and Best Management
Practices, EPA 8320R-92-006, USEPA, 1992.
Water QuaUty Besl Management Practices Manual, City of Seattie, 1989.
Industrial Handbook 4-14 March, 1993
ACTIVITY: VEHICLE AND EQUIPMENT MAINTENANCE AND REPAIR
DIKE TO PREVENT
SPILLS/LEAKS
FROM ENTERING
STDRM DRAIN
J^aterial Handline
JVehicle Maintenance!.
.Construction,
jCommercial Activities^
Roadways
Waste Containment
C^^ousekeeping Practi^s^
Appiications
Manufacturing
DESCnUPTION ;
Prevent or reduce the discbarge of poUutants to storm water from vehide and equipment
maintenance and repair by mnning a dry shop.
APPROACH
• Keep equipment clean, don't allow excessive buUd-up of dl and grease.
• Keep drip pans or containers under the areas that might drip.
• Do not change motor oil or perform equipment maintenance in non-appropriate areas.
Use a vehicle maintenance area designed to prevent stotm water pollution.
• Inspect equipment for leaks on a regular basis.
• Segregate wastes.
• Make sure oU filters are c(»npletely drained and crashed before recycling or disposal..
• Make sure incoming vehicles are checked for leaking oU and fluids.
• Clean yard storm drain inlets(s) regulariy and especiaUy after large stonns.
• Do not pour materials down dr^ns or hose down woric areas; use dry sweeping.
• Store idle equipment under cover.
• Drain aU fluids from wrecked vehicles.
• Recycle greases, used oU or oU fUters. antifreeze, cleaning solutions, automotive
batteries, hydrauUc, and transmission fluids.
• Switch to non-toxic chemicals for maintenance when possible.
• Clean smaU spUls witb rags, general clean-up with damp mops and larger spUls with
absorbent material.
• Paint signs on slorm drain inlets to indicate that they are not to receive Uquid or soUd
wastes.
• Train employees.
• Minimize use of solvents.
• For a quick reference on disposal alternatives for spedfic wastes see Table 4.1, SCI.
REQUIREMENTS
Costs (Capital, O&M) - Should be low, bul wUl vary depending on die size of the
faciUty.
• Maintenance - Should be low if procedures for the approach are foUowed.
LIMITATIONS
• Space and time Umitations may preclude aU work bdng conducted indoors.
• It may not be possible to contain and dean up S{H1IS frtxa vehides/equipment brought
on-site after working hours.
• Drain pans (usuaUy 1 ft. x 1 ft) are generally too smaU to contain antifreeze, which
may gush firom some vehicles, so drill pans (3 fL x 3 fL) may have to be purchased or
fabricated.
• Dry floor cleaning methods may not be suffident for some spUls. Use three-step
method instead.
• Identification of engine leaks may require some use of solvents.
Targeted Constituents
O Sediment
O Nutrients
% Heavy Metals
% Toxic Materials
O Floatable Materials
O Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
• Ukely to Have Significant Impact
O Probable Low or
Unknown Impaci
Implementation
Requirements
O Capital Costs
Q O&M Costs
Q Maintenance
O Training
High O Low
SC4
Best'
Management
Practices>
Industrial Handbook 4 -15 March, 1993
Additional Information — VeWcIe and Equipment Maintenance and Repair
Vehicle or equipment mainlenance is a potentiaUy significant source of storm water poUution. Activities that can
contaminate storm water include engine repair and service (parts cleaning, spiUed fuel, oU, etc.), replacement of fluids,
and outdcKV equipment storage and parking (dripping engines). For furtiier infonnation on vehicle or equipment
servidng, sec SC2, Vehicle and Equipment FueUng, and SC3, Vehicle and Equipment Washing and Steam Qeaning.
Waste Rednction
Parts are often cleaned using solvents such as tiichloroetiiylene, l.l.l-tricbloroethane or methylene chloride. Many of
tiiese deaners are hannful and must be diqiosed of as a hazaidous waste. Oeaning witiiout using Uquid cleaners (e.g.
wire brush) whenever possible reduces waste. Prevent spUls and drips of solvents and deansers to tiie shop floor. Do aU
Uquid deaning al a centralized station so die solvents and residues stay in one area. Locate drip pans, drain boards, and
diying racks to direct drips back into a solvent sink or fluid holding tank for re-use.
«
Safer Altematives
If possible, eliminate ot reduce tbe amount of hazardous materials and waste by substituting non-hazardous or less
hazardous materials. For example:
Use non-caustic detergents instead of caustic cleaning agenU for parts cleaning (ask your suppUer aboul alternative
cleaning agents).
• Use detergent-based or water-based cleaning systems in place of organic solvent degreasers. Wash water may
require tieattnent befwe it can be discharged to the sewer. Contaa your local sewer autbority for more information.
• Replace chlorinated organic solvents (1,1,1-uichloroediane, metiiylene chloride, etc.) with non-chlorinated solvents.
Non-chlorinated solvents like kerosene or mineral spirits are less toxic and less expensive to dispose of prc^rly.
Check list of active ingredients to sec whether il contains chlorinated solvents. The "chlor^ term indicates tiiat the
solvent is chlorinated.
• (Tboose cleaning agents that can be recycled. /-
• Contact your suppUer or refer to trade journals for more waste minimization ideas.
Redudng the number of scdvents makes recycling easier and reduces hazardous waste management costs. Often, one
solvent can perfonn a job as weU as two different solvents.
Recycling
Separating wastes aUows for easier recycling and may reduce treatment costs. Keep hazardous and non-hazardous
wastes separate, do not mix used oU and solvents, and keep cblorinated solvents (like 1,1,1-tiichloroctiiane) separate
firom noa-chlorinated solvents (like kerosene and mineral spirits).
Many products made of recycled (Le., refined or purified) materials are available. Engine oU, transmission fluid,
antifreeze, and hydrauUc fluid are available in recycled form. Buying recycled products supports the market for recyded
materials.
Spill Lgflk nean Up
Clean leaks, drips, and other spills witii as Uttie water as possible. Use rags for small spills, a damp mop for general
cleanup, and dry absorbeitt material for larger spiUs. Use the foUowing tiiree-step metiiod for cleaning floors:
1. Clean ^ills witii rags oc other absorbent materials.
2. Sweep floc»- using diy absorbent materiaL
3. Mop floor. Mop water may be discharged to tiie sanitary sewer via a toUet or sink.
Industrial Handbook 4-16 March, 1993
Additional Information — VeWcIe and Equipment Maintenance and Repair
Good Housekeeping
Also consider the foUowing measures:
• Avoid hosing down your work areas. If work areas are washed, direct wash water to sanitaiy sewer.
• CoUect leaking or dripping fluids in drip pans or containers. Fluids are easier to recycle if kept separate.
• Keep a drip pan under tbe vehide while you uncUp hoses, unscrew fUters, or remove other parts. Use a drip pan
under any vehicle that might leak while you work on it to keep splatters or drips off tiie shop floor.
• Promptiy transfer used fluids to the proper waste or recycling drums. Don't leave fuU drip pans or other open
containers lying around.
Do not pour Uquid waste to floor drains, sinks, outdoor storm drain inlets, or other storm drains or sewer connections.
Used or leftover cleaning solutions, solvents, and automotive fluids and oU are toxic and should not be put in the sanitary
sewer. Post signs al sinks to renund employees, and paint stencils at outdoor drains to teU customer and others not to
pour wastes down drains.
OU filters disposed of in trash cans or dumpsters can leak oU and contaminate storm water. Most munidpaUties prohibit
or discourage disposal of these items in soUd waste faciUties. Place the oU filter in a funnel over the waste oU recycUng
or disposal collection tank to drain excess oU before disposal. OU fUters can be crashed and recycled. Ask your oU
supplier or recycler aboul recyding oU filters.
Put pans under leaks to colled fluids for proper recycling or disposaL Keeping leaks off die ground reduces tiie potential
for stotm water contamination and reduces cleanup time and costs. If tbe vehicle or equipment is to be stored outdocHS,
oU and otiier fluids should be drained first
Designate a special area to drain and replace motor oU, coolant, and other fluids, where there are no connections to the
suirm drain or the sanitary sewer and drips and spiUs can be easUy cleaned up.
Be especially careful with wrecked vehicles, whether you keep tiiem indoors or out, as weU as vehicles kept on-site for
scrap or salvage. Wrecked or dainaged vehicles often drip oU and other fluids for several days.
• As the vehicles arrive, place drip pans under tiiem immediately, even if you beUeve that the fluids have leaked out
before die car reaches your shop.
• BuUd a shed or lemporary roof over areas where you park cars awaiting repair or salvage, especially if you handle
wrecked vehicles. BuUd a roof over vehicles you keep for parts.
Drain aU fluids, induding air conditioner coolant, from wrecked vehides and "part" cars. Also drain engines,
transmission, and other used parts.
• Store cracked batteries in a non-leaking secondary container. Do tbis with aU cracked batteries, even if you think aU
tbe add has drained out If you drop a battery, ti-eat it as if it is cracked. Put it into die containment area until you
are sure it is not leaking.
Examples of Effective Programs
The City of Palo Alto has an effective program for commerdal vehicle service fiidlities. Many of tiie program's
elements, including specific BMP guidance and lists of equipmeni suppliers, are also appUcable to industrial vehicle
service fadUties.
Pick N PuU Auto Dismantiers in Rancho Cixdova drains all fluids fix>m automobUes before they enter tbe yard.
Ecology Auto Wrecking in Rialto is sunounded by a steel plate/concrete fence and bas a completely paved lol tbat is
graded to a central low point CoUected storm water is channeled tiirougb as underground drainage system of clarifiers
Industrial Handbook 4-17 March, 1993
Additional Infomiation — Vehicle and Equipment Maintenance and Repair
and tiien stored in a 60,000 gaUon UST before being processed tiirough a fUter system. In addition, tiie work area is
covered, ventilated and has an additional sump. Vehicle fluids are drained in this area and segregated for recycling.
AU Auto Parts, Fontana, has a complete water recycling system in a 10,000 square fool concrete slab surrounded by a
curb that contains aU the runoff and sends il to tbe recycling system. AU receiving, dismantiing, and shipping occurs on
the slab.
REFERENCES
Best Management Practices for Automotive-Related Industties, Santa Clara Valley Nonpoint Source PoUution Control
PTBgram, 1992.
BeslManagentent Practices for ConboUing OU and Grease in Urban Storm Water Runoff, G. S. Silverman, et al, 1986
Environmental Professional, VoL 8, pp 351-362.*
Best Management Piacticcs for Industrial Storm Water PoUutioa Control, Santa Clara VaUey Nonpoint Source PoUutioa
Control Program, 1992.
Faa Sheet - Waste Reduction for Automotive Repair Shops; DTSC, 1989.
Hazardous Waste Reduction Assessment Handbook - Automotive Repair Shops; DTSC, 1988.
Hazardous Waste Reduction Cheddist - Automotive Repair Shops; DTSC, 1988.
Storm Water Managemenl for Industtial Activities: Developing Pdlution Prevention Plans, and Best Managentent
Practices, EPA 832-R-92-006, USEPA, 1992.
Industrial Handbook 4-18 March, 1993
ACTIVITY: OUTDOOR LOADING/UNLOADING OF MATERIALS Applications
Manufacturing
^^^^Material HandUncT^
Vehicle Maintenance
instruction^
Commercial Activities'^
Roadways
Waste Containment
^housekeeping Practic^^
DESCRIPTION
Prevent or reduce tbe discbarge of poUutants to storm water firom outdoor loading/
uiUoading of materials.
APPROACH
• Park tank tiucks or deUvery vehicles so that spills or leaks can be contained.
• Cover die loading/uiUoading docks to reduce exposure of materials to rain.
• Seal ot door skirt between traUer and buUding can also prevent exposure to rain.
• Design loadmg/unloading area to prevent storm water runon:
grading or berming, and
position roof downspouts to direa storm water away from loading/unloading
areas.
• Contain leaks during transfer.
• Use drip pans under hoses.
• Make sure fork lift operators are propeily trained.
• Employee training for spill containment and cleanup.
REQUIREMENTS
• Costs (Coital, O&M) - Should be tow except when covering a large loading/unload-
ing area.
• Maintenance
Conduct regular inspections and make repairs as necessaiy. The frequency of
repairs wiU depend on tiie age of the fadlity.
Check kiading and unloading equipment regularly for leaks:
valves,
pumps,
flanges, and
connections.
LIMITATIONS
• Space and time limitations may preclude all transfers from being performed indoors or
undercover.
• It may not be possible to conduct tiansfers only during dry weather.
Targeted Constituents
O Sediment
0 Nutrients
# Heavy Metals
% Toxic Materials
9 Fhatable Materials
0 Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
9 Ukely to Have ignificant Impact
O Probable Low or
Unknown Impact
Impiementati'on
Requirements
Q Capital Costs
O O&M Costs
O Maintenance
Q Training
High O Low
SCS
Best'
Management
Practices^
Industrial Handbook 4 -19 March, 1993
Additional Information — outdoor Loading/Unloadlng of Materials
The loading/unloading of materials usuaUy takes place outside. Loading or unloading of materials occurs in two ways:
materials in containers or direa Uquid transfer. Materials spiUed, leaked or lost during loading/unloading may coUea in
the soil or on otber surfaces and bc canied away by mnoff or when die area is deaned. RainfaU may wash poUutants
from machinery used to unload or move materials. The loading or unloading may involve rail or ttuck ttansfer.
The most important faaors in preventing these constituents from entering storm water is:
• Linut exposure of material to rainfall
• Prevent storm water mnon.
• (Theck equipmeni regulariy for leaks.
• Contain spills during tiansfer operations.
Loading or uiUoading of Uquids should occur in the manufacturing building so that any spills that are nol completely
retained can be discharged to the sanitary sewer, treatment plant or treated in a inanner consistent with local sewer
authorities and pennil requirements. Best management practices indude:
Use overhangs or door skirts tiiat enclose die trailer.
Park tank tracks during deUveiy so that spUls ote leaks can bc contained.
DesignJoading/uiUoading area to prevent storm water mnon which would include grading or berming the area, and
positioning roof downspouts so tiiey direa storm water away frran the loading/unloading areas.
Check loading and unloading equipment regularly for leaks, including valves, pumps, flanges and connections.
Look for dust or fumes during loading or unloading operations.
Use a written tqierations plan tiiat describes procedures for loading and/or unloading.
Have an emergency spiU cleanup plan reacUly avaUable.
Employees ttained in spUl containment and cleanup should be present during the loading/unloading.
Establish depots of cleanup materials next to or near each loading/uiUoading area, and train employees in their use.
FOT loading and unloadmg tank tracks to above and below ground storage tanks, the foUowing procedures should be
used.
The area where the transfer takes place should be paved. If the Uquid is reactive with tiie asphalt Portland
cement should be used to pave tiie area.
Transfer area should bc designed to prevent mnon of storm water from adjacent areas. Sloping thc pad and
using a curb, like a speed bump, around tiic uphill side of the transfer area should reduce mnon.
- Transfer area should be designed to prevent mnoff of spiUed Uquids firom tiie area. Slopmg die area to a drain
should prevent mnoff. The drain should be connected to a dead-end sump or to die sanitary sewer. A positive
control valve should be instaUed oa tbe drain.
• FOT tiansfer firom raU cars to storage tanks dial must occur outside, use tiie foltowing procedures:
Drip pans should be placed at kications where spUlage may occur, such as hose connections, hose reels, and
fUIer nozzles. Use drip pans when making and breaking connections.
Drip pan systems should be instaUed between tbe rails to coUect spUlage from tank cars.
REFERENCES
Best Management Practices for Industrial Storm Water PoUution Contttjl, Santa Clara VaUey Nonpoint Source Pollution
Control Program, 1992
Storm Water Managemenl for Industrial Activities: Developing Pollution Prevention Plans, and Best Management
Practices, EPA 832-R-92-006, USEPA, 1992.
Water QuaUty Best Management Practices Manual City of Seattle, 1989.
Industrial Handbook 4-20 March, 1993
ACTIVITY: OUTDOOR CONTAINER STORAGE OF UQUIDS
COVER TO MINIMIZE STORM WATER
DIKE TO CONTAIN
SPIttS/STORM WATER
Applications
Manufacturing
Vehhie Maintenance
^Commercial ActivH^^
Roadways
Waste Containment
(housekeeping Practic^^
DESCRIPTION ,
Prevent OT reduce tbe disdiarge of poUutants to storm water from outdoor container storage
areas by instaUing safeguards against acddental releases, installing secondary containment
conducting regular inspections, and training employees in standard operating procedures
and SpiU cleanup techiuques.
APPROACH
• Protect materials fiom rainfall mnon, ranoff, and wind dispersal:
SlOTC materials indoors.
Cover the storage area witii a roof.
Minize storm water nmon by enclosing tiie area or buiding a berm around it
Use "doghouse" for storage of Uquid containers.
Use covered dumpsteis fOT waste |»odua containers.
• Storage of oU and hazardous materials must meet spedfic Federal and State standards
including:
SpiU Prevention Control and Countermeasure Plan (SPCC) Plan,
secondary containment
integrity and leak detection monitoring, and
emergency preparedness plans.
• Train operator on proper storage.
• Safeguards against acddental releases:
overflow protection devices to wam operator or automatic shut down transfer
pumps,
protection guards (bollards) around tanks and piping to prevent vehicle or forkUft
damage, and
clear tagging OT labeUng, and restricting access to valves to reduce human error.
• Berm or surround tank or container with seamdary containment system:
dUces, Uners, vaults, OT double waUed tanks.
• Some municipalities require that secondary containment areas be connected to
tiie sanitary sewer, prohibiting any hard connections to the stonn drain.
• FadUties witii "spUl ponds" designed to intercept tteat and/OT divert spiUs
should contaa the appropriate regulatory agency regarding envirinmeiital
compliance.
REQUIREMENTS
• Cost (Capital, O&M)
WiU vary depending on tbe size of tiie faciUty and die necessary controls.
• Maintenance: Condua routine weekly inspections.
LIMITATIONS
• Storage sheds often must meel buUding and fire code requirements.
Targeted Constituents
O Sediment
O Nutrients
% Heavy Metals
0 Toxic Materials
O Fhatable Materials
% Oxygen Demand-
ing Substances
O Oil & Grease
O Bacteria & Viruses
W Ukely to Have
Significant Impact
o Probable Low or
Unknown Impact
implementation
Requirements
O Capital Costs
Q O&M Costs
O Maintenance
O Training
High O Low
SCB
Best'
Management
Practices'*
Industrial Handbook 4-21 March, 1993
Additional Information — outdoor container storage of Uquids
Acddental releases of materials irota aboveground Uquid storage tanks, drums, and dumpsters present the poten-
tial fOT contaminating storm waters witii many different poUutants. Materials spilled, leaked OT lost from storage
containers and dumpsters may accumulate in soils or on the siufaces and be canied away by storm water ranoff.
Tbese source controls apply to containers located outside of a buUding used to temporarUy store Uquid materials.
It should be noted tbat the storage of reactive, ignitable, or flammable liquids must comply witii fire codes.
Container Management
To limit tiie possibUity of storm water poUution, containers us«l to store dangerous waste or otiier Uquids should
bc kq>t inside tiie buUding imless this is impractical due to site constraints. If the containers are placed outside, tiie
foUowing procedures shotUd be employed:
• Dumpsters used to store items awaiting transfer to a landfiU should be placed in a lean-to stmcture or other-
wise covered, dumpsters shaU bc kept in good condition without corrosion or leaky seams.
• (jarbage dumpsters shaU be replaced if tiicy'are deteriorating to die point wbere leakage is occurring. It
shoukl be kept undercover to iMcvent the entry of storm water. Employees should bc made aware of the
importance of keeping tbe dumpsters covered and firee from leaks.
• A fillet should J)e placed on both sides of the curb to CaciUtate moving tiie dumpster.
• Waste container drums should be kept in an area such as a service bay. If drums are kept outside, tbey musl
bc stored in a lean-to type stmcture, shed or walk-in container to keep rainfaU from readiing tiie drums.
Storage of reactive, igiutible, or flammable Uquids must comply with the fire codes of your area. Practices listed
below should be employed to enhance tbe fire code requirements.
• Containers should be placed in a designated area.
• Designated areas should be paved, free of cracks and gaps, and impervious in order to contain leaks and spUls.
• Liquid waste should be surrounded by a curb OT dike to provide tbe voluote to contain 10 percent of the
volume of all of die containers OT 110 percent of the volume of tiie largest container, whichever is greater.
• Tbe area inside die curb should slope to a drain.
FOT used oil OT dangerous waste, a dead-end sump should be instaUed in the drain.
AU other Uquids should be drained to tbe sanitary sewer if available. Tbe drain musl have a positive control
such as a tock, valve, or plug to prevent release of contaminated Uquids.
• The designated slorage area should be covered.
• Containers used fOT Uquid removal by an employees musl be placed in a containment area.
A drip pan should be used at aU times.
• Drams stored in an area where unauthorized persons may gain access musl be secured to prevent acddental spillage,
pUferage, OT any unauthorized use.
• Employees trained in emergency spUl deanup procedures should be present when dangerous waste, Uquid chcoucals,
or other wastes are loaded or unloaded.
The most common causes of unintentional releases:
• External corrosion and stractural failure,
• Installation problems,
• Spills and overfUls due to operator errOT,
• FaUure of piping systems (pipes, pumps, flanges, coupUngs, hoses, and valves), and
• Leaks during pumping of Uquids or gases from track or railcar to a storage fadUty or vice versa.
Operator Training/Safeouards
WeU-ttained employees can reduce human errors dial lead to acddental releases or spiUs. Employees should be familiar
witii the SpiU Prevention Control and Countermeasure Plan. The employee should have the tools and knowledge to
Industrial Handbook 4-22 March, 1993
Additional Information — outdoor container storage of Uquids
immediately begin deaning up a spiU if one should occur. Operator errors can be prevented by using engineering safe
guards and tiius redudng accidental releases of poUutant Safeguards include:
• Overflow proteaion devices on tank systems to wam tbe operator to automatically shutdown transfer pumps when
tbe tank reaches fuU capadty,
• Protective guards (bollards) around tanks and piping to prevent vehicle or forkUft damage, and
• Clearly tagging or labeling aU valves to reduce human error.
Tank systems should be inspected and tank integrity tested regulariy. Problem areas can often be detected by visually
inspecting the tanks firequentiy. Problems or potential problems should be corrected as soon as possible. Registered and
spedfically trained professional engineers can identify and correct potential problems such as loose fittings, poor welding,
and improper or poOTly fitted gaskets fOT newly instaUed tank systems. The tank foundations, connections, coatings, and
tank waUs and piping systems also should be inspected. Inspection for corrosion, leaks, cracks, scrauAes in protective
coatings, or otiier physical damage tbat may Weaken the tank system should be a part of regular integrity testing.
Secondary Containment
Tanks should be bermed OT surrounded by a secondary containment system. Leaks can be detected more easily and spills
can be contained when a secondary containment systems arc installed. Berms, dikes, liners, vaults, and double-wall tanks
are examples of secondary containment systems.
One of tbe best protective measures against contamination of storm water is diking. Containment dikes are benns or
retaining walls dial are designed to bold spills. DUdng is an effective pollution prevention measure for above ground
storage tanks and railcar OT tank track loading and unloading areas. Tbe dike surrounds the area of concem and holds the
SpUl, keeping spiU materials separated firom tiie storm water side of die dike area. DUdng can lie used in any industtial
fadUty, but it is most commonly used for controlling large spiUs or releases firom Uquid storage areas and Uquid transfer
areas.
Fbr single-wall tanks, containment dikes should be large enough to hold the contents of tbe storage tank for die fadUty
plus rain water. For trucks, diked areas should be capable of holding an amount equal to die volume of the tank track
COTnpartment Diked constraction material should be strong enough to safely hold spiUed materials. Dike materials can
consist of earth, concrete, synthetic materials, metal or other impervious materials. Strong adds or bases may react witii
metal containers, concrete, and some plastics. Wbere strong adds or bases or stored, altemative dike nuilerials sbodd be
considered. More active organic chemicals may need certain special liners for dikes. Dikes may also bc designed witii
impermeable niaterials to increase containment capabiUties. DUces should be inspected during or after significant storms
or spills to check for washouts or overflows. Regular checks of containment dikes to insure tiiic dikes are capable of
holding SpUls should be conducted, InabiUty of a sttucttire to retain storm water, dike erosion, soggy areas, or changes in
vegetation indicate problems with dike stractures. Damaged areas should be patched and stabilized immediately. Earthen
dikes may require spedal maintenance of vegetation such as mulching and inigation.
Curbing is a banier that surrounds an area of concem. Curbing is »milar to containment diking in the way tiiat it prevents
spiUs and leaks firom being released into the environment The curbing is usually smaU scaled and does not contain large
spills Uke diking. Curbing is common at many faciUties in small areas where handling and transfer Uquid materials occur.
Curbing can redired contaminated stom water away firom tiic storage area. It is useful in areas wbere liquid materials are
tiansferred from one container to another. Asphalt is a common material used for curbing; however, curbing materials
include earth, concrete, synthetic materials, metal or other impenetrable materials. SpUled materials should be removed
'immediately from cuibed areas to allow space fOT future. spUls. Curbs shoukl have manuaUy-controlled pump systems
radicr tiian common drainage systems for coUection of spiUed materials. The curbed area should bc inspeaed regulariy to
clear clogging debris. Maintenance should also be conducted frequentiy to prevent overflow of any spilled materials as
curbed areas are designed only for smaller spills. Curbing has the following advantages:
• Excdlent runon conttol
Inexpensive,
• Ease of installment
Provkles option to recycle materials spUled in curb areas, and
• Common industty practice.
Industrial Handbook 4-23 March, 1993
Additional Information — Outdoor Container Storage of Uquids
MaintenanrB
• Weekly inspeaion should bc considered and indude:
Check for extemal corrosion and structural faUure,
Check fOT spiUs and overfills due to operator error.
Check for faUure of piping system (pipes, pumps, flanges, coupling, hoses, and valves).
Check fOT leaks or spills during pumping of Uquids or gases firom tmck or raU car to a storage faciUty or vice
versa,
VisuaUy inspea new taiUc or container installation loose fittings, poor welding, and improper or poOTly fitted
gaskets, and
Inqiea tank foundations, connections, coatings, and tank walls and piping system. Look fw corrosion, leaks,
cradcs, scratches, and other physical damage dial may weaken tiie ttmk or container system.
Examnles of EfTective Pmpram^ «
TTie "doghouse" design has been used to store smaU liquid containers. Tbe roof and flooring design prevent contaa witii
direa rain OT runoff. Tbe doghouse has two soUd stmctural walls and two canvas covered walls. "ITie flooring is wire
mesh about secondary containment TTie unit has been used successfuUy at Lockheed MissUe and Space Company in
Sunnyvale.
REFERENCES
Best Management Practices for Industtial Storm Water PoUution Conttol Santa Clara VaUey Nonpoint Source
PoUutkm Control Program, 1992.
Stonn Water Management for Industrial Activities: Developing PoUuticm Prevention Plans, and Best Management
Practices, EPA 832-R-92-006, USEPA, 1992.
Water (QuaUty Besl Management Practices Manual, City of Seattle, 1989.
Industrial Handbook 4-24 March, 1993
ACTIVITY" oi^ooR PROCESS EQUIPMENT OPERATIONS AND • MAINTENANCE
DIKE TO CONTAIN '
SPIU.SirSTORM WATER
Applications
C^^^anufacturing^^
Material Handling
Vehicle Maintenance
(C^pnstructioiT^
(Commercial Activit^l^
Roadways
Waste Containment
(^housekeeping Practices^
DESCRIPTION *
Prevent or reduce the discharge of poUutants to storm water frcna outdoor process equip-
ment operations and maintenance by redudng tbe amount of waste created, enclosing or
covering aU or some of die equipment installing secondary containment and ttaining
employees.
APPROACH
• Alter the activity to prevent exposure of poUutants to stonn water.
• Move activity indoors.
• Cover tbe area witii a permanent roof.
• Minimize contaa of stram water with outside manu&cturing operations through
berating and drainage routing (ran on prevention).
• Connea process equipmeni area to pubic sewer or faciUty wastewater treatment
system.
• Clean regularly thc storm drainage system.
• Use catch basin fUttation inserts (Chapter 5, TC6, Media Filtration) as a means to
capttire particulate poUutants.
• Some munidpaUties require that secondary containment areas (regardless of size) be
connected to tbe sanitary sewer, prohibiting any hard connections to die storm drain.
REQUIREMENTS
• Costs (Capital O&M)
Variable depending on the complexity of the operation and die amount of control
necessary for storm water poUution conttol..
• Maintenance
Routine preventive maintenance, including cheddng process equipment for
leaks.
LIMITATIONS
• Providing cover may be expensive.
• Space limitations may preclude enclosing some equipment
• Storage sheds often musl meet building and fire code requirements.
Targeted Constituents
9 Sediment
O Nutrients
# Heavy Metals
# Toxic Materials
O Floatabh Materials
O Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
# Ukely to Have
Significant Impact
o
Probable Low or
Unknown Impact Implementation
Requirements
# Capital Costs
Q O&M Costs
O Maintenance
O Training
High O Low
SC7
Best'
Management
Practices'"
Industrial Handbook 4-25 March, 1993
Additional Information — Outdoor Process Equipment Operations and Maintenance
Outside process equipment operations can contaminate storm water ranoff. Activities, such as rock grinding OT cmsh-
ing, painting or coating, grinding or sanding, degreasing or parts cleaning, landfiUs, waste piles, wastewater and solid
waste treattnent and disposal, and land appUcation are process operations that use hazardous materials and lhat can lead
to contamination of storm water ranoff. PoUutants firom the wastewater and soUd waste tteatinent and disposal areas
result from waste pumping, additions of treatment chemicals, mbung, aeration, clarification, and soUds dewatering.
Possible Storm water contaminants inciude heavy metals, toxic materials, and oU and grease. Waste spiUed. leaked, OT
lost from outdOOT process equipment operations may buUd up in soils OT on otiier surfaces and bc carried away by storm
water ranoff. There is also a potential fOT Uquid waste firtxn lagoons or surface impoundments, associated with outtloor
equipment operations, to overflow to surface waters or soak the soU, which can be picked up by storm water runoff.
Tlic preferred (and possibly the most economical) action to reduce stonn water poUution is to alter tiie nature of activity
such that poUutants are not exposed to storm water. This may mean perfoming the activity during dry periods only or
substituting benign materials TOT more toxic ones. Actions otber than altering the activity include enclosing the activity
in a building and connecting the floOT drains to thc sanitary sewer. Tbe area used by the activity may bc so greal as to
make cndosure prohibitively expensive. BuUding cost can bc reduced by not covering the sides, and thus elinunating
the need fOT ventilating and Ughting systems. When certain parts of thc activity are the worst source of poUutants, those
parts can bc segregated and endosed or covered.
Curls can be placed around tbe immediate boundaries of tiie process equipment Tbe storm drains from tbese interiOT
areas can be connected to the fiadlity's process wastewater systenu
Reducing die amount of waste that is created and consequentiy tbe amount tiiat must be slOTcd or treated is anodier way
to reduce the potential for storm water contamination firom outside manufacturing activities. Waste reduction BMPs are
available for a wide range of industries and are designed to provide ideas and ways to reduce waste (see References).
Hvdranlic/Treatment Mndifiratinn';
If storm water becomes poUuted, it should be capoired and ureated. If you do not have your own process wastewater
treatment system, consider discharging to the public sewer system. Use of the public sewer might be allowed under the
foUowing conditions:
• If the activity area is very smaU Oess than a few hundred square feet), thc local sewer autiiority may bc wiUing to
aUow tbe area to remain uncovered with die drain connected to die public sewer.
* It may be possible under unusual circumstances to connea a much larger area to thc public sewer, as long as the rate
of storm water discharges do not exceed tiie capadty of tiie wastewater treattnent plant Thc storm water could be
slOTed during the storm and then tiansferred to the pubUc sewer when the nonnal flow is low, such as at night
Thc majority of the poUutants in storm water are discharged over time by die small high frequency storms. Less
poUuted runoff from tbe infrequent large stt>rms can bc bypassed to the storm drain. To implement tiiis BMP. a hydrau-
lic evaluation of thc downstream sewer system should occur in consultation with tiic local sewer autitority.
Industries that generate large volumes of process wastewater typicaUy have their own treattnent system that discharges
directiy to tiie nearest receiving water. These mdustries have die discretion to use tiieir wastewater tteatment system to
treat storm water within dlie constraints of their permit requirements for prcicess treattnent It may also be possible for
tbe industty to discbarge die storm water directiy to its effluent outfaU without treattnent as long as tiie total kiading of
die discharged process water and storm water docs not exceed tbe loading had a stonn water treatment device been used.
This could be jM±icved by redudng thc loading from die process wastewater treatment system. Check witii your Re-
gkmal Water Quality Control Board, as tiiis option would be subjea to permit constraints and potentiaUy regular
monitoring.
Industrial Handbook 4-26 March, 1993
Additional Information — outdoor process Equipment Operations and Maintenance
REFERENCES
Best Management Practices for Industrial Storm Water PoUution Conttxjl Santa Clara VaUey Nonpoint Source PoUution
Control Program, 1992.
PubUcattons That Can Work For You]; (Talifomia Department of Toxic Substances Control Saaamento, CA 1991 (A
Ust and OTder foim fOT waste minimization pubUcatioas fimn the State).
Stonn Water Management for Industrial Activities: Developing PoUution Prevention Plans, and Best Management
Practices, EPA 832-R-92-006, USEPA, 1992.
Water (QuaUty Best Managemenl Practices Manual City of Seattle, 1989.
Industrial Handbook 4-27 March, 1993
ACTIVITY' OUTDOOR STORAGE OF RAW MATERIALS, PRODUCTS,
AND BY- PRODUCTS
Applications
Manufacturing
C^^ter'ial Handling^
Vehhie Maintenance
.Construction
'Commercial Activities"
Roadways
Waste Containment
(housekeeping Practic^^
DESCRIPTION *
Prevent or reduce the discharge of poUutants to siOTm water from outdoor material and
inoduct storage areas by endosing or covering materials, mstalling secondary contain-
ment and preventing storm water runon.
APPROACH
• Protea materials from rainfall nmon, mnoff and wind di^iersak
Store material indoors.
Cover the storage area witii a roof.
Cover tbe material with a temporary covering made of polyetiiylene, polypro-
pylene, or hypalon.
Minimize storm water runon by enclosing tbe area or buUding a berm around the
area.
Use "doghouse" for sttjrage of Uquid containers.
• Parking lots or otiier surfaces near bulk materials storage areas should be swept
periodically to remove debris blown OT washed from storage area.
• InstaU peUet traps at storm water discharge points where plastic peUets are loaded and
unloaded. ^
• Keep Uquids in a designated area on a paved impervious surface witiiin a secondary
containment
• Keep outdoor storage containers in good condition.
• Use benns and curbing.
• Use cau± basin fUttation inserts (Ch^ter 5, TC6, Media FUttation)
REQUIREMENTS
• Costs (Coital, O&M)
Costs should be low except wbere large areas may have to be covered.
• Maintenance
Berm and curbing repair and patehing.
LIMITATIONS
• Space Umitations may preclude storing some materials indoors.
• Some munidpalities require tbat secondary containment areas (regardless of size) bc
connected to the sanitary sewer, prohibiting any hard connections to tiie storm drain.
• Storage sheds often musl meet building and fire code requtrements.
Targeted Constituents
9 Sediment
O Nutrients
# Heavy Metals
# Toxh Materials
0 Fhatable Materials
O Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
• Ukely to Have
Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
Q Capital Costs
O O&M Costs
O Maintenance
Training
High O Low
SCS
Best'
Management^
Practices^
Industrial Handbook 4-28 March, 1993
Additional Information — Outdoor Storage of Raw Materials, Products, and By-Products
Raw materials, by-products, finished products, containers, and material storage areas exposed to rain and/or
runoff can poUute storm water. Sttnm water can become contaminated by a wide range of contaminants when
materials wash off or dissolve into water or are added to runoff by spiUs and leaks.
Paved areas should be sloped in a inanner that minimize die pooling of water on tiie site, particulariy with
materials that may leach pollutants into storm water and/OT groundwater, such as COTUpost logs, and wood chips.
A minimum slope of 1.5 percent is recommended.
Curbing should be placed along tbe perimeter of the area to prevent the nmon of uncontaminated storm water
from adjacent areas as weU as ranoff of stonn water from the stockpUe areas. The storm drainage system should
be designed to minimize die use of catcfa basins in the interiOT of tiie area as tiiey tend to rapidly fiU wUh manu-
facttiring materiaL In tiiese cases, consider the u^ of die catt± basin insert fdter described in Chapter 5, TC6
(Media FUttation). llic area should be sloped to drain storm water to die perimeter wbere it can be coUected OT to
internal drainage alleyways wbere material is not stockpled. If die raw material by-product or product is a
Uquid, more information for outside suMage of Uquuls can be found under SC6, OUUIOOT Container Storage of
Liquids.
E?tamplc?i
The "doghouse" design has been used to store smaU Uquid cootainers. Tbe roof and flooring design prevent
contact witb direct rain or ranoff. Thc doghouse has two solid stmctural walls and two canvas covered walls.
Thc flooring is wire mesh about secondary containment The unit has been used successively at Lockheed
Missile and Space Company in Suimyvalc.
REFERENCES
Best Management Practices for Industtial Storm Water Pollution Conttol, Santa Clara VaUey Nonpoint Source
PoUutioa Control Program, 1992,
Stt»m Water Managemenl for Industiial Activities: Developing PoUution Prevention Plans, and Best Management
Practices, EPA 832-R-92-006, EPA, 1992.
Water (QuaUty Best Managemenl Practices Manual City of Seattie, 1989.
Industrial Handbook 4.29
* March, 1993
ACTIVITY: WASTE HANDUNG AND DISPOSAL
FUEL OIL
•
0
RECYCLABLE
WASTE
ONLY
Applications
Manufacturing
Material Handling
Vehhie Maintenance
"ignstructioji,
Commercial Activities ^
Roadways
Waste Containment
(housekeeping Practh^^
DESCRIPTION *
Prevent or reduce tbe discharge of poUutants to storm water from waste handUng and
(Usposal by tracking waste generation, storage, and disposal; reducing waste generation and
disposal through source reduction, re-use, and recycling; and preventing runon and ranoff
firom waste management areas.
APPROACH
Maintain usage inventory to Umil waste generation.
Raw material substitution or eUmination.
Process or equipment modification.
Production planning and sequencing.
SARA Titie m. Section 313 requires reporting for over 300 Usted chemicals and
chemical compounds. This requirement should bc used to ttack these chemicals
although tbis is nol as accurate a means of tracking as otiiei api^oacfaes.
Track waste generated.
(Characterize waste stream.
Evaluate the prtxess generating the waste.
Prioritize waste streams using: manifests, biennial reports, permits, environmen-
tal audits, SARA Tide HI reports, emission reports, NPDES monitoring reports.
Inventory reports.
Data on chemical spills.
Emissions.
Shelf Ufe expiration.
Use design data and review: process flow diagram, materials and a|>pUcations diagram,
piping and instructions, equipment list plot plan.
Use raw material and production data and review: composition sheets, materials safety
data sheets (MSDS), battdi sheets, produa OT raw material inventory records, i»oduc-
tion schedide, operatOT data log.
Use economic data and review:
Waste treatment and disposal cost
Produa utiUty and economic cost
Operation and maintenance labOT cost
Recycle materials whenever possible. .
Maintain Ust of and thc amounts of materials disposed.
Waste segregation and separation.
Check industrial waste management areas for spills and leaks.
Cover, endose, or berm industtial wastewater management areas whenever possible to
prevent conuia witb ranon OT ranoff.
Equip waste transport vehicles witiii anti-spUl equipment
Targeted Constituents
O Sediment
O Nutrients
9 Heavy Metals
0 Toxic Materials
O Floatable Materiais
O Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
W Ukely to Have
Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
O Capital Costs
Q O&M Costs
O Maintenance
Q Training
High O Low
SC9
Best'
Management
Practices'"
Industrial Handbook 4-30 March, 1993
ACTIVITY: WASTE HANDUNG AND DISPOSAL (Continue)
• Minimize spills and fugitive losses such as dust or mist from loading systems.
• Ensure that sediments or wastes are prevented from being tracked off-site.
• Training and supervision.
• Stendl storm drains on tbe faciUty's property with prohibitive message regarding waste disposal.
• FOT a qmck reference on disposal alternatives for specific wastes see Table 4.1, SC 1.
• Consider ordering industty-specific OT waste stteam-specific guidance firom PPIC (see Appendix G).
REQUIREMENTS
• Costs {Capital, O&M)
Capital and O&M costs for these programs wiU vary substantially depending on tiic size of the faciUty and tiie
types of waste handled. Costs should Ije low if there is an inventory program in place.
• Maintenance
None except fot maintaining equipment fOT material ttacking program.
LIMITATIGNS
• Hazardous waste that cannot be re-used OT recycled must be disposed of by a Ucensed hazardous waste hauler.
Industrial Handbook 4-31 March, 1993
Additional Information — waste Handling and Disposal
Industrial waste management activities occur in areas tbat can contaminate storm water and include landfiUs, waste piles,
wastewater and solid waste treatment and disposal, and land appUcation. Typical operations which affea storm water
poUution may include waste pumping, tteatment chemicals storage, muing, aeration, clarification, and solids dewater-
ing.
Waste Reduction
Waste SpiUed, leaked, or lost from waste managemenl areas or outside manufaauring activities may buUd up in soils or
in otiier surfaces and bc carried away by storm water mnoff. There is also a potential for Uquid waste from lagoons or
surface impoundments to overflow to surface waters or soak tbe soil where poUutants may be picked up by storm water
runoff.
Waste reduction for manufacturing activities is die best way to reduce the potential of storm water contamination from
waste management areas. Reduction in the amount of industtial waste generated can be accompUshed using many
different types of source contttils such as:
• Production planning and sequendng.
• Process OT equipment modification.
Raw material substitution OT elimination.
• Loss prevention and housekeeping.
• Waste segregation and separation.
• Close loop recycling.
An approach to reduce storm water poUution from waste handUng and disposal is to assess process activities at tbe
faciUty and reduce waste generation. Thc assessment is designed to find situations wbere waste can be eliminated or
reduced and emissions and environmental damage can be minimized. The assessment involves coUecting process
specific information, setting poUution prevention targets, and developing, screening and selecting waste reduction
options for further study. Starting a waste reduction program is economically beneficial because of reduced raw material
purchases and lower waste disposal fees. In addition, material tracking systems to increase awareness about material
usage can reduce spiUs and minimize contamination, thus redudng the amount of waste produced.
Snill/I.eak Contml
Waste can bc prevented firom contaminating storm water by diecking waste management areas for leaking containers or
spills. Corroded OT danu^cd containers can begin to leak at any time. Transfer waste firom tbese damaged containers
into safe containers. Dumpsters should be covered to prevent rain firom washing waste out of boles or cracks in the
bottom of tbe dumpster. Leaking equipment including valves, Unes, seals, or pumps should be repaired prcanptiy.
Vehides transporting waste should bave spiU prevention equipment that can prevent spUls during transport Tbe spiU
prevention equipment includes:
• Vehides equipped vitb baffles fOT Uquid waste.
• Tracks with sealed gates and spiU guards for soUd waste.
Loading or unloading wastes can contaminate storm water when the wastes are lost from the transfer. Loading systems
can also be used to minimize spills and fugitive emission losses such as dust OT mist Vacuum transfer systems can
ntinimize waste loss.
Runon/Rmioff Prevention
Storm water ranon should be prevented from entering the waste management area. Sttirm water poUution from mnon
can be prevented by enclosing tiie area OT buUding a berm around die area. Otber alternatives for reducing storm water
poUution include:
• Preventing the waste materials frcan directiy contacting rain.
Industrial Handbook 4 . 32 March, 1993
Additional Information — waste Handling and Disposal
Moving the activity indoor after ensuring tbat aU safety concems such as fitre hazard and ventilation are addressed.
Covering die area with a permanent roof.
Covering waste pUcs witb temporary covering material such as reinforced tarpaulin, polyethylene, polyurethane,
polypropylene or hypalon.
To avoid tracking materials off-site, tbe waste management area should be kept clean at aU times by sweeping and
cleaning up spills immcdiatdy. Vehides should never drive through spills. If necessary, wash vehicles in designated
areas before they leave the site, and contrd the wash water.
Minimizing the ranoff of poUuted storm water from land a^^Ucation of industrial waste on-site can be accomplished by:
• Choosing a site wbere:
slopes are under 6 peicent ^
tbe soU is permeable
there is a low water table
il is kx:ated away fimn wetilands or marshes
there is a dosed drainage system
• AvokUng applying waste to tbe site:
when it is raining
when die ground is firozen
when die ground is saturated with water
• Growing vegetation on land disposal areas to stabilize soils and reduce the volume of surCace water rtmoff from die
site.
• Maintaining adequate bairieis between die land appUcation site and tbe receiving waters. Planted strips are particu-
lariy good.
• Using erosion conticd tediniques
mulching and matting,
fUter fences,
straw bales,
diversion terracing,
sediment basins,
• Performing routine maintenance to ensure thc erosion cootrol OT site stabiUzation measures are woridng.
Examples of Effeaive Proyrams The port of Long Beach has a state-of-the-art database for identifying potential poUutant sources, documenting fadUty
management practices, and tracking poUutants.
REFERENCES
Best Management Practices for Industrial Storm Water PoUutioa Coattol, Santti Clara VaUey Nonpoint Source PoHution
Control Program, 1992,
PubUcatioas Than Can Work FOT You!; CaUfornia Department of Toxic Substances Conttol Sacramento, CA, 1991 (A
Ust and order form fOT waste miiiiinizatioo publk:atioas firtxn the State),
Storm Water Management for Industrial Activities: Developing PoUutioa Prevention Plans, and Best Management
Practices, EPA 832-R-92-006. USEPA, 1992.
Distribute List PoUution Prevention Infonnation aearinghouse, USEPA 1992.
Industrial Handbook 4-33 March, 1993
ACTIVITY: CONTAMINATED OR ERODIBLE SURFACE AREAS Applications
Manufacturing
Material Handling
Vehhie Maintenance
Construction^
Commercial Activities
dRoadways^
Waste Containment
Housekeeping Practices
DESCRIPTION
Prevent or reduce tbe discharge of poUutants to storm water firom contaminated or
erodible surface areas by leaving as much vegetation on-site as possible, minimizing soil
exposure time, stabUizing exposed soils, and i»eventing storm water ranon and runoff.
APPROACH
This BMP addresses soils which are not so contaminated as to exceed criteria (see Titie 22
California Code of Regulations for Hazardous Waste Criteria), but thc soU is eroding and
canying pollutants off in tbe storm water.
Contaminated or erodible surface areas can be controUed by:
• Preservation of natural vegetation,
• Re-vegetation,
• Chemical stabilization,
• Removal of contaminated soils, or
• (jeosynthetics.
FOT a quick reference on disposal altematives for specific wastes see Table 4.1, SCI.
REQUIREMENTS
• Cost (C:apital, O&M)
Except for preservation of natural vegetation, each of tiie above solutions can bc
quite expensive depending upon the size of thc area.
• Mainteiiance
Maintenance should be minimal, except possibly if irrigation of vegetation is
necessary.
LIMITATIONS
Disadvantages of preserving natural vegetation or re-vegetating include:
• Requires substantial planning to preserve and maintain die existing vegetation.
• May not be cost-effective witii high land costs.
• Lade of rainfaU and/or poor soils may lhnit thc success of re-vegetated areas.
Disadvantages of chemical stalnUzation indude:
• Creation of impervious surfaces.
• May cause harmful effects on water quaUty.
• Is usuaUy more expensive than vegetative cover.
Targeted Constituents
9 Sediment
9 Nutrients
# Heavy Metals
# Toxic Materials
# Fhatable Materials
0 Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
# Ukely to Have
Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
O Capital Costs
Q O&M Costs
O Maintenance
O Training
High O Low
SC10
Best'
Management
Practices'*
Industrial Handbook 4-34 March, 1993
Additional Information — Contaminated or Erodible Surface Areas
Of interest here arc areas witiim tiie industrial site tiiat are bare of vegetation and dierefore subject to erosion. They may
or may not be contaminated from past« current activities. Activity may OT may not bc occuning in tiie area of interest
According to tiie State's General Industtial Activity Storm Water Permit die SWPPP must mdude BMPs tiial deal witii
diese sittiations. If tiie area is temporarUy bare because of consttuction, see SC12, BuUding Repair, Remodeling, and
Constmction.
Contaminated or erodible surfaces can resuU from Uae human activities such as vegetation removal, compacting or
distiirbing soil, and changing natiiral drainage pattems. Industties must klentify die areas of ccrataminated or erodible
surfaces. Thc areas may include:
Heavy activity where plants cannot grow.
• SoU sUx;lq)Ues.
Steep slopes. .
• Constraction areas.
• DemoUtion areas.
• Any area wbere soU is disttirbed.
The most effective way to control erosion is to preserve existing vegetation. Preservation of natural vegetation provides
a nattiral buffer zone and an opportunity for infUfration of storm water and capmre of poUutants in die soU niattix. By
preserving stabilized areas, il minunizcs erosion potential protects water quaUty, and {Hovidcs aestitetic benefits. This
iwactice is used as a permanent conttol measure. Vegetation preservation on-site should bc planned before dismrbing die
site. Preservation requires good site management to minimize die impaa of constmction when constraction is undenvay.
Proper maintenance is important to ensure healdiy vegetation tiiat can conttx>l erosion. Different species, soU types, and
cUmatic conditions wUI require different maintenance activities such as mulcbmg. feitiUzing. liming, irrigation, pruning
and weed and pest controL Mamtenance should be perfonned regulariy especiaUy during construction phases.
Advantages of preservation of natural vegetation are:
• Caa handle higher quantities of storm water runoff tiian newly seeded areas.
• Increases die fdtering capadty because vegetation and root systems are usually dense in preserved natural
vegetation.
• Enhances aesthetics.
• Provides areas for infUttation, dius reducing die quantity and veiodty of stoim water ranoff
• AUows areas where wiMlife can remain undisttirbed.
Provides noise buffers and screens fOT on-site toleration.
• UsuaUy requires less maintenance tiian planting new vegetation.
The measure of chotee is to leave as much native vegetation on-site as possible, tiiereby reducing OT diminating die
problem. However, assuming die site already bas conttuninated or erodible surface areas, dicre are diree possible courses
of action:
1. Re-vegeuite die area if il is not in use and tiierefore not subjea to dainage firom site activities. In as much as
die area is already devoid of vegetation, special measures are Ukely necessary. Lack of vegetation may be
due to die lack of water and/w poOT soUs. The later can perfia^is be solved widi fertiUzation. Or die ground
may simply be too compacted firom prior use. Improving soU conditions may be suffident to support
vegetation. If avaUable process wastewater can bc used fOT irrigation, see Consttuction Best Management
Practice Handboc* fOT procedures to estabUsh vcgeQtion.
Industrial Handbook 4. 3S .
* -^^ March, 1993
Additional Information — contaminated or Erodlble Surface Areas
I. Chemical stabiUzation (for example ligno suUate) can be used as an altemate in areas where temporary
seeding practices cannot be used because of season or dimate. It can provide immediate, effective, and
inexpensive erosion control. AppUcation rates and procedures recoinmended by tiie manufaaurcr should be
foUowed as closely as possible to prevent tiie product firom forming ponds and creating large areas where
moisture cannot penetrate the soil The advantages of chemical stabilization include:
EasUy appUed to die surface.
• Effective in stabiUzing areas.
Provides immediate {sotection to soils dial are in danger of erosion.
3. Removal of contaminated soils is a last resort and quite expensive. The level and extent of tiic contamination
must be determined. Tbis detennination and removal must comply witii Suite and Federal regulations,
permits must bc acquired, and fees paid.«
4. GcosyntiSetics indude those materials tiiat are designed as an impermeable barrier to contain or conttol large
amounts of Uqukl OT soUd matter. Geosyntiietics have been developed primarily for use in landfills and surface
impoundments, and die tedinotogy is weU established. There are two general types of geosyntiietics:
gecHncmbianes(impetmeable) and geotextiles(permeable).
Geomembranes are composed of one of three types of impenneable materials: elastcaners(rabbers),
tiiermoplasics(plastics). or a combination of tiiese two types of materials. The advantages of tiiese materials
inchide: I) die variety of compounds avaUable, 2) sheeting is produced in a factory environment 3) polymeric
membranes are flexible, and 4) simple instaUation. The disadvantages include: 1) chenucal resistance must be
determined for each appUcation, 2) seaming systems may be a weak Unk in tiie system, and 3) many materials
are subject to attack fipom biotic, mechanical or environmental sources.
• Geotextiles are uncoated synthetic textile products tiiat are not water tight Tbey are composed of a variety of
materials, most commonly polypropylene and polyester. Geotextiles serve five basic functions: 1) fUttation, 2)
drainage, 3) separation, 4) reinforcement and 5) armOTing.
FOT more information on geosyntiietics, see die reference below.
REFERENCIS
Covers for UnconttoUed Hazardous Waste Sites, USEPA, EPA/54Or2-85/0O2, PB87-119483, 1985.
Industrial Handbook 4-36 March, 1993
ACTIVITY: BUILDING AND GROUNDS MAINTENANCE
Graphic: Nonh Central Texas COG. 1993
Applications
Manufacturing
Material Handling
Vehicle Maintenance
Construction
C^ammercial Activ^s^
C^Roadway^^
Waste Containment
Chousekeeping PracdcM^
DESCRIPTION
Prevent or reduce tbe discharge of poUutants to storm water firom buildings and grounds
maintenance by washing and cleaning up with as Uttle water as possible, preventing and
cleaning up spills immediately, keeping debris firom entering the storm drains, and
maintaining the sttxm water collection system.
APPROACH
• Leaving or planting native vegetation to reduce water, fertiUzer, and pestidde needs.
• Careful use of pestiddes and fertUizers in landscqiing.
• Integrated pest managemenl wbere appropriate.
• Sweqiing of paved surfaces.
• Cleaning of thc storm drainage system at appropriate intervals.
• Proper disposal of wash water, sweepings, and sediments.
• FOT a quick reference on disposal alternatives for spedfic wastes see Table 4.1, SCI.
REQUIRMENTS
• Costs (Capital, O&M)
Cost wiU vary depending on die type and size of faciUty.
OveraU costs ^ould be low in comparison to otiier BMPs,
• Maintenance
The BMPs themselves relate to maintenance and do not require maintenance as
they do not involve stractures.
LIMITATIONS
Alternative pest/weed controls may not be available, suitable, or effective in every
case.
Targeted Constituents
% Sediment
9 Nutrients
9 Heavy Metals
# Toxic Materials
# Fhatable Materials
% Oxygen Demand-
ing Substances
# Oil& Grease
O Bacteria & Viruses
• Ukely to Have Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
O Capital Costs
Q O&M Costs
Q Maintenance
O Training
High O Low
SC11
Best
Management
P^actices^
Industrial Handbook 4-37 March, 1993
Additional Information — Building and Grounds Maintenance
BuUdings and grounds maintenance includes taking care of landscaped areas around the fadUty, cleaning of paridng lots
and pavement otiier tban in tbe area of industtial activity, and die cleaning of tbe storm drainage system. Painting and
otiier miuOT or majOT repairs of buUdings is covered in SC12 (Building Repair, RemodeUng. and Consttuction). Certain
normal maintenance activities can generate materials tiiat must be properly disposed. Other maintenance activities can
enhance water quaUty if tiiey are carried out more frequendy and/or in a more deUberate fashion.
Pesridde/FerriliTffr Manaownwit
Landscape maintenance involves the use of pesticides and fertUizers. Proper use of diesc materials wUl reduce die risk
of loss to Storm water. In particular, do not apply tiiese materials during thc wet season as tbey may be canied firom die
site by the next storm. When irrigating the landscaped areas, avoid over-watering not only to conserve water but to
avoid the discharge of water wbich may have become coitaminated witii nutrients and pestiddes.
It is important to properly store pestiddes and appUcation equipment and to dispose tbe used containers in a responsible
manner, consistent witii state regulations, Personnd who use pestiddes should be ttained in tiieir use. The California
Departtnent of Pestidde Regulation and county agriculttiral commissioners Ucense pestidde dealers, certify pesticide
applicators, and conduct on-site inspections.
Written procedures for die use of pesticides and fertilkers relevant to your facUity would help maintenance suiff under-
stand the "do's" and "don'ts". If you have large vegetated areas, consider tbe use of integrated pest management (IPM)
tediniques to reduce the use of pesticides.
Paridng/Storm .Sewer Maintpn.nnrp
A parking area that drains to thc same storm drainage system as die industtial activity dial is to bc permitted must also bc
evaluated for suitable BMPs. Storm water from parking lots may contain undesirable concenttations of oU, grease,
suspended particulates, and metals such as copper, lead, cadmium, and zinc, as weU as the petroleum byproducts of
engine combustion. Deposition of air particulates, generated by die facUity or by adjacent industries, may connibute
sigiuficant amounts of poUutants.
Thc two most ^propriate maintenance BMPs are periodic sweeping and cleaning cateh basins if they are part of the
drainage system. A vacuum sweeper is die best metiiod of sweeping, rather than mechanical brash sweeping wbich is
not as effective at removing thc fine particulates.
Catch basins in parking lots generaUy need to be deaned every 6 to 12 mondis, or whenever die sump is half fuU. A
sump dial is more dian half full is not effective at removing additional particulate pollutants firom die storm water. If the
Stonn drain Unes have a low gradient less dian about 0 J fea in elevation drop per 100 feet of Une, it is Ukely dial
material is settling in Uae lines during die small frequent stonns. If you bave nol cleaned die storm drain system POT
some time, check tiie lines as weU. If diey are not deaned, die catt± basins wiU Ukely be filled during die next signifi-
cant storm by material diat is washed from die Unes. Also, instaU "ttim-down" elbows or sunilar devices on die outiets
of die cateh basins; they serve to retain floatables, oU and grease.
Ckarly maik die storm drain inlets, either witii a COIOT code (to distinguish frcm process water inlets if you have diem)
OT widi die painted stencU of "DO NOT DUMP WASTE". This wiU minimize inadvertent dumping of Uquid wastes.
Sweepings and sediments firom diese maintenance activities are generally low in mettds and odier pollutants and there-
fore can be disposed on-site OT to a consttuction debris landfdl Test die material if diere is a reasonable doubt whether
metals or odier pollutants are present If concenttations of contaminants are high, it indicates dial otiier BMPs may be
needed to elhninate OT reduce emissions from die source. If a vactor ttuck is used to clean the storm drainage system.
Industrial Handbook 4-38 March, 1993
Additional Information — Buiiding and Grounds Maintenance
dirty water wiU be generated. This water should not bc discharged to die storm drainage system as it is silt laden and
contains much of die poUutants tiiat were removed by die cateh basins. Tbe water should be disposed to die process
wastewater system, if you have one, OT to the pubUc sewer if permission is granted by tiie local sewer audiority. AJtenia-
tively, the water can bc placed somewhere on die site where it can evaporate.
The cleaning of die paved surfaces and cateh basins in die areas of industrial activity has been discussed previously in
SC5 (Loading and Unloading of Materials), SC7 (Outdoor Process Equipmeni Operations and Maintenance), and SCS
(OutdoOT Storage of Raw Materials, Products, and Byproducts).
If some ranployecs have cars tiiat are leaking alnionnal amounts of engine fluids, encourage them to have the problem
COTTCCted.
Fxamples of FfTeetive Programs
Infonnation on integrated pest management may be obtained from tiie Bio-Integral Resource Center, P.O. Box 7414,
Bericelcy, CA 94707,510-524-2467.
REFERENCES
Best Management Practices for Industtrial SttJrm Water PoUution Conttol Santa Clara VaUey Nonpoint Source PoUution
Conttol Program, 1992.
Industi-ial Handbook 4 - 39 March, 1993
ACTIVITY: BUILDING REPAIR, REMODEUNG AND CONSTRUCTION Applications
Manufacturing
Material Handling
Vehhh Maintenance
dConstruction^
C^Commercial AcUviti^^
Roadways
Waste Containment
(housekeeping Practic^^
DESCRIPTION
Prevent OT reduce die discbarge of poUutants to storm water from buUding repair, remodel-
ing, and constraction by using soU erosion controls, endosing or covering buUding
material storage areas, using good housekeeping practices, using safer alternative prod-
ucts, and ttaining employees.
APPROACH
Use soil erosion control techniques if bare ground is temporarUy exposed. See the
Constraction Activity Best Management Practice Handbook.
• Use pennanent soU erosion control techniques if the remodeUng clears buUdings from
an area dial are not to be replaced. See SCIO (Contaminted OT Erodible Suriace
Arras).
• Enckise painting operations, consistent witii local air quality regulations and OSHA.
• Properiy store materials that are normally used in repair and remodding such as
paints and solvents.
• Properly Store and dispose waste materials generated from the activity. SecCA20,
SoUd Waste Management Constmction Handbook.
• Maintain good housekeeping practices whUe work is underway.
REQUIREMENTS
• Costs (Ci^ital O&M)
These BMPs are generaUy of low to modest in cost
LIMITATIONS
• This BMP is for minor constraction only. Tbe State's General Consttuction Activity
Storm Water Pemtit has more requirements fOT larger projects. Thc ccmpanioa
"Coostructioa Activity Best Manageinent Practice Handbook" contains spedfic
guidance and best management practices for larger-scale projects.
• Hazardous waste dial cannot bc re-used or recycled must be disposed of by a Ucensed
hazardous waste hauler.
• Safer alternative products may not be available, suitable, or effective in every case.
• Be certain dial actions to help storm water quality are consistent with Cal- and Fed-
OSHA and air quality regulations.
Modifications are a common occurrence particularly at large industrial sites. The activity
Targeted Constttuents
9 Sediment
O Nutrients
9 Heavy Metals
# Toxh Materials
9 Floatable Materials
O Oxygen Demand-
ing Substances
# 0/7 & Grease
O Bacteria & Viruses
• Ukely to Have
Sl^ificant Impact
o Probable Low or
Unknown Impact
Implementation
Requirements
O Capital Costs
Q O&M Costs
Q Maintenance
O Training
High O Low
SC12
Best'
Management
Practices>
Industrial Handbook 4-40 March, 1993
Additional Information — Buiiding Repair, Remodeling, and Construction
may vary from minor and normal buUding repair to major remodeling, or tbe installation of new fadUties on cunentiy
open space. Tbese activities can generate pollutants dial can reach storm water if premier care is not taken. Tbe sources of
these contaminants may be solvents, paints, paint and vamish removers, finishing residues, spent thinners, soap cleaners,
kerosene, asphalt and concrete materials, adhesive residues, and old asbestos installation.
Good Housekeeping
Proper care involves a variety of mostiy conunon sense, housekeeping actions such as:
• Keep the woik site clean and orderly. Removing debris in a timely fashion. Sweep tiie area.
• Cover materials of particular concern that must bc lefl out particulariy during the rainy season.
• Educate employees who are doing the work.
• Infonn on-site contractors of company poUcy on tbese matters and include appropriate provisions in their contiact to
make certain proper housekeeping and dispdsal practices are implemented.
• Make sure that nearby storm drains are weU maiked to minimize tbe chance of inadvertent disposal of residual
paints and otber Uquids.
• Do not dump waste Uquids down tbe storm drain.
• Advise conaete tmck drivers to not wash their ttuck over the storm drain. Have a designated area tbat does not
drain to die storm drain.
• Clean die stonn drain system in thc immediate vidnity of tbe constmction activity after it is completed.
Proper education of off-site contractors is often overlooked. The consdentious efforts of weU trained employees can be
lost by unknowing off-site contractors, so make sure tbey are weU informed about what tbey are expected to do.
Painting operations should bc properiy enclosed or covered to avoid drift Use temporary scaffolding to bang drop clodis
OT draperies to prevent drift AppUcation equipmeni that minimizes overspray also helps. Local air poUution regulations
may, in many areas of tiic state, specify painting procedures which if properiy carried out are usuaUy suffident to proted
water quaUty. If painting requires saaping or sand blasting of tbe existing surface, use a ground doth to coUea tbe
chips. Dispose tbe residue properly. If die paint contains lead or tributyl tin, it is considered a hazardous waste.
Mix paint indoors before using so tbat any spUl wiU not be exposed to rain. Do so even during dry weathei because
deanup of a spiU wiU never be 100% effective. Dried paint wiU erode from a surface and be washed away by stonns. If
using water based paints, clean tbe appUcatioa equipment in a sink that is connected to tbe sanitary sewer. Properly store
leftover paints if tbey are to be kept fOT die next job, OT dispose properly.
When using sealants on wood, pavement roofs, etc, qiuckly dean up spills. Remove excess Uquid with absorbent
material or rags. If when rep^iing roofs, smaU partides have accumulated in tbe gutter, dther sweep out thc gutter or
wash the gutter and trap the particles at the oudet of die downspout A sock OT geofabric placed over die outlet may
effectively trap tbe materials. If tbe downspout is tight lined, place a temporary plug at the first convenient point in the
stonn drain and pump out the water with a vaaor tnK:k, and clean die cateh basin sump wbere you placed die plug.
Soil/Erosion Contrnl
If the woric involves exposing large areas of soU employ the apprc^riate soil erosion and control techniques. See the
Constraction Best Management Practice Handbook. If old buUdings are being tom dovm and not replaced in die near
fiittue, stabilize die site using measures described in SCIO, Contaminated or Erodible Surface Areas.
If a buUding is to bc placed over an open area with a storm drainage system, make sure tbe sttxm inlets widiin die
Industrial Handbook 4-41 March, 1993
Additional Information — SuIIdlng Repair, Remodeling, and Construction
budding are covered or removed, OT tbe storm line is connected to the sanitary sewer. If because of tbe remodeUng a
new drainage system is to be instaUed or the existing system is to be modified, consider instaUing cateh basins as they
serve as effective "in-Une" tteaonenl devkes. Sec TC2 (Wet Ponds) in Chapter 5 regarding design criteria. Include in
the catdi basin a "tum-down" elbow OT similar device to trap fioarables.
Recyde residual paints, solvents, lumber, and other in3tPTial<; to the maximum extent practical. Buy recycled products
to die maximmn extent practicaL.
REFERENCES
Best Management Practices for Industrial Storm Water PoUution Conttol Santa Clara VaUey Nonpoint Source PoUution
Conttol Program, 1992.
Industrial Handbook 4-42 March, 1993
ACTIVITY: OVER-WATER ACTIVPRES
W*TEI*-"nQMT
msTE ootmiHEii
roRTuunKesio
Applicati'ons
Manufacturing
<C^terial HandUng^
Vehhie Maintenance
Construction
^Commercial Activiti^^
Roadways
/aste Containment^
Tousekeeping Practices^.
DESCRIPTION
Prevent or reduce die discharge of poUutants to storm water and receiving waters from
over-water activities by minimizing over-water maintenance, keeping wastes out of the
water, cleanmg up spiUs and wastes immediately, and educating tenants and employees.
APPROACH
Properly dispose of domestic wastewater and ballast water.
Limit over-water huU surface maintenance to sanding and minor painting.
Use pbosphate-free and biodegradable detergents for huU washing.
Use secondary containment on paint cans.
Have available spiU containment and cleanup materials.
Use ground clodis when painting boats on land.
Use ttirps, plastic sheeting, ete. to conttiin spray paint and blasting sand.
Properly dispose of surface chips, used blasting sand, residual pamts, and other
materials. Use tempc«ary stt)rage containment dial is not exposed to rain.
Immediately clean up spills on docks OT boats.
Sweep drydocks before flooding.
Clean catch basins and thc storm drains at regular intervals.
Post signs to indicate proper use and disposal of residual paints, rags, used oil and
otber engine fluids.
Educate tenants and employees on spill prevention and deanup.
Include appropriate language in tenant contracts indicating dieir responsibUities.
Marinas should provide wastewater disposal faciUties.
REQUIREMENTS
• Cosl (Capital, O&M)
- Most of die BMPs are of low and modest cost Exceptions are stations for
temporary storage of residual paints and engine fluids, and wastewater pumpout
fadUties.
• Maintenance
Keep ample supply of spiU cleanup materials.
LIMITATIONS
Private tenants at marinas may resist resttictions on Clipboard painting and maintenance.
Existing contracts widi tenants may not allow die owner to require dial tenants abkle by
new rales diat benefit water quality. Even biodegradable cleaning agents have been found
to tie toxic to fish.
Targeted Constituents
O Sediment
O Nutrients
# Heavy Metals
# Toxh Materials
# Floatable Materials
# Oxygen Demand-
ing Substances
# Oil & Grease
# Bacteria & Viruses
# Ukely to Have Sl^ificant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
O Capital Costs
Q O&M Costs
Q Maintenance
Training
High O Low
SC13
Best'
Management
Practices'*
Industrial Handbook 4-43 March, 1993
Additional Information — over-water Activities
Over-water activities occur at boat and ship repair yards, marinas, and yacht clubs, altiiough die later are not required to
obtain a permit Activities of concern indude chipping and painting of hulls, on board maintenance of engines, and the
disposal of domestic wastewater and ballast water. Widi few exceptions, BMPs to protect water quaUty are common
sense, low cost changes to nonnal day-to-day procedures.
Over-water Activitv Minimiratinn
Woik on boats in tiie water should bc kept to a minimum. Major hull resurfadng should occur on land. Surface prepara-
tion over water should bc limited to sanding. Painting should be Umited to spot work. In marinas, tenant maintenance
over water should bc such as to nol require opening more than a pint size paint can. Paint mixing should not occur on
thc dock.
Good Housekeeping *
When conducting on board maintenance, used antifreeze should bc stored in a separate, labeled drum and recycled. Fuel
tank vents should have valves to prevent fud oveiflows or spills. Boats widi inboaid engines should bave oU absorption
pads in bUge areas and diey should be changed when no longer useful OT at least once a year.
Marina owners should provide temporary storage stations for used engine fluids, paint cans, and other maintenance
materials. Signs should be posted at tbe head of each dock indicating maintenance rules. Marina owners should instaU a
wastewater disposal system, eitiier dockside lines or a pumpout station. Tenant conttacts should include language
indicating their responsibiUties.
When painting on shore, place paint cans in a tray OT comparable device dial coUecis spills and drips. Use ground cloths
when painting. Use spray guns that minimize overspray; also enclose tbe area with plastic tarps. Identify a designated
area fOT washing boats. Vacuum sweep woric areas frequentiy. When doing repairs OT painting on a tidal grid OT similar
open "dry doci:", use ground cloths to retain chips and spiUed paint Thc repair yard owner should instaU signs so tiiat
boat owners who are doing their own work know tiieir responsibiUties,
Large boat repair yards can unplement the above BMPs. -There are several additional measures. With regard to dry dock
operations: sweep the accessible areas of tiie dry dock before flooding; and pidc up otber debris that appears after tbe
ship is floated. Remove floatable debris such as wood. Shipboard cooling and process water discharges should bc
directed to minimize contaa widi ^>ent abrasives, paints, and odier debris. Look for and repair leaking valves, pipes,
hoses, or sod chutes canying either water OT wastewater. Pbstic sheeting OT other suitable materials should be instaUed
when sandblasting and spray painting.
Use drip pans OT comparable devices when transferring oils, solvents, and paints. Regulariy clean thc shoreside work
areas of debris, sandblasting material, ett^ Clean catch basins or other parts of tbe stonn drainage system diat might
accumulate these materials.
Fish WfiMc
Fish wastes must also be managed pn^ierly. RecycUng fish wastes bade to die water is encouraged when disposal wiU
not result in water quaUty OT public nuisance problems, such as wastes washing up onshwe OT causing odors or bacteria
problems. Fish wastes should not be recycled in any dead end lagoons OT odier poorly flushed areas. Marina owners
should provide fish cleaiung stations where waste recycling can occur without adversely affecting water quaUty.
Note: San Francisco Bay Area boat repair and maintenance fedUties. The San Francisco Bay Regiooal Water Quality
Control Board has issued a General Storm Water NPDES Peimit to boat yards which work primarUy on pleasure vessels
less than 65 feet in lengdi. Thc General Permit requires maintenance of pressure wash containment and recycle or
pretteattnent system implemenuition ofa Stonn Water PoUution Conuxil Plan (SPCP) and a Monitoring Program.
Industriai Handbook 4-44 March, 1993
Additional Information — over-water Activities
REFERENCES
Proposed Guidance Specifying Management Measuies for Sources of Nonpoint PoUution in Coastal Waters, USEPA,
1992.
(jcneral NPDES Permit for Discharges of Sttmn Water firom Boat Repair FacUities, SFBRWCJCB, 1992.
Industrial Handbook 4-45 March, 1993
ACTIVITY: EMPLOYEE TRAINING Applications
C!l^^^nufacturi^g~^
Material Handline
Vehhh Maintenance
Construction
C^^mmercial Activities^
Roadways
DESCRIPTION
Emptoyee training, like equipment maintenance, is not so much a best management practice as it is a metiiod by wbich to
implement BMPs. Tbis faa sheet highU^is the importance of ttaining and of nitegrating the elements of employee
training from tbe individual source controls into a comprehensive training program as pan of a facility's Storm Water
PoUution Prevention Plan (SWPPP).
The spedfic employee training aspects of each of tiie source conttx>ls are highlighted in die individual fact sheets. The
focus of diis faa sheet is more general and includes die overaU objectives and approach for assuring employee ttaining
in storm water poUution prevention. AccOTdingly, tiie organization of tbis faa sbeet differs somewhat from tbe other faa
sheets in this cba^r.
OBJECTIVES
Employee training should be based on four objectives:
• Promote a dear identification and understanding of tiie problem, including activities witb tbe potential to pollute
sb:»m water;
• Identify solutions (BMPs);
• Pnanote employee ownership of tiie iroblems and tbe solutions; and
Integrate employee feedback into ttaining and BMP unplementation.
APPROACH
• Integrate training regarding storm water quality management witii existing training programs tbat may bc required
for your business by other regulations such as: tiie fllncss and Injury Prevention Program (RPP) (SB 198) (Califomia
Code of Regulations Titie 8, Seaion 3203), tiie Hazardous Waste Operations and Emergency Response
(HAZWOPER) standard (29 CFR 1910.120), tiie SpUl Prevention Conttol and Countenneasure (SPCQ Plan (40
CFR 112), and tiie Hazardous Materials Management Plan (Business Plan) (Califomia Healtii and Safety Code,
Seaion 6.95).
• Businesses, particularly smaUer ones tiiat are not regulated by Federal, State, or local regulations, may use tiie
information in this Handbodc to develop a uaining program to reduce tibeir potential to pollute storm water.
LISTING OF INDUSTRIAL ACnvrTIES
Employee training is a vital component of many of die individual source control BMPs included in tiiis chapter. Follow-
ing is a compilation of the ttaining aspects of the source conttol fact sheets.
Indastrial Hundl)ook 4 - 46 March, 1993
ACTIVITY — EMPLOYEE TRAINING (Continue)
SCI Non-Storm Water Discharges to Drains
• Use thc quick reference on disposal altematives (Table 4.1) to train employees in proper and consistent methods
for disposal.
• Consider posting tbe quick reference table near stotm drains to reinforce training.
SC2 Vehicle and Equipment FueUng
• Train employees in proper fuding and cleanup procedures.
• The SPCC Plan may be an effective program to reduce die number of acddental spills firom fueling.
SC3 Vehide and Equipment Washing and Steam Cleaning
• Train employees in sttmdaid operating jxocedures and spUl cleanup techniques described in die faa sbeet
S(T4 Vehicle and Equipment Maintenance and Repair
• Train employees in standard operating procedures and S^HU cleanup techniques described in the faa sbeet
• Paint StencUs to remind employees iiot to pour waste down Storm drains,
SCS Outdoor Loadin^Unloading of Materials
• Use a written operations plan that describes procedures fOT loading and/OT unloading.
• Have an emergency spiU deanup plan readily available.
• Employees trained in spiU containment and cleanup should bc present during loading/unloading.
• Make sure fork lift operators are also properly trained.
SC:6 Outdoor Container Storage of Liquids
• Registered and specifically trained professional engineeis can identify and correct potential problems such as
loose fittings, poor welding, and impiopex ot poorty fitted gaskets fOT newly instaUed tank systems.
• Emptoyees trained in emergency spiU deanup procedures should be present when dangerous waste, liquid
chemicals, or other wastes are handled.
SCJ Outdoor Process Equipment Operations and Maintenance
• The preferred and possibly most economical actioo to reduce storm water poUution is to alter the activity. This
may mean training employees to perfonn the activity during diy periods only or substittiting benign materials
fOT more toxic ones,
SCS Outdoor Storage of Raw Materials, Products, and By-Products
• Train employees in standard operating procedures and spUl cleanup techniques described in die faa sbeet
SC9 Waste Handling and Disposal
• Train employees in standard operating procedures and spill deanup tediniques described in the faa sheet
• Paint stencils to remind employees not to pour waste down stoim drains.
SCIO Contaminated or Erodible Surface Areas
• Training is not a significant element of this best management practice.
Industrial Handbook 4-47 March, 1993
ACTIVITY — EMPLOYEE TRAINING (Continue)
SCll Buikiing and Grounds Maintenance
• Personnel who use pestiddes should be ttained in tiieir use. Tbe (Talifcania Department of Pestidde Regulation
and county agriadtural commissioneis Ucense pestidde dealers, certify pestidde appUcators, and condua on-
site inspections.
• Written procedures fOT tiie use of pesticides and fertilizers relevant to your facUity would help mamtenance staff
understand tbe "do's" and "don'ts". If you have laige vegetated areas, consider die use of integrated pest
management (IPM) techniques to reduce the use of pestiddes.
SC12 Building Repair, RemodeUng, and (Construction
Proper education of off-site contractors is often overlooked, -fhe consdentious efforts of weU ttained employees
can bc lost by unknowing off-site coatracttxs, so make sure tbey are weU infonned about what they are ex-
pected todo.
SC13 Over-Water Activities
• Post signs to intUcate proper nse and disposal of residual paints, rags, used oU, and other engine fluids.
• Educate tenants and employees on spiU prevention and cleanup.
• Indude'appropriate language in tenant contracts indicating their responsibUities.
Industrial Handbook 4-48 March, 1993
APPENDIX 7
INDUSTRIAL / MUNICIPAL STORM WATER TREATMENT
CONTROLS
5. TREATMENT CONTROL BMPs
INTRODUCTION
This chapter
describes
specific
^^^HMMM^MMMMHi treatment
control Best
Management Practices (BMPs) for removing
pollutants in storm water from industrial
fadlities.
Each fact sheet contains a cover sheet with:
i
• A description of the BMP
• Suitable Applications
• Installation/Application Criteria
Requireihents
Costs, including capital costs, and
operations and maintenance (O&M)
Maintenance (including
administrative and staffing)
• Limitations
The side bar presents infonnation on which
BMP considerations, targeted constituents, and
an indication of the level of effort and costs to
implement The remainder of die fact sheet
provides further information on some of all of
tiiese topics, and provides references for
additional guideUnes.
BMP fact sheets are provided for each of the
following controls:
GENERAL
PRINCIPLES
There are
several general
principles that
are applicable to
aU freatment
contiol BMPs.
Treatment Control BMPs
TCI Infilttation
Id Wet Ponds
TC3 Consttucted Wetiands
TC4 Biofilters
TCS Extended Detention Basins
TC6 Media FUttation
TC7 Oil/Water Separators and Water
Quality Inlets
TC8 Multiple Systems
Priority should be given to source
control: Source control BMPs are
generally (but not always) less expensive
than treatment control BMPs. Also,
U-eatment confrol BMPs will not remove
all pollutants and tiieir removal efficiency
is difficult to predict given die limited
understanding as to die relationship
between facility design criteria and
performance.
Recognize the unique California
climate: Witii few exceptions most
storm water freatment experience has been
in "wet" states where vegetation can be
maintained without irrigation. In confrast,
Califomia's climate is semi-arid with the
exception of the north coast. The
freatment confrol BMPs dial require
vegetative cover may not be practical for
many areas of California unless inigation
is provided. Also, design criteria have
emerged from research of faciUties located
in climates where the rainfaU season is
coincident with the growth of vegetation.
However, in California, tiie wet season
does not occur during the primary growth
season. Caution must be used in using
design criteria that have been developed
elsewhere in the nation.
Design Storm Size; It is commonly
thought by those unfamiliar widi urban
runoff quality management dial design
storms for sizing water quality confrols
should be the same as those used for the
design of drainage facilities. This is not
tme. The damage done to a receiving
water by tiie pollutant wash-off of a 25
year storm (commonly used to size a
Industrial Handbook 5-1 March, 1993
drainage system) is inconsequential to die
potential hydraulic damage. Of concern
to water quality confrol are the small
frequent events, smaller tiian the 1-year
storm, that carry die vast majority of
ranoff and pollutants. There is little or no
incremental benefit from sizing facilities
to freat the exfreme events.
Bare and erosive soils may affect
treatment control BMPs: Protection of
natural watercourses requires that
sediment fr-ansport not be altered for the
watercourse. Therefore, consideration
must be given to fransport loads. In
addition, many residential developments in
Califomia have open space areas covered
by native vegetation. Because of the
semi-arid climate, tiie vegetation is diin
allowing for erosion during severe storms.
These higher tiian normal sediment loads
may adversely impact tiie performance
and maintenance requirements of
freatment confrol BMPs.
Consider the characteristics of
pollutants in storm water: The presence
and concenfration of poHutants is highly
variable, botii witiiin and between storms.
PoUutants come in two forms, particulate
and dissolved. Some freatment control
BMPs will only remove particulates.
Various vegetated BMPs such as wet
ponds are purported to remove dissolved
pollutants as well as particulates.
Vegetated freatment confrol BMPs have
mechanisms dial theoretically should also
remove both forms, however, the data
confirming die tiieory are limited and
sometimes confradictory.
Incorporate multiple use objectives:
Opportunities abound to integrate storm
water freatment needs witii otiier
management objectives such as die use of
wet ponds and constracted wetlands for
passive recreation, wildlife habitat, flood
detention, and ground water recharge.
Maintenance is very important: All of
die treatment confrol BMPs desaibed in
Chapter 5 are passive systems, that is,
diey operate witiiout die need for
mechanical or chemical systems.
Nonetheless, maintenance is very
important for the facilities to operate
effectively.
Factors to Consider: Each fact sheet
lists seven general factors dial are tiie
most common considerations in selecting a
freatment control BMP. In every case, all
freatment confrol BMPs must be
compatible witii existing flood confrol
objectives.
Soil: Infilfration systems must be
located on suitable soUs; vegetation
requires good soils; wet pond bottoms
require impermeable soils.
Area Required: Most BMPs require
considerable area, although some can
be placed underground.
Slope: Certain BMPs cannot be
placed on or near steep slopes as the
ponding of water or velocity of flow
may cause instability or excessive
erosion.
Water Availability: BMPs using
vegetation for pollutant removal may
require water during the dry season.
Aesdietics and safety: Where visible
or accessible to die public, aesdietics
or safety can be a concern widi some
BMPs.
Hydraulic Head: A few BMPs
require a drop in water elevation
which site topography may not
provide.
Environmental Side Effects:
Considerations for mosquito breeding,
ground water contamination, as well
as opportunities for aquatic wildlife
and passive recreation.
Industrial Handbook 5-2 March, 1993
BMP: INFILTRATION
Runoff
Considerations
Sotfs
[^ea Required^
.Slope
Water Availability
Aesthetics
Hydraulic Head
Environmental Side\
V.^.,£ffecfs
DESCRIPTION
A famUy of systems in wbich die majority of the runoff firom smaU storms is infilttated into
tiie ground rather than discharged to a surface water body. InfUtration systems include:
ponds, vaults, trenches, dry wells, porous pavement and concrete grids.
EXPERIENCE IN CALIFORNU
InfUtration ponds have been used by many local jurisdictions and CaTIrans in the Centtal
VaUey for aboul three decades.
SELECTION CRITERIA
• Need to achieve high level of particukite and dissolved pollutant removal.
• Suitable site soils and geologic conditions; low potential for long-term erosion in tiie
watershed.
• Multiple management objectives (e.g., ground water recharge or ranoff volume
control).
LIMITATIONS
• Loss of tnfilttative capadty and high maintenance cost in fine soUs.
• Low removal of dissolved poUutants in very coarse soUs.
Not suitable on fiU sites OT steep slopes.
• Risk of ground water contamination in very coarse soils, may require ground water
monitoring.
• Shoukl not use until upstream drain^e area is stabUized.
Infiltration faciUties could fall under Chapter 15, Tide 23, of Califomia Code of
Regulations regarding waste disposal to land.
DESIGN AND SIZING CONSIDERATIONS
• Volume sized to capture a particular firaction of annual ranoff.
• Pretteatment in fine soils,
• Emergency overflow or bypass for larger storms.
• Observation weU in trenches.
CONSTRUCTION/INSPECTION CONSIDERATIONS
• Protea infUtration surface during constraction.
• Vegetation of pond sides to prevent erosion.
• Frequent inspection POT clogging during constraction.
Targeted Constituents
# Sediment
O Nutrients
# Heavy Metals
9 Toxic Materials
# Floatable Materials
9 Oxygen Demand-
ing Substances
# Oil & Grease
# Bacteria & Viruses
W Ukely to Have
Significant Impact
O Probable Low or Unknown Impaet
Implementation
Requirements
d Capital Costs
O O^AT Costs
Q Maintenance
O Training
High O Low
TC1
Best'
Management
Practices^
Industrial Handbook 5-3 March, 1993
BMP: INFILTRATION (Continue)
MAINTENANCE REQUIREMENTS " ~ —
• Frequent deaning of porous pavements.
• Maintenance is difficult and cosdy fOT underground ttenches.
COST CONSIDERATIONS
• Potential for high maintenance costs due to clo'oinc.
Indastrial Handbook 5-4
TCI
Pne<lGM\
March, 1993
I
I
Additional Information — infiltration
Offneml Informntion
Where conditions are suitable infilttation systems may be Oie preferred choice because storm water is placed into tiie
ground tiiereby redudng excess mnoff and providing groundwater recharge.
InfUttation systems include:
Infilttation basin which is an open surface pond or underground vault (Figure lA)
InfUttation trendi wbich is an underground chamber filled widi rock, also called a rock weU (Figure IB).
Dry weU or "vertical" infiltration trench (Figure IC)
Porous pavement botii asphalt and concrete (Figure ID).
Concrete grid and modular pavement which are lattice grid sttuctures witii grassed, pervrous material placed in die
openings (Figure IE).
»
Infilttation basins are generally used for areas less tiian five aaes but can handle ttibutary areas up to 50 acres if tiie soil
is very permeable. Tbe other systems are smtable only for small sites of a few acres. Porous pavement and concrete
grids should only be. used in low ttaffic areas lUce parking areas. Smdies have shown tiiat porous pavement is sttong and
wUl last as tong as conventional pavement (Field, et al 1982; Gburek and Urtm, 1980). Experience in Rorida and
Maryland indicates tiiat concrete porous pavement performs better tiian porous asphalt Porous pavements and under-
ground fadlities may be favored at industrial sites where land is aUeady needed for business activities.
InfUttation systems should be considered where dissolved pollutants are of concem. However, satisfactory removal
effidencies require soils tiiat contain loam. Coarse soUs are not effective at removing dissolved poUutants and fine
particulates before the storm water reaches the ground water aquifer.
Local jurisdictions may not feel that infUttation systems are appropriate on industtial sites where spills of hazardous
chemicals can occur. However, spill conuol procedures may provide satisfaaory conuol (Chapter 4). Care should be
taken when considering tiie multiple objectives of using infilttation systems for water quality tteattnent ground water
recharge, and flood controL Infilttation basins, ttenches, and porous pavement can meet storm water detention require-
ments.
Three concerns witii infUttation systems are dogging, accumukition of metals, and ground water conuimination.
InfUtration systems have been used successfully on sandy soik in tiie Cenual VaUey of Califomia and Long Island, New
York for many years witiiout operational problems. In botii instances tiie primary objectives are ground water recharge
and flood control, not water quaUty tteatment
Problems can be expected witii infilttation systems placed in fmer soils. The Suite of Maryland bas emphasized tiiese
systems for about 10 years where tiiey have been installed in soUs witii infilttation rates as low as 027 inches per hour.
A recent survey (Lindsey, et al., 1991) found tiiat a itaid of tiie fadlities examined (177) were clogged and anotiier 18%
were experiendng slow infilttation. Dry wells that tteat roof ranoff had tiie fewest failures (4%) and porous pavement
tiie most (77%). Dry weUs may have tiie lowest CaUure rate because tiiey only handle roof ranoff. The primary causes
of failure appear to be inadequate pretteattnent and lack of soU stabUization in tiie ttibutary watershed, as well as poor
constraction practices (Shaver, pers. conun.). Erosion of tiie slc^s of infUttation ponds was a significant problem in
almost half tiic fadUties surveyed. Problems have occurred in die Centtal VaUey witii facUities placed on finer soik, as
in tiic case of Modesto. (Tultoch, pers. comm.).
Based on a review of several smdies of infiltration fadUties in sandy and loamy soik concluded that "monitoring ... has
not demonstiated significant contamination... altiiough highly soluble pollutants such as ninate and chloride have been
shown to migrate to ground water" (USEPA, 1991). However, poUution has been found m ground water wbere infUtta-
tion devices are in coarse gravels (Adophson, 1989; MUler, 1987).
Industrial Handbook 5 - 5 March, 1993
Additional Information — infiltration
Site Seleaion Considemtions (infUttation basin)
• Recommended minimum preconstraction infUtration rates bave ranged from 0.25 to 4 inches per hour.
• One state (Ecology, 1992) has specified a maximum clay content (30%) and a minimum cation exchange capadty
(5 meq).
• Not less tiian three feet separation firom seasonal high ground water, much greater distance if soik are very coarse.
• Avoid Steep (25%) slopes or otiier geologic conditions tiiat would be made unsttible by the infUttating water.
• Not less tiian four feet separation from bedrtxrk.
• Impaa on local groundwater including recharge potential water quality, etc.
Stahre and Urbonas (1988) bave presented a site selection procedure, if tiie site first passes tiie above criteria. Presented
in Table lA is a point system. If the site receives less tiian 20 points it is considered unsuiuible; more tiian 30 points is
considered excellent Thk procedure is used tq enhance infilttation perfonnance and minimize clogging.
Design
Thc degree of treatment achieved by infiltration k a function of tiie amount of storm water tiiat is captured and infU-
trated over time. This relationship for various areas in Califomia is shown in Appendix D. The figures in Appendix D
were developed using die hydrological model STORM.
The procedure to detennine die volume of infiltration basin is as follows: (1) select the appropriate figure in Appendix
D; (2) detennine for the catchment tbe percenttige of impervious area directiy connected to tbe storm drain system; (3)
choose a capoire goal, and read the required unit basin storage (acre-ft per acre) required for thc infiltration basin (to
provide perfonnance simUar to tiie otiier treattnent conttol BMPs in Chapter 5, a reasonable capture goal for infUtration
systems is 80%.); (4) multiply this unit figure times tiie total acreage of tbe catchment and convert to cubic feet When
using tiie above approach to size an infiltration ttench, remember to increase die volume of tbe trench to account for tiie
rode.
To calculate tbe minimum surface area of tiie infiltration system obtain tbe infiltration rate at the site using appropriate
techniques. Thk value k Uien used in tiie foUowing equations:
^m = V/D. m (1)
wbere: A
V
D
m
m
= minimum area required (ft^)
= volume of the infUttation basin (ft^)
= maximum allowable basin deptii (ft)
The maximum allowable depth is determined from tiie equation:
Dm = 40yi2S (2)
where: I = site infiltration rate in inches per hour
S = safety faaOT
The safety factOT accounts for the uncertainty of whetiier the infiltration test measures die real infiltration rate. Recom-
mendations have ranged firom 2 to 10 (consult your local SoU Conservation Service Office). The coeffident of 40
refers to the recommended drawdown time in hours. Thk k a reasonable drawdown time, given tiiat the average time
between stotms during tiie wet season in Califomia k on tiae order of 200 hours, except in Northem Califomia where it
is about 80 hours. A longer drawdown time may cause anaerobic conditions in tiie underlying soil or tiie production of
algae during die warmer montiis tiiat wodd clog the soU. A shorter drawdovm time reduces thc volume of the fadlity.
but increases the required surface area. Appendbc D contains figures for two drawdown times: 24 and 40 hours. In
most of the State, reducing the drawdown time does not significantiy reduce the volume.
Industrial Handbook 5-6 March, 1993
Additional Information — infiltration
Suggested references on tiie design of porous pavement include Maryland (1984) and Florida (1988).
Additional design considerations
For basins and ttenches, pretteat tiie storm water to remove tiie floatables and settleable soUds, particulariy when
pladng tiiese systems in finer soils. Pretteattnent can be accomplkhed with any of tbe otber treatment conool
BMPs in thk handbook.
Communities and CalTrans bave used infiltration systems in tiie Centtal VaUey for more tiian two decades witiioul
pretreatment Clogging has not been a problem with well maintained systems discharging to sands and courser soik,
suggesting tiiat pretteattnent k of limited value. Pretteatmcnt when infiltrating to finer soUs is suggested by tiie
experience of Maryland described previously. An infilttation fadlity sized only for ffeaonent is much smaUer tiian one
sized for flood connol and tiierefore may be more susceptible to clogging. Communities in tiie Central Valley (Fresno,
Modesto) require a retention volume that captures tiie 100 year event or about 20,000 ft^ per impervious ttibuttury acre.
In comparison, above Equation (1) wiU provide a volume in the range of 2,000 ft^ per impervious acre.
For small systems treating less tiian a few acres of pavement pretteattnent can bc accompUshed with a Type 2 catch
basin and a subpierged outiet The diameter and deptii of tiie sump should be at least four times die diameter of tiie
oudet pipe to die infiltration system (Lager, et al.. 1977). See Figure IC. The cateh basin cover should be steadied
"dump no waste". Vegetated biofilters can also be used altiiough they wUl not likely be feasible in industtial sites
which tend to be fuUy utilized.
Additional design considerations for basins include:
Do not locate on fdl sites, or on or near steep slopes
Energy dissipation at inlet to minimize erosion
Vegetate tiie slopes for tiie same reason
Vegetate tiie IxHtom to reduce tendency to clog with fmes
Freeboard of 1 foot
Side slopes of at least 3:1 for safay, and for ease of mowing (4:1 slopes are prefered)
Incorporate bypass or overflow for large events
Provide dedicated access to the basin bottom (minimum 4:1) for maintenance vehicles
Vegetating the slopes and bottom will bc difficult unless tiie facUity can be irrigated during the summer. Drought
tolerant ground cover spedes may be more suitable. See TC4 Biofilters for recommended species.
Additional design considerations for atrnches include:
Do not locate on fill sites, or on or near steep slopes
A 4 inch or 6 inch diameter observation weU witii locking cap, to check for loss of infilttative capadty
6 inch sand layer or geofabric at tbe bottom
Geofabric around uench walk to prevent soik from migrating into the trench rock mattix
(jcofabric 12 inches below ground surface witii 3/4 rock placed on top. which serves as filter for coaise soUds
Backfdl and filter rock should be clean washed aggregate 1 inch to 3 inches diameter
Incorporate bypass or overflow fOT large events
Provide dedicated access for maintenance vehicles
FOT porous pavement experience in Maryland suggest tbat asphalt pavement has continuous plugging problems and a
limited Ufe. Frequent maintenance k required. For drywells where access for maintenance is difficult if not 'unpossible
pretreattnent of tiie storm water k highly recommended. Such pretreatment may include biofilters, sumps, etc. Consul-
tation witii tiie local jurisdiction regarding the design of dryweUs is required.
Industrial Handbook 5-7 March, 1993
Additional Information — Infiltration
Constniaion
It k very important to protect tbe namral infUttation rate by using Ught equipment and constraction procedures dial
minimize compaction. Storm water must not be allowed to enter the facUity untU all consttuction in tiie catehment area
is completed and the drainage area k stabilized. If thk prohibition k not feasible in paiticukir situations, do not excavate
tbe faciUty to final grade untU after all constmction k complete upstteam. Leave one foot of native soU in Uie basin
which can be removed in layers as it clogs. Disking tbe surface frequendy during tiik period may be benefidal. After
final grading die fmal surface should also be disked. WiUi ttenches, make sure die rock fiU does not become diny whUe
temporarily stored at thc site.
The local jurisdiction may also specify tiiat the infUttation rate of the fadlity be witiiin a certain percentage of tiie
preconsttuction rate before tbe facUity is approved or accepted.
Maintenance «
Inspect the faciUty at least annually and after extreme events. If tiiere is stiU water in the pond or u^ncb 72 hours after a
storm it k time to clean tiie CadUty. A concem is restrictions on tbe disposal of tiie sediment removed from an infiltta-
tion basin due to contamination. Limited studies suggest tiiat tiik is not a problem, particularly if source-control BMPs
are effective. The Fresno MetropoUtan Flood Conuol Dkttia found noticeable accumulation of poUuttmts in tiie surface
layer in infUtration basins tiiat bad not been cleaned for about 20 years although the levels were stiU below toxic tiiresh-
olds. Tbe basins are now cleaned at least once every three years. Linuted studies of the bottom sediments in wet and
extended detention ponds indicate tiiat toxicity limits specified by final disposal regulations are not exceeded (see TC2
Wet Ponds).
Pretteatmcnt may reduce maintenance costs by capturing gross settieable soUds and floatables in a smaller space tiiat can
be more easily cleaned. Maintenance techniques for basins include rotoUlUng, disking and deep ripping.
Porous pavement should be cleaned at least quarterly by vacuum sweeping and high pressure washing.
Sec Maryland (1984) and Rorida (1988) for additional guidance on the design, consttuction, and
maintenance of infiltration systems.
REFERENCES
Adolphson Associates, 1991, "Subsurface Storm Water Dkposal FacUities", Interim Report for tiie Tacoma-Pierce
County Health Department
Adolphson Assodates, 1989, "Storm Water Evaluation. Clover/Chambers Basin Ground Water Management Program"
for the Tacoma-Pierce County Health Department
Field, R. H. Masters, and M. Singer, 1982, "Stattis of Poras Pavement Research", Water Resources Research, 16, 849.
Florida (Suite oO. 1988, "Thc Florida Development Manual", Department of Environmenuti Regulation.
Goforth, GF., JP. Heaney, and W.C. Huber. 1983, "Comparison of Basin Perfomiance Modeling Techniques". Jour.
EE, ASCE, 109(5), 1082.
Gburek, W. J, and J£. Urban, 1980, "Storm Water Detention and Ground water Recharge Using Porous Asphalt - Initial
Results", in Proceedings of Intemational Symposium on Urban Storm Water Runoff, Lexington, Kenmcky.
King County, 1990, "Surface Watti Design Manual". King County Washington.
Industrial Handbook 5-8 March, 1993
Additional Information — infinration
Lmdsey, G., L. Roberts, and W. Page, 1991. "Stonnwater Management InfUttation Practices in Maryland: A Second
Survey". Maryland Department of the Environment
Maryland (State of), 1984, "Standanls and Specifications fOT Infilttation Practices", Department of Nattiral Resources.
MettopoUtan Washmgton CouncU of Governments (MWCOG). March. 199Z "A Cunent Assessment of Urtian Best
Managemenl Practices: Techmques fOT Reducing Nonpoint Source PoUutioo in tiie Coastal Zone".
MiUer, S., 1987, "Urban Runoff QuaUty and Ivlanagcment in Spokane" in Proceedings of tiie Northwest Nonpoint Source
PoUutioa Cooference, March 24-25, Seattle.
Portland Cement Pervious Pavement Manual.* Florida Concrete Products Association, Uic 649 Vassar Sfreet Oriando,
Florida, 32804 (no date).
Schueler, TJL, 1987, "ConfroUing Urban Runoff: A Practical Manual fOT Plannmg and Designing Urban BMPs". Metto-
poUtan Washington Coundl of Governments.
Shaver. E., pers. cOTnm., State of Delaware Departtnent of Nattiral Resources.
Stahre, P. and Urtx>nas, B., 1989. "Swedkh Approach to frifdttation and Percolation Design", m Design of Urijan Runoff
(JuaUty ControL Americans Sodety of CivU Engineers.
Tulloch, AUce, pers. comm.. City of Modesto E*ubUc Works.
United States Environmental Protection Agency (USEPA), 1991, "Detention and Retention Effects on CJroundwater",
Region V.
Indusfrial Handbook 5-9 March, 1993
Additional Information — Infiltration
TABLE lA. POINT SYSTEM FOR EVALUATING INFILTRATION STIES
1. Ratio between tribuuuy connected impervious area (AJMP) and die infiltration area (AINF):
• AINF>2AIMP
20 points
• AIMP< AINF<2 AIMP
10 points
• 0.5 AIMP < AINF < AIMP
5 points
2. Nattire of surface soU layer
• Course soik witii low ratio of OTganic material
7 points »
• Nonnal humus soil
5 points
• Fme grained soik with high ratio of organic material
0 points
3. Underlaying soUs:
• If the underlaying soik are courser tiian surface soil assign tiie same number of points as for the
surface sou layer assigned under item 2 above.
• If the underlaying soik are finer grained tiian tiie smface soUs, use the following points:
• Gravel sand of glacial tiU witii gravel or sand
7 points
• SUty sand or loam
5 points
• Hne sUt or day
0 points
4. Slope (S) of thc infilttation surface:
• S < 0.07 ft/ft
5 points
• 0.07 < S < 0.20 ft/ft
3 points
• S > 0.20 ft/ft
0 points
5. Vegeuition coven
• Healtiiy natural vegetation cover
5 points
• Lawn is well esuiblished
3 points
• Lawn is new
0 points
• No vegetation, bare ground
-5 points
6. Degree of traffic on infilttation surface:
• Litde foot ttaffic
5 points
• Average foot tiaffic (paik, lawn)
3 points
• Much foot traffic (playing fields)
0 points
Industrial Handbook 5-10 March, 1993
Additional Information — infiltration
Top View
Riprap*
Outtall \
Protection
\
Side View
' Exiiliralion Storage ( Slopa
mmm Back-up Underdrain Pipe in Case ol Standing Water Problems
Source: Schuelef (1987)
NOTE:
1. Backup underdrain is not used in most appfications because plugging
occurs in soil above the drain.
2. An infiltration basin can also be excavated (typically 2 to 6 feet deep)
as long as the bottom of the basin Is 3 feet above high seasonal water table.
FIGURE lA. INFILTRATION BASIN
Industrial Handbook 5-11 March, 1993
Additional Information — infiltration
Top View
Grass Filter Intlow
MEDIAN STRIP DESK3N
Side View
20* Grass Filter Strio
Permeable Filter
Fabric One Foot
Below Surface.
Traps Debris
Screened Overflow Pipe
WaSSZ^^iM. or Permeable Filter
Sides Lined with Penneable Filter Fabnc
^J^o.-^2a jjUciean Washed Stone or Gravel
»'QS{*%'' ^ (1.5-3.0 Inch)
Cloth Lines Bottom
Source: Schueler (1987)
BUILOING DRAIN OESIGN
AaJt,
Adapted from King C^rrty
Levei
•Perforated Pipe
Screen CB Sump with
SoikJ Ud -Optionai
FIGURE IB. INFILTRATION TRENCHES
Industrial Elandbook 5-12 March, 1993
Additional Information — infiltration
y-ci
JL
goo« 2.-
48" 10 Pr-cast aonnole Bottom .
Perforoted UonBole laied ajjinown —
-itft 1 1/2" lo i" woahea cfroin Rock
Montioit has opcfl bottom
m ov«r-«»eovol»d or«a with drain rock •
WITH PRETREATMENT
\1
Concrete >><lonnoi« g'-O" ^ian^ol« to oe •erforoteti 'n oreo of Oram Aocw
\
— "op ot Orctn r^ocK
•'-OV,— I 'o 3" "Oshsd Oroin Soc»
y PVC collection pipe, drill
i/*' notes a 2" etc, top ol pioe
H-."
Source: Adolphson, 1991
Side View
Source: Schueler, 1987
Note: See discussion on page 5-6 regarding design considerations.
WTTHOUT PRETREATMENT
FIGURE IC. DRYWELL CONFIGURATIONS
Industrial Handbook 5-13 March, 1993
5^
-1 n tr
^^iii(^iiiy|[fifeniiMiii%»ii^'i^
^IIISl|iSll@llieillSHir^lil^lllsWeipf^Tfeiir^
POROUS ASPHALT SURFACE COURSE
1/2" to 3/4" Aggregate
asphaltic mix
2.5 to 4" thickness lyplcdl
FirTrR"l:WsT
1/2" Aggretdte
2" Thickness
A RESERVOIR BASE COURSE
l"'lo 2" Aggregate
Voids volume is designed tor
runoff Retention
Thickness is basml on storage
required
EXISTING SOIL
Minimal compaction to retain
porosity and permeability
Source: Cily of Rockville, Maryland
FIGURE ID. POROUS ASPHALT PAVING TYPICAL SI^CI ION
>
Q.
Q.
o'
SL 5" —**
o —t
3
o*
3
3. I
5"
Additional Information — infiltration
Poured-In-Place Slab Castellated Unic
Lattice Unit Modular Unit
Source: State of Florida
FIGURE IE. TYPES OF GRID AND MODULAR PAVEMENTS
Industrial Handbook 5-15 March, 1993
BMP: WET PONDS Considerations
Soils
djrea Required^
Water Availability
Aesthetics
Hydraulic Head
( Environmental Side\
Effects
DESCRIPTION
A wet pond has a pennanent water pool to tteiat incoming storm water An enhanced wet
pond includes a pretteattnent sediment forebay
CALIFORNU EXPERIENCE
There are regioiial flood contttil basins in California tiiat function Uke wet ponds or
constructed wetiands (TC3).
SELECTION CRITERIA
• Need to achieve high level of particulate and some dissolved conuuninant removal.
• Ideal for large, regional ttibutary areas.
• Multiple benefits of passive recreation (e.g., bird watehing, wUdUfe habitat).
LIMITATIONS
• Concern for mosquitoes and maintaining oxygen in ponds.
• Cannot be placed on steep unsttible slopes.
• Need base flow or supplemental water if water level is to be maintained.
• Infeasible in very dense urban areas.
• In California the wet season k coinddent witii minimal pbnt growth.
• Could be regulated as a wetlands or under Chapter 15, Tide 23, Califomia Code of
Regulations regarding waste disposal to lands.
• PencUng volume and deptb, pond designs may require approval from State Division of
Safety of Dams.
DESIGN AND SIZING CONSIDERATIONS
• Wet pool volume detennined by Figures 2B and C.
• Water deptii of 3 to 9 fecL
• Wetiand vegetation, occupying 25-50% of water surface area.
• Design to minimize short-circuiting.
• Bypass storms greater than two year storm.
CONSTRUCTION/INSPECTION CONSIDERATIONS
• Be careful when instaUing wetland vegetation.
MAINTENANCE REQUIREMENTS
• Remove floatiibles and setUment buUd-up.
• Coned erosion spots in banks.
• Conttvl mosquitoes.
• May require permits from various regulatory agendes, e.g. Corps of Engineers.
COST CONSIDERATIONS
• Costs for providing sutylemental water may be prohibitive.
Targeted Constituents
9 Sediment
O Nutrients
O Heavy Metals
Q Toxic Materials
9 Floatable Materials
9 Oxygen Demand-
ing Substances
Q Oil & Grease
O Bacteria & Viruses
# Ukely to Have
Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
# Capital Costs
Q O&M Costs
Q Maintenance
O Training
High O Low
TC2
Best^
Management
Practices^
Industrial Handbook 5-16 March, 1993
Additional Information — wet Ponds
General
The major feamres of a wet pond are shown in Figure 2A. Il k essentially a smaU lake witii rooted wetland vegetation
along the perimeter. The pennanent pool of water provides a quiescent volume for continued settUng of particulate
contaminants and uptake of dissolved contaminants by aquatic plants between storms. The wetland vegetation is present
to improve tbe removal of dissolved contaminants and to reduce die fonnation of algal mats. However, given tiie need to
minimize thc impaa on space, it may be cost-effective to use vertical concrete retaining walk which would not aUow for
emergent vegetation.
The average depdi of die wel pool k generaUy 3 to 9 feet, although greater deptiis are possible witii artificial mixing. Tbe
objective k to avoid tiicrmal stratification tbat could result in odor problems. Gentie artifidal mixing may be neecfcd in
small ponds because tibey are effectively sheltered from tbe wind.
In industrial appUcations ground water or treated process water wUl have to be pumped mto tiie fadUty to maintain tiie
water level. The wet pond could be aUowed to dry during die summer montiis. Allowing tiie wet pond to dry has not
been tried elsewhere bul seems feasible since tiie pond need not operate during die summer months. The major problem
with tiik concept wiU likely be aesthetics ratiier than perfonnance.
Wet ponds are of interest where the removal of tiie dissolved constiment fraction is of concern, particularly nutrients and
metals. Dissolved contaminants are removed by a combination of processes: physical adsorption to bottom sedunents
and suspended fme sedinoents, natural chemical flocculation, and uptake by aquatic plants. A wet pond witb concrete
sides and floor would therefore not Ukely provide any advanttige over the non-vegetative treatment control BMPs. The
relative importance of each mechanism is not weU understood. Very limited data prevents a definitive conclusion as to
the effectiveness of wet ponds m removing dksolved conuuninants. Reduction in tiie dksolved fraction of phosphorus
and some metals have been observed but this does not necessarily mean it k removed in tiie pond. It may be incorpo-
rated into algae or absorbed onto fme paniculate matter which exits tiie facUity in the effluent If tiie primary removal
mecfaankm is biologk:al, wet ponds may not be particulariy effective in removing dissolved contaminants in California
because most storms occur during winter when plant growth is minimaL
Another concept k the extended detention wet pond in which the oudet of tiie fadUty k restricted so as to retain a
treattnent design stoim on top of the wet pool for a specified time. It k beUeved thk added measure improves perfor-
mance. The effect of restricting thc outflow is to reduce die overflow rate during tiic storm increasing thc capttire of
settleable soUds. However, tiie majority of settUng occurs between ratiier than during the stonns. The extended deten-
tion zone may tiierefore provide Uttie incremental benefit If vertical space is available die concept could bc employed
because tiie added cost may be nominal. See TC5 Extended Detention Basins on how to determine thc extended deten-
tion volume.
Design
Two methods have been proposed for the sizing of wet ponds: one predicated on tiie removal of particulate contaminanis
only (USEPA, 1986) and one predicated on die removal of phosphoras as weU (Florida, 1988; Maryland, 1986). The
first mediod relates die removal efficiency of suspended soUds to pond volume. The second method provides a detention
time of 14 days based on tiic wettest montii to allow suffident time for die uptake of dissolved phosphorus by algae and
die settiing of fine soUds where die particukite phosphorus tends to bc concenttated. The criterion of 14 days comes from
Kast et aL, 1983 who observed dial in lakes at least 14 days is needed fot significant algal growdi during die growing
season. In much of die United States mcluding Maryland and Florida die growing season k coinddent with significant
rainfall But tius k not tbe sittiation in California where essentiaUy all of tiic rainfall occurs firom November tiirough
AprU. Consequentiy, the removal of phosphorus and fme solids wUl not be as high as thc literature indicales.
Industrial Handbook 5-17 March, 1993
Additional Information — wet Ponds
•Si7inp tha Permanent Pool
Figure 2B shows die relationship between perfonnance and tiie long-term removal effidency for average conditions in
C^omia (USEPA (1986) as adapted in FHWA (1989)). Vi/Vj- k tiie ratio of tiie volume of tiie wet pond to die volume
of tiie runoff of tiie mean storm event from tiie ttibutary watershed. The depth of tiie mean storm for various areas of
CalUomia is shown in Figure 2C. Tbe recommended perfonnance goal is 80%. The volume of die pond k tiierefore
calculated as follows:
Vb = 3SciAi 43560/12 =10890SdAj (D
where: V^ = pond volume (ft^)
Sd = mean storm deptii (inches)
Aj = impervious acres in die tributary watershed
For Aj tiie engineer may use directiy connected impervious acres because it more conecdy represents die area being
tteated and would aUow a smaller facUity. Although impervious area and directiy connected impervious area are not tiie
same, tiiey are reasonable given tiie uncertainty of die methodology and expected pond performance.
Thk volume should be compared witii tiie 14 days detention time criterion and tiie more conservative volume (i.e., larger
volume) should be used for sizing.
Adding Detention Storage to tiie Permanent Pool
Some investigators beUeve tiiat detention volume added above tiie permanent pool enhances pool performance. Tbe
State of Flaida, for example, requUes one basin inch of detention storage be added to tiie pennanent pool and be bled
down over a 60 hour period. This requirement, however, adds considerably to tiie size of tiie basm, and tiie Uterature
docs not indicate dial water quaUty performance k improved. Therefore detention storage should bc added only if tiie
pond k to be used for drainage control in addition to water quality controL As with extended detention, consideration
should be given to bypassing tiie fadUty for flows greater tiian tiie two year storm so tiiat bed load is not napped in die
pond.
A perforated riser oudet recoinmended by titie Denver Urban Drainage and Flood Contttil Dkuicts k iUusttated in
Figures 2D and 2E. Otiier outiet concepts are Ulustrated in TCS, Extended Detention Basins, Figure 5B.
Additional Considerations
Place wetland vegetation around tbe pond perimeter and near tbe oudeL
Rooted vegetation around the pond perimeter serves several functions (Figure 2A). It enhances tiie removal of dissolved
poUutank (sec T3, Constructed Wetiands); it may reduce die fonnation of floating algal mats; it reduces the risk of
people faUing into tiic deeper areas of tiie pond; and, it provides some habitat for insects, aquatic life, and wetland
wildlife. The "sheir for tiic vegetation should bc about 10 feet wide with a water deptii of 1 to 2 feet The total area of
the "shclT sbodd bc 25-50% of tiie water surface area. Vegetation near tiie exit wUl assist settiing of solids. An
alternative k a rock fUtcr which k used in many wastewater oxidation ponds where loss of algae in tiie effluent is a
common problem during die growth season (Rich, L., 1988).
If mesquites are of particular concern, it would be advisable to inhibit tiie growtii of emergent wedand vegetation around
the perimeter by using steep slc^>es, say, 2:1, and by minimizing the ainount of pond area tiiat has a deptb less tiian 18".
Gambusia (mosquito fish) can also be planted in larger ponds but die water level must be maintained to insure tiieir
survival during die dry season.
Industrial Handbook 5 - 18 March, 1993
Additional Information — wet Ponds
If placement of wetiand vegetation along tbe perimeter k not feasible consider tbe use of devices that retain non-iooted
wetiand spedes (Lunnion, undated; Zirschky, et al, 1980). Non-rooted vegetation k more effective tiian rooted vegeta-
tion in removing dissolved nutrients and metak (see TC3 Consttucted Wetiands). The vegetation grows witiun the
device which k periodicaUy removed and cleaned tiiereby removing tiie contaminants from the facUity. The system
developed by Limnion k in use in several artifidal lakes in CaUfomia to control nuttients.
• Except for very smaU faciUties, include a forebay to faciUtate maintenance.
Use side slopes of at least 2:1 or flatter unless vertical retaining waUs are used.
• Except for very smaU faciUties, provide access to tbe forebay (slope of 4:1 or less), to the outiet, and around tbe
pond perimeter for cleaning.
About 10 to 25% of the surface area determined in tbe above procedure should be devoted to the forebay. The forebay
can be dktinguished from tiic remainder of tiie pond by one of several means: a lateral siU witb rooted wedand vegeta-
tion, two ponds in series, differential pool depdi, rock-fiUed gabions or retaining wall or a horizontal rock fUter placed
lateraUy across the pond.
• Use energy dissipation at tiie inlet to avoid erosion, to {»t>mote settling in tiie forebay and to minimize short-
circuiting.
• Use a lengtii to width ratio of at least 3:1 to 'minimize short-circuiting.
Short circuiting must be minimized. Thk can bc accompUshed by using a generally rectangular configuration with a
lengtii to widtii ratio of a least 3:1 and by pladng the inlet and outiet at opposite ends. The inlet and outiet can bc placed
at die same end if baffling k instaUed to dfrect die water to the opposite end before rettuning to die oudet If topography
or aesthetics requires thc pond to have an irregular shape, the pond area and volume should bc increased to compensate
foi die dead spaces.
Inlet design may affect a facility's hydrauUc effidency. The ttaditional approach of deadheading die inlet pipe directiy
mto die pond is not satisfactory. Experience widi wastewater tteatment indicates dial it k best to have multiple inlets
spaced equal to tbe depdi of tiie pond, witii a perforated baffle kxated in front of die inlets at a dktance from one to two
times die pond depth (Kleinschmidt, 1961). However, thk concept k not practical with storm water tteatment systems.
A possible compromise that should significantiy reduce short-circuiting in which the flow is split by a T or Y
(Kleinschmidt 1961) witii tiie horizontal rock filter serving as perforated baffle. A lateral bench witii wedand vegetation
as shown in Figure 2A should ako work. The area between tiic inlet and die fdter becomes die forebay. Placing large
rocks at each inlet wUl dissipate the energy and spread tiie water more effectively across the forebay.
• Minimize water loss by infiltration through tiie pond bottom.
To mainttiin thc wet pool to the maximum extent possible excessive losses by mfUttation through tide bottom must bc
avoided. Dependuig on die soUs, tiiis can be accompUshed by compaction, incorporating day mto die soil or an
artificial Uner.
• Freeboard of 1 foot
• Witii earthen walls, place an antiseep collar around the oudet pipe.
• The oudet should incorporate an antivortex device if die fadlity is large (A 100 year storm must safely pass dirough
or around tbe device).
Thc settleable solids concentration of storai water is relatively low, obviating die need for adding depth to die facUity for
sedimenl storage.
Industrial Handbook ,5-19 March, 1993
Additional Information — wet ponds
The sides of an earthen waU should be vegetated to avoid erosion. Drought tolerant groundcover spedes should be used
if irrigation can not occur during the summer. SecTC4, BiofUters regarding recommended plant spedes.
Maintenance
Check at least annuaUy and after each extreme storm event The fadUty should bc cleaned of accumulated debris. The
banks of surface ponds should be checked and areas of erosion repaired. Remove nuisance wetiand species and take
^ropriate measures to conttol mosquitoes. Solids should be removed when 10 to 15% of the storage capadty has been
lost
Lunited sttidies (Dewberry and Davis, 1990; Meiorin, 1991; Florida, 1991; Livingstone, peis. comm.) of die bottom
sediments indicate that toxidty linuts specified by final disposal regulations are not exceeded. Concenttations observed
by Dewberry and Davk (1990) were less tiian 1/1000 of toxidty limits. If tiiis problem k occurring it suggests tiiat
source control BMPs need to be improved, i
If algal blOOTis are excessive consider alum tteatment or the use of devices tiiat retain non-rooted vegetation as dk-
cussed above.
REFERENCES
Dewberry and Davis Inc, 1990, "Investigation of Potential Sediment Toxicity from BMP Ponds", Nortiiem Virginia
Planning Dktrict Commission.
Rorida (State oO, 1988, "The Rorida Development Manual", Departtnent of Envfronmental Regulation.
Rorida (State oO, 1991, "Maintenance Guidelines for Accumulated Sediments in Retention/Detention Ponds Receivuig
Highway Runoff*. Department of Transportation.
Kleinschmidt SJL, 1961, "HydrauUc Design of Detention Tanks", J. Boston Sodety of Civil Engrs., 48,4.247.
Limnion Corporation, undated, "Nutrient Removal Using a Submersed Macrophyte System", and "Metals Removal
Using a Submersed Macrophyte System".
Maryland (State oO, 1986, "FeasibUity and Design of Wet Ponds to Achieve Water QuaUty Conttol", Water Resources
Adminkttation.
MettopoUtan Washington Coundl of (jovemments (MWCOG), March, 1992, "A Cunent Assessment of Urban Best
Management Practices: Techniques for Redudng Nonpoint Source Pollution m the Coastal Zone".
Rast W., R. Anne Jones, G. Fred Lee, 1983, "Predictive CapabUity of U.S. OECD Phosphorus Loading-Euttophication
Response Modek", J. Water PoUution Conttol Federation, 55,7,990.
Rkh, L, 1988, "A Critical Look at Rock FUters", J. of Envfr. Engr, Amer. Sodety of CivU Engrs, 114,219.
Shepp, D., D. Cole, and F. GalU, 1992, "A Field Survey of die Performance of Oil/Grit Separators", Metropolitan
Coundl of Governments.
United States Environmental Protection Agency, 1986, "Methodology for Analysk of Detention Basins for Conttxil of
Urban Runoff Quality".
Industrial Handbook 5-20 March, 1993
Additional Information — Wet Ponds
Urban Drainage and Rood Control Dktrict, Denver Colorado, "Urban Stotm Drainage Criteria Manual - Volume 3 - Best
Management Practices - Stormwater Quality", September 1992.
Waflcer, W., 1987, "Phosphorus Removal by Urban Runoff Detention Basins", in Lake and Reservofr
Management North American Sodety for Lake Management 314.
Zfrschky, J., and S. Reed, 1988, "The Use of Duckweed for Wastewater Treattnent", J. Water Pollution Conttol Federa-
tion, 60,1253.
I
I
Industrial Ebindbook 5-21 March, 1993
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FIGURE 2A. PLAN AND SECTION OF A WE F I»OND
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0.1 0.2 0.-4 0.6 O.B 1 2 -4 6 8 10
WET BASIN VOLUME / RUNOFr VOLUHE, V, / v
Sourcs: FHWA (1989)
FIGURE IB. TSS REMOVAL VERSUS V/VR RATIO
TC2
Industrial Handbook 5-23 March, 1993
Additional Information —wetPonds
0.60 0.50 0.40
0.40
Source: Woodward-Clyde, 1989
0.50
FIGURE 2C. AVERAGE STORM EVENT
DEPTH (INCHES)
Industrial Handbook 5-24 March, 1993
Additional Information — wet ponds
Thraadad Cas ^•movaola & Lodcasla
Ovarflow Grata for^
Larger Slorms
_2 I
•3 i O;
Q.
ID
Q
Detention Volume
Level
?artcrai9d Hoias
Abova Parmanant .°ool
Pannanaot Pod Uaval
Stiff Sta«l
Screery far
Trasn Skimmer
Pannanam Pod fls > 40 of Risar
Waiar Gualitv
Riser pip* (Saa Oatail)
Notas: 1. Altamata dasigns ara accaptabl* as long as Itw
riydrauiics pravidas 3^a rvquirad amtying tiin«s.
2. Usa Irash skimmar scraans oi stiif craan staal
matariai a protact partoratad ris«r. Must aztand
from fim top of tha nsar ID 2 It. balow iria
pannanant pool laval. OUTLET WORKS
NOTTOSCALc
Siza Sasa to Pravant
Hydrosaiic Upiitt
Notes: 1. Minimuni numbar of holes • 3
2. Minimum hde diameter • MS" Dia.
l-1/2*dtafTiet«rAir
Vent in Threaded Cap
Water Quality
Outlet Holes
Ductile Iron or
Steel P'ipe
WATER QUALrrV
RISER PIPE
NOT TO SCALE
(Used By Permission, UDFCD, 1992)
Maximum Numbar of Parloratad Columns
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FIGURE 2D. WATER QUALITY OUTLET
FOR A WET POND
Industrial Handbook 5-25 March, 1993
Additional Information — wet ponds
0.2 0.4 0.5 0.8 1.0 2.0 4.0 6.0 8.0 10
R«qiiir«d Ar«a par Row (in.^)
Souroe: Douglas County Stonn Drainage and Technical Criteria. T986. (Used By Permission. UOF(^, 1992)
FIGURE 2E. WATER QUALITY OUTLET SIZING:
WET POND WITH A 12-HOUR DRAIN
TIME OF THE CAPTURE VOLUME
Industrial Handbook 5-26 March, 1993
BMP: CONSTRUCTED WETLANDS
FLOW
TREES
AQUATIC PLANTS
Considerations
Soils
^rea Required
Shpe
[Water Availability
Aesthetics
Hydraulic Head
^Environmental Skie\
DESCRIPTION *
Constructed wetlands bave a signiticant percentage of tiic fadUty covered by wetiland
vegetation.
EXPERIENCE IN CALIFORNU
Research faciUty constructed in Fremont in 1983 by the Association of Bay Area Govern-
ments. Several communities (Davis, Orange County) have regional detention ponds tbat
are essentiaUy constructed wetlands.
SELECTION CRITERIA
• Need to achieve high level of particulate and some dissolved contaminant removal.
• Ideal for large, regional tributary areas.
• Multiple benefits of passive recreation and wUdlife.
LIMITATIONS
• Concem for mosquitoes.
• Cannot be placed on steep unstable slopes.
• Need base flow to maintain water level.
• Not feasible in densely developed areas.
• Wet season coinddent with minimal plant growth.
• Nutrient release may occur during winter.
• Overgrowth can lead to reduced hydrauUc c^adty.
• Regulatory agendes may limit water quality to constnicted wetlands.
• May bc regulated under Chapter 15, Titie 23, CaUfornia Code of Regulations regard-
ing waste disposal to lands.
DESIGN AND SIZING CONSIDERATIONS
• Suitable soils for wedand vegetation.
• Surface area equal to at least 1 % and preferably 2% of die ttibutary watershed.
• Forebay.
CONSTRUCnONANSPECnON CONSIDERATIONS
• Invdve quaUfied wetland ecologist to design and instaU wetland vegetation.
• EstabUshing wetland vegetation may be difficult
MAINTENANCE REQUIREMENTS
• Remove foreign debris and sediment buUd-up.
Areas of bank erosion should be repaired.
• Remove nuisance species.
• Conttx)! mosquitoes.
Targeted Constituents
% Sediment
# Nutrients
# Heavy Metals
9 Toxic Materials
9 Fhatable Materials
9 Oxygen Demand-
ing Substances
# 0/7 & Grease
O Bacteria & Viruses
9 Ukely to Have
Significant Impact
O Probable Low or
Unknown Impaet
implementation
Requirements
# Capital Costs
Q O&M Costs
O Maintenance
O Training
High O Low
TC3
Best^
Management
P^actices^
Industrial Handbook 5-27 March, 1993
BMP: CONSTRUCTED WETLANDS (Continue)
COST CONSIDERATIONS
• Wetiands being shaUower than wet ponds may result in larger area requiremaits.
• Costs fot providing supplemental water may be prohibitive.
I
I Industrial Handbook 5-28 March, 1993
Additional Information — Constructed Wetlands
Ggneral Infonnation
Altiiough natural wetlands are being used to treat storm water, regulatory agendes do not favor this use, except as a final
"poUshing" step after tteattnent by one or more of the treatment control BMPs presented in this chapter. Consmicted
wetlands, in contrast are buUt specificaUy for treating stoim water runoff. Tbey are not wetlands created as mitigation
for the loss of natural wetlands. Consequentiy, there is no intention to repUcate the complete array of ecological func-
tions of a wetland (e.g., tbe presence of wildlife), altiiough it can be done. A constructed wetland is generaUy one of tbe
more aesthetic than tbe tteatment systems. It is Ukely dial constructed wetiands wUl bc used only in very large industiial
sites, but smaU faciUties witii concrete retaining waUs to conserve space wiU also likely be effective.
The simplest form of a constnicted wetland includes a rectangular basin with a fcxebay and wetiand vegetation area. Tbe
deeper forebay (3 to 6 feet) traps floatables and tiie larger settieable solids, faciUtating maintenance as weU as protecting
tiie wetland vegetation. Altematively, a detention pond may bc placed before tiie wetiand, to remove settieable soUds
and to protect the wetland from extreme inatases in water elevation. Thc wetland vegetation is placed in a shallow pool
dial extends laterally across the basin. Construction of low flow channels through emergent vegetation can cause storm
water to short cucuit through channels ratiier tiian tiirough the wetiand vegetation.
Placing rooted wetland spedes through the majority of tbe facUity adds to the cost in comparison to a wet pond. How-
ever, it is beUeved by many practitioners tbat tbe vegetation improves performance. Placing the vegetation across the
faciUty as Ulustrated in Rgure 3A improves settiing of particulates and uptake of dissolved contaminants. As tiie
constructed wetland is shaUower than a wet pond, there may be better contact between tbe water and soU which may be
the primary remover of dissolved phosphorus and metals.
The vegetation reduces tbe effect of wind wbich can cause significant sbort-cfrcuiting in a wet pond. Water loss in a
wetland may not bc greater and possibly less tiian a wet pond. Evapotranspiration from tiie plants wiU bc greater in a
wetland but ev^xnation from tiie water surface may be less because the dense vegetation eliminates the effect of tiie
wind. The net result may be a slower rate of water loss. Conceivably a constracted wetland could be made smaUer tiian
a wet pond, given the benefits of thc vegetation. But experience is too limited to identify how tiie size might be altered
from what is calculated for a wet pond.
Relying on volunteer plants to cover die vegetated area wiU delay complete coverage for several years and may allow die
invasion of undesirable spedes or dominance by one or two spedes such as cattails which tend to flourish in disturbed
conditions. Complexity is promoted by varying water depth tiirough the vegetated area rather than keeping the deptii
uniform. Preferred spedes to maximize thc removal of dissolved metals are SaUcomia pacifica (cadmium, copper and
lead), Justicia americana (copper), Potamogeton crispus (cadmium), Phragmites communis (zinc), Carex stricta (zinc),
and Scirpus lacusttis (zinc) (SUverman, 1982).
There is some question as to tbe incremental benefit of wetland vegetatioa in California, inasmuch as most of the wet
season occurs when thc vegetation is donnant The minimum desirable temperattire for caoaUs, sedges, and bulnisbes is
IQOC, 140C, and 16^0, respectively (USEPA, 1988). For most of California, mean temperatures during die winter
months are 5 to lO^C; along die south coast tiiey range from IQPC to 150C. The primary removal mechanisms fot
dissolved phosphtxus and metals are adsorption by the soU and use by non-rooted vegetation. Rooted vegetation obtains
nutrients ftom tbe soils, not firom tbe water, unless tiic vegetation is placed m graveL In contrast non-rooted vegetation
removes nutrients and metals from the water (Guntenspergen, et al., 1991). It can bc expected that soU adsorption wUl
continue during the winter to some extent Removal of metals and nutrients by non-rooted vegetation may not occur, or
wiU at least be significantiy reduced because of tbe lack of growth. In contrast loss wUl occur from vegetation die-off or
dormancy. Thc net effect over a 12 month period may be that a constructed wetiand is no more effective than a wet
pond, particukttly with regard to die removal of dissolved phosphorus and metals.
Industrial Handbook 5-29 March, 1993
Additional Information — Constructed Wetlands
The above concem is partiaUy confirmed by research at the experimental wetland/wet pond in Fremont (Meiorin, 1991).
The author states that tbe "uptake of nutrients ... was low because most stonns occurred in winter when plant growth was
reduced by ambient temperatures, short day lengths and low Ught levels". Despite the use of die word "low", phospho-
rus removal during tbe winter months was about 50% which is not noticeably better than removal in a wet pond. The
removal of nitrogen was negative. Resuspension of plant material and detritus also occurred during the winter.
Despite tiic concerns, tbe wetland bottom soUs are possibly a more significant mechanism for removing phosphorus and
metals. However, the experience with constructed wetlands treating wastewater seems to indicate phosphorus removal
occurs in the first two to three years Ixil tiien removal rates decrease dramaticaUy and have become negative in some
cases (FauUcncr and Richardson, 1991). This result appears to be due to samration of tite soU and tbe plants reaching
maximum density. However, metals removal may continue. Nittxigen removal does not degrade over time because it is
a bacteriological process. This process is very temperattire dependent and therefore would be expected to be lower in
tbe winter. *
Using gravel as tiie substtate may be a suitable ^proach in smaU fadUties. Because thc gravel is lacking in nutrients
certain emergent spedes wiU ttike diefr nuttients from tiie water (Thut 1988). See Reddy and Smith (1988). Harvesting
may also be more practical with this apptoach.
Of particular concem in many areas of Califomia wiU be mosquitoes. Thick stands of emergent vegetation provide an
ideal breeding habitat If Gambusia (mosquito fish) are introduced into die fadUty the design must include a deep pool
area where thc fish can reside during the dry season. Tbe forebay can serve this function.
.Design
In tiic most comprehensive review to date of wetiands tteating storm water, Stecker et al. (1992) found considerable
variation in tbe performance of 26 faciUties, botii natural and constmcted. AU were located on large watersheds witii
mixed land uses, not industrial sites. There appeared to bc no relationship between performance and the size (surface
area) of die wetland. Thc surface area of tiic ten constmcted wetlands varied from 03% to 12.6% of die ttibutary area.
The removals of suspended soUds and phosphorus ranged from 50 to 95% and 37 to 92%, respectively, for nine of die
10 fadUties. Thc smallest facUity removed 85% of die suspended solids and 37% of tiic phosphorus. The autiiors were
unable to relate thc variabiUty of performance to any factor of design or operation. Constmcted wetlands pcrfOTmed
somewhat better tiian natural wetlands. The only conclusion that might be safely drawn from this study is that a surface
area greater than about 1 or 2% of the tributary watershed is not justified, given the uncertainty of any unprovement in
perfonnance witii thc increase in size. Lacking, however, are data on thc percentage of each watershed that is impervi-
ous.
Thc CadUty can be sized using the same procedure outiined for Wet Ponds, TC2. However, inasmuch as a wetland is
shaUower than a wet pond, sizing thc wetland for the same Vj/Vj as a wet pond requires considerably more surface area.
Given tiic likely advantages of a constmcted wetland over a wet pond, scwnc may consider tiiis to bc an unreasonable
penalty. It is dierefore recommended diat surface area of die constmcted wetiland not exceed dial which would bc
detennined for a wet pond.
Additional design considerations include:
• Have 25% to 50% (fwebay and afterbay) 3 to 6 feet deep, and remaining area 6 in. to 24 in. deep or as appropriate
for die wetland species selected. This geometiy should provide satisfacttiry conditions for wedand wUdlife (Adams
etai., 1983).
• Side sk^pes of at least 4:1 to a water depdi of 2 feet except on very small fadlities where retaining waUs may be
used to conserve space. If retaining walls arc used, die area must be fenced for safety.
• Access for maintenance vehkrles to the forebay, thc outiet and around tiie perimeter.
Industrial Handbook 5-30 March, 1993
Additional Information — constructed wetiands
Freeboard of at least 1 foot
With earthen contained faciUties, instaU an antiseep coUar on the outiet pipe.
The soils must be suitable for wetiand vegetation. If necessary organic soils (18 to 24 in.) must be imported to tiie
site.
-The soU must have an affinity for phosphoms. SoUs with aluminum and iron are best Soils saturated with phos-
phorus or a metal spede may cause tiic concenttations of tiiese contaminants to increase in tiie overlying water.
Minumze sbort-cfrcuiting by pladng energy dissipators at tbe inlet and by having a high lengtii to width ratio.
Short circuiting must be minimized by using a generaUy rectangular configuration with a lengtii to width ratio of a least
3:1 and by pladng the inlet and outiet at opposite ends. The inlet and outiet can be placed at the same end if baffling
(islands) is instaUed to dfrect tiie water to the opposite end before retuming to tiie oudet If topography or aestiietics
requires the wetland to have an inegular shape, the pond area and volume should be increased to compensate for tbe
dead spaces. Energy dissipators and entranc^ baffles wiU spread tiie water lateraUy across tiie facUity.
Minimize water loss by infiltration through the wetland bottom.
Supplemental water may be needed to avoid loss of rooted vegetation during tiie dry period.
To maintain the wet pool to tiie maximum extent possible excessive losses by infUtration through tbe bottom must be
avoided. Depending on the soUs, tiiis can be accompUshed by compaction, incorporating clay into tiie soiL or an
artifidal Uner. Wetland vegetation species bave evolved to handle die sttess of seasonal variations in water avaUabiUty.
However, during die dry season there must be suffident water to avoid complete desiccation of plant roots. Conse-
quentiy, constmcted wetlands are infeasible in areas where tiiere is a lack of eitiier a baseflow or near-surface ground
water during thc dry season. Supplemental water such as pumped ground water and treated process wastewater may
have to bc used.
• A wetland ecologist sbodd prepare the planting design and specifications, and oversee the planting.
Constracted wetlands may not need antivortex and trash rack devices on thefr outiets Uke a wet pond because of the
rooted vegetation. Sec TC2, Wet Ponds regarding inlet design. Design concepts for outiet devices are discussed in TCS
Extended Detention Ponds. See Josselyn (1982) regarding wetiand plant considerations. Establishing wetiand vegeta-
tion initiaUy may be difficult and requfre multiple plantings.
Maintenance
• Check at least annuaUy and after each extreme storm event
• Remove accumulated fordgn debris.
• Repafr areas of stope erosion.
• Employ mosquito countermeasures as required by local authorities.
• Clean deposits fiom the forebay when a toss of capadty is significant probably every 3 to 5 years depending on tbe
land use (see TC2, Wet Ponds), ot when tiic concenttations of toxicants in the sediments are reaching a level of
concem.
There is some question as to whether annual harvesting of rooted vegetation is either practical or effective at reducing
seasonal losses of nutrients and prolonging tiie Ufe of the fadUty (USEPA,' 1988). The benefits of harvesting may depend
upon die wetland spede (Suzuki, T. el aL, 1991). Pladng rooted vegetation ui gravel beds rather than soU may make
harvesting practicaL If harvesting is to bc done, it should occur twice per season, in the early summer when nutrient
content in thc plant material is at its peak, and in the fall before plant dormancy. Given the significant role of the bottom
soU in removing metals and phosphorus its replacement may bc required, althou^ probably not more frequentiy tban
once every few decades. CHeaning thc forebay more frequendy is important as noted above.
Industrial Handbook 5-31 March, 1993
Additional Information — Constructed Wetlands
Another consideration is the regulatory impUcations of removing accumulated material from constracted wetlands. Do
such actions requfre a 404 or other permit? At present constracted wetlands are excluded firran tins requirement
(Rittdue, 1992).
REFERENCES
Adams, L., Dove LE., DJL. Lecdy, and T. Franklin., 1983, "Urban Wetiands fw Stoimwater Control and WUdlife
Enhancement - Analysis and Evaluation", Urban WUdlife Research Center, Columbia, Maryland.
Faulkner, S. and C. Richardson, 1991, "Physical and Chemical Characteristics of Freshwater Wetland SoUs", in Co^-
sttiided Wetlands for Wastewarw Trcatmwit ed. D. Hammer, Lewis PubUshers, 831 pp.
Guntenspergen, GJL, F. Steams, and JA. Kadlec, 1991, "Wetiand Vegetation", in Consttucted Wetiands for Wastewater
Treattnent, ed. D.A. Hammer, Lewis PubUsheri $31 pp.
Josselyn, M., 1982, "Wetiand Restoration and Enhancement in California", Instittite of Marine Resources, University of
California.
Kulzer, L, 1990, "Water Ptrflutioo Contrtri Aspects of Aquatic Plants", Munidpality of MettopoUtan Seattie.
Livingstone, E., pers. comnt, Rorida Department of Environmental Conservation.
Mekxui, E.C., 1991, Urban Runoff Treattnent in a Fresh/Brackish Water Marsh in Fremont Califomia", in Constructed
Wetiands for Wastewater Treattnent Ed. D. A. Hammcri Lewis PubUshers.
MettopoUtan Washfaigton Coundl of Govemments (MWCOG), March, 1992, "A Current Assessment of Urtian Best
Management Practices: Techniques fw Reducing Nonpoint Source Pdlution in die Coastal Zone".
Reddy, K, and W. Smith, 1987, Aquatic Plants for Water Treatment and Resource Recovery, MagnoUa Press.
RittdUe, S, 1992, letter to ILB. James, (Chairman of die Management Committee of die Santa Clara Valley Nonpoint
Source PoUution Conttnl Program.
SUverman, G, 1982, "Wetiands for OU and Grease ConttoF. Tech Memo. 87, Association of Bay Area Govemments.
Suziki, T., W.G-A Nissanka, and Y. Kurihara, 1991, "AmpUficatioo ofTotal Dry Matter, Nittngen and Phosphorus
Removal from Stands of Phragmites ausoaUs by Harvesting", m Constracted Wetiands for Wastewater Treattnent Ed.
D. A. Hammer, Lewis PuWishers.
Sttecker, E.W., JM. Kersnar, and ES>. DriscoU, 1992, "The Use of Wetiands for CoottoUuig Stonnwater PoUution" for
USEPA Region V.
Thut, R., 1988, "UtUization of Artifidal Marshes for Treattnent of Pulp MUI Effluents", in Consttucted Wetiands for
Wastewater Treattnent, Ed. D. Hammer, Lewis PubUshers.
United States Envfronmental Protection Agency (USEPA), 1988, "Consttucted Wetiands and Aquatic
Hant Systems for Munidpal Wastewater Treannenr, EPA 625/1-88-022.
Industrial Handbook 5-32 March, 1993
BMP: BIOFILTERS
FLOW
CHECK DM (optional)
Consideratk>ns
(^oils^
dl^ea Requir^^
<^h£e^
Carter Availabil^^
Aesthetics
Hydraulh Head
Environmental Side
Effects
DESCRIPTION »
Btofiltets are of two types: swale and strip. A swale is a vegetated channel that treats
concentrated flow. A strip tteats sheet flow and is placed paraUel to tbe contributing
surface.
EXPERIENCE IN CALIFORNIA
No biofilters specificaUy designed to treat storm water have been located. However,
insttmces of "biofUter by happenstance" exist in northem communities (Davis, Sacramento,
Turiock, Fresno) wbere storm water is discharged to a grassed area prior to an inlet or an
infiltration area.
SELECTION CRITERIA
• Comparable performance to wet ponds and constracted wetlands.
Lunited to treating a few acres.
AvailabUity of water during dry season.
LBVOTATIONS
• Poor perfomiance has occuned but tiiis appears to bc due to poor design.
• May bc limited to areas where summer iirigation is feasible.
• Can be difficult to maintain sheet flow in strips.
• Can be difficult to avoid chaimeUzation in swales.
• Cannot be placed on steep slope.
• Area required may make infeasible on industrial sites.
• Proper maintenance required to maintain health and density of vegetation.
DESIGN AND SIZING CONSIDERATIONS
Thc surface area is defined by Rgure 4A.
The minimum width for a swale is determined by Mannings Equation.
Minimum length of a strip is 10 feet
Thc longimdinal slope must not exceed 5%.
Use a flow spreadet and energy dissipator at the entrance of a swale.
Good soUs are important to adueve good vegetatioa cover.
CONSTRUCTION/INSPECTION CONSIDERATIONS
• Make sure soils are suitable for healtiiy vegetatioa.
• Level cross-sectioo and even longittidinal slope fot swales.
• Adiieve sheet flow widi strips.
Targeted Constituents
9 Sediment
Q Nutrients
O Heavy Metals
O Toxh Materials
O Fhatable Materials
O Oxygen Demand-
ing Substances
Q Oil& Grease
O Bacteria & Viruses
• Ukely to Have
Sigruficant Impact
O Prol)able Low or
Unkrwwn Impact
Implementation
Requirements
Q Capital Costs
Q O&M Costs
O MaintenarKe
O Training
High O Low
TC4
Best^
Management
Practices''
Industrial Handbook 5-33 March, 1993
Additional Information — eiofiiters
A biofilter swale is a vegetated channel tiiat tooks similar to, but is wider dian, a dittdi tiiat is sized only to ttansport
flow. The biofUter swale must bc wider to maintain low flow velodties and to keep tiic deptiii of tiie water below the
hdght of tiic vegetation up to a particular design event A filter sttip is placed along the edge of thc pavement (its fiUl
lengdi if possible). The pavement grade must bc such as to achieve sheet flow to the maTimnTin extent practical along
the strip.
Vegetated biofilters wiU likely see Umited appUcation fri mdusttial settings. Sttips are most suitable for parkfrig tots
which under this general pcnmi do not require consideration unless they drain to a drainage system tiiat also receives
ftows frwn tiie industrial activities of concern. Withfri tiic mdusttial site itself conditions are usuaUy not suitable for
locatuig a grassy area next to a paved area TypicaUy, die industrial area is paved w the jroperty Une. If die suirm
water passes tiirough a ditch ptiot to leaving tbe site it may be possible to widen die diteh frito a swale.
i
The perfomiance of biofilters is probably somewhat less tiian wet ponds and constracted wetiands because tiie latter
provide treatment both during and between storms. Some researcbers have observed poor performance, recommending
diefr use only in combuiation witii otiier treattnent control BMPs. However, most ficM research on swale perfonnance
has been conducted on grassed roadside dittdies. A swale must be wkJer than a traditional roadskJc ditch, to avoid
excessive flow velodties which topples tbe grass and causes chaimeUzation.
Thc swale bottom musl bc as level as possible; energy dissipation and a flow qireader should be placed at die enttance
to minnnize channeUzation. The pavement must be as level as possible along its boundary witii a biofilter sttip. Thc
pavement edge should be left clear, dial is, no curbs. Parkfrig staU btocks musl bc open to pass tiic flow as unbfridered
as possible. Use of curb cuts in curbs is not a satisfactory approach. Thc cuts charaieUze die water and can clog witii
debris. Thc performance of strips may bc compromised by die faUure to achieve sheet flow at the interface between
thc paved area and die strip.
Turf grass is tiic preferred vegetation. Figure 4B shows recommendations for seven spedes of ttirf grass and one
ground cover plant for various areas of CaUfomia (Youngner, ct al., 1962). More recent mformation fri tiiis regard is
also shown m Rgure 4C (CCAE, 1984). Turf grass wiU require summer frrigation to rcmafri active. Altiiough it has
not been ttied it may bc possible to aUow tiic grass to become donnant during tiie summer sfrice die biofilter is only fri
service during tiic wet season. Tbe biofUter could be frrigated bcgfrining fri October to bring it to a healtiiy condition
prior to tiic first stwms. Ground cover spedes suitable for a non-frrigatioo siOiatioo may work but it also has not been
tried. TTic soU must bc of a fertilUty and porosity dial aUows for healtiiy vcgetatirai. A porous soU also promotes
infilttadoD. See the references tiiat foUow for Agricultural Extensive pubUcations on effident water use by mrf
grasses.
If eroston of die swalc is of concem because of tiie difficulty of maniiafrung a good grass cover, consider die use of
concrete grids (see Infilttation Systems) or sfrnUar material. Anodier concept is to use ched: dams to divide die swak
frito a series of terraces, redudng die longittidinal slope to perhaps 1%, tiiereby reducing flow velodties.
Desiyn
Several metiiods have been proposed to size biofdters (Homer, 1988; FHWA, 1989; EEP, 1991; Tolhier, ct al., 1976).
However, information on die relationship between biofilter area and perfonnance is lacking for urban conditions.
Figure 4A uses tile mediod of Homer (1988) widi die 2-year stotm as die design event a slope of 3%, and a grass
hdght of 4 inches. A biofilter is sized to tteat aU stonns up to a parttoular design event Tbe design event can bc
relatively smaU because die aggregate of aU smaU events represents die majwity of pollutant mnoff. Research in
western Washuigton (Metto, 1992) found fliat a biofUter sized acconUng to diis tcchmque removed 80 percent of die
su^iendcd soUds and attached poUutants and 50% of die soluble zfric. It was not able to remove dissolved phoOThonis
or copper.
Industrial Handbook c -IA
^ ^ March, 1993
Additional Information — eiofmers
Rgure 4A is meant for guidaiKC only and should be used with caution in areas where predpitation varies greatiy
because of terrain.
The design engineer must determine tiie widtii of a swale using Manning's Equation and die 2-year rainfall intensity
(California, 1976) appropriate to the site. An "n" of 0.20 is recommended (Metro, 1992). The design engineer must also
calculate the peak flow of tiie 100-year event to detennine tiie deptii of a swale. Since a widtii using an "n" of 020 is
generally wider than what is required of a grass Uned channel, channel stabiUty sbodd not be of concem. It is generaUy
not necessary to have a bypass fw the extreme events because tbe minimmn width specification combined with the
relatively gende slope avoids excessive velocities. If erosion at extteme events is of concern, consider tiie above
concepts to minimize erosion.
The design engineer can make the swale wider tiian determined in tiie above step, witii a conesponding shortening of tiic
swale lengtii to obtain the same sur&ce area. »However, tiiere is a practical Umitation on how wide the swale can bc and
stiU bc able to spread die flow across tiic swale width. Splitting tiie flow into multiple inlets and/or pladng a flow
spreader near die storm mlet should bc fricorpwated mto die design. A concept tbat may work is to place a level 2"x
12" timber across the width of thc swale perhaps 10 feet firom die pipe outiet Place gravel between tiic outiet and tiie
timber, to within 2 inches w so of the top of the timber. Place large rock immediately near the oudet to dissipate die
flow energy; thc rock also may help distribute die flow. -The timber wiU function Uke a wefr. Row spreaders have seen
limited appUcation and thefr effect on performance bas not been evaluated.
The problem of spreading the flow across flic width of tiic swale may Until its use to tributary cau±ments of only a few
acres. Thc minimum width based on using Manning's Equation results in widths of 3 to 12 feet per acre of impervious
tributary surface, depending on tiie location and longitudinal slope.
A minimum length of 10 feet is reciMimended for biofUter sttips. Length here is defined as tiie measurement in the
direction of flow from the adjoining pavement Lengths of 20 to 50 feet have been recommended by most practitioners
perhaps because of the concern tiiat sbeet ftow cannot be maintained. Wherever room permits a lengtii greater tiian 10
feet should be used. The short lengtii is recommended in this handbook because space is at a premium at most existing
industrial sites: 10 feet should work satisfactory if good sheet flow is maintained and no obstructions such as curbs are
placed along thc pavement edge.
The type of strip discussed here is not to be confused with tbe natural vegetated buffer strip used in residential develop-
ments to separate tbe bousing from a stream or wetland. As the later type foUows the natural coatour ftow
channeUzation is mcxe likely and lengths of 75 to 150 feet are recommended.
The lengtii of pavement prior to tiie strip should not exceed a few hundred feet to avoid channelization of large aggre-
gates of ranoff along tbe pavement before it reaches the pavement edge. To avoid channelization, care must be taken
during constmction to make sure that tbe cross-section of thc InofUter is level and that its longittidinal slope is even.
Channelization wUl reduce the effective area of the biofilter used fw tteatment and may erode tiie grass because of
excessive velodties.
Maintenance
Thc CadUty should bc checked annuaUy for signs of erosion, vegetation loss, and channeUzation of the flow. The grass
shoukl be mowed when it reaches a hdght of 6 inches. /^Uowuig tiie grass to grow taUer may cause it to tiiin and
become less effective. The cUppings should bc removed.
Industrial Handbook 5-35 March, 1993
Additional Information — Biofiiters
REFERENCES
Califomia (State oO, 1976, "RainfaU Analysis for Drainage Design, Volume 3, Intensity-Duration-Frequency Curves",
BuUetin No. 195, Department of Water Resources.
CaUfomia Cooperative Agriculttiral Extension (CCAE), 1984, "Selecting tiic Best Turf Grass", Leaflet 2589.
CCAE, 1985, "Turfgrass Water Conservation", BuUetin 21405.
CCAE, 1991, "Effluent Water fw Turfgrass Irrigation", BuUetin 21500.
Federal Highway Admfrustration (FHWA), 1989, "Retention, Detention, and Overland Row for PoUutant Removal of
Highway Stormwater Runoff (Draft)", Report No. FHWA/RD-89/203.
Homer, RJL, 1988, "BiofUtration Systems for Storm Runoff Water (Quality Contttil", Washington State Department of
Ecology.
EEP, 1991, "Vegetated Buffer Sttip Designation Method Guidance ManuaT', Narragansctt Bay Project
Lager, J.A., W.G. Smith, and G. Tchobanoglous, 1977, "Catchbasin Technology Overview and
Assessment", USEPA 600/2-77-051.
Metropolitan Washington CouncU of Governments (MWCOG), March, 1992, "A Current Assessment of Urban Besl
Management Practices: Techniques fw Redudng Nonpoint Source PoUution in tiie Coastal Zone".
MunicipaUty of Mettt>poUtan Seattie, (Metro), 1992, "Pollutant Removal Effectiveness of a Designed Grassy Swale in
Mountiakc Terrace, Washmgton (Draft)".
Sacramento County Ccxipcrativc Agriculttiral Extension, "Water Effident Landsca^ Plants" by Pamela S. Bone,
Environmental Horticultural Notes.
Tolhier, E.W, and BJ. BarfieW, 1976, "Suspended Sediment Fdtration Capadty of Simulated
Vegetation", Trans. American Sodety of Agricultural Engineers, 19,678.
Youngner, V.B., J.H. Madison, M.H. KfrnbaU, and W.B. Davis, 1962, "CUmatic Zones for Turfgrass m Califomia",
CalUomia Agriculttire, 16 (7), 2.
Industrial Handbook 5 - 36 March, 1993
Additional Information — ekjfflters
FIGURE 4A. SIZING GUIDELINE FOR BIOFILTERS
(SQ. FT7IMPERVIOUS ACRE)
Industrial Handbook 5-37 March, 1993
Additional Information — Biofilters
Weil soapted to area
Adaptable with hi^er maintenance
Bener adapted grass availalile
I Not adaptable
BERMUDA GRASS
FIGURE 4B. STATE OF CALIFORNLV SHOWING
MOST SUITABLE TURF GRASS SPECIES
Industrial Handbook 5-38 March, 1993
i
I
Additional Infonnation — Btofiiters
COLD TOLERANCE
(winter color persistance)
High Creesing sentgrass
Ksntucky oiusgrass
.=^ed fescue
Colcniai oentgrass
Higniana def.tgrass
Perennial r/egrass
Tall fescue
V/eeping aikaligrass
Dichondra
Zoysiagrass
Common bermufiagrass
Hybrid bermudagrass
Kikuyugrass »
Seashore paspalum
Low St. Augustinegrass
HEAT TOLERANCE
Mign
i
Low
lovsiagrass
-.-r-c 3=''^UC3graS3
;J'-;T-':P ^^'Tirjoacrass
Seasncre aasoaiurr
5;. AugusiNiecrass
•^ ik'.jvugrass
"aii -^sc'je
C'eeoi'ig ^enrgrass
•".entucky 3iuegras3
-jigmanc benigrass
3er=nnial .-/egrass
Colonial sentgrass
vVeeoing aikaligrass
Red fescue
MOWING HEIGHT ADAPTATION
High cut Tall fescue
Red fescue
Kentucky bluegrass
Perennial ryegrass
Weeping aikaligrass
St. Augustinegrass
Common bermudagrass
Dichondra
Kikuyugrass
Colonial benigrass
Highland bentgrass
Zoysiagrass
Seashore paspalum
Hybrid bermudagrass
Low Cul Creeping bentgrass
DROUGHT TOLERANCE
High Hybrid bermudagrass
Zoysiagrass
Common bermudagrass
Seasfiore paspalum
S(. Augustinegrass
Kikuyugrass
Tall fescue
Red fescue
Kentucky bluegrass
Perennial ryegrass
Highland bentgrass
Creeping bentgrass
Colonial bentgrass
Weeping aikaligrass
Low Dichondra
MAINTENANCE COST
AND EFFORT
High Creeping bentgrass
Dichondra
Hybrid bermudagrass
Kentucky bluegrass
Colonial bentgrass
Seashore paspalum
Perennial ryegrass
SL Augustinegrass
Highland bentgrass
Zoysiagrass
Tall fescue
Common bermudagrass
Low Kikuyugrass
FIGURE 4C. ADDITIONAL INFORMATION ON THE
SUITABILITY OF TURF GRASS SPECIES
Industrial Handbook 5-39 March, 1993
BMP: EXTENDED DETENTIGN BASINS
H\qh-Yistcr
Line
aow
3
o <0
o e • 5
Considerations
So//s
C^rea Required^
Shpe
Water Availability
Aesthetics
C^^HjidraulhHe^^
Environmental Side
Effects
DESCRIPTION
Extended detention basuis are dry between stbrms. During a storm titie basfri fiUs. A bottom
oudet releases die storm water slowly to provide time for sediments to settie.
EXPERIENCE IN CALIFORNU
There are no known basins in CaUfomia. Hydraulic detention basins may fiinction Uke
extended detention basuis if tiic former has been sized to conttol die pre-development 2-
year event More liberal standards do not provide suffident detention time.
SELECTION CRTTERIA
Objective is to remove only particulate pollutants.
Use where lack of water prevents the use of wet ponds, wetiands or btofiiters.
Use where wet ponds or wetiands would cause unacceptable mosquito conditions.
LIMITATIONS
May tie less reliable than other treatment conttol BMPs.
InabiUty to vegetate banks and bottom may result in erosion and resuspension.
Limitation of the orifice diameter may preclude use in smaU watersheds.
Requires differential elevation between inlet and oudet
Pending tbefr volume and depth basin designs may require approval from State
Division of Safety of Dams.
DESIGN AND SIZING CONSIDERATIONS
Basin volume is sized to capttire a particular fiaction of tbe runoff.
Drawdown time of 24 to 40 houis.
ShaUow basin with large surface area performs bettex than deep basin with same
volume.
Place energy dissipators at die entrance to minimize bottom erosion and resuspension.
Vegetate side slopes and bottom to tbe maximum extent practical.
If side erosion is particularly severe, consider paving w soil stabUization.
If floatables are a problem, protect oudet witii trash rack or otiier device.
Provkle bypass w pass through capabiUties fw 100 year storm.
CONSTRUCnON/INSPECnON CONSIDERATIONS
• Make sure the oudet is instaUed as designed.
Targeted Constituents
9 Sediment
O Nutrients
Q Heavy Metals
O Toxic Materials
Q Fhatable Materials
O Oxygen Demand-
ing Substances
O 0/7 & Grease
O Bacteria & Viruses
# Ukely to Have Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
# Capital Costs
Q O&M Costs
O Maintenance
O Training
High O Low
TCS
Best^
Management
P^actices^
Industrial Handbook 5-40 March, 1993
BMP: EXTENDED DETENTION BASINS (Continue)
MAINTENANCE REQUIREMENTS
Check oudet regulariy for ctogging.
Check banks and bottom of sur&ce basui fw erosion and conect as necessary.
• Remove sediment when accumulaticm readies 6-iiiches, or if resuspension is observed.
COST CONSIDERATIONS
• GeneraUy less expensive tiian wet ponds and wetlands, but more expensive than btofiiters.
Industrial Handbook 5-41 March, 1993
Additional Information — Extended Detention Basins
C?eneral
Extended detention ponds and vaults may be particularly appxipriate to Califwnia where dry weatiier base flow cannot
be used to mainrain water levels, as is required for wet ponds and constracted wetlands. These systems are suitable fw
essentiaUy any size tributary area from an individual commercial develojHnent to a large residential area. Surface ponds
are less expensive to constmct but underground vaults may be appropriate in commercial developments. Use of
concrete retaining walls wUI reduce thc space required by a pond. The basic elements of an extended detention basin
are iUustrated in Rgure 5A. The configuration shown in Figure 5A is most appropriate for large sites.
Extended detention provides a lower removal efficiency tban wet ponds and constmcted wetlands: the faciUties are
smaUer thereby reducing tiiefr effectiveness with particulate poUutants, and tbey do not have tbe abUity to remove
dissolved contaminants. Also, extended detention faciUties may be less reliable than constracted wetlands w wet ponds
because of the lack of a pemianent water pool (See Figure 5A). But if desired, a shallow pool of 1 to 3 feet could be
included in die design but this is more of an aesthetic consideration. If irrigation water is available, a tiiick grass turf on
the bottom of thc facUity may provide some "removal of dissolved contaminants, like a vegetated biofilter. See TC4
Biofilters fw recommendations on birf grass and groundcover spedes.
Where irrigation water is not avaUable, there may be concerns about erosion and resuspension of particulate poUutants
in surface ponds. This, however, has not been a significant problem in Austin, Texas wbere sand filters are preceded by
dry settUng ponds (Hartigan, pers. comm.). However, the design must incorporate several feamres to minimize tiie
potential fw this iMDblem. Drought tolerant vegetation may worit but has not been evaluated. Nonvegetative materials
may help such as concrete w plastic grids, smaU riprap, erosion matting, w paving. A paved forebay may facUitate
maintenance thereby reducing the material available fw resuspenston.
The recommended drawdown time of 24 to 40 hours for a fiUl pond is based on very limited laboratory data. A few
extended detentiCTi ponds have been monitored and generaUy provide a removal effidency of 60 to 80% witii a
drawdown time of about 24 hours. Forty hours is recommended in order to settie out the finer clay particles in Califor-
nia sediment that ty^ncaUy adsorb toxic pollutants.
Design
Detemune the volume of the basin using die appropriate figure from Appendix D. -The procedure is as follows: (1)
seled the appropriate figure fw your area; (2) determine for thc catchment the percentage of impervious area directiy
connected to the storm drain system; (3) choose a capttire goal, and read thc requfred unit volume requfred for tiie
basin; and (4) multiply tbis unit volume times the total acreage of tbe catchment and convert to cubic feet This volume
is also referred to as water quality capture volume shown in Rgure 5 A. Total impervious acres may be used in Ueu of
directiy connected impervious acres if it is easier to detennine tbe fonner, although this wiU result in a larger faciUty.
Altiiough these variations are not equivalent tbey are reasonable given tbe uncertainty of the methodology and ex-
pected basin perfonnance.
What ^ould bc tiic capture goal? To achieve an equivalent poUutant capture percentage as a wet pond, 85 to 95
percent of the ninoff must bc captured and detained. But capttire volumes over 85 percent are not cost effective as tiie
capture cases in Appendix D show. -Tbcrcfore it is recommended that a capture volume of 85 percent be used fw
determining die detention basin size required. Because of tiic possibiUty of resuspension of materials during extteme
storms consideration should bc given to pladng tbe basin offline, dial is, it shoukl have a bypass for the extreme
events. Bypassing larger events wiU also aUow the bedload canied by die storm and is necessary fw beach replenish-
ment to move downstream.
A drawdown time of 40 hours is recommended m wder to settle out tbe finer clay particles as stated above; however,
24 hours can bc used if it can be demonstrated tiiat tiiis rate wUl remove 80% of the soUds. The analysis of ranoff usinjg
Industrial Handbook 5 - 42 March, 1993
Additional Information — Extended D^ention Basins
the hydrotogic model STORM and CaUfomia predpitation data found that increasing tiie drawdown time from 24 to 40
hours increased the size of the basin by only about 10% to 20% depentfing on thc location (sec Appendix D).
Premier hydrauUc design of die oudet is critical to achieving good performance of the detention basin. The two most
common oudet problems dial occur are: 1) titic capadty of the outlet is ttx> great resulting in partial filling of die basin
and less than designed for drawdown time and 2) the outiet ctogs because it is not adequately protected against trash and
debris. To avoid these problems, two alternative outiet types are reconimended fw use: 1) V-noteb wier, and 2) perfo-
rated riser. Thc V-notch wier wiU not clog, bul it is also difficult to maintain smaU release rates at low heads. Thc
perforated riser if propetiy designed and gravel padced gives much better control and is recoinmended over the V-noteh
wier.
Two diflerenl a^iproacbcs can bc used to controi tbe outflow. One is to use a single orifice oudet witii w without the
protection of a riser pipe. Tbe other is to use the perforated riser itself fen- discharge control. Both approaches are
presented below. *
Flow Ctmtrpl Using a Single Orifice
The oudet control orifice should bc sized using the foUowing equation (GKY, 1989).
a = 2A(H-Ho)0-5 = C7xl0-5)A(H-Ho)0-5
3600CT(2g)0^ CT
where: a = area of orifice (ft^)
A = average surface area of the pond (ft^)
c = orifice coeffident
T = drawdown time of fuU pond (hrs.)
g = gravity (32.2 ft/sec2)
H = elevation when thc pond is fiUl (ft)
HQ = final elevation when pond is empty (ft)
With a drawdown time of 40 hours tbe equatioo becomes:
a = (1.75X10"<S)A(H-Ho)0-5
C
(1)
(2)
Assuming an average release rate at ooe half thc pood depth, a cwnmoa approach in several design manuals, leads to
consideraUe errw. If the pood has a significant variation of surface area with depth, do not use Equatton (2); consiUt
GKY (1989).
Care must be taken in die selcctioa of "c": 0.60 is most often recommended and used. However, based on actual tests
GKY (1989) reoMnmcnds tiic foUowuig:
c = 0.66 for tiiin materials, that is, tbe thickness is equal to w less than orifice diameter
Cs 0.80 when the material is thicker dian die wiftoe (fiameter
DrUling the orifice uito an oudet structure that is made of concrete can result in considerable impact on die coeffident, as
docs die bcveUng of die edge. The experiments by GKY (1989) were widi sharp edged (vifices.
I
I
Industrial Handbook 5-43 March, 1993
Additional Information — Extended Detention Basins
Equation (1) defines die orUicc area wbere a single orifice outiet is used to regulate die detention basin oudlow. How-
ever, a recent survey of extended detention faciUties (GaUi, pers. comm.) found tiie drawdown time of smaU stonns that
do not fdl tiie fadUty to be ux) short to provkle effective treattnent The fadUties surveyed were designed for a draw-
down time of 24 hours. A 40 hour drawdown may provide suffident time fw tiic smaUer sttxms. But it may be pradent
to take additional steps to be certaui that tiie anaU sttxms, which represent die majority of poUution, are eff^ectively
tteated. One approach wodd bc to check die design analysis to determuie if die fadUty takes at least 24 hours to drafri
when half fuU. If not eitiier modUy tiic design to achieve tius objective, w insttdl a two orifice outiet The lower outiet
is sized to drain a half-fiiU facUity fri 24 hours. The second orifice is placed at tiie nud-watcr elevation and is sized in
combination widi tiiic lower orifice to drafri die entire facUity m 40 hours. Anotiier approach is to instaU tiie outiet about
one foot above tiic bottom of tiic pond (essentiaUy enlargfrig tiie micropool area). This lower area wiU dry up between
stonns and wiU capttire much of thc volume of smaU stonns and improving poUutant removal.
Three altemative outiet sttucmres are suggested (Figure 5B). Thc concrete block sttucttue is appropriate for large ponds.
Thc riser pipe is suggested for small to large ponds. Placing die oudet control ui die berm w in a manhole located
downstream of tbe CaciUty is most suitable fw smaU ponds.
Recommendations reganUng die design of a riser pipe are shown fri Table 5 A fw Austin (1988). Table 5 A provides
guklancc on the location of holes. To prevent dogging of tius orifice and die bottom orifices of tiie riser pipe, wrap tiic
bottom tiuee rows of orifices witii geotextile fabric and a cone of one to tiiree inch rock. The holes in tiie riser pipe
shoukl not bc modified to achieve a 40 hour drawdown time. Ratiier, the control orifice should he placed downstteam.
Fw smaU faciUties, place tiie control orifice in a manhole between tiic pond and tiie filter as shown in Figure 5B. Use a
"T-pipe" (Rgure 5B) to submerge tiie orifice.
TABLE 5A PERFORATED OUTLET RISER PIPE ORIFICES (Austin, 1988)
VER-nCAL
SPACING
RISER PIPE BETWEEN ROWS NUMBEROF PERFORATION
DL\METER (center to center) PERFORMATIONS DL\METER
6 in. 2.5 in. 9 per row lin.
8 in. 2.5 m. 12 lin.
10 in. 2Jin. 16 lin.
Ctogging of die bottom holes has been observed in riser pipes fri tiic mid-Adantic states (MWCOG, 1992) suggesting tiiat
die diameter of die riser holes sbouW not bc less tfian 3/4 to I" (MWCOG, 1992) altiiough a minfrnum diameter of 2" is
now being considered (GaUi, pers coaun.). However, most of tiic facUities surveyed had risers yitbout die gravel cone
and die oudet holes were modified to provide drawdown conttol. Modifying tbe holes in die riser to conttol tiie outiet
rate reduces die diameter of die holes and nicreases die risk of clogging. However, gravel packing tiie riser pipe as shown
in Rgure 5B2 aad 5C.1 wiU minimize dus risk. Submerging die conttol orifice as showo in Rgure 5B3 wUl aUow die
use of a smaUer orifice diameter. Ooc orifice witii a diameter of 1/2 uidi, w 1 mch to be conservative, aUows tiie use of
extended detentioa for very smaU catefaments. Detention facUities in westem Washington use tiiis concept and have not
experienced clogging problems.
Row Conttnl Using ttie Perforated Riser
Fbr outlet conttol using thc perforated riser as the outflow controL it is recommended that the procedure developed by die
Denver Urban Drafriage and Rood Control Disttid be used (UDFCD, 1992) as Ulusttated ui Figures 5C and 5D. Figure
5D uses a valve fw C^ of 0.65. This design mcorporates flow control for tbe smaU sttmns m die perforated riser but also,
provides an overflow oudet fw large stonns. If properiy designed, die CaciUty can bc used fw botii water Quality and
Industrial Handbook 5 - 44 March, 1993
Additional Information — Extended D^ention Basins
drainage contrd by: 1) sizing the perforated riser as indicated for water quaUty control; 2) sizing tbe outiet pipe to
contrd peak outftow rate ftom tbe 2 year storm; and 3) using a spiUway m thc pond berm to control the disdiarge from
larger stonns up to tbe 100 year storm.
Otlicr Design Considgratinufi
Do not locate on fiU sites w on or near steep slopes if is expected that much of tbe water wUl exit tiirough tiie bottom,
or modify thc bottwn to prevent excessive infUtration.
Energy (Ussqiation at thc iiUet to minimize erosion
Vegetate thc slopes and bottom fw the same reason
Freeboard of 1 Coot
Side stopes of at least 2:1 unless vertical retaining walls are used
Incorpcvate bypass or overflow fw large events
Provide dedicated access to the basin bottoip (ounimum 4:1) fw maintenance vehicles
With a riser stmcture, include an anti-vortex device and a debris barrier.
Maintenance
Conduct inspections scmiannuaUy and after each significant storm. Remove floatables and correct erosion (Mroblcms in
tbe pond slopes and bottom. Pay particular attention to tiic outiet control orifice(s) for signs of dogging. If tbe orifice is
located in a Type 2 cateh basin, remove sediments if they are within 18 in. of the wifice plate. Often extended detentton
basin serve multiple used, e.g. basebaU fieU, resulting in higher mamtenance costs.
REFERENCES
Austin (City oO. 1988, "Environmental Criteria Manual".
(jaUi, J., pers. comm., MetropoUtan Washington CouncU of Governments.
GKY, 1989, "Oudet HydrauUcs of Extended Detention FaciUties", for the Northem Vfrginia Planiung District Commis-
sioa
Hartigan, P., pers. comm., Washington Departtnent of Ecology (formerly witii tiie City of Austin).
MetropoUem Washuigton CouncU of Govemments (MWCOG), March, 1992, "A Current Assessment of Urban Best
Management Practices: Techniques fw Reducing Nonpoint Souice PoUutioo m the Coastal Zone".
MettopoUtan Washingttxi Coundl of Govemments (MWCOG), 1983, "Nationwide Urban Runoff Program PoUution
Removal Capatnhty of Urban Best Management Practices in flic Washington MetropoUtan Area", available firom NTIS.
PB84-245497.
Northem Vfrgfriia Ranning Distria Commission (NVPDQ, 1987, "BMP Handbook for die Occoquan Watershed".
RandaU, C.W., et al., 1982, "Urtan Runoff PoUutant Removal by Sedunentation", in Procecdfrigs of die Conference on
SUMmwater Detentioa FaciUties, HcnnUcer, NH, ASCE, pp 205-209.
Urban Drainage & Ftood Conttol District, Deaver Colorado, "Urban Storm Drainage Criteria Manual - Volume 3 - Best
Management Practtoes - Stormwater QuaUty", September, 1992.
Whipple, W. and J. Hunter, 1981, "SettieabiUty of Utban Runoff PoUution", J. Water PoUution Coattol Federatioa, 53
(12): 1726-1731.
Industrial Handbook 5-45 March, 1993
5*
9
r
side Slopes No Sleeper lhan 4:1
tn
EinbankmenI SkJe Slopa
No Steeper lhan 3:1
Forebay
Inflow —•
FloW^
Dispersing
Inlel
Solid Driving Suriace
Frequent
Runoli Pool
10% 10 25V. ol WQCV
Storage)
NOT TO SCALE
Waler Qualily Capture Emergency Spillway Flood
Voltime (WQCV) level ^^^^^ ^,^3,
(including 20% addilionaj/ (e.g. lOO-yrJ
volpme fpr sediment Spillway Ciesi
liiveri
Low Flow
Channel
1.5'lo 3* ;>
SECTION
NOT TO SCALE
Oullel Works
[Sea Figure 5B.3 or 50)
(Used By Permission, UDFCD, 1992)
FIGURE 5A. PLAN AND SECTION OF AN EXTENDED
DETENTION BASIN
>
Q.
ZJ
SL K o
3
& o
5
S
a> R K a
a
o
Additional Information — Extended D^ention Basins
.HGURE SB. 1 CONCHETE STRUCTURE
-J- -
Side View
I'•—Emergency Spillway '
I (If Applicable)
j-Rood Control Outlets
Extended
Detention Outlet
10 or 25 Year Outiet
• 2 Year Outlet
Front View
FIGURE 53.2 RISER PIPE
'nraacad Cao
(See Table SA)
|: :
/
/ Gravel
/ Envelope te / (recommended)
^<aai^ . >^ 'vv>
»'•".-*'",•• fW
''J'*^'^ ~ 5<> 1 Viii;
/
Design into Impoundment as
Flood Control Spillway
.Vi-.-.-
K-.."-.-..« Control
Orifice Plate
RGURE 5B.3 CONTROL MANHOLE
Control Structure ^ Ftood Control Outlet
Emergency Overflow r
Pond Design W.s.-7-
rW.S. \
Source: Douglas County, Colorado
Berni Embankment^
Controi Oriflce Plate
FIGURE 5B. OUTLET CONFIGURATIONS USING
SINGLE ORIFICE FOR FLOW CONTROL
Industrial Ebndbook 5-47 March, 1993
Additional Information — Extended Detention Basins
Thrsadad Caa
Water Quafity
Riser Pipe (See Detail)'
Notas: 1. Tha ouSat pipa shaH ba sizsd to control
everflow into na concraia risar.
2. Altemata dasi9ns induda a Hydrobraka outlet (or on fica
designs) as tong as 9ie hydraulic perfonnanca matches itis
configuration.
Concrete
Access Pit
(Min. 3 ft)
Ramovaoie & Locxaoia
Cvarrlow Grata for
Lar^ar Storms
.*/•.'.'•
••.vi.'
Outlet Pioa-
OUTLET WORKS
NOTTOSCALc
Size Base to Pravant
Hydrostatic Uplift
Notes: 1. Mirvmum number of hoias > 8
2. hfinimum hola diameter - 1/S* dia.
1-1/2* diameter Air
Vent In Threaded Cap
Water Quality
Outlet Holes
Ductile Iron or
Steal Pipe
WATER QUALITY
RISER PIPE
NOTTO SCAL5~
(Used By Perniission. UDFCD. 1992)
Maximum Numbar ol ?arforatad Columns
Risar
Oiamatar
fn.)
Hole Diamatar. in. Risar
Oiamatar
fn.) 1/4-1/r 3/4*
4 S 3 - 1 -
s 12 12 9 -
8 IS 16 12 8
10 20 20 14 10
12 24 2* 18 12
Hole Diameter
On.)
Ana ol Hole
(in.2)
1/8
1/4
3/8
1/2
5/8
3/4
7/8
1
OJ313
0JD*9
0.110
0.196
0J07
0.442
0.601
O.Tas
FIGURE 5C. OUTLET CONFIGURATION USING
PERFORATED RISER FOR FLOW
CONTROL
Industrial Handbook 5-48 March, 1993
Additional Information — Extended D^enticn Basins
0.01 0.02 0.04 0.06 0.10
Source: Douglas County (Colorado) Storm Drainage
and Technical Criteria, 1986.
1 1 » i L !_
0.20 0.4O 0.60 1.0 2.0 4.0 6.0
R«qutrad Araa p«r Row (iru^)
(Used By Pennissfon. UDFCD, 1992)
FIGURE 5D. WATER QUALITY OUTLET SIZING:
EXTENDED DETENTION BASIN WTTH
A 40-HOUR DRAIN TIME OF THE
CAPTURE VOLUME
Industrial Handbook 5-49 March, 1993
BMP: MEDIA FILTRATION
FLOW PBETREATMENT
Consideratk>ns
Soils
Area Required
Shpe
Water Availability
Aestheths
(^H^rauth H^^
Environmental SkJe
Effects
DESCRIPTION '
Coosists of a settiing basin foUowed by a fUter. The most common filter media is sand;
some use peat/sand mixture.
EXPERIENCE IN CALIFORNIA
A tenant at die Pwt of Long Beach recentiy instaUed a sand fUter. Thc City of Los
Angeles wiU soon instaU several experimental filters.
SELECTION CRITERIA
• Objective is to remove only sediment (particulate poUutants).
• Use where unavailabiUty of water prevents tiie use of wet ponds, wetiands, or
biofUters.
• Can bc placed underground.
• SuitaWe fw mdivklual devdofanents and smaU tributary areas up to about 100 acres.
• May require less space tban other treatment cootrol BMPs.
LIMITATIONS
• FUtcr may require more Crequenl maintenance tiian most of die other BMPs.
• Head loss.
Dissolved poUutants are not captured by sand.
• Severe clogging potential if exposed soU surfaces exist upstream.
DESIGN AND SIZING CONSIDERATIONS
• Settling basin smaUer than wet or extended detentioa basin.
• Spread flow across filter.
• Place fUter offUne to protect firom extreme events.
• Minimize erosion in settling basin.
CONSTRUCnON/INSPECnON CONSIDERATIONS
• Be certain filter sand is dean and die outiet device firom the basin to tiic filter is level
MAINTENANCE REQUIREMENTS
• Clean filter surface about twice annuaUy; w more often if watershed is excessively
erosive
COST CONSIDERATIONS
• Fdtratioo system may use less space tiian other systems.
• Smaller media improves perfonnance but increases maintenance costs.
Targeted Constituents
# Sediment
O Nutrients
Q Heavy Metals
O Toxh Materials
# Fhatable Materials
9 Oxygen Demand-
ing Substances
Q Oil & Grease
Q Bacteria & Viruses
• Ukely to Have
Significant Impact
O Prot>able Low or
Unknovm Impact
Implementation
Requirements
# Capital Costs
Q O&M Costs
O Maintenance
O Training
High O Low
TC6
Best^
Management
PracticesN
Industrial Handbook 5-50 March, 1993
Additional Information — Media nitration
Sand filters may be particularly suitable for industrial sites because the settling basin can be located underground. A
sand filter consists of two units: settling basin and thc fUter. Pretreatment is essential to avoid rapid clogging of the
filter. Peat/sand mixture has been use± peat having thc abUity to remove dissolved contaminants. However, there have
been clogging probkms (Tomasak, et al., 1987) bul tiiis may bc due to using die wrong type of peat ((jaUi, 1990).
Linuted researdi indicates that compost made firom leaves is very effective at removing dissolved phosphoms and
metals, and oU and grease (Stewart, 1989). A new concept is placement of a fUter device in a catch basin insert
(McPherson, 1992) which may be very weU suited for industrial sites.
Field research in the City of Austin, Texas (Austin, 1990) intficates tiie sand filter has a removal effidency of suspended
soUds tiiat is similar to wet ponds and extended detention: 70 to 90%. The observed removal of metals was 20 to 80%,
dq>ending on die metal, 20 to 30% fw nitrogen, and 50 to 60% for pbospbonis. These rates are also similar to wet
ponds, which is not expected as a fUter does not remove dissolved contaminants. Sand with a diameter smaUer than used
in Austin would likely improve performance bdl has not been tried.
Thc sand fUter should be an ideal system for tbe Central VaUey and Southem (TaUfonua It does not rely on vegetatioa,
and has proven itself in the City of Austin. Tbe sand filter is suitable fw tributary areas of a less tiian an acre to about 50
acres.
Make certain that any soU erosion problems in the site have been conected (Chapter 4). Experience in Austin indicates
that exposed soUs during construction "upstream" firom thc fUter can result in pentration of fines into the filter media,
resulting in a need to replace die entire filter bed. Thc system should have a bypass for extreme events.
Altemative configurations
The most experience to date is with surface faciUties shown conceptuaUy in Rgure 6A. It can be used on catchments up
to perhaps 50 acres. Its origin is Austin, Texas where there are now several hundred faciUties. The "Austin" filter uses
an extended detention basin with a drawdown time of 24 hours. Two other systems are most suitable for smaU
catchments ofa few acres. An undergnxmd "linear" filter (Rgure 6B) is used in Delaware (Shaver, 1991). The filter
accepts sheet flow firom adjacent pavement It. therefore, may be ideal fw industrial appUcations. Another underground
design (Rgoie 6C) developed in Washingtoa D.C. (Tmong, 1989) is also ideal for developments. It accepts concen-
trated flow. Both of these underground systems use a wet vault (w water quaUty inlet, see TCJ) as tbe pretreatment
device. The fourth concept is (Rgure 6D) is an insert placed in existing cateh basins. It should otUy bc used where
maintenance staif are available to check tbe fUter firequentiy and wbere local flooding will not occur if the filter clogs.
Determining tiie volume of tfie prett^eannent unit
To size die pretreatment basin refer to die sizing metiiods for extended detention (TC5). Witii tiie sand fdter tbe pre-
treatment basin need not bc as effident as a fiiU size system. Thc pretreatment system, however, should bc large enough
to provide a removal efllcieney that avokls rapid dogging of thc fUter. As yet, there is no dear answer on this question.
For now it is suggested that die volume of a wet vadt be such as to achieve a removal effidency of 50 to 60%.
Tbe volume of an pretreatment unit can bc decreased by redudng the drawdown time, which results in a lower but
acceptable removal effidency. The fuiUty volume can be detennined firom TC5 Extended Detention using a drawdown
timeof 24 hours.
Industrial Handbook 5-51 March, 1993
Additional Information — Media nitration
Detennining the surface area of die fUter
The foUowing equation is derived firom Austin (1988) for a maximum (fuU pretreattnent basin) fUtration time of 24
liours:
FUtta-area(ft2) = 3630SuAH/K(D+H) (D
where: Su = unit storage (inches-acre) firom Appendix D
A = area in acres draining to faciUty
H = deptiii (ft) of die sand fdtta-
D = average water deptiii (ft) over the fUter taken to be one-half thc difference between die top of the fiilter
and die maximum water surface elevation
K = fUtcr coeffident recommended as 3 J (Austin)
i
Equation (1) is appropriate fw thc filter media size reconunended by the City of Austin, diameter of 0.02 to 0.04 inches.
The fUtcr area must bc increased if a smaller media is used (see Austin, Texas (1988)).
Configuring a surface sand filter (City of Austin concept)
Additional design criteria for die settling basin (Austin, 1988):
Fw die oudet use a perforated riser pipe, as described in TC5, Extended Detention
Size the outlel wifice for a 24 hour drawdown
Energy dissipatw at the inlet to the settling basin
Trash rack at outiets to the filter
Vegetate slopes to tbe extent possible (see Vegetated Biofilters)
Access ramp (4:1 or less) fw mauitenance vehicles
One foot of firecboard
Lengtb to width ratio of at least 3:1 and preferably 5:1
Sediment trap at inlet to reduce resuspension. One concept is shown in Rgure ffi.
Additional design criteria for die filter
Use a flow spreader (Rgure 6A).
Use eitibicr of two altemative sand bed designs (Rgure 6F).
Use dean sand 0.02 to 0.04 inch (Uameter.
Some have placed geofabric on sand surface to faciUtate maintenance.
Underdrains (Rgure 6A).
- Sdiedule 40 PVC.
4 inch diameter.
3/8 mch perforations placed around die pipe, with 6 mch space between each perforation cluster,
maximum 10 foot spadng between laterals.
- minimum grade of 1/8" per foot
Configuring the linear filter
Take die volume for the pretreatment unit and die fUter area identified above and configure mto a stmcture similar to tiiat
shown in Rgure 6B. The structural desiga in Rgure 6B assumes traffic loads over the filter. The structure can bc less
robust if it is located along die edge of die pavement away fixim traffic Odier reconunendations (Shaver, 1991):
Industrial Handbook 5-52 March, 1993
Additional Information — Media Ritration
• Depdiof sand 18"
• Diameter of the oudet pipe should be 6" or less; use miUtiple outiets if necessary
The fUter must be positioned relative to the pavement in a manner that evenly distributes the flow as it enters the
sedimentation chamber. Pavement design and constmction is therefore critical.
Configuring tiie wet vault filtftr
Similarly tiie volume of the wel vault and fUter area are configured into a rectangular unit similar to that shown in Figure
6C. Otber coasiderations for the wet vadt include:
• A length to width ratio of at least 3:1 to minimize short-circuiting
• Baffles to reduce entrance velodties and tq retain floatables
• Access ports to faciUtate maintenance
• Depth of the wet pool of at lcast3 feet but not more tiian 10 feet
Catch basin insert
The catdi basin mscrt fUtcr may bc ideal fw industrial sites as il can be placed in existing catch basins, and tiierefore
may avoid die need fw an "end-of-pipe" CadUty. Thc system is Ulusttated m Figure 6D. It consists of a series of trays.
The tc^ tray is a sediment crap. Fdter material is placed in tbe lower trays. Of several materials examined, thc most
suitable appears to be household fiberglass insulatkin. Limited tests indicate over 90% removal of metals and oU
(McPherson, 1992). As tiic insert requues frequent attention it sbodd only bc used where a maintenance person is
locanal on-site. Thc msert has a bypass along one skle shoukl tiie fUter material clog and is hydiaulkaUy designed so as
to not compromise die primary purpose of a cattA basin, to get stcvm water inio ttic drain system. The concept shown in
Rgure 6D is prof«ictary (Enviro-drain, 1992).
Maintmiwire!
Inspect semiannually, and after m^w stcrais. Sediment should bc removed fiom thc settling basin when 4 inches
accumulates and from tbe fUter when 1/2 mch accumulates, or when dicrc is stiU water in tiie basin w over the filter 40
hours after tiie stotm. Remove floatables. Experience in Austin indicates die fdter surface must be cleaned about twice
each year by raking off die dried sediment FaUure to clean tiic fUter regularly may resuk in tiie need to replace die
entire media because of penettation of fmes mto tite fdter. Il is more cost effective over tiic long term to clean die fdter
regularly as recwnmended. If there are open space areas in die ttibutary that are erosive or if constroctkMi is occurring,
more firequent deaning wiU be necessary. It may bc necessary lo replace tiic fUter media after constmction activity has
ceased and tbe soils are stabUized.
Consdt Austin (1988), Tmong (1989), and Shaver (1991) fw additional design and maintenance criteria.
REFERENCES
Austin (City oO. 1990, "Removal EffKiendes of Stonnwater Conttol Sttucmres".
Austin (City <rf), 1988, "Environmental Criteria Manual".
Enviro-dram Inc, 1992, Kirkland, Wasbingttm.
GaUi, J., 1990, "Peat-Sand Rlters: A Proposed Stormwater Management Practice for Urbanized Areas", MettopoUtan
Washingtoa CouodI of Governments.
McPherson, J., 1992, "Water (QuaUty BMPs: Catt± Basin InfUttation", iwesented to tiic APWA
Stonnwater Managers Comminee, Tacoma, Washington.
Industrial Handbook 5 - S"? .
^ March, 1993
Additional Information — Media Filtration
MetropoUtan Wasbingttm Coundl of Govemments (MWCOG), March, 1992, "A Currenl Assessment of Urban Best
Management Practices: Techniques for Redudng Nonpoint Source PoUutioa in die Coastal Zone".
Shaver, E., 1991, "Sand Rlter Design fw Water CJuaUty Treattnenf, Delaware Department of Nattiral Resources.
Stewart W., 1989, "Evaluation and FuU-Scale Testing of a Cwnpost BfofUter fot Stormwater Runoff Treattnent",
presented at die Annual Conference of the Pacific Nortiiwest PoUution Control Association.
Tomasak, MJD., G.E. Johnson, and PJ. MuUoy, 1987, "Operational Problems wifli a SoU FUttation System fw Treating
Stormwater^, Minnesota PoUutioa Coatrol Agency.
Tmong, H. V., 1989, "The Sand Rlter Qaahty Sttucttire", Disttict of Columbia Govemment
Industrial Handbook 5-54 March, 1993
5^
a.
PLAN ViEW
in
tn
Ul
n er
VO Ul
Fillralion Basin
Energy Dissipalors
Fillered Oulllow
Slone
Rip Rap
ELEVATION Underdrain Piping Sysiem
>
Q. CL
S
O
3
5"
o
3
o'
3
3E
s.
o
3
Source: City of Austin
FIGURE 6A. CITY OF AUSTIN SAND FILTER
Additional Information —- Media Filtration
•T.OW r
GRATZDCOVEIt SOLm COVER
1 DRAiN
OUT? ALL
FLOW PAVTNG
*•
-I •
1
% • X 0 1 %
• 0
• %
SA>T) OLTFALL
SECnONA-A
CRATE (FABRIC WTIA??£D
OVER ESmZ CRATE OPE>T>«J)
Source: Shaver (199D
FIGURE 6B. LINEAL SAND FILTER
ENTRANCE
GROUND
LAOC£.=) . ENTRANCE
= B,T
ENTRANCE
ORA:.S
•WASHED SANa--V:;>;.'|..j
f|N.CLOW ^^SHEO ry/ C CLEAN OlK PIPE
Source: Distnct of Columbia
FIGURE 6C. VAULT SAND FILTER
Industrial Handbook 5-56 March, 1993
Additional Information — Media Filtration
Catch Basin Grate
Sediment Trap
Filter Trays
Bypass ' Oitflow
Source: McPherson (1992)
FIGURE 6D. CATCH BASIN FILTER
Industrial Handbook 5-57 March, 1993
Additional Information — Media nitration
Sediment Trap Drain Pips
Drop Inlet
Bottom of
Sedimentation
Basin
10
" Outlet
Structure
Section A - A
(Gravel Not Shown)
Sediment Trap
To Outlet Structure
2" Gravel Layer ^ Perforated PVC Pipe B. SEDIMENT TRAP
Over Pipe Wrapped in Geotextile Fabric
Source: City of Austin
FIGURE 6E. EXAMPLE RISER PIPE AND SEDIMENT TRAP DETAILS
Industrial Handbook 5-58 March, 1993
Additional Information — Media Filtration
18" Min.
Sand Bed
V
r
Gravel
Layer
Geotextile Fabric Perforated PVC Pipes
A SAND BED PRORLE (WiTH GRAVEL LAYER)
4" Perforated PVC Pipe
Covered with Geotextile Fabric
18" Min.
Sand Bed
1"To2"
Gravel Layer
Max. Slope 4:1 Geotextile
Fabric
-Max. 10'-0" O.C.
B. SAND BED PRORLE CTRENCH DESIGN)
Adapted from City of Austin (1989)
FIGURE 6F. SAND BED FILTRATION CONFIGURATIONS
Industrial Handbook 5-59 March, 1993
BMP: OIUWATER SEPARATORS AND WATER QUALITY INLETS
FLOW
Consideratkins
So/7s
Stope
IVater Availability
Aestheths
Hydraulh Head
Environmental Side
Effects
DESCRIPTION ,
Oil/water separators arc designed to remove one specific group of contaminants: pettoleum
compounds and grease. However, separators wiU also remove floatable debris and settie-
able soUds. Two general types of oil/water separators are used: conventional gravity
separatw and tbe coalescing plate interceptw (CPI).
EXPERIENCE IN CALIFORNIA
Oil/water separators are in use throughout California at industrial sites. OU/water separa-
tors are used at aU bulk petroleum storage and refinery facUities. A few jurisdictions
require new commerdal developments to instaU separators under certain sittiations tiiat arc
environmentaUy sensitive
SELECTION CRIIERL^
AppUcable to situations wbere the concentration of oU and grease related compounds wiU
be abnormaUy high and source control cannot provide effective control. Thc general types
of businesses wbere tiiis situatioa is likely are ttuck, car, and equipmeni maintenance and
washing businesses, as weU as a business that performs maintenance on its own equipment
and vehicles. Public faciUties wbere separators may bc required include marine ports,
airfields, fleet vefaicie maintenance and washing, fadUties, and mass transit park-and-ride
lots. Conventional separators arc capable of removing oU droplets witii diameters equal to
w greater tiian 150 mkaons. A CPI separatw sbodd be used if smaUer droplets must be
removed.
LIMITATIONS
Littie data on oU characteristics in storm water leads to considerable uncertainty about
performance.
• Air quaUty permit (conctitional authorization) permit-by-rale from DTSC may bc
required.
DESIGN AND SIZING CONSIDERATIONS
• Sizing related to anticipated influent oU concentration, water temperature and veiodty,
and die effluent goal. To maintain reasonable separatw size, it should bc designed to
bypass flows in excess of first flush.
CONSTRUCTION/INSPECTION CONSIDERATIONS
• None identified.
MAINTENANCE REQUIREMENTS
• Clean firequentiy of accumulated oil, grease, and floating debris.
COST CONSIDERATIONS
• Coalescing ^te material is costiy but requires less space tiian thc conventional
setiarator.
Targeted Constituents
O Sediment
O Nutrients
O Heavy Metals
O Toxh Materials
% Fhatable Materials
d Oxygen Demand-
ing Substances
# Oil & Grease
O Bacteria & Viruses
• Ukely to Have Significant Impact
O Prol>able Low or Unknovm Impact
Implementation
Requirements
9 Capital Costs
Q O&M Costs
O MaintenarKe
O Training
• High O Low
TC7
ManagemenK
Practices>—*
Industrial Handbook 5-60 March, 1993
Additional Information — OilWater separators and Water Ouality Inlets
General Informarinn
OU/water separatt>rs wUI bc needed for a few types of industtial sites where activities result m abnonnal amounts of
pettoleum products lost to exposed pavement dtiier by acddental smaU spUls w nonnal dripping from tiic vehicle
undaomage nus wUl most Ukely bc related to vehide and mobUe equipment maintenance activities. Separators mav
^ bc advisable where an area is heavUy used by mobUe equipment sudi as loadmg wharfs at marine por^ Limited dL
uxUcates od/water separators can reduce die oU/grease conccattation below 10 mg/1 CLcttenmaier, et al. 1985).
Wet ponds, coosttucted wetiands, and biofilters wUI remove pcttolemn products but tiieir leliabUity is micenain where
high cwicenttatiwis of pettoleum products may occur firequentiy. Aiso, BMPs tiiat rely on vegetation may be damaged w
become unsightiy high concenttations of oU and grease occur frequentiy.
Tbe^g of sectors is based upon die rise rate veiodty of oU drtjplet and rate of mnoff However, witii ti,e exception
of Stom water firom od refmcnes tiiere arc no daia describmg tiic characteristics of pettoleum products in urt>an storm
water ibatare relevant to design: ddier oU density and droplet size to calculate rise rate w direa measurement of rise
rates. Fur^ ,t ,s known (Sdvemian, 1982) fliat a significant peroentage of die pcttolemn products are attadied to tiic
hlSSn °" ^ "'"^^''^ "^"^^ perfonnance of oil/water
Tlic bask: configurations of tiic two types of separators are Ulusttated m Rgure 7A. Witii small instaUations, a conven-
StStr^ general appearance ofa septic tank, but is much longer in relatiwiship to its widtii. Larger
feobttcs have the ^.pcarance of a munidpal wastewater primary scdimcntatiwi tank. TTH: CPI sepJator contains dSLlT
spaced plates whidi enhances die removal effidency. In effect to obtain tiie same effluent quaUt^ a CPI s^^^r
S^SS^?^^'';.^^' ^ •»'^^«>"vcntional separator. TUc angle of tiie plates to tiie horizontal ran^fi^m OO
^o^in^ to 60O. altiiough 450 to 60° rs tiic most commwi. THe perpendicular distance between tiie plates typk:aUr
i^^I^ht^'"'" is tite water quaUty inlet Ulusttated in Rgure 7B. It is essentiaUy a cwiventional gravity separatw but
^tbouuhe appnj«iate gcwnctticcoafiguratioa (see Design discussfon below). Anodier name fw tins systeT^ a wet
s^aZT^^^Te ^^l'^.'^ ^ ^ Effective (Shepp, et al. 1992) because tiie ^co^^d^
sue (200 to 400 ft /acre of ttibutary) is too small To bc effective, a water quaUty inlet must have die surface area and
jtolt^ dm is sundar to that of cwiventional separaton.. TUcy may exhibit'odorVoblems during I sZ^^^^ of
w.^ ? de^dauon of accmndated wganic matter and tiic lade of rcUration of tiic let poTSiS
Wa^gton D.C. have been observed to have odw but it has been noticeable only when tiic system Opened fw
E>esign of Cnnventinnal .^Snrarflfnri
"'"^ ^ °" '^P'^^ "^"8 die following equation
Vp = 1.79(dp-dc)d2xl0-8/n (1)
where:
n
dc
d
= rise rate (ft/second)
=s absolute viscosity of die water (poises)
= density of die wl (gm/cc)
= density of die water (gm/cc)
= diameter erf" die droplet to be removed (nucrons)
March, 1993
Additional Information OilWater separators and Water Quality Inlets
A water temperature must be assumed to select tiie appropriate values for water density and viscosity from Table 7 A. The
engineer should use the expected temperature of tiie storm water during the December-January period. There are no data
on die density of pettoleum products in urban storm water but it can be expected to Ue between 0.85 and 0.95. To selea
the droplet diameter tbe engineer must identiify an effidency goal based on an understanding of the disttibution of droplet
sizes in stcwm water. However, tiiere is no information on tiic size distributron of oU droplets m urban storm water.
Rgure 7C is a size and volume distribution for storm water firom a petroleum products storage faciUty (Branion, undated).
The engineer must also seled a design influent conccnttation, which carries considerable uncertainty because it wUl vary
widely within and between storms.
To Ulusttate Equation 1: if the effluent goal is 10 mg/1 and the design influent conccnttation is 50 mg/1, a removal
effidency of 80% is required. From Rgure 7C: tiiis effidency can be achieved by removing aU droplets witii diameters
90 nucrons w larger. Using a water temperature of lOOC gives a water density of 0.998. Using an oU density of 0.898,
the rise rate fw a 90 micron droplet is 0.0011 feet per second.
It is generaUy beUeved that conventional separators are not effective at removing droplets smaller than of 150 microns
(APL 1990). TheorcticaUy, a conventional separatw can be sized to remove a smaUer droplet but tiie facUity may be so
large as to make thc CPI separator more cost-effective.
Sizing conventional separatw (modified from API, 1990).
D= (Q/2V)" (2)
where: D = depth, which sbodd bc between 3 and 8 feet
Q = design flow rate (cfs)
V = aUowable horizontal veiodty which is equal to 15 times the desiga oU rise rate but uot greater than
0.05 feet per second
If the depth exceeds 8 feet design parallel units dividing tiic design flow rate by the numbcr of units needed to reach the
n^Timiim reconunended dcpdi of 8 feet Equation (2) is simplified firom equations in API (1990) based on a recom-
mended widtii to deptii ratio of 2. Thc constant in Equation (2) can be changed accordmgly if a different ratio is as-
sumed. Sc»ne engineers may wish to increase the faciUty size to account fw flow turbulence. See API (1990) fw tiic
design procedure.
Uien:
Calculate kngtii, L = VD/Vp
Compute widdi, W = Q/(VD). This shoukl be 2 to 3 times tiie depdi, but not to exceed 20 feet
Baffle height to dqpth ratio of 0.85 fw top baffles and 0.15 fw bottom baffles
Locate tbe distribution baffle at O.IOL from tbe entrance
Add one foot for firecboard
Install a bypass fw flows in excess of flic design flow
Determining the design flow, Q, requires identification of tbe design sttMm. The separattx is expected to operate effec-
tivdy at aU ftow rates equal to w less than die peak mnoff rate of the design stonn. The design storm need not be an
extreme event as is typicaUy used in tbe sizing of flood control fadUties. If sized to handle a storm firequency between
the 3-nioath to I-year event tiie faciUty wiU effectively treat tiie vast majority of storm water tiiat occurs over time. AU
events equal to w less tiian tiic 6-inootii event represents about 90% of tiic predpitation over time; designing for a 2-year
Industrial Handbook 5-62 March, 1993
Additional information — Oil/Water Sep^ors and Water Quality Inlets
event only increases the amount of runoff treated by about 5% (increase from 90% to 95 % of rainfaU treated). For the
design storm selected, calculate tbe peak nmoff rate using thc rational method.
Application of tiie Conventional OU/Water .Separator
Assume tiiat a conventional oil/water separatw is to be used to treat runoff from a 1/2 acre parking lot Assume further it
is to bc sized to treat runoff fiom a rainfaU rate of 0.50 inches/hr (which translates to a runoff rate of 0.50 cfs/acre when
tiie area is IOO percent impervious.
Using the example above, tiic computed Vp is 0.0011 ft/sec. Using Equation 2, V =15 x 0.0011= 0.0165 ft/sec wbich is
less than 0.05 ft/sec; thus,
D = (Q/2V)0.05 = (1/2 X 0.05/(2 x 0.0165)) x 0.05
D = 3.8ft. '
L = VD/Vp = 0.0165 X 3.8/0.0011
L = 57ft
W = Q/(VD) = 0.25/(0.0165 X 3.8)
W = 4.0 ft since W is less tiian 2x D, uicrease widtii to W = 3.8 x 2 = 7.6 ft
Thus, a conventiooal oil/water separator sized to capture mnoff firom a 0.5 in/hr rainfaU on a 1/2 acre parking lot would
bc:
D = 3.8 ft
W = 7.6ft
L = 57 ft
•SiTinp CPT VT>aratnr
Manufacturers can provide padcaged separator units fw flows up to several cubic feet per second. For larger flows, tbe
engineer must size the plate pack aod desiga die vault Givco the greal variabiUty of separator technology among
manufacturers with reflect to plate size, spadng, and incUnation, it is recommended that the design engineer consult
vendors fw a plate package tiiat wUl meet the engineer's criteria. Manufacttirer's typicaUy identify thc capadty of
various standard units. However, tbe engineer's design criteiia must be comparable to tbat used by the manufaaurcr in
rating its uaits.
The engineer can size die faciUty using die foUowing procedure. First identify tiie expected plate angle, H (as degrees),
and calculate the total plate area required, A(ft2).
A = Q/VpCosincH (3)
CPI separatws are not 100% hydrauUcaUy effideot; ranging firom 0.35 to 0.95 depending on die plate design (Aquatrend,
undated). If die engineer wishes to inccnporate dus factor, divide die result firom Equation 3 by tiie seleaed efficiency.
• Seled spadng, S, between die plates, usuaUy 0.75 to 1.5 inch.
• Identiify reasonaUe plate width, W, and kngtb, L.
• Number of plates, N =A/WL.
• Calculate plate volume, Pv(ft^).
Industrial Handbook 5-63 March, 1993
Additional Information — Oil/Water separators and Water Quality Inlets
Pv= (liS.+ LCosineH)(WLSmeH) (4)
12
Add a foot beneatii tiie plates fw sediment storage.
Add 6" to 12" above die plates for water clearance so dial tiie oU accumulates above tiie plates.
Add one foot for freeboard.
Add a forebay fw fkiatables and distribution of flow if more tiian one plate unit is needed.
Add after lay fw coUection of the effluent from tbe plate pack area.
For larger units mclude device to remove and stwe oU from the watet surface.
Horizontal plates require tiie least plate volume to achieve a particular removal effidency. However, settleable soUds wUl
accumulate on tiic plates compUcating mamtenance procedures. The plates may be damaged by tiie weight when
removed fw clcamng. The plates should be placed al an angle of450 to 60O so dial settleable soUds sUde to tiie fadlity
bottom. Experience shows tiiat even widi slanted plates some soUds wUl "stick" to die plates because of tiie oU and
grease. Pladng die plates closer ttigctiicr reduces flic plate volume. However, if debris is expected such as twigs, plastics,
and paper, select a larger plate separation distance. Or instaU ahead of die plates a ttash rack andJot screens witii a
diameter somewhat smaUer than thc plate placing.
Recognizmg tiiat an oU/water separatw also removes settleable soUds, it can also be consklered a wet vault (TC2). Tbe
engmeer can use Rgure 2B (See TC2) to estimate tiic effidency of botii tiie conventional and CPI separators. As Rgure
2B does not indude tiie effea of plate technology, a CPI separator should perform considerably better tiian indicated in
Rgure 2B for the same Vj/Vf ratio.
See API (1990) for fiirther design concepts for bodi die conventional and CPI separators.
Maintenance
Check montidy during die wet season and clean several times a year. Always dean in October before die start of die wet
season. Properiy dispose die oU.
REFERENCES
American Petroleum Uistittite (API). 1990, "Design and Operation of OU-Water Separators", Publication 421.
Aquattend, undated, "Design Manual: Innova Sep Particle Separation System", Shawnee Mission, Kansas.
Branion, R., undated, "Prindples fw die Separation of OU Drops from Water in Gravity Type Separators", Departtnent of
Chemical Engineering. University of British Columbia.
Lettenmaier, D. and J. Richey, 1985, "Operational Assessment of a Coalescing Plate Oil/Water Separator", MunidpaUty
of MetropoUtan Seattie.
MettopoUtan Washington Coundl of Govemments (MWCCXJ), March, 1992, "A Current Assessment of Uri>an Best
Management Practices: Techniques fw Redudng Nonpoint Source PoUution in the Coasud Zone".
SUverman, G, 1982, "Wetiands fw OU and Grease Control", Tech Memo. 87, Association of Bay Area Govemments.
Industrial Handbook 5-64 March, 1993
Additional Information — Oil/Water Separators and Water Qual'rty Inlets
TABLE 7A. WATER YISCOSIFIES & DENSITIES
Density of
pure water
Temperature Absolute Viscosity Density in air
•c T (Poises) (siugs/fLsec) (gm/cc) (Ibs/fp)
0 32.0 0.017921 0.00120424 0.999 62J51
1 33.8 0.017343 0.00116338 0.999 62355
2 35.6 0.016728 0.00112407 0.999 62J58
3 37.4 0.016191 0.00108799 0.999 62J60
4 392 0.0I5674i 0.00105324 1.000 62J60
5 41.0 0.0I5I88 0.00102059 0.999 62360
6 42.5 0.014728 0.00098968 0.999 62359
7 44.6 0.014284 0.00095984 0.999 62357
8 .46.4 0.013860 0.00093135 0.999 62354
9 482 0.013462 0.0009O160 0.999 62350
10 50.0 0.013077 0.00087873 0.999 62345
11 51.8 0.012713 0.00085427 0.999 62339
12 53.6 0.012363 0.00084870 0.999 62333
13 55.4 0.012028 0.00080824 0.999 62326
14 572 0.011709 0.00078681 0.999 62317
15 59.0 0.011404 0.00076631 0.999 62309
16 60.8 0.011111 0.00074662 0.999 62299
17 62.6 0.010828 0.00072761 0.999 62289
18 64.4 0.010559 0.00070953 0.999 62278
19 662 0.010299 0.00069206 0.999 62266
20 68.0 0.010050 0.00067533 0.998 62254
Industrial Handbook 5-65 March, 1993
Additional Information — OiUWater separators and Water Quality Inlets
Clear
well \
Oil retention
baffle
Oil Oil separation Flow distribution
skimmer compartment baffle
Water
Inspection and
sampling tee
CONVENTIONAL SEPARATOR
Grit/sludge
removal baffle
Adapted from Romano, 1990
Vfater
outlet
Separator
vault
Coalescing
plates
COALESCING PLATE SEPARATOR
Water
inlet
Flow Adapted from Romano, 1990
bottle
FIGURE 7A. .CONVENTIONAL AND COALESCING
PLATE SEPARATORS
Industrial Handbook 5-66 March, 1993
Additional Information — Oil/Water separators and water QtialityWets
Primary inlet ^
\ /
Ma.nnoies
f Raised Secondary Inlet
for Large Storms
Trash Rack Protects
Two 6 Inch Orifices
Inverted Elbow
Pipe Regulates
Water
Levels Overflow
Pipe
Reinforced
Concrete
Construction
Adapted from Schueler. 1987
NOTE:
1. Size as conventional separator.
2. Design outlet orifice in elbow to limit outftow
to the design rate for the unit
FIGURE 7B. WATER QUALITY INLET
Industrial Handbook 5-67 March, 1993
Additional Information — OllWater separators and Water Quality Inlets
IOO
20 40 60 80 100 120 140 160 180 200
Drop Diam«t*Kntleron)
SIZE
voumE Source: Branion (un<tated)
FIGURE 7C. SIZE AND VOLUME DISTRIBUTION
Industrial Handbook 5-68 March, 1993
Additional Information — Multiple-Systems
Multiple systems may occur in scries w by stacking verticaUy. Mdtiple systems that have been tried or that a^iear to be
feasible are presented betow.
.Stacked sYStems
• Extended detentton above wet pond: used extensively m thc nud-Atiantic states. Recoinmended by several
{ffactioners because of the uncertainty about the performance of wet pcHids.
• Wet pood above sand fUter has been tried in Rorida and Massachusetts and found wanting due to die dogging of
the sand fUter by settieable soUds.
Series .systems
• Extended detention basin - sand fUten standard system in Austin, Texas. SettUng basin is needed to avoid excessive
maintenance on the sand fUter. .
• Detentioa basin - sand fUter - wetland: Large system operating in Rorida.
• Wet pond - wetland: where an unusuaUy high loading of sediment is expected, a fiiU size wet pond, rather than just
a fwebay in tbe wetland, may bc desirable to ntinimize the amount of sediment reaching die wetland wbere it would
be more costiy-to remove.
• BtofUter - wa pood: Used firequentiy in tiic Pacific Northwest again to enhance reliabUity.
• BtofUter - infUtration trench: treatment of the stt»m water before it enters an infUtration system.
• OU/water separator - wetiand w biofUter oil/water separator used to protea the vegetated tteatment system wbere
high concentrations of oU may frequentiy occur.
Industrial Handbook 5-70 March, 1993
BMP: MULTIPLE-SYSTEMS
4.FLOW
INFILTRATION ^»ij£
TRENCH
S
INFILTRATION
BASIN
•FLOW
Considerations
Sa//.s
Cjrea Required^
C^Sh^^
C^ter Availabil^^
Aesthetics
C]^drau/fc H^d^^
Environmental She
Effects
DESCRIPTION i
A multi|de treatment system uses two w more of thc prececUng BMPs in scries. A few
multiple systems have already been described: settUng basia combined with a sand filter;
settiing basin or UofUter combined with an infiltratioo basin w trench; extended detention
zone on a wet pond.
EXPERIENCE IN CALIFORNU
• Thc research wetlands at Fremont Califomia are a combination of wet ponds,
wetlands, and grass biofUters.
SELECTION CRITERIA
• Need to protea a downstream tteatment system
• Enhanced reliabiUty
• Optimum use of the site
LIMTTATIONS
• AvaUable space
DESIGN AND SIZING CONSIDERATIONS
• Refer to intUvidual treatment contrd BMPs
CONSTRUCnONANSPECnON CONSIDERATIONS
• Refer to individual tteatment control BMPs
MAINTENANCE REQUIREMENTS
• Refer to individaal treattneat coatrol BMPs
COST CONSIDERATIONS
Targeted Constttuents
% Sediment
O Nutrients
Q Heavy Metals
Q Toxh Materials
9 Fhatable Materials
O Oxygen Demand-
ing Substances
O Oil & Grease
O Bacteria & Viruses
9 Ukely to Have
Significant Impact
O Probable Low or
Unknown Impact
Implementation
Requirements
# Capital Costs
# O&M Costs
9 MaintenarKe
O Training
High O Low
ICS
Best^
Management
Practices^
Industrial Handbook 5-69 March, 1993
APPENDIX 8
INDUSTRIAL / MUNICIPAL PROPRIETARY BMPS
CDS is the most effective system for the sustainable removai and
retention of suspended solids aind floatables from storm water.
REMOVES POLLUTANTS
The Continuous Deflective Separation (CDS) teclinology
utilizes a non-blocking, non-mechanical screening process
to remove pollutants from storm water flow and combined
sewer overflows (CSO). CDS units capture fine sands
and solids and are capable of removing more than 80%
of annual total suspended solids from storm water.
Additionally, CDS units remove 100% of floatables and
100% of all particles in the storm water which are equal
to or greater than one-half the size of the screen opening.
Studies show the units remove 93% of all particles which
are one-third the size of the screen opening, and 53% of
all particles one-fifth the size of the screen opening.
A conventional oil baffle within a CDS unit effectively
controls oil and grease in storm water. With the addition
of sorbents, the permanent capture efficiency of oil and
grease is increased to 80-90%. The combination of a
conventional oil baffle and particulate sorbents is a unique
feature of a CDS storm water treatment unit. Once
pollutants are captured in a CDS unit, they cannot escape.
PROVEN TECHNOLOGY
The CDS technology has been proven by extensive
independent laboratory studies and hundreds of actual
installations in the United States and Australia. Copies of
these performance reports are available at our web site,
or by contacting our offices.
APPROVEO BEST MANAGEMENT PRACTICE
The CDS technology has achieved approval as a Best
Management Practice (BMP) by municipalities and state
DOTS throughout the United States. The USEPA lists CDS
as a structural BMP.
1) Raw storm water enters the
CDS unit's diversion chamber.
(?) A diversion weir guides the
flow into the unit's separation
chamber where a vortex is
formed.
Standard CDS Unit Capacities and Physical Features
Manufacture
Material
Model
Designation
Approximate
Impervious
Catchment
Area (Acres)
Treatment Capacity
Q water qualily
Screen
Diameter/Height
(It)
Sump
Capacity
(yd3)
Depth Below
Pipe Invert
(ft)
Foot Print
Diameter
(It)
Manufacture
Material
Model
Designation
Approximate
Impervious
Catchment
Area (Acres) cfs MGD
Screen
Diameter/Height
(It)
Sump
Capacity
(yd3)
Depth Below
Pipe Invert
(ft)
Foot Print
Diameter
(It)
Precast
Concrete
PMSU 20J5 1-4 0.7 0.5 2.0/1.5 1.1 5.1 6.0
Precast
Concrete
PMSU 20_20 2-6 1.1 0.7 2.0/2.0 1.1 5.7 6.0
Precast
Concrete
PMSU 20_25 3-9 1.6 1.0 2.0/2.5 1.1 6.2 6.0
Precast
Concrete
PSW & PMSU 30_28 6-17 3.0 1.9 3.0/2.8 1.4-2.1 6.9 6.0-6.5
Precast
Concrete
PSWC & PMSU AO JO 12-33 6.0 3.9 4.0/4.0 1.9 9.7 8.3
Precast
Concrete PSWC 56_40 & 50_40 & 50_50 18-61 9 & 11 5.8 & 7.1 5.6 / 4.0 & 5.0/5.0 1.9 9.7 9.5 Precast
Concrete
PSWC 56_53 28-78 14 9 5.6/5.3 1.9 10.8 9.5
Precast
Concrete
PSWC 56_68 38-106 19 12 5.6/6.8 1.9 12.5 9.5
Precast
Concrete
PSWC 56_78 & PSW 70_70 50-144 25&26 16&17 5.6 / 7.8 & 7.0/7.0 1.9-3.9 13.5 9.5
Precast
Concrete
PSW100_60 60-167 30 19 10.0/6.0 6.9-14.1 12.0 17.5
Precast
Concrete
PSW100_80 100-278 50 32 10.0/8.0 6.9-14.1 14.0 17.5
Precast
Concrete
PSW 10OJ 00 128-356 64 41 10.0/10.0 6.9-14.1 16.0 17.5
Fiberglass Premanufactured fiberglass units are available to treat small flows of 1 to 3 cfs
Cast-ln-Place
Concrete CDS cast-in-place reinforced concrete units can be designed to treat flows up to 300 cfs
(¥) The vortex spins all floatables
and most suspended solids to
the center of the separation
chamber.
)The separation screen will not
become blocked due to the
washing vortex, but it will allow
liquid to move through.
(^The screened liquid which
passes through the process
quickly moves toward the
outlet.
^0)The diversion weir is designed
to bypass excessive flows
without affecting the proper
operation of the CDS unit or
storm drain system. Bypass
flows will not wash out any of
the captured pollutants.
(J)The cleaned water then moves
- freely to the receiving water.
(S^The cleaned storm water moves out
of the separation chamber and into
the diversion chamber downstream
from the diversion weir.
7 )The sump can be equipped with an optional
basket to facilitate emptying the unit, or simply
clean with a vactor or clam bucket.
6) Suspended solids gently settle into
a sump where they remain until they
are removed.
EXTREMELY LOW MAINTENANCE
CDS units are self-operating. They have no moving parts
and they are entirely gravity driven, requiring only the
hydraulic energy available within the storm water flow.
The screens and supporting hardware are stainless steel
and will resist corrosion.
CDS units have very large sump capacities relative
to their design flows, and only need to be cleaned out
with a standard vactor truck approximately one to four
times per year. This operation eliminates workers' expo.sure
to the materials captured in the units.
KEY FEATURES anti BENEFITS
Uses
• Slorm Water Treatment
• Combined Sewer Overflow Treatment
• Dry Weather Flow Diversion
Applications
• Capture and retention of suspended solids,
sand, floatables, oil and grease, and other
gross pollutants from:
• Commercial Service and Parking Areas
• Industrial Areas
• Public Property and Parkland
• Residential Streets and Private Property
• Pretreatment for:
• Wetlands, Ponds, and Swales
• Media and Sand Filters
• OilA/Vater Separators
ElticienI
• Highly effective (up to 90%) in capturing
and retaining sediment as small as one-
third the screen aperture.
• Captures and retains 100% of floatables
and all other material greater than the
screen aperture.
Cost-Effective
• CDS provides the lowest cost per CFS
(Cubic Feet per Second) processed when
compared to other structural BIVIPs.
Large Flow Range
• From 0.7 to 300 CFS.
Non-Blocking and Non-Mechanical
• Standard CDS units have no moving parts.
They require no power or supporting
infrastructure, and they will not clog.
Unobtrusive and Easy to Install
• CDS units are compact and are installed
below ground, so space requirements are
modest. They are ideal for new construc-
tion as well as retrofit or redevelopment.
Low-Cost, Safe and Easy Pollutant Removal
• Maintenance is easy using standard vactor.
clam, or basket equipment which mini-
mizes maintenance personnel exposure
to hazardous material.
Improves Discharge Waler Quality
• Removes floatables and suspended solids
from storm water runoff.
• Removes free oil and grease with the use
of an oil baffle, and/or sorbents.