HomeMy WebLinkAboutCT 04-06; PALOMAR POINTE; WATER QUALITY PLAN & STORM WATER MANAGEMENT PLAN; 2005-01-01I
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K&S ENGINEERING
Planning Engineering Surveying
WATER QUALITY PLAN
&
STORM WATER MANAGEMENT PLAN
For
PALOMAR POINTE PROJECT
College Boulevard
Carlsbad, CA
CT 04-06
Prepared For:
LANlKAI DEVELOPMENT COMPANY
1815 Aston Avenue, Suite 106
Carlsbad, CA 92008
USA
Prepared By:
K&S Engineering
7801 Mission Center Court, Suite 100
San Diego, CA 92108
January 2005
K&S Job #02-084
RECEIVED
JAN 2 (1 2005
ENG\NEER~G OE?AR'·Mt:.~T
7801 Mission Center Court, Suite 100 • San Diego, California 92108 • (619) 296-5565 • Fax (619) 296·5564
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TABLE OF CONTENTS
Section Page
1.0 Introduction.. ......... ... .. . .. . ..... . ........ ....... . .... . ... .. ... .. ........ .. .... ..... ......... ......... ... .. 2
Figure 1 -Location Map ................... '" .................................................... '" . ..... 3
2.0 Project Background .......................... " ...... . ... ... .. ....... ... .. ... .... ........ ......... .......... 5
2.1 Hydrologic Unit Contribution.... .. .... . ....... .... .................. ... ........ ......... ......... . . 6
Figure 2 -Carlsbad Watershed.. ........ ... ......... .......... ................................ ............. 6
2.2 Beneficial Use ............................................................. :... ...................... 7
Table 1 -Beneficial Use.. ..... ................ ... .................... . ......... .. .... ........... ........ .. 7
Figure 3 -Vicinity Map.................................................................................... 8
3.0 Characterization of Project Runoff .......................................................................... ·" 10
3.1 Constituents ofConcem and Sources............................................................ 10
Table 2 -Pollution Potential by Development Element. ................. , ....... '" ........ '" .... ... . 10
3.2 Soil Characteristics ........... ~.. ... ......... ........ ............... ....... ..... ....... ............. i2
3.3 Site Hydrology....................................................................................... 12
4.0 Response to Planning Department Review................................................................ 14
4.1 Industrial Development............................................ ................................ 14
4.2 Parking Lots......................................................................................... 14
4.3 All Development.................................................................................... 15
Table 3 -Enhanced Treatment Control Efficiency ........... " ............................... " . .. . . . . . 15
5.0 Project BMP Plan Implementation......................................................................... 17
5.1 Construction BMP. . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . .. . . . . .. . . . . . . . . . . ... . . . . . . . . . . . . . . . .. . .. . .. . . 17
5.2 Post-Construction BMP Options ................................... '" .................. '" ....... 17
5.3 Fiscal Resources.................................................................................... 18
Table 4 -BMP Maintenance Program ..................................... '" ....... .. ...... ...... . .. .. 19
Table 5 -Post Construction BMP Yearly Estimated Operation & Maintenance (O&M) Costs ... 20
6.0 Conclusion .............. '" ......... " ......... '" ....... '" .. . ... .. . ..... .. .... . .. ....... .. . .. ...... .... .. ... . . 22
Certification .............. " ........................................................................ , ..... .... . 24
Attachments.................... ......... ............................................................ .......... 25
Project Information Site Map .................................................................... .
Post Construction BMP Site Map ................................................................. .
APPENDICES
1. Post Construction Treatment Control BMPs
2. Post Construction Proprietary BMPs, FloGard technical information.
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1.0 INTRODUCTION
The California State Water Quality Control board approved Order Number 2001-01 (Order) on
February 21,2001. The Order outlines the stOrln water discharge requirements for municipal stonn water
systems, which drain "development" areas from watersheds within
1.) The County of San Diego,
2.) mcorporated cities of San Diego County, and
3.) San Diego Unified Port District.
The City of Carlsbad is identified as one of the municipal co-pennittees in the order and, therefore, subject to its
requirements.
This Water Quality Technical Report was prepared to defme the potential Best Management Practice (BMP)
options that satisfy the requirements, identified in the following documents:
1.) City of Carlsbad Standard Urban Stonn Water Mitigation Plan, Stonn Water Standards,
2.) Standard Specifications for Public WorJ>.s Construction,
3.) NPDES General permit for Stonn Water Discharges Associated with Construction Activity, and
4.) County of San Diego Municipal NPDES Stonn Water Permit (Order Number 2001-01).
Specifically, this report includes the following: " "
1.) Project background, hydrological unit (HU) location and HU beneficial uses
2.) Characterization of anticipated project runoff, including constituents of concern and soil characteristics
3.) Response to the water quality concerns endemic to this development, included in Preliminary Review
from City Planning Department.
4.) Construction and pennanent BMP,device infonnation for this development.
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Figure 1
CITY OF OCEANSIDE
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OCEAN
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CITY OF ENCINITAS
LOCATION MAP
NOT TO SCALE
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SECTION 2.0
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2.0 PROJECT BACKGROUND
A preliminary Drainage StudylHydrology Report for Palomar Pointe ("Project") is being prepared and
submitted by K&S Engineering to the City of Carlsbad (City) concurrently with the submittal of this document.
It is included as an Attachment to this report for convenience.
In general, the Order requires that BMPs;
1.) Control the post-development peak storm water storm discharge rates and velocities to maintain or
reduce pre-development downstream erosion
2.) Minimize storm water pollutants of concern in urban runoff from new development through
implementation of source control BMPs,
3.) Remove pollutants of concern from urban runoff through implementation of structural treatment BMPs
4.) Include proof of a mechanism, to be provided by the "Project" proposal, which will ensure ongoing
long-term structural BMP maintenance .
Also structural BMPs shall be located so as to infiltrate filter, or treat the required runoff volume or flow
(numeric sizing criteria) prior to discharge to any receiving·waterbody supporting beneficial uses.
From a storm water quality perspective, the Order requires the implementation of storm water BMPs. The BMP
-design criteria, pursuant to the Order, are either volume-or-flow-based. Specially, volume-based BMPs must be
designed to treat the volume of runoff produced from a 24-hour 85th percentile storm event. In general, this is
equal to 0.6 inches of runoff for San Diego County.
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 entering the storm drain system, or removed
completely and allowed to percolate via a retention pond. Note that the preliminary BMP components identified
in Section 5.0 were sized using the flow-based criteria. Preliminary volume calculations were also performed to
evaluate the use of retention basins.
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2.1 Hydrologic Unit Contribution
The "Project" is located in the Los Monos hydrologic sub-area (HSA) (904.31) of the Agua Hedionda
hydrologic area of the Carlsbad watershed hydrologic unit. The area is characterized by moderately sloping land
occupied by predominately non-native grass. The drainage from this "Project" will discharge into City
underground storm drainage systems in College Boulevard, eventually feeding into the Agua Hedionda Lagoon,
which then flows into the Pacific Ocean. .
The "Project" will not alter the overall drainage pattern of the site before entering the storm drainage system. A
slight increase in impervious area (as a percentage of the total HSA) will be experienced because of the
"Project" development.
The "Project" represents a negligible percentage (0.01%) of the overall watershed area of approximately
210 square miles. Approximately 6.6 acres of the 13.47 acre vacant site will be occupied by three
industrial/commercial buildings together with associated parking areas, vehicular access and parking, pedestrian
< .. areas and landscaping. Based on the County Hydrology Manual, September 2001, the runoff coefficient will
-increase from 0.325 to 0.85.
Figure 2
Approximate Project
location
Carlsbad Watershed
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2.2 Beneficial Use
The beneficial uses of inland surface water and groundwater for this hydrologic unit are included in Table 1.
The data contained in this Table has been extracted from the Water Quality Control Plan for the San Diego
Basin.
TABLE 1
Beneficial Uses Inland Surface Coastal Waters Ground Water Water
Municipal and Domestic Supply X X
Agricultural Supply X X
Industrial Service Supply X '« X X
Navigation X
Hydropower Generation X ,.
Contact Water Recreation X X
Non-Contact Water Recreation X X
Commercial and Sport Fishing X
Warm Freshwater Habitat X X
Cold Freshwater Habitat X
Estuarine Habitat X
Wildlife Habitat X X
Biological Habitats X
Rare, Threatened, or Endangered X X
Marine Habitat X
Migration of Aquatic Organisms X
Aquaculture X
Shellfish Harvesting X
Spawning, Reproduction and/or Early X Development
Beneficial Use
The reader is directed to Chapter 2 of the State Water Resources Control Board's Water Quality Control Plan
for the San Diego Region Basin (Basin Plan) for more detailed descriptions of the above beneficial uses.
(bttP://YI'I1'w.swrcb.ca.gov//·11,'qcb9Iprograms/Clzapter%202 %20BeneOcial%20Uses. pdO
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SECTION 3.0
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3.0 CHARACTERIZATION OF PROJECT RUNOFF
According to the California 2002 303d list published by the San Diego Regional Water Quality Control Board,
Agua Hedionda Creek and Agua Hedionda Lagoon are the only impaired water bodies downstream of the
"Project". The "Project" area is approximately 3.5 miles upstream from the outlet of the lagoon to the Pacifi~
Ocean.
The Agua Hedionda Creek's total dissolved solids for a length of7 miles and a TMDL classification of "Low".
The identified sources of the pollutantlstressor are listed as:
• Urban Runoff/Storm Sewers.
• Unknown Nonpoint Source.
• Unknown point source.
The Agua Hedionda Lagoon's pollutantlstressors are bacteria indicators and sedimentation/siltation for an area
qf 6.8 acres and a TMDL classification of "Low" on, both. The identified source for both of the
p~_~lutantlstressors is listed as nonpointlpoint source. ..
3.1 Constituents of Concern and Sources
, <
There are no sampling data available for the existing site condjtion. In addition, the project is not expected to
generate significant amounts of non-visible pollutants. However, the constituents listed in Table 2 are commonly
found on similar developments and could affect water quality:
TABLE 2
Pollution Potential by Development Element
, Constituents of Concern Priority Trash Oxygen Bacteria Project Heavy Organic· Oil &
Categories Sediments Nutrients Metals Compounds & Demanding Grease & Pesticides
Debris Substances Viruses
Commercial
Development p(l) p(l) p(2) X p(3) X p(4) p(3)
greater than
100,00 ft2
Parking Lots p(1) p(1) X X p(1) X p(3) p(3)
X = anticipated
P = potential
(1) A potential pollutant iflandscaping exists on-site.
(2) A potential pollutant if the project includes uncovered parking.
(3) Including Solvents.
(4) A potential pollutant ifland use involves food or animal waste products.
.
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Constituents of Concern General Pollutant Categories
The potential sources for the constituents of concern for the project could be, but are not limited to those
listed below:
o Sediments -Sediments are soils or other surficial materials eroded and then transported or deposited by the
action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills, reduce spawning habitat,
lower young aquatic organisms survival rates, smother bottom dwelling organisms, and suppress aquatic
vegetation growth.
o Nutrients -Nutrients are inorganic substances, such as nitrogen and phosphorus. They commonly exist in the
form of mineral salts that are either dissolved or suspended in water. Primary sources of nutrients in urban run-off
are fertilizers and eroded soils. Excessive discharge ofnutrients:to water bodies and streams can cause excessive
aquatic algae and plant growth. Such excessive production, referred to as cultural eutrophication, may lead to
excessive decay of organic matter in the water body, loss of oxygen in the water, release of toxins in sediment, and
the eventual death of aquatic organisms.
o ~ -Metals are raw material components in non-metal pi:oducts such as fuels, adhesives, paints, and other
~ coatings. Primary source of metal pollution in storm water are 1;rpically commercially available metals and metal
'~.products. Metals of concern include cadmium, chromium, copper, lead, mercury, and zinc. Lead and chromium
'have been used as corrosion inhibitors in primer coatings and 'cooling tower systems. At low concentrations
:'naturally occurring in soil, metals are not toxic. However, at higher concentrations, certain metals can be toxic to
..aquatic life. Humans can be impacted from contaminated groundw~ter resources, and bioaccumulation of metals in
fish and shellfish. Environmental concerns, regarding the potential for release of metals to the environment, have
,already led to restricted metal usage in certain applications. .
o 'Organic Compounds -Organic compounds are carbon-based. 'Commercially available or naturally occurring
.organic compounds are found in pesticides, solvents, and hydrocarbons. Organic compounds can, at certain
concentrations, indirectly or directly constitute a hazard to life or health. When rinsing off objects, toxic levels of
solvents and cleaning compounds can be discharged to storm drains. Dirt, grease, and grime retained in the
cleaning fluid or rinse water may also adsorb levels of organic compounds that are harmful or hazardous to aquatic
life.
o Trash & Debris -Trash (such as paper, plastic, polystyrene packing foam, and aluminum materials) and
biodegradable organic matter (such as leaves, grass cuttings, and food waste) are general waste products on the
landscape. The presence of trash & debris may have a significant impact on the recreational value of a water body
and aquatic habitat. Excess organic matter can create a high biochemical oxygen demand in a stream and thereby
lower its water quality. Also, in areas where stagnant water exists, the presence of excess organic matter can
promote septic conditions resulting in the growth of undesirable organisms and the release of odorous and
hazardous compounds such as hydrogen sulfide.
o Oxygen-Demanding Substances -This category includes biodegradable organic material as well as chemicals
that react with dissolved oxygen in water to form other compounds. Proteins, carbohydrates, and fats are examples
of biodegradable organic compounds. Compounds such as ammonia and hydrogen sulfide are examples of
oxygen-demanding compounds. The oxygen demand of a substance can lead to depletion of dissolved oxygen in a
water body and possibly the development of septic conditions.
o Oil and Grease -Oil and grease are characterized as high-molecular weight organic compounds. Primary
sources of oil and grease are petroleum hydrocarbon products, motor products from leaking vehicles, esters, oils,
fats, waxes, and high molecular-weight fatty acids. Introduction of these pollutants to the water bodies are very
possible due to the wide uses and applications of some of these products in municipal, residential, commercial,
industrial, and construction areas. Elevated oil and grease content can decrease the aesthetic value of the water
body, as well as the water quality.
o Pesticides -Pesticides (including herbicides) are chemical compounds commonly used to control
nuisance growth or prevalence of organisms. Excessive application of a pesticide may result in run-off
containing toxic levels of its active component.
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3.2 Soil Characteristics.
The "Project" area consists of soil group D. Soils of group D are in the low range for allowing rain fall to
percolate into the native soil types. Group D soils have very slow infiltration rates when thoroughly wetted.
They are chiefly clays that have a high shrink-swell potential or have a high permanent water table. They are
soils that have a claypan or clay layer at or near the surface, or soils 'that are shallow over nearly impervious
material. Rate of water transmission is very slow.
3.3 Site Hydrology.
The existing flows of the natural areas, as well as the proposed drainage, can be separated into three
watersheds, Areas A, B & C (see watershed maps in Project's Hydrology Report, submitted separately.)
Existing Area A comprises approximately 80% of the site and drains to a detention basin at the northwest comer
of the sit~ It then enters a 24" RC pipe that connects to the City's stOrm drain system. Existing Area C drains
southerly to: the future golf course and an exiting natural drainage chamf€l. Existing Area B drains southwesterly
to an 18" RC pipe connecting to the City's storm drain system in College,Boulevard.
The Proj~ct's proposed drainage basin areas are approximately the s~me as the existing. The onsite, private
storm drain"'system has been sized for the lO-year storm events. The det~ntion basins are sized for the 100-year
storm event: Increased flows from Area A (approximately 80% of the site) will be reduced by increasing the
capacity of im existing detention basin in the northwest comer. A second, smaller detention basin is constructed
to handle increased flows from Area C. Flows from this basin will outflow to the private driveway and then the
public street, before interception by a curb inlet, which has the capacity to intercept a Q(50) of 4.47 cfs. This
will outlet to an energy dissipator constructed on the golf course site to decrease flow velocity discharging to an
existing drainage course. This outlet will eventually be connected to the golf course drainage system. These two
detention basins will reduce all onsite flows, except for drainage from the public street and the private entry
drive, to existing flow amounts
Therefore no increase in flow is experienced after development of the site from Areas A & c. The net
increase in flows from Area B, due to development of the public street and private entry drive, has minimal
impact to the downstream properties. Area B flows into an existing 18" RC pipe at College Boulevard that will
flow less than Y2 full during a 100 year flow. At the pipe outlet, an existing rip-rap energy dissipator reduces the
flow velocity into a deep natural canyon.
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SECTION 4.0
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4.0 RESPONSE TO CITY PLANNING DEPARTMENT REVIEW
As mentioned in the introduction, the "Project" must be designed in compliance with all applicable stormwater
and water quality ordinances. This includes incorporating BMPs that minimize runoff contamination and
volume from the site. The following narrative identifies specific BMPs that may be used in conjunction with the
development land-use identified in the Staff Report.
4.1 Industrial Development
In order to meet the specific industrial development requirements of the site, an erosion control and BMP plan
will be prepared that provides calculations for the required treated volume of runoff and/or treated discharge,
and location of construction and post-construction BMP devices. The following BMPs need to be used, in
addition to the B:M;.Ps identified in Section 5.0 that meet the industrial developm.¢nt criteria:
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• The feasibility of using porous materials near walkways and the useo-'of design elements to' reduce
directly connected impervious areas will be evaluated during final design. Note that the ability to use
porous mategal infiltration devices may be limited due to the use of curbsJo direct flow to catch basins.
• Runoff from driveways, streets and other impervious surfaces will be treated by media filter devices
such as catch basin inserts or in-line pollutant traps. The use ofvegetated.(biofilters) and/or gravel filter
strips may al$o be incorporated, where feasible. .
• Erosion control measures will be used during construction and also implemented as a part of the
"Project" NPDES post-construction BMP plan. K&S will prepare a construction Storm Water Pollution
Prevention Plan (SWPPP) for Palomar Pointe. The SWPPP will be available pending final approval of
the construction documents. (See Appendix 1 for examples of construction BMPs.)
• Selected Post-construction BMPs are designed in accordance with the Order and California Stormwater
Best Management Practices handbook. (See Appendix 2 for examples ofPost .. construction BMPs.)
• BMP operation and maintenance shall be evaluated on a continuing basis. Maintenance guidelines and
cost are identified in Tables 4 and 5 at the end of Section 5.3. It is anticipated that either the individual
lot owners, owner's association or a private, property management company maintenance service are
responsible for the maintenance of the BMPs.
4.2 Parking lots
Runoff from parking lot areas will be treated through the use of detentionldesilt basin, media filtration devices,
or other feasible BMPs such as vegetated strips, biofiltration and in-line treatment structures.
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4.3 All Development
A public education and landscape management plan will be incorporated into the "Project". The elements of the
plan may consist of catch basin stenciling, public awareness signs, and herbicide/pesticide management. These
elements will be addressed in a water quality/urban runoff control plan (Plan) for the "Project", and are subject
to the municipal code.
All landscaped and undisturbed natural areas will act as biofilters for irrigation and drainage flow waters.
Mulching, seeding and planting of the landscaped areas provide biofiltration of applied pesticides and fertilizers.
Following manufacture( guidelines to avoid over treatment of landscaping will provJde a limited occurrence in
the planted areas of the ·'Project".
TABLE 3
E h n ance dT t t c t I BMP Eft" rea men on ro IClency
Pollutant of 'e Treatment Control BMP Categories ,
Concern '~ --
Detention Infiltration Wet Ponds Drainage Hydrodynamic
Biofilte.rs Filtr~tion Separator Basins Basins(1) orWetJands Inserts Systems(2)
Sediment M# H H H L til M
Nutrients L M M M L M L
Heavy M M M H L H L Metals -
Organic U U U U L M L Compounds
Trash & L H U U M H M Debris
Oxygen
Demanding L M M M L M L
Substances
Bacteria U U H U L M L
Oil & Grease M M U U L H L
Pesticides U U U U L U L
(1) Including trenches and porous pavement.
(2) Also known as hydrodynamic devices and baffle boxes.
L: Low removal efficiency)
M: Medium removal efficiency)
H: High removal efficiency)
U: Unknown removal efficiency
Sources: Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters
(1993), National Storm water Best Management Practices Database (2001), and Guidefor BMP Selection in
Urban Developed Areas (2001).
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SECTION 5.0 .
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5.0 PROJECT BMP PLAN IMPLEMENTATION
This section identifies a preliminary BMP plan design that meets the above water quality criteria requirements.
The plan was developed per the proposed roadway and lot layout/density associated with the site. BMPs other
than those identified in the plan, may be used during final engineering.
The following Sections address the use of construction-and post-construction BMPs. Note that the two BMP
"Project" components are discussed in Sections 5.2.
5.1 Construction BMP
K&S will prepare a Strom Water Pollution Prevention Plan (SWPPP) for the "Project". The ~oject SWPPP will
identify and detail construction BMPs. Temporary BMPs include, but are not necessarily limited to the
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• silt fences, fiber rolls, storm drain inlet protection, stockpile management, solid water"management,
stabilized construction exit, vehicle and equipment maintenance, erosion control mats ~nd spray-on
applications, gravel bag b~rms, material delivery and storage, spill prevention and conti-ol, concrete
water management, water~ conservation practices, paving and grinding operations, stabUization of
disturbed areas, permanet!t revegetation of man-made slopes.
The SWPPP will be available penqing final approval of the construction documents.
During construction, the temporarY BMPs employed will be consistent with the NPDES Strom Water Pollution
Prevention Program. The objectives of the SWPPP are to:
1.) Identify all pollutant sources, including sources of sediment that may affect the water quality of
stormwater discharges associated with construction activity from the "Project" site;
2.) Identify nonstormwater discharges; ,
3.) Identify, construct, implement (in accordance with a time schedule) and maintain BMPs to reduce or
eliminate pollutants in stromwater discharges and authorizednonstormwater discharges from the
"Project" site during construction; and ,
4.) Develop a maintenance schedule for BMPs installed during construction designed to reduce or
eliminate pollutants after construction is completed (post-construction BMPs). BMPs, in addition to
desilting basins, may include silt fences, sand bags, and gravel bags. (See Appendix 1 for Construction
BMPs.)
5.2 Post-Construction BMP Plan
K&S has identified two preliminary water quality BMP planning components for the "Project" that satisfy
agency storm water requirements.
The "Project" will utilize detentionldesilt basins and FloGard+™ catch basin inserts as the preferred BMP
components. See Post Construction BMPs Site Map (Attachments) for locations.
Component 1: Provide 2 detentionldesilt basins.
Component 2: Provide FloGard+™ catch basin inserts at each inlet location, which does not discharge to a
detention/desilt basin, with notice of necessary maintenance to property owner.
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5.3 Fiscal Resources
The owner/developer of the project will be financially responsible for construction/installation of the post-
development BMPS and implementation of the SWPPP. An association/property management company shall
perform the maintenance of the catch basin inserts, detention basins and biofilter swales, as well as the private
onsite storm drains and landscaping.
Most of the permanent BMPs accrue minimal maintenance costs. Mulching, seeding and plantings are part of
a continuing landscape maintenance program. Landscaping maintenance for permanent stabilization of graded
areas will be the responsibility of the owner/developer through the association/property management company.
A maintenance contract entered into with the FloGard™ insert provider upon installation will insure a
continued monitoring of all catch basin inserts of the Project. The contract provides for necessary maintenance
and needed repairs to continue insert effectiveness for the length of the contract. .
Installation and maintenance of the post-development BMP's will be the responsibility of the
owner/developer under a BMP Maintenance Agreement. A security will be required to back-up the Maintenance
. Agreement to equal the cost of two years maintenance activities and the agreement will remain in place for an
interim period of five years.
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The permanent responsibility oftli~'post-development BMP's will remain with the property by ~..ay of the m;e
of restrictive CC&R language. The "'CC&R language will place the responsibility for all future "maintenance
upon the owner record.
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TABLE 4
BMP Maintenance Program
A schedule of periodic maintenance should be i~plemented and modified, as needed, to insure effective operation of the indicated BMPs. As a guideline, a tentative schedule of maintenance frequency follows. The
schedule is based on certain indicators outlined for a particular BMP. I
BMP ROUTINE ACTIONS I MAINTENANCE INDICATORS I FIELD MEASUREMENT I FREQUENCY I MAINTENANCE ACTIVITY
FloGard+™ Inserts Sediment removaL : Sediment more than 1/2 height of filter ; Visual inspection of filter body. I After each rain event. I Remove and properly dispose of sediment.
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Trash and debris removal. I Sufficient trash or debris accumulation : Visual in'spection of inlet and filter I After each rain event. i Remove and properly dispose of trash and I to hinder filter performance. ~ insert. I debris accumulation. --j
Oil and grease removal. I Absorbent medium dark gray or darker ; Visual ~pection of adsorbent filter After each Target 2 (0.75") rain Replace adsorbent media within 10 working I and saturated with oil. i media. event. days. Characterize and properly dispose of
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I spent media prior to wet season. i I
Structural integrity of insert. i Broken or damaged insert with visible i Visual inspection of insert components. Semi-annually, May and October. I Replace insert. Contact vendor to develop I rips, tears, gashes and/ or fallen media. I I I preventative procedures. Effect repairs
I I within 10 working days.
Annual renewal of adsorbent medium. I End of wet season. I Lack of precipitation for extended Annually before wet season. Remove, characterize and properly dispose
I i period. of spent media. Replace adsorbent media
I I before start of wet season. i
Biofilters Height of vegetation. I Average height of vegetation (grass) I Visual inspection of vegetation. Inspect weekly and after rainy Cui: vegetation as required.
I i I exceeds 4" . i periods.
Assess adequate cover. I Bare spots appear in planted/ mulched I Visual inspection of lack of Assess growth on a monthly basis. Reseed vegetated areas as required. No later I areas or less than 70% coverage over I vegetative/ mulch cover. Record Assess mulch coverage on a monthly than November. Scarify area for reseeding.
entire area. ! locations to identify persistent problem basis. Reapply mulching as required to cover bare
I areas. spots.
, Inspect for debris accumulation. I "Qebris or litter accumulation. ! Visual inspection Sor trash. During routine site landscape , Remove and properly dispose of trash, litter
i I maintenance. and debris.
Inspect for accumulation of sediment or I Sediment is at or near vegetation height. I Visual inspection for sediment depth. Inspect monthly and after each Remove accumulated sediment when
erosion of soil .. I Rills or gullies in topsoil. : Visual inspection for rills and soil significant rainfall. interfering with drainage flows.
" ., erosion. .. ~
Detention Basin Inspect for standing water. Standing water for more than 72 hrs. Visual observation for three consecutive Annually, three days after every Drain facility. Check & clear clogged inlet
days with no change in water leveL Target 2 (0.75") rain event. structure.
Weekly and after rainfall. Notify engineer to investigate remedial
Seasonally, wet and dEY. procedures to achieve acceptable infiltration.
Inspect for trash and debris. Trash or debris present. i Visual observation of trash or debris During routine trashing per Remove and properly dispose of I accumulation in basin or structures. scheduled landscape maintenance: accumulated trash and debris.
Inspect for sedimentation Sediment storage zone 1/2 full. i Visual inspection for sediment Annually and after rainfall. Remove stone aggregate and filter fabric.
accumulation. l accumulation in stone aggregate at inlet Wash stones and fabric. Remove
i structure filter fabric. accumulated sediment. Reinstall filter fabric I (replace if necessary) and stones to design
i parameters prior to wet season .. I
General maintenance inspection. Inlet structure, outlet structure, filter fabric i Visual inspection of all components. Twice per year, late wet and dry Remove excess vegetation.
damaged or other features damaged. ,
Regrade and replant slopes, if eroded. : seasons. Vegetation height exceeds 12" or woody Consult engineer if no immediate Make-all necessary repairs, as required, prior vegetation/ trees emerge. I
Evidence of erosion or compromising of slope i solution evident. to wet season. Notify engineer if immediate
stability. remedies are not evident.
--Safety fence damage.
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TABLES
POST CONSTRUCTION BMP YEARLY ESTIMATED
OPERATION AND MAINTENANCE (O&M) COSTS
Pennanent BMPs constructed and installed for this project will necessitate continuous operation and maintenance when the project is complete. O&M costs are based upon California
Department of Transportation estimated costs for 'pilot BMP project utilizing prevailing wage rates. Below are the itemized costs of the project BMPs, based on the pilot project, as shown on the
Post Construction BMP Site Map (see Attachments). I
As identified in Section 5.3, Fiscal Resources, the source for funding ofBMP operation and maintenance is the responsibility of the property owner(s) andlor owners association. , I I
Post construction permanent BMP operation and maintenance costs include, but are not limite4 to, the following: I
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PERMANENT BMP YEARLY OPERATION & MAINTENANCE COSTS
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BMP OPERATION & MAINTENANCE LABOR EQUIPMENT MATERIALS TOTALeOST ,
ITEM
Per Hrs. Rate Cost Type Days Rate Cost Item Cost
CATCH BASIN FILTER INSERTS 20.0 43.63 $872.60 1 Ton Truck 2.5 26.84 $67.10 New Adsorbent, $300.00 $1,239.70 Testing & Disposal
Trimmer, Rake,
1 Ton Truck, Fork, Bags, Safety
DETENTION BASIN 43.0 43.63 $1,876'.09 Backhoe, 3.0 98.86 $296.58 Equipment, Seed, $500.00 $~,672.67 , , Hydroseeder Erosion elanket,
Testing & Disposal
HYDROSEEDING*/BIOFIL TERS 24.0 43.63 $1,047.12 1 Ton Truck, 3.0 48.15 $144.45 Seed, Binder $100.00 $1,291.57
'" '" Hydroseeder ... I O&M TOTAL $5,203.94
* Only Required if Site not Constructed 30 Days after Grading.
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-, -SECTION 6.0 ,-.,
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...
6.0 CONCLUSION
This Plan has been prepared to define potential Best Management Plan (BMP) components that satisfy the
requirements identified in the following documents:
1.) Carlsbad Municipal Code Stormwater Management and Discharge Control Ordinance,
2.) Standard Specifications for Public Works Con~truction,
3.) NPDES General Permit for Storm Water Dis~harges Associated with Construction Activity issued by
the State Water Resources Control Board, and
A Flowgard™-Plus Catch Basin Insert cleanses 0.36 C.F.S. per Square foot of effective catch basin area (see
manufacture's specifications attached on Appendices ~ection 3).
Basin area formula -A=QICI !
Q: Proposed Catch Basin = 2'x 2' = 4 S:F. of Effective Area
The Clean Flow Rate for a 2'x 2' Catch Basin will be 4 S.F. x 0.36 C.F.S./S.F. = 1.44 C.F.S.
C: C runoff Coefficient = 0.95 (iridustrial soil group "D")
I: 1= 0.2 inlhr (see i below) ...
A -Basin area QICI
1.44/(0.95)(0.2)= ,1.44/.19 = 7.58Ac
The proposed insert for a 2'x 2' catch basin will easily ~andle the maximum flow rate of any basin area of this
project.
The detentionldesilt basins sizing criteria is for a 100 yr storm event. All basin computations are outlined in the
Hydrology Report (submitted separately). Basin 1 will accept drainage from watershed area A and Basin 2 will
accept drainage from subarea C1 in watershed area C (as shown on the Site Maps, attached and the Watershed
Maps in the Hydrology Report, submitted separately). Basin 1 provides a total volume of31,101 fewhile Basin
2 provides 2,542 fe.
With the increase of flow generated in Area A, the basin will need to provide 333 yd3 of detention volume. The
basin actually provides 1,152 yd3• With the increase of flow generated in Area C, the basin will need to provide
38 yd3 of detention volume. The basin actually provides 94 yd3• Area B requires no detention due to minimal
flow increase, but will have catch basin inserts provided for treatment control BMPs. The detention volumes
provided are sufficient to provide both detention and desiltation of storm flows. With the addition of catch basin
inserts will reduce pollutants of concern from reaching the basins and ultimately downstream waters. The basin
sediment storage capacities will reduce sediments from reaching downstream waters.
Flow-based BMP's shall be designed to mitigate (infiltrate, filter or treat) either:
i. The maximum flow rate runoff produced from a rainfall intensity of 0.2 inch of rainfall per hour; or
11. The maximum flow rate of runoff produced by the 85th percentile hourly rainfall intensity, as determined from the
local historical rainfall record, multiplied by a factor of two; or
iii. The maximum flow rate of runoff, as determined from the local historical rainfall record, which achieves
approximately the same reduction in pollutants loads and flows as achieved by mitigation of the 85th percentile
hourly rainfall intensity multiplied by a factor of two.
Thus, it has been shown that this project can meet the water quality objectives as outlined in Order 2001-01 with
BMPs as shown on the proposed site plan. An analysis has been performed to ensure that the site plan can
accommodate the water quality BMPs. Therefore, it is not anticipated that the site plan will be affected by the
implementation of these BMPs.
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CERTIFICATION ' ' " ",'
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CERTIFICATION
This Concept Water Quality and Stonnw~ter Management Plan has been prepared under the direction
of the undersigned to comply with the requirements of the City of Carlsbad, Standard Urban Stonn
Water Mitigation Plan, Stonn Water Standards Manual in effect as of the date ofthis report.
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I' ATTACHMENTS .' < . ~
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, APPENDICES .,
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I POST CONSTRUCTION
TREAT.MENT CONTROLBMPs
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Post-Construction Storm Water Management in New Development &
Redevelopment
Grassed Filter Strip
Description
Grassed filter strips (vegetated filter strips. filter strips. and grassed filters) are
vegetated surfaces that are designed to treat sheet flow from adjacent surfaces. Filter
strips function by slowing runoff velocities and filtering out sediment and other
pollutants. and by providing some infiltration into underlying soils. Filter strips were
originally used as an agricultural treatment practice. and have more recently evolved
into an urban practice. With proper design and maintenance. filter strips can provide
relatively high pollutant removal. One challenge associated with filter strips. however.
is that it is difficult to maintain sheet flow. so the practice may be "short circuited" by
concentrated flows. receiving little or no treatment.
Applicability
Filter strips are applicable in most regions. but are restricted in some situations
because they consume a large amount of space relative to other practices. Filter strips
are best suited to treating runoff from roads and highways. roof downspouts. very
small parking lots. and pervious surfaces. They are also ideal components of the
"outer zone" of a stream buffer (see Buffer Zones fact sheet). or as pretreatment to a
structural practice. This recommendation is consistent with. recommendations in the
agricultural setting that filter strips are most effective when combined with another
practice (Magette et al.. 1989). In fact. the most recent storm water manual for
Maryland does not consider the filter strip as a treatment practice. but does offer storm
water volume reductions in exchange for using filter strips to treat some of a site.
Regional Applicability
Filter strips can be applied in most regions of the country. In arid areas. however. the
cost of irrigating the grass on the practice will most likely outweigh its water quality
benefits.
Ultra-Urban Areas
Ultra-urban areas are densely developed urban areas in which little pervious surface
exists. Filter strips are impractical in ultra-urban areas because they consume a large
amount of space.
Storm Water Hot Spots
Storm water hot spots are areas where land use or activities generate highly
contaminated runoff. with concentrations of pollutants in excess of those typically
found in storm water. A typical example is a gas station. Filter strips should not receive
hot spot runoff. because the practice encourages infiltration. In addition. it is
questionable whether this practice can reliably remove pollutants. so it should
definitely not be used as the sole treatment of hot spot runoff.
Storm Water Retrofit
A storm water retrofit is a storm water management practice (usually structural). put
into place after development has occurred. to improve water quality. protect
downstream channels. reduce flooding. or meet other specific objectives. Filter strips
are generally a poor retrofit option because they consume a relatively large amount of
space and cannot treat large drainage areas.
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Cold Water (Trout) Streams
Some cold water species, such as trout, are sensitive to changes in temperature.
While some treatment practices, such as wet ponds (see Wet Ponds fact sheet), can
warm storm water substantially, filter strips do not warm pond water on the surface for
long periods of time and are not expected to increase storm water temperatures. Thus,
these practices are good for protection of cold-water streams.
Siting and Design Considerations
Siting Considerations
In addition to the restrictions and modifications to adapting filter strips to different
regions and land uses, designers need to ensure that this management practice is
feasible at the site in question. The following section provides basic guidelines for'
siting filter strips.
Drainage Area
Typically, filter strips are used to treat very small drainage areas. The limiting design
factor, however, is not the drainage area the practice treats but the length of flow
leading to it. As storm water runoff flows oyer the ground's surface, it changes from
sheet flow to concentrated flow. Rather than moving uniformly over the surface, the
concentrated flow forms rivulets which are slightly deeper and cover less area than the
sheet flow. When flow concentrates, it moves too rapidly to be effectively treated by a
grassed filter strip. As a rule, flow concentrates within a maximum of 75 feet for
impervious surfaces, and 150 feet for pervious surfaces (CWP, 1996). Using this rule,
a filter strip can treat one acre of impervious surface per 580-foot length.
Filter strips should be designed on slopes between 2 and 6 percent. Greater slopes
than this would encourage the formation of concentrated flow. Except in the case of
very sandy or gravelly soil, runoff would pond on the surface on slopes flatter than 2
percent, creating potential mosquito breeding habitat.
Soils {fopography
Filter strips should not be used on soils with a high clay content, because they require
some infiltration for proper treatment. Very poor soils that cannot sustain a grass cover
crop are also a limiting factor.
Ground Water
Filter strips should be separated from the ground water by between 2 and 4 ft to
prevent contamination and to ensure that the filter strip does not remain wet between
storms.
Design Considerations
Filter strips appear to be a minimal design practice because they are basically no more
than a grassed slope. However, some design features are critical to ensure that the
filter strip provides some minimum amount of water quality treatment.
• A pea gravel diaphragm should be used at the top of the slope. The pea
gravel diaphragm (a small trench running along the top of the filter strip)
serves two purposes. First, it acts as a pretreatment device, settling out
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sediment particles before they reach the practice. Second, it acts as a level
spreader, maintaining sheet flow as runoff flows over the filter strip.
• The filter strip should be designed with a pervious berm of sand and gravel at
the toe of the slope. This feature provides an area for shallow ponding at the
bottom of the filter strip. Runoff ponds behind the berm and gradually flows
through outlet pipes in the berm. The volume ponded behind the berm should
be equal to the water quality volume. The water quality volume is the amount
of runoff that will be treated for pollutant removal in the practice. Typical water
quality volumes are the runoff from a 1-inch storm or %-inch of runoff over the
entire drainage area to the practice.
• The filter strip should be at least 25 feet long to provide water quality
treatment.
• Designers should choose a grass that can withstand relatively high velocity
flows and both wet and dry periods.
• Both the top and toe of the slope should be as flat as possible to encourage
sheet flow and prevent erosion.
Regional Variations
In cold climates, filter strips provide a convenient area for snow storage and treatment.
If used for this purpose, vegetation in the filter strip should be salt-tolerant, (e.g.,
creeping bentgrass), and a maintenance schedule should include the removal of sand
built up at the bottom of the slope. In arid or semi-arid climates, designers should
specify drought-tolerant grasses (e.g., buffalo grass) to minimize irrigation
requirements.
Limitations
Filter strips have several limitations related to their performance and space
consumption:
• The practice has not been shown to achieve high pollutant removal.
• Filter strips require a large amount of space, typically equal to the impervious
area they treat, making them often infeasible in urban environments where
land prices are high.
• If improperly designed, filter strips can become a mosquito breeding ground.
• Proper design requires a great deal of finesse, and slight problems in the
design, such as improper grading, can render the practice ineffective in terms
of pollutant removal.
Maintenance Considerations
Filter strips require similar maintenance to other vegetative practices (see Grassed I
Swales fact sheet). These maintenance needs are outlined below. Maintenance is very
important for filter strips, particularly in terms of ensuring that flow does not short circuit
the practice.
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Table 1. Typical maintenance activities for grassed filter strips (Source: CWP, 1996)
Activity Schedule :.........--------_._-.--._-----------._--.. _.----;.-...... --.-~.------.. •
•
•
Inspect pea gravel diaphragm for clogging and
remove built-up sediment.
Inspect vegetation for rills and gullies and
correct. Seed or sod bare areas.
Inspect to ensure that grass has established. If
not, replace with an alternative species.
: Annual inspection (semi-
; annual the first year)
_.---_._-----------
• Mow grass to maintain a 3-4 inch height
• Remove sediment build-up within the bottom
when it has accumulated to 25% of the original
capacity.
Regular (frequent)
Regular (infrequent)
._------_ .. _.----_._----'
Effectiveness
Structural storm water management practices can be used to achieve four broad
resource protection goal~. These include flood control, channel protection, ground
water recharge, and pollutant removal. The first two goals, flood control and channel
protection, require that a storm water practice be able to reduce th€l peak flows of
relatively large storm events (at least 1-to 2-year storms for channel protection and at
least 10-to 50-year storms for flood control). Filter strips do not have the capacity to
detain these events, but can be designed with a bypass system that routes these flows
around the practice entirely.
Filter strips can provide a small amount of ground water recharge as runoff flows over
the vegetated surface and ponds at the toe of the slope. In addition, it is believed that
filter strips can provide modest pollutant removal. Studies from agricultural settings
suggest that a 15-foot-wide grass buffer can achieve a 50 percent removal rate of
nitrogen, phosphorus, and sediment, and that a 100-foot buffer can reach closer to 70
percent removal of these constituents (Desbonette et aI., 1994). It is unclear how these
results can be translated to the urban environment, however. The characteristics of the
incoming flows are radically different both in terms of pollutant concentration and the
peak flows associated with similar storm events. To date, only one study (Yu et aI.,
1992) has investigated the effectiveness of a grassed filter strip to treat runoff from a
large parking lot. The study found that the pollutant removal varied depending on the
length of flow in the filter strip. The narrower (75-foot) filter strip had moderate removal
for some pollutants and actually appeared to export lead, phosphorus, and nutrients
(See Table 2).
Table 2. Pollutant removal of an urban vegetated filter strip (Source: Yu et aI., 1993)
Total suspended solids
Nitrate+nitrite -. -,----_ ..
Total phosphorus
Extractable lead
Extractable zinc
Pollutant Removal (%)
_w _ • ___ .. _ -._.
75-Ft Filter Strip
54 _ ..
-27
-25
-16
47
. --_.-.--.~ --~. ----..
150-Ft Filter Strip
. -.. _-----.----_.--.
84
20
40
50
55
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Cost Considerations
Little data are available on the actual construction costs of filter strips. One rough
estimate can be the cost of seed or sod, which is approximately 30¢ per ff for seed or
70¢ per ft2 for sad. This amounts to between $13,000 and $30,000 per acre for a filter
strip, or the same amount per impervious acre treated. This cost is relatively high
compared with other treatment practices. However, the grassed area used as a filter
strip may have been seeded or sodded even if it were not used for treatment. In these
cases, the only additional costs are the design, which is minimal, and the installation of
a berm and gravel diaphragm. Typical maintenance costs are about $350lacre/year
(adapted from SWRPC, 1991). This cost is relatively inexpensive and, again, might
overlap with regular landscape maintenance costs.
The true cost of filter strips is the land they consume, which is higher than for any other
treatment practice. In some situations this land is available as wasted space beyond
back yards or adjacent to roadsides, but this practice is cost-prohibitive when land
prices are high and land could be used for other purposes.
References
Design Reference
Center for Watershed Protection (CWP). 1996. Design of Stormwater Filtering
Systems. Prepared for Chesapeake Research Consortium, Solomons, MD, and EPA
Region V, Chicago, IL.
Other References
Desbonette, A., P. Pogue, V. Lee, and N. Wolff. 1994. Vegetated Buffers in the
Coastal Zone: A Summary Review and Bibliography. Coastal Resources Center.
University of Rhode Island, Kingston, RI.
Magette, W., R. Brinsfield, R. Palmer and J. Wood. 1989. Nutrient and Sediment
Removal by Vegetated Filter Strips. Transactions of the American Society of
Agricultural Engineers 32(2): 663-667.
Southeastern Wisconsin Regional Planning Commission (SWRPC). 1991. Costs of
Urban Nonpoint Source Water Pollution Control Measures. Technical report no. 31.
Southeastern Wisconsin Regional Planning Commission, Waukesha, WI.
Yu, S., S. Barnes and V. Gerde. 1993. Testing of Best Management Practices for
Controlling Highway Runoff. FHWNVA 93-R16. Virginia Transportation Research
Council, Charlottesville, VA.
Information Resources
Center for Watershed Protection (CWP). 1997. Stormwater 8MP Design Supplement
for Cold Climates. Prepared for U.S. Environmental Protection Agency Office of
Wetlands, Oceans and Watersheds. Washington, DC.
Maryland Department of the Environment (MOE). 2000. Maryland Stormwater Design
Manual. (http://www.mde.state.md.us/environmentlwma/stormwatermanual
I' '\II'<I ...... i .. ".r>I]. Accessed May 22,2001.
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Sediment Basin
Description and Purpose
A sediment basin is a temporary basin formed by excavation or
by constructing an embankment so that sediment-laden runoff
is temporarily detained under quiescent conditions, allowing
sediment to settle out before the runoff is discharged.
Suitable Applications
Sediment basins may be suitable for use on larger projects with
sufficient space for constructing the basin. Sediment basins
should be considered for use:
• Where sediment-laden water may enter the drainage system
or watercourses
• On construction projects ,vith disturbed areas during the
rainy season
• At the outlet of disturbed watersheds between 5 acres and
75 acres
• At the outlet oflarge disturbed watersheds, as necessary
• Where post construction detention basins are required
• In association with dikes, temporary channels, and pipes
used to convey runoff from disturbed areas
Limitations
Sediment basins must be installed only within the property limits
and where failure of the structure will not result in loss of life,
damage to homes or buildings, or interruption of use or service of
January 2003 California Stormwater BMP Handbook
Construction
www.cabmphandbooks.com
SE-2
Objectives
EC Erosion Control
SE Sediment Control
. TC Tracking Control
WE Wind Erosion Control
NS Non-Stormwater
Management Control
Waste Management and
WM Materials Pollution Control
Legend:
./ Primary Objective
./ Secondary Objective
Targeted Constituents
Sediment ./
Nutrients
Trash . ./
Metals
Bacteria
Oil and Grease
Organics
Potential Alternatives
SE-3 Sediment Trap (for smaller
areas)
Stormwater
Quality
Association
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SE-2 Sediment Basin
public roads or utilities. In addition, sediment basins are attractive to children and can be very
dangerous. Local ordinances regarding health and safety must be adhered to. Iffencing of the
basin is required, the type of fence and its location should be shown in the SWPPP and in the
construction specifications.
• Generally, sediment basins are limited to drainage areas of 5 acres or more, but not
appropriate for drainage areas greater than 75 acres.
• Sediment basins may become an "attractive nuisance" and care must be taken to adhere to
all safety practices. If safety is a concern, basin may require protective fencing.
• Sediment basins designed according to this handbook are only practically effective in
removing sediment down to about the medium silt size fraction. Sediment-laden runoff with
smaller size fractions (fine silt and clay) may not be adequately treated unless chemical
treatment is used in addition to the sediment basin.
• Sites with very fine sediments (fine silt and clay) may require longer detention times for
effective sediment removal.
• Basins with a height of 25 ft or more or an impounding capacity of 50 ac-ft or more must
obtain approval from Division of Safety of Dams.
• Standing water may cause mosquitoes or other pests to breed.
• Basins req uire large surface areas to permit settling of sediment. Size may be limited by the
available area.
Implementation
General
A sediment basin is a controlled storm water release structure formed by excavation or by
construction of an embankment of compacted soil across a drainage way, or other suitable
location. It is intended to trap sediment before it leaves the construction site. The basin is a
temporary measure with a design life of 12 to 28 months in most cases and is to be maintained
until the site area is permanently protected against erosion or a permanent detention basin is
constructed.
Sediment basins are suitable for nearly all types of construction projects. Whenever possible,
construq the sediment basins before clearing and grading work begins. Basins'should be
located at the stormwater outlet from the site but not in any natural or undisturbed stream. A
typical application would include temporary dikes, pipes, and/or channels to divert runoff to the
basin inlet.
Many development projects in California will be required by local ordinances to provide a
stormwater detention basin for post-construction flood control, desilting, or stormwater
pollution control. A temporary sediment basin may be constructed by rough grading the post-
construction control basins early in the proj~ct.
Sediment basins trap 70-80 % of the sediment that flows into them if designed according to this
handbook. Therefore, they should be used in conjunction with erosion control practices such as
2 of 12 California Stormwater BMP Handbook
Construction
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January 2003
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Sediment Basin SE-2
temporary seeding, mulching, diversion dikes, etc., to reduce the amount of sediment flowing
into the basin.
Planning
To improve the effectiveness of the basin, it should be located to intercept runoff from the
largest possible amount of disturbed area. The best locations are generally low areas. Drainage
into the basin can be improved by the use of earth dikes and drainage swales (see BMP EC-9).
The basin must not be located in a stream but it should be located to trap sediment-laden runoff
before it enters the stream. The basin should not be located where its failure would result in the
loss of life or interruption of the use or service of public utilities or roads.
• Construct before clearing and grading work begins when feasible.
• Do not locate in a stream.
• Basin sites should be located where failure of the structure will not cause loss oflife, damage
to homes or buildings, or interruption of use or service of public roads or utilities.
• Large basins are subject to state and local dam safety requirements.
• Limit the contributing area to the sediment basin to only the runoff from the disturbed soil
areas. Use temporary concentrated flow conveyance controls to divert runoff from
undisturbed areas away from the sediment basin.
• The basin should be located: (1) by excavating a suitable area or where a low embankment
can be constructed across a swale, (2) where post-construction (permanent) detention
basins will be constructed, and (3) where the basins can be maintained on a year-round basis
to provide access for maintenance, including sediment removal and sediment stockpiling in
a protected area, and to maintain the basin to provide the required capacity.
Design
Sediment basins must be designed in accordance with Section A of the State of California
NPDES General Permit for Stormwater Discharges Associated with Construction Activities
(General Permit) where sediment basins are the only oontrol measure proposed for the site. If
there is insufficient area to construct a sediment basin in accordance with the General Permit
requirements, then the alternate design standards specified herein may be used.
Sediment basins designeci per the General Permit shall be designed as f011ows:
Option 1:
Pursuant to local ordinance for sediment basin design and maintenance, provided that the
design efficiency is as protective or more protective of water quality than Option 3.
OR
Option 2:
Sediment basin(s), as measured from the bottom ofthe basin to the principal outlet, shall have
at least a capacity equivalent to 3,600 cubic feet (133 yd3) of storage per acre draining into the
sediment basin. The length of the basin shall be more than twice the width of the basin. The
January 2003 California Stormwater BMP Handbook
Construction
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SE-2 Sediment Basin
length is determined by measuring the distance between the inlet and the outlet; and the depth
must not be less than 3 ft nor greater than 5 ft for safety reasons and for maximum efficiency.
OR
Option 3:
Sediment basin(s) shall be designed using the standard equation:
OR
AS=1.2Q/VS (Eq. 1)
Where:
As = Minim urn surface area for trapping soil particles of a certain size
Vs = Settling velocity of the design particle size chosen
Q=CIA
Where
Q = Discharge rate measured in cubic feet per second
C = Runoff coefficient
I = Precipitation intensity for the lO-year, 6-hour rain event
A = Area draining into the sediment basin in acres
The design particle size shall be the smallest soil grain size determined by wet sieve
analysis, or the fine silt sized (0.01 mm [or 0.0004 in.]) particle, and the Vs used shall be
100 percent of the calculated settling velocity.
The length is determined by measuring the distance between the inlet and the outlet; the
length shall be more than twice the dimension as the width; the depth shall not be less
than 3 ft nor greater than 5 ft for safety reasons and for maximum efficiency (2 ft of
sediment storage, 2 ft of capacity). The basin(s) shall be located on the site where it can
be maintained on a year-round basis and shall be maintained on a schedule to retain the
2 ft of capacity.
Option 4:
The use of an equivalent surface area design or equation, provided that the design efficiency is
as protective or more protective of water quality than Option 3.
4 of 12 California Stormwater BMP Handbook
Construction
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Sediment Basin SE-2
Other design considerations are:
• The volume of the settling zone should be sized to capture runoff from a 2-year stonn or
other appropriate design storms specified by the local agency. A detention time of 24 to 40
hours should allow 70 to 80 % of sediment to settle.
• The basin vol ume consists of two zones:
A sediment storage zone at least 1 ft deep.
A settling zone at least 2 ft deep.
• The length to settling depth ratio (LjSD) should be less than 200.
• Sediment basins are best used in conjunction with erosion controls. Sediment basins that
will be used as the only means of treatment, without upstream erosion and sediment
controls, must be designed according to the four options required by the General Permit (see
Options 1-4 above). Sediment basins that are used in conjunction with upstream erosion
and sediment controls should be designed to have a capacity equivalent to 67 yd3 of
sediment storage per acre of contributory area.
• The length of the basin should be more than twice the ·width of the basin; the length should
be detennined by measuring the distance between the inlet and the outlet.
• The depth must be no less than 3 ft.
• Basins with an impounding levee greater than 4.5 ft tall, measured from the lowest point to
the impounding area to the highest point of the levee, and basins capable of impounding
more than 35,000 ft3, should be designed by a Registered Civil Engineer. The design should
include maintenance requirements, including sediment and vegetation removal, to ensure
continuous function of the basin outlet and bypass structures.
• Basins should be designed to drain within 72 hours following storm events. If a basin fails to
drain within 72 hours, it must be pumped dry.
• Sediment basins, regardless of size and storage volume, should include features to
accommodate overflow or bypass flows that exceed the design storm event.
I nclude an emergency spillway to accommodate flows not carried1by the principal
spillway. The spillway should consist of an open channel (earthen or vegetated) over
undisturbed material (not fill) or constructed of a non-erodible riprap.
The spillway control section, which is a level portion of the spillway channel atthe
highest elevation in the channel, should be a minimum of 20 ft in length.
• Rock or vegetation should be used to protect the basin inlet and slopes against erosion.
• A forebay, constructed upstream of the basin may be provided to remove debris and larger
particles.
January 2003 California Stormwater BMP Handbook
Construction
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• The outflow from the sediment basin should be provided with velocity dissipation devices
(see BMP EC-10) to prevent erosion and scouring ofthe embankment and channel.
• Basin inlets should be located to maximize travel distance to the basin outlet.
• The principal outlet should consist of a corrugated metal, high density polyethylene (HDPE),
or reinforced concrete riser pipe with dewatering holes and an anti-vortex device and trash
rack attached to the top of the riser, to prevent floating debris from flowing out of the basin
or obstructing the system. This principal structure should be designed to accommodate the
inflow design stOITI1.
• A rock pile or rock-filled gabions can serve as alternatives to the debris screen, although the
designer should be aware of the potential for extra maintenance involved should the pore
spaces in the rock pile clog.
• The outlet structure should be placed on a fiITI1, smooth foundation with the base securely
anchored with concrete or other means to prevent floatation.
• Attach riser pipe (watertight connection) to a horizontal pipe (barrel). Provide anti-seep
collars on the barrel.
• Cleanout level should be clearly marked on the riser pipe.
• Proper hydra ulic design of the outlet is critical to achieving the desired perfoITI1ance of the
basin. The outlet should be designed to drain the basin within 24 to 72 hours (also referred
to as "drawdO\Vll time"). The 24-hour limit is specified to provide adequate. settling time; the
72-hour limit is specified to mitigate vector control concerns.
.• The two most common outlet problems that occur are: (1) the capacity of the outlet is too
great resulting in only partial filling of the basin and drawdown time less than designed for;
and (2) the outlet clogs because it is not adequately protected against trash and debris. To
avoid these problems, the following outlet types are recommended for use: (1) a single orifice
outlet with or without the protection of a riser pipe, and (2) perforated riser. Design
guidance for single orifice and perforated riser outlets follow:
6 of 12
Flow Control Using a Single Orifice At The Bottom Of The Basin (Figure 1): The outlet
control orifice should be sized using the following equation:
2A(H -HO)O.5 (7xlO-5 )A(H -HO)O.5 a---=------'-'-------''---3600CT(2g)0.5 -CT
where:
a = area of orifice (ft2)
A = surface area of the basin at mid elevation (ft2)
C = orifice coefficient
T = drawdown time of full basin (hrs)
California Stormwater 8MP Handbook
Construction
www.cabmphandbooks.com
(Eq.2)
January 2003
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Sediment Basin SE-2
g = gravity (32.2 ft/S2)
H = elevation when the basin is full (ft)
Ho = final elevation when basin is empty (ft)
With a drawdown time of 40 hours, the equation becomes:
(1.75xlO-6 )A(H -Ho)O.5 a = -'------.:..~---:....-
C
Flow Control Using Multiple Orifices (see Figure2):
2A(hmax ) a =------~~----
t CT(2g[hmax -hcenUOidO!Or!fices])O.5
With terms as described above except:
at = total area of orifices
(Eq.3)
(Eq·4)
hma"( = maximum height from lowest orifice to the maximum watet surface (ft)
hcentroid of orifices = height from the lowest orifice to the centroid of the orifice configuration
(ft)
Allocate the orifices evenly on two rows; separate the holes by 3X hole diameter
vertically, and by 120 degrees horizontally (refer to Figure 2).
Because basins are not maintained for infiltration, water loss by infiltration should be
disregarded when designing the hydraulic capacity of the outlet structure.
Care must be taken in the selection of "C"; 0.60 is most often recommended and used.
However, based on actual tests, GKY (1989), "Outlet Hydraulics of Extended Detention
Facilities for Northern Virginia Planning District Commission", recommends the
following:
C = 0.66 for thin materials; where the thickness is equal to or less than the orifice
diameter, or f I
C = 0.80 when the material is thicker than the orifice diameter
Installation
• Securely anchor and install an anti-seep collar on the outlet pipe/riser and provide an
emergency spillway for passing major floods (see local flood control agency).
• Areas under embankments must be cleared and stripped of vegetation.
• Chain link fencing should be provided around each sediment basin to prevent unauthorized
entry to the basin or if safety is a concern.
January 2003 California Stormwater BMP Handbook
Construction
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SE-2 Sediment Basin
Costs
Average annual costs for installation and maintenance (2 year useful life) are:
• Basin less than 50,000 ft3: Range, $0.24 -$1.58/ft3. Average, $0.73 per ft3. $400 -$2,400,
$1,200 average per drainage acre.
• Basin size greater than 50,000 ft3: Range, $0.12 -$0.48/ft3. Average, $0.36 per ft3. $200-
$800, $600 average per drainage acre.
In~pection and Maintenance
• Inspect BMPs prior to forecast rain, daily during extended rain events, after rain events,
weekly during the rainy season, and at two-week intervals during the non-rainy season.
• Examine basin banks for seepage and structural s~undness.
• Check inlet and outlet structures and spillway for any damage or obstructions. Repair
damage and remove obstructions as needed. .
• Check inlet and outlet area for erosion and stabilize if required.
• Check fencing for damage and repair as needed.
• Sediment that accumulates in the BMP must be periodically removed in order to maintain
BMP effectiveness. Sediment should be removed when sediment accumulation reaches one-
half the designated sediment storage volume. Sediment removed during maintenance may
be incorporated into earthwork on the site or disposed of at appropriate locations.
• Remove standing water from basin within 72 hours after accumulation.
• BMPs that require dewatering shall be continuously attended while dewatering takes place.
Dewatering BMPs shall be implemented at all times during dewatering activities.
• To minimize vector production:
Remove accumulation of live and dead floating vegetation in basins during every
inspection. .
Remove excessive emergent and perimeter vegetation as needed or as advised by local or
state vector control agencies.
References
A Current Assessment of Urban Best Management Practices: Techniques for Reducing
Nonpoint Source Pollution in the Coastal Zones, Metropolitan Washington Council of
Governments, March 1992.
Draft-Sedimentation and Erosion Control, an Inventory of Current Practices, USEP A. April
1990.
Guidelines for the Design and Construction of Small Embankment Dams, Division of Safety of
Dams, California Department of Water Resources, March 1986.
8 of 12 California Stormwater BMP Handbook
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Manual of Standards of Erosion and Sediment Control Measures, Association of Bay Area
Governments, May 1995.
McLean, J., 2000. Mosquitoes in Constructed Wetlands: A Management Bugaboo? In T.R.
Schueler and H.K. Holland [eds.], The Practice of Watershed Protection. pp. 29-33. Center for
Watershed Protection, Ellicott City, MD, 2000.
Metzger, M.E., D. F. Messer, C. L. Beitia, C. M. Myers, and V. L. Kramer. The dark site of
stormwater runoff management: disease vectors associated with structural BMPs, 2002.
National Management Measures to Control Nonpoint Source Pollution from Urban Areas,
United States Environmental Protection Agency, 2002.
Proposed Guidance Specifying Management Measures for Sources of Nonpoint Pollution in
Coastal Water, Work Group-Working Paper, USEPA, April 1992.
Stormwater Quality Handbooks -Construction Site Best Management Practices (BMPs) Manual,
State of California Department of Transportation (Caltrans), November 2000.
Stormwater Management ofthe Puget Sound Basin, Technical Manual, Publication #91-75,
Washington State Department of Ecology, February 1992.
U.S. Environmental Protection Agency (USEPA). Guidance Specifying Management Measures
for Nonpoint Pollution in Coastal Waters. EPA 840-B-9-002. U.S. Environmental Protection
Agency, Office of Water, Washington, DC, 1993
Water Quality Management Plan for the Lake Tahoe Region, Volume II Handbook of
Management Practices, Tahoe Regional Planning Agency, November 1988.
January 2003 California Stormwater BMP Handbook
Construction
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SE-2 Sediment Basin
Embankment
Stabilized
-----
---.... " Side slopes ~l 3: 1 (H: V) .
Max I
------------.-----inlet { I
/ Riser
protection
, '-------... , ....
'-.
--------
TOP VIEW
12 in
Riser
Design high water
12 in
Min Dewatering outlet
Sediment storage
depth permanent pool
NOTE: SIDE VIEW
This outlet provides no drainage
for permanent pool.
FIGURE 1: TYPICAL TEMPORARY SEDIMENT BASIN
SINGLE ORIFICE DESIGN
10 of 12
NOT TO SCALE
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Construction
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January 2003
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Embankment
---------... .... "\ Side slopes ~3: 1 (H: V) ./
-------
I Max I .
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inlet {~===7
, '------.... ..... '-
---------
TOP VIEW
Riser wi hood
& trash rock
~ _______ Sl __________ _
Settling depth~--
24" Min depth
Sedim en t storage --"-<:--
Emergency
spillway
~12" :;-r
depth -12" Min '------i/.,:===u====ll
Riser encased in gravel
jacket. Upper two-thirds
perforated.
Anti-seep
collars
Anti-floatation block
SIDE VIEW
protection
FIGURE 2: TYPICAL TEMPORARY SEDIMENT BASIN
MULTIPLE ORIFICE DESIGN
January 2003
NOT TO SCALE
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Maintenance &-------
emergency discharge
outlet
Debris screen
Trash rack
Debris screen
Water quality
discharge orifices
Maintenance &
emergency discharge
outlet
Sediment Basin
Ou t flow
Plan
Profile
Outflow
\,~: .. ~ a .... _~ j.# ....
. : .• -:"'''!'" .. -... :. t ••
FIGURE 3: MULTIPLE ·ORIFICE OUTLET RISER
NOT TO SCALE
12 of 12 California Stormwater BMP Handbook
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POST CONSTRUCTION
PROPRIETARY BMPs
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US PATENT
Flo-Gard+Plus Filter
installed
NOTES:
1. Ac>GardThliPWS (wan roount) high capacity catch basin
inserts a-e avalabie in sizes to fit combination style and
non-standard each basins (see specifier chart). Refer to
the Ac>GardThliPLUS (frame mount) insert for devices to lit
most f1atijrated standard style catch basins.
2. Filter insert shall have both an "initial" filtering bypass and
"uitillBte" high.flow bypass feature.
3. Filter asserrbly shall be constructed from stainless steel
(Type 304).
4. Allow a rrinimum of '/.j)" of c1earmce between the bottom
of grate and top ci inlet or outlet pipe(s). Refer to the
Ac>GardThl insert for "shallow" installations.
5. Filter medium shall be Rubberizem Installed and maintained
in accordance with mallllfachKer recommendations.
~/"-..")
... /'
Mounting Brackets
FLO-GARO™ +PLUS
CATCH BASIN FILTER INSERT
(Wall Mount Installation)
COMBINATION INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
06/04
h-,---i------------r-ri ~I---OebrisTrap
_f-
~~ ---/ .'.:.:.:.:. :',':' .. ; ':':':':':'. ':':':'. ':', .:.: ..
!-
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r--r--....... -Ultimate" Bypass
Liner
! ...
~
.......... Support Basket
................................................................... .
vi '"
Catch Basin u----i--------------'-' --(Ral Grate Style)
'------'---LI====::F=======~ Outlet Pipe
TOP VIEW
-++-___ Grate
Gasket
Ultimate Bypass
Debris Trap
Support Basket
Absorbent Pouches
Liner
.-1-----1--,-Outtet Pipe
SIDE VIEW
NOTES:
1. Flo-Gard™+PlUS (wall mount) high capacity catch basin
inserts are available to fit non standard or combination
catch basin sizes and styles (see specifier chart). Refer to
the Flo-Gard™+PLUS (frame mount) inserffor devices to fit
industry standard-size flat grated catch basin inlets.
2. Filter insert shall have both an "initial" filteriJig bypass and
.. ultimate" high·flow bypass feature.
3. Filter assembly shall be constructed from stainless steel
(Type 304).
4. Allow a minimum of Z-O" of clearance between the bottom
of grate and top of inlet or outlet pipe(s). Refer to the
Flo-Gard™ insert for "shallow" installations.
5. Filter medium shall be Rubberizer® installed and maintained
in accordance with manufacturer recommendations.
FLO-GARO™ +PLUS
CATCH BASIN FILTER INSERT
(Wall Mount)
COMBINATION INLET
KriSlar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
06/04
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us PATENT
CATCH
BASIN
FILTER BODY
FILTER BASKET
FOSSIL ROCR' FILTER
MEDIUM POUCH
PIPE INLET
....... '3/8" X3"
ANCHOR BOLT
(3 PER SECTION)
PIPE INLET-SIDE VIEW
SCALE: NONE
FLO-GARO™ +PLUS
I
CATCH BASIN FILTER INSERT
(Curb Mount-Installation Options)
PIPE INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
06/04
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US PATENT
FLOATING EDGE
(CURVED UPWARD)
.OPTIONAL RECESSED MOUNT
SCALE: NONE
EXAMPLE: SAN DIEGO REGIONAL STANDARD
CURB INLET TYPE "S"
FLO-GARD +PLUS
(REMOVABLE)
WATERTIGHT SEAL
FLO-GARD™ +PLUS
CATCH BASIN FILTER INSERT
(Curb Mount-Installation Options)
CURB INLET· RECESSED MOUNT
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819 06104
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US PATENT
CURB INLET-SIDE VIEW
SCALE: NONE
FILTER BODY
FILTER BASKET
FOSSIL ROC~ FILTER
MEDIUM POUCH .. ' . . ~ ... "
CURB OPENING
3/8" X3"
ANCHOR BOLT
(3 PER SECTION)
FLO-GARO™ +PLUS
CATCH BASIN FILTER INSERT
(Curb Mount-Installation Options)
CURB INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
06/04
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,
Attach to catch basin wall or
~I __ ~
v
TOP VIEW
Initial (filtering)
Support Basket
FRONT VIEW
____ Catch Basin Wall
Stainless Steel
Debris Trap
o
(optional)
•
FilterLiner
Support Basket
SIDE VIEW
Debris Trap
/
I·
Gasket
o
Uner
NOTES:
1. A<Klard™+PLUS (curb 11ll00t) Iigh caj:aCily catch basin
inserts are available in sizes to fit most industry-standard
catch basin sizes ald styles (see specifier chart). Refer to
the A<Klard™+PLUS (wall l1llunt) insert fot devices to fit
non-standard or coniJination style catch basins.
2. Filter insert shall have both al "iritial" fittering bypass and
"ultirmle" high-How bypass feature.
3. Filter asseniJly shan be constructed from stainless steel
(Type 304). I
4. Allow a rtinil11ll1l of '/.0" of cle<ralce between the bottom
of grate and top of inlet or outletpipe(s). Refer to the
Flo-Gard™ insert for "shaHow" instaHations.
5. Filter medium shall be RttberiZlll'® installed and maintained
in accordance with rmnufacturer recomnendalioos.
FLO-GARD TM +PLUS
CATCH BASIN FILTER INSERT
(Curb Mount)
CURB INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
1
12"
1
06104
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US PATENT
Flo-Gard+Plus Fitter
installed
NOTES:
-
1. Flo-GardlMtPLUS (frame mount) high capacity catch basin
Inserts are available in sizes to fit most industry-standard
catch basin sizes a1d stytes (see specifier chat). Refer to
the Flo-GardlM+PLUS (wall mount) insert for devices to fit
non-standard or combination style catch basins.
2. Filter insert shall have both an "initial" filtering bypass and
"ultimate" high-flow bypass feature.
3. Filter asseniJIy shaD be constructed from stainless steel
(Type 304).
4. Allow a ninimum of 'l.q' of clearance between the bottom
of grate and top of inlet or outlet pipets). Refer to the
Flo-GardlM insert for "shallow" installatioos.
5. Filter medium shall be Rubberizei'll installed and maintained
in accordance with manufacturer recomnendations.
/~"')
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FLO-GARO™ +PLUS
CATCH BASIN FILTER INSERT
(Frame Mount Installation)
FLAT GRATED INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
06/04
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1'-.....1'-~Ultimale" Bypass
Uner
.............................................................. '-.....
--......... Support Baskel
CalchBasin
'-'-______________ ....L.I --(Ral Grale Slyle)
1-------l/====3F======~ Outlet Pipe
TOP VIEW
Initial Bypass
r-,----------7.L.-==F===J--Grale NOTES:
T
1
US PATENT
Gaskel
Ultimale Bypass
Debris Trap
Support Baskel
Fossil Rock Pouches
Uner
1. Ao-Gard™+PlUS (frame 11lOII1I) high capacity catch basin
inserts are available In sizes to fit most iodustry-stoodard
catch basin sizes CIld ~es (see specifier chart). Refer to
the Ao-Gard™tPLUS (wall mount) insert f« devices to fit
non-sIiIldard or rontination style each basins.
2. Rlter insert shall have both an "initial" filtering bypass ald
"ultimate" high-noW bypass feature.
3. Rlter asserriJly shall be constructed from stainless steel
[Type 304).
4. Allow a ninllOOm of 2'.0" of clearance between the bottom
of grate and top of inlet or outlet pipe{s). Refer to the
. Ao-Gard™ insert for "shallow" installations.
5. Filter medium shan be Rubberizerw InstaRed and maintained
in accordance v.ith manufacturer recorrrnendations.
L-_---i--r-Outlel Pipe
SIDE VIEW
FLO-GARDtM +PLUS
CATCH BASIN FILTER INSERT
(Frame Mount)
FLAT GRATED INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
06/04
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Flo INTO COMPLIANCE.
FloGard™ complies with state and federal
requirements for pollution protection of drains
from storm water runoff in a variety of installations.
FloGard™ captures silt and debris, as well as oils
and grease from runoff before it enters our streams
and oceans. FloGard™ is suitable for use in such
applications as vehicle parking lots, aircraft ramps,
truck/bus storage yards, corporate yards,
subdivisions and public streets. CONTRACTORS
can use FloGard™ during construction to handle
sediment problems.
EASY, ECONOMICAL SOLUTION.
The FloGard™ design allows for installation in
either new or existing drain inlets. Industry-standard
sizes and shapes are available for flat-grated,
combination, curb and round inlet applications.
FloGard™ is easy and economical to install.
FloGard™ uses the same effective filter medium
(Fossil Rock™) found in our other Fossil FilterTM products.
This medium is in pre-filled adsorbent pouches that
are easily replaced. Additiona"y, the filter body is
replaceable should damage occur during usage.
MAINTENANCE PROGRAMS.
Product discounts are available with
the purchase of a comprehensive
maintenance package.
FloGard™ -Another economical
pollution solution from the
makers of Fossil FilterTM!
Circular drain
in.lolioHon
u.s. PATENT PENDING
Eosily replaceable
prelilled Fossil Rock'M
pouches oller efleelive
removel 01 oil and
grease.
Modular de.ign allow"
lor ea.y replaeemenl
olliller componenl •.
r il.
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"Clip In" FOSSIL
ROCK'· Booms
(hydrocarbon removal
during highest flows) ,
\\
Stainless steel
support frame
(easy Inslallalion
without anchoring
to calch basin) , ',,-
""
Liner support basket
(durable supporllor
ma<imum weight of
collected pollutants)
High tensile corner
support cables
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(added load support Ihat
retains liner size and .....
shape when full) ' ......
PATENT PENDING
The unique /lpatent pending/l design of the FloGard™
High Capacity catch basin insert offers a removable
"trap" that retains floatables during high flows.
The solids holding capacity of the FloGard™ High
Capacity insert will vary by model. For example, the
24/1x 24/1x12/l model will hold approximately 1.67
cubic feet of debris, while a 36/1x36"x36/1 model will
hold up to 13.43 cubic feet.
Removable debris trap
(retains floatables during
high flows)
FOSSIL ROCKN
pillow (hydrocarbon
removal during low lIows)
High Ilow bypass
(will not impede
maximum design lIows)
Replaceable filter liner
(effectively collects
sediment, debris and
trash)
'Refer 10 specification
chart lor available sizss.
FloGard™ High Capacity is recommended for
areas with higher than normal amounts of sediment
and debris and moderately high levels of petroleum
hydrocarbons. Examples of appropriate applications
are public streets, equipment storage and/or
maintenance yards and industrial facilities.
For areas where petroleum hydrocarbons (oil and
grease) are a concern, the FloGard™ High Capacity
catch basin insert may be specified with Fossil Rock'·
filter medium in easy to replace "clip in" pouches.
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FILTRATION CAPACITY
Charts shown below reflect the effectively filtered hydraulic flow capacity of both rectangular grated inlets and
curb inlets of various sizes.
The data shown on the charts is based on the hydraulic testing performed by Sandine & Associates (see
attached letters). Testing ~ shown that a flow rate of 12 GPM per linear foot of Fossil Fdte,mt is effectively
:filtered by the installed Fossil RocJclm filter media.
HYDRAULIC CAPACITY CHART
Rectangular Grated Inlet Application
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20 ........................... '1" ................................ r .... · ........ · .. · ............... t .... · ........................... t .... · ........................... 1" .................................. , .................................. r ............ ..
o 24 "x24" 24"x30" 24"x36" 30"x30" 24"x48" 36"x36" 36"x48" 48"x48"
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INLET DIMENSION
HYDRAULIC CAPACITY CDART
Curb Inlet Application
250 .... ·· .. · .. · ...... ····r··· .. ·· .............. ·r ........ ·· ...... ··· .. ·T·· ...... ······· .. ·· .. ·T· .. · .. ···· ...... ·· .... r .. ·· .. · ........ ·· .... ·r·· .... · .. ·· .... ······T······ .......... · .. ·· .. ,
o·~----+-----~----~----~----~----~----~----~ o 36" 48" 60" 72" 84" 96" 108" 120"
o KriStar Enterprises 419196 CURB INLET ~~
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K&S ENGINEERING
Planning Engineering Surve~ng
L--DETENTIONjDESIL
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PROJECT INFORMATION SITE MAP
LEGEND
DRAINAGE STRUCTURE FLOW
SURFACE FLOW
DRAINAGE AREA
CONCRETE BROW DITCH
HMP LINE
ENVIRONMENTALLY SENSITIVE AREA
NON-DISTRUBED AREA
> ....... --
CALTRANS
B.M.P. CODE
STABILIZED CONSTRUCTION ENTRANCE TC-1,3
SILT FENCE SC-1
GRAVEL BAG BARRIER
MATERIAL DELIVERY AND STORAGE/
SOLID WASTE MANAGEMENT
DETENTION/DESILT BASIN
SC-4,6,B,9,10
WM-1,5,6,B,9
SC-2, SE-2
SYMBOL
-D 01------
cc"C:c.::C'::,:·:O:":·
, . ff~32fJ.7
_ PAj)=J20.15
NOTE:
IN THE EVENT THAT THE CLEARED SITE REMAINS EMPTY FOR A PERIOD -';'~c;:"~"'~~. OF MORE THAN THIRTY DAYS, THE AREA SHALL BE HYDROSEEDED.
THE HYDROSEED MIX SPEaRED IS A NAlIVE MIX AND WILL REQUIRE NO
IRRIGAlION AFTER IT HAS BEEN ESTABLISHED. IRRIGAlION TO ESTABLISH
SEED MIX WILL BE BY WATER TRUCK. HYDROSEED MIX:
ARTEMESIA CALIFORNIA (CAliFORNIA SAGEBRUSH) 4 LBS/ACRE
4 LBS/ACRE
2 LBS/ACRE
8 LBS/ACRE
20 LBS/ACRE
5 LBS/ACRE
4 LBS/ACRE
4 LBS/ACRE
BACCHARIS EMERI (COYOTE BRUSH)
. BACCHARIS SAROTHROIDES (DESERT BROOM) .
ENCEUS CALIFORNIA (CAUFORNIA SUNflOWER)
ERIOGONUM F ASCICULA TUM (CALIFORNIA BUCKWHEAT)
HETEROMELES ARBUllFOUA (TOYON)
RHUS LAURINA (LAUREL SUMAC)
SAlVIA MEUFERA (BLACK SAGE)
1. SOIL PREPARAllON:
A. WATER AUL PLANlING AREAS THOROUGHLY AND CONlINUOUSL Y
FOR THREE (3) CONSECUlIVE DAYS TO SA TURA TE UPPER
LAYER OF SOIL PRIOR TO HYDROSEEDING OPERA liON.
B. ALLOW PLANlING AREA SOIL SURFACE TO DRY OUT FOR ONE
DAY ONLY PRIOR TO THE HYDROSEEDING APPLICAlION. CARE
MUST BE TAKEN TO NOT ALLOW THE SOIL SURFACE TO BE
SUPER SA TURA TED WITH WATER PRIOR TO THE HYDROSEEDING
INSTAULAlION. AT lIHE SAME liME THE SOIL SURFACE SHOULD
NOT BE BONE DRY. THERE SHOULD BE SOME RESIDUAL
MOISTURE WITHIN lIHE RRST 1/4 INCH OF SOIL SURFACE.
C. BEGIN THE HYDROSEEDING OPERA liON ON AUL AREAS AS
SPEaRED HEREIN.
2. PREP ARA llON OF HYDROSEEDING MIXTURE:
3.
.;/ .4.
A. THE SLURRY SHALL BE PREPARED AT THE SITE AND ITS
COMPONENTS SHALL BE MIXED TO SUPPLY THE RATES OF
APPLICA liON AS PER SPECIRCA liONS.
B. SLURRY PREPARAlION SHALL BEGIN BY ADDING WATER TO
THE LINK WHEN lIHE ENGINE IS AT ONE-HALF THROTTLE.
WHEN THE WATER LEVEL HAS REACHED THE HEIGHT OF THE
AGITATOR SHAFT AND GOOD RECIRCULAllON HAS BEEN
ESTABLISHED, THE FERlIUZER SHALL BE ADDED TO THE
MIXTURE (THE TANK SHALL BE AT LEAST 1/3 RLED WITH
WATER AT lIHlS liME) •
. C. THE ENGINE lIHROTTLE SHAlL BE OPEN TO FULL SPEED
WHEN THE TANK IS 1/2 RLLED WITH WATER. AUL ORGANIC.
AMENDMENTS, RBER, AND CHEMICALS SHALL THEN BE
ADDED BY lIHE liME THE TANK IS 2-1/3 TO 3/4 FUUL.
AT THIS liME THE SEED MIX SHALL ALSO BE ADDED.
D. SPRA YlNG SHALL COMMENCE IMMEDIA TEL Y WHEN THE TANK
\S FULL AID lIHE SLURRY IS MIXED.
APPUCA liON: TH, OPERATOR SHALL SPRAY THE AREA WITH A
UNIFORM VISIBLE COAT USING lIHE DARK COLOR OF THE
CELLULOSE RBER OR ORGANIC AMENDMENT AS VISUAl GUIDE. THE
SLURRY SHAUL BE APPLIED IN A DOWNWARD DRIULING MOllON
. VIA A FAN STREAM NOZZLE.
llME UMIT: THE HYDROMULCHING SLURRY COMPONENTS ARE NOT
TO BE LEFT IN lIHE HYDROMULCHING MACHINE FOR MORE THAN
TWO HOURS. IF SLURRY COMPONENTS ARE LEFT FOR MORE THAN
TWO HOURS IN lIHE MACHINE, THE CONTRACTOR SHALL ADD 50% . . ...
MORE OF THE ORIGINAlLY SPECIRED SEED MIX TO ANY SLURRY
MIX WHICH HAS NOT BEEN APPLIED WITHIN THE TWO HOURS
AFTER MIXING. THE CONTRACTOR SHALL ADD 75% MORE OF THE
OR!GlNAL SEED MIX TO ANY SLURRY M!XTURE WH!CH Hf1.S NOT BEEN
APPUED EIGHT HOURS AFTER MIXING. ANY MIXTURE NOT APPLIED
AFTER EIGHT HOURS SHAIUL BE REJECTED AND DISPOSED OF
OFf-SITE AT CONTRACTOR'S EXPENSE.
5.· CLEAN UP:
AS PROJECT PROGRESSES, CONTRACTOR SHALL MAINTAIN AUL
AREAS IN A NEAT MANNER AND REMOVE UNSIGHlIL Y DEBRIS AS c'
NECESSARY. AFTER COMPLEl10N OF PROJECT, CONTRACTOR SHAUL·.
REMOVE ALL DEBRIS AND CONTAINERS USED IN ACCOMPUSHING
WORK. HE SHAUL SWEEP AND CLEAN ALL SIDEWALKS, ASPHALT,
AND CONCRETE AREAS ADJACENT TO PLANlINGS.
GPA 04-08/ZC 04-03/LCPA 04-07/CT 04-06
PUD 03-02/ PIP 03-02/CDP 03-06/HDP 03-02.
I SHEET I CITY OF CARLSBAD 1 ENGINEERING DEPARTMENT .
STORM WATER MANAGEMENT PLAN FOR
PALOMAR POINTE
LOTS 1-7. CARLSBAD TRACT NO. CT 04-06
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7801 Mission Center Court, Suite 200 IF P~IZJ f 1tt5c:J'Woifx36". ~
~:::::::::::s:on:D:i~::O:C:O.:9:~:O:8::::::::~ __________________________________________________________________________________________________________________________ ~ __________________________________________________________ ~ ____ ~ ____________________________ _=============s:c.:~:~R==P:~==:A:C:c:ORD==m:G:z:y.:.===========:J~