HomeMy WebLinkAboutEIR 05-05; PONTO BEACHFRONT VILLAGE VISION PLAN; Environmental Impact Report (EIR)(Final-Appendix Volume VII - Appendix H; 2007-08-01August 2007
Ponto 5eachfront Village
Vision Plan Final
Environmental Impact Report
Appendix Volume VII
(Appendices H through I)
SCH# 20070?1141
EIR 05-05/GPA 05-04/
LCPA 05-01/DI 05-01
Prepared for:
�w
Ci� of Carlsbad
Planning Department 16,5 Farada� Avenue
Carlsbad, California 92008
Contact: Christer Westman, Pr�ect Manager
(760)602-4614
Prepared 6�:
�
CONSULTING
9755 clairemont Mesa f>oulevard, Suite 100
San Diego, California 92124
(858)614-5000 -Fax (858) 614-5001
Rf>F JN 25-101951.001
PONTO BEACHFRONT VILLAGE VISION PLAN
FINAL
ENVIRONMENTAL IMPACT REPORT
SCH#2007031141 EIR 05-05/GPA 05-04/LCPA 05-01/DI 05-01
APPENDIX VOLUME VII
(APPENDICES H-1)
Prepared For:
City of Carlsbad Planning Department 1635 Faraday Avenue Carlsbad, California 92008
Contact: Christer Westman, Project Manager (760)602-4614
Prepared By:
RBF Consulting 9755 Clairemont Mesa Boulevard, Suite 100 San Diego, California 92124 (858)614-5000
FAX (858) 614-5001 RBF JN 25-101951.001
AUGUST 2007
Appendix H:
Appendix I:
APPENDIX VOLUME VII (APPENDICES H-1)
Geologic Hazards Analysis
Storm Water Mitigation Plan and Preliminary
Hydrology Study
APPENDIX H
Geologic Hazards Analysis
APPENDIX I
Storm Water Mitigation Plan and
Preliminary Hydrology Study
• \^^^0M:7hjm^im:^-7 7^;g^
^^^^^^^^^^^^^
Ponto Beachfront Village Vision Plan
Storm Water Mitigation Plan and
Preliminary Hydrology Study
October 30, 2006
Revised March 20, 2007
Prepared for:
CITY OF CARLSBAD
1635 FARADAY AVENUE
CARLSBAD, CA 92008
CONTACT: Christer Westmen, Planning Department
Prepared by:
CONSULTING
Contact Person:
Richard Lucera, P.E.
RBF JN 25-101951
RBF CONSULTING
5050 Avenida Encinas, Suite 260
Carlsbad, CA 92008
760.476.9193
Table of Contents
Storm Water Mitigation Plan
1 Storm Water Mitigation Plan Purpose and Scope 1
2 Project Information 1
2.1 Project Description 1
2.2 Project Activities 4
3 Water Quality Conditions of Concern 7
3.1 Potential Pollutants 7
3.1.1 Sediments 8
3.1.2 Nutrients 8
3.1.3 Heavy Metals 8
3.1.4 Organic Compounds 8
3.1.5 Trash and Debris 8
3.1.6 Oxygen Demanding Substances 9
3.1.7 Oil and Grease 9
3.1.8 Pesticides 9
3.1.9 Bacteria and Viruses 9
3.2 Pollutants of Concern 9
3.3 Conditions of Concern 10
4 Post Construction Best Management Practices 12
4.1 Site Design BMPs 12
4.1.1 Minimize Impervious Footprint and Directly Connected Impervious AreasIS
4.1.2 Landscape Design 13
4.1.3 Protect Slopes and Channels 13
4.2 Source Control BMPs 13
4.2.1 Efficient Landscape Design and Irrigation Practices 14
4.2.1.1 Common-Area Efficient Irrigation 14
4.2.1.2 Runoff-Minimizing Landscape Design 14
4.2.1.3 Landscape Maintenance 14
4.2.2 Material and Trash Storage Area Design 15
4.2.3 Pollution Prevention Outreach for Businesses 15
4.2.3.1 Source Reduction 15
4.2.3.2 Reuse/Recycling 16
4.2.3.3 Energy Recovery 16
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4.2.4 Storm Drain Stenciling and Signage 16
4.2.5 Rip Rap or Other Flow Energy Dissipators 16
4.3 BMPs for Individual Project Categories 16
4.4 Treatment Control BMPs 17
4.4.1 Treatment Control BMP Selection 18
4.4.1.1 Drainage Filter Inserts 19
4.4.1.2 Infiltration Basins 19
4.4.1.3 Vegetated Buffer Strip 19
4.5 Construction-Phase BMPs 20
5 Maintenance 20
Preliminary Hydrology Study
1 Introduction to Preliminary Hydrology Study 1
2 Project Information 1
2.1 Existing Conditions 1
2.2 Proposed Conditions 1
3 Analysis and Conclusion 2
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List of Tables
Table 2-1 Drainage Areas 4
Table 3-1 Anticipated and Potential Pollutants by Project Type (City of Carlsbad
SUSMP) 7
Table 3-2 Summary of 303(d) Impairments of Downstream Water Bodies 10
Table 4-1 Applicable BMPs (Carlsbad SUSMP) 12
Table 4-2 Site Design BMP Alternatives 13
Table 4-3 Source-control BMP alternatives 14
Table 4-4 Carlsbad SUSMP Individual Project Categories 17
Table 4-5 Treatment Control BMP Selection Matrix (City of Carlsbad SUSMP) 18
Table 4-6 Treatment-Control BMP Alternatives 18
Table 3-1 Summary of Site Flows 2
List of Figures
Figure 2.1-1 Ponto Beachfront Vision Plan Redevelopment Area 2
Figure 2.1-2 Existing Hydrologic Soils 3
Figure 2.2-1 Preliminary Land Use Exhibit 6
Figure 4.4-1 Kristar Floguard Plus® Inlet Insert 20
Technical Appendices
Appendix A Storm Water Standards Applicability Checklist
Appendix B Site Design BMPs
Appendix C Pre-Development Hydrology
Appendix D Post-Development Hydrology
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storm Water Mitigation Plan - Ponto Beachfront
Village Vision Plan
1 Storm Water Mitigation Plan Purpose and Scope
This report presents the water quality measures required for the Ponto Beachfront Village
Vision Plan (BWP), in order to fulfill the requirements of the City of Carlsbad. It also
describes the implementation and maintenance of water quality Best-Management Practices
(BMPs) that will be installed on the site.
2 Project Information
2.1 Project Description
The area proposed for development is located within the City of Carlsbad, between the San
Diego Northern Railroad and northbound Carlsbad Boulevard, and also straddling both sides
of Avenida Encinas. (See Figure 2-1) The development is bounded by Ponto Road to the
North, and Batiquitos Lagoon to the South. A realignment of Carlsbad Boulevard along the
project frontage is also anticipated in conjunction with site development of Ponto BWP.
The 50-acre future development site is mostly vacant, except for a cluster of single-family
residences, a few of which have small on-site businesses. The existing topography slopes
gently from an existing top of bank, adjacent to the rail lines towards Carlsbad Boulevard.
Sensitive habitats of disturbed coastal sage scrub and jurisdictional non-wetland waters have
been identified, with proposed development limited to the previously disturbed areas. Existing
soils consist mostly of marina loamy coarse sand (MIC) which has a Hydrologic Group "B"
rating. A small portion of the site consists of terrace escarpments (TeF) probably from
previous dredging of Batiquitos Lagoon. (See Figure 2-2 Existing Hydrologic Soils)
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Village Vision Plan
Project Vicinity
Ponto Beachfront Village
Rgure 2
Figure 2-1 Ponto Beachfront Vision Plan Redevelopment Area
The Ponto Beachfront Village Vision Plan Area is intended to be a pedestrian and bicycle
friendly mixed use area with up to three (3) hotels, town-homes at density of 15-23 dwelling
units per acre, live-work units, commercial uses, community facilities, and related parking
areas. Development of these uses will require General Plan and Local Coastal Program Land
Use Amendments.
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storm Water Mitigation Plan - Ponto Beachfront
Village Vision Plan
HYDROLOGIC GROUP RATING FOR SAN DIEGO COUmT AREA, CALIFORNIA
0 ISO 300 D KC 1,000 2,DDD 3,DDD 4.000
MHH Vu»CilllWB.!KirAC
W«b$MlSt=7WV].] 7
?s« 1 of 3
Figure 2-2 Existing Hydrologic Soils
MIC (Marina Loamy Course)
TeF (Terrace Escarpments)
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2.2 Project Activities
As stated above, the 50-acre future development will consist of several hotels, town-homes,
live-work units, commercial uses, community facilities, and related parking areas. Preliminary
site plans have not been prepared for each of these specific uses, however a Preliminary
Land Use Exhibit is included to illustrate relative size and location of each use. (See Figure
2-3)
The site will take roadway access from a four-way intersection at Ponto Drive and Avenida
Encinas as well as at one location along northbound Carlsbad Boulevard and one location
along Ponto Road adjacent to Hanover Beach Colony. Drainage from the site will be directed
to the low spot along Carlsbad Boulevard or towards Batiquitos Lagoon. Existing drainage
from the east (across the railroad) within an 84" diameter pipe is planned to bypass through
the site without commingling of flows from future development.
Table 2-1 Drainage Areas
Hotel Commercial 7.0 Acres
Hotel or Residential Apartments 3.5 Acres
Mixed Use Residential 6.6 Acres
Resort Hotel 13.7 Acres
Townhomes 6.8 Acres
Live/Work Mixed Use 1 0.9 Acres
LiveAA/ork Mixed Use 2 1.3 Acres
Total 39.8 Acres
Each of the areas listed in Table 2-1 are used to calculate the required storage for volume
based BMPs, such as extended detention basins, infiltration basins, bioretention areas, or wet
ponds, etc. There are approximately 10 acres within the project site that have not been
analyzed for the general magnitude of storage required for volume based BMPs. This area
includes the existing roads (approximately 6.0 acres) and a 4.1 acre linear park. The existing
roads are assumed to drain in separate systems with no "co-mingling" of flows with that from
the project. The linear park is assumed to incorporate some degree of parking, which will
require treatment. However, without a site plan or allocation as to the amount of parking
required, volume based calculations to estimate storage needs are impossible. Selection of
BMPs and the related supporting calculations for volume or flow based mitigation measures
will ultimately be the responsibility of the developer(s), since those included herein are solely
intended to demonstrate a basic order of magnitude to assist in land planning.
The City of Carlsbad has established a checklist to evaluate the need to incorporate Best
Management Practices (BMPs) for storm water treatment into the project design. The
checklist considers a combination of physical site characteristics and proposed development
to determine permanent and construction storm water BMP requirements. The checklist,
known as the Storm Water Applicability Checklist (included in Appendix A) establishes a
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Storm Water Mitigation Plan - Ponto Beachfront
Village Vision Plan
construction site priority (low, medium, or high) and determines the types of BMPs required for
the project. Because the project site is 50 acres or greater and its proximity to coastal waters,
the project is considered to be a high priority project. The project is subject to and will
incorporate the "Priority Project Permanent Storm Water Requirements" per the City's
SUSMP. These include the site design and source control BMPs, BMPs applicable to
individual priority project categories, and treatment control BMP requirements.
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Storm Water Mitigation Plan
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Ponto Beachfront Village Land Use Themes
Ponto Beachfront Village Vision Plan EIR
Figure 3-6
storm Water Mitioatlon Plan - Ponto
Beachfront Villaae Vision Plan
3 Water Quality Conditions of Concern
3.1 Potential Pollutants
The proposed project is not expected to generate significant amounts of pollutants, but
many constituents are generally anticipated for projects in this category
Table 3-1 Anticipated and Potential Pollutants by Project Type (City of Carlsbad
SUSMP)
ProjtBt
CMtgoritf StCiifTllfUs Nutrimis
HHvy Organic
Cotrpounds
Trash &
DtWs
Oxygen
OwnarWbtg
SiAstanots
OUA
Grtasc
BacMria &
Vmscs Pts«)ci<lts
DatachMl
RttWtndil
Divtlocmtnt
X X X X X X X
Attached
RtsMtntsi
Dtvakiprmnt
X X X poi pr, X
Conuntreial
Dflvdoprntnt
>100,OCOW
B') Pill PW X X P!» FWt
Rtpak X x<*> X X
RHtamnb X X X X
Hllsd*
Dtvalarmtnt
>5,0O0ll»
X X X X X X
ParicngLots po pn X X pi') X pti
SdMb.
FiMways
X Pi')» X X X
X 'ankipated
(1) A (Mtartial polUarrt If landscapn} cxisis on-stt.
(2) A iMMnfial poMant tw pR^cd Induies Mwovcreei pari^
(3) A pottntial pobtant land UM nvoh«s (CKMI or anlra^
4) InoMng pttrotcwn hythocaHxMts.
5) InoKning soKwits.
As indicated in Section 2.1, the project consists of several hotels, mixed use residential,
and associated parking lot area (See Figure 2-3 Preliminary Land Use Exhibit), thus
the project falls into the "attached residential", "commercial", "parking lot", and "streets,
highways and freeways" (because of internal access roads) priority project categories
indicated in Table 3-1. Potential pollutants of concern associated with these four priority
project categories include:
Sediments (since there will be landscaped areas on site);
Nutrients (since there will be landscaped areas on site);
Organic compounds;
Metals (associated with vehicle parking);
Litter and trash collecting in the drainage systems;
Oxygen-demanding substances including biodegradable organic material and
chemicals;
Oils, grease, and other hydrocarbons emanating from paved areas on the site;
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Pesticides used to control nuisance growth; and
Bacteria and Viruses
3.1.1 Sediments
Sediments are soils or other surface materials eroded and then transported or
deposited by the action of wind, water, ice, or gravity. Sediments can increase
turbidity, clog fish gills, reduce spawning habitat, lower young aquatic organisms
survival rates, smother bottom dwelling organisms, and suppress aquatic
vegetation growth.
3.1.2 Nutrients
Nutrients are inorganic substances, such as nitrogen and phosphorus. They
commonly exist in the form of mineral salts that are either dissolved or suspended
in water. Primary sources of nutrients in urban runoff are fertilizers and eroded
soils. Excessive discharge of nutrients to water bodies and streams can cause
excessive aquatic algae and plant growth. Such excessive production, referred to
as cultural eutrophication, may lead to excessive decay of organic matter in the
water body, loss of oxygen in the water, release of toxins in sediment, and the
eventual death of aquatic organisms.
3.1.3 Heavy Metals
Metals are raw material components in non-metal products such as fuels,
adhesives, paints, and other coatings. The primary sources of metal pollution in
storm water are typically commercially available metals and metal products. Metals
of concern include cadmium, chromium, copper, lead, mercury, and zinc. Lead and
chromium have been used as corrosion inhibitors in primer coatings and cooling
tower systems. At low concentrations naturally occurring in soil, metals are not
toxic. However, at higher concentrations, certain metals can be toxic to aquatic life.
Humans can be impacted from contaminated groundwater resources, and
bioaccumulation of metals in fish and shellfish. Environmental concerns, regarding
the potential for release of metals to the environment, have already led to
restricted metal usage in certain applications.
3.1.4 Organic Compounds
Organic compounds are carbon-based (commercially available or naturally
occurring) substances found in pesticides, solvents, and hydrocarbons. Organic
compounds can, at certain concentrations, indirectly or directly constitute a hazard
to life or health. When rinsing off objects, toxic levels of solvents and cleaning
compounds can be discharged to storm drains. Dirt, grease, and grime retained in
the cleaning fluid or rinse water may also adsorb levels of organic compounds that
are harmful or hazardous to aquatic life.
3.1.5 Trash and Debris
Trash (such as paper, plastic, polystyrene packing foam, and aluminum materials)
and biodegradable organic matter (such as leaves, grass cuttings, and food waste)
are general waste products on the landscape. The presence of trash 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
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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.
3.1.6 Oxygen Demanding Substances
This category includes biodegradable organic material as well as chemicals that
react with dissolved oxygen in water to forni other compounds. Proteins,
carbohydrates, and fats are examples of biodegradable organic compounds.
Compounds such as ammonia and hydrogen sulfide are examples of oxygen-
demanding compounds. The oxygen demand of a substance can lead to depletion
of dissolved oxygen in a water body and possibly the development of septic
conditions.
3.1.7 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 leaking vehicles, esters, oils, fats, waxes, and high molecular-weight
fatty acids. Introduction of these pollutants to the water bodies are very possible
due to the wide uses and applications of some of these products in municipal,
residential, commercial, industrial, and construction areas. Elevated oil and grease
content can decrease the aesthetic value of the water body, as well as the water
quality.
3.1.8 Pesticides
Pesticides (including herbicides) are chemical compounds commonly used to
control nuisance growth of organisms. Excessive application of a pesticide may
result in runoff containing toxic levels of its active component.
3.1.9 Bacteria and Viruses
Fecal bacteria are part of the intestinal flora of warm-blooded animals. Their
presence in surface waters is indicative of pollution. Total coliform measurements
typically include non-fecal coliform. Therefore additional testing is usually required
to confirm that percentage of total coliform, which has fecal contamination.
Coliform bacteria can be associated with land development uses that include food
handling, food waste, or animal waste.
3.2 Pollutants of Concem
The Environmental Protection Agency (EPA) is the primary federal agency responsible
for management of water quality in the United States. The Clean Water Act (CWA) is
the federal law that governs water quality control activities initiated by the EPA and
others. Section 303 of the CWA requires the adoption of water quality standards for all
surface water in the United States. Under Section 303(d), individual states are required
to develop lists of water bodies that do not meet water quality objectives after required
levels of treatment by point source dischargers. Total maximum daily loads (TMDLs) for
all pollutants for which these water bodies are listed must be developed in order to bring
them into compliance with water quality objectives.
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The project is located within the San Marcos hydrologic area of the Cartsbad hydrologic
unit. Receiving waters for the project site are the Batiquitos Lagoon and Pacific Ocean.
According to the California 2002 303(d) list published by the San Diego Regional Water
Quality Control Board (RWQCB Region 9), the project's receiving waters are impaired by
one (1) of the potential pollutants, bacteria. Batiquitos Lagoon does not have any 303d
impairments. Table 3-2 summarizes the receiving waters and their classification by the
RWQCB Region 9.
Table 3-2 Summary of 303(d) Impairments of Downstream Water Bodies.
Receiving Water
Hydrologic
Unit
Code
Approximate
Distance
From Site
303(d)
lmpairment(s)
Pacific Ocean Shoreline- San Marcos HA 904.50 0.1 mi Bacteria Indicators
3.3 Conditions of Concern
According to the City of Carlsbad SUSMP, a change to a priority prqject site's hydrologic
regime would be considered a condition of concern if the change would impact
downstream channels and habitat integrity. However, it is anticipated that site design
would include the necessary measures to effectively treat and detain/retain storm water
runoff to levels equal to or less than pre-development conditions. We conclude the
following:
> There will be no substantial change to existing drainage areas or increased
tendency for erosion, since the developer(s) will be required to provide detention
basins, energy dissipation measures, or other similarly acceptable hydraulic
equivalents (see attached Preliminary Hydrology Study).
> The City of Carlsbad has eliminated previous requirements to mitigate storm
water increases associated with land development within the coastal zone, since
there is no inherent benefit to detain storm water prior to direct discharge to the
ocean. However, recent modifications to the County of San Diego Municipal
Storm Sewer Discharge Permit require the City of Carisbad to develop a
hydromodification plan within the next 18 months. The developers of this project
will be subject to whatever requirements are ultimately included in this
forthcoming document. This may include, but not be limited to, mitigation to base
flow levels for increases in peak discharge during lower event design storms,
increases in discharge velocity, and/or duration. Therefore, it is reasonable to
assume at this point that some sort of detention will ultimately be required- if not
from the stand point of traditional flood control, but rather from the standpoint of
water quality. The stormwater detention volumes included within are solely for
the purpose of establishing a general order of magnitude to assist with land
planning, but verification will ultimately be the responsibility ofthe developer.
> Post development flow will not exceed capacity of downstream storm drain, since
the site is assumed to discharge to newly designed pipe and then directly to
Batiquitos Lagoon and the existing pedestrian under-cross at the low point in
Carisbad Boulevard, or, if possible, utilize on-site infiltration (or other similar
means) within the native soils. However, it shall be the responsibility of the
developer to design a storm drain system for the project that creates "erosional"
issues or subjects existing improvements to conditions beyond current hydraulic
capacity
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storm Water Mitiaation Plan - Ponto
Beachfront ViHaoe Vision Plan
Areas 9 and 22 of the City of Carisbad LFMP (Storm Drain Facilities Master Plan
of Improvements) coincide with the development area of the Ponto Beachfront
Village Vision Plan. The LFMP calls for realignment of existing 84" storm drain
pipe within these areas as well as construction of a temporary sediment basin. It
is unclear as to whether or not these improvements are based upon the
anticipated needs generated by the Ponto Beachfront Village Vision Plan.
However, it is reasonable to assume that these improvements can and will be
incorporated into forthcoming design efforts by the respective developers. If
these subsequent design efforts conclude that the need to construct these
improvements is no longer applicable or can be better accomplished by other
means, a revision to the City of Carisbad LMFP based upon the most current
concept of the Ponto Vision Plan would be warranted.
> The area does not propose any development within the 100-year floodplain or
Special Flood Hazard Area (SFHA) designated by FEMA.
> The project does not propose the construction«Df levees and/or dams, and is not
located behind a levee or below a dam that would present a flood hazard upon its
failure.
> It is our understanding that the risks of seiche, tsunami, and mudflow are
addressed in the geotechnical evaluation titled "Geologic Hazards Evaluation -
Proposed Ponto Beachfront Village. Prepared" by Kleinfelder, Inc. July 20, 2006.
These are not natural phenomena studied in traditional land development
hydrologic analysis.
> Post development flows will not contribute to a degradation of surface or
groundwater quality, since on-site areas will utilize the necessary BMPs (Best
Management Practices) to treat any contaminants associated with development.
Selection of specific BMPs and related engineering design shall be the
responsibility of the developer. However standards for sizing these facilities shall
be based upon that described in the CASQA (California Storm Water Quality
Association) manual for new construction. (Refer to Appendix B)
> The developer will be required to design site improvements to adhere to any
applicable forthcoming detention requirements associated with
hydromodification. This may involve provision for surface detention ponds, sub-
surface storage pipe, or other similariy acceptable hydraulic equivalent.
Preliminary calculations have been prepared to estimate a general order of
magnitude to assist with further land planning. Ultimate responsibility for analysis
and compliance with applicable hydromodification standards shall be the
responsibility of the developer. (Refer to Appendix C Pre-Development Hydrology
and Appendix D Post-Development Hydrology)
V
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4 Post Construction Best Management Practices
The project site incorporates four major types of post-construction best management
practices (BMPs). These types are (1) site design BMPs; (2) source control BMPs; (3)
site design and source control BMPs for individual priority project categories; and (4)
treatment control BMPs. In general, site design BMPs and source control BMPs reduce
the amount of storm water and potential pollutants emanating from a site and focus on
pollution prevention. Treatment-control BMPs target anticipated potential storm water
pollutants. The project will apply these BMPs to the maximum extent practicable.
Table 4-1 Applicable BMPs (Carlsbad SUSMP)
SOe
Design
Source
Controf
BMPsfl
auPi
Prim
iAppSea
nhrAoiei
Uetc linMnr
nesi*
Tmriment
BKPSM
SOe
Design
Source
Controf
BMPsfl
-8
8
ac
(t
•s
P
iJ
xi
i
3
ti
S. A
2 1
1 f
1
•
M
{
1
i
1
5
« 1
8 •1
£
1
1
•ml
CT
1
s
i Tmriment
BKPSM
Standard Projsds R R 0 0 0 0 0 0 0 0 0 0 0
Pnonty PRfiacti:
Detadied Residenfial
Devriovnient R R R R R S
Attached RtsidMiri R R R s
Camnad^ Dewlopmeiifi
>1OO.O0OtP R R R R R R s
Autaniolim nepar Shop R R R R R R R s
Rcsbiaanb R R R R s
Hiside Oewetopnient
>5.IX10IP R R R R s
Parking Lots R R RlH s
Streets, K|^iways&
FrecNays R R s
R = nttfmi; selact one or more appTicaUe aid ammjuiuib BM^s from the applicaWe steps In Section III.2 A-D, or
etuwalent as idunlilied 'wt i^ffmntx C.
0 = Q>lianal/arina]rbere<|uredb)rat)rs<aff. Asapprapnaile,afvliiarisareeiK)CHcagedtoiricc^^
BMPs and BMPs iVflicatte to iiMfiindicripnorilyprii^ia^^ C3ly staff may retire one or
mm of these BMF^ where appropriate.
S 3c Seled one cv riin aftpficaUe and appofm'ate li«atn«t oorM BMPs 1^
(1)RelariDSco6snlll.2A.
C2) Refer ioSe«icmill.2.B.
(3) P>k)rilypiofectcafeganesmietapp<yspecifKst^ PViorHypiG^edsare
std^ect to ttie tequnnients of al ptioiity piqecl lategoii^
(4) Re<ertoSeGionlll.2.D.
^) Applies if flK poind area totals >5,000 square lieet or w« >15 paikH^
4.1 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)
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has listed several site design BMPs that can be implemented in development projects.
The project has incorporated site design BMPs to the maximum extent practicable.
Error! Reference source not found, lists site-design BMP alternatives and indicates the
practices that have been applied to the project site.
Table 4-2 Site Design BMP Alternatives
n Buffer Zones n Open Space Design
• Narrower Residential Streets • "Green" Parking
• Alternative Turnarounds n Alternative Pavers
n Urban Forestry • Conservation Easements
• Eliminating Curbs And Gutters 13 Landscape Design
K Other (Explained Below) El Minimize Impervious Footprint
4.1.1 Minimize Impervious Footprint and Directly Connected Impervious Areas
The project will minimize the use of impervious surfaces in landscape design, such
as decorative concrete, in order to minimize impervious footprint on the site and
the amount of directly connected impervious surface. Where possible, building
roof drains, parking lots, and sidewalks will discharge to vegetated swales and
depressed areas, instead of directly to the storm drain collection system, to reduce
the amount of directly connected impervious surface. Partying lots will be
constructed to minimum widths and will drain to vegetated areas. Curbs have
been eliminated in various areas to allow sheet flow into Bio-Retention Areas.
4.1.2 Landscape Design
Site design will include several landscaped areas, through which site runoff can
be directed and filtered prior to discharge to in-tract storm drain pipe systems.
These landscaped areas are an effective method of pre treatment and will be
located upstream of on-site detention/retention basins.
4.1.3 Protect Slopes and Channels
Site runoff will be directed away from the tops of slopes, and all slopes will be
vegetated to provide permanent stabilization.
4.2 Source Control BMPs
Source-control BMPs are activities, practices, and procedures (primarily non-structural)
that are designed to prevent urban runoff pollution. These measures either reduce the
amount of runoff from the site or prevent contact between potential pollutants and storm
water. In addition, source-control BMPs are often the best method to address non-storm
(dry-weather) flows. Table 4-3 lists source-control BMP alternatives and indicates the
practices that will be applied at the project site.
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Beachfront Village Vision Plan
Table 4-3 Source-control BMP alternatives.
S Storm Drain Stenciling and Signage • Homeowner Outreach
13 Material and Trash Storage Area Design Q Lawn and Gardening Practices
El Efficient Irrigation Systems Q Water Conservation
13 Low-Irrigation Landscape Design Q Hazardous Waste Management
n On-Lot Treatment Measures Q Trash Management
D Riprap or Other Flow Energy Dissipation I3 Outreach for Commercial Activities
• Other (Explained Below)
4.2.1 Efficient Landscape Design and Irrigation Practices
Efficient landscape design and irrigation 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-
minimizing landscape design, and an effective landscape maintenance plan to the
maximum extent practicable.
4.2.1.1 Common-Area Efficient Irrigation
Automatic irrigation systems should include water sensors, programmable
irrigation timers, automatic valves to shut-off water in case of rapid pressure drop
(indicating possible water leaks), or other measures to ensure the efficient
application of water to the landscape and prevent unnecessary runoff from
irrigation. Drip irrigation and other low-water irrigation methods should be
considered where feasible. Common elements of efficient irrigation programs
include:
Reset irrigation controllers according to seasonal needs.
Do not over-water landscape plants or lawns.
Keep irrigation equipment in good working condition.
Promptly repair all water leaks.
4.2.1.2 Runoff-Minimizing Landscape Design
Landscape designs that group plants with similar water requirements can reduce
excess irrigation runoff and promote surface infiltration. Landscape designs
should utilize non-invasive native plant species and plants with low water
requirements when possible.
4.2.1.3 Landscape Maintenance
The landscape maintenance plan should include a regular sweeping program of
impervious surfaces, litter pick-up, and proper equipment maintenance
(preferably off-site), and proper use of chemicals to help eliminate sources of
storm water pollutants. Common elements of an effective landscape
maintenance plan include:
Implementing a regular program of sweeping sidewalks, driveways, and gutters
as part of the landscape maintenance plan. Pick-up litter frequently. Provide
convenient trash receptacles for public use if necessary.
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Storm Water Mitigation Plan
storm Water Mitigation Plan - Ponto
Beachfront Village Vision Plan
Avoid using water to clean sidewalks, driveways, and other areas.
Discourage washing of landscape maintenance equipment on-site. Minimize
water use and do not use soaps or chemicals. Use a commercial wash-rack
facility whenever possible.
Keep landscape maintenance equipment in good working order. Fix all leaks
promptly, and use drip pans/drip cloths when draining and replacing fluids.
Collect all spent fiuids and dispose of them properiy. Designate equipment
maintenance areas that are away from storm water inlets. Perform major
maintenance and repairs off-site if feasible.
Materials with the potential to pollute runoff (soil, pesticides, herbicides,
fertilizers, detergents, petroleum products, and other materials) should be
handled, delivered, applied, and disposed of with care following manufacturer's
labeled directions and in accordance with all applicable Federal, state, and local
regulations. Materials will be stored under cover or othenwise protected when
rain is forecast or during wet weather.
Pesticides and fertilizers, if used, will be applied according to manufacturer's
directions and will not be applied prior to a forecast rain event. Any material
broadcast onto paved surfaces (e.g. parking areas or sidewalks) will be promptly
swept up and properiy disposed.
4.2.2 Material and Trash Storage Area Design
There are no outdoor material storage areas associated with the proposed project.
Trash storage areas will be designed to contain stored material to prevent debris
from being distributed into storm water collection areas. For example, dumpsters
with lids will be kept in a separate enclosed area to prevent debris from being
scattered by wind or animals. The trash storage area will be paved with an
impervious surface such as concrete or asphalt concrete. In addition, the trash
storage area will be graded to prevent run-on from adjoining areas.
4.2.3 Pollution Prevention Outreach for Businesses
One source-control best management practice for commercial sites is pollution
prevention outreach. For instance, at the lease signing or as part of the lease, the
tenant can be presented with a brochure to encourage them to develop and
implement a pollution prevention program. The pollution prevention program
would emphasize source reduction, reuse and recycling, and energy recovery.
The following offer suggestions for measures to be included in these areas of
pollution prevention. The pollution prevention outreach should choose the
measures most applicable to the project site for the project site.
4.2.3.1 Source Reduction
Incorporating environmental considerations into the designing of products,
buildings, and manufacturing systems enables them to be more resource
efficient.
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Beachfront Village Vision Plan
Rethinking daily operations and maintenance activities can help industries
eliminate wasteful management practices that increase costs and cause
pollution.
Controlling the amount of water used in cleaning or manufacturing can produce
less wastewater.
Re-engineering and redesigning a facility or certain operation can take
advantage of newer, cleaner and more efficient process equipment.
Buying the correct amount of raw material will decrease the amount of excess
materials that are discarded (for example, paints that have a specified shelf life).
4.2.3.2 Reuse/Recycling
Using alternative materials for cleaning, coating, lubrication, and other production
processes can provide equivalent results while preventing costly hazardous
waste generation, air emissions, and worker health risks.
Using "green" products decreases the use of harmful or toxic chemicals (and are
more energy efficient than other products).
One company's waste may be another company's raw materials. Finding markets
for waste can reduce solid waste, lessen consumption of virgin resources,
increase income for sellers, and provide an economical resource supply for the
buyers.
4.2.3.3 Energy Recovery
Using energy, water, and other production inputs more efficiently keeps air and
water clean, reduces emissions of greenhouse gases, cuts operating costs, and
improves productivity.
4.2.4 Storm Drain Stenciling and Signage
Ali new storm drain grate inlets constructed as part of this project will be signed
with the message "No Dumping - Drains to Oceans" or equivalent message as
directed by the City.
4.2.5 Rip Rap or Other Flow Energy Dissipators
Rip rap or other suitable energy dissipators shall be placed, where applicable, at
the downstream end of storm drain outfalls or other location where sustained,
concentrated flows will have the capability of eroding natural soils.
4.3 BMPs for Individual Project Categories
The City of Carisbad SUSMP lists ten individual project categories for which BMPs must
be provided. Table 4-4 below lists these individual project categories and indicates that
the individual category of "Parking Areas" is applicable to the proposed project. Inlets
equipped with filter inserts treat any runoff generated and additional treatment is
provided as discussed in Section 4.4. Most parking areas will discharge to depressed
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Beachfront Village Vision Plan
vegetated areas, instead of directly to the storm drain collection system. Slopes will be
vegetated to provide permanent stabilization and to prevent erosion.
Table 4-4 Carlsbad SUSMP Individual Project Categories
• Private Roads
• Residential Driveways & Guest Parking
• Dock Areas
• Maintenance Bays
• Vehicle Wash Areas
• Outdoor Processing Areas
• Equipment Wash Areas
El Parking Areas
• Fueling Area
• Hillside Landscaping
4.4 Treatment Control BMPs
Post-construction "treatment control" storm water management BMPs provide treatment
for storm water emanating from the project site. Structural BMPs are an integral element
of post-construction storm water management and may include storage, filtration, and
infiltration practices. BMPs have varying degrees of effectiveness versus different
pollutants of concern. Table 4-5 summarizes which treatment control BMPs and
removal effectiveness for certain constituents.
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Table 4-5 Treatment Control BMP Selection Matrix (City of Carlsbad SUSMP)
PoAitant ofConem Tnaimtnt Contml BMP Categories
Bioilln Ddmlion
Basra
hSInvion
BasimCt
Wet Pon* or
Wetlands
Orainase
lns«ib
Fiilradcn Hydrodynamic
S«afa(orSvrtenB«
M H H H L H M
NiMfnti L M M M L M L
Hc9W Metds M M M H L H L
dvnoCaavoimds U U U U L M L
Tnsh&Oekris L H u U M H M
OxjfycnOemandhg
SiManocs L M M M L M L
Baotaiia U U H U L M L
Oa&Qrtast M M U U L H L
PeiriioMles U U U u L U L
(1) hNiudkig taidiis and pcfous pavement
(2) Mso knom as hydrodynarnie divioes and kafllc boias.
L IJOW Nraovai ettciency
M: McdunrtmovilelRciirtcy
H: H^^ rtnwual cBdtncy
U: LMcriawir«nKwalcfliai»icy
Sowees: Guidarwe Spcoiiiynq Mknagerntrtf Ik^^
ShamnlirB»ftUin»omtt«Prac6MuDMabast(^
4.4.1 Treatment Control BMP Selection
The selection, design and siting of structural BMPs within a project depend largely
on the project-wide drainage plan. BMP alternatives were evaluated for their
relative effectiveness for treating potential pollutants from the project site; technical
feasibility; relative costs and benefits; and applicable legal, institutional, and other
constraints. Table 4-6 below lists treatment-control BMP alternatives and
identifies the BMPs selected for the project site.
Table 4-6 Treatment-Control BMP Alternatives.
S Vegetated Swales and/or Strips • Wet Ponds/Wetlands
• Dry Extended Detention Basins S Infiltration Basins
• Bio-Retention Areas • Sand or Organic Filters
r~l Hydrodynamic Separators • Infiltration Trenches
S Catch Basin/Inlet Inserts • Other (Explained Below)
Several of the treatment control options available for this project are not feasible
based upon site conditions and constraints. Wet ponds and constructed
wetlands rely on a perennial water source, which is generally difficult to sustain in
the project's arid environment. While filtration devices, such as sand filters and
media filters, typically have medium to high removal efficiencies for the project's
pollutants of concern, they are aesthetically unsuitable for use in developments
such as this project. An underground sand/media filter might improve aesthetics,
but these are not recommended for drainage areas greater than 2 acres (2003
California New Development BMP Handbook, Fact Sheet TC-40), and the
proposed project covers 50 acres. Since the proposed project site will
presumably consist of generally flat graded pads, implementing several filters for
smaller drainage areas is not feasible due to the lack of required head needed to
ensure that water passes through the filter.
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Beachfront Village Vision Plan
The treatment controls which are both effective at removing the project pollutants
of concern and suitable for incorporation into the proposed project include
infiltration basins, vegetated strips, and drainage inlet inserts as described in the
following sections. The combination of these treatment controls in ali drainage
areas provides a multiple BMP approach to water quality treatment for runoff.
4.4.1.1 Drainage Filter Inserts
To provide initial treatment and removal of potential pollutants, drainage
inlet inserts will be installed in all storm drain inlets capturing runoff from
the parking lots. Kristar Floguard Plus® inserts or equivalent will be
specified to treat runoff for hydrocarbons and trash/debris. The Kristar
Floguard Plus® inlet insert is shown in Figure 4-1, and is similar in design
and function to other proprietary inlet inserts. Surface runoff enters the
inlet and passes over/through and adsorbent material to remove
hydrocarbons, while sediments and trash/debris are collected in the
hanging basket. Recommended maintenance consists of three
inspections per year (once before the wet season and two during, or more
as may be needed) plus replacement of the adsorbent when it is more
than 50% coated with pollutants and removal of excessive
sediment/debris. Each inlet insert costs about $570 and is available
locally through Downstream Sen/ices (760-746-2544 or 760-746-2667).
The inserts can be installed by Downstream Services for additional cost
or by the project construction contractor. Maintenance costs are
estimated at about $400 per year. (Detailed design calculations for these
inserts will be prepared when an initial site plan is available for review,
and preliminary on-site sub-watersheds can be delineated.)
4.4.1.2 Infiltration Basins
The infiltration basin areas function as a soil and landscaped-based
filtration device that removes pollutants through a variety of physical,
biological, and chemical treatment processes. These facilities normally
consist of a grassy bottom and native soils that promote moderately high
infiltration rates. The degree of treatment is a functional of overall volume
and dewatering time. When combined with additional flood control
storage volume they can also mitigate adverse impacts associated with
runoff volumes and rates. Cost ranges between $2 and $18 per cubic
foot of storage depending on other drainage facilities and improvements
associated with basin construction (Refer to TC-11 and the supporting
calculations in Appendix B).
4.4.1.3 Vegetated Buffer Strip
Grassed buffer strips within the landscaped areas are vegetated surfaces
that are designed to treat sheet flow from adjacent developed surfaces.
They function by slowing runoff and allowing sediment and other
pollutants to settle and by providing localized infiltration. Costs can range
between $0.30 to $0.70 per square foot. Design parameters vary as a
Ponto Beachfront Village Vision Plan: JN 25-101951 19
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storm Water Mitigation Plan • Ponto
Beachfront Village Vision Plan
function of flow rate; therefore, since a detailed site plan has not been
developed, detailed deign calculations have not been performed based
upon delineated sub -areas. However, a more detailed description of
how vegetated buffer strips are designed and implemented is found in
Appendix B.
Figure 4-1 Kristar Floguard Plus® inlet Insert
Initial Bypass
FouU Flock™ Pouches
SIDE VIEW
TOP VIEW
4.5 Construction-Phase BMPs
Additional best management practices to prevent reduce, and/or treat storm water
pollution will be implemented during the construction phase of the project. Because the
site is greater than 1 acre (as required by the NPDES General Permit) and because it is
considered a High Priority Construction Project by the City of Carisbad, a Storm Water
Pollution Prevention Plan (SWPPP) will be developed for the project site under separate
cover and will be incorporated by reference into this document.
5 Maintenance
To ensure long-term maintenance of project BMPs, the project proponent will enter into
J\ (j) agreement with the City of Carisbad to obligate the project proponent to maintain,
repair and replace the storm water BMPs as necessary in perpetuity.
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The site shall be kept in a neat and orderiy fashion with a regulariy scheduled landscape
maintenance crew in charge of keeping gutters and inlets free of litter and debris. The
landscape crew will also maintain the landscaping and vegetated strips to prevent
overgrowth and accumulation of litter or sediment.
The developer will select and design an appropriate series of treatment BMPs. For
example, the developer may select Kristar Floguard Plus® inlet inserts to be used in
series with extended detention basin(s). It is recommended that the hydrocarbon
absorption booms be replaced four times per year. Currently the approximate cost to
replace each boom is $100.00. This amounts to a maintenance cost of $400.00 per
year, per inlet. Extended detention basins will require routine periodic maintenance that
is required of any landscaped area, as well as regular cleanout of any substantial
accumulation of sediment/debris. It is reasonable to assume that maintenance of BMPs
would be at least several thousand dollars annually, and the developer should consider
this during the design phase. Additionally, repair of malfunctioning storm drain at the
inlet or outlet will be required on an as needed basis.
Maintenance records shall be retained for at least 5-years. These records shall be made
available to the City of Carisbad for inspection upon request.
Ponto Beachfront Village Vision Plan: JN 25-101951 21
Storm Water Mitigation Plan
1 Introduction to Preliminary Hydrology Study
The purpose of this study is to identify and propose remedial action for storm water flows
generated from the proposed re-development of the Ponto Vision Beachfront Village
Area. This report is to verify that the proposed drainage design will have no effect on the
direction of runoff and a negligible diversion of flow.
No options or exceptions have been taken for this study within the regulations of the San
Diego County.
No other hydrologic and hydraulic design criteria outside of the San Diego County (June
2003) are referenced for this study.
2 Project Information
2.1 Existing Conditions
The project is located within the City of Carisbad, between the San Diego Northern
Railroad and northbound Carisbad Boulevard, and also straddling both sides of Avenida
Encinas. (See Figure 2-1 Page 2 of the Storm Water Mitigation Plan)
The 50-acre future redevelopment site is mostly vacant, except for a cluster of single
family residences, a few of which have small on-site light industrial businesses. The
existing topography slopes gently from an existing top of bank, adjacent to the rail lines
towards Carisbad Boulevard. Sensitive habitats of disturbed coastal sage scrub and
jurisdictional non-wetland waters have been identified, with proposed development
limited to the previously disturbed areas. Existing soils consist mostly of marina loamy
coarse sand (MIC) which has a Hydrologic Group "B" rating. A small portion of the site
consists of terrace escarpments (TeF) probably from previous dredging of Batiquitos
Lagoon. (See Figure 2-2 on Page 3 ofthe Storm Water Mitigation Plan.)
2.2 Proposed Conditions
The Ponto Vision Redevelopment Area is intended to be a pedestrian and bicycle
friendly mixed use area with up to three (3) hotels, town-homes at density of 15-23
dwelling unites per acre, live-work units, commercial uses, community facilities, and
related parking areas. Development of these uses will require a number of General Plan
and Local Coastal Program Land Use Amendments. (Refer to Figure 2-3 Preliminary
Land Use Exhibit and Table 2-1 Drainage Areas of the Storm Water Mitigation Plan on
Pages 6 and 4, respectively)
The site will take roadway access from a four-way intersection at Ponto Drive and
Avenida Encinas as well as at one location along northbound Carisbad Boulevard and
one location along Ponto Drive adjacent to Hanover Beach Colony. It is assumed that
drainage from the site will be directed via new storm drainage system within the Ponto
BWP to the low spot along Carisbad Boulevard (near the existing pedestrian under
cross) or towards Batiquitos Lagoon. Existing drainage from the east (across the
railroad) within an 84" diameter pipe is planned to bypass through the site without
commingling of flows from future development.
3 Analysis and Conclusion
Runoff from the proposed development will increase as a result of additional impervious
area and construction of on-site pipe conveyance systems. However this increase can
be mitigated by expansion of infiltration basins used to treat water quality to the extent
necessary to control the increase in 100-year flows. The 100-year volumes can be
designed to accommodate infiltration of the entire post development flow (effectively
eliminating overiand discharge) or to simply reduce site discharge to pre-development
levels. This determination will be made during site design as a function of more detailed
geotechnical recommendations and the availability of space within the site layout. The
results are summarized below. Preliminary backup calculations to substantiate water
quality and flood control basin sizing can be found in Appendix B, while corresponding
watershed maps can be found in Appendix C and Appendix D. Since preliminary site
plans have not been developed, we anticipate that this hydrology analysis will require
further development prior to final design. However, we believe that the conclusions and
preliminary data enclosed within are conservative based upon the most current
information related to development.
Table 3-1 Summary of Site Flows
j
Site
L. ... .
^rea
(acres^
Pre
Development
Q (cfs)
Posf
Development Q
without
Mitigation (cfs)
i
Posf
Development
with Detention
of 100 Year Q to
Pre
Development
(cfs)
Hotel
Commercial 7.0 8.3 38.5 8.3
Hotel or
Residential
Apts
3.5 4.4 18.9 4.4
Mixed Use
Residential 6.6 6.0 34.4 6.0
Resort Hotel 13.7 14.0 74.0 14.0
Townhomes 6.8 6.1 34.5 6.1
Live/Work
Mixed Use 1
0.9 1.2 4.9 1.2
Live/Work
Mixed Use 2
1.3 1.7 7.0 1.7
Total 39.8
Areas 9 and 22 of the City of Carisbad LFMP (Storm Drain Facilities Master Plan of
Improvements) coincide with the development area ofthe Ponto Beachfront Village Plan.
The LFMP calls for realignment of existing 84" storm drain pipe within these areas as
well as construction of a temporary sediment basin. It is unclear as to whether or not
these improvements are based upon the anticipated needs generated by the Ponto
Beachfront Vision Plan. However, it is reasonable to assume that these improvements
can and will be incorporated into forthcoming design efforts by the respective
developers. If these subsequent design efforts conclude that the need to construct
these improvements is no longer applicable or can be better accomplished by other
means, a revision to the City of Carisbad LMFP based upon the most current concept of
the Ponto Vision Plan would be warranted.
Appendix A Storm Water Standards Applicability Checklist
51
STDRw WATER RiEduiftEflWBNTS AF^I
Project Address _ , ^ Assessors Parcel Numbers): Project # (city use only):
Complete Sections 1 and 2 of the following checklist to determine your project's permanent and
construction storm water best management practices requirements. This form must be completed
and submitted with your permit application.
Section 1. Permanent Storm Water BMP Requirements:
If any answers to Part A are answered "Yes," your project is subject to the "Priority Project
Permanent Storm Water BMP Requirements," and "Standard Permanent Storm Water BMP
Requirements" in Section 111, "Permanent Storm Water BMP Selection Procedure" in the Storm
Water Standards manual.
If all answers to Part A are "No," and any answers to Part B are "Yes," your project is only subject
to the "Standard Permanent Storm Water BMP Requirements". If every question in Part A and B
is answered "No," your project is exempt from permanent storm water requirements.
Does the project meet the definition of one or more of the priority project categories?* Yes No
1. Detached residential development of 10 or more units. •
2. Attached residential development of 10 or more units. •
3. Commercial development greater than 100,000 square feet. m •
4. Automotive repair shop.
5. Restaurant.
6. Steep hillside development greater than 5,000 square feet. •
7. Project discharging to receiving waters within Environmentally Sensitive Areas.
8. Parking lots greater than or equal to 5,000 ft or with at least 15 parking spaces, and
potentially exposed to urban runoff.
9. Streets, roads, highways, and freeways which would create a new paved surface that is
5,000 square feet or greater
* Refer to the definitions section in the Storm Water Standards for expanded definitions of the
priority project categories.
Limited Exclusion: Trenching and resurfacing work associated with utility projects are not
considered priority projects. Parking lots, buildings and other structures associated with utility
projects are priority projects if one or more of the criteria in Part A is met. If all answers to Part A
are "No", continue to Part B.
Part B: Determine Standard Permanent Storm Water Requirements.
Does the project propose: Yes No
1. New impen/ious areas, such as rooftops, roads, parking lots, driveways, paths and
sidewalks? m 2. New pervious landscape areas and irrigation systems?
3. Permanent structures within 100 feet of any natural water body?
4. Trash storage areas? •
5. Liquid or solid material loading and unloading areas? •
6. Vehicle or equipment fueling, washing, or maintenance areas?
7. Require a General NPDES Permit for Storm Water Discharges Associated with Industrial
Activities (Except construction)?*
8. Commercial or industrial waste handling or storage, excluding typical office or household
waste?
9. Any grading or ground disturbance during construction? •
10. Any new storm drains, or alteration to existing storm drains?
*To find out if your project is required to obtain an individual General NPDES Permit for Storm Water
Discharges Associated with Industrial Activities, visit the State Water Resources Control Board web site
at, www.swrcb.ca.gov/stormwtr/industrial.html
Section 2. Construction Storm Water BMP Requirements:
If the answer to question 1 of Part C is answered "Yes," your project is subject to Section IV, "Construction
Storm Water BMP Performance Standards," and must prepare a Storm Water Pollution Prevention Plan
(SWPPP). If the answer to question 1 is "No," but the answer to any of the remaining questions is "Yes,"
your project is subject to Section IV, "Construction Storm Water BMP Performance Standards," and must
prepare a Water Pollution Control Plan (WPCP). If every question in Part C is answered "No," your project
is exempt from any construction storm water BMP requirements. If any of the answers to the questions in
Part C are "Yes," complete the construction site prioritization in Part D, below.
Part C: Determine Construction Phase Storm Water Requirements.
Would the project meet any of these criteria during construction? Yes No
1. Is the project subject to California's statewide General NPDES Permit for Storm Water
Discharges Associated With Construction Activities?
2. Does the project propose grading or soil disturbance?
3. Would storm water or urban runoff have the potential to contact any portion of the
construction area, including washing and staging areas? n 4. Would the project use any construction materials that could negatively affect water quality
if discharged from the site (such as, paints, solvents, concrete, and stucco)?
Part D: Determine Construction Site Priority
In accordance with the Municipal Permit, each construction site with construction storm water BMP
requirements must be designated with a priority: high, medium or low. This prioritization must be
completed with this form, noted on the plans, and included in the SWPPP or WPCP. Indicate the project's
priority in one of the check boxes using the criteria below, and existing and surrounding conditions of the
project, the type of activities necessary to complete the construction and any other extenuating
circumstances that may pose a threat to water quality. The City reserves the right to adjust the priority of
the projects both before and during construction. [Note: The constmction priority does NOT change
construction BMP requirements that apply to projects; all construction BMP requirements must be
identified on a case-by-case basis. The construction priority does affect the frequency of inspections that
will be conducted by City staff. See Section IV.1 for more details on construction BMP requirements.]
A) High Priority
1) Projects where the site is 50 acres or more and grading will occur during the rainy season
2) Projects 1 acre or more.
3) Projects 1 acre or more within or directly adjacent to or discharging directly to a coastal lagoon or
other receiving water within an environmentally sensitive area
4) Projects, active or inactive, adjacent or tributary to sensitive water bodies
I |B; Medium Priority
5) Capital Improvement Projects where grading occurs, however a Storm Water Pollution Prevention
Plan (SWPPP) is not required under the State General Construction Permit (i.e., water and sewer
replacement projects, intersection and street re-alignments, widening, comfort stations, etc.)
6) Permit projects in the public right-of-way where grading occurs, such as installation of sidewalk,
substantial retaining walls, curb and gutter for an entire street frontage, etc. , however SWPPPs are
not required.
7) Permit projects on private property where grading permits are required, however. Notice Of Intents
(NOIs) and SWPPPs are not required.
I \C) Low Priority
8) Capital Projects where minimal to no grading occurs, such as signal light and loop installations,
street light installations, etc.
9) Permit projects in the public right-of-way where minimal to no grading occurs, such as pedestrian
ramps, driveway additions, small retaining walls, etc.
10) Permit projects on private property where grading permits are not required, such as small retaining
walls, single-family homes, small tenant improvements, etc.
Owner/Agent/Engineer Name (Please Print): Title:
Signature: iO. / / -/
t^^/pc*^^^
Date: f /
Storm Water Standards
4/03/03
DRAFT
ENVIRONMENTALLY SENSITIVE AREAS WITHIN THE CITY OF CARLSBAD
Environmentally
Sensitive Areas
/\/ Major Roads
Carlsbad City Boundary
I Environmentally Sensitive Areas
e 5.800 Z9Q0 0
i Jcargi32/products/plannln9/r312,02/EnvSensArea5
34
Appendix B Site Design BMPs
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SHEETNO. OF
CONSULTING
PLANNING • DESIGN • CaNSTRUCTION
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RATIONAL METHOD HYDROGRAPH PROGRAM
^OPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
•RUN DATE 10/17/2006
HYDROGRAPH FILE NAME Textl
TIME OF CONCENTRATION 12 MIN.
•B HOUR RAINFALL 2.5 INCHES
MASIN AREA 7 ACRES
RUNOFF COEFFICIENT 0.32
PEAK DISCHARGE 8.3 CFS •TIME •TIME
TIME
TIME
•"IME
VIME
n"IME
TIME
(IME
IME
IME
TIME
J"IME
•~IME
•"IME
TIME
TIME
VIME
•"IME
^IME
TIME
^IME
VIME
•"IME
TIME
TIME
•"IME
VIME
"IME
TIME
IIME
IME
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
0
12
24
36
48
60
72
84
96
108
120
132
144
156
168
180
192
204
216
228
240
252
264
276
288
300
312
324
336
348
360
372
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS):
(CFS) =
(CFS):
(CFS) ••
(CFS):
(CFS):
(CFS):
(CFS) :
(CFS) :
(CFS) ••
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS) :
(CFS):
0
0.3
0.4
0.4
0.4
0.4
0.5
0.5
0.5
0.6
0.7
0.7
0.9
1.1
1.7
8.3
2.4
1.3
1
0.8
0.7
0.6
0.6
0.5
0.5
0.4
0.4
0.4
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RATIONAL METHOD HYDROGRAPH PROGRAM
^OPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
BRUNDATE 10/17/2006
HYDROGRAPH FILE NAME Textl
TIME OF CONCENTRATION 5 MIN.
B HOUR RAINFALL 2.5 INCHES
ftASIN AREA 7 ACRES
RUNOFF COEFFICIENT 0.82
PEAK DISCHARGE 38.5 CFS
f lME
IME
TIME
TIME
•"IME
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TIME
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TIME
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TIME
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~IME
TIME
f lME
IME
IME
TIME
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TIME
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^IME
TIME
^IME •IME •iME TIME TIME IIME IME
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
325
330
335
340
345
350
355
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
DISCHARGE
(CFS):
(CFS) ••
(CFS) ••
(CFS) ••
(CFS):
(CFS) =
(CFS) ••
(CFS) ••
(CFS) ••
(CFS) ••
(CFS) =
(CFS):
(CFS) ••
(CFS) ••
(CFS):
(CFS) ••
(CFS):
(CFS) ••
(CFS):
(CFS) ••
(CFS) ••
(CFS):
(CFS):
(CFS) ••
(CFS) ••
(CFS):
(CFS) ••
(CFS) ••
(CFS) ••
(CFS) ••
(CFS):
(CFS) ••
(CFS) ••
(CFS):
(CFS) ••
(CFS):
(CFS):
(CFS) ••
(CFS) ••
(CFS):
(CFS):
(CFS):
(CFS) ••
(CFS):
(CFS) ••
(CFS) ••
(CFS) =
(CFS) =
(CFS) ••
(CFS) =
(CFS) ••
(CFS) ••
(CFS) =
(CFS) =
(CFS):
(CFS)=
(CFS):
(CFS) ••
(CFS) =
(CFS) ••
(CFS) ••
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS) =
(CFS):
(CFS) =
(CFS)=
(CFS)=
(CFS) ••
0
0.9
0.9
0.9
0.9
0.9
1
1
1
1
1
1.1
1.1
1.1
1.2
1.2
1.2
1.3
1.3
1.4
1.4
1.5
1.5
1.6
1.7
1.8
1.9
2
2.2
2.4
2.6
2.9
3.4
4
5.1
7.5
38.5
9.9
6
4.5
3.7
3.1
2.8
2.5
2.3
2.1
2
1.9
1.8
1.7
1.6
1.5
1.5
1.4
1.3
1.3
1.3
1.2
1.2
1.1
1.1
1.1
1.1
1
1
1
1
0.9
0.9
0.9
0.9
0.9
TIME (MIN) = 360 DISCHARGE (CFS) = 0.9
TIME (MIN) = 365 DISCHARGE (CFS) = 0
CONSULTING
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RATIONAL METHOD HYDROGRAPH PROGRAM
COPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
[RUN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
TIME OF CONCENTRATION 11 MIN.
HOUR RAINFALL 2.5 INCHES
lASIN AREA 3.5 ACRES
UNOFF COEFFICIENT 0.32
PEAK DISCHARGE 4.4 CFS
tIME
IME
TIME
TIME •TIME •TIME
^IME
TIME
•TIME
•TIME
•TIME
TIME
_TIME •TIME •TIME
TIME
TIME
•"IME •IME
^IME
TIME
KIME
IME
IME
TIME
J"IME
•IME •iME n"IME TIME TIME riME TIME TIME •|ME
(MIN
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(MIN
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(MIN
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(MIN
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(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
0 DISCHARGE (CFS
11 DISCHARGE (CFS
22 DISCHARGE (CFS
33 DISCHARGE (CFS
44 DISCHARGE (CFS
55 DISCHARGE (CFS
66 DISCHARGE (CFS
77 DISCHARGE (CFS
88 DISCHARGE (CFS
99 DISCHARGE (CFS
110 DISCHARGE (CFS
121 DISCHARGE (CFS
132 DISCHARGE (CFS
143 DISCHARGE (CFS
154 DISCHARGE (CFS
165 DISCHARGE (CFS
176 DISCHARGE (CFS
187 DISCHARGE (CFS
198 DISCHARGE (CFS
209 DISCHARGE (CFS
220 DISCHARGE (CFS
231 DISCHARGE (CFS
242 DISCHARGE (CFS
253 DISCHARGE (CFS
264 DISCHARGE (CFS
275 DISCHARGE (CFS
286 DISCHARGE (CFS
297 DISCHARGE (CFS
308 DISCHARGE (CFS
319 DISCHARGE (CFS
330 DISCHARGE (CFS
341 DISCHARGE (CFS
352 DISCHARGE (CFS
363 DISCHARGE (CFS
374 DISCHARGE (CFS
0
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.3
0.4
0.5
0.6
0.9
4.4
1.3
0.7
0.5
0.4
0.4
0.3
0.3
0.3
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0
P
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RATIONAL METHOD HYDROGRAPH PROGRAM
COPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
RUN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
TIME OF CONCENTRATION 5 MIN.
6 HOUR RAINFALL 2.5 INCHES
BASIN AREA 3.5 ACRES
RUNOFF COEFFICIENT 0.82
PEAK DISCHARGE 18.9
ITIME
TIME
TIME
ITIME
TIME
TIME
TIME
TIME •TIME •TIME •TIME
TIME
_TIME •TIME •TIME
TIME
TIME •TIME •TIME
"TIME
TIME
EIME
IME
IME
TIME
—TIME
•TIME
priME
TIME
TIME •TIME •TIME •TIME
TIME
HTIME •TIME •IME
TIME
TIME •TIME •iME
"TIME
TIME
KIME
IME
IME
TIME
jriME •iME •IME TIME TIME VIME •IME %IME TIME f lME IME IME TIME TIME •IME •iME ^IME TIME IIME IME IME TIME J"IME •IME I'IME
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
: 0
= 5
= 10
: 15
= 20
= 25
= 30
= 35
= 40
= 45
= 50
= 55
: 60
= 65
= 70
= 75
: 80
= 85
= 90
= 95
: 100
: 105
•• 110
• 115
•• 120
: 125
•• 130
•• 135
•• 140
• 145
•• 150
' 155
• 160
165
•• 170
175
•• 180
185
190
195
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
325
330
335
340
345
350
355
CFS
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 1.3
DISCHARGE (CFS) = 1.5
DISCHARGE (CFS) = 1.7
DISCHARGE (CFS) = 2
DISCHARGE (CFS) = 2.5
DISCHARGE (CFS) = 3.7
DISCHARGE (CFS) = 18.9
DISCHARGE (CFS) = 5.3
DISCHARGE (CFS) = 3
DISCHARGE (CFS) = 2.2
DISCHARGE (CFS) = 1.8
DISCHARGE (CFS) = 1.6
DISCHARGE (CFS) = 1.4
DISCHARGE (CFS) = 1.3
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
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iPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY I JNDATE 10/19/2006
HYDROGRAPH FILE NAME Textl
^ME OF CONCENTRATION 13 MIN.
•HOUR RAINFALL 2.5 INCHES
•SIN AREA 6.6 ACRES
RUNOFF COEFFICIENT 0.25
PEAK DISCHARGE 6 CFS •ME ™E
TIME I
fiiMEl •ME •ME TIME I
JlMEi
•MEI
•VIE I
TTME
TIME
EE
E
E
TIME
J^Ei •VIE •VIE
TIME I
TIME •VIE
•VIE I
TTME
TIME I
KEi
E
E
TIME
TIME I
(MIN) = 0 DISCHARGE (CFS) = 0
(MIN) = 13 DISCHARGE (CFS) = 0.3
(MIN) = 26 DISCHARGE (CFS) = 0.3
(MIN) 39 DISCHARGE (CFS) = 0.3
(MIN) = 52 DISCHARGE (CFS) = 0.3
(MIN) = 65 DISCHARGE (CFS) = 0.3
(MIN) = 78 DISCHARGE (CFS) = 0.3
(MIN) = 91 DISCHARGE (CFS) = 0.4
(MIN) = 104 DISCHARGE (CFS) = 0.4
(MIN) = 117 DISCHARGE (CFS) = 0.5
(MIN) = 130 DISCHARGE (CFS) = 0.5
(MIN) = 143 DISCHARGE (CFS) = 0.6
(MIN) = 156 DISCHARGE (CFS) = 0.8
(MIN) = 169 DISCHARGE (CFS) = 1.2
(MIN) = 182 DISCHARGE (CFS) = 6
(MIN) = 195 DISCHARGE (CFS) = 1.5
(MIN) = 208 DISCHARGE (CFS) = 0.9
(MIN) = 221 DISCHARGE (CFS) = 0.7
(MIN) = 234 DISCHARGE (CFS) = 0.6
(MIN) = 247 DISCHARGE (CFS) = 0.5
MIN) = 260 DISCHARGE (CFS) = 0.4
(MIN) = 273 DISCHARGE (CFS) = 0.4
MIN) -286 DISCHARGE (CFS) = 0.4
MIN) = 299 DISCHARGE (CFS) = 0.3
MIN) = 312 DISCHARGE (CFS) = 0.3
MIN) = 325 DISCHARGE (CFS) = 0.3
MIN) = 338 DISCHARGE (CFS) = 0.3
MIN) = 351 DISCHARGE (CFS) = 0.3
MIN) 364 DISCHARGE (CFS) = 0.2
MIN) = 377 DISCHARGE (CFS) = 0
?ri^y,^D USE Rr.3xo,--ri^L
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f ' TIONAL METHOD HYDROGRAPH PROGRAM
PYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
RUN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
(IME OF CONCENTRATION 5 MIN.
HOUR RAINFALL 2.5 INCHES
ASINAREA 6.6 ACRES
RUNOFF COEFFICIENT 0.79
•EAK DISCHARGE 34.4 CFS
IME
TIME
(IME
ME
ME
IME
TIME
IME
ME
ME
TIME
IME
ME
ME
TIME
TIME
|ME •ME ™E
TIME
IME
ME
ME
TIME
IME
ME
ME
ME
TIME
IME
ME
ME
TIME
JJME •ME •ME
TIME
TIME
•ME •ME ™E
TIME IME
ME
ME
TIME
TIME •ME •ME
"ME
TIME
IME
ME
ME
TIME
IME
ME
ME
ME
TIME
IME
ME
ME
TIME
IME
ME
ME
TIME
TIME •ME •ME
^ME
MIN) = 0 DISCHARGE (CFS) = 0
MIN) = 5 DISCHARGE (CFS) = 0.8
MIN) = 10 DISCHARGE (CFS) = 0.8
MIN) = 15 DISCHARGE (CFS) = 0.8
MIN) = 20 DISCHARGE (CFS) = 0.8
MIN) = 25 DISCHARGE (CFS) = 0.8
MIN) = 30 DISCHARGE (CFS) = 0.9
[MIN) = 35 DISCHARGE (CFS) = 0.9
(MIN) = 40 DISCHARGE (CFS) = 0.9
MIN) = 45 DISCHARGE (CFS) = 0.9
MIN) = 50 DISCHARGE (CFS) = 0.9
(MIN) = 55 DISCHARGE (CFS) = 1
MIN) = 60 DISCHARGE (CFS) = 1
MIN) = 65 DISCHARGE (CFS) = 1
MIN) = 70 DISCHARGE (CFS) = 1.1
MIN) = 75 DISCHARGE (CFS) = 1.1
MIN) = 80 DISCHARGE (CFS) = 1.1
MIN) = 85 DISCHARGE (CFS) = 1.2
MIN) = 90 DISCHARGE (CFS) = 1.2
MIN) = 95 DISCHARGE (CFS) = 1.2
MIN) = 100 DISCHARGE (CFS) = 1.3
MIN) = 105 DISCHARGE (CFS) 1.3
MIN) = 110 DISCHARGE (CFS) = 1.4
MIN) = 115 DISCHARGE (CFS) = 1.5
MIN) = 120 DISCHARGE (CFS) = 1.5
MIN) = 125 DISCHARGE (CFS) = 1.6
MIN) = 130 DISCHARGE (CFS) 1.7
MIN) = 135 DISCHARGE (CFS) = 1.9
MIN) = 140 DISCHARGE (CFS) = 2
MIN) = 145 DISCHARGE (CFS) = 2.2
MIN) = 150 DISCHARGE (CFS) 2.4
MIN) = 155 DISCHARGE (CFS) = 2.7
MIN) = 160 DISCHARGE (CFS) = 3.1
(MIN) = 165 DISCHARGE (CFS) = 3.6
MIN) = 170 DISCHARGE (CFS) = 4.6
MIN) = 175 DISCHARGE (CFS) = 6.8
MIN) = 180 DISCHARGE (CFS) = 34.4
MIN) = 185 DISCHARGE (CFS) = 9.5
MIN) = 190 DISCHARGE (CFS) = 5.5
MIN) = 195 DISCHARGE (CFS) = 4.1
MIN) = 200 DISCHARGE (CFS) = 3.3
MIN) = 205 DISCHARGE (CFS) = 2.9
MIN) = 210 DISCHARGE (CFS) = 2.5
MIN) = 215 DISCHARGE (CFS) = 2.3
MIN) = 220 DISCHARGE (CFS) = 2.1
MIN) = 225 DISCHARGE (CFS) = 1.9
MIN) = 230 DISCHARGE (CFS) = 1.8
MIN) = 235 DISCHARGE (CFS) = 1.7
MIN) = 240 DISCHARGE (CFS) = 1.6
MIN) = 245 DISCHARGE (CFS) = 1.5
MIN) = 250 DISCHARGE (CFS) = 1.4
MIN) = 255 DISCHARGE (CFS) = 1.4
MIN) = 260 DISCHARGE (CFS) = 1.3
MIN) = 265 DISCHARGE (CFS) = 1.3
MIN) = 270 DISCHARGE (CFS) = 1.2
MIN) = 275 DISCHARGE (CFS) = 1.2
MIN) = 280 DISCHARGE (CFS) = 1.1
MIN) = 285 DISCHARGE (CFS) = 1.1
MIN) = 290 DISCHARGE (CFS) = 1.1
MIN) = 295 DISCHARGE (CFS) = 1
MIN) = 300 DISCHARGE (CFS) = 1
MIN) = 305 DISCHARGE (CFS) = 1
MIN) = 310 DISCHARGE (CFS) = 1
MIN) = 315 DISCHARGE (CFS) = 0.9
MIN) = 320 DISCHARGE (CFS) = 0.9
MIN) = 325 DISCHARGE (CFS) = 0.9
MIN) = 330 DISCHARGE (CFS) = 0.9
MIN) = 335 DISCHARGE (CFS) = 0.9
MIN) = 340 DISCHARGE (CFS) = 0.8
MIN) = 345 DISCHARGE (CFS) = 0.8
MIN) = 350 DISCHARGE (CFS) = 0.8
MIN) = 355 DISCHARGE (CFS) = 0.8
t/re K E^JJDE'^'Tr^i-
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POST-C0^JSTRUCTI0^J
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n- 9 .0 MINUIES
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DETETfTION VOLUME - 0.74 AC-FT
Q (cys) T - IBO MINUTES
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Q = 6.0 CFS
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T (MUJUTES)
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RATIONAL METHOD HYDROGRAPH PROGRAM
;OPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
WNDATE 10/17/2006
HYDROGRAPH FILE NAME Textl
(IME OF CONCENTRATION 10 MIN.
HOUR RAINFALL 2.5 INCHES
ASINAREA 13.7 ACRES
RUNOFF COEFFICIENT 0.25
PEAK DISCHARGE 14 CFS
•IME
"IME
TIME
8IME (
IME
IME
TIME
JIME
•iMEl
•iMEi
TIME I
TIME I
•IME
•IME
^MEi
TIME I
^ME •ME •ME
TIME I
TIME I IMEl
ME I
ME
TIME I
IME
ME
ME
TIME «ME|
MEi
ME I
ME
TIME
IMEl
ME
ME
TIME I
(MIN = 0 DISCHARGE (CFS) = 0
(MIN = 10 DISCHARGE (CFS) = 0.5
(MIN = 20 DISCHARGE (CFS) = 0.5
(MIN = 30 DISCHARGE (CFS) = 0.6
(MIN) = 40 DISCHARGE (CFS) = 0.6
(MIN) = 50 DISCHARGE (CFS) = 0.6
(MIN) = 60 DISCHARGE (CFS) = 0.7
(MIN) = 70 DISCHARGE (CFS) = 0.7
(MIN) = 80 DISCHARGE (CFS) = 0.7
(MIN) = 90 DISCHARGE (CFS) = 0.8
(MIN) = 100 DISCHARGE (CFS) = 0.8
(MIN) -110 DISCHARGE (CFS) = 0.9
(MIN) = 120 DISCHARGE (CFS) = 1
(MIN) = 130 DISCHARGE (CFS) = 1.1
(MIN) = 140 DISCHARGE (CFS) = 1.3
(MIN) = 150 DISCHARGE (CFS) = 1.5
(MIN) = 160 DISCHARGE (CFS) = 1.9
(MIN) = 170 DISCHARGE (CFS) = 2.9
(MIN) = 180 DISCHARGE (CFS) = 14
(MIN) -190 DISCHARGE (CFS) = 4.5
(MIN) = 200 DISCHARGE (CFS) = 2.3
(MIN) = 210 DISCHARGE (CFS) = 1.7
(MIN) 220 DISCHARGE (CFS) = 1.4
(MIN) = 230 DISCHARGE (CFS) = 1.2
(MIN) = 240 DISCHARGE (CFS) = 1.1
MIN) = 250 DISCHARGE (CFS) = 1
MIN) = 260 DISCHARGE (CFS) = 0.9
MIN) = 270 DISCHARGE (CFS) = 0.8
MIN) = 280 DISCHARGE (CFS) = 0.8
MIN) = 290 DISCHARGE (CFS) = 0.7
MIN) = 300 DISCHARGE (CFS) = 0.7
MIN) = 310 DISCHARGE (CFS) = 0.6
MIN) = 320 DISCHARGE (CFS) = 0.6
MIN) = 330 DISCHARGE (CFS) = 0.6
MIN) = 340 DISCHARGE (CFS) = 0.6
MIN) = 350 DISCHARGE (CFS) = 0.5
MIN) = 360 DISCHARGE (CFS) = 0.5
MIN) = 370 DISCHARGE (CFS) = 0
I
I
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I
I
I
I
I
PRE ' f) Bu e L. o p iri B/^r
RATIONAL METHOD HYDROGRAPH PROGRAM
•OPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
"uNDATE 10/17/2006
HYDROGRAPH FILE NAME Textl sME OF CONCENTRATION 5 MIN.
HOUR RAINFALL 2.5 INCHES
\SIN AREA 13.7 ACRES
RUNOFF COEFFICIENT 0.82
PEAK DISCHARGE 74 CFS
IME
"ME
TIME
IME
ME
ME
TIME
^ME •ME •ME TIME
TIME •ME •ME
~ME
TIME
IME
ME
ME
TIME
IME
ME
ME
ME
TIME
IME
ME
ME
TIME
IME
ME
ME
TIME
TIME •ME •ME ™E
TIME
IME
ME
ME
TIME
TIME •ME •ME
TTME
TIME
IME
ME
ME
TIME
JIME
•VIE
PVIE TIME TIME EE E E TIME ^ME •VIE •ME TIME TIME •ME •ME TME TIME EE E E
(MIN) = 0 DISCHARGE (CFS) = 0
(MIN) = 5 DISCHARGE (CFS) = 1.7
(MIN) = 10 DISCHARGE (CFS) 1.7
(MIN) -15 DISCHARGE (CFS) = 1.8
(MIN) = 20 DISCHARGE (CFS) = 1.8
(MIN) = 25 DISCHARGE (CFS) = 1.8
(MIN) = 30 DISCHARGE (CFS) = 1.9
(MIN) = 35 DISCHARGE (CFS) = 1.9
(MIN) = 40 DISCHARGE (CFS) = 1.9
(MIN) = 45 DISCHARGE (CFS) = 2
(MIN) = 50 DISCHARGE (CFS) = 2
(MIN) = 55 DISCHARGE (CFS) = 2.1
MIN) = 60 DISCHARGE (CFS) = 2.1
MIN) = 65 DISCHARGE (CFS) = 2.2
MIN) = 70 DISCHARGE (CFS) = 2.3
MIN) = 75 DISCHARGE (CFS) = 2.3
MIN) = 80 DISCHARGE (CFS) = 2.4
MIN) = 85 DISCHARGE (CFS) = 2.5
^MIN) = 90 DISCHARGE (CFS) = 2.6
(MIN) = 95 DISCHARGE (CFS) = 2.7
(MIN) 100 DISCHARGE (CFS) = 2.8
(MIN) = 105 DISCHARGE (CFS) = 2.9
(MIN) = 110 DISCHARGE (CFS) = 3
(MIN) -115 DISCHARGE (CFS) = 3.2
(MIN) = 120 DISCHARGE (CFS) = 3.3
(MIN) = 125 DISCHARGE (CFS) = 3.5
(MIN) = 130 DISCHARGE (CFS) = 3.7
(MIN) = 135 DISCHARGE (CFS) = 4
(MIN) = 140 DISCHARGE (CFS) = 4.3
(MIN) = 145 DISCHARGE (CFS) = 4.7
(MIN) = 150 DISCHARGE (CFS) = 5.2
(MIN) = 155 DISCHARGE (CFS) = 5.8
(MIN) = 160 DISCHARGE (CFS) = 6.6
(MIN) = 165 DISCHARGE (CFS) = 7.9
(MIN) = 170 DISCHARGE (CFS) = 10
(MIN) = 175 DISCHARGE (CFS) = 14.7
(MIN) 180 DISCHARGE (CFS) = 74
(MIN) = 185 DISCHARGE (CFS) = 20.6
(MIN) = 190 DISCHARGE (CFS) = 11.8
(MIN) = 195 DISCHARGE (CFS) = 8.8
(MIN) = 200 DISCHARGE (CFS) = 7.2
(MIN) = 205 DISCHARGE (CFS) = 6.2
(MIN) = 210 DISCHARGE (CFS) = 5.4
(MIN) = 215 DISCHARGE (CFS) = 4.9
(MIN) = 220 DISCHARGE (CFS) = 4.5
(MIN) = 225 DISCHARGE (CFS) = 4.1
(MIN) 230 DISCHARGE (CFS) = 3.9
MIN) = 235 DISCHARGE (CFS) = 3.6
MIN) = 240 DISCHARGE (CFS) = 3.4
MIN) = 245 DISCHARGE (CFS) = 3.3
MIN) = 250 DISCHARGE (CFS) 3.1
MIN) = 255 DISCHARGE (CFS) = 3
MIN) = 260 DISCHARGE (CFS) = 2.8
MIN) = 265 DISCHARGE (CFS) = 2.7
MIN) = 270 DISCHARGE (CFS) = 2.6
MIN) = 275 DISCHARGE (CFS) = 2.5
MIN) = 280 DISCHARGE (CFS) = 2.5
MIN) = 285 DISCHARGE (CFS) = 2.4
MIN) = 290 DISCHARGE (CFS) = 2.3
MIN) = 295 DISCHARGE (CFS) = 2.2
MIN) = 300 DISCHARGE (CFS) = 2.2
MIN) = 305 DISCHARGE (CFS) = 2.1
MIN) = 310 DISCHARGE (CFS) = 2.1
MIN) = 315 DISCHARGE (CFS) = 2
MIN) = 320 DISCHARGE (CFS) = 2
MIN) = 325 DISCHARGE (CFS) = 1.9
MIN) 330 DISCHARGE (CFS) = 1.9
MIN) = 335 DISCHARGE (CFS) = 1.8
MIN) = 340 DISCHARGE (CFS) = 1.8
MIN) = 345 DISCHARGE (CFS) = 1.8
MIN) = 350 DISCHARGE (CFS) = 1.7
MIN) = 355 DISCHARGE (CFS) = 1.7
AJT
TIME (MIN) = 360 DISCHARGE (CFS) = 1.7
"llME (MIN) = 365 DISCHARGE (CFS) = 0
JOB z 5 1^ nsi
CONSULTING
PLANNING • DESIGN • CONSTRUCTION
800.479.3808 • WWW.RBF.COM
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Capture / Treatment Analysis
Unit Basin Storage Volume (inches)
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14.B MINUTES
POSTKXWSTRUCTION
^rf. 74.0 CFS
Tl- S.D HIM11EE
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T - IBO MINLn"ES
Q (CFS) 0 = 74.0 CFS
Cl = 14 .0 CFS-
T (MINUTES)
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RATIONAL METHOD HYDROGRAPH PROGRAM ROPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
UN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
(IME OF CONCENTRATION 13 MIN.
HOUR RAINFALL 2.5 INCHES
ASIN AREA 6.8 ACRES
RUNOFF COEFFICIENT 0.25
PEAK DISCHARGE 6.1 CFS •IME ^IME
TIME
IIME
IME
IME
TIME
JIME •IME •IME
TIME
TIME
•IME
•IME
^IME
TIME
JIME
•iME
•IME
TIME
TIME •IME
•iME
"IME
TIME
dIME
•IME
•iME
TIME
[IME
i
I
I
I
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(MIN = 0 DISCHARGE (CFS) = 0
(MIN = 13 DISCHARGE (CFS) = 0.3
(MIN = 26 DISCHARGE (CFS) = 0.3
(MIN = 39 DISCHARGE (CFS) = 0.3
(MIN = 52 DISCHARGE (CFS) = 0.3
(MINj = 65 DISCHARGE (CFS) = 0.3
(MIN] = 78 DISCHARGE (CFS) = 0.4
(MIN) = 91 DISCHARGE (CFS) = 0.4
(MIN) = 104 DISCHARGE (CFS) = 0.4
(MIN) = 117 DISCHARGE (CFS) = 0.5
(MIN) = 130 DISCHARGE (CFS) = 0.5
(MIN) = 143 DISCHARGE (CFS) = 0.6
(MIN) = 156 DISCHARGE (CFS) = 0.8
(MIN) = 169 DISCHARGE (CFS) = 1.2
(MIN) = 182 DISCHARGE (CFS) = 6.1
(MIN) = 195 DISCHARGE (CFS) = 1.6
(MIN) = 208 DISCHARGE (CFS) 1
(MIN) = 221 DISCHARGE (CFS) = 0.7
(MIN) = 234 DISCHARGE (CFS) = 0.6
(MIN) = 247 DISCHARGE (CFS) = 0.5
(MIN) = 260 DISCHARGE (CFS) = 0.4
MIN) = 273 DISCHARGE (CFS) 0.4
MIN) 286 DISCHARGE (CFS) 0.4
MIN) = 299 DISCHARGE (CFS) = 0.3
MIN) = 312 DISCHARGE (CFS) = 0.3
MIN) = 325 DISCHARGE (CFS) = 0.3
MIN) = 338 DISCHARGE (CFS) = 0.3
MIN) = 351 DISCHARGE (CFS) = 0.3
MIN) = 364 DISCHARGE (CFS) = 0.3
MIN) = 377 DISCHARGE (CFS) = 0
0 iy~>r^f I-j 0MB S
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RATIONAL METHOD HYDROGRAPH PROGRAM
•OPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
^UN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
^IME OF CONCENTRATION 5 MIN.
• HOUR RAINFALL 2.5 INCHES
•ASINAREA 6.8 ACRES
RUNOFF COEFFICIENT 0.79
PEAK DISCHARGE 34.5 CFS
X 0 i->f\i Hot^^S
(MIN) 0 DISCHARGE (CFS) = 0
(MIN) = 5 DISCHARGE (CFS) = 0.8
(MIN) = 10 DISCHARGE (CFS) = 0.8
(MIN) = 15 DISCHARGE (CFS) = 0.8
(MIN) = 20 DISCHARGE (CFS) = 0.9
(MIN) = 25 DISCHARGE (CFS) = 0.9
(MIN) = 30 DISCHARGE (CFS) = 0.9
(MIN) = 35 DISCHARGE (CFS) = 0.9
(MIN) = 40 DISCHARGE (CFS) = 0.9
(MIN) = 45 DISCHARGE (CFS) = 1
(MIN) -50 DISCHARGE (CFS) = 1
(MIN) = 55 DISCHARGE (CFS) = 1
(MIN) = 60 DISCHARGE (CFS) = 1
(MIN) = 65 DISCHARGE (CFS) = 1.1
(MIN) = 70 DISCHARGE (CFS) = 1.1
(MIN) = 75 DISCHARGE (CFS) = 1.1
(MIN) = 80 DISCHARGE (CFS) = 1.2
(MIN) = 85 DISCHARGE (CFS) = 1.2
(MIN) = 90 DISCHARGE (CFS) = 1.2
(MIN) = 95 DISCHARGE (CFS) = 1.3
(MIN) = 100 DISCHARGE (CFS) = 1.3
(MIN) -105 DISCHARGE (CFS) 1.4
(MIN) = 110 DISCHARGE (CFS) = 1.4
(MIN) = 115 DISCHARGE (CFS) = 1.5
(MIN) = 120 DISCHARGE (CFS) = 1.6
(MIN) = 125 DISCHARGE (CFS) = 1.7
(MIN) = 130 DISCHARGE (CFS) = 1.8
(MIN) = 135 DISCHARGE (CFS) = 1.9
(MIN) = 140 DISCHARGE (CFS) = 2.1
(MIN) = 145 DISCHARGE (CFS) = 2.2
(MIN) 150 DISCHARGE (CFS) = 2.5
(MIN) = 155 DISCHARGE (CFS) 2.8
(MIN) = 160 DISCHARGE (CFS) = 3.2
(MIN) 165 DISCHARGE (CFS) = 3.8
(MIN) = 170 DISCHARGE (CFS) = 4.8
(MIN) = 175 DISCHARGE (CFS) = 7
(MIN) = 180 DISCHARGE (CFS) = 34.5
(MIN) = 185 DISCHARGE (CFS) = 10.8
(MIN) = 190 DISCHARGE (CFS) = 5.6
(MIN) = 195 DISCHARGE (CFS) = 4.2
(MIN) 200 DISCHARGE (CFS) = 3.4
(MIN) = 205 DISCHARGE (CFS) = 2.9
(MIN) = 210 DISCHARGE (CFS) = 2.6
(MIN) = 215 DISCHARGE (CFS) = 2.3
(MIN) 220 DISCHARGE (CFS) = 2.1
(MIN) = 225 DISCHARGE (CFS) = 2
(MIN) = 230 DISCHARGE (CFS) = 1.8
(MIN) = 235 DISCHARGE (CFS) = 1.7
(MIN) = 240 DISCHARGE (CFS) = 1.6
(MIN) = 245 DISCHARGE (CFS) = 1.6
(MIN) = 250 DISCHARGE (CFS) = 1.5
(MIN) = 255 DISCHARGE (CFS) 1.4
(MIN) = 260 DISCHARGE (CFS) = 1.4
(MIN) 265 DISCHARGE (CFS) = 1.3
(MIN) = 270 DISCHARGE (CFS) = 1.3
(MIN) = 275 DISCHARGE (CFS) = 1.2
(MIN) = 280 DISCHARGE (CFS) = 1.2
(MIN) = 285 DISCHARGE (CFS) = 1.1
(MIN) = 290 DISCHARGE (CFS) = 1.1
(MIN) 295 DISCHARGE (CFS) = 1.1
(MIN) = 300 DISCHARGE (CFS) = 1
(MIN) = 305 DISCHARGE (CFS) = 1
(MIN) = 310 DISCHARGE (CFS) = 1
(MIN) = 315 DISCHARGE (CFS) = 1
(MIN) = 320 DISCHARGE (CFS) = 0.9
(MIN) = 325 DISCHARGE (CFS) 0.9
(MIN) = 330 DISCHARGE (CFS) = 0.9
(MIN) = 335 DISCHARGE (CFS) = 0.9
(MIN) = 340 DISCHARGE (CFS) = 0.9
(MIN) = 345 DISCHARGE (CFS) = 0.8
(MIN) = 350 DISCHARGE (CFS) = 0.8
(MIN) = 355 DISCHARGE (CFS) = 0.8
TIME (MIN) = 360 DISCHARGE (CFS) = 0.8
•TIME (MIN) = 365 DISCHARGE (CFS) = 0
JOB. ZT lol ITI
SHEETNO. 15 OF n
C O N S U LTI N G
PLANNING • DESIGN • CONSTRUCTION
8aa.479.380B * WWW.RBF.COM
CALCULATED BY.
CHECKED BY
SCALE
DATE
DATE
)o/i^7<)^
'"ST - (- r * A/
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San Diego WSO Airport (7740) - San Diego County, California
Capture / Treatment Analysis
Unit Basin Storage Volume (inches)
PRE-CO^JSTRUCTIO^J
q.- «.t CTS
13. a M[I«JTES
POST-C0r,BTRUCTI0N
Our M.5 CFS
r<- S.Z MMTTES
TOTAL SITE AREA = 6.B «
IfJFILTHATIDtJ VOUIE - 1. IJ AC-FT
DETQ^rraj VOLUME - 0.77 AC-n
T - 180 MI^Jl;rES
Q (CFS)
0 = 34.5 CFS
Q - 6.1 CFS
T (MINUTES)
T - 182 MlfJUTES
PONTO VISION
RBF JN Z5101951
TOWNHOMES
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JOB.
SHEETNO.
7^ IOI 15'!
OF /
CONSULTING
PLANNING • DESIGN • CONSTRUCTION
800.479.3808 • WWW.RBF.COM
CALCULATED BY .
CHECKED BY
SCALE
7' DATE
DATE
10/1^7 0^
FoR^ A D&T/9TLED D^^<^^rPTTo^ Op ^TPPJ
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RATIONAL METHOD HYDROGRAPH PROGRAM
lOPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
INUNDATE 10/19/2006
HYDROGRAPH FILE NAME Textl
iIME OF CONCENTRATION 10 MIN.
HOUR RAINFALL 2.5 INCHES
ASIN AREA 0.9 ACRES
RUNOFF COEFFICIENT 0.32
^EAK DISCHARGE 1.2 CFS
•IME
TIME
TIME
•IME
•ME
^ME
TIME
^ME •ME •ME
TIME
TIME •ME •ME
TIME
TIME
IME
ME
ME
TIME (ME ME ME ME TIME IME ME ME TIME ^ME •ME •ME TIME TIME RME ME ME TIME
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
: 0
•• 10
•• 20
•• 30
•• 40
•• 50
•• 60
•• 70
: 80
: 90
100
•• 110
: 120
: 130
•• 140
• 150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0.1
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0
PRE
RATIONAL METHOD HYDROGRAPH PROGRAM
lOPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
RUN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
IIME OF CONCENTRATION 5 MIN.
HOUR RAINFALL 2.5 INCHES
ASIN AREA 0.9 ACRES
RUNOFF COEFFICIENT 0.82
JEAK DISCHARGE 4.9 CFS
•IME
TIME
TIME •IME •IME
^IME
TIME
IIME
IME
IME
TIME
(IME
IME
IME
IME
TIME
IME
ME
ME
TIME
jME
ME
ME
TIME
TIME
IME
ME
ME
TIME
^ME •ME •ME
TIME
TIME •ME •ME
TIME
TIME
IME
ME
ME
TIME
IME
ME
ME
ME
TIME IME
ME
ME
TIME
J^ME
•ME •ME TIME TIME •ME •ME TIME TIME JUME •ME •ME TIME TIME •ME •ME "ME TIME IME ME ME
(MIN = 0 DISCHARGE (CFS = 0
(MIN = 5 DISCHARGE (CFS 0.1
(MIN = 10 DISCHARGE (CFS = 0.1
(MIN = 15 DISCHARGE (CFS = 0.1
(MIN; = 20 DISCHARGE (CFS 0.1
(MIN = 25 DISCHARGE (CFS = 0.1
(MIN = 30 DISCHARGE (CFS = 0.1
(MIN = 35 DISCHARGE (CFS = 0.1
(MIN) = 40 DISCHARGE (CFS^ = 0.1
(MIN) = 45 DISCHARGE (CFS = 0.1
(MIN) = 50 DISCHARGE (CFS) = 0.1
(MIN) = 55 DISCHARGE (CFS) = 0.1
(MIN) = 60 DISCHARGE (CFS) = 0.1
(MIN) = 65 DISCHARGE (CFS) = 0.1
(MIN) = 70 DISCHARGE (CFS) = 0.1
(MIN) = 75 DISCHARGE (CFS) = 0.2
(MIN) = 80 DISCHARGE (CFS) = 0.2
(MIN) = 85 DISCHARGE (CFS) = 0.2
(MIN) = 90 DISCHARGE (CFS) = 0.2
(MIN) = 95 DISCHARGE (CFS) = 0.2
(MIN) = 100 DISCHARGE (CFS) = 0.2
(MIN) = 105 DISCHARGE (CFS) = 0.2
(MIN) = 110 DISCHARGE (CFS) = 0.2
(MIN) = 115 DISCHARGE (CFS) = 0.2
(MIN) = 120 DISCHARGE (CFS) = 0.2
(MIN) = 125 DISCHARGE (CFS) = 0.2
(MIN) = 130 DISCHARGE (CFS) = 0.2
(MIN) = 135 DISCHARGE (CFS) = 0.3
(MIN) = 140 DISCHARGE (CFS) 0.3
(MIN) = 145 DISCHARGE (CFS) = 0.3
(MIN) = 150 DISCHARGE (CFS) = 0.3
(MIN) 155 DISCHARGE (CFS) = 0.4
(MIN) = 160 DISCHARGE (CFS) = 0.4
(MIN) = 165 DISCHARGE (CFS) = 0.5
(MIN) = 170 DISCHARGE (CFS) = 0.7
(MIN) = 175 DISCHARGE (CFS) = 1
(MIN) = 180 DISCHARGE (CFS) = 4.9
(MIN) = 185 DISCHARGE (CFS) = 1.3
(MIN) = 190 DISCHARGE (CFS) = 0.8
(MIN) = 195 DISCHARGE (CFS) = 0.6
(MIN) = 200 DISCHARGE (CFS) = 0.5
(MIN) = 205 DISCHARGE (CFS) = 0.4
(MIN) = 210 DISCHARGE (CFS) = 0.4
(MIN) = 215 DISCHARGE (CFS) = 0.3
(MIN) = 220 DISCHARGE (CFS) = 0.3
(MIN) = 225 DISCHARGE (CFS) = 0.3
(MIN) = 230 DISCHARGE (CFS) = 0.3
(MIN) = 235 DISCHARGE (CFS) = 0.2
(MIN) = 240 DISCHARGE (CFS) 0.2
(MIN) = 245 DISCHARGE (CFS) = 0.2
(MIN) = 250 DISCHARGE (CFS) = 0.2
(MIN) = 255 DISCHARGE (CFS) = 0.2
MIN) = 260 DISCHARGE (CFS) = 0.2
(MIN) = 265 DISCHARGE (CFS) = 0.2
(MIN) = 270 DISCHARGE (CFS) = 0.2
MIN) = 275 DISCHARGE (CFS) = 0.2
MIN) = 280 DISCHARGE (CFS) = 0.2
MIN) = 285 DISCHARGE (CFS) = 0.2
MIN) = 290 DISCHARGE (CFS) = 0.2
MIN) = 295 DISCHARGE (CFS) = 0.1
MIN) = 300 DISCHARGE (CFS) = 0.1
MIN) = 305 DISCHARGE (CFS) = 0.1
MIN) = 310 DISCHARGE (CFS) = 0.1
MIN) 315 DISCHARGE (CFS) = 0.1
MIN) = 320 DISCHARGE (CFS) = 0.1
MIN) = 325 DISCHARGE (CFS) = 0.1
MIN) = 330 DISCHARGE (CFS) = 0.1
MIN) = 335 DISCHARGE (CFS) = 0.1
MIN) = 340 DISCHARGE (CFS) = 0.1
MIN) = 345 DISCHARGE (CFS) = 0.1
MIN) = 350 DISCHARGE (CFS) = 0.1
MIN) = 355 DISCHARGE (CFS) -0.1
fos-r
JME (MIN) = 360 DISCHARGE (CFS) = 0.1
IME (MIN) = 365 DISCHARGE (CFS) = 0
JOB.
SHEETNO.
ZT IOI 15;
/ 7 OF
CONSULTING
PLANNING • DESIGN • CONSTRUCTION
800.479.3008 • WWW.RBF.COM
CALCULATED BY .
CHECKED BY
SCALE
5C DATE
DATE
10^ l7/(f6
Us, 1
[100 y - /A^^
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Capture / Treatment Analvsis
Unit Basin Storage Volume (inches)
PRE-CO^JSTRUCTIO^J
0^ t,2 CFS
1^- 10.4 M[NUTES
POST-CONSTRUCT 10^J
4.a CTS
r<' S.D MINUTES
TOTAL SITE AREA = 0.9 AC
irriLTRATIDM VOLUkE = 0.16 AC-FT
DETBfl"IOrJ VOLUME - Q.OS AC-FT
Q (CFS)
180 MlhWES
T (MINUTES)
IBO UINUTES
PONTO VISIOtJ
RBF J-'l Z5101931
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BOO.479.3808 * WWW.RBF.COM
JOB. Z5 I 01 1^1
SHEETNO.
CALCULATED BY.
CHECKED BY
SCALE
; c
OF
DATE
DATE
JA
10/ \s706
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U
TIONAL METHOD HYDROGRAPH PROGRAM
OPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
UN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
IIME OF CONCENTRATION 11 MIN.
HOUR RAINFALL 2.5 INCHES
ASINAREA 1.3 ACRES
RUNOFF COEFFICIENT 0.32
EAK DISCHARGE 1.7 CFS
jjfiME
TIME
TIME
•IME
•IME
^IME
TIME
^IME •IME •IME
TIME
TIME •IME •IME
~IME
TIME
IIME
IME
IME
TIME
JIME •IME •IME
TIME
TIME
(IME
IME
IME
TIME
^IME •IME •ME
TIME
TIME
||ME
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
= 0 DISCHARGE (CFS) = 0
= 11 DISCHARGE (CFS) = 0.1
= 22 DISCHARGE (CFS) = 0.1
= 33 DISCHARGE (CFS) = 0.1
= 44 DISCHARGE (CFS) = 0.1
= 55 DISCHARGE (CFS) = 0.1
•• 66 DISCHARGE (CFS) = 0.1
^77 DISCHARGE (CFS) = 0.1
•• 88 DISCHARGE (CFS) =
•• 99 DISCHARGE (CFS) =
MIO DISCHARGE (CFS) =
•• 121 DISCHARGE (CFS) =
•• 132 DISCHARGE (CFS) = 0.1
•• 143 DISCHARGE (CFS) = 0.1
: 154 DISCHARGE (CFS) = 0.2
165 DISCHARGE (CFS) =
•• 176 DISCHARGE (CFS) =
• 187 DISCHARGE (CFS) =
198 DISCHARGE (CFS) =
209 DISCHARGE (CFS) =
220 DISCHARGE (CFS) =
231 DISCHARGE (CFS) = 0.2
242 DISCHARGE (CFS) = 0.1
253 DISCHARGE (CFS) = 0.1
264 DISCHARGE (CFS) = 0.1
275 DISCHARGE (CFS) = 0.1
286 DISCHARGE (CFS) = 0.1
297 DISCHARGE (CFS) = 0.1
308 DISCHARGE (CFS) = 0.1
319 DISCHARGE (CFS) = 0.1
330 DISCHARGE (CFS) =
341 DISCHARGE (CFS) =
352 DISCHARGE (CFS) =
363 DISCHARGE (CFS) =
374 DISCHARGE (CFS) =
0.1
0.1
0.1
0.1
0.2
0.3
1.7
0.4
0.3
0.2
0.1
0.1
0.1
0.1
0
I
I
I
I
I
I
I
I
RATIONAL METHOD HYDROGRAPH PROGRAM tOPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
UN DATE 10/19/2006
HYDROGRAPH FILE NAME Textl
KIME OF CONCENTRATION 5 MIN.
HOUR RAINFALL 2.5 INCHES
ASINAREA 1.3 ACRES
RUNOFF COEFFICIENT 0.82 <EAK DISCHARGE 7 CFS
1
LTVB / K X
TME
"IME
TIME
•"IME •IME
^IME
TIME
f lME
IME
IME
TIME
TIME •IME •IME
"IME
TIME
IIME
IME
IME
TIME
JIME •IME •IME
"IME
TIME
IIME
IME
IME
TIME
jIME
IME
IME
TIME
TIME •IME •IME
^IME
TIME
^IME
•IME
•iME
TIME
TIME •IME •IME
TIME
TIME
IIME
IME
IME
TIME
JIME •ME •ME TIME TIME IME ME ME TIME ^ME •ME •ME TIME TIME •ME •ME ^ME TIME IME ME ME
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
(MIN
= 0
= 5
= 10
= 15
= 20
= 25
= 30
= 35
: 40
= 45
= 50
= 55
= 60
= 65
: 70
= 75
= 80
= 85
= 90
= 95
= 100
= 105
= 110
= 115
= 120
= 125
•• 130
•• 135
: 140
•• 145
•• 150
•• 155
•• 160
•• 165
•• 170
: 175
180
185
•• 190
195
: 200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
325
330
335
340
345
350
355
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 1.4
DISCHARGE (CFS) = 7
DISCHARGE (CFS) = 2
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.3
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
DISCHARGE (CFS) = 0.2
05 r
riME (MIN) = 360 DISCHARGE (CFS) = 0.2
llME (MIN) = 365 DISCHARGE (CFS) = 0
JOB.
SHEETNO.
7S IOI "isj
I 1 OF
CONSULTING
PLANNING • DESIGN • CON8TRUCTION
800.479.3808 • WWW.RBF.COM
CALCULATED BY .
CHECKED BY
SCALE
DATE
DATE
10 ' 19- 0^
XX FXCrnAYTi/^/ C 1^^ '0'' - ^^'•^
^i^BA'- X't'Zc? [0,21 c^..fi
4 ,^7 - X ^5'='^ 5•,3(^/ ^/
1/
6- .
/4i>3^iTPD- ,5/ ' ff C l.'b^ 0 0 6 e^cH
Ll7\Al / 1/ z
San Diego WSO Airport (7740) - San DIego County, California
Capture / Treatment Analysis
• • n M 0-5 0.6 0 7
Unit Basm Storage Volume (inches)
I
PRE-CQ^^ISTRUCTI0^4
Of 1.7 CFS
•b- 10.a MINUTES
posT-co^JSTRUcTIO^^
9^ 7 .D CFS
r<* S.D MMTIES
TOTAL SITE AREA = 1.3 AC
INFILTHATIDN VQLUIE =0.22 AC-FT
DETOJTION VOLUME = 0.12 AC-FT
Q (CFS)
T = 180 HirJLfTES
T (MlfJUTES)
T = 187 MINUTES
POMTO visior4
RBF JN 25101951
FIGURE 7 - UVE/WORK MIXED USE 2
IBBNaUUnNB
Vegetated Buffer Strip TC-31
Design Considerations
a Tr>&iilai'y Area
a Slops
• Waler Aval'abiiiy
• Aest..ielics
Description
Grassed buffer strip.s (vegetateci filter .strips, filter strips, and
grassed filters) are vegetated surfaces lhat are designeci to treat
sheet flow from adjacent surfaces. Fitter strips function hy
slowing runoff velocities and allowing sediment and other
pollutant-s to settle and by providing »ome infiltration into
underljing .wils, Filter strips were originally used as an
agricultural treatment practice and have more recently <>voivGd
into an urban praaice. With proper design a«d tnaintetiHnce,
filter stri».s can provide relatively high pollutant removal. In
addition, tho public \iews them as landscaped amenities and nnt
us stomivx'ater infrastmcture. Consequently, there is little
resistance to their u.ie.
California Experience
Caltrans constructed and monitored tiiree vegetated buffer strips
in southern California and is currently evaluating their
performance at eight additional sites statewide. These strips were
Kt'cieraliy effective in reducing the voinme and ma.ss of ixilUitants
in runoff. Kven in the areas vdiere the fttmaal rainfall was only
rthont TO inches/yi\ the vegetfition did not require additional
irrigation. One factor that strongly affected petforniance ^va-4 the
presence of large nu iTiher.s of gopliers a t most (if t he soutii ern
California .sites. Tlie gophers crcated eaiUien mounds, desUoyed
vt^etation, and }tetierally raiuced the eiTectiveness ofthe
L'fjntrols for TSS reduction.
Advantages
a Buffers require minimal maintenance acti\ity (generally just
erosion prevention and moxving).
* If properly designed, vegetated, and operated, buffer strips can
provide reliable water quality benefits in conjunttioii with high
aesthetic appeal.
Targeted Constituents
1/ SedinKfit
/ N'Llrients
Tfash
•f Metals
•/ Baaena
/ Oil and G«ssa
/ Orgsr^s
Legend ffisnww^giffstw^Messi
• Lw B High
Stormw«t«r
Ouatity
AHoriMion
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TC-31 Vegetated Buffer Strip
• Flow characteristics and wgetation type and density can be closely controlled to maximize
BMP effectiveness,
•I Roadside shoulders act as effective buffer strips when slope and length meet criteria
described below.
Limitations
• May not be appropriate for industrial sites or locations where spills may occur.
• Buffer strips cannot treat a very large drainage area.
• A thick vegetative cover is needed for these practices to function properly.
• Bufifer or vegetative filter length must be adequate and flow characteristics acceptable or
water quality performance can be severely limited.
• Vegetative buffers may not provide treatment for dissolved constituents except to the extent
that flows across the vegetated surface are infiltrated into the soil profile.
• This technology does not provide significant attenuation of the increased volume and flow
rate of runoff during intense rain events,
Oesign and Sizing Guidelines
• Maximum length (in the direction of flow towards the buffer) ofthe tributary area should be
60 feet.
• Slopes should not exct$ed 15%.
• Minimum length (indirection of flow) is 15 feet.
• Width should be the same as the tributary area.
B Either grass or a diverse selection of olher low growing, drought tolerant, native vegetation
-ihould be specified. Vegetation whose growing season corresponds to the wet season is
preferred.
Construction/htspeetion Considerations
• Include directions in the specifications for use of appropriate fertilizer and soil amendments
based on soil propeities determined through testing and compared to the needs of the
vegetation requirements.
• Install strips at the time of the year when there is a reasonable chance of successful
establishment without irrigation; however, it is recognized that rainiali in a given year may
not be suifident and temporary irrigation may be required.
• If sod tiles must be used, they should be placed so that there are no gaps between the tile.;;
stagger the ends ofthe tiles to prevent the foimation of channels along the strip.
• Use a roller on. the sod to ensure that no air pockets form between the sod and the soil.
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• Where seeds are used, erosion controls will be necessaiy to protect seeds for al least 75 days
after the &rst rainfall of the season.
Performance
Vegetated buffer strips tend to provide somewhat better treatment of stormwater runoff than
swvies and have fevrer tendencies for channelization or erosion. Table l documents the pollutant
removal observed m a recent study by Caltrans (2002) based on three sites in southem
Cahfomia. The column labeled "Significance" is the probability that the mean influent and
effluent EMCs are not significantly different based on an analysis of variance,
The renioA^l of sediment and dissolved metals was comparable to that obsei-ved in much more
complex controls. Reduction in nitrogen was not significant and all of the sites exported
phosirfiorus for the entire study period. This may have been the x-esult of using sah grass, a warm
weather species that is dormant during the wet season, and which leaches phosphorus when
donnant.
Another Caltrans study (unpublished) of vegetated highway shoulders as bufifier strips also found
stibstantial reductions often within a very short distance of the edge of pavement- Figure l
presents a box and whisker plot of the concentrations of TSS in highway runoff after traveling
various distances (shown in meters) through a vegetated filter strip with a slope of about 10%.
One can see that the TSS median concentration reaches an irreducible minunum concentration
of about 20 mg/L within 5 meters ofthe pavement edge.
TBbl« 1 Pollutant Rmluction in a Vegetated Buffer Strip
Mean EMC
ConstStiiciit Remijval Signlflcaiice
Influent Effluent % P
TSS i»9 3» 74 <t}.0O0
NOj-N 0.67 0.5a •3 0.367
TKN-N 2.50 2.10 l&
Total N* 3.17 2.6S 15 -
Dissolved P 0.13 0.46 -206 Q.047
Total P 0.42 0.6a •i^ 0035
TcrtalCn 0.058 0.009 84 <a.ooo
Total Pb 0.046 0.006 88 < 0,000
Total Zn 0.24.5 0.055 78 < 0.000
l>lssolved Cu 0039 0,007 77 0004
l>issolv«d Pb 0,004 0.00a 66 0.006
D«8»olv«<t Zn 0.099 0,035 65 <0.000
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TC-31 Vegetated Buffer Strip
Filter strips also exhibit good removal of litter and other floatables because the %vater depth in
these systems is well below the vegetation height and consequently these materials are not easily
transported through them. Unfortunately little attenuation of peak runoff rales aiKl volumes
(particularly for lai-ger events) is normally observed, depending on the soii properties. Therefore
it may be prudent to follow the strips with another practice than can reduce flooding and
channel erosion downstream.
Siting Criteria
The use of buffer strips is limited to gently sloping areas where the vegetative cover is i-obu.st and
difhise, and where shaUow flow characteristics are possible. The practical water qualily bifuefits
can be effectively eliminated %vith the occurrence of significant erosion or when flow
concentration occurs across the vegetated surface. Slopes should not exceed 15 percent or i>e less
than I percent. The vegetative surface should extend across the fidl width of the area twing
drained. Tbe upstream boundary of the filter should be located contiguous to the developed
area. Use of a level spreading device (vegetated lienn, sawtooth concrete border, rock trench,
etc) to facilitate overland sheet flow is not normally recommended because of maintenance
considerations and the potential for standing vinter.
Filter strips are npplicable in most regions, but are restricted in some situations because they
consume a large amount of space relative to other practices. Filter strips are best suited to
treating runoff from roads and highAvaj.'s, roof downspouts, small parking lots, and pervious
surfaces. They are also ideal components of the "outer zone" of a stream buffer or as
pretreatment to a structural practice. In arid areas, however, the cost of irrigating the grass on
the practice \vill most likely outweigh its water qualily benefits, although aesthetic
considerations may be sufficient to overcome this constraint. Filter strips are generally
impractical in ultra-urban areas where little peivious surface exists.
Some cold water species, such as trout, are sensitive to changes in temt^erature. While -wme
treatment practices, such as wet ponds, can warm stormwater substantially, itlter strips do not
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Vegetated Buffer Strip TC-31
are not expected to increase stormwater temperatures. Thus, these practice.* are good for
protection of cold-water streams.
Filter strips should be separated from the ground water by between 3 and 4 fl to prevent
contamination and to ensure that the filter strip does not remain wet between storms.
Additional i>esign Guidelines
Filter strips appear to be a minimal design practice because they are basically no more than a
grassed slope. In general the slope of the strip should not exceed I5fc% and the strip should be
at least 15 feet long to provide ivater quality treatment. Both the top and toe ofthe slope should
be as flat as possible to encourage sheet flow and prevent erosion. The top of the strip should be
installed 2-5 inches below the adjacent pavement, so that vegetation and sediment accumulation
at the edge of the strip does not prevent runoff from entering.
.<\ m^jor question that remains unresolved is how large the drainage area to a strip can be.
Research has conclusively demonstrated that these are effective on roadside shoulders, where
the contributing area is about twice the buffer area, They have also been installed on the
perimeter of large parking lots where the>' performed fairly effectively; hovirever much lower
slopes may be needed to provide adequate water quality treatment.
The filter area should be densely vegetated wth a mix of erosion-resistant plant species that
effectively bind the soil. Native or adapted grasses, shrubs, and trees are preferred because they
generaliy require less fertilizer and are more drought resistant than e.xotic plants. Runoff flow
velocities should not exceed about 1 fps across the vegetated surface.
For engineered vegetative strips, the facility surface should be graded flat prior to placement of
vegetation. Initial establishment of vegetation requires attentive care including appropriate
watering, fertilization, and prevention of excessive flow across the facliit)' until vegetation
completely covers the area and is well estabUshed. Use of a permanent irrigation system may
help provide maximal water quality performance.
In cold climates, filter strips provide a convenient area for snow storage and treatment. If used
for this purpose, vegetation in the filter strip should be salt-tolerant (e.g., creeping bentgi-ass),
and a maintenance schedule should indude the removal of sand built up at the bottom of the
slope. In arid or semi-arid climates, designers should specify drought-tolerant grasses to
minimize irrigation requirements.
Maintenance
Filter strips require mainly vegetation management; therefore Uttle special training is needed
for maintenance crews. Typical maintenance activities and frequencies include:
• Inspect strips at least twice annually for erosion or damage to vegetation, preferably at the
end of the wet season to schedule summer maintenance and before major fall nm-off to be
sure the strip is ready for svintet. However, additional inspection after periods of hea\'y run-
off is most desirable. The strip .should be checked for debris and litter and areas of secUment
accumulation.
• Recent research on biofiltration swales, but likely applicable to strips (Colwell el al., 2000),
indicates that grass height and mowing irequencjf have little impact on pollutant removal;
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consequently, mowing may only be necessary once or twice a year for safety and aesthetics
or to suppress weeds and woody vegetation.
• Trash tends to accumulate in strip areas, particularly along highways. The need for litter
removal should be determined through periodic inspection but litter should always be
removed prior to mowing.
• Regularly inspect vegetated buffer strips for pools of standing water. Vegetated buffer strips
can become a nuisance due to mosquito breeding in level spreaders (unless designed to
dewater completely in 48-72 hours), in pools of standing water if obstructions develop (e.g,
debris acctunulation, invasive vegetation), and/or if proper drainag;e slopes are not
implemented and maintained.
Cost
Cbnsfntctfon Cost
Little data is available on the actaal construction costs of filter strips. One rough estimate can be
the cost of seed or sod, which is approximately 30* per ft* for seed or 70$ per ft* for sod. This
amounts to between $13,000 and $30,000 per acre of filter strip. This cost is relatively high
compared vrith other ti*eatment practices. However, the grassed area used as a filter strip may
have been seeded or sodded even if it were nol used for treatment. In these cases, the only
additional cost is the design. Topical maintenance costs are aiiout $350/acre/year (adapted
from SWRPC, i99t)- This cost is relatively inexpen.<iivQ and, again, might overlap with regular
landscape maintenance costs.
The true cost of filter strips is the land they consume. In some situatioits this land is a^-aiiable as
wasted space beyond back yards or adjacent to roadsides, but this practice is cost-prohibitive
when land prices are high and land could be used for other purposes.
Muintenance Cost
Maintenance of vegetated buffer strips consists mainly of vegetation management (mowing,
irrigation if needed, weeding) and litter removal. Consequently the costs are quite variable
depending on the frequency of these activities and the local labor rate.
References and Sources of Additional Information
Caltrans, 2002, BIMP Retrofit Pilot Program Proposed Final Report, Rpt. CTSW-RT-oi-050,
California Dept. of Transportation, Sacramento, CA.
Center for Watershed Protection (CWP). 1996. Design qf Stormitfater Filtering Systems.
Prepared for Chesapeake Research Consortium, Solomons, MD, and EPA Region V, Chicago, IL.
Desbonette, A., P. Fogue, V. Lee, and N. Wolff, 1994. Vegetated Buffers in the Coastal Zone: A
Summary Review and Bihliagraphy. Coastal Resources Center. University of Rhode Island,
Kingston, Rl.
Magette, W., R. Brinsfield, R, Palmer and J. Wood. 1989, Nutrient and Sediment Removal by
Vegetated Filter Strips. TVansacrioFis of the American .^ciety ofAgricvttural Engineers 32(a):
663-667-
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Metzger, M. E., D. F. Messer, C. L. Beitia, C. M. Myers, and V. L. Kramer. 2002. The Dark Side
Of Stormwater Runoff Management: Disease Vectors Associated With Structural BMPs.
Stormwater 3(2): 24-39.
Southeastem Wisconsin Regional Planning Commission (SWRPC). 1991, Cosfs uf Urban
Nonpoint Source Water Pollution Control Measures. Technical report no. 31. Southeastem
Wisconsin Regional Planning Commission, Waukesha, Wl,
Yu, S., S. Barnes and V. Gerde. 1993. Testing of Best Management Pmcticesfor ControUing
Highway Runoff. FHWA/VA 93-R16. Virginia Transportation Research Council,
Chariotlesville, VA.
It{fbrmation Resources
Center for Watershed Protection (CWP). 1997, Stormwater BMJP Design Supplement/or Cold
Climates. Prepared for U.S. Environmental Protection Agency Office of Wetlands, Oceans and
Watersheds. Washington, DC.
Maryland Department ofthe Environment (MDE). 2000. Maryland Stormwater Design
Manual http://wwWrmde.8tate.md.us/environment/wma/stonnwatermanual. Accessed May
aa, 2001.
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lUa
twwauii, and afriilHiwrt wff ilrip)
Note Not to Sab
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Infiltration Basin TC-11
'^:j77yr
Description
An infiltration basin is a shallow impoundment that is designed
to uifiltrate stonnwater. Infiltration basins use the natural
fUtering abili^ of the soil to remove pollutants in storm^vater
runoff. Infiltration facilities store runoff until it gradually
exfiitrates through the soil and ev«»tually into the water table.
This practice has high pollutant removal efficiency and can also
help recharge groundwater, thus helping to maintain low fimvs in
stream systems. Infiltration basins can be challenging to apply
on many sites, however, because of soils requirements. In
addition, some studies have sho\vn relatively high failure rates
compared vrith other management practices.
California Experience
Infiltration basins have a long history of use in California,
especially in the Central Valley. Basins located in Fresno were
among those initially evaluated hi the National Urban Runoff
Pro-am and were fbund to be effective at reducing the \'Dlume of
runoff, while posing tittle long-term threat to groundvirater
quality (EPA, 1983; Schroeder, 1995). Proper siting of these
de^'ices Is crudal as underscored by the experience of Caltrans in
siting tm basins in Southem Califomia, The basin with
marginal separation firom groundwater and soil permeability
failed immediately and could never be rehabilitated.
Advantages
• Provides 100% reduction in the load discharged to surfoce
waters.
• The principal benefit of infiltration basins is the
approximation of pre-development hydrology during which a
Design Considerations
• Soil for InfiftratScn
• Slope
• Aeethallcs
Targeted Constituents
•
•
•
•
Sediment
Nulrienls
Tr*8h
Melals
Baclerla
Oil and Grease
On^anics
Lagend (Rmoval SHutlvtoti^
a Low • High
A Mediuni
aiiMmia
Stornwatw
Ouanty
AsiDdMion
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significant portion of the average annual rainfall runoff is infiltrated and evaporated rather
than flushed directly to creeks.
• If the water qualitv' volume is adequately sized, infiltration basins can be useful for providing
control of channel forming (erosion) and high frequencj' (generally less than the 2-year)
flood events.
Limitations
a May not bft appropriate for industrial sites or locatiotis where spills may occur.
a Infiltration basins require a minimum .soil infiltration rate of 0.5 inches/hour, nol
appropriate at sites with Hydrologic Soil Types C and D.
a If infiltration rates exceed 2.4 inches/hour, tlien the runoff shouki be fiilly treated prior to
infilti-ation to protect groundwater quality.
• Not suitable on fill sites or steep slopes.
• Risk of groundwater contamination in veiy coarse soils.
a Upstream drainage area must be completely stabilized before ctjnslruction.
• Difficult to reistore fimctioning of infiltration basins once clogged.
Design and Sizing Guidelines
• Water quality volume determined by local requirements or sized so that 85% of the annual
runoff vohime is captured.
• Basin sized so that the entire vvater qualit>' volume is infiltrated vvithin 48 hours,
• Vegetation e-Htablishment oti the basin floor may help retiuce the clogging rate.
Construction/Inspeetion Consiilera tions
a Before construction begins, stabilize the entire area draining to the fadlity, If impossible,
place a diversion berm around the perimeter nf the infiltration site to prevent sediment
entrance during constrtiction or remove the top 2 inche.'s of .<!oil after the site is stabililized.
Stabilize the entire contributing drainage area, induding the side .ilopes, before allovving any
nmoff to enter once construction is complete.
• Place excavated material such that it can not be washed back into the basin if a storm occurs
during construction of the facility.
a Build the basin without ilriving heavy equipiutinl o\er the infiltration surface. Any
equipment driven on the surface should have extra-wide ("low pressure") tires. Prior to any
construcrion, rot>e off the infiltration area to stop entrance by unwanted equipment.
B .After final grading, till the infiltrfllion ."surface deeply.
» Use appropriate erosion control seed mis for the spe<:ific project and location.
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Performance
As water migrates through porous soil and rock, pollutant attenuation mechanisms indude
precipitation, sorption, physical filtration, and bacterial degradation. If functionmg properly,
this approach is presumed to have high removal efficiencies for particulate pollutants and
moderate removal of soluble pollutants. Actual pollutant remo^-al in the subsurface would fae
expected to vary depending upon site-specific soil types. This technology eliminates discharge to
surfece waters exe&pt for the very largest storms; consequently, complete removal of al!
stormwater constituents can be assumed.
There remam some concerns about the potential for groundwater contamination despite the
findings ofthe NURP and Nightingale (1975; I987a,b,c; 19S9). For instance, a report by Pitt et
al- (1994) highlighted the potential for groundwater contamination fi-om intentional and
unintentional stormwater infiltration. That report recommends that infiltration facilities not be
sited in areas vriiere high concentrations are present or where there is a potential for spills of
toxic material Conversely, Schroeder (1995) reported that there was no evidence of
groundwater impacts fi-om an infiltration basin serving a large industrial catchment in Fresno
CA.
Siting Criteria
The key element in siting infiltration basins is identii>ing sites with appropriate soil and
hydrogeologic properties, which is critical for long terra performance. In one shidy conducted in
Pnnce George's County, Maryland (Galli, 1992), all ofthe infiltration basins investigated clogged
within 2 years. It is believed that these failures were for the most pait due to allowing infiltration
at sites with rates of less than 0.5 in/hr. basing siting on soil type rather lhan field infihration
tests, and poor construction practices that resulted in soil compaction ofthe basin invert.
A study of 23 infiltration basins in the Pacific Northwest showed better long-term performance
in an area with highly permeable soils (Hilding, 1996). In this study, few ofthe uifihration
basuis had failed after 10 years. Consequently, the follovring guidelines for identif>'ing
appropriate soil and sulisurface conditions should be rigorously adhered to,
• Determine soil type (consider RCS soil tj-pe % B or C only) from mapping and oonsiUt
USDA soil survey tables to review other parameters such as the amount of silt and clay,
presence of a r^rictive layer or seasonal high water table, and estimated permeability.' The
soil should not have more than 30% clay or more than 40% of clay and silt combined.
Eliminate sites that are clearly unsuitable for infiltration.
• Groundwater separation should be at least 3 m from the basin invert to the measured
ground water elevation. There is concem al tiie state and regional levels ofthe impact on
groundwater quality from infiltrated runoff, especially when the separation between
groundwater and the surface is small
• Location away ftom buildings, slopes and highway pavement (greater than 6 m) and wells
and bridge structures (greater than 30 m). Sites constructed of fill, having a base flow or
with a slope greater than 15?^ shoidd not be considered.
• Ensure that adequate head is available to operate flow splitter structures (to allow the basin
to be offline) without ponding in the splitter structure or creating backwater upstream ofthe
splitter.
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• Base flow should not be present in the tributary watershed.
Secondary Screening Based on Site Geotechnical Investigation
a At least three in-hole conductivity tests shaU be performed using USBR 7300-89 or Bouwer-
Rice procedures (the latter if groundwater is encountered within tlw boring), two trats at
different locations within the proposed basin and the third down gradient by no more than
approxunately to m. The tests shall measure penneability in the side slopes and the bed
within a depth of 3 m of the invert.
• Hie minimum acceptable hydraulic conductivity as measured in any of the three required
lest holes is 13 mm/hr. If any test hole shows less than the minimum value, the site should
be disqualified frotn further consideration.
« Exclude from consideration sites constructed in fill or partially in fill unless no silts or clays
are present in the soil boring. Fill tends to be compacted, with clays in a dispersed rather
than flocculated state, greatly reducing permeability,
• The geotechnical investigation should be such that a good understanding is gained as to how
the stormwater runoff will move in the soil (horizontally or vertically) and if there are any
geological conditions that could inhibit the movement of water.
Additional Design Guidelines
(1) Basin Sizing - The required water quality volume is determined by local regulations
or sufficient to capture 85% of the annual wnoff.
(2) Provide pretreatment if sediment loading is a maintenance concem for the basin.
(3) Include energy dissipation in the inlet design for the basins. Avoid designs that
include a permanent pool to reduce opportunitj- for standing water and associated
vector problems.
(4) Basin invert area should be determined by the etjuation;
WQV
where A = Basin invert area (m^)
WQV " water quality volume (ma)
k = 0.5 tunes the lowest field-measvired hydraulic conductivity
(m/hr)
t = dravwiown time (48 hr)
(5) The use of vertical piping, either for distribution or infiltration enhancement shall
nol be allowed to avoid device classification as a Class V injection well per 40
CFRi46.5{e)(4)-
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Maintenance
Regular maintenance is critical to liie successlnl operation of infiltratton basins. Recommended
operation and maintenance guidelines include:
« Inspections and maintenance to ensure.
• Observe drain time for the design storm after completion or modification of tlie fadlity to
confirm that the desired drain time has been obtained.
a Schedule semiannual uispections for beginning and end of the wet season to identify
potential problems such as erosion of the basin side slopes and invert, standing water, trash
and debris, and sediment accumulation.
• Remove accumulated trash and debris in the basin at the start and end of the wet season,
• Inspect for standi ng water at the end of the wet season.
• Trim vegetation at the beginning and end of the wet season to prevent establishment of
woody vegetation and for aesthetic and vector reasons.
• Remove accumulated sediment and regrade when the accumulated sediment volume
exceeds io% of the basin.
• If erosion is occurring within the basin, revegetate immediately and stabilize with an erosion
control mulch or mat until vegetation cover is established.
• To avoid reversing soil development, scarification or other disturbance should only be
performed when there are actual signs of clogging, rather than on a routine basis. Always
remove deposited sediments before scarification, and use a hand-guided rotary tiller, if
possible, or a disc harrow pulled by a very light tractor.
Cost
Infiltration basins are relatively cost-effective practice* because little infrastructure is needed
when constructing them. One study estimated the total construction cost at about $2 per ft
(adjusted for inflation) of storage for a 0.25-acre basin (SWRPC, 1991). As vrith other BMPs,
these published cost estimates may deviate greatly firom what might be incuiTcd at a specific
site. For instance, Caltrans spent about $18/ft^ for the two infiltration basins constructed in
southern Califoraia, eacli of which had a water quality volume of about 0.34 ac-ft. Mueb of the
higher cost can be attributed to changes in the stom drain system necessary to route the mnoff
to the basin locations.
Infiltration basins typically consume about 2 to 3% ofthe site draining to them, which is
relatively small. Additional space may be required for buffer, landscaping, access road, and
fencing. Maintenance costs are estimated at 5 to io?6 of construction costs.
One cost concern associated with infiltration practices is the maintenance burden and longevity.
If improperiy maintamed, infiltration basins have a high failure rate. Thus, it may be necessary
to replace the basin wilh a different technology after a relatively short period of time.
January 2003 California Stormwater BMP Handbook 5 of 8
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TC-11 Infiitration Basin
References and Sources of Additional Information
Caltrans, 2002, BMP Retixjfit Pilot Program Proposed Finai Report, Rpt. CTSW-RT-oi-050,
California Dept. of Transportation, Sacramento, CA.
Gall), J. 1992. Analysis of Urban BMP Perfonnance and Longevity in Pfinee George's County,
Maryland. Metropolitan Washington Council of Governments, Washinglon, DC.
Hilding, K. 1996. Longevity of infiltration basins assessed in Puget Sound. Watershed Protection
Techniques i{3):ia4-i25.
Maryland Department ofthe Environment (MDE). 2000, Maryland Stormtoater Design
Manual. http://wwWrmde.State.md.us/environment/vmia/stormwatermanHal. Accessed May
22, aoo2.
NRghtingale, H.I., 1975, 'Lead, Zinc, and Copper in Soils of Urban Storm-Runoff Retention
Basins." American Water Works Assoc. Journal. Vol. 67, p, 443-446.
Nightingale, H.L, 1987a, "Water Quality beneath Urban Runoff Water Management Basins,"
Water Resources Bulletin, Vol 23, p, 197-205.
Nightingale, H.I.. 1987b, "Accumulation of As, Ni, Cu, and Pb in Retention and Recharge Basin
Soils fi'om Urban Runoff," Water Resources Bulletin, Vol, 23, p. 663-672,
Nightingale, H.L, 1987c, "Organic Pollutants in Soils of Retention/Recharge Basins Receiving
Urban Runoff Water," Soil Science Vol, 148. pp. 39-45.
Nightingale, H.I., Harrison, D.. and Salo, J.E., 1985, "An Evaluation Technique for Ground-
water Quality Beneath Urban Runoff Retention and Percolation Basins," Ground Water
Monitoring Review, Vol 5, No, 1, pp. 43-50.
Oberts, G. 1994. Performance of Stormwater Ponds and Wetlands in Winter. Watershed
Protection Techniques 1(2): 64-68.
Pitt, R,, et al. 1994, Potential Groundwater Contamination from Intentional and
Nonintentional Stormwater Infiltration, E?A/6oo/R'94/05i, Risk Reduction Engineering
Laboratory, U.S. EPA, Cincinnati, OH.
Schueler, T. 1987. Controlling Urban Runoff: A Practical Manualfor Planning and Designing
Urban BMPs. Metropolitan Washington Coundl of Govemments, Washington, DC.
Schroeder, RA., 1995, Potential For Chemicai Transport Beneath a Storm-Runoff Recharge
(Retention) Basin for an Industrial Catchment in Fresno, CA, USGS Water-Resource
Investigations Report 93-4140.
Southeastem Wisconsin Regional Planning Commission (SWRPC), 1991. Costs of Urban
Nonpoint Source Water PoUution Control Measures. Southeastern Wisconsin Regional
Planning Commission, Waukesha, WI.
U.S. EPA, 1983, Results ofthe Nationwide Urban Runoff Program: Volume 1 - Final Report,
WH-554. Water Planning Division. Washington, DC.
^ of 8 California Stormwater BMP Handbook Januarv 2D03
New Development and Redeveiopment
www.cabmptiandbooks.com
Ponto Vision EIR: JN 25-101951
Storm Water Mitigation Plan
Infiitration Basin TC-11
Watershed Management Institute (WMl). 1997. Operation, Maintenance, and Management of
Stormwater Management Systems. Prepared for U-S. Environmental Protection Agency Ofiice
of Water, Washington, DC.
Itlformatitm Resoitreea
Center for Watershed Protection (CWP), 1997. Stormwater BMP Design Supplementfor Cold
aimates. Prepared for U.S. Envux)nmental Protection Agency Office of Wetlands, Oceans and
Watersheds. Washington, DC.
Ferguson, B.K., 1994, Stormwater Infiltration. CRC Press, Ann Arbor, Ml.
USEPA. 1993. Guidance to Specify Management Measures for Sources ofNonpoint Pollution in
Coastal Waters. EPA-840-B-92-002. U.S. Environmental Protection Agency, Oflice of Water
Washington, DC.
January 2003 CaHfbmla Stomiweter BMP Handbook 7 of 8'
New Devetapmeflt and Redevelopment
WWW.cabmphandbooks.com
Ponto Vision EIR: JN 25-101951
Storm Water Mitigation Plan
TC-11 Infiitration Basin
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Ponto Vision EIR: JN 25-101951
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Appendix C Pre-Development Hydrology