HomeMy WebLinkAboutCT 13-01; Buena Vista 11; Storm Water Quality CT 13-01; 2013-09-20RECORD COPY
liiitia! Date
Storm Water Management Plan
SWMP 13-13
Buena Vista 11
CT 13-01
DWG. 479-6 & 479-6A
Prepared: September 30, 2013
Revised: November 12, 2013
PREPARED FOR
Kraemer Land Company, inc.
i01 S. Kraemer Blvd., Suite 136
Placentia, CA 92870
(714) 528-9664
RECEIVED
FEB 1 8 2014
LAND UcvcLuHMENT
PROJECT _ENGiNEER ENGINEERING
William Luodstroiii, R.i^.c.
UM<i- u A Wi- n RV
Lundstrom
Engineering and Surveying, Inc.
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Certification
This Storm Water Management Plan (SWMP) has been prepared under the direction of
the following Registered Civil Engineer. The Registered Civil Engmeer attests to the
technical information contained herein and the engineenng data upon which
recommendations, conclusions, and decisions are based. The plans and specifications m
this SWMP are not for construction purposes; the contractor shall refer to final approved
construction documents for plans and specifications.
William Lundstrom Date
Registered Civil Engineer 61630
Exp. Date 6/30/15
Lundstrom ^ ..
Engineering and Survcyins, in'- Page 11
>* r
C i I Y U F
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www/.carlsbadca.gov
INSTRUCTIONS:
To address post-development pollutants that may be generated from development projects, the City requires that new development and
significant redevelopment priority projects incorporate Pemnanent Storm Water Best Management Practices (BMP's) into the project
design per the City's Standard Urban Stomiwater Management Pian (SUSMP). To view the SUSMP, refer to the Engineenng Standards
(Volume 4, Chapter 2) at wwvv.C3rlsbadca.qov/!5tandards.
Initially this questionnaire must be completed by the applicant in advance of submitting for a development application (subdivision,
discretionary pemiits and/or constaiction pennits). The results of the questionnaire determine the level of storm water standards that
must be applied to a proposed development or redevelopment project. Depending on the outcome, your project will either be subject to
'Standard Stomiwater Requirements' or be subject to additional criteria called 'Priority Development Project Requirements'. Many
aspects of project site design are dependent upon the storm water standards applied to a project.
Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts. City staff has
responsibility for making the final assessment after submission of the development application. If staff determines that the questionnaire
was incorrectly filled out and is subject to more stringent storm water standards than initially assessed by you, this will result in the return
ofthe development application as incomplete. In this case, please make the changes to the questionnaire and resubmit to the City.
If you are unsure about the meaning of a question or need help in determining how to respond to one or more of the questions, please
seek assistance from Land Development Engineering staff.
A separate completed and signed questionnaire must be submitted for each new development application submission. Only one
completed and signed questionnaire is required when multiple deveiopment applications for the same project are submitted concurrently.
In addition to this questionnaire, you must also complete, sign and submit a Project Threat Assessment Form with constmction pemnits
for the project.
Please start by completing Step 1 and follow the instructions. When completed, sign the form at the end and submit this with your
application to the city.
STEP1
TO BECOMPLETED FOR ALL PROJECTS :
To determine if your project is a prionty development project, please answer the following questions. YES NO
Is your project LIMITED TO constructing new or retrofitting paved sidewalks, bicycle lanes or trails that meet
the following criteria: (1) Designed and constructed to direct storm water runoff to adjacent vegetated areas, or
other non-erodible permeable areas; OR (2) designed and constmcted to be hydraulically disconnected from
paved streets or roads; OR (3) designed and constructed with permeable pavements or surfaces in
accordance with USEPA Green Streets guidance?
2. Is your project LIMITED TO retrofitting or redeveloping existing paved alleys, streets, or roads that are
designed and constructed in accordance with the USEPA Green Streets guidance?
If you answered "yes" to one or more of the above questions, then your project is NOT a priority development project and therefore is
NOT subject to the stomi water criteria required for priority development projects. Go to step 4, mark the last box stating "my
project does not meet PDP requirements" and complete applicant Information.
If you answered "no" to both questions, then go to Step 2.
E-34 Pace 1 of 3 Effective 6/27/13
I
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Qpyfjmmient Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
STEP 2
o=,-nMoicTcnpr.R AM NFW OR REDEVELOPMENT PROJECTS 1
To determine if your project is a priority development project, please answer the following questions. YES NO
1 is vour project a new development that creates 10,000 square feet or more of impen/ious surfaces collectively
overfhe entire project site? This includes commercial, industrial, residential. m,xed-use, and pubhc
Howpinnmerit nroiects on Dublic or private land. . • 2 tltuZ^e^i^^^^ 5,000 square feet or more of impen/ious surface collectively over the entire
prS; site^Jl an'eSng S of 10,000 square feet or more of impervious surface? ™s/nc/udes commercial,
indtnfrial r^-^M^""'"', miynd-iise, and public development proiects on Dublic or pnvate land, y
3 s vour oroiect a new or redevelopment project that creates 5,000 square feet or more of '["Pf "^^^ surta^e
coSve ^ove^Se entire project site and supports a restaurant? A restaurant is a facility that sells prepared
Sind drinks for consumption, including stationary lunch counters and refreshment stands selling prepared
fnnr/<j and drinks for immediate consumption.
4 Is vour oroiect a new or redevelopment project that creates 5.000 square feet or more or impervious su. Ic^c
over tTTentire pro^site and supports a hillside development project? A hillside development
project includes development on any natural slope that is twenty-five percent or greater.
5 is your project a new or redevelopment project that creates 5,000 square feet or "'^'^P^^'^P^J^'^^^^^
coEve ? over the entire project site and supports a partying lot. A parking loUs alan^^^^ or facility for the
Lrnnrarv n;,*/nf7 or storaoe of mofor vehicles used oersonallv for business or for commerce,
6 HorpToSa new or redevelopment project that creates 5,000 square feet or more of impe^^us surface
coSvey ovefthe entire project site and supports a street, road, highway freeway ^^^'^'^f^^^f^Jj^'^'^,
?oad, 3wIy freeway or driveway is any paved impen/ious surface used for the transportation of
automobiles trucks, motorcycles, and other vehicles. __— —; —
7 fs rufpSecra new or redevelopment project that creates or replaces 2.500 square feet or more of
mpei^^LuTSace Sectively over'the entire site, and discharges directly t°f,,f"™ToL
Area (ESA)? 'Discharging Drectly to' includes flow that is conveyed overland a distance fee or/ess
Zm the project to the ESA or conveyed in a pipe or open channel any distance as an isolated flow from the
nroiect to the ESA (i e. not commingles with flows from adjacent lands). .—-—.
-rifS^ed a new development that supports an automotive repair f'fl,^"'f°;"°^^^^^^^
facility that Is categorized in any one of the following Standard Industnal Classification (SIC) codes. 5013.
5014 5541 7532-7534, or 7536-7539. . • ————— 9 is your project a new development that supports a retail gasoline outlet (RGO)? This category ^.
that meet the following critena: (a) 5.000 square feet or more or (b) a project Average Daily Traffic (ADV of
100 or more vehicles per day. ^ • r;——z—
10. Is your project a new or redevelopment project that results in the disturbance of one or more acres or Und cud
are expected to generate pollutants post construction?
>
11 Is'your project located within 200 feet of the Pacific Ocean and (1) creates 2 500 square feet or more of
• imn»rvinM.s surface or (2) increases impervious surface on the property bv more than 10/o? . __
qSeSmSre cheS^^ project meets PDP requirements" box and complete applicant mfonnation.
information.
E-34 Page 2 of 3 Effective 6/27/13
I CITY OF
.CARLSBAD
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
qpyeioament Services^
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
i
py
I ch
Llllipicw
STEP 4
CHECK THE APPROP"'"!^ BOX AND COf" "^'"^ INFORMATION
"7" M, pr„)e« meets PRIORITY DEVELOPfNT -.ROJECT ^^^^^^
-Applicant Information and Signature Box
I Address;
Applicant Name: j;^^ Bg:t7
1 Applicant Signature: Jy^M-—"
Accesspr's Parcel Number(s): / ^
Applicant Title: ^^^^^
Date:
Th/s Sox for City Use Only
City Concurrence: YES ) NO
Date:
ProjectlD: QIJ^-OI
^Environmentally sensitive Areas includebutarenotn^
enlimnlntS^^^^^^^ a'eas which have been identified by the Copemi.ttees.
E-34 Page 3 of 3 Effective 6/27/13
Table of Contents
ii
Certification
lii
Table of Contents •
iii
Table of Exhibits ;
iv
List of Tables '
5
Introduction ^
Purpose and Scope '5
Regulatory Enviromnent
Section 1. Project Information ^
1.1. Project Description ""^
1.2. Hydrologic Settmg • g
1.3. Proposed Runoff Management Facilities
Section 2. Characterization of Receiving Waters ^
2.1. Beneficial Uses •."
2 2 Characterization of Receivmg Waters: 303(d) hnpamnents
13
Section 3. Design Criteria and Methodology
3.1. Design Criteria ^4
3.2. Hydrologic Design Methodology
Section 4. Characterization of Project Runoff
4.1. Hydrologic Effects of Project
4.2. Potential Pollutants 20
4.3. Conditions of Concem
Section 5. Storm Water Best Management Practice Plan 23
23
5.1. Site Design BMPs 2?
5.2. Source-Control (Pollution Prevention) BMPs
5 3 Treatment Control BMPs
36
Section 6. Hydromodification
39
Section 7. Summary and Conclusions
Table of Exhibits
Exhibit A: Vicinity Map
Exhibit B: Existing Condition Map . ^ —
3 Lundstroiii ...
Engineering ami Sur/cyms, Inc. ragg 111
Exhibit C: Proposed Condition BMP Site Map
List of Tables
Table 1-1 Summary of hnpervious Cover Analysis..... -•""••7""oVn
Table 2-1 Beneficial Uses of Downstream Inland Surface Waters (RWQCB, 1998). 11
Table 2-2 Summary of Receivmg Surface Waters
Table 3-1 Rational Method Runoff Coefficients
Table 4-1 Anticipated and potential pollutants by project type (San Diego County,
2002a)
Table 4-2 Conditions of Concem versus BMP Matrix
• Table 5-1 Site Design BMP Altematives
Table 5-2 Source-control BMP altematives
Table 5-3 Basic Homeowner Outreach Program
Table 5-4 Treatment Control BMP Altematives
Table 5-5 Treatment Control BMP Selection Matrix
Lundstrom
Engineering and .SuTveving, inc. Page iv
Introduction
discharges is through the use of best management practices (BMPs).
Purpose and Scope
Th-.. SWMP has been developed in order to characterize receivmg waters, identify the
report also identifies mamtenance requirements P^^^P^f 1^^^^^^
rSechanisms that will ensure tiiat the BMPs are mamtamed throughout the life of the
project.
Regulatory Environment
The Clean Water Act was amended m 1972 to provide that discharge of PoUut^^ ^
LVnTthe Urdted States witiiout a National Pollution Discharge Elmunation System
™ tri^Us ula^^^ 1990, tiie EPA published fmal regulations (commody
Sed o'asThe Phase E rule) mandating that discharges of stonn water to waters of the
U S. firom construction projects witiiout anNPDES pemut be prohibited.
The Phase I rule describes six minimum control measures that most NPDES General
Pe^ttees will need to implement. These mmhnum control measures
SmenteTby applymg BMPs that are appropriate to tiie project source, location, and
climate. These six minimum control measures are.
Public education and outreach on storm water mipacts;
Public involvement/participation;
Illicit discharge detection and elimuiation;
Construction site storm water runoff control;
Post-constmction stomi water management m new development and redevelopment; and
Pollution prevention/good housekeepmg for municipal operations.
Two of the Phase I minimum control measures, constmction storm water runoff control
Lundstrom P„^-5
Engineering awl Surveying, Inc. S^aB^
for Construction Activities (SWPPP) before coirmiencement °f °f ^^'"^jf'^^^^^
AnnendixD of tliis SWMP summarizes construction-pliase BMPs for ttie s te. ine
t^eTmust also meet the site design, source-control, and post-construction treatn^en
coS™^ water management requirements, which are the pnmary subject of this
report.
Redonal Water Quality Control Board (San Diego Region) Order No. 2007-0001
fcor^ly Cwn as the Municipal Pemiit) defmes urban runoff as a waste, and requ.es
SaXcal municipalities regulate urban mnoff. The Municipal Pemut requires that each
m^cipal^^^^^^ a program to mmmiize or elimmate the negative water quahty
Xts of urban n^off A primary component of this progr^ is to change the
dfveWei^ aS^^^^^ processes and other ordmances to requhe that new development
trsiSli^ apply best management practices (BMPs) to the maxmium
StS'^rS^^^^^ I^e MLcipal Pemiit also defmes specific numenc sizmg
criteria for tiie design of these BMPs (see Section 3).
Lundstrom P .
Engineering ami Sumcying, Inc. J dgc U
Section !. Project Information
1.1.Project Description
1.1.1 Proj ect Location
The site is located southwest ofthe intersection of Buena Vista Way and Valley Street, in
the City of Carlsbad, Califomia.
1.1.2 Proj ect Activities Description
The 2.73-acre project site is cunently situated on moderately slope (4%) ground.
Elevations across the site range fiom approxunately 181 feet above mean sea level
(MSL) at the nortiiwest property comer to approximately 160 feet above MSL along tiie
easterly property line or a distance of 520 feet.
The project proposes the development of eleven single-family residential lots and a
private cul-de-sac.
To comply with cunent stonn water regulations, on-site low unpact design (LED) and
mtegrated management practices (IMP) wiU be unplemented to mitigated anticipated
increase m pollutant loads and peak run-off fi:om the proposed development. Porous
pavers, rock-line yard swales, and underground detention stmctures are proposed to meet
cuirent storm water requirements.
1.2.Hydrologic Setting
This section summarizes tiie project's size and location in the context of the larger
watershed perspective, topography, soil and vegetation conditions, percent hnpervious
area, nahiral and mfrastmcmre dramage features, and other relevant hydrologic and
environmental factors to be protected specific to the project area's watershed.
1.2.1 Watershed
The project site is located m the Buena Vista Creek Hydrologic Area (HA 904.20) and
Carlsbad Hydrologic Unit (HU 904.00).
• 1.2.2 Soil and Vegetation Conditions
Per "Prelimmary Geotechnical Evaluation Buena Vista 11 Subdivision", dated March 13,
2013, by GeoSoils, hic, onsite soils are considered to fall mto Hydrologic Soils Group
"D" as defined m tiie County of San Diego.
The project site is categorized as having non-native vegetation developed or unvegetated
habitat.
Lundstrom Engineering and Surveying, Inc. Pa'^C 7
1.2.3 Impervious Cover
The site cunently has no impervious cover, under the existing condition. The project will
add approximately 6.7-acres of hnpervious area to the project site. Table 1 1
summarizes tiie impervious cover under existmg and proposed condition.
Summary of Impervious Cover Analysis.
Existing Condition Vro^osed Condition
(acre) {%) (^^")
1.3.Proposed Runoff Management Facilities
The proposed facilities managmg mnoff fiom tiie site mclude:
- Appropriate gradmg of pads to direct mnoff away fiom stmctures on the site.
• Bioretention Basms.
. Stonn drain systems to direct on-site mnoff to appropriate outfalls.
Underground detention facilities that will mtercept and release mnoff at a
predetermined rate.
e Lundstrom Engineering and Survcving, Inc. Page 8
Section 2. Characterization of Receiving Waters
Tho Enviromnental Protection Agency (EPA) is the ^^^^ ^f^'^L^f'^Zu^^^^^^
for management of water quality m the United States. The Clean Water Act (CWA is
tiie federal law tiiat govems water quality control activities imtiated by ^^^^ EPA and
others Section 303 of the CWA requhes the adoption of water quality standards for all
surface water m the United States. Under Section 303(d), mdividual states are required to
develop lists of water bodies that do not meet water quality objectives
levels of treatment by pomt source dischargers. Total maxmium daily loads (TMDLs) for
all pollutants for which these water bodies are listed must be developed m order to bnng
them mto compUance witii water quality objectives.
2.1.Beneficial Uses
2.1.1 Definitions
The Porter-Cologne Act establishes a comprehensive Program for ^e Protection °f
beneficial uses of tiie waters of the state. Califomia Water Code Section 13050®
describes tiie beneficial uses of surface and gromid waters that may be designated by the
State or Regional Board for protection as follows:
"Beneficial uses of tiie waters of the state that may be protected _ agamst _ quality
degradation mclude, but are not necessarily lunited to, domestic, mumcipal, agricultural
and mdustrial supply; power generation; recreation; aesthetic enjoyment; navigation, and
preservation and enhancement offish, wildlife, and otiier aquatic resources or preserves.
Beneficial uses for surface waters are designated under the Clean Water Act Section 303
hi accordance with regulations contamed m 40 CFR 131. The State is requued to specity
Appropriate water uses to be achieved and protected. _ The beneficial use design^on of
surface waters of tiie state must take mto consideration tiie use ^d value of water for
public water supplies, protection and propagation of fish, shellfish and wildlife
recreation m and on the water, agricultural, mdustrial and other pmposes mcludmg
navigation.
hi 1972 the State Board adopted a unifonn list and description of beneficial uses to be
applied 'throughout all basms of the State. During the 1994 Basin Plan update beneficia
u?e defmitions were revised and some new beneficial uses were added. Overall, he
followmg twenty-three beneficial uses are now defmed statewide and are designated
withm the San Diego Region:
Munidpai and Domestic Supply, hicludes uses of water for community, military, or
individual water supply systems includmg, but not limited to, dnnkmg water supply.
A'^ricuhural Supply. Includes uses of water for fannhig, horticulture or ranchmg
mcluding, but not limited to, inigation, stock watering, or support of vegetation for range
grazmg.
Lundstrom ^ o
Engineering and Surveying, Inc. rage 7
Ind^istrial Process Supply, hicludes uses of water for industrial activities that depend
primarily on water quality.
Industrial Service Supply, hicludes uses of water for mdustrial activities that do not
?ep nd p^^^^^ water quality including, but not lunited to mmmg, cooling w^^^^^
supply, hydraulic conveyance, gravel washing, fire protection, or oil well re
pressurization.
Ground Water Recharge. Includes uses of water for natural or artificial recharge of
^3 wSof^Sipofes of feture extraction, maintenance of water quahty, or haltmg
of saltwater mtrusion into fieshwater aquifers.
Freshwater Replenishment hicludes uses of water for natiiral or artificial mamtenance
of surface water quantity or quality (e.g., salmity).
Navigation, hicludes uses of water for shipping, travel, or otiier transportation by
private, military, or commercial vessels.
Hydropower Generation, hicludes uses of water for hydropower generation.
Contact Water Recreation, hicludes uses of water for recreational activities involvmg
bXc n^cf ;fh water, where mgestion of water is —^^^.P-f ^.^^^^^
hiclude, but are not lunited to, swhmnmg, wadmg, water-skimg, skm and SCUBA divmg,
surfing, white water activities, fishing, or use of natural hot spnngs.
Non-Contact Water Recreation, hicludes the uses of water for recreational activities
^^olvbs pro^Lty to water, but not nomiaUy mvolvmg body contact with water, where
S In of^^is reasonably possible. These uses mclude, but are not limited to
SclSa slbathing, hikmg, beachcombmg, campmg, boatmg, tidepool and m^me
SrstTyTh^nrsiWg, or aesthetic enjoyment m conjunction with the above
activities.
Commercial and Sport Fishing, hicludes the uses of water for commercial or
r^creXnal collection of fish, shellfish, or other organisms mcludmg, but not Imuted to,
uses involving organisms mtended for human consumption or bait purposes.
Aauaculture. Includes the uses of water for aquaculmre or mariculture operations
Sdtg but not lunited to, propagation, cultivation, mamtenance, or harvesting of
aquatic plants and annuals for human consumption or bait purposes.
Warm Freshwater Habitat, hicludes uses of water that support warm water ecosystems
Sing, burnot lunited to, preservation or enhancement of aquatic habitats, vegetation,
fish or wildlife, mcludmg invertebrates.
Cold Freshwater Habitat, hicludes uses of water that support cold water ecosystems
SudTng but not lunited to, preservation or enhancement of aquatic habitats, vegetation,
fish or wildlife, including uivertebrates. ^
Lundstrom P
Engineering and Surveying, Int. rage IV
Inland Saline Water Habitat. Includes uses of water that support mland salme water
ecosystems mcluding, but not lunited to, preservation or enhancement of aquatic salme
habitats, vegetation, fish, or wildlife, mcludmg invertebrates.
Estuarine Habitat, hicludes uses of water that support estoarme ecosystems includmg,
but not lunited to, preservation or enhancement of estiiarine habitats, vegetation, fish,
shellfish, or wildlife (e.g., estuarine mammals, waterfowl, shoreburds)
Marine Habitat, hicludes uses of water that support manne ecosystems mcluding but
not limited to, preservation or enhancement of marine habitats, vegetation such as kelp,
fish, shellfish, or wildlife (e.g., marine mammals, shoreburds).
Wildlife Habitat, hicludes uses of water that support tenestrial ecosystems mcludmg but
not hmited to, preservation and enhancement of tenestrial habitats vegetahon v^ldl^^^^
(e.g., mammals, birds, reptiles, amphibians, uivertebrates), or wildlife water and food
sources.
Preservation of Biological Habitats of Special Significance. Includes uses of water that
fupport designated aTeas or habitats, such as ^S^' P^^^'
ecological reserves, or Areas of Special Biological Sigmficance (ASBS), where the
preservation or enhancement of natiiral resources requhes special protection.
2.1.2 Beneficial Uses: hiland Surface Waters
The RWQCB San Diego Basm Plan identifies several beneficial uses of receiving mland
I^fecfwaters Table 2-1 summarizes the beneficial uses identified for downstream
inland surface waters.
Table 2-1 Beneficial Uses of Downstream Inland Surface Waters (RWQCB, 1998).
® Existing Beneficial Use
O Potential Beneficial Use
+ Exempt from Municipal Use
Beneficial Use
Receiving Water
(Hydrologic Unit Code)
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Buena Vista Creek (HA 904.20)
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Lundstrom
Engineering and Surveying, Inc. Page 11
2.2.Characterization of Receiving Waters: 303(d) Impairments
The most immediate receiving water for the project site is Buena Vista Lagoon accordmg
I thrCaSiia 2010 303(d) hst pubhshed by the San Diego Regional Water Quality
Co«r(^^^^^^^ Region 9). Table 2-2 summarizes the receivmg waters and
their classification by the RWQCB Region 9
Table 2-2 Summary of Receiving Surface Waters.
Receiving Water
Hydrologic
Unit Code
Approximate
Distance From Site
303(d) Impairment(s)
e Lundstrom Engineering and Surveying, lnc Page 12
Section 3. Design Criteria and Methodology
This section summarizes tiie design criteria and methodology apphed during drainage
analysis of the project she. The design criteria and methodology follow the County of
San Diego Hydrology Manual, Hydrauhc Design and Procedure Manual, and Storm
Water Standards as appropriate for the project site.
3.1.Design Criteria
3.1.1 Volume-Based Water Quahty Numeric Sizmg Criteria
Volume-based BMPs are designed to capture and treat tiie most frequent storm events.
Volume-based BMPs mclude extended detention basms, wet detention basins, and water
quahty treatment wetlands.
The water quality caphire volume may be included as part ofthe configuration ofthe
detention basms (for example, in a forebay or as mitial storage m the basm), or as a
stand-alone water quality basui. The water quality volumes should be provided m
addition to the flood-control detention volume and debris volumes allocated for each
basin.
The San Diego Regional Water Quality Control Board (RWQCB Region 9) has defmed
the sizing criteria for volume-based Best Management Practices as:
The volume of runoff produced from each and every storm event up to and including a
historical record-based reference 24-hour rainfall criterion for treatment (0.6 inch
approximate average for the San Diego County area) that achieves approximately the
same reduction in pollutant loads achieved by the 85th percentile 24-hour event
A 24-hour, 0.6-mch rainfall has a retum frequency of less than one year. The 85th
percentile 24-hour event criterion can be used for sizhig tiie volume-based water quality
treatment controls within the project site.
3.1.2 Flow-Based Water Quality Numeric Sizing Criteria
Flow-based BMPs are sized to filter or otherwise treat the peak flow of mnoff from a
stormwater quality storm event. Flow-based BMPs include bioretention basins.
The San Diego RWQCB has defmed the design discharge for flow-based BMPs as the
mnoff generated from a storm with a rainfall intensity of 0.2 mch/hour. Flow-based water
quality BMPs on the project site have been designed based upon a Rational Method
analysis of this design storm, which is slightly larger than the 85th percentile event
(0.1 inch/hour).
Lundstrom
Engineering and Surveying, Inc. Pa^^e 13
3.2.Hydrologic Design Methodology .
3.2.1 Rational Method: Peak Flow
Runoff calculations for this study were accomplished usmg the Rational Metiiod. The
Rational Metiiod is a physically-based numerical ^^^-^^^^^^^^^
directty proportional to ramfaU and area, less losses for mfiltration and depression
storage. Flows were computed based on the Rafional fonnula:
Q=CiA
where... Q= Peak discharge (cfs);
C = runoff coefficient, based on land use and
soil type;
i= rainfall mtensity (in/hr);
A = watershed area (acre)
The mnoff coefficient represents the ratio of ramfaU tiiat mns off the watershed versus
the portion tiiat infiltrates to tiie soil or is held m depression storage. Tlie mnoff
coefficient is dependent on tiie land use coverage and soil type (Table 3-1).
For a typical dramage shidy, ramfaU mtensity varies with tiie watershed time of
concentSion. The watershed thne of concentration at any given pomt is defmed as he
Ze h would theoreticaUy take mnoff to travel from the most upsfream pomt m the
rtershed to a concentration pomt, as calculated by equations m the San Diego County
Hydrology Manual.
Table 3-1 Rational Method Runoff Coefficients,
LANDUSE (CountyElements) RUNOFF COEFFICIENT
SCS Soil Type A B C D
Pennanent Open Space 0.20 0.25 0.30 0.35
Residential, 1.0 DU/A or less 0.27 0.32 0.36 0.41
Residential, 2.0 DU/A or less 0.34 0.38 0.42 0.46
Residential, 2.9 DU/A or less 0.38 0.41 0.45 0.49
Residential, 4.3 DU/A or less 0.41 0.45 0.48 0.52
Residential, 7.3 DU/A or less 0.48 0.51 0.54 0.57
Residential, 10.9 DU/A or less 0.52 0.54 0.57 0.60
Residential, 14.5 DU/A or less 0.55 0.58 0.60 0.63
Residential, 24.0 DU/A or less 0.66 0.67 0.69 0.71
Residential, 43.0 DU/A or less 0.76 0,77 0.78 0.79
Neighborhood Commercial 0.76 0.77 0.78 0.79
General Commercial 0.80 0.80 0.81 0.82
Office Professional/Commercial 0.83 0.84 0.84 0.85
Limited Industrial 0.83 0.84 0.84 0.85
General Industrial 0.87 0.87 0.87 0.87
Lundstrom ^
Engineering and Surveying, Inc. rage 14
Rational Method calculations were accomplished using the Advanced Engineering
Software Rational Method Analysis (Southem Califomia County Methods) (AES-
RATSCx) computer software package. Peak discharges were computed for 50-year, 10-
year, and 2-year hypothetical storm retum frequencies.
3.2.2 Rational Method: Runoff Volume
For designs that are dependent on the total storm volume, a hydrograph must be
generated to account for the entire volume of mnoff from the 6-hour storm event. The
hydrograph for the enthe 6-hour storm event is generated by creating a rainfaU
distribution consisting of blocks of rain, creating an mcremental hydrograph for each
block of rain, and adding the hydrographs from each block of rain. This process creates a
hydrograph that contains runoff from all the blocks of rain and accounts for the enthe
volume of runoff from the 6-hour storm event. The total volume under the resulting
hydrograph is equal to the following equation:
V0L = CP6A
Where: VOL = volume of runoff (acres-inches)
Pa = 6-hour rainfall (iuches)
C = runoff coefficient
A = area of the watershed (acres)
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Engineering ajid Surveying, Inc. Page 15
Section 4. Characterization of Project Runoff
This section characterizes the quantities and location of storni water runoff from the
project site and the pollutants that might potentially be present in the ranoff from tiie
project site.
4.1.Hydrologic Effects of Project
The project will add approxunately 1.2-acres of new hnpervious area (44 percent oftiie
project site) m tiie forni of rooftops, and streets. The proposed project wiU not
sionificantty alter tiie overall dramage scheme for tiie site. Exhibit C illustrates tiie
proposed condition hydrology map. Table 4-1 summarizes tiie hydrologic effects of the
project.
Table 4-1 Summary of Hydrology Analysis at Node #1 (outfall).
Tributary Area 100-Year 10-Year 2-Year
Existing/Proposed Existing/Proposed Existing/Proposed Existing/Proposed
(acre)/(acre) (cfs)/(cfs) (cfs)/(cfs) (cfs)/(cfs)
15.5 15.5 43.0 45.1 26.4 28.5 18.8 21.3
The existmg and proposed condition anatyses illustrate that there is an mcrease amount of
ranoff generated from the proposed condition, hi order to mitigate peak ranoff rates we
are proposmg to utilize an underground detention basin for tiie project.
Lundstrom Engineering and Surveying, Inc. Page 16
4.2.Potential Pollutants
The proposed project is not expected to generate significant amounts of pollutants, but
many constituents are generaUy anticipated for projects m tiiis category.
An evaluation of the project's potential effect on water quality identifies several
constituents of concem:
an mcrease m sedunent discharge due to the concenfration of flows on tiie site;
an mcrease m nutrients from fertUizers and eroded soUs;
litter and frash coUecting m the dramage systems;
metals;
oxygen-demandmg substances mcludmg biodegradable organic material and chemicals;
oUs, grease, and other hydrocarbons emanating from paved areas on the site;
bacteria and vmises caused by the transport of anhnal or human fecal wastes; and
pesticides used to control nuisance growth.
a Lundstrom Engineering and Survt7ing, Inc. Page 17
Table 4-1 Anticipated and potential pollutants by project type (San Diego County, 2002a).
•/ Anticipated Pollutants
P Potential PoUutants
General Pollutant Categoi -ies
Priority Project Categories Sediments Nutrients Heavy Metals Organic Substances Trash and Debris Oxygen-Demanding Substances Oils and Grease Bacteria and Viruses Pesticides Detached Residential SM Uli ilili lii •
Attached Residential • p(i) P'
2) p
Commercial (> 100,000 sf) pd) pd) pP) p(5) p(3) p(5)
Auto Repair Shops V •
Restaurants • • •
Hillside Development (>5,000 sf) • •
Paridng Lots p(i) pd) pd) p(l)
Streets, Highways, and Freeways • p(i) • p('i) V p(5)
Retail Gasoline Outlets p('t) V
(1) A potential pollutant i) landscapmg exists on-sue; [i/ A yuii^nuui i,ui.^.^„. .j ...^ ^ -J-- •••-
aLs; (3) A potential pollutant if land use involved food or animal waste products: (4) Including petroleum
hydrocarbons; (5) Including solvents.
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Engineering and Sunty ing, Inc. Page 18
4.2.1 Sediment
Sediments are soils or other surface materials eroded and then transported or deposited by
the action of wmd, water, ice, or gravity. Sediments can mcrease turbidity, clog fish gills,
reduce spawning habhat, lower young aquatic organisms survival rates, smother bottom
dweUing organisms, and suppress aquatic vegetation growth.
4.2.2 Nutrients
Nutrients are inorganic substances, such as nitrogen and phosphoras. They commonly
exist in the form of mineral sahs that are either dissolved or suspended in water. Primary
sources of nutrients in urban runoff are fertilizers and eroded soils. Excessive discharge
of nutrients to water bodies and sfreams can cause excessive aquatic algae and plant
growtii. Such excessive production, refened to as cultural eufrophication, 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.
4.2.3 Trash and Debris
Trash (such as paper, plastic, polystyrene packing foam, and alummum materials) and
biodegradable organic matter (such as leaves, grass cuttmgs, and food waste) are general
waste products on the landscape. The presence of trash and 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.
4.2.4 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-demandmg compounds. The oxygen
demand of a substance can lead to depletion of dissolved oxygen m a water body and
possibly the development of septic conditions.
4.2.5 Oil and Grease
Oil and grease are characterized as high-molecular weight organic compounds. The
primary sources of oil and grease are petroleum hydrocarbon products, motor products
from leakmg 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 constraction areas. Elevated oil and grease content can decrease the
aesthetic value of the water body, as well as the water quality.
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Engineering and Surveying, Inc.
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4.2.6 Bacteria and Virases
Bacteria and virases are ubiquitous microorganisms that thrive under certain
environmental conditions. Theu proliferation is typically caused by the transport of
animal or human fecal wastes from the watershed. Water containing excessive bacteria
and virases can alter the aquatic habitat and create a harmful environment for humans and
aquatic life. Also, the decomposition of excess organic waste causes increased growth of
undeshable organisms in the water.
4.2.7 Pesticides
Pesticides (including herbicides) are chemical compoimds commonly used to confrol
nuisance growth of organisms. Excessive application of a pesticide may result in nmoff
containing toxic levels of its active component.
4.2.8 Metals
Metals are raw material components in non-metal products such as fuels, adhesives,
paints and other coatings. Primary source of metal pollution in storm water are typically
commercially available metals and metal products. Metals of concem 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
naturaUy occurring in soU, metals are not toxic. However, at higher concentrations,
certain metals can be toxic to aquatic hfe. Humans can be impacted from contaminated
groundwater resources, and bioaccumulation of metals in fish and
shellfish. Envhonmental concems, regarding the potential for release of metals to the
envnonment, have aheady led to restricted metal usage in certain applications.
4.3. Conditions of Concern
The most immediate receiving water for the project site is Buena Vista Lagoon. Buena
Vista Lagoon flows to the Pacific Ocean. According to the California 2010 303(d) list
published by the San Diego Regional Water Quality Control Board (RWQCB Region 9),
San Diego Bay is impahed for bacteria, nutrients and sediment.
Conelating the potential pollutants from this residential development and the known
impairments of the downstream water bodies reveals several conditions of concem. The
secondary pollutants of concem from this development will be (1) an increase in
sedunent discharge from the site due to concentration of fiows (which may cany
adsorbed pollutants of concem); (2) organics; (3) nutrients; (4) trash (such as paper,
plastic, polystyrene packing foam, and aluminum materials) and biodegradable organic
matter (such as leaves, grass cuttings, and food waste), which may create a "habitat" for
harmful bacteria; (5) pesticides, oils, grease, and other hydrocarbons from landscaped
areas, parking lots, and driveways; (6) metals; (7) BOD (oxygen demanding materials).
Sediment discharge and eroded soil are of most concem during constraction phase of the
project, A complete program of constraction Best Management Practices (BMPs) will be
developed for the project site, and will be described in a Storm Water Pollution
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Page 20
Prevention Program (SWPPP) for Constraction Activities as part of the approval of the
final^Xg plans. The constraction BMPs wiU address this conditon of concem during
the constraction phase.
Sedunent discharge and eroded soU wiU also be a '^^^^'^^^.f'':"?'^^^^^^
is complete. On one hand, levelmg and stabilizing tiie site might ^c^f ^J^^^^^^^
sedunent yield from the site. However, concentration of flows at the culverts will
potSy generate erosive conditions on hillsides. Riprap protection, landscape
L other measures wiU be taken to ensure tiiat the constmcted slopes aoid areas
downstream of culverts are adequatdy protected from concenfrated stomi water flows.
other common pollutants from detached residential housmg have the Potenti^J. ^
conSbute to dolsfream hnpamnents. Eroded soils may mcrease total dissolved sohd ,
a^d may cany nufrients like phosphorous mto downsfream receivmg waters.
Sode^adabHaterials m frash can lower dissolved oxygen. It is possible tiiat pe waste
"fribute to downstream colifomi and bacterial hnpamnents Proposed bioreten^^^^^
Ws wUl mitigate tiie pollutants of concem to the maxmimn extent practical (Section 5,
"Storni Water Best Management Practice Plan") after constraction is complete.
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Engineering and Surveying, Inc. ragC / I
Table 4-2 Conditions of Concem versus BMP Matrix.
Condition of Concern
(Impairments)
Potential Aggravating Pollutant Permanent Best Management
Source(s) Practice(s)
Bacterial Indicators Trash and Gross Pollutants Bioretention
Heavy Metals
Organic Compounds
Trash and Debris
Commercially available metals
and metal products
Carbon-based compounds
General waste products on the
landscape
Bioretention
Bioretention
Bioretention & Underground
Detention
Oxygen Demanding Substances Biodegradable material Bioretention
Oils and Grease
Sedunent
High-molecular weight
compounds
Accumulation from wind
Bioretention
Bioretention & Underground
Detention
Nutrients
Pesticides
Degradation of organic matter Bioretention
Landscaping practices Bioretention
8 Lundstrom Engineering and Surveying, Inc. Page 22
Section 5. Storm Water Best Management Practice
Plan
This SWMP incorporates three major types of best management practices (BMPs).
These types are (1) she design BMPs; (2) source confrol BMPs; and (3) treatment control
BMPs. The SWMP applies general site design and source control BMPs, and targets
anticipated potential storm water pollutants with treatment-control BMPs applied to the
maximum extent possible.
S.l.Site Design BMPs
Site design BMPs aim to conserve natural areas and minimize impervious cover,
especially impervious areas 'directly connected' to receiving waters, in order to maintain
or reduce increases in peak flow velocities from the project site. The U.S. EPA (2002)
has listed several site design BMPs that can be implemented development projects. The
project has mcorporated she design BMPs to the maximum extent possible. Table 5-1
lists site-design BMP altematives and indicates the practices that have been apphed to the
project site.
Table 5-1 Site Design BMP Altematives.
• Buffer Zones • Open Space Design
H Narrower Residential Streets El "Green" Paridng (Turfstone-Grass Pavers)
• Altemative Turnarounds • Altemative Pavers
• Urban Forestry • Conservation Easements
• Elimiuating Curbs And Gutters M Landscape Design
H Other (Explained Below)
5.1.1 Selection of Site Design
Selection of She Design BMPs is limited in the context of the present project. The
design aspects hiclude designing residential streets to the minimum width requhed by
City standards, and there will also be efficient landscape inigation installed. The roof
ranoff will be directed to landscape areas, where possible, before discharging to storm
drains.
5.1.2 Landscape Design
Efficient landscape design and inigation practices can be an effective source-control to
prevent pollution in storm water and dry-weather flows. The completed project will
implement principles of common-area efficient irrigation, runoff-minimizhig landscape
design,-and an effective landscape maintenance plan to the maximum extent possible.
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Engineering and Surveying, Inc. Pa^^C 23
Common-Area Efficient Irrigation
Automatic inigation systems (if mstaUed) should mclude water sensors programmable
hri-ation timers, automatic valves to shut-off water m case of rapid pressure_ drop
(mdicatmg possible water leaks), or other measures to ensure the efficient application ot
water to the landscape and prevent unnecessary runoff from hrigation. Dnp irngation
and otiier low-water urigation metiiods should be considered where feasible. Common
elements of efficient irrigation programs hiclude:
Reset irrigation confroUers according to seasonal needs.
Do not over-water landscape plants or lawns.
Keep hrigation equipment m good working condition.
Promptly repah aU water leaks.
Runoff-Minimizing Landscape Design
Landscape designs that group plants witii sunilar water reqmrements can reduce excess
urination ranoff and promote surface mfiltration. Landscape designs should ufrlize non-
mvasive native plant species and plants witii low water requuements when possible.
Landscape Maintenance
The landscape mamtenance plan should mclude a regular sweepmg program of
hnpervious surfaces, litter pick-up, and proper equipment mamtenance (preferably ott-
she), and proper use of chemicals to help elhmnate sources of stonn water poUutants.
Common elements of an effective landscape maintenance plan mclude:
Implementmg a regular program of sweepmg sidewaUcs, driveways, and gutters as part of
tiie landscape mamtenance plan. Pick-up litter frequentty. Provide convement frash
receptacles for public use if necessary.
Avoid usmg water to clean sidewalks, driveways, and other areas.
Discourage washmg of landscape mamtenance equipment on-she. Mhihnize water use
and do not use soaps or chemicals. Use a commercial wash-rack facility whenever
possible.
Keep landscape maintenance equipment in good workmg order. Fix all leaks promptly,
and use drip pans/drip cloths when drammg and replacing fluids. Collect all spent fluids
and dispose of them property. Designate equipment mamtenance areas that are away
from storai water mlets. Perfonn major mamtenance and repaus off-site if feasible.
Materials with the potential to pollute ranoff (soU, pesticides, herbicides, fertilizers,
detergents, petroleum products, and otiier materials) should be handled, delivered,
apphed and disposed of with care followmg manufachirer's labeled duectons and m
accordance with all apphcable Federal, state, and local regulations. Matenals wtil be
stored under cover or otherwise protected when rain is forecast or dunng wet weather.
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Engineering and Surveying, Inc. FagC Z4
5.1.3 Narrower Residential Sfreets
A narrow street in a residential neighbortiood.
Cars can be parked in^ driveways or along the
road shoulder
Description
This better site design practice promotes tiie use of nan:ower sfreets to reduce tiie amount
of hnpervious cover created by new residential development and, m tiim, reduce the _
stonn water ranoff and associated pollutant loads. Cunently, many commumties requue
wide residential streets that are 32, 36, and even 40 feet wide. These wide streets provide
two parkmg lanes and two movmg lanes, but provide much more parking than is acttiaUy
necessary, hi many residential settmgs, sfreets can be as nanow as 22 to 26 fee wide
without sacrificmg emergency access, on-street parkmg or vehicular and pedestnan
safety Even nanower access streets or shared driveways can be used when only a
handfiil of homes need to be served. However, developers often have little flexibility to
desicm nanower sfreets, as most communities requhe wide residential sfreets as a
standard element of theu local road and zonmg standards. Revisions to cunent local road
standards are often needed to promote more widespread use of nanrower residential
sfreets Turfstone - Grass Pavers will be InstaUed along Buena Vista Way and VaUey
Street as shown on Exhibit 'C. Specifications are provided at the end of this report.
Applicability
Nanower streets can be used in residential development settings that generate 500 or
fewer average daity trips (ADT), which is generaUy about 50 single family homes, and
may sometimes also be feasible for streets that are projected to have 500 to 1,000 ADT.
However nanower sfreets are not feasible for arterials, coUectors, and other street types
that cany' greater fraffic volumes or are not expected to have a constant traffic volume
over time.
In most communities, existing local road standards wiU need to be modified to pennit the
use of nanower sfreets. Several communities have successfiilty implemented nanower
streets, mcludmg Portland, OR; Bucks County, PA; Boulder, CO; and throughout New
8 Lundstrom ^ Engineering and Surveving, Inc. r agC Z J
Jersey, hi addhion, there are numerous examples of communities where developers have
successfully nanowed private sfreets within innovative subdivisions.
Siting and Design Conditions
Residential sfreet design requhes a careful balancmg of many competing objectives:
design, speed, fraffic volume, emergency access, parkmg, and safety. Communities that
want to change theu road standards to pennit nanower sfreets need to mvolve all tiie
stakeholders who mfluence sfreet design m the revision process. Several excellent
references on narrow sfreet design are provided at tiie end of this fact sheet.
Limitations
A number of real and perceived baniers hmder wider acceptance of narrower sfreets at
the local level. Advocates for nanrower sfreets wiU need to respond to the concems of
many local agencies and the general pubhc. Some of tiie more frequent concems about
nanower sfreets are listed below.
. Inadequate On-Street Parking. Recent research and local experience have_
demonstrated that narrow sfreets can easily accommodate residential parking
demand. A smgle family home typically requhes 2 to 2.5 parkmg spaces, hi most
residential zones, tiiis parkmg demand can be easily satisfied by one parkhig lane
on the street and driveways.
. Car and Pedestrian Safety. Recent research mdicates that nanow sfreets have
lower accident rates than wide streets. Nanow sfreets tend to lower the speed of
vehicles and act as traffic cahnmg devices.
. Emergency Access. When designed properly, narrower streets can easily
accommodate fire tracks, ambulances and other emergency vehicles.
. Large Vehicles, Field tests have shown that school buses, garbage tracks, movmg
vans, and otiier large vehicles can generally safely negotiate nanower sfreets,
even when cars are parked on both sides of the sfreet. hi regions with high
snowfall, streets may need to be slightly wider to accommodate snowplows and
other equipment.
. Utility Corridors. It is often necessary to place utihties underneath the street
rather than in the right of way.
hi addition, local communities may lack the authority to change road standards when the
review of public roads is retained by state agencies. In these cases, sfreet nanowmg can
be accomplished only on private sfreets (i.e., mamtamed by residents rather than a local
or state agency).
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Engineering and Surveying, Inc. Page 26
Maintenance Considerations
Nanower sfreets should shghtly reduce road maintenance costs for local communities,
since they present a smaller surface area to maintain and repair.
Effectiveness
Smce streets constittite the largest share of hnpervious cover in residential developments
(about 40 to 50 percent), a shift to narrower sfreets can result in a 5-to 20-percent overall
reduction m hnpervious area for a typical residential subdivision (Schueler, 1995). As
nearly aU the pollutants deposited on street surfaces or frapped along curbs are delivered
to the storm dram system during stonn events, this reduced hnperviousness franslates
dhectly mto less storm water runoff and pollutant loadings from tiie development. From
the standpomt of storm water quality, residential sfreets rank as a major source area for
many storm water pollutants, includmg sedunent, bacteria, nutrients, hydrocarbons, and
metals (Bannerman, 1994).
Cost Considerations
Narrower streets cost less to buUd tiian wider sfreets. Considerhig that tiie cost of pavmg
a road averages $15 per square yard, shavmg even a mere four feet from existmg sfreet
widths can yield cost savmgs of more tiian' $35,000 per mile of residential street, hi
addition, smce nanower streets produce less hnpervious cover and runoff, addttional
savmgs'can be realized m the reduced size and cost of downstream storai water
management facilities.
5.2.Source-Control (Pollution Prevention) BMPs
Source-confrol BMPs are activities, practices, and procedures (primarily non-stracttiral)
that are designed to prevent urban runoff pollution. These measures either reduce the
amount of runoff from the she or prevent contact between potential pollutants and stoma
water. Also, source-confrol BMPs are often the best metiiod to address non-storm (dry-
weather) flows. Table 5-2 lists source-control BMP ahematives and mdicates tiie
practices that wiU be apphed at the project site.
Table 5-2 Source-control BMP altematives.
H Storm Dram Stenciling and Signage El Homeowner Oufreach
S Material and Trash Storage Area Design • Lawn and Gardening Practices
m Efficient Irrigation Systems • Water Conservation
lEl Low-Irrigation Landscape Design • Hazardous Waste Management
• On-Lot Treatment Measures • Trash Management
• Riprap or Other Flow Energy Dissipation • Outreach for Commercial Activities
• Other (Explained Below)
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Engineering and .Surveying, Inc. Pa^^C 27
5.2.1 Selection of Source-Control BMPs
Selection of Source Control BMPs is limited in the context of the present project. The
residential development includes common areas that will be administered by a
homeowners association (HOA), which makes it feasible to apply storm drain stenciling,
efficient inigation systems, homeowner outreach, and on-lot freatment measures.
5.2.2 Material and Trash Storage Area Design
Storage areas such as for landscaping supplies and trash storage areas will be designed to
contain materials stored in these areas and to prevent debris from being distributed into
storm water coUection areas. For example, dumpsters wiU be kept in a separate enclosed
area to prevent debris from being scattered by wind or animals.
5.2.3 Efficient Irrigation Systems
Storm drain stenciling involves labeling storm drain inlets with painted messages
warning citizens not to dump pollutants into the drains. The stenciled messages are
generally a simple phrase to remind passersby that the storm drains connect to local water
bodies (and not to a sanitary sewer system) and that dumping pollutes those waters.
Some specify which water body the inlet drains to or name the particttlar river, lake, or.
bay. Commonly stencUed messages include:
"No Dumping. Drains to Water Source"
"Drains to River"
"You Dump it. You Drmk h. No Waste Here."
Pictures can also be used to convey the message, including a dolphin, whale, duck,
common game fish, or a graphic depiction of the path from drain to waterbody.
Communities with a large Spanish-speaking population might wish to develop stencils hi
both English and Spanish, or use a graphic.
DOB' Ni) mwm
5.2.4 Efficient Inigation Systems
Irrigation water provided to landscaped areas may result in excess hrigation water being
conveyed into stormwater drainage systems.
Project plan designs for development and redevelopment should include application
methods of inigation water that minimize runoff of excess hrigation water into the
stormwater conveyance system.
e Lundstrom Engineering and Surveying, Inc. Page 28
Appropriate applications include residential, commercial and industrial areas planned for
development or redevelopment. (Detached residential single-family homes are typically
excluded from this requirement.)
The following methods to reduce excessive hrigation runoff should be considered, and
incorporated and implemented where determined applicable and feasible by the
Permittee:
Employ rain-triggered shutoff devices to prevent irrigation after precipitation.
Design irrigation systems to each landscape area's specific water requhements.
Include design featuring flow reducers or shutoff valves triggered by a pressure drop to
control water loss hi the event of broken sprinkler heads or lines.
Implement landscape plans consistent with County or City water conservation
resolutions, which may include provision of water sensors, programmable hrigation times
(for short cycles), etc.
Design timing and apphcation methods of inigation water to minimize the runoff of
excess inigation water into the storm water drainage system.
Group plants with similar water requhements in order to reduce excess irrigation ranoff
and promote surface filtration. Choose plants with low irrigation requhements (for
example, native or drought tolerant species). Consider design features such as:
Using mulches (such as wood chips or bar) hi planter areas without ground cover to
minimize sediment in runoff
Installing appropriate plant materials for the location, hi accordance with amount of
sunlight and climate, and use native plant materials where possible and/or as
recommended by the landscape architect
Leaving a vegetative barrier along the property boundary and hiterior watercourses, to act
as a pollutant filter, where appropriate and feasible
Choosing plants that mhiimize or eliminate the use of fertilizer or pesticides to sustain
growth
Employ other comparable, equally effective methods to reduce irrigation water ranoff.
5.2.5 On-Lot Treatment
"On-lot treatment" describes a series of practices designed to treat runoff from individual
residential lots. Their primary purpose is to manage rooftop, driveway and sidewalk
ranoff. Managing ranoff from these sources helps to disconnect impervious surfaces and
to reduce the effect of increased impervious cover in a watershed.
With few exceptions, some sort of on-lot treatment can be applied to almost all sites.
However, while on-site treatment of residential storm water ranoff has been encouraged,
it has not generally been an option to meet storm water requirements. This practice is
changing, as municipalities and other storm water regulators realize the value of these
3 Lundstrom
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treatment processes. According to the EPA, there are cunentty at least two jurisdictions
that offer "credits" m exchange for the application of on-she storni water management
practices
Project Location
Detachmg roof leaders wiU be used on all homes buih withm tiie proposed project
Runoff will also be diverted to a pervious area or to a landscaped area on each mdmdual
lot usmg site grading, channels or berais. Yard drams wiU collect tiie ranoff, post
filtration, from the landscaped lots.
Sitmg and Design Considerations
Although most residential lots can mcorporate on-lot treatment, tiie best option for a she
depends botii on site design constramts and tiie preferences of the homeowner.
Bioretention and vegetated swales need to meet tiie sitmg requhements of those practices.
The use of cisterns and ram barrels has far fewer she consframts. However, for this
practice to be effective, homeowners must have a use for the stored water. These
practices are therefore best suited to homeowners who have some active mterest m
gardening or landscaping.
Altiiouah tiiese practices are shnple compared with many other post-constiruction storai
water practices, the designs need to mcorporate the same basic elements of any other
storai water practice. Prefreataient is hnportant to ensure that tiiese practices, such a root
leaders, do not become clogged with leaf debris. Ram banels and cisterns should also
mcorporate some sort of pretreatment, such as a mesh filter at tiie top of the banel or
cistern.
Storac^e practices should also typicaUy mcorporate some type of bypass so that larger
storais flow away from the house. In ram banels or cisterns, this bypass may be a hose
set at a hi-^h level of the practice and dhected away from the practice and bmldmg
foundation." For bioretention, an on-lme design dhects aU flows to the management
practice, but larger flows generally flow over the practice and are not treated.
Maintenance Requhements
Bioretention areas, filter strips, and vegetated swales require regular maintenance to
ensure that the vegetation remams m good condition. Rain banels and cisterns requue
minhnal mamtenance, but the homeowner needs to ensure that the tank is cleaned out
approximately once per year.
Pollutant Removal
Although the practices used for on-lot applications can have relatively high pollutant
removals, it is not clear that tiiese pollutant removal rates can be realized with the
relativety low pollutant concentrations entering the practices. One clearty recogmzable
benefit of many on-lot practices, however, is that they generaUy promote ground water
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Engineeririg and Surveying, Inc. ragC JU
recharge, either directly through infiltration or indhectly by applying or dhecthig ranoff
to pervious services.
5.2.6 Homeowner Outreach
One source-control best management practice for residential sites is pollution prevention
outreach. The key to a successfiil outreach campaign is to target a message to a specific
audience, such as homeowners. At the sale of the property or lease- signmg, tiie
homeowner or tenant can be presented with a brochure to encourage them to develop and
implement source-confrol best management practices. Another strategy is to attach
brochures as non-bmdmg but informative parts of private road mamtenance or stractural
BMP maintenance agreements that might be used for ensuring the maintenance of the
stractural freatment confrol measures. Primaty areas of source-control BMP for
homeowners hiclude:
Lawn and Garden Activities. Lawn and garden activities can result in contamination of
storm water through pesticide, soil, and fertihzer runoff. Proper landscape management,
however, can effectively reduce water use and contaminant ranoff and enhance the
aesthetics of a property. Envhonmentally friendly landscape management can protect the
envhonment through careful plannmg and design, routine soU analysis, appropriate plant
selection, use of practical ttirf areas, water use efficiency, use of mulches, and appropriate
maintenance. Additional activities that benefit water resources hiclude maintahiing
healthy plants and lawns and composting lawn wastes. Healthy plants are less susceptible
to diseases and insects and therefore requhe minimal use of pest control measures. To
promote healthy plants, it is often beneficial to tiU composted material into the soU.
Recycling of garden wastes by composting is also effective at reducing waste, although
compost bins and piles should not be located next to waterways or storm drains because
leachate from compost materials can cause contamination. • -
Water Conservation Practices. By making minor changes in water use habhs, each
household can reduce hs water consumption while saving money on water and sewage
biUs. Homeowners can be made aware of practices like checking regularly for plumbhig
leaks and checkmg for water leaks by monitoring then water meters when no water is
being used (such as when they go on vacation).
Pet Waste Management. When pet waste is not properly disposed of, it can wash mto
nearby waterbodies or can be canied by runoff into storm drains. Homeowners should be
encouraged to dispose of pet waste with regular trash, bury h m then yards, or flush h
down the toilet.
Trash Management. Homeowners should be informed about then options for recycling
and waste disposal, as weU as the consequences of littering. It is especially important to
inform residents of proper disposal procedures for household hazardous wastes.
Lundstrom
£nginccri)ig and Surveying, Inc. Page 31
Table 5-3 Basic Homeowner Outreach Program.
tiniir hotline 1-888-846-0800, -__ha^hom^l:^m^^:S r-^ r;^r;fl^^^6l^^rf^i^^^
-^-^;;^^;;^^;jr-g^^ waste out of gutters and streets by placmg
0 Clean up and properly dispose of pet waste. It x ^ J Tdeenf
^glacingtatotrash^^ '
Source:mm.co.san-diego.ca.us/deh/stormwater/residential.html
5 3 Treatment Control BMPs
r^~=r.:^fS9—^^^^
to protect water quality tiiroughout tiie life oftiie project. Sfructo^
element of post-consfruction storai water management. BMPs have varying g
effectiveness versus different pollutants of concem.
selection, .esisna.dsi.in, of—B^^^^^
project-wide dramage plan. BMP f "T" j'^, (see Section 3);
institutional constrauits. .
Table 5-4 lists .reanBen.-con,rol BMP al.ema.ives and identifies the BMPs selected for
the project site.
5 3 1 Selection of Treahnent-Confrol BMPs
the site.
The following BMPs were analyzed for use on site. A brief explanation on why they
were not used is also mcluded. ^
T^indsSpm
Engineering and Sun'Q'ing, Inc.
Page 32
Treatment Control BMP Selection Matrix
Lundstrom
Engineering and Sun't7liig, Int.
Page 35
Section 6. Hydromodification
Project ranoff dhectty discharges mto an existmg public ^^onn f in systo^^^^^^^^
conveyance) which outfalls into Buena Vista Lagoon per Plate A-1, Mast^^ Plan ol
DraLaaTFacilities, on the following pages. A recent sttidy of Buena Vista Lagoon,
^nXmodmcatioi Exemption Anafysis for Select Carlsbad Watersheds", dated June
10 20lTby Chang Consultants concludes that Buena Vista Lagoon is a stabilized
cLeyan'ce System Sid therefore, exempted from hydromodification requuements.
Lundstrom 3.
Engineering and Surveying, Inc. rdgC .JU
S E C T I O
, .OEWT..V POLLUTANTS, BMP S.Z.NO ANO SSLHCT.ON
t4 Hidremcdif.cMion Comrtl; Reqareil
I Entiof 0«irignl'l3tr« I
Vefei to cspiiudecimtP ^emption caerii iteriis beloT for jus-jficadoas leg-.mgd on each noce
30 City of Cai lsbad SUSMP - January 14, 2011
LunSstrom
Engineering and Sui-vc)'ing, Int.
Page 37
S Lundstrom P 3„ Engineering and Surveying, Inc. ^ rdgC JO
Section 7. Summary and Conclusions
This SWMP has evaluated the potential effects on water quality ofthe proposed project
by identifying characteristics of receivhig waters, potential pollutants from the proposed
project, and the most appropriate best management practices (BMPs) to address these
constittients. These BMPs hiclude measures related to site design, source confrol, and
treattnent confrol. In addition, tiie report has addressed the maintenance requhements and
recommended mechanisms to ensure that post-constraction treatment-confrol BMPs wiU
be mamtamed tiiroughout the life of the project. This section provides a summary
discussion that evaluates the potential effects of the proposed project on water resources
with aU BMPs in place.
Bioretention basms are proposed to treat bacteria, TSS, metals, nifrogen, phosphoras and
organic matter to meet current storm water requhements. The stated BMP address the
pollutants of concem to the masdmum extent practical and wiU help prevent adverse
effects to the quality of water in the area.
The existmg and proposed condition analyses illusfrate that there is an mcrease in runoff
generated from tiie proposed condition, hi order to mitigate 100-year peak runoff rate, an
underground detention basin wiU be utilized.
Project runoff dhectly discharges mto an existmg pubhc storm dram system (stabUized
conveyance) which outfalls mto Buena Vista Lagoon per Plate A-1, Master Plan of
Dramage Facilities. A recent sttidy of Buena Vista Lagoon, "Hydromodification
Exemption Analysis for Select Carlsbad Watersheds", dated June 10, 2013, by Chang
Consultants concludes tiiat Buena Vista Lagoon is a stabilized conveyance system and
therefore, exempted from hydromodification requirements.
Lundstrom
Engineering and Sur\'eying, Inc. PagC 39
EXHIBITS
REGION REGION NAME
Regional Board 9 - San Diego Region
Regional Board 9 - San Diego Region
Regional Board 9 - San Diego Region
Regional Board 9 - San Diego Region
Regional Board 9 - San Diego Region
Regional Board 9 - San Diego Region
Regional Board 9 - San Diego Region
Buena Vista Lagoon
Water quality limited ocgmonto
WATER BODY NAME
Buena Vista lagoon
Buena Vista Lagoon
Buena Vista Lagoon
Buena Visla Lagoon
Buena Vista Lagoon
Chollas Creek
|010 c^HM303(d)H|Hvater <jHBi
cjquiring a TMDL(6A). being oddrcoood by
WATER BODY TYPE
Estuary
Estuary
Estuary
Estuary
Estuary
Estuary
River & Stream
CALWATER
WATERSHED
90421000
90421000
90421000
90421000
ESTIMATED
SIZE
AITECTED
202
202
UNIT
Acres
90421000
202
202
POLLUTANT
Indicator Bacteria
Indicator Bacteria
Nutrients
Acres Sedimentation/Siltation
Sedimentation/Siltation
Copper
Pallhogens
POLLUTANT
CATEGORY
Palliogens
Nutrients
Sediment
FINAL LISTING DECISION
List on 303(d) list CTMDL required list)
List on 303(d) list (TMDL required list)
Ust on 303(d) lisl (TMDL required lisl)
List on 303(d) list (TMDL required list)
Metals/Metalloids
Ust on 303(d) list (TMDL required list)
List on 303(d) list (TMDL required list)
Ust on 303(d) list (TMDL required list)
County off San Diego
Hydrology Manual
Soil Hydrologic Group
Legend
"Major Roads
*^ Incorporated city Bdy
HYDROLOOC SOIL GROUP
Hydroiogic^roup Undefinad
•Hydro loglcSroup A
Hydro knflc IS niupB
HydrologlcSisup c
"HydrologicGroup D
'-No Soil Dala
Note: Soil Data Source
USDA/MRCS
SSURGD Soils 2007
N
A
I—I—I
31,50 3 Miles
*GIS ssacis
THIS MW B PROVIDED «rmOUT WWtHANTY OF «4Y KWD, EFTHEHBCPRESSOR WPLED. NCUJOWG. BUT NOT UMITED
TO "EMPUEO WMnm-UBS OF MERCHANTABIUTIV AND
FfTNESS FOR A/PAHTICULAR PURPOSE. Capyfi^SftnCt5.AI Rights RMMVWL
Thi. pwduct nwf contain i*nn-too Ih. SANOAG^^
pamiMiM Df SANDAG.
Thi. pwduet itm contain l*bnTi.6on wtadi IMM) r.pr*iiracl
with painmien ^mrltad by Thorn.* BroB-r. M.p..
DMA# COVER BMP# BMP Type
Pollutants of
Concern
Removal
Efficiency
DMA Area
(ac.)
"C"
DMA
Runoff
Factor
Water
Quality Flow
Rate [cfs)
(lwq =
0.2in/hr)
Bioretention Sizing
Factor 15 in/hr, 4%)
BMP
Volume (V1)
6" Ponding
(cf)
BMP Area
Required
(sf)
BMP Area
Provided
(sf)
1A Pervious/landscape 1 Biotentention M-H 0.145 0.10 0.003 0.04 48 25 190
1B Impervious 1 Biotentention M-H 0.091 1.00 0.018 0.04 48 159
190
2A Pervious/landscape 2 Biotentention M-H 0.112 0.10 0.002 0.04 45 20 180
2B Impervious 2 Biotentention M-H 0.082 1.00 0.016 0.04 45 143
180
3A Pervious/landscape 3 Biotentention M-H 0.101 0.10 0.002 0.04 45 18 180
3B Impervious 3 Biotentention M-H 0.069 1.00 0.014 0.04 45 120
180
4A Pervious/landscape 4 Biotentention M-H 0.104 0.10 0.002 0.04 45 18 180
48 Impervious 4 Biotentention M-H 0.064 1.00 0.013 0.04 45 111
180
5A Pervious/landscape 5 Biotentention M-H 0.126 0.10 0.003 0.04 45 22 180
58 Impervious 5 Biotentention M-H 0.075 1.00 0.015 0.04 45 130
180
6A Pervious/landscape 6 Biotentention M-H 0.075 0.10 0.002 0.04 45 13 180
68 Impervious 6 Biotentention M-H 0.102 1.00 0.020 0.04 45 178
180
7A Pervious/landscape 7 Biotentention M-H 0.111 0.10 0.002 0.04 45 19 180
78 Impervious 7 Biotentention M-H 0.070 1.00 0.014 0.04 45 122
180
8A Pervious/landscape 8 Biotentention M-H 0.101 0.10 0.002 0.04 45 18 180
88 Impervious 8 Biotentention M-H 0.083 1.00 0.017 0.04 45 145 180
9A Pervious/landscape 9 Biotentention M-H 0.115 0.10 0.002 0.04 45 20 180
98 Impervious 9 Biotentention M-H 0.072 1.00 0.014 0.04 45 125
180
10A Pervious/landscape 10 Biotentention M-H 0.095 0.10 0.002 0.04 45 17 180
108 Impervious 10 Biotentention M-H 0.079 1.00 0.016 0.04 45 138
180
11A Pervious/landscape 11 Biotentention M-H 0.072 0.10 0.001 0.04 45 13 180
118 Impervious 11 Biotentention M-H 0.094 1.00 0.019 0.04 45 164 180
12A Pervious/landscape 12 Biotentention M-H 0.046 0.10 0.001 0.04 350 8 700
128 Impervious 12 Biotentention M-H 0.383 1.00 0.077 0.04 350 667
700
I
ORCO PAVINGSTONES •:• WW.ORCO.COM
1 7-i in '/a in) ** See Payings:one Dimensions secrion for acmal measurements CONVERSION; 80 mm = 3.125 in U /a in; •^icc 5
3.125 in
(80 mm)
23.5 in
(597 mm)
15.66 in
(397 mm)
Tisk ww.orco.com for the latest information on avail-
able color blends, solid colors, and patterns. Befote
ordeting, always verify color and texture with paving-
stone samples.
ORCO Block Co., Inc. manufactures pavingstones in
accordance with ASTM C936-J2 StamUnlSpecijicatm fnr
Solid Concrete Interlocking Paving Units and tested using
ASTM €140-12 StandardTest Methods for Sampling and
Testing Concrete Masonrj Units and Mated Units. ORCO
certifies that our pavingstones' average minimum
comptessive strength exceed 8000 psi with water
absorption no greater than 5%.
For proper instaUation procedures, visit the Interlocking
Concrete Pavement Instimte (ICPI) at www.icpi.org.
See Tech Spec #2 - Construaion of Interlocking Concrete
Pavements. In addition, ICPIs Guide Specifications
provide information for installation of larger pavers,
slabs, permeable systems, and using alternative setting
beds—like concrete, mortar, and bituminous asphalt.
ICPI recommends using ICPI Certified Installers, who
are trained in paver standards, materials, and techniques.
Complete ORCO Terms of Sale and applicable warranty
information are available at www.orco.com.
ADivislonarORCOBIockCo.
WWW.0RC0.COM
951.685.8498
OOB.CO Block Co. 9/12
Pervious Pavements
Design Objectives
0
0
0
0
Maximize Infiltration
Provide Retention
Siow Runoff
Minimize Impen/ious Land
Coverage
Prohibit Dumping of Improper
Materials
Contain Pollutants
Collect and Convey
Description ^vincr arp^s The term describes a system
Pervious pa^g is used for ^'^^^'^^.'"^'^i^r^^^JM-^^i
compiisingaload-beaiiBg, ^^fl^ JSt^^tra^^^^ The surface can
temporarily stores water pnor to "ff^f*^™ " f ^^face ofthe material (e.g., grass
itseifbeporoussuchthatwatermffltra^esa^^^^^^
s:5^Zs=rr^»-^^^^^
Xt'SS?ea^~^e==t.g.aMgh^^^^^
r2::tfflowispro,Beab,^^^^^^^^
together with appropnate flow controls. ™ cycle. Alternatively, where
refharge, this conributix« f^"'*^"'^:,XraW5 is UgH. We is
animpemie^te merabrane. The system offers
^T^il'otai^fcrd^S^eofspatiailycoostrainedurbanarea^
Si^cantattenuationandimprov^^^^^
^.5^!^frs»"fpS^^
Suitable Applications
Residential commercial and industrial applications.are possible^
?he use oFpermeable pavement may be restricted m cold regions,
Irid regioi^ or regions with high wind erosionjhere are some
SecSSdvant^ages associated with penneablep
which ar e as follows;
Januar7 2003
California StormwatEr BMP Handbook
Mew Development and Redevelopment
www .cabmpha ndbooks.com
lof 10
|D-20
when blocked or damaged.
Their apphcationshouldbe limitedto ^f^^^^^^^^^^^ -trT'
peeds Oess than 30 mphlimit) car V^^ f^^eon "dSlLable for adoptable
tr'afacked areas. Permeable smfaces are cm en^^^ i^pHcations of
roads due to the risks associated with failure on hign speea
ponding, and disruption arising from reconstruction.
Whenusingmi-W,ir.ntrationsystem.^^^^^^^
The use of penneable pavement is restricted to gentle slopes.
f Porous bloa pavmg has a higher risk of abrasion and dama^^ than sohd bbcb.
Design Considerations
Designing NevlTistaUations j ™„„.qw»ter conations are suitable,
'ifthe^ades, subsoils, "."^^t^^iTp^tmeSo^^^^ areas, culde sacs
Swt,JeCtLt;?r==-^^^^
The suitabm^ of a pervious system at aparticuta pavement s.e wi^ however, depend onthe
bading criteria required ofthe pavement.
water table shouldbe at least 4 feet below the surface,
shouldbe considered:
2 of 10
California StormwatEr BMP Handbook
Mew Development and Redevelopment
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January 2003
Pervious Pavements
. Waterispresentwithintheconstructionandcansottenandweakenmaterials.andthismust
be allowed for.
. Porousasphaltbsesadhesionandbecomesbrittleasairpassesthroughthevolds. Its
durability is therefore lower than conventional matenals.
The sin^esi^edgradingofmaterialsusedmeans that caresbouldbetaiento ensure fliat loss of
finer particles between unbound layers does not occur.
PosMoning ageotextile near the surface of the^r^o^^r^^^^
Lfltoioii. only alimited amomt of the constmcuo^^^^
below the geotextile is protected In addation^ ^tSf "^po^dt Som^^ to lower
=etSSS?i^c2^^^^^^^^
The design should ensure that sufEcient void space e^dsts for the storage of sediments to hmrt
the period between remedial works.
wetting and drying should be assessed.
• tss^;Ss==.^rrc^=eibrt£S^=
rock material with a high surface friction
InpoMtioncontroltenns. these layersrepresent^^^^^^
pollutant retention and degradation processes. ^^ processes In
^^^^
fwd provide favorable sites for colonization by microbial populations.
3 of 10
t
-20 Pervious Pavemems
I
•
I • I
The blocks should be lain level
Theyshouldnotbeusedfcrstorageofsitematerials,unlessflresurfaceiswellprotected
fi:om deposition of silt and other spillages.
Thepavementshouldbec—dmas^^^^^
rjSort:S^Xi.ors:il.omfl.source.
Surfaeesdraiuingto^epavementshouldbestab^cdbeforecons^uctionofthepavement
.appropriate cons^ctione^uipmentsho^dbCept away ftomthepavemcntto prevent
damage to the surface, sub-base or sub-grade.
feri:^cr.r:n.ofaperv^ —
l^fjr^f^Se^^^^^^
t Type of use
Ownership
a Level of trafficking
. The local environment and my contributing catchments
S^dies^theUKhaveshowns..™^^^
mamtenance for over lo years and ^^^^^^J^J^Xut mamtenance. However, performance
sSrrr^-°^='^^^^^^^
regimes:
4 of 10
California StormwatEr BMP Handbook
New Development and Redevelopment
www.cabmphandbooks.com
January 2003
Pervious Pavements SD-zu
^^^^{^ Typical Recommended Maintenance Regimes
Activity
Minimize use of salt or grit for de-icing
Keep landscaped areas well maintained
Prevent soil beingwashed onto pavement
Schedule
Ongoing
Vacuum clean surface using commercially available sweeping
machines atthe following times:
- End of winter (April)
- Mid-summer (July / August)
- AfterAutumn leaf-fall (November)
2/3 X per year
Inspect outlets
Tf rnutine cleaning does not restore infiltration rates then
reSnS^cion S^Jart ofthe whole of a pervious surface may be
required.
The surface area affected by hydrauUc failure should be lifted for
inspection ofthe intemal materials to identify the location and
extent ofthe blockage.
Surface materials should be Ufted and replaced after brush
cleaning Geotextiles may need complete replacement.
Sub-surface layers may need cleaning and replacing.
Removed silts may need to be disposed of as controlled waste.
As needed (infrequent)
Maximum 15-20 years
Permeable pa^-ements are up to — (^^^^^
forms of pavement construction), '"^^'^ k f^oTexoensi^^ smfacing, the extra cost of
Table 1 gives US cost estimates for capital and maintenance costs of porous pavements
(Landphair et al., 2000)
Redeveloping Existing Installations , . . ^. , rqmMP WOMP etc)
Variousim'^dictionalstormwatern^ag^m^^^^^^^^
above shouldbe followed.
January 2003 California StormwatEr BMP Handbook
Mew Development and Redevelopment
www .cabmpha ndbooks.com
5 of 10
i D-20 Pervious Pavements
•additional Information
!:l?aS~tsareupto.a.cheaperCora^^^^
I.rms of pavement constmction), "^tx^Se smfacmg, the extra cost of
ccomit.(Acccptingfl^the porous asphaltits^s^^^^ which is offset by the savings inunderground pipework etcHINwmczyn
lable a gives US cost estimates for capital and maintenance costs of porous pavements
(Landphair et al, 2000)
6 of 10
Pervious PaveSTenfS
Table 2 Engineer's Estimate for Porous Pavement
January 2003
California StDnmwater BMP Handbook
Mew Development and Redevelopment
www.cabmphandbooks.cBm
7 of 10
12:^ Pervious Pavements
I
/V1P3AU. .
Brbu/i UUl.<J.y<L-^y"--- - r J]
Cor^tmctionlndus^Researchandlnfomratiou^^Ca^^^
K-s-=tbs^-r?——^^^^
Portland Oregon, September 2002.
^^^^^
KobayashiM., r999. Stonnwater mnotfcontrolinNagoyaCiti,. Proc. Sthint Conf. on
UrbanStormDramagc, Sydney, Austraha, pp.825-833.
^a^e-fir;i»^^^^^^
1837-1, College Station, Texas.
KiemczynowiczJ. Hogland W. «8^Yobr"(ETrp^b1« Topics in Drainage Hydraulics and Hydrology. BC. Yen (.M.), puo
Research, pp 19-80.
reS-aS==rrri^-^^^^^
University, UK December 2001.
Pratt C.J.. 1995. Infiltration drainage - case smdies of UKpractice. ProjectReport
8 of 10
Califomia Stormwater BMP Handbook
Mew Development and Redevelopment
www.cabmphandbooks.com
January 2003
Pervious Pavements SD-20
22,Constmction Industry Research and Infonnation Association, London, SWiP 3AU; also
known as National Rivers Authority R&D Note 485
Pratt C J 1990. Pemieable Pavements for Stormwater QuaHty Enhancement. In: Urban
LSnlter Quahty Enhancement - Source Control, retrofitting and combmed sewer
technology, Ed. H.C. Torno, ASCE, ISBN 087262 7594, PP-131-155
Raimbault G., 1997 French Developments m Reservoir Structures Sustamable water resomces I
the 21=* century. Mahno Sweden
Schliiter W & Jefferies C. Monitoring the outflow from aPorous CarPar^ J^oc. First National
Conference on Sustainable Drainage Systems, Coventry June 2001.
WildTC Jefferies C, andD'Arcy, B.J. SUDS in Scotland - the Scottish SUDS database
ReportNostS
Edinburgh. In preparation August 2002.
January 2003 California StormwatEr BMP Handbook
Mew Development and Redevelopment
www.cabmphandbooks.com
SD-20 Pervious Pavements
C3«oiex!ile — Penrieablii _—J . cvertfew C3«oiex!ile —
.. . •., .•.•^
• .'y'- - », r"-—-
- •" Eulj-base J •'•
;:;r^4-i3:~.^ To furaier
•-' ijsalrrKiil Ulspoaul
or reuse
If •
ImpurmaaWti —-^
- •" Eulj-base J •'•
;:;r^4-i3:~.^ To furaier
•-' ijsalrrKiil Ulspoaul
or reuse •SeotsxSUe- ' T ' T Inliltralian •
\a 1 Pervious p.T/emenl Med hr att»«iuali<io (tJ) Pervious pavsnienl iiwd for inliltration
Schematics of a Pervious Pavement System
10 of 10 California Stormwater BMP Handbook
Mew Development and Redevelopment
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January 2003
Bioretention TC-32
Design Considerations
• Soil for Infiltration
• Tributary Area
• Slope
• Aesthetics
• Environmental Side-effects
Description
The bioretention best management practice (BMP) functions as a
soil and plant-based filtration device that removes pollutants
through a variety of physical, biological, and chemical treatment
processes. These facilities normally consist of a grass buffer
strip, sand bed, ponding area, organic layer or mulch layer,
planting soil, and plants. The runoffs velocity is reduced by
passing over or through buffer strip and subsequently distributed
evenly along a ponding area. Exfiltration of the stored water in
the bioretention area planting soil into the underlying soils
occurs over a period of days.
California Experience
None documented. Bioretention lias been used as a stormwater
BMP since 1992. In addition to Prince George's County, MD and
Alexandria, VA, bioretention has been used successfully at urban
and suburban areas in Montgomery County, MD; Baltimore
County, MD; Chesterfield County, VA; Prince William County,
VA; Smith Mountam Lake State Park, VA; and Gary, NC.
Advantages
• Bioretention provides stormwater treatment that enhances
the quality of downstream water bodies by temporarily
storing runoff in the BMP and releasing it over a period of
four days to the receiving water (EPA, 1999)-
• The vegetation provides shade and wind breaks, absorbs
noise, and improves an area's landscape.
Limitations
• The bioretention BMP is not recommended for areas with
slopes greater than 20% or where mature tree removal would
Targeted Constituents
0 Sediment '
0 Nutrients >
0 Ti^sh I
0 Metals 1
0 Bacteria 1
0 Oil and Grease '
0 Organics '
Legend fRemova/Effectiveness)
• Low • High
A Medium
January 2003 California Stormwater BMP Handbook
Mew Development and Redevelopment
www.cabmphandbooks.com
lof 8
jC_32 Bioretention
be required since clogging may result, particularly if the BMP receives runoff with high
sediment loads (EPA, 1999)-
. Bioretention is not a suitable BMP at locations where tiie water table is witiiin 6 feet of the
ground surface and where the surrounding soil stratum is unstable.
. By design, bioretention BMPshave tiie potential to create vety attractive habitats for _
mosquitoes and otiier vectors because of highly organic, often heavily vegetated areas mixed
v/ith shallow water.
. In cold chmates the soil may freeze, preventing runoff from infiltiating into the planting soil.
Design and Sizing Guidelines
. The bioretention area should be sized to capture the design storm runoff.
. In areas where the native soil permeabihty is less tiian 0.5 in/br an underdrain should be
provided.
. Recommended minimum dimensions are 15 feet by 40 feet, although the preferred widtii is
25 feet. Excavated depth should be 4 feet
• Area should drain completely within 72 hours.
. Approximately itiee or shrub per 50 ft? of bioretention area should be included.
• Cover area with about 3 inches of mulch.
Cons triiction/InspectioTi Considerations
Bioretention area should not be established until contiibuting watershed is stabihzed
Performance
Bioretention removes stormwater pollutants tiirough physical and biological processes,
including adsorption, fati-ation, plantuptake, microbial activity decomposition, sedimentation
and volatilization (EPA, 1999)- Adsorption is the process whereby particulate pdlutants attach
.to soil (e g clay) or vegetation surfaces. Adequate contact time between the surface and
poRutanmustbeprovidedfor in the design of the systemfortiiisremovdproc^
Thus tiie infilti-ation rate oftiie soils mustnot exceed tiiose specified in tiie design cntena or
pollutant removal may decrease. PoUutants removed by adsorption include metals, phosphorus,
andhydrocarbons. Ftitiation occurs as nmoff passes tiirough tiie bioretention area media, such
as the sand b ed, groimd cover, and planting soil.
Common particulates removed from stormwater include particulate organic matter, _
phosphonis, and suspended soHds. Biological processes tiiat occur in wetiands result m
poUutantuptakebyplantsandmicroorganismsintiiesoil. Plant growth is sustamed by ^e
uptake of nutiients from tiie soils, witii woody plants Ipckmg up tiiese nutrients tiirough tiie
seasons Microbial activity within tiie soil also contiibutes to tiie removal of mtrogen and
organic matter. Nitirogenisremovedbynitiifyinganddenitiifymgbactena, while aerobic
bacteria are responsible for tiie decomposition oftiie organic matter. Microbialprocesses
require oxygen and can result in depleted oxygen levels if the bioretention area is not adequately
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Bioretention TC-32
aerated. Sedimentation occurs m tiie swale or ponding area as tiie velocity slows and solids fall
out of suspension.
Hie removal effectiveness of bioretention has been stiidied during field and laboratory stodies
and nutrients are shown in Table i. Table 1 Laboratory and Estimated
Bioretention Davis et a I. (1998);
PGDER(1993)
Pollutant Removal Rate
TotalPhosphorus 70-83%
Metals ecu, Zn,Pb) 93-98%
TEK 68-80%
Total Suspended Solids 90%
Organics 90%
Bacteria 90%
— :
Results for botii tiie laboratoty and field experiments were Similar for e^ach of ^e pdlutants
SSySrDoXg or hdviiigtiie M^^^^
pollutants concentiations (D avis et d, 1998) •
The microbial activity and plant uptake occuning m the bioretention area wiUhkely result in
higher removal rates tiian those determinedf or infiltiation BMi^s.
Siting Criteria ^ 4.
Bioretention BMPs are generally used to tieat stormwater from uupemous smfaces at
commerddres^^^^^ Implementation of bioretention for
ZZ^^^'^^^nt is ideal for median ships, parking lot islands and swales^ Moreover,
SJToffL fliesf areas can be designed to eitiier divert directiy mto tiie bioretention area or
convey into tiie bioretention areaby a curb and guti:er cohection system.
The bestlocationfor bioretention areas is uplandfrominletstiiatreceivesheetflowfromsraded
SLaSSSstiiatwi^ Inordertomaxmnzetiealmient
SeXenessTe site must be graded m such a way tiiat mmhmzes erosive condition, as sheet
flowlTconveyedto tiie tieatment area. Locations where a bioretention area canbe reaily
inc^rSedmto tiie site plan witiiout fijrther environmental damage are preferred.
S^ortreffectively minimize sedimentloato^
shouldbe usedin stabilized drainage areas.
January 2003 California Stormwater BMP Handbook
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TC-32 Bioretention
Additional Design Guidelines
The layout of the bioretention area is determined after site constiaints such as location of
utilities, underlying soils, existing vegetation, and drainage are considered (EPA, 1999). Sites
with loamy sand soils are especially appropriate for bioretention because the excavated soil can
be backfilled and used as the planting soil, thus eliminating the cost of importing planting soil.
The use of bioretention may not be feasible given an mstable sunounding soil stratum, soils
with clay content greater than 25 percent, a site with slopes greater than 20 percent, and/or a
site with mature tiees that would be removed during construction of the BMP.
Bioretention can be designed to be off-Hne or on-line oftiie existing drainage system (EPA,
1999). The drainage area for a bioretention area should be between 0.1 and 0.4 hectares (0.25
and 1.0 acres). Larger drainage areas may require multiple bioretention areas. Furthermore,
the maximum drainage area for a bioretention area is determined by the expected rainfall
intensity and runoff rate. Stabilized areas may erode when velocities are greater than 5 feet per
second (1.5 meter per second). The designer should determine the potential for erosive
conditions at the site.
The size of the bioretention area, which is a function of the drainage area and the runoff
generated from the area is sized to capture the water quaHty volume.
The recommended minimuTn dimensions of the bioretention area are 15 feet (4.6 meters) wide
by 40 feet (12.2 meters) long, where the minimnm width allows enough space for a dense,
randomly-distributed area of trees and shrubs to become established. Thus replicating a natural
forest and creating a microclimate, thereby enabling the bioretention area to tolerate fhe effects
of heat stiess, acid rain, runoff pollutants, and insect and disease infestations which landscaped
areas iu urban settings typically are unable to tolerate. The prefened width is 25 feet (7.6
meters), with a length of twice the widtii. Essentially, any fadlities wider than 20 feet (6.1
meters) should be twice as long as they are wide, which promotes the distribution of flow and
decreases the chances of concenttated flow.
In order to provide adequate storage and prevent water from standing for excessive periods of
time the ponding depth of the bioretention area should not exceed 6 inches (15 centimeters).
Water should not be left to stand for more than 72 hours. Arestriction on the type of plants that
can be used may be necessary due to some plants' water intolerance. Furthermore,"if water is
left standing for longer than 72 hours mosquitoes and other insects may start to breed.
The appropriate planting soil should be backfilled into the excavated bioretention area. Planting
sofls should be sandy loam, loamy sand, or loam texture with a clay content ranging from 10 to
25 percent.
Generally the soil should have infiltiation rates greater than 0.5 inches (1.25 centimeters) per
hour, which is typical of sandy loams, loamy sands, or loams. The pH of the soil should range
between 5.5 and 6.5, where pollutants such as organic nitrogen and phosphorus can be adsorbed
by the sofl and microbial activity can flourish. Additional requirements for the planting soil
include a 1.5 to 3 percent organic content and a maximum 500 ppm concentiation of soluble
salts.
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Bioretention ICS!
Soil tests should be performed for every 500 cubic yards (382 cubic meters) of planting sofl,
witil the exception of pH and organic content tests, wHch are requu-ed only once per
bioretention La (EPA, 1999). Planting soil shouldbe 4 inches (10.1 centimeters) deeper tiian
tiie bottom of tiie largestrootbanand4feet(i.2meters)altogetiier.ms depth
adequate soil for tiie plants' root systems to become established, prevent plant damage due to
severe wind, and provide adequate moistiire capacity. Most sites wfll requure excavation m
order to obtain the recommended deptii.
Planting soil deptiis of greater tiim 4 feet (1.2 meters) ^^ay^^q^^'^^J^^^^,"?^^^^^ „^
practices such £ shoring measures (EPA 1999)- Planting sofl should be placed m 18 mches or
™ter IfftsmdHghtiy compacted until tiie desireddeptii is reached Smce high canopy tiees
Say be dStioyed during mdntenance tiie bioretention area should be vegetated to resemble a
terrestiial forest community ecosystem that is dominated by understoiy tiees. "Ihree ^peoes
each of botii tiees and shmbs are recommended to be plantedat a rate of 2500 frees andshnibs
per hectare (1000 per acre). For instance, a 15 foot (4.6 meter) by 40 foot (12.2 meter)
bioretention area (600 square feet or 5575 square meters) would require 14 tiees and shmbs.
The shmb-to-tiee ratio shouldbe 2:1 to 3:1.
Treesandshmbsshouldbeplantedwhenconditionsarefavorable. Vegetation should be
watered at tiie end of each day for fourteen days following its planting. Plant species tolerant of
poflutantloads and varying wet and dty conditions shouldbe used m tiie bioretention area.
The desimer should assess aestiietics, site layout, md mainteiiance requiremaits when
selecting plant species. Adjacent non-native mvasivespedes should be identified and the
designer should take measures, such as providmg a sofl breach to ehmmate the tijreat of to
species invading tiie bioretention area. Regional landscaping manuals should be consulted to
ensure tiiat tiie planting of flie bioretention area meets tiie landscaping requhements
estabhshed by flie local autiiorities. The designers should evaluate tiie best placement of
vegetiitionwitijintiiebioretentionarea. Plants shouldbe placed at irregular mtervals to
replicate a natiiral forest. Trees shouldbe placed on tiie perimeter oftiie area to P^o^^de diade
and shelter from tiie wmd. Trees and shmbs can be sheltered from damagmg flows if fliey are
placed away from tiie patii of flie incoming nmoff In cold clhaates, species tiiat are more
tolerantto cold winds, such as evergreens, shouldbe placed in windier areas oftiie site.
FoUowing placement oftiie frees and shmbs, tiie ground cover and/or miflch shouldbe
established. Ground cover such as grasses or legmnes can be planted attiie begmnmg ofthe
growing season. Muldishouldbeplacedunmediately after tiees and shmbs are planted. Two
to 3 inches (5 to 7.6 cm) of commerdafly-avaflable fine shredded haxdwood mulch or shredded
hardwood chips should be appHed to tiie bioretention area to protectfrom erosion.
Maintenance
'The primary maintenmce requfrement for bioretention areas is tiiat of inspection and repau- or
replacemeiit of tiie treatinent area's components. Generafly, this involves noflmg more tiian flie
routine periodic maintenance tiiat is required of any landscaped area. Plante tiiat are
appropriate for tiie site, cHmatic, and watering conditions shouldbe sdectedfor use intiie
bioretention cell. Appropriately sdected plants wfll aide in reducmg feriflizer, pesticide, water,
and overafl mamtenance requiremente. Bioretention system components should blend over
time tiirough plant and root growtii, organic decomposition, and tiie development of a nattjral
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TC-32 Bioretention
sofl horizon. These biologic and physical processes over time will lengthen the facility's life span
and reduce the need for extensive maintenance.
Routine maintenance should include a biarmual health evaluation of the tiees and shmbs and
subsequent removal of any dead or diseased vegetation (EPA, 1999)- Diseased vegetation
shouldbe heated as needed using preventative and low-toxic measures to the extent possible.
BMPs have the potential to create very attractive habitats for mosquitoes and other vectors
b ecause of highly organic, often heavfly vegetated areas mixed with shaflow water. Routine
inspections for areas of standing water within the BMP and corrective measures to restore
proper infiltration rates are fiecessary to prevent creating mosquito and other vector habitat In
addition, bioretention BMPs are susceptible to invasion by aggressive plant spedes such as
cattafls, which increase the chances of water standing and subsequent vector production ff not
routinely maintained.
In order to maintain the treatment area's appearance it may be necessary to pnme and weed.
Furthermore, mulch replacement is suggested when erosion is evident or when fhe site begins to
look unattractive. Specificafly, the entire area may requfre mulch replacement every two to
three years, although spot mulching may be suffident when there are random void areas. Mulch
replacement should be done prior to the start of the wet season.
New Jersey's Department of Environmental Protection states in their bioretention systems
standards that accumulated sediment and debris removal (espedally at the inflow point) wiU
normafly be the primary maintenance function. Other potential tasks include replacement of
dead vegetation, sofl pH regulation, erosion repafr at inflow pointe, mulch replenishment,
im clogging the underdrain, and repairing overflow structures. There is also the possibility that
the cation exchange capadty of the sofls in the cefl wfll be significantiy reduced over time.
Depending on poflutant loads, sofls may need to be replaced within 5-10 years of constmction
(LID, 2000).
Cost
Constriiction Cost
Constraction cost estimates for a bioretention area are sHghtiy greater than those for the
requfred landscaping for a new development (EPA, 1999). Ageneralrule ofthumb (Coffman,
1999) is that residential bioretention areas average about $3 to $4 per square foot, depending on
soil conditions and the density and types of plmts used. Commercial, industrial and
institutional site costs can range between $10 to $40 per square foot, based on fhe need for
contiol stmctures, curbing, storm drains and underdrains.
Retrofitting a site typicafly costs more, averaging $6,500 per bioretention area. The higher coste
are attributed to the demolition of existing concrete, asphalt, and existing stmctures and fhe
replacement of fiU material with planting sofl. The costs pf retiofitting a commercial site in
Maryland, Kettering Development, with 15 bioretention areas were estimated at $111,600.
hi my bioretention area design, the cost of plante varies substantially and can account for a
significant portion of the expenditures. V/hfle these cost estimates are sHghfly greater than
those of typical landscaping tieatment (due to the increased number of plantings, additional sofl
excavation, backffll material, use of underdrains etc.), those landscaping expenses that would be
requfred regardless of the bioretention installation should be subtiacted when determining the
net cost.
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Bioretention TC-32
P erhaps of most importance, however, tiie cost savings compared to the use of traditional
structural stormwater conveyance systems makes bioretention areas quite attractive finandafly.
For example, the use of bioretention can decrease flie cost required for constincting stormwater
conveyance systems at a site. A medical office buflding in Maryland was able to reduce the
amount of storm drain pipe that was needed from 800 to 230 feet - a cost savings of $24,000
(PGDER, 1993). And a new residential development spent a total of approxunately $100,000
using bioretention cefls on each lot instead of nearly $400,000 for tiie traditional stormwater
ponds that were originafly planned (Rappahanock,). Also, in residential areas, stormwater
management controls become a part of each property owner's landscape, reducing the public
burden to maintain large centiaHzedfacflities.
Maintenance Cost
The operation and maintenance coste for a bioretention facility wiU be comparable to those of
typical landscaping requfred for a site. Costs beyond fhe normal landscaping fees wfll indude
the cost for testing the soils and may include coste for a sand bed and planting sofl.
References and Sources of Additional Information
Coffman, L.S., R. Goo and R. Frederick, 1999: Low impact development an innovative
altemative approach to stormwater management. Proceedings, ofthe 26tii Annual Water
Resources Planning and Management Conference ASCE, June 6-9, Tempe, Arizona.
Davis, A.P., Shokouhian, M., Sharma, H. and Mfriami, C, "Laboratory Smdy of Biological
Retention (Bioretention) for Urban Stormwater Management," Wafer £7iwron Res 73(1) R-IA
(2001). ) / JW, o t
Davis, A.P., Shokouhian, M., Sharma, H., Mfriami, C, and Winogradoff, D. "Water Quality
Improvement tiirough Bioretention: Lead, Copper, and Zinc," Water Environ. Res., accepted for
publication, August 2002.
Kun, H., Seagren, E.A., and Davis, A.P., "Enghieered Bioretention for Removal of Nittate from
Stormwater Runoff," WEFTEC2000 Conference Proceedings on CDROM Research
Symposium, Nitrogen Removal, Session 19, Anahdm CA, October 2000.
Hsieh, C.-h. and Davis, A.P. "Engnieering Bioretention for Treatment of Urban Stormwater
Runoff," Watersheds 2002, Proceedings on CDROM Research Symposium, Session iq Ft
Lauderdale, FL, Feb. 2002. - ' '
Prince George's County Department of Envfromnental Resources (PGDER), 1993. Design
Manual for Use oi Bioretention in Stormwater Management. Division of Envfronmental
Management, Watershed Protection Branch, handover, MD.
U.S. EPA Office of Water, 1999. Stormwater Technology Fact Sheet Bioretention EPAB^'^-F-99-012.
Weinstein, N. Davis, A.P. and Veeramachaneni, R. "Low Impact Development (LID) Stormwater
Management Approach for the Contiol of Diffuse Poflution from Urban Roadways," 5th
Intemational Conference Diffuse/Nonpoint Pollution and Watershed Management
Proceedings, CS. Melching andEmre Alp, Eds. 2001 Intemational Water Assodation
January 2003 Califomia Stormwater BMP Handbook 7 of a
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TC-32 Bioretention
CURB STOPS-
TAKMNULOI yiLtl 1-LOW
bi^Jkaj E33ZE3
"SlUNtUIAPHkAUH
GRASS FILTER STRIP
OVERFLOW
'CATCH BASIN'
- OPTIONAL
SAND LAYER
UNDERDRAIN COLLECTION SYSTEM
• GRAVELCURTAIH
DRAIN OVERFLOW
PLAN VJEW
pCRAVEL
CURTAIN
DRAIN
-i lit
OH n ONAL SAND M
FILTER UYER ~
s" PONDING'
r-3" MULCH
.I'PliLMTIMff snii
Ml—
m
PIPE IN 8" GRAVEL
JACi-^ET
-FILTER FABRIC
TYPICAL SECTION
Schematic of a Bioretention Facility (MDE^. 2000)
-FROFttE-
Californla Stormwater BMP Handbook
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January 2003
Table 6-4 O&M Cost Estimate
Item Maintenance
Interval
Cost per
interval
Annual cost
estimate
Responsible
Party
Inlet stencils Annually $175.00 $175.00 Contractor/
Ovmer
Irrigation
Inspect irrigation *
Inspect plants *
Bi-monthly
Bi-monthly
$10
$10
$240.00
$240.00
Owner/HOA
Owner/HOA
Bioretention
Maintain landscaping Monthly $50.00 $360.00 Owner/HOA
*Note: These tasks are completed during routine landscape maintenance and account for 15% of
the estimated landscaping maintenance cost.