HomeMy WebLinkAboutCT 05-21; GREYHAWK BUSINESS PARK; PRELIMINARY STORM WATER MANAGEMENT PLAN; 2010-02-02PRELIMINARY STORM WATER
MANAGEMENT PLAN
For
STATE STREET CONDOS
Prepared: March 11, 2009
Updated: February 2, 2010
JN: 051117-5
Prepared by:
O'DAY CONSULTANTS, INC.
2710 Loker Avenue West, Suite 100
Carlsbad, California 92010-6609
Tel: (760) 931-7700
Fax: (760) 931-8680
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PRELIMINARY STORM WATER MANAGEMENT PLAN
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STATE STREET CONDOS
Exp. 12/31/10
I TABLE OF CONTENTS
ITEM PAGE
COVER SHEET.......................................................................................i
TABLE OF CONTENTS............................................................................ii I 1.0 INTRODUCTION .......................................................................... 1
1.1 PURPOSE.........................................................................1
1.2 LOCATION ....................................................................... 1 I 2.0 PROJECT REVIEW & PERMITTING PROCESS....................................2
2.1 DETERMINE APPLICABLE STORM WATER BMP
I REQUIREMENTS...............................................................2
2.2 PRIORITY PROJECT PERMANENT STORM WATER BMP
REQUIREMENTS...............................................................2
I 3.0 PREPARE AND SUBMIT APPROPRIATE PLANS.................................2
3.1 REQUIRED BMP ELEMENTS................................................2
4.0 PERMANENT BEST MANAGEMENT PRACTICES SELECTION.............2
I 4.1 IDENTIFY POLLUTANTS FORM THE PROJECT AREA............2
1.1 ANTICIPATED POLLUTANTS OF CONCERN...............3
4.1.2 POTENTIAL POLLUTANTS OF CONCERN...................3
I 4.2 IDENTIFY POLLUTANTS OF CONCERN IN RECEIVING
WATERS..........................................................................3
4.2.1 IDENTIFY THE HYDROLOGIC UNIT CONTRIBUTION... 3
I 4.2.2 IDENTIFY 303(d) IMPAIRMENTS IN THE RECEIVING
WATERS...............................................................3
4.3 BENEFICIAL USES OF RECEIVING WATERS..........................3
I 4.3.1 BIOL - PRESERVATION OF BIOLOGICAL HABITATS
OF SPECIAL SIGNIFICANCE.....................................3
4.3.2 REC1 - CONTACT RECREATION...............................3
I 4.3.3 REC2 - NON-CONTACT RECREATION........................4
4.3.4 EST - ESTUARINE HABITAT....................................4
4.3.5 MAR - MARINE HABITAT.......................................4
I 4.3.6 WILD - WILDLIFE HABITAT....................................4
4.3.7 RARE - RARE, THREATENED, OR ENDANGERED
SPECIES...............................................................4
1 4.3.8 MIGR - MIGRATION OF AQUATIC ORGANISMS..........4
4.4 IDENTIFY CONDITIONS OF CONCERN.................................4
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5.0 ESTABLISH PERMANENT STORM WATER BEST MANAGEMENT
PRACTICES................................................................................5
5.1 SITE DESIGN BMPS...........................................................5
I CHARACTERISTICS.................................................5
1.1 MAINTAIN PRE-DEVELOPMENT RAINFALL RUNOFF
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TABLE OF CONTENTS (CONTINUED)
ITEM PAGE
5.1.2 MINIMIZE IMPERVIOUS FOOTPRINT........................5
5.1.3 CONSERVE NATURAL AREAS.................................5
5.1.4 MINIMIZE DIRECTLY CONNECTED IMPERVIOUS
AREAS..................................................................5
5.1.5 MAXIMIZE CANOPY INTERCEPTION AND WATER
CONSERVATION CONSISTENT WITH THE CARLSBAD
LANDSCAPE MANUAL............................................6
5.2 SOURCE CONTROL BMPS 6
5.2.1 DESIGN OUTDOOR MATERIAL STORAGE AREAS TO
REDUCE POLLUTION INTRODUCTION......................6
5.2.2 DESIGN TRASH STORAGE ARES TO REDUCE
POLLUTION INTRODUCTION...................................6
5.2.3 USE EFFICIENT IRRIGATION SYSTEMS AND
LANDSCAPE DESIGN..............................................7
5.2.4 PROVIDE STORM WATER CONVEYANCE SYSTEM
STENCILING AND SIGNAGE....................................7
5.3 INDIVIDUAL PRIORITY PROJECT CATEGORIES.....................7
5.4 TREATMENT CONTROL BMPS............................................7
5.4.1 TREATMENT CONTROL BMP DESIGN STANDARDS 8
5.4.2 TREATMENT CONTROL BMP SELECTION...............8
5.4.3 POLLUTANTS OF CONCERN....................................8
5.4.4 STRUCTURAL TREATMENT CONTROL BMP
SELECTION...........................................................9
5.4.5 TREATMENT CONTROL BMP INFORMATION.............9
5.4.6 STRUCTURAL TREATMENT LIMITED EXCLUSIONS 9
5.5 PERMANENT BMPS APPLICABLE TO THE PROJECT SITE........9
6.0 CONSTRUCTION STORM WATER BMPS..........................................10
7.0 IMPLEMENTATION & MAINTENANCE REQUIREMENTS..................10
7.1 OPERATION AND MAINTENANCE PLAN..............................10
7.2 ACCESS EASEMENT/AGREEMENT.......................................10
8.0 APPENDICES..............................................................................11
APPENDIX A: VICINITY MAP
APPENDIX B: STORM WATER STANDARDS QUESTIONNAIRE
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TABLE OF CONTENTS (CONTINUED)
ITEM PAGE
APPENDIX C: CITY OF CARLSBAD STANDARDS EXCERPTS
TABLE 1: STANDARD DEVELOPMENT PROJECT & PRIORITY PROJECT STORM
WATER BMP REQUIREMENTS MATRIX
TABLE 2: ANTICIPATED AND POTENTIAL POLLUTANTS GENERATED BY
LAND USE TYPE
TABLE 3: NUMERIC SIZING TREATMENT STANDARDS
TABLE 4: STRUCTURAL TREATMENT CONTROL BMP SELECTION MATRIX
APPENDIX B: DRAFT ENVIRONMENTALLY SENSITIVE AREAS WITHIN THE
CITY OF CARLSBAD MAP
APPENDIX D: PRELIMINARY HYDROLOGY STUDY
I . 'PRELIMINARY HYDROLOGY STUDY FOR STATE STREET CONDOS'
PREPARED BY O'DAY CONSULTANTS, INC DATED FEB. 11, 2009
I APPENDIX E: BENEFICIAL USES OF RECEIVING WATERS
APPENDIX F: 2006 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED
I SEGMENTS
APPENDIX G: SOURCE CONTROL BMP FACT SHEETS
I . CITY OF CARLSBAD GS-16: REFUSE BIN ENCLOSURES
CASQA SD-10: SITE DESIGN AND LANDSCAPE PLANNING
CASQA SD-11: ROOF RUNOFF CONTROLS I . CASQA SD-12: EFFICIENT IRRIGATION
CASQA SD-32: TRASH ENCLOSURES
APPENDIX H: TREATMENT CONTROL BMP FACT SHEETS
CASQA TC-32: BIORETENTION
. SECTION 6: LONG-TERM MAINTENANCE OF BMPS
APPENDIX I: APPLICABLE MANUFACTURER'S BMP INFORMATION
APPENDIX J: MAP EXHIBITS
PRELIMINARY STORM WATER MANAGEMENT PLAN BMP EXHIBIT
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1.0 INTRODUCTION
Federal, state and local agencies have established goals and objectives for storm water
quality in the region. The proposed project is a priority project as defined in Order No.
2007-01 by the San Diego Region of the California Water Quality Control Board. As a
result, the project is subject to SUSMP requirements. In addition, prior to the start of
construction activities, the project will comply with all federal, state and local permits
including the Stormwater Management Plan (SWMP) required under the County of San
Diego Watershed Protection, Stormwater Management, and Discharge Control Ordinance
(WPO) (section 67.87 1), the City of Carlsbad's Standard Urban Storm Water Mitigation
Plan, and the National Pollution Discharge Elimination System (NPDES) from the
Regional Water Quality Control Board (RWQCB).
The purpose of this SWMP is to address the water quality impacts from the proposed
improvements as shown on the Tentative Map. This report will provide guidelines in
developing and implementing post construction Best Management Practices (BMPs) for
storm water quality.
The proposed developed condition for State Street Condos as shown on the Tentative
Map consists of two multi-unit buildings being constructed on the north and south ends of
the site with a drive aisle in the middle. A total of 9 residential units are being proposed.
A majority of the runoff will flow via sheet flow and through roof drains into landscape
areas and then continue to sheet flow to the gutter.
1.1 PURPOSE
This Storm Water Management Plan has been written to the standards set forth in
the City of Carlsbad Engineering Standards, Volume 4: Storm Water Standards
Manual (BMPs) (2008 Edition). This report will reference these standards as
'City Standards.'
1.2 LOCATION
The project is located according to the vicinity map found in Appendix A.
2.0 PROJECT REVIEW & PERMITTING PROCESS
In order to complete the Project Review & Permitting Process section of the City
Standards the Storm Water Standards Questionnaire has been completed. For reference,
this document has been included in Appendix B: Storm Water Standards Questionnaire.
2.1 DETERMINE APPLICABLE STORM WATER BMP
REQUIREMENTS
Based on the completed Storm Water Standards Questionnaire completed for the
project (see Appendix B: Storm Water Requirements Applicability Checklist) the
following requirements apply to the project:
2.2 PRIORITY PROJECT PERMANENT STORM WATER BMP
REQUIREMENTS
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Based on Section 1: New Development of the Storm Water Standards
Questionnaire, the project meets priority requirements.
Since the project is subject to priority project standards the design should
incorporate all applicable requirements identified in Sections 2.3.3 'Establish
Permanent Storm Water Best Management Practices' per the City Standards.
This should include Low Impact Development (LID) site design and source
control BMPs; BMPs applicable to individual priority projects; and treatment
control BMPs. Further guidance on these requirements can be found on page 10
of the City Standards.
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I 3.0 PREPARE AND SUBMIT APPROPRIATE PLANS
Based on the general categories of storm water requirements that are applicable to the
project as described in section 2, the following categories from Table 1: Standard
I Development Project & Priority Project Storm Water BMP Requirements Matrix found
on page 6 of the City Standards apply:
I 3.1 REQUIRED BMP ELEMENTS
The following are required BMP elements for the project and one or more
applicable BMPs must be utilized:
I • Site Design BMPs
• Source Control BMPs
Applicable to Individual Priority Projects
I o Surface Parking Areas
Treatment Control BMPs
4.0 PERMANENT BEST MANAGEMENT PRACTICES SELECTION
This section will identify what permanent best management practices will apply to
project:
4.1 IDENTIFY POLLUTANTS FROM THE PROJECT AREA
Based on the general pollutant categories and project categories as described in
Table 2: Anticipated and Potential Pollutants Generated by Land Use Type found
on page 8 of the City Standards, the project has the following pollutants:
4.1.1 ANTICIPATED POLLUTANTS OF CONCERN
The following are anticipated pollutants of concern for the project:
Heavy Metal
Organic Compounds (petroleum hydrocarbons)
Trash & Debris
Oil & Grease
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4.1.2 POTENTIAL POLLUTANTS OF CONCERN
The following are potential pollutants of concern for the project:
Sediment
Nutrients (due to landscaping)
Oxygen Demanding Substances (due to landscaping)
Pesticides (due to landscaping)
4.2 IDENTIFY POLLUTANTS OF CONCERN IN RECEIVING
WATERS
This section will identify the pollutants or concern, if any, in the receiving waters
of the project proposed drainage pattern.
4.2.1 IDENTIFY THE HYDROLOGIC UNIT CONTRIBUTION
The State Street Condos project is located in the Buena Vista Hydrologic
Subarea (904.21) of the Carlsbad Hydrologic Unit in the San Diego
Region.
4.2.2 IDENTIFY 303(d) IMPAIRMENTS IN THE RECEIVING
WATERS
I In the 2006 CW Section 303(d) List of Water Quality Limited Segments,
the Buena Vista Lagoon is impaired for bacteria indicators, nutrients, and
sedimentation/siltation. Portions of Carlsbad where construction sites
I have the potential to discharge into a tributary of a 303(d) or directly into a
303(d) water body or sites located within 200 feet of an ESA require
additional BMP implementation.
4.3 BENEFICIAL USES OF RECEIVING WATERS I The beneficial uses for the hydrologic unit are included in Appendix E and a
summary of the applicable definitions are listed below. This information comes
I from the Water Quality Control Plan for the San Diego Basin.
4.3.1 BIOL - PRESERVATION OF BIOLOGICAL HABITATS OF
I SPECIAL SIGNIFICANCE
This beneficial use includes uses of water that support designated areas or
habitats, such as established refuges, parks, sanctuaries, ecological
I reserves, or Areas of Special Biological Significance (ASBS), where the
preservation or enhancement of natural resources requires special
protection.
1 4.3.2 REC-1 CONTACT RECREATION
This beneficial use includes uses of water for recreational activities
I involving body contact with water, where ingestion of water is reasonably
possible. These uses include, but are not limited to, swimming, wading,
water-skiing, skin and SCUBA diving, surfing, white water activities,
fishing, or use of natural hot springs.
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4.3.3 REC-2 - NON-CONTACT RECREATION
I This beneficial use includes the uses of water for recreational activities
involving proximity to water, but not normally involving body contact
with water, where ingestion of water is reasonably possible. These I include, but are not limited to, picnicking, sunbathing, hiking, camping,
boating, tide pool and marine life study, hunting, sightseeing, or aesthetic
I enjoyment in conjunction with the above activities.
4.3.4 EST - ESTUARINE HABITAT
I This beneficial use includes the uses of water that support estuarine
ecosystems including, but not limited to, preservation or enhancement of
estuarine habitats, vegetation, fish, or wildlife (e.g., estuarine mammals,
I waterfowl, shorebirds).
4.3.5 MAR - MARINE HABITAT
I This beneficial use includes uses of water that support marine ecosystems
including, but not limited to, preservation or enhancement or marine
habitats, vegetation such as kelp, fish, shellfish, or wildlife (e.g., marine
I mammals, shorebirds).
4.3.6 WILD - WILDLIFE HABITAT
I This beneficial use includes uses of water that support terrestrial
ecosystems including but not limited to, preservation and enhancement of
terrestrial habitats, vegetation, wildlife, (e.g., mammals, birds, reptiles,
I amphibians, invertebrates), or wildlife water food and sources.
4.3.7 RARE - RARE, THREATENED, OR ENDANGERED
I SPECIES
This beneficial use includes uses of water that support habitats necessary,
at least in part, for the survival and successful maintenance of plant or
I animal species established under state or federal law as rare, threatened or
endangered.
I 4.3.8 MIGR —MIGRATION OF AQUATIC ORGANISMS
This beneficial use includes uses of water that support habitats necessary
for migration, acclimatization between fresh and salt water, or other
I temporary activities by aquatic organisms, such as anadromous fish.
I 4.4 IDENTIFY CONDITIONS OF CONCERN
In order to determine if the project proposed drainage patterns will affect the
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downstream conditions, a copy of the project's Preliminary Drainage Study is
including in Appendix D: Site Drainage Study. This report is title 'Preliminary
Hydrology Study for State Street Condos, March 11, 2009. Based on the findings
in this Preliminary drainage study, the onsite water will be treated per this report.
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5.0 ESTABLISH PERMANENT STORM WATER BEST MANAGEMENT
PRACTICES
Because the project is a Priority Project, all the applicable BMPs will be applied to the
project. Where applicable, the project will incorporate storm water BMPs in the project
design in the following progression:
Site Design BMPs
Source Control BMPs
Individual Project BMPs
Treatment Control BMPs
5.1 SITE DESIGN BMPS (LOW IMPACT DEVELOPMENT)
Site Design BMPs are comprised of the following BMPS:
Maintain Pre-Development Rainfall Runoff Characteristics
Minimize Impervious Footprint
Minimize Directly Connected Impervious Areas
Maximize Canopy Interception and Water Conservation
Consistent with the Carlsbad Landscape Manual
I 5.1.1 MAINTAIN PRE-DEVELOPMENT RAINFALL RUNOFF
CHARACTERISTICS
This Site Design BMP entails controlling post construction peak storm I water discharge at the rate and velocities of the pre-developed condition.
5.1.2 MINIMIZE IMPERVIOUS FOOTPRINT
This Site Design BMP and L.I.D. requirement entails minimizing the
proposed site impervious footprint through increasing building densities,
utilizing pervious construction materials on walkways, driveways, trails,
patios, overflow parking areas, alleys and low traffic areas. Examples of
materials that can be used are pervious concrete, porous asphalt, unit
payers, and granular materials. In addition, streets, sidewalks, and parking
lot aisles can be designed to minimum widths, provided pedestrian safety
is not compromised. And lastly, this can be accomplished through the
minimization of use of impervious surfaces, such as decorative concrete in
landscape design. The proposed design of the project will attempt to
utilize this Site Design BMP by minimizing the impervious footprint to
the maximum extent practicable.
5.1.4 MINIMIZE DIRECTLY CONNECTED IMPERVIOUS
AREAS
This Site Design BMP entails minimizing directly connected impervious
areas where landscaping is proposed to direct runoff from impervious
surfaces such as sidewalks, parking lots, walkways, and patios to
landscaping areas. An example of this is tying the area.drains from the
upper deck into a single system that will outlet into the landscape area at
the ground level.
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5.1.5 MAXIMIZE CANOPY INTERCEPTION AND WATER
CONSERVATION CONSISTENT WITH THE CARLSBAD
LANDSCAPE MANUAL
This Site Design BMP entails maximizing canopy interception and water
conservation consistent with the Carlsbad Landscape Manual to preserve
existing native trees and shrubs, to plant additional native or drought
tolerant trees, and to plant large shrubs in place of non-drought tolerant
exotic species. The project will utilize this Site Design BMP by having
the landscaping designer utilize the applicable City of Carlsbad Landscape
Manual and any other applicable City of Carlsbad Standards.
5.2 SOURCE CONTROL BMPS
Source Control BMPs are comprised of the following BMPS:
Design Outdoor Material Storage Areas to Reduce Pollution
Introduction
Design Trash Storage Areas to Reduce Pollution Introduction
Use Efficient Irrigation Systems and Landscape Design
Provide Storm Water Conveyance System Stenciling and Signage
5.2.1 DESIGN OUTDOOR MATERIAL STORAGE AREAS TO
REDUCE POLLUTION INTRODUCTION
This Source Control BMP entails placing any and all potentially hazardous
materials that have a potential to contaminate urban runoff in storage areas
on site that are enclosed in structures such as, but not limited to, cabinets,
sheds, or other similar structures that prevent and contain with rain, runoff,
or spillage. In addition, secondary structures such as berms, dikes, or
curbs will be utilized out side of the storage structure to further prevent
contamination. The storage areas shall be paved with a sufficiently
impervious material to contain leaks and spills, and shall have a roof or
awning to minimize direct contact with precipitation within the secondary
containment area. Because the project does not proposed any material
storage areas this Source Control BMP will not be utilized.
5.2.2 DESIGN TRASH STORAGE AREAS TO REDUCE
POLLUTION INTRODUCTION
This Source Control BMP entails designing trash storage areas to reduce
pollution introduction. Trash Storage Areas shall be paved with an
impervious surface, designed not to allow runoff from adjoining areas,
screened or wailed to prevent off-site transportation of trash, and contain
attached lids on all trash containers that protects them from precipitation.
Alternatively, the trash enclosure can contain a roof or awning to
minimize direct contact with precipitation. The project will utilize this
Source Control BMP by designing and building the trash torage areas
according to the City of Carlsbad Standard Drawing GS-16 and in
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accordance with CASQA SD-32: Trash Enclosures. These areas will be
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paved with an impervious surface, graded to drain away from the
enclosure, and screened and walled to prevent off-site transport of trash.
Trash containers will contain attached lids that exclude rain to minimize
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direct precipitation. A copy of each of these is provided in Appendix G.
5.2.3 USE EFFICIENT IRRIGATION SYSTEMS AND
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LANDSCAPE DESIGN
This Source Control BMP entails employing rain shutoff devices to
prevent irrigation during precipitation and this requires all landscaping
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aspects to be designed per the Carlsbad Landscape Manual. The project
will utilize this Source Control BMP by having the landscaping designer
utilize the applicable City of Carlsbad Landscape Manual and any other
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applicable City of Carlsbad Standards. In addition, site irrigation will also
be designed in accordance with CASQA SD-10: Site Design and
Landscape Planning. A copy of this has been provided in Appendix G.
1 5.2.4 PROVIDE STORM WATER CONVEYANCE SYSTEM
STENCILING AND SIGNAGE
I This Source Control BMP entails providing storm drain conveyance
system stenciling and signage. This shall be done by providing concrete
stamping, porcelain tile, insert permanent marking or approved equivalent
I as approved by the City of Carlsbad, of all storm drain conveyance system
inlets and catch basins within the project area with prohibitive language
(i.e. "No Dumping - I Live Downstream') satisfactory to the City
I Engineer. In addition, signs shall be posted and prohibitive language
and/or graphical icons, which prohibit illegal dumping at public access
points along channels and creeks within the project area, trailheads, and
I parks shall be used. The project will utilize this Source Control BMP by
utilizing CASQA SD-13: Storm Drain Stenciling. A copy of this is
provided in Appendix G.
I 5.3 INDIVIDUAL PRIORITY PROJECT CATEGORIES
Where identified in Table 1 of the City Standards, the following requirements
I shall be incorporated into priority projects: Surface Parking Areas. Surface
parking areas (covered and uncovered) where landscaping is proposed shall
incorporate landscape areas into the drainage design. The project will utilize this
I Individual Priority Project Category BMP by incorporating the proposed
landscaping areas in the drainage pattern as much as feasibly possible. ' 5.4 TREATMENT CONTROL BMPS
Where identified in Table 1 of the City Standards, and after site design and source
control BMPs have been incorporated into the project design, treatment control
BMPs may then be utilized.
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5.4.1 TREATMENT CONTROL BMP DESIGN STANDARDS
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Treatment Control BMPs shall be designed to infiltrate, filter, and/or treat
runoff from the project footprint per Table 3: Numeric Sizing Treatment
Standards. A copy of Table 3 is provided in Appendix C. There are four
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guidelines that need to be followed for Treatment Control BMPs:
All Structural Treatment Control BMPs shall infiltrate, filter,
and/or treat the required runoff volume or flow prior to
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discharging to any receiving water body supporting beneficial
uses.
Multiple post construction Structural Treatment Control BMPs
I for a single priority project shall collectively be designed to
comply with the numeric sizing treatment standards.
Shared BMPs shall be operational prior to the use of any
I dependent development or phase of development. The shared
BMPs shall only be required to treat the dependent
developments or phases of development that are in use.
I . Interim storm water BMPs that provide equivalent or greater
treatment than is required may be implemented by a dependant
development until each shared BMP is operational. If interim
I BMPs are selected, the BMPs shall remain in use until
permanent BMPs are operational.
I 5.4.2 TREATMENT CONTROL BMP SELECTION
All projects classified as Priority Projects in the City of Carlsbad shall
select a single or combination of treatment control BMPs from the
I categories listed in Table 4: Structural Treatment Control BMPs Selection
Matrix. A copy of Table 4 is provided in Appendix C. This selection
matrix will determine the most efficient removal BMP for the pollutants of
I concern from the project site. The most efficient device or combination of
devices shall be utilized to maximize pollutant removal.
I 5.4.3 POLLUTANTS OF CONCERN
Based on the above findings for the proposed site usage the project has the
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following pollutants of concern:
Sediment (Anticipated)
Nutrients (Potential by use)
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. Heavy Metals (Anticipated)
Organic Compounds (Anticipated)
Trash & Debris (Anticipated)
Oxygen Demanding Substances (Potential by use) 1 .
Oil & Grease (Anticipated)
Pesticides (Potential by use)
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The other pollutants of concern have not been accounted for because the
project landscaping will be designed and installed per the City of Carlsbad I Landscape Manual and will incorporate efficient irrigation, pest resistant
species, and incorporate drought resistant native species of planting.
1 5.4.4 STRUCTURAL TREATMENT CONTROL BMP
SELECTION
Based on the pollutants of concern present from the project site and the I removal efficiencies listed in Table 4: Structural Treatment Control BMP
Selection Matrix, the Structural Treatment Control BMP with the most
efficient removal efficiencies for the project is as follows (listed most to I least efficient):
I . Bioretention (see Appendix J for sizing calculations)
Based on the above mentioned removal efficiencies and limited space on
site, the project shall incorporate a combination of biofilters on site. I Higher removal efficient structural treatment control devices could not be
used on site due to the limited space to accommodate their proper design
and implementation.
5.4.5 STRUCTURAL TREATMENT LIMITED EXCLUSIONS I No Structural Treatment Limited Exclusions apply to this project as
defined in the City Standards.
1 5.5 PERMANENT BMPS APPLICABLE TO THE PROJECT SITE
Based on the above findings, the following permanent BMPs will be established
I for the project:
Site Design BMPs:
I . Maintain Pre-Development Rainfall Runoff Characteristics
Minimize Impervious Footprint
Minimize Directly Connected Impervious Areas
I a Maximize Canopy Interception and Water Conservation
Consistent with the Carlsbad Landscape Manual
Source Control BMPs: I . Design Trash Storage Areas to Reduce Pollution Introduction
Use Efficient Irrigation Systems and Landscape Design
Provide Storm Water Conveyance System Stenciling and Signage
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6.0 CONSTRUCTION STORM WATER BMPS
Based on the size of the project site the City of Carlsbad will require that a separate
document be prepared. If the project site is less then one acre then the project will
require a Water Pollution Control Plan. If the project site is one acre of more then a
Storm Water Pollution Prevention Plan will be required. Since the project has a disturbed
area more than one acre a SWPPP will be required. Construction BMPs and any
applicable design standards can be found in this separate document.
7.0 IMPLEMENTATION & MAINTENANCE REQUIREMENTS
Once the City of Carlsbad approves all the project BMPs, the applicants and the City
Project Managers must ensure proper implementation of the selected BMPs. In order to
accomplish effective implementation and maintenance the City of Carlsbad may require
that some sort of Permanent BMP Maintenance Agreement be entered into. This will be
at the discretion of the City of Carlsbad Staff. In the event that a Permanent BMP
Maintenance Agreement is required by City Staff, the following items will need to be
addressed:
7.1 OPERATION AND MAINTENANCE PLAN
The applicant shall include and Operation & Maintenance Plan (O&M), prepared
satisfactory to the City, with the approved maintenance agreement, which
describes the designated responsible party to mange the storm water BMPs,
employee's training program and duties, operating schedule, maintenance
frequency, routine service schedule, specific maintenance activities (including
maintenance of storm water conveyance system stamps), copies of resource
agency permits, and any other necessary activities. At a minimum, maintenance
agreements shall require the applicant to provide inspection and servicing of all
permanent treatment BMPs on an annual basis. The project proponent or City-
approved maintenance entity shall complete and maintain O&M forms to
document all maintenance requirements. Parties responsible for the O&M plan
shall retain records for at least 5 years. These documents shall be made available
to the City inspector upon request at any time. In addition, CASQA Section 6:
Long-term Maintenance of BMPs shall be utilized as guide. A copy of this is
provided in Appendix H.
7.2 ACCESS EASEMENT/AGREEMENT
If a permanent BMP requires access for maintenance, as part of the O&M plan,
the applicant shall execute and record an access easement or agreement that shall
be binding on the under lying land throughout the life of the project in favor of the
party responsible for maintenance, until such time that the permanent treatment
BMP requiring access for maintenance is removed or replaced. The City shall
approve any changes to the permanent BMPs, O&M plans, or access agreements.
The agreement shall include a provision that gives the City the right, but not the
obligation to perform the maintenance. The party responsible for BMP
maintenance will pay the City for any and all costs uncured by the City for
maintaining any BMPs. The agreement will provide a cost recovery provision in
favor of the City satisfactory to the City Attorney.
I -10-
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PRELIMINARY STORM WATER MANAGEMENT PLAN
STATE STREET CONDOS
8.0 APPENDICES:
The following Appendices are included:
Appendix A: Vicinity Map
Appendix B: Storm Water Standards Questionnaire
Appendix C: City of Carlsbad Standards Excerpts
Table 1: Standard Development Project & Priority Project Storm
Water BMP Requirements Matrix
Table 2: Anticipated and Potential Pollutants Generated by Land Use
Type
Table 3: Numeric Sizing Treatment Standards
Table 4: Structural Treatment Control BMP Selection Matrix
Appendix B: Draft Environmentally Sensitive Areas Within the City
of Carlsbad Map
Appendix D: Site Drainage Study
I • Preliminary Hydology Study for State Street Condos by O'Day
Consultants, Inc date March 11, 2009.
I Appendix E: Beneficial Uses of Receiving Waters
I Appendix F: 2006 CWA Section 303(d) List of Water Quality Limited Segments
Appendix G: Source Control BMP Fact Sheets
I Carlsbad Standard Drawing GS-16: Refuse Bin Enclosures
CASQA SD-10: Site Design and Landscape Planning
CASQA SD- 11: Roof Runoff Controls
CASQA SD-12: Efficient Irrigation I CASQA SD-32: Trash Enclosures
I Appendix H: Treatment Control BMP Fact Sheets
CASQA TC-32: Bioretention
Section 6: Long-term Maintenance of BMPs
Appendix I: Applicable Manufacturer's BMP Information
Appendix J: Map Exhibits
State Street Condos Storm Water Management Plan BMPs Exhibit
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PRELIMINARY STORM WATER MANAGEMENT PLAN
STATE STREET CONDOS
APPENDIX A: VICINITY MAP
CITY OF OCEANSIDE
d- CITY OF VISTA
SITE :
CIT OF 1- ROAD
PALOMAR \?O
5 Id PACIFIC ° ('A D CD A fl CITY OF I \ ) L) /\ LI SAN MARCOS OCEAN % y r
.....
COSTA AVE
CITY OF ENCINITAS
VICINITY A/A?
NO SCALE
I STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
APPENDIX B: STORM WATER STANDARDS QUESTIONNAIRE
I Please see attached.
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CITY OF
CARLSBAD
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Development Services
Engineering Department
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
a4 r-e
I
TiTRUCTIONS:
This questionnaire must be completed by applicant in advance of submitting for a development application (subdivision
and land use planning approvals and construction permits). The results of the questionnaire determine the level of
I storm water pollution prevention standards applied to a proposed development or redevelopment project. Many
aspects of project site design are dependent upon the storm water pollution protection standards applied to a project.
Applicant responses to the questionnaire represent an initial assessment of the proposed project conditions and
I impacts. City staff has responsibility for making the final assessment after submission of the development application.
A staff determination that the development application is subject to more stringent storm water standards than initially
assessed by the applicant, will result in the return of the development application as incomplete.
I ll applicants are unsure about the meaning of a question or need help in determining how to respond to one or more of
the questions, they are advised to seek assistance from Engineering Department Development Services staff.
I A separate completed and signed questionnaire must be submitted for each new development application submission.
Only one completed and signed questionnaire is required when multiple development applications for the same project
are submitted concurrently. In addition to this questionnaire, applicants for construction permits must also complete,
I
sign and submit a Construction Activity Storm Water Standards Questionnaire.
To address pollutants that may be generated from new development, the city requires that new development and
significant redevelopment priority projects incorporate Permanent Storm Water Best Management Practices (BMPs)
into the project design, which are described in Section 2 of the city's Storm Water Standards Manual This
I questionnaire should be used to categorize new development and significant redevelopment projects as priority or
non-priority, to determine what level of storm water standards are required or if the project is exempt.
I I 1. Is Your Project a significant redevelopment?
Definition:
-)- Significant redevelopment is defined as the creation or addition of at least 5,000 square feet of impervious surface
on an already developed site. y e
I Significant redevelopment includes, but is not limited to: the expansion of a building footprint; addition to or
replacement of a structure; structural development including an increase in gross floor area and/or exterior
construction remodeling; replacement of an impervious surface that is not part of a routine maintenance activity; and
I land disturbing activities related with structural or impervious surfaces. Replacement of impervious surfaces includes
any activity that is not part of a routine maintenance activity where impervious material(s) are removed, exposing
underlying soil during construction.
I Note: If the Significant Redevelopment results in an increase of less than fifty percent of the impervious surfaces of a
previously existing development, and the existing development was not subject to S(JSMP requirements, the numeric
sizing criteria discussed in Section F.1 .b. (2)(c) applies only to the addition, and not to the entire development.
If your project IS considered significant redevelopment, then please skip Section 1 and proceed with Section 2.
If your project IS NOT considered significant redevelopment, then please proceed to Section 1.
I
I E-34 Page 1 of 3 REV 8/12/09
I
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CITY OF
CAR LSBAD
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Development Services
Engineering Department
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
SECTION 1
NEW DEVELOPMENT
PRIORITY PROJECT TYPE YES NO Does you project meet one or more of the following criteria:
Home subdivision of 100 units or more.
Includes SF0, MFD, Condominium and Apartments
Residential development of 10 units or more.
Includes SF0. MFD, Condominium and Apartments
Commercial and industrial development greater than 100,000 square feet including parking areas.
Any development on private land that is not for heavy industrial or residential uses. Example: Hospitals,
Hotels, Recreational Recreational Facilities, Shopping Malls, etc.
Heavy lndustna!I Industry greater than I acre (NEED SIC CODES FOR PERMIT BUSINESS TYPES)
SIC codes 5013, 5014, 5541, 7532-7534, and 7536-7539
Automotive repair shop.
SIC codes 5013, 5014, 5541, 7532-7534, and 7536-7539
A New Restaurant where the land area of development is 5,000 square feet or more including parking areas.
SIC code 5812
Hillside development
(1) greater than 5,000 square feet of impervious surface area and (2) development will grade on any natural
slope that is 25% or greater
Environmentally Sensitive Area (ESA).
Impervious surface of 2,500 square feet or more located within, "directly adjacent'2 to (within 200 feet), or
"discharging directly to"3 receiving water within the ESA1
Parking lot.
Area of 5,000 square feet or more, or with 15 or more parking spaces, and potentially exposed to urban runoff
Retail Gasoline Outlets - serving more than 100 vehicles per day.
Serving more than 100 vehicles per day and greater than 5,000 square feet
Streets, roads, highways, and freeways.
Project would create a new paved surface that is 5,000 square feet or greater.
Coastal Development Zone.
Within 200 feet of the Pacific Ocean and (I) creates more than 2500 square feet of impermeable surface or (2)
increases impermeable surface on property by more than 10%.
i ESA (Environmentally Sensitive Areas) include but are not limited to all Clean Water Act Section 303(d) impaired water bodies;
areas designated as Areas of Special Biological Significance by the State Water Resources Control Board (Water Quality Control
Plan for the San Diego Basin (1994) and amendments); water bodies designated with the RARE beneficial use by the State Water
Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); areas designated as
preserves or their equivalent under the Multi Species Conservation Program within the Cities and County of San Diego; and any
other equivalent environmentally sensitive areas which have been identified by the co-permittees.
2 "Directly adjacenr means situated within 200 feet of the environmentally sensitive area.
3 Discharging directly to" means outflow from a drainage conveyance system that is composed entirely of flows from the subject
development or redevelopment site, and not commingled with flow from adjacent lands.
Section 1 Results:
If you answered YES to ANY of the questions above you have a PRIORITY project and PRIORITY project requirements DO apply.
A Storm Water Management Plan, prepared in accordance with City Storm Water Standards, must be submitted at time of
application. Please check the "MEETS PRIORITY REQUIREMENTS" box in Section 3.
It you answered NO to ALL of the questions above, then you are a NON-PRIORITY project and STANDARD requirements apply.
Please check the "DOES NOT MEET PRIORITY REQUIREMENTS" box in Section 3.
E-34 Page 2 of 3 REV 8112/09
ThLc Rny for ON Use On/v
ity Concurrence:Yes No
y:
ID ate:
Project ID:
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SECTION 2 I
SIGNIFICANT REDEVELOPMENT: r YES NO
1. If the existing development was constructed today, would it qualify as a priority project? (Priority projects are
defined in Section 1)
If you answered YES, please proceed to question 2.
If you answered NO, then you ARE NOT a significant redevelopment and you ARE NOT subject to PRIORITY project requirements.
only STANDARD requirements. Please check the 'DOES NOT MEET PRIORITY REQUIREMENTS" box in Section 3 below.
2. Is the project solely limited to one of the following:
Trenching and resurfacing associated with utility work?
Resurfacing and reconfiguring existing surface parking lots?
New sidewalk construction, pedestrian ramps, or bike lane on public and/or private existing roads?
Replacement of existing damaged pavement?
If you answered NO to ALL of the questions, then proceed to Question 3.
If you answered YES to ONE OR MORE of the questions then you ARE NOT a significant redevelopment and you ARE NOT subject to
PRIORITY project requirements, only STANDARD requirements. Please check the 'DOES NOT MEET PRIORITY REQUIREMENTS"
box in Section 3 below.
3. Will the development create, replace, or add at least 5,000 square feet of impervious surfaces on an existing
development, or be located within 200 feet of the Pacific Ocean and (1) create more than 2500 square feet of
impermeable surface or (2) increase impermeable surface on property by more than 10%?
If you answered YES, you ARE a significant redevelopment and you ARE subject to PRIORITY project requirements. Please check
the "MEETS WITH REQUIREMENTS" box in Section 3 below.
If you answered NO, you ARE NOT a significant redevelopment, and you ARE NOT subject to PRIORITY project requirements, Only
STANDARD requirements. Please check the 'DOES NOT MEET PRIORITY REQUIREMENTS" box in Section 3 below.
SECTION 3 I
Questionnaire Results:
0 MY PROJECT MEETS PRIORITY REQUIREMENTS. MUST COMPLY WITH PRIORITY PROJECT STANDARDS AND MUST
PREPARE A STORM WATER MANAGEMENT PLAN FOR SUBMITTAL AT TIME OF APPLICATION.
Wr MY PROJECT DOES NOT MEET PRIORITY REQUIREMENTS AND MUST ONLY COMPLY WITH STANDARD STORM
WATER REQUIREMENTS.
AnnIh'cnt Infnm,.tir)n AnH 5ir,nh,rô Any
Address: Assessor's Parcel Number(s):
4143 '?r2 ycA C'a'c/e e4dCA?,O,
Apph'cantName
, j. Applicant Title:
Applicant ignature: Date:
f
REV 8/12/09
CITY* OF
CARLSBAD
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Development Services
Engineering Department
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
E-34 Page 3 of 3
PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
APPENDIX C: CITY OF CARLSBAD STANDARDS EXCERPTS
I Table 1: Standard Development Project & Priority Project Storm Water BMP
Requirements Matrix
BMPs Applicable to Individual
rity PdCategories (3)
I ICz CQ
0 13
Site Source o •
0 ?
8
. Treatment
Design Control > 0 ± Control
BMPs(1) BMPs(2) BMPs(4)
Standard Projects R R 0 0 0 1 0 0 0 0 0 0 0 0
Priority Projects:
Detached
Residential R R R R R S
Development
Attached
Residential R R R S
Development
Commercial
Development R R R R R R S
>100,000 ft2
Automotive R R R R R R R S
Repair
Restaurants R R R R S
Hillside
Development R R R R S
<5, 000 ft2
Parking Lots R R R(5) S
Streets,
Highways, & R R S
Freeways
R = Required; select one or more applicable and appropriate BMPs from the applicable steps in Section III.2.a-d, or
equivalent as identified in Appendix C.
0 = Optional or may be required by City Staff. As appropriate, applicants are encouraged to incorporate treatment
control BMPs and BMPs applicable to individual priority project categories into the project design. City staff may
require one or more of these BMPs, where applicable.
S = Select one or more applicable and appropriate treatment control BMPs from Appendix C.
Refer to Section III.2.A.
Refer to Section III.2.B.
Priority Project categories must apply specific Storm water BMP requirements, where applicable. Priority projects
are subject to the requirements of all priority project categories that apply.
Refer to Section III.2.1).
Applies if the paved area totals >5,000 square feet or with >15 parkign spaces and is potentially exposed to urban
run-off.
Source: City of Carlsbad Public Works Department Standard Urban Storm Water Mitigation
Plan Storm Water Standards (2008, page 6)
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PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
APPENDIX C: CITY OF CARLSBAD STANDARDS EXCERPTS
I Table 2: Anticipated and Potential Pollutants Generated by Land Use Type
General Pollutant Categories
Project
Categories Sediments Nutrients Heavy Organic Trash Oxygen Oil Bacteria Pesticides
Metals Compounds & Demanding & &
Debris Substances Grease Viruses
Detached
Residential X X X X X X X
Development
Attached
Residential X X X PO) p(2) p') x
Development
Commercial
Development pW p( p(2) x p(5) x p(3) p(5)
> 100,000 ft2
Automotive X X' X X
Repair
Restaurants X X X X
Hillside
Development X X X X X X
<5, 000 ft2
Parking Lots p(') p(l) x p) x
Streets,
Highways, & X p(l)x x x x p(5) x
Freeways
Notes:
X = Anticipated
P = Potential
A potential pollutant if landscaping exists on-site.
A potential pollutant if the project includes uncovered parking areas.
A potential pollutant is land use involves food or animal waste areas.
Including petroleum hydrocarbons.
Including solvents.
Source: City of Carlsbad Public Works Department Standard Urban Storm Water Mitigation
Plan Storm Water Standards (2008, page 8)
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PRELIMINARY STORM WATER MANAGEMENT PLAN
STATE STREET CONDOS
APPENDIX C: CITY OF CARLSBAD STANDARDS EXCERPTS
Table 3: Numeric Suing Treatment Standards
Volume
Volume-based BMPs shall be designed to mitigate (infiltrate, filter, or treat) the volume of run-off
produced from a 24-Hour 85th percentile storm event, as determined from Isopluvial maps contained in
the County of San Diego Hydrology Manual.
OR
Flow
Flow-based BMPs shall be designed to mitigate (infiltrate, filter, or treat) the maximum flow rate of
run-off produced from a rainfall intensity of 0.2 inch of rainfall per hour for each hour of a storm
event.
Source: City of Carlsbad Public Works Department Standard Urban Storm Water
Mitigation Plan Storm Water Standards (2008, page 14)
PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
APPENDIX C: CITY OF CARLSBAD STANDARDS EXCERPTS
I Table 4: Structural Treatment Control BMP Selection Matrix
Treatment Control BMP Categories
Pollutant
Of Biofilters Detention Infiltration Wet Ponds Drainage Filtration Hydrodynamic
Concern Basins Basins (1) or Inserts Separator
Wetlands Systems (2)
Sediment M H H H L H M
Nutrient L M M M L M L
Heavy M M M H L H L
Metals
Organic U U U U L M L
Compounds
Trash& L H U U M H M
Debris
Oxygen L M M M L M L
Demanding
Substances
Bacteria U U H U L M L
Oil& M M U U L H L
Grease
Pesticides U U U U L U L
Notes:
Including trenches and porous pavement.
Also known as hydrodynamic devices and baffle boxes
Low removal efficiency
Medium removal efficiency
H: High removal efficiency
U: Unknown removal efficiency
Sources: Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (1993),
National Stormwater Best Management Practices Database (2001), and Guide for BMP Selection in Urban
Development Areas (2001).
Source: City of Carlsbad Public Works Department Standard Urban Storm Water Mitigation
Plan Storm Water Standards (2008, page 15)
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PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
APPENDIX D: DRAINAGE STUDY
I Please see 'Preliminary Hydrology Study for State Street Condos' prepared by O'Day
Consultants, Inc dated March 11, 2009
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PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
APPENDIX E: BENEFICIAL USES OF COASTAL WATERS
I Please see attached.
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— — — — — — — — — — — — MM — — — — —
Table 2-3. BENEFICIAL USES OF COASTAL WATERS
Coastal Waters Hydrologic
Unit Basin
Number
BENEFICIAL USE
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0
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Coastal Lagoons - continued
Buena Vista Lagoon
2 4.21 • • • 0 • • •
Loma Alta Slough 4.10 • • S S S S
Mouth of San Luis Rev River 3.11 5 S S • S S
Santa Margarita Lagoon 2.11 0 *
Aliso Creek Mouth 1.13 5 • ,• • •
San Juan Creek Mouth 1.27 5 5 5 S S S
San Mateo Creek-Mouth 1.40 • S S • S S S
San Onofre Creek Mouth 1.51 1 1 01 0 1 1 1 • S S • S
Includes the tidal prisms of the Otay and Sweetwater Rivers.
2 Fishing from shore or boat permitted, but other water contact recreational (REC-1) uses are prohibited.
Existing Beneficial Use
0 Potential Beneficial Use
March 12, 1997
Table 2-3
BENEFICIAL USES -
2-48
PRELIMINARY STORM WATER MANAGEMENT PLAN
STATE STREET CONDOS
APPENDIX F: 2006 CWA SECTION 303(d) LIST OF WATER QUALITY
LIMITED SEDIMENT
Please see attached.
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- - - - - - - = - - - - - - - - - - - 2006 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENTS
(Those requiring TMDLS (A), being addressed by USEPA approved TMDLS (B), and being addressed by actions other than TMDLs (C))*
USEPA APPROVAL DATE: JUNE 28, 200'7
CALWATER POTENTIAL TMDL ESTIMATED PROPOSED OR
I REGION TYPE NAME WATERSHED SOURCES POLLUTANT/STRESSOR REQUIREMENT SIZE AFFECTED USEPA APPROVED
STATUS* TMDL COMPLETION
9 C Pacific Ocean Shoreline, Buena Vista Creek 90421000
HA
Indicator bacteria A 1.2 Miles 2008
Impairment located at Buena Vista Creek, Carlsbad City Beach at Carlsbad Village Drive, Carlsbad State Beach at Pine
Avenue.
Nonpoint/Point Source
9 C Pacific Ocean Shoreline, Dana Point HSA 90114000
9 C Pacific Ocean Shoreline, Escondido Creek 90461000
HA
9 C Pacific Ocean Shoreline, Imperial Beach 91010000
Pier
9 C Pacific Ocean Shoreline, Laguna Beach 90112000
HSA
9 C Pacific Ocean Shoreline, Loma Alta HA 90410000
Indicator bacteria A 2 Miles 2005
Impairment located at Aliso Beach at West Street, Aliso Beach at Table Rock Drive, 1000 Steps Beach at Pacific Coast
Hwy (Hospital, 91h Ave), Salt Creek (large outlet), Salt Creek Beach at Salt Creek service road, Salt Creek Beach at
Dana Strand Road, and Monarch Beach.
Nonpoint/Point Source
Indicator bacteria A 0.44 Miles 2008
Impairment located at San Eljo Lagoon outlet.
Nonpoint/Point Source
PCBs (Polychlorinated biphenyls) A 0.42 Miles 2019
Source Unknown
Indicator bacteria A 1.8 Miles 2005
Impairment located at Main Laguna Beach, Laguna Beach at Ocean Avenue, Laguna Beach at Laguna Avenue, Laguna
Beach at Cleo Street, Arch Cove at Bluebird Canyon Road, Laguna Beach at Dumond Drive.
Nonpoint/Point Source
Indicator bacteria A 1.1 Miles 2008
Impairment located at Loma Alto Creek Mouth.
Nonpoint/Point Source
Page 283 01299
I PRELIMINARY STORM WATER MANAGEMENT PLAN
STATE STREET CONDOS
APPENDIX G: SOURCE CONTROL BMP FACT SHEETS
I Please see attached.
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Site Design & Landscape Planning SD-10
Design Objectives
Maximize Infiltration
Provide Retention
Slow Runoff
Minimize Impervious Land
Coverage
Prohibit Dumping of Improper
Materials
Contain Pollutants
Collect and Convey
Descript ion
Each pr3jeoi site pcssesses Lmique topographic, hydrologic, and vegetative features, some of
vhich ae tuore suitable fo: Aevelopment than others. Integrating and incorporating
appropuate landscape plaiuñng meth:dologies into the project design is the most effective
action hat ran be done to rrnimize surface and groundwater contamination from stormwater.
Approac)
Landspe Dlanning Should couple consideration of land suitability for urban uses with
conside rat on of cou1muniy goals and projected. growth. Project plan designs should conserve
natural ars to the extent possible, maximize natural water storage and infiltration
Dpport1:ni1s, and protect sopes and channels.
Suitable Applications
AppiW6ale applications in-Jude residential, commercial and industrial areas planned for
devek pu1.t or redevelopn mt.
Desgn Cnsiderations
Design requirements for site design ad landscapes planning
shou.d coni rm to applicab standars and specifications of
agencies with jurisdiction aLd be consistent with applicable
Geiiera Pin anc. Local Area Plan pol cies.
. fig"
ianuay 2OC3 Califoiia St:rmwater BMP Handbook 1 of 4
New Cevelopmerit and Redevelopment
%m/vw.cabmphandbooks.com
SD-10 Site Design & Landscape Planning
Designing New Installations
Begin the development of a plan for the landscape unit with attention to the following general
principles:
Formulate the plan on the basis of clearly articulated community goals. Carefully identify
conflicts and choices between retaining and protecting desired resources and community
growth.
Mal) and assess land suitability for urban uses. Include the following landscape features in
the assessment: wooded land, open unwooded land, steep slopes, erosion-prone soils,
foundation suitability, soil suitability for waste disposal, aquifers, aquifer recharge areas,
wetlands, floodplains, surface waters, agricultural lands, and various categories of urban
land use. When appropriate, the assessment can highlight outstanding local or regional
resources that the community determines should be protected (e.g., a scenic area,
recreational area, threatened species habitat, farmland, fish rim). Mapping and assessment
should recognize not only these resources but also additional areas needed for their
sustenance.
Project plan designs should conserve natural areas to the extent possible, maximize natural
water storage and infiltration opportunities, and protect slopes and channels.
Conserve Natural Areas during Landscape Planning
If applicable, the following items are required and must be implemented in the site layout
during the subdivision design and approval process, consistent with applicable General Plan and
Local Area Plan policies:
Cluster development on least-sensitive portions of a site while leaving the remaining land in
a natural undisturbed condition.
Limit clearing and grading of native vegetation at a site to the minimum amount needed to
build lots, allow access, and provide fire protection.
Maximize trees and other vegetation at each site by planting additional vegetation, clustering
tree areas, and promoting the use of native and/or drought tolerant plants.
Promote natural vegetation by using parking lot islands amid other landscaped areas.
Preserve riparian areas and wetlands.
Maximize Natural Water Storage and Infiltration Opportunities Within the Landscape Unit
Promote the conservation of forest cover. Building on land that is already deforested affects
basin hydrology to a lesser extent than converting forested land. Loss of forest cover reduces
interception storage, detention in the organic forest floor layer, and water losses by
evapotranspiration, resulting in large peak runoff increases and either their negative effects
or the expense of countering them with structural solutions.
Maintain natural storage reservoirs and drainage corridors, including depressions, areas of
permeable soils, swales, and intermittent streams. Develop and implement policies and
2 of 4 California Stormwater BMP Handbook January 2003 New Development and Redevelopment
www.cahmphandhooks.com
I Site Design & Landscape Planning SD-10
regulations to discourage the clearing, filling, and channelization of these features. Utilize
them in drainage networks in preference to pipes, culverts, and engineered ditches.
I a Evaluating infiltration opportunities by referring to the stormwater management manual for
the jurisdiction and pay particular attention to the selection criteria for avoiding
groundwater contamination, poor soils, and hydrogeological conditions that cause these
I
facilities to fail. If necessary, locate developments with large amounts of impervious
surfaces or a potential to produce relatively contaminated runoff away from groundwater
recharge areas.
I Protection of Slopes and Channels during Landscape Design
Convey runoff safely from the tops of slopes.
I a Avoid disturbing steep or unstable slopes.
Avoid disturbing natural channels.
I a Stabilize disturbed slopes as quickly as possible.
I
a Vegetate slopes with native or drought tolerant vegetation.
Control and treat flows in landscaping and/or other controls prior to reaching existing
natural drainage systems.
I a Stabilize temporary and permanent channel crossings as quickly as possible, and ensure that
increases in run-off velocity and frequency caused by the project do not erode the channel.
1 Install energy dissipaters, such as riprap, at the outlets of new storm drains, culverts,
conduits, or channels that enter unlined channels in accordance with applicable
specifications to minimize erosion. Energy dissipaters shall be installed in such a way as to
I minimize impacts to receiving waters.
Line on-site conveyance channels where appropriate, to reduce erosion caused by increased
flow velocity due to increases in tributary impervious area. The first choice for linings
I should be grass or some other vegetative surface, since these materials not only reduce
runoff velocities, but also provide water quality benefits from filtration and infiltration. If
velocities in the channel are high enough to erode grass or other vegetative linings, riprap,
I concrete, soil cement, or geo-grid stabilization are other alternatives.
a Consider other design principles that are comparable and equally effective.
I Redeveloping Existing Installations
Various jurisdictional storm'water management and mitigation plans (SUSMP, WQMP, etc.)
define "redevelopment" in terms of amounts of additional impervious area, increases in gross
I floor area and/or exterior construction, and land disturbing activities with structural or
impervious surfaces. The definition of" redevelopment" must be consulted to determine
whether or not the requirements for new development apply to areas intended for
I 'designing redevelopment. If the definition applies, the steps outlined under new installations"
above should be followed.
January 2003 California Stormwater BMP Handbook 3 of 4
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SD-10 Site Design & Landscape Planning
Redevelopment may present significant opportunity to add features which had not previously
been implemented. Examples include incorporation of depressions, areas of permeable soils,
and swales in newly redeveloped areas. While some site constraints may exist due to the status
of already existing infrastructure, opportunities should not be missed to maximize infiltration,
slow runoff, reduce impervious areas, disconnect directly connected impervious areas.
Other Resources
A Manual for the Standard Urban Stormwater Mitigation Plan (SUSMP), Los Angeles County
Department of Public Works, May 2002.
Stormwater Management Manual for Western Washington, Washington State Department of
Ecology, August 2001.
Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of
San Diego, and Cities in San Diego County, February 14, 2002.
Model Water Quality Management Plan (WQMP) for County of Orange, Orange County Flood
Control District, and the Incorporated Cities of Orange County, Draft February 2003.
Ventura Countywide Technical Guidance Manual for Stormwater Quality Control Measures,
July 2002.
4 of 4 California Stormwater BMP Handbook January 2003
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Design Objectives
1f Maximize Infiltration
/ Provide Retention
/ Slow Runoff
Minimize Impervious Land
Coverage
Prohibit Dumping of Improper
Materials
Contain Pollutants
Collect and Convey
Roof Runoff Controls SD-11
Rain Garden
De;cription
Various roof runoff controls are available to add -ess storrnwate
:hal drains off rooftops. The objective is to rediue the tctal volume and rate of runoff from
iEd:vidual lots, and retain the pollutants an site.1-at may be piked up from roofing materials
md atmospheric deposition. Roof runoff contrcls consiit of dii ecting the roof runoff away from
vad areas and mitigating flow to the storm drain system thrc igh one of several general
macaches: cisterns or rain barrels; dry welds o riflltradcn trenches; pop-up emitters, and
foumation planting. The first three approaches lequire the rcof runoff to be contained in a
atter and downspout system. Foundation plan :iTg pro-ides a vegetated strip under the drip
line of the roof.
Ap 3roach
[egn of individual lots for single-family hcrne as well as lots for higher density residential and
:)rnrnerciaJ structures should consider site design provi ions f:r containing and infiltrating roof
riri:ff or directing roof runoff to vegetative swa1 or bufer arts. Retained water can be reused
ior Natering gardens, lawns, and trees. Eenefits to the environment include reduced demand for
table water used for irrigation, imprcvad storm Aater quality, increased groundwater
recharge, decreased runoff volume and peak flc'w. and cecreasad flooding potential.
Suitable Applications
pTropriate applications include residential ':o,imerciai and industrial areas planned for
'ievlopment or redevelopment.
Design Considerations
Designing New Installations
1isrns or Rain Barrels
C rn method of addressing roof runoff is :o 'Ire oaf dcwnspouts
:o cisterns or rain barrels. A cistern is an above ;round storage S 0 A
vs.e with either a manually operated valve cr r permar ently :pen California
oat let. Roof runoff is temporarily stored and then relead for Stormwater
irigation or infiltration between storms. The nurriber of rain Quality
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SDii Roof Runoff Controls
barrels needed is a function of the rooftop area. Some low inipact developers recommend that
every house have at least 2 rain barrels, with a minimum storage capacity of 1000 liters. Roof
barrels serve several purposes including mitigating the first flush from the roof which has a high
volume, amount of contaminants, and thermal load. Several types of rain barrels are
commercially available. Consideration must he given to selecting rain barrels that are vector
proof and childproof. In addition, some barrels are designed with a by valve that filters out
grit and other contaminants and routes overflow to a soak-away pit or rain garden.
If the cistern has an operable valve, the valve can be closed to store stormwater for irrigation or
infiltration between storms. This system requires continual monitoring by the resident or
grounds crews, but provides greater flexibility in water storage and metering. If a cistern is
provided with an operable valve and water is stored inside for long periods, the cistern must be
covered to prevent mosquitoes from breeding.
A cistern System with a permanently open outlet can also provide for metering stormwater
runoff. If the cistern outlet is significantly smaller than the size of the downspout inlet (say 1/4 to
1/2 inch diameter), runoff will build up inside the cistern during storms, and will empty out
slowly after peak intensities subside. This is a feasible way to mitigate the peak flow increases
caused by rooftop impervious land coverage, especially for the frequent, small storms.
Dry wells and Infiltration Trenches
Roof downspouts can be directed to dry wells or infiltration trenches. A dry well is constructed
by excavating a hole in the ground and filling it with an open graded aggregate, and allowing the
water to fill the dry well and infiltrate after the storm event. An underground connection from
the downspout conveys water into the dry well, allowing it to be stored in the voids. To
minimize sedimentation from lateral soil movement, the sides and top of the stone storage
matrix can be wrapped in a permeable filter fabric, though the bottom may remain open. A
perforated observation pipe can be inserted vertically into the dry well to allow for inspection
and maintenance.
In practice, dry wells receiving runoff from single roof downspouts have been successful over
long periods because they contain very little sediment. They must be sized according to the
amount of rooftop runoff received, but are typically 4 to 5 feet square, and 2 to 3 feet deep, with
a minimum of i-foot soil cover over the top (maximum depth of to feet).
To protect the foundation, dry wells must be set away from the building at least 10 feet. They
must be installed in solids that accommodate infiltration. In poorly drained soils, dry wells have
very limited feasibility.
Infiltration trenches function in a similar manner and would be particularly effective for larger
roof areas. An infiltration trench is a long, narrow, rock-filled trench with no outlet that receives
stormwater runoff. These are described under Treatment Controls.
Pop-up Drainage Emitter
Roof downspouts can be directed to an underground pipe that daylights some distance from the
building foundation, releasing the roof runoff through a pop-up emitter. Similar to a pop-up
irrigation head, the emitter only opens when there is flow from the roof. The emitter remains
flush to the ground during dry periods, for ease of lawn or landscape maintenance.
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Roof Runoff Controls SD-11
I Foundation Planting
Landscape planting can be provided around the base to allow increased opportunities for
I stormwater infiltration and protect the soil from erosion caused by concentrated sheet flow
coming off the roof. Foundation plantings can reduce the physical impact of water on the soil
and provide a subsurface matrix of roots that encourage infiltration. These plantings must be
I sturdy enough to tolerate the heavy runoff sheet flows, and periodic soil saturation.
Redeveloping Existing Installations
Various jurisdictional stormwater management and mitigation plans (SUSMP, WQMP, etc.)
I define "redevelopment" in terms of amounts of additional impervious area, increases in gross
floor area and/or exterior construction, and land disturbing activities with structural or
impervious surfaces. The definition of" redevelopment" must be consulted to determine
I whether or not the requirements for new development apply to areas intended for
redevelopment. If the definition applies, the steps outlined under "designing new installations"
above should be followed.
Supplemental Information
Examples
City of Ottawa's Water Links Surface —Water Quality Protection Program
City of Toronto Downspout Disconnection Program
City of Boston, MA, Rain Barrel Demonstration Program
Other Resources
Hager, Marty Catherine, Stormwater, "Low-Impact Development", January/ February 2003.
www.stormh20.com
Low Impact Urban Design Tools, Low Impact Development Design Center, Beltsville, MD.
rww.hd-stormwater, net
Start at the Source, Bay Area Stormwater Management Agencies Association, 1999 Edition
January 2003 California Stormwater BMP Handbook 3 of 3
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Efficient Irrigation SD-12
Design Objectives
EI Maximize Infiltration
Provide Retention
[?l Slow Runoff
Minimize Impervious Land
Coverage
Prohibit Dumping of Improper
Materials
Contain Pollutants
Collect and Convey
Description
Irrigation water provided to landscaped areas may result in excess irrigation water being
conveyed into stormnwater drainage systems.
Approach
?roject plan designs for development and redevelopment should include application methods of
:rrigation water that niinimize runoff of excess irrigation water 11t0 the stormwater conveyance
system.
Suitable Applications
Appropriate applications include residential, commercial and li dustrial areas planned for
development or redevelopment. (Detached residential single-family homes are typically
-excluded from this requirement.)
Design Considerations
Designing New Installations
The following methods to reduce excessive irrigation runoff shild be considered, and
.ncorporated and implemented where determined applicable ard feasible by the Penimittee:
Employ rain-triggered shutoff devices to prevent irrigation after precipitation.
Design irrigation systems to each landscape areas specific water requirements.
Include design featuring flow reducers or shutoff valves
triggered by a pressure drop to control water loss in the event
of broken sprinkler heads or hues.
Implement landscape plans consistent with County or City
water conservation resolutions, which may include provisioa
of water sensors, progranuinable irrigation times (for short
cycles), etc.
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SD-12 Efficient Irrigation
Design timing and application methods of irrigation water to minimize the runoff of excess
irrigation water into the storm water drainage system.
Group plants with similar water requirements in order to reduce excess irrigation runoff and
promote surface filtration. Choose plants with low irrigation requirements (for example,
native or drought tolerant species). Consider design features such as:
- Using mulches (such as wood chips or bar) in planter areas without ground cover to
minimize sediment in runoff
- Installing appropriate plant materials for the location, in accordance with amount of
sunlight and climate, and use native plant materials where possible and/or as
recommended by the landscape architect
Leaving a vegetative barrier along the property boundary and interior watercourses, to
act as a pollutant filter, where appropriate and feasible
- Choosing plants that minimize or eliminate the use of fertilizer or pesticides to sustain
growth
a Employ other comparable, equally effective methods to reduce irrigation water rimoff.
Redeveloping Existing Installations
Various jurisdictional storniwater management and mitigation plans (SUSMP, WQMP, etc.)
define"redevelopment" in terms of amounts of additional impervious area, increases in gross
floor area and exterior construction, and land disturbing activities with structural or
impervious surfaces. The definition of * redevelopment" must be consulted to determine
whether or not the requirements for new development apply to areas intended for
redevelopment. If the definition applies, the steps outlined under 'designing new installations"
above should be followed.
Other Resources
A Manual for the Standard Urban Stormwater Mitigation Plan (SUSMP), Los Angeles County
Department of Public Works, May 2002,
Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of
San Diego, and Cities in San Diego County, February 14, 2002.
Model Water Quality Management Plan (WQMP) for Count), of Orange, Orange County Flood
Control District, and the Incorporated Cities of Orange County, Draft February 2003.
Ventura Countywide Technical Guidance Manual for Stormwater Quality Control Measures,
July 2002.
2 of 2 California Stormwater BMP Handbook January 2003
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I Trash Storage Areas SD-32
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Description
Trash storage areas are areas where a trash receptacle (s) are
located for use as a repository for solid wastes. Stormwater
runoff from areas where trash is stored or disposed of can be
polluted. In addition, loose trash and debris can be easily
transported by water or wind into nearby storm drain inlets,
channels, and/or creeks. Waste handling operations that may be
sources of stormwater pollution include dumpsters, litter control,
and waste piles.
Approach
This fact sheet contains details on the specific measures required
to prevent or reduce pollutants in stormwater runoff associated
with trash storage and handling. Preventative measures
including enclosures, containment structures, and impervious
pavements to mitigate spills, should be used to reduce the
likelihood of contamination.
Design Objectives
Maximize Infiltration
Provide Retention
Slow Runoff
Minimize Impervious Land
Coverage
Prohibit Dumping of Improper
Materials
Contain Pollutants
Collect and Convey
Suitable Applications
Appropriate applications include residential, commercial and industrial areas planned for
development or redevelopment. (Detached residential single-family homes are typically
excluded from this requirement.)
Design Considerations
Design requirements for waste handling areas are governed by Building and Fire Codes, and by
current local agency ordinances and zoning requirements. The design criteria described in this
fact sheet are meant to enhance and be consistent with these code and ordinance requirements.
Hazardous waste should be handled in accordance with legal requirements established in Title
22, California Code of Regulation.
Wastes from commercial and industrial sites are typically hauled by either public or commercial
carriers that may have design or access requirements for waste storage areas. The design
criteria in this fact sheet are recommendations and are not intended to be in conflict with
requirements established by the waste hauler. The waste hauler should be contacted prior to the
design of your site trash collection areas. Conflicts or issues should be discussed with the local
agency.
Designing New Installations
Trash storage areas should be designed to consider the following structural or treatment control
BMPs:
a Design trash container areas so that drainage from adjoining
I roofs and pavement is diverted around the area(s) to avoid
run-on. This might include berming or grading the waste
handling area to prevent run-on of stormwater.
I a Make sure trash container areas are screened or walled to
prevent off-site transport of trash. £
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SD-32 Trash Storage Areas
Use lined bins or dumpsters to reduce leaking of liquid waste.
Provide roofs, awnings, or attached lids on all trash containers to minimize direct
precipitation and prevent rainfall from entering containers.
a Pave trash storage areas with an impervious surface to mitigate spills.
Do not locate storni drains in immediate vicinity of the trash storage area.
a Post signs on all dumpsters informing users that hazardous materials are not to be disposed
of therein.
Redeveloping Existing Installations
Various jurisdictional stormwater management and mitigation plans (SUSMP, WQMP, etc.)
define "redevelopment" in terms of amounts of additional impervious area, increases in gross
floor area and/or exterior construction, and land disturbing activities with structural or
impervious surfaces. The definition of" redevelopment" must be consulted to determine
whether or not the requirements for new development apply to areas intended for
redevelopment. If the definition applies, the steps outlined under "designing new installations"
above should be followed.
Additional Information
Maintenance Considerations
The integrity of structural elements that are subject to damage (i.e., screens, covers, and signs)
must be maintained by the owner/operator. Maintenance agreements between the local agency
and the owner/operator may be required. Some agencies will require maintenance deed
restrictions to be recorded of the property title. If required by the local agency, maintenance
agreements or deed restrictions must be executed by the owner/operator before improvement
plans are approved.
Other Resources
A Manual for the Standard Urban Stormwater Mitigation Plan (SUSMP), Los Angeles County
Department of Public Works, May 2002.
Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of
San Diego, and Cities in San Diego County, February 14, 2002.
Model Water Quality Management Plan (WQMP) for County of Orange, Orange County Flood
Control District, and the Incorporated Cities of Orange County, Draft February 2003.
Ventura Countywide Technical Guidance Manual for Stormwater Quality Control Measures,
July 2002.
2 of 2 California Stormwater BMP Handbook January 2003
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PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
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APPENDIX H: TREATMENT CONTROL BMP FACT SHEETS
Please see attached.
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Targeted Constituents
Sediment U
Nutrients A
21 Trash U
Metals
1 Bacteria U
Oil and Grease U
I Organics U
Legend (Removal Effectiveness)
S Low U High
A Medium
Bioretention TC-32
Design Considerations
Soil for Infiltration
Tributary Area
Slope
Aesthetics
s Environmental Side-effects
,gla* J1
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Description
The bioretention best management practice (BMP) functions as a
soil and plant-based filtration device that removes pollutants
through a variety of physical, biological, and chemical treatmer.t
processes. These facilities normally consist of a grass buffer
strip, sand bed, ponding area, organic layer or mulch layer,
planting soil, and plants. The runoffs velocity is reduced by
passing over or through buffer strip and subsequently distributed
evenly along a ponding area. Exfiltration of the stored water in
the bioretention area planting soil into the underlying soils
occurs over a period of days.
California Experience
None documented. Bioretention has been used as a storniwater
BMP since 1992. In addition to Prince George's County, MD and
Alexandria, VA, bioretention has been used successfully at urban
and suburban areas in Montgomery County, MD; Baltimore
County, MD; Chesterfield County, VA; Prince William County,
VA; Smith Mountain Lake State Park, VA, and Cary, NC.
Advantages
Bioretention provides stormwater treatment that enhances
the quality of dowistream water bodies by temporarily
storing runoff in the BMP and releasing it over a period of
four days to the receiving water (EPA, 1999).
The vegetation provides shade and wind breaks, absorbs
noise, and improves an area's landscape.
Limitations
The bioretention BMP is not recommended for areas with
slopes greater than 20% or where mature tree removal world
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TC-32 Bioretention
be required since clogging may result, particularly if the BMP receives runoff with high
sediment loads (EPA, 1999).
Bioretention is not a suitable BMP at locations where the water table is within 6 feet of the
ground surface and where the surrounding soil stratum is unstable.
By design, bioretention BMPs have the potential to create very attractive habitats for
mosquitoes and other vectors because of highly organic, often heavily vegetated areas mixed
with shallow water.
In cold climates the soil may freeze, preventing runoff ft-oiii infiltrating into the planting soil.
Design and Sizing Guidelines
The bioretention area should be sized to capture the design storm runoff.
In areas where the native soil permeability is less than 0.5 ii/hr an nnderdrain should be
provided.
Recommended minimum dimensions are 15 feet by 40 feet, although the preferred width is
25 feet. Excavated depth should be 4 feet.
Area should drain completely within 72 hours.
Approximately 1 tree or shrub per 50 ft2 of bioretention area should be included.
Cover area with about 3 inches of mulch.
Construction/Inspection Considerations
Bioretention area should not be established until contributing watershed is stabilized.
Performance
Bioretention removes stormwater pollutants through physical and biological processes,
including adsorption, filtration, plant uptake, microbial activity, decomposition, sedimentation
and volatilization (EPA, 1999). Adsorption is the process whereby particulate pollutants attach
to soil (e.g., clay) or vegetation surfaces. Adequate contact time between the surface and
pollutant must be provided for in the design of the system for this removal process to occur.
Thus, the infiltration rate of the soils must not exceed those specified in the design criteria or
pollutant removal may decrease. Pollutants removed by adsorption include metals, phosphorus,
and hydrocarbons. Filtration occurs as runoff passes through the bioretention area media, such
as the sand bed, ground cover, and planting soil.
Conmion particulates removed from stormwater include particulate organic matter,
phosphorus, and suspended solids. Biological processes that occur in wetlands result in
pollutant uptake by plants and microorganisms in the soil. Plant growth is sustained by the
uptake of nutrients from the soils, with woody plants locking up these nutrients through the
seasons. Microbial activity within the soil also contributes to the removal of nitrogen and
organic matter. Nitrogen is removed by nitrifying and denitrifying bacteria, while aerobic
bacteria are responsible for the decomposition of the organic matter. Microbial processes
require oxygen and can result in depleted oxygen levels if the bioretention area is not adequately
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I Bioretention I TC-32
I aerated. Sedimentation occurs in the swale or ponding area as the velocity slows and solids fall
out of suspension.
The removal effectiveness of bioretention has been studied during field and laboratory studies
conducted by the University of Maryland (Davis et al, 1998). During these experiments,
synthetic stormwater runoff was pumped through several laboratory and field bioretention areas
I to simulate typical storm events in Prince George's County, MD. Removal rates for heavy metals
and nutrients are shown in Table i.
Table I Laboratory and Estimated
Bioretention Davis et at. (1998);
PGDER (1993)
Pollutant Removal Rate
Total Phosphorus 70-83%
Metals (Cu, Zn, Pb) 93-98%
TKN 68-80%
Total Suspended Solids 90%
Organics 90%
Bacteria 90%
' Results for both the laboratory and field experiments were similar for each of the pollutants
analyzed. Doubling or halving the influent pollutant levels had little effect on the effluent
pollutants concentrations (Davis et al, 1998).
I The microbial activity and plant uptake occurring in the bioretention area will likely result in
higher removal rates than those determined for infiltration BMPs.
Siting Criteria I Bioretention BMPs are generally used to treat stormwater from impervious surfaces at
commercial, residential, and industrial areas (EPA, 1999). Implementation of bioretention for
stormwater management is ideal for median strips, parking lot islands, and swales. Moreover, U the runoff in these areas can be designed to either divert directly into the bioretention area or
convey into the bioretention area by a curb and gutter collection system. ' The best location for bioretention areas is upland from inlets that receive sheet flow from graded
areas and at areas that will be excavated (EPA, 1999). In order to maximize treatment
effectiveness, the site must be graded in such a way that minimizes erosive conditions as sheet
flow is conveyed to the treatment area. Locations where a bioretention area can be readily I incorporated into the site plan without further environmental damage are preferred.
Furthermore, to effectively minimize sediment loading in the treatment area, bioretention only
should be used in stabilized drainage areas.
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TC-32 Bioretention
Additional Design Guidelines
The layout of the bioretention area is determined after site constraints such as location of
utilities, underlying soils, existing vegetation, and drainage are considered (EPA, 1999). Sites
with loamy sand soils are especially appropriate for bioretention because the excavated soil can
be backfilled and used as the planting soil, thus eliminating the cost of importing planting soil.
The use of bioretention may not be feasible given an unstable surrounding soil stratum, soils
with clay content greater than 25 percent, a site with slopes greater than 20 percent, and/or a
site with mature trees that would be removed during construction of the BMP.
Bioretention can be designed to be off-line or on-line of the existing drainage system (EPA,
1999). The drainage area for a bioretention area should be between o.i and 0.4 hectares (0.25
and 1.0 acres). Larger drainage areas may require multiple bioretention areas. Furthermore,
the maximum drainage area for a bioretention area is determined by the expected rainfall
intensity and runoff rate. Stabilized areas may erode when velocities are greater than 5 feet per
second (1.5 meter per second). The designer should determine the potential for erosive
conditions at the site.
The size of the bioretention area, which is a function of the drainage area and the runoff
generated from the area is sized to capture the water quality volume.
The recommended minimum dimensions of the bioretention area are 15 feet (4.6 meters) wide
by 40 feet (12.2 meters) long, where the minimum width allows enough space for a dense,
randomly-distributed area of trees and shrubs to become established. Thus replicating a natural
forest and creating a microclimate, thereby enabling the bioretention area to tolerate the effects
of heat stress, acid rain, runoff pollutants, and insect and disease infestations which landscaped
areas in urban settings typically are unable to tolerate. The preferred width is 25 feet (7.6
meters), with a length of twice the width. Essentially, any facilities wider than 20 feet (6.1
meters) should be twice as long as they are wide, which promotes the distribution of flow and
decreases the chances of concentrated flow.
In order to provide adequate storage and prevent water from standing for excessive periods of
time the ponding depth of the bioretention area should not exceed 6 inches (15 centimeters).
Water should not be left to stand for more than 72 hours. A restriction on the type of plants that
can be used may be necessary due to some plants' water intolerance. Furthermore, if water is
left standing for longer than 72 hours mosquitoes and other insects may start to breed.
The appropriate planting soil should be backfllled into the excavated bioretention area. Planting
soils should be sandy loam, loamy sand, or loam texture with a clay content ranging from 10 to
25 percent.
Generally the soil should have infiltration rates greater than 0.5 inches (1.25 centimeters) per
hour, which is typical of sandy barns, loamy sands, or barns. The pH of the soil should range
between 5.5 and 6.5, where pollutants such as organic nitrogen and phosphorus can be adsorbed
by the soil and microbial activity can flourish. Additional requirements for the planting soil
include a 1.5 to 3 percent organic content and a maximum 500 ppm concentration of soluble
salts.
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I Soil tests should be performed for every 500 cubic yards (382 cubic meters) of planting soil,
with the exception of pH and organic content tests, which are required only once per
bioretention area (EPA, 1999). Planting soil should be 4 inches (10.1 centimeters) deeper than
I the bottom of the largest root ball and 4 feet (1.2 meters) altogether. This depth will provide
adequate soil for the plants' root systems to become established, prevent plant damage due to
I order
severe wind, and provide adequate moisture capacity. Most sites will require excavation in
to obtain the recommended depth.
Planting soil depths of greater than 4 feet (1.2 meters) may require additional construction
I practices such as shoring measures (EPA, 1999). Planting soil should be placed in 18 inches or
greater lifts and lightly compacted until the desired depth is reached. Since high canopy trees
may be destroyed during maintenance the bioretention area should be vegetated to resemble a
terrestrial forest community ecosystem that is dominated by understory trees. Three species
I each of both trees and shrubs are recommended to be planted at a rate of 2500 trees and shrubs
per hectare (1000 per acre). For instance, a 15 foot (4.6 meter) by 40 foot (12.2 meter)
I The
bioretention area (6o0 square feet or 55.75 square meters) would require 14 trees and shrubs.
shrub-to-tree ratio should be :i to :i.
Trees and shrubs should be planted when conditions are favorable. Vegetation should be
I watered at the end of each day for fourteen days following its planting. Plant species tolerant of
pollutant loads and varying wet and thy conditions should be used in the bioretention area.
The designer should assess aesthetics, site layout, and maintenance requirements when
I selecting plant species. Adjacent non-native invasive species should be identified and the
designer should take measures, such as providing a soil breach to eliminate the threat of these
species invading the bioretention area. Regional landscaping manuals should be consulted to
I ensure that the planting of the bioretention area meets the landscaping requirements
established by the local authorities. The designers should evaluate the best placement of
vegetation within the bioretention area. Plants should be placed at irregular intervals to
replicate a natural forest. Trees should be placed on the perimeter of the area to provide shade I and shelter from the wind. Trees and shrubs can be sheltered from damaging flows if they are
placed away from the path of the incoming runoff. In cold climates, species that are more
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tolerant to cold winds, such as evergreens, should be placed in windier areas of the site.
Following placement of the trees and shrubs, the ground cover and/or mulch should be
established. Ground cover such as grasses or legumes can be planted at the beginning of the
I growing season. Mulch should be placed immediately after trees and shrubs are planted. Two
to 3 inches (5 to 7.6 cm) of commercially-available fine shredded hardwood mulch or shredded
hardwood chips should be applied to the bioretention area to protect from erosion.
1 Maintenance
The primary maintenance requirement for bioretention areas is that of inspection and repair or
replacement of the treatment area's components. Generally, this involves nothing more than the
l routine periodic maintenance that is required of any landscaped area. Plants that are
appropriate for the site, climatic, and watering conditions should be selected for use in the
bioretention cell. Appropriately selected plants will aide in reducing fertilizer, pesticide, water,
I and overall maintenance requirements. Bioretention system components should blend over
time through plant and root growth, organic decomposition, and the development of a natural
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soil horizon. These biologic and physical processes over time will lengthen the faciiti/s life span
and reduce the need for extensive maintenance.
Routine maintenance should include a biannual health evaluation of the trees and shrubs and
subsequent removal of any dead or diseased vegetation (EPA, 1999). Diseased vegetation
should be treated as needed using preventative and low-toxic measures to the extent possible.
BMPs have the potential to create very attractive habitats for mosquitoes and other vectors
because of highly organic, often heavily vegetated areas mixed with shallow water. Routine
inspections for areas of standing water within the BMP and corrective measures to restore
proper infiltration rates are necessary to prevent creating mosquito and other vector habitat. In
addition, bioretention BMPs are susceptible to invasion by aggressive plant species such as
cattails, which increase the chances of water standing and subsequent vector production if not
routinely maintained.
In order to maintain the treatment area's appearance it may be necessary to prune and weed.
Furthermore, mulch replacement is suggested when erosion is evident or when the site begins to
look unattractive. Specifically, the entire area may require mulch replacement every two to
three years, although spot mulching may be sufficient when there are random void areas. Mulch
replacement should be done prior to the start of the wet season.
New Jersey's Department of EnvironmentaiProtection states in their bioretention systems
standards that accumulated sediment and debris removal (especially at the inflow point) will
normally be the primary maintenance function. Other potential tasks include replacement of
dead vegetation, soil pH regulation, erosion repair at inflow points, mulch replenishment,
unclogging the underdrain, and repairing overflow structures. There is also the possibility that
the cation exchange capacity of the soils in the cell will be significantly reduced over time.
Depending on pollutant loads, soils may need to be replaced within 5-10 years of construction
(LID, 2000).
Cost
Construction Cost
Construction cost estimates for a bioretention area are slightly greater than those for the
required landscaping for a new development (EPA, 1999). A general rule of thumb (Coffman,
1999) is that residential bioretention areas average about $3 to $4 per square foot, depending on
soil conditions and the density and types of plants used. Commercial, industrial and
institutional site costs can range between $io to $40 per square foot, based on the need for
control structures, curbing, storm drains and underdrains.
Retrofitting a site typically costs more, averaging $6,500 per bioretention area. The higher costs
are attributed to the demolition of existing concrete, asphalt, and existing structures and the
replacement of fill material with planting soil. The costs of retrofitting a commercial site in
Maryland, Kettering Development, with 15 bioretention areas were estimated at $iii,600.
In any bioretention area design, the cost of plants varies substantially and can account for a
significant portion of the expenditures. While these cost estimates are slightly greater than
those of typical landscaping treatment (due to the increased number of plantings, additional soil
excavation, backfill material, use of underdrains etc.), those landscaping expenses that would be
required regardless of the bioretention installation should be subtracted when determining the
net cost.
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Perhaps of most importance, however, the cost savings compared to the use of traditional
structural stormwater conveyance systems makes bioretention areas quite attractive financially.
For example, the use of bioretention can decrease the cost required for constructing stormwater
I conveyance systems at a site. A medical office building in Maryland was able to reduce the
amount of storm drain pipe that was needed from 80o to 230 feet - a cost savings of $24,000
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(PGDER, 1993). And a new residential development spent a total of approximately $ioo,000
using bioretention cells on each lot instead of nearly $400,000 for the traditional stormwater
ponds that were originally planned (Rappahanock,). Also, in residential areas, stormwater
management controls become a part of each property owner's landscape, reducing the public
I burden to maintain large centralized facilities.
Maintenance Cost
I The operation and maintenance costs for a bioretention facility will be comparable to those of
typical landscaping required for a site. Costs beyond the normal landscaping fees will include
the cost for testing the soils and may include costs for a sand bed and planting soil.
I References and Sources of Additional Information
Coffman, L.S., R. Goo and R. Frederick, 1999: Low impact development: an innovative
alternative approach to stormwater management. Proceedings of the 26th Annual Water
I Resources Planning and Management Conference ASCE, June 6-9, Tempe, Arizona.
Davis, A-P., Shokouhian, M., Sharma, H. and Minami, C., "Laboratory Study of Biological
I Retention (Bioretention) for Urban Stormwater Management," Water Environ. Res, 73(1), 5-14
(2001).
• Davis, A-P., Shokouhian, M., Sharma, H., Minami, C., and Winogradoff, D. "Water Quality
Improvement through Bioretention: Lead, Copper, and Zinc," Water Environ. Res., accepted for
publication, August 2002.
Kim, H., Seagren, E.A., and Davis, A.P., "Engineered Bioretention for Removal of Nitrate from
I Stomiwate Runoff," WEFTEC 2000 Conference Proceedings on CDROMResearcli
Symposium, Nitrogen Removal, Session 19, Anaheim CA, October 2000.
I Hsieh, C.-h. and Davis, A.P. "Engineering Bioretention for Treatment of Urban Stormwater
Runoff," Watersheds 2002, Proceedings on CDROM Research Symposium, Session 15, Ft.
I
Lauderdale, FL, Feb. 2002.
Prince George's County Department of Environmental Resources (PGDER), 1993. Design
Manual for Use of Bioretention in Stormwater Management. Division of Environmental
I Management, Watershed Protection Branch. Landover, MD.
U.S. EPA Office of Water, 1999. Stormwater Technology Fact Sheet: Bioretention. EPA 832-F-
99-012.
Weinstein, N. Davis, A.P. and Veeramachaneni, R. "Low Impact Development (LID) Stormwater
Management Approach for the Control of Diffuse Pollution from Urban Roadways," 5th
I International Conference DiffIise/Nonpoint Pollution and Watershed Management
Proceedings, C.S. Meiching and Emre Alp, Ed& 2001 International Watçr Association
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PRELIMINARY STORM WATER MANAGEMENT PLAN
I STATE STREET CONDOS
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APPENDIX I: APPLICABLE MANUFACTURER'S BMP INFORMATION
Please see attached.
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PRELIMINARY STORM WATER MANAGEMENT PLAN
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APPENDIX J: MAP EXHIBITS
Please see attached.
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