HomeMy WebLinkAboutMP 98-01F; Villages of La Costa Greens RV Storage Site; Conditional Use Permit (CUP) (2)HUNSAKER
&ASSOCL\TES
SAN DIECO,
PLANNING
ENGINEERINC
SURVEYING
IRVINE
LOS ANGELES
RIVERSIDE
SAN DIECO
STORM WATER
MANAGEMENT PLAN
for
LA COSTA GREENS
NEIGHBORHOODS 1.2 & 1.3
(RV SITE)
City of Carlsbad, California ^^^^ ^^^O|?T^
Prepared for:
Real Estate Collateral Management Company
1903 Wright Place
Suite 180
Carlsbad, CA 92008
w.o. 2352-141
January 22, 2006
DAVE HAMMAR
LEX WILLIMAN
ALISA VIALPANDO
DAN SMITH
RAY MARTIN
10179 Huennekens St.
San Diego, CA 92121
(858) 558-4500 PH
(858) 558-1414 FX
www.HunsakerSD.com
lnfo@HunsakerSD,com
PREUMINARY
Eric Mosolgo, R.C.E.
Water Resources Department Manager
Hunsaker & Associates San Diego, Inc.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
TABLE OF CONTENTS
CHAPTER 1 - Executive Summary
1.1 Introduction
1.2 Summary of Pre-Developed Conditions
1.3 Summary of Proposed Development
1.4 Results and Recommendations
1.5 Conclusion
1.6 References
CHAPTER 2 - storm Water Criteria
2.1 Regionai Water Quality Control Board Criteria
2.2 City of Carlsbad SUSMP Criteria
CHAPTER 3 - Water Quality Environment
3.1 Beneficial Uses
3.2 Surface Water
3.2.1 Surface Quality Objectives and Beneficial Uses
3.3 Groundwater
3.4 303(d) Status
3.5 Conditions of Concern - Developed Condition Hydrology Summary
3.6 Identification of Primary & Secondary Pollutants of Concern
CHAPTER 4 - Identification of Anticipated Pollutants from Project Site
4.1 Anticipated Pollutants from Project Site
4.2 Sediment
4.3 Nutrients
4.4 Trash & Debris
4.5 Oxygen-Demanding Substances
4.6 Oil & Grease
4.7 Pesticides
4.8 Organic Compounds
4.9 Metals
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
CHAPTER 5 - Flow-Based BMPs
5.1 Design Criteria
5.2 Grass-Lined Swales
5.3 FloGard Curb Inlet Filter Units
5.4 Pollutant Removal Efficiency
5.5 Maintenance Requirements
5.6 Schedule of Maintenance Activities
5.7 Annual Operations & Maintenance Costs
CHAPTER 6 - Source Control BMPs
6.1 Landscaping
6.2 Urban Housekeeping
6.3 Automobile Use
6.4 Integrated Pest Management Principles
6.5 Stenciling and Signage
6.6 Trash Storage Areas
6.7 Efficient Irrigation Practices
CHAPTER 7 - Site Design BMPs
7.1 Site Design BMPs
7.2 Minimize Impervious Footprint
7.3 Conserve Natural Areas
7.4 Permeable Pavements
7.5 Minimize Directly Connected Impervious Areas
7.6 Slope & Channel Protection / Hillside Landscaping
7.7 Residential Driveways & Guest Parking
CHAPTER 8 - Treatment Control BMP Design (Grassy Swale)
8.1 BMP Locations
8.2 Determination of Treatment Flows
8.3 Grassy Swale Sizing
8.4 BMP Unit Selection Discussion
8.4.1 Extended Detention Basins
8.4.2 Vegetated Swales
8.4.3 Infiltration Basins
8.4.4 WetPonds
8.4.5. Media Filters
8.4.6 Drainage Inserts
8.4.7 Hydrodynamic Separator Systems
CHAPTER 9 - Fiscal Resources
9.1 Agreements (Mechanisms to Assure Maintenance)
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
BMP LOCATION EXHIBIT
DEVELOPED CONDITIONS HYDROLOGY EXHIBIT
(pocket)
(pocket)
List of Tables and Figures
Chapter 1 - Vicinity Map
Chapter 1 - Watershed Map
Chapter 1 - BMP Location Map
Chapter 2 - Site Design and Source Control Storm Water BMP Requirements Matrix
Chapter 2 - Storm Water Applicability Checklist
Chapter 3 - Beneficial Uses Table
Chapter 3 - 2002 CWA Section 303(d) list
Chapter 4 - Pollutant Category Table
Chapter 5 - Pollutant Removal Efficiency Table (Flow-Based BMPs)
Chapter 5 - Grassy Swale Data
Chapter 5 - FloGard Unit Data
Chapter 8 - BMP Location Map
Chapter 8 - Design Runoff Determination Summary Tables
Chapter 8 - Grassy Swale Design Calculations
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Chapter 1 - EXECUTIVE SUMMARY
1.1 - Introduction
The La Costa Greens Neighborhood 1.2 &1.3 site is located adjacent to El Camino
Real, north of Poinsettia Lane and west of Alicante Road in the City of Carlsbad,
California (see Vicinity Map on this page).
Per the City of Carlsbad SUSMP, the La Costa Greens Neighborhoods 1.2 & 1.3
project is classified as a Priority Project and subject to the City's Permanent Storm
Water BMP Requirements.
This Storm Water Management Plan (SWMP) has been prepared pursuant to
requirements set forth in the City of Carlsbad's "Standard Urban Storm Water
Mitigation Plan (SUSMP)." All calculations are consistent with criteria set forth by the
Regional Water Quality Control Board's Order No. 2001-01, and the City of Carlsbad
SUSMP.
This SWMP recommends the location and sizing of a single on-site Best
Management Practice (BMPs), which will treat 85'^ percentile runoff priorto
discharging from the proposed site (see BMP Location Map in this chapter).
Furthermore, this report determines anticipated project pollutants, pollutants of
concern in the receiving watershed, recommended source control BMPs, and
methodology used forthe design of flow-based BMPs.
MJCAim ROAD BACKBONE STJ^ET ACCESS AND iWPflDVEMEWJS PER
DRAWNG NO. 3S7-2C
BACKBONE STREH ACCESS AND AffTOscyare PER OK. HO. 397-21 MD
LA COSTA VICINITYMAF
NOTE: eACKBONE lilPBOVEUENTS INdUDE SERWCf mOM WATER. 5EV€R. PQV€R. PHONE. CATV ETC
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
1.2 - Summarv of Pre-Developed Conditions
The existing La Costa Greens 1.1-1.3 has been mass graded per the "Grading &
Erosion Control Plans for La Costa Greens Neighborhoods 1.01-1.03" and is awaiting
future development.
Runoff from the mass graded site flows in a southeastern direction towards Poinsettia
Road, where it is intercepted via headwalls and then conveyed beneath Poinsettia
Road to the Alicante detention basin.
Flow from this basin then flows southwards to an unnamed tributary of San Marcos
Creek, which then flows in a southerly direction along the site boundary of the La
Costa Greens Golf Course, west ofthe Phase I development area. All the runoff
eventually drains under Alga Road via three 96" RCP culverts, as shown in Drawing
No. 397-2, and discharges into San Marcos Creek towards the Batiquitos Lagoon.
The Regional Water Quality Control Board has identified San Marcos Creek as part
ofthe Carlsbad Hydrologic Unit, San Marcos Hydrologic Area, and the Batiquitos
Hydrologic Subarea (basin number 904.51).
The existing condition hydrologic analysis ofthe La Costa Greens 1.1-1.3
development was completed and is discussed in the "Wass Graded Hydrology Study
for La Costa Greens Neighborhoods 1.1-1.3 & El Camino Real Widening", prepared
by Hunsaker & Associates, San Diego, Inc. and dated August 23, 2005.
1.3 - Summarv of Proposed Development
The proposed La Costa Greens Neighborhoods 1.1-1.3 are to be developed in
individual stages. The current development ofthis site incorporates a proposed RV
storage site within La Costa Greens Neighborhood 1.2. This development will
incorporate the paving of the RV storage site and a super-elevated paved roadway
connecting the site with the adjacent El Camino Real. There is a proposed AC berm
to be associated with this servicing road, conveying paved surface flows to the
proposed flow based BMPs.
This report does not include discussion on future residential development ofthe
northern portion of Neighborhood 1.2 and the adjacent Neighborhood 1.1. These will
remain in their current mass graded state.
Runoff from the developed RV site will discharge to one (1) curb outlet, located to the
south west corner of the future Neighborhood 1.3 project site. Developed site runoff
will be conveyed via the aforementioned super-elevated roadway to the mass graded
pad located to the south ofthe RV storage site. Runoff will then drain in a south
westerly direction via a proposed Grassy Swale to be constructed within the mass
graded pad. Flows will then drain to the receiving desilt basin located to the south
west ofthe project site priorto discharging from the project bounds.
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CARLSBAD
WATERSHED MAP FOR
LA COSTA GREENS
NEIGHBORHOODS 1.1-1.3
CITV OF CiUILSBAD, CAUFORNIA
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Flows that are not intercepted via the proposed grassy swale are then conveyed via
the AC berm to a curb inlet located at the entrance to the project site from the
adjacent El Camino Real. A FloGard Curb Inlet Filter unit will be located at the inlet
structure to provide treatment for flows generated by the proposed access road.
Development of the site will not cause any diversion to or from the existing San
Marcos Creek watershed.
All pipes will be sized for the 100-year event storm event. Detailed storm drain
system calculations will be provided at the final engineering phase.
Table 1 - Summary of Developed Conditions
Drainage Location Drainage Area
(Ac)
100-Year Peak Flow
(cfs)
Southern Outlet
(Neighborhood 1.3) 5.3 18.6
1.4 - Results and Recommendations
Table 2 below summarizes rational method 85"^ percentile calculations for the interim
grassy swale for the La Costa Greens Neighborhoods 1.2 & 1.3 development.
Table 2 - Developed Conditions 85*^ Percentile Calculations
Treatment
Unit
Drainage
Area
(acres)
Rainfall
Intensity
(inches/hour)
Runoff
Coefficient
85*^
Percentile
Flow (cfs)
RV Tributary
to Swale 0.5 0.2 0.87 0.1
Overall Swale
Tributary 2.7 0.2 0.6* 0.3
FloGard Inlet
Filter 0.8 0.2 0.55* 0.1
•• weighted C coefficient see Chapter 8
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Rational Method calculations predicted 85"^ percentile runoff flow of approximately
0.1 cfs from the proposed RV storage site. The swale however is tributary to an area
of approximately 2.7 Ac inclusive of the RV site, such that the interim treatment flow
directed to the swale is approximately 0.3 cfs. The rational method also
approximates a treatment flow of 0.1 cfs to be generated via the proposed roadway
to the south of the swale.
All treatment flows generated via the proposed RV storage site will be conveyed and
treated via the proposed grassy swale. As the swale is to be located in a currently
mass graded pad which is awaiting future residential development, the swale is
simply an interim treatment BMP for the RV site. Ultimate treatment for the RV site
and the surrounding residential developments will be addressed upon development
of these residential sites.
The map at the end ofthis chapter shows the location ofthe proposed site BMPs.
1.5 - Conclusion
The combination of proposed construction and permanent BMP's will reduce, to the
maximum extent practicable, the expected project pollutants and will not adversely
impact the beneficial uses of the receiving waters.
Many alternate treatment BMPs, including extended detention basins, infiltration
basins, wet ponds, media filters, drainage inserts and hydrodynamic separators were
explored and evaluated (see Chapter 8 for a full comparison on all treatment BMPs
considered). However, as the storm drain infrastructure is to be constructed at a
latter date (which will incorporate treatment control BMPs acceptable at the time of
future development), a grassy swale and inlet filter unit provide the best treatment
alternative.
Permeable pavements were also evaluated for implementation within the La Costa
Greens Neighborhoods 1.2 & 1.3 project site. However, due to several factors
including porous pavements high failure rate, porous pavements have been deemed
infeasible for the project site. A full discussion is provided within Chapter 7 of this
report.
An operations and maintenance plan will be submitted to the City during the Grading
Plan approval process.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
1.6 - References
"2002 C\NA Section 303(d) L/sf," California Regional Water Quality Control Board.
Hydrology Manual. County of San Diego Department of Public Works - Flood
Control Division; June 2003.
"Order No. 2001-01, NPDES No. CAS0108758 - Waste Discharge Requirements for
Discharges of Urban Runoff from the Municipal Separate Storm Sewer
Systems (MS4s) Draining the Watersheds ofthe County of San Diego, the
Incorporated Cities of San Diego County, and San Diego Unified Port District",
California Regional Water Quality Control Board - San Diego Region;
February 21, 2001.
"Water Quality Plan for the San Diego Basin", California Regional Water Quality
Control Board - San Diego Region, September 8, 1994.
'Tentative Map Drainage Study for La Costa Greens Neighborhoods 1.1-1.3",
Hunsaker & Associates Inc; January 2006.
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LEGEND
WATERSHED BOUNDARY
FLOWLINE
GRASSY SWALE
— TTTT 7—7—
Ri\051D\t.Hyd\0S10«H07- BMP-lS,dwgE 20853Jan-23-2006iia'd?
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Chapter 2 - STORM WATER CRITERIA
2.1 - Regionai Water Quality Control Board Criteria
All runoff conveyed in the proposed storm drain systems will be treated in compliance
with Regional Water Quality Control Board regulations and NPDES criteria prior to
discharging to natural watercourses. California Regional Water Quality Control
Board Order No. 2001-01, dated February 21, 2001, sets waste discharge
requirements for discharges of urban runoff from municipal storm separate drainage
systems draining the watersheds of San Diego County.
Per the RWQCB Order, post-development runoff from a site shall not contain
pollutant loads which cause or contribute to an exceedance of receiving water quality
objectives or which have not been reduced to the maximum extent practicable. Post-
construction Best Management Practices (BMPs), which referto specific storm water
management techniques that are applied to manage construction and post-
construction site runoff and minimize erosion, include source control - aimed at
reducing the amount of sediment and other pollutants - and treatment controls that
keep soil and other pollutants onsite once they have been loosened by storm water
erosion.
Post construction pollutants are a result ofthe urban development ofthe property
and the effects of automobile use. Runoff from paved surfaces can contain both
sediment (in the form of silt and sand) as well as a variety of pollutants transported by
the sediment. Landscape activities by homeowners are an additional source of
sediment.
All structural BMPs shall be located to infiltrate, filter, or treat the required runoff
volume or flow (based on the 85^^ percentile rainfall) prior to its discharge to any
receiving watercourse supporting beneficial uses.
2.2 - Citv of Carlsbad SUSMP Criteria
Perthe CityofCarlsbad SUSMP, the La Costa Greens Neighborhoods 1.2 & 1.3
project is classified as a Priority Project and subject to the City's Permanent Storm
Water BMP Requirements. These requirements required the preparation ofthis
Storm Water Management Plan.
The Storm Water Applicability Checklist, which must be included along with Grading
Plan applications, is included on the following page.
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storm Water Standards
4/03/03
11
-V1._RES0URCES &REFERENeES=_ --"^tt- —
APPENDIXA
STORM WATER REQUIREMENTS APPLICABILITY CHECKLIST
Complete Sections 1 and 2 of the following checklist to determine your project's
permanent and construction storm water best management practices requirements.
This form must be completed and submitted with your permit application.
Section 1, Permanent Storm Water BMP Requirements:
If any answers to Part A are answered "Yes,"' your project is subject to the "Priority
Project Permanent Storm Water BMP Requirements," and "Standard Permanent Storm
Water BMP Requirements" in Section III, "Permanent Storm Water BMP Selection
Procedure" in the Storm Water Standards manual.
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If all answers to Part A are "No," and any answers to Part B are "Yes," your project is
only subject to the "Standard Permanent Storm Water BMP Requirements". If every
question in Part A and B is answered "No," your project is exempt from permanent
storm water requirements.
Part A: Determine Priority Project Pennanent Storm Water BMP Requirements.
Does the project meet the definition of one or more of the priority project
categories?* Yes No
1. Detached residential development of 10 or more units >^
2. Attached residential deveiopment of 10 or more units X. 3. Commercial development greater than 100,000 square feet /
4. Automotive repair shop X
5. Restaurant
6. Steep hillside development greater than 5,000 square feet
7. Project discharqinq to receivinq waters within Environmentally Sensitive Areas X
8. Parking lots greater than or equal to 5,000 ft'' or with at least 15 parking spaces, and
potentiallv exposed to urban runoff %
9. Streets, roads, highways, and freeways which would create a new paved surface that is
5,000 square feet or greater X
* Refer to the definitions section in the Storm Water Standards for expanded definitions of the priority
project categories.
Limited Exclusion: Trenching and resurfacing work associated with utility projects are not considered
priority projects. Parking lots, buildings and other stmctures associated with utility projects are
priority projects if one or more of the criteria in Part A is met. If ail answers to Part A are "No",
continue to Part B.
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storm Water Standards
4/03/03
Part B: Determine Standard Permanent Storm Water Requirements
Does the project propose: Yes No
1. New impervious areas, such as rooftops, roads, parking lots, driveways, paths and
sidewalks? w
2. New pen/ious landscape areas and irrigation systems? X
3. Pennanent structures within 100 feet of anv natural water body? X
4. Trash storage areas? >
5. Liquid or solid material loadinq and unloading areas?
6. Vehicle or equipment fueiinq, washing, or maintenance areas? X
7. Require a General NPDES Permit for Storm Water Discharges Associated with
Industrial Activities (Except construction)?*
8. Commercial or industrial waste handling or storage, excluding typical office or
household waste? y
9. Any gradinq or qround disturbance durinq construction? X
10. Any new storm drains, or alteration to existing storm drains? X
'To find out if your project is required to obtain an individual General NPDES Perriiit for Storm Water
Discharges Associated with Industrial Activities, visit the State Water Resources Control Board web site
at, vwvw.swrcb.ca.qov/stonnwtr/industrial.html
Section 2. Construction Storm Water BMP Requirements:
If the answer to question 1 of Part C is answered "Yes," your project is subject to
Section IV, "Construction Storm Water BMP Performance Standards," and must prepare
a Stomn Water Pollution Prevention Plan (SWPPP). If the answer to question 1 is °No,°
but the answer to any of the remaining questions is "Yes," your project is subject to
Section IV, "Construction Storm Water BMP Performance Standards," and must prepare
a Water Pollution Control Plan (WPCP). If every question in Part C is answered "No,"
your project is exempt from any construction storm water BMP requirements. If any of
the answers to the questions in Part 0 are "Yes," complete the construction site
prioritization in Part D, below.
Part C: Determine Construction Phase Storm Water Requirements
Would the project meet any ofthese criteria during construction? Yes No
1. . Is-the project subject to Califomia's statewide General NPDES Permit for Stomn Water
Discharqes Associated With Construction Activities?
2. Does the project propose grading or soil disturbance? >
3. Would storm water or urban runoff have the potential to contact any portion of the
constmction area, includinq washinq and staging areas? X
4. Would the project use any construction materials that could negatively affect water
quality if discharged from the site (such as, paints, solvents, concrete, and
stucco)?
31
storni Water Standards
4/03/03
Part D: Determine Construction Site Priority
In accordance with the Municipal Permit, each constaiction site with construction storm
water BMP requirements must be designated with a priority: high, medium or low.
This prioritization must be completed with this form, noted on the plans, and included in
the SWPPP or WPCP. Indicate the project's priority in one of the check boxes using the
criteria below, and existing and surrounding conditions of the project, the type of
^ UWUVILI^O I lOwOOOdl y \^WIllpiCLC: Ll tC OWt lOkl UOLl Wl I Cll IU Cliiy WUI71 C/MCIIUQUII^
circumstances that may pose a threat to water quality. The City reserves the right to
adjust the priority of the projects both before and during construction. [Note:
The construction priority does NOT change construction BMP requirements that apply
to projects; all construction BMP requirements must be identified on a case-by-case
basis. The construction priority does affect the frequency of inspections that will be
conducted by City staff. See Section IV.1 for more details on construction BMP
requirements.]
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1) Projects where the site is 50 acres or more and grading will occur during the
II rainy season
1 2) Projects 5 acres or more. 3) Projects 5 acres or more within or directly
adjacent to or discharging directly to a coastal lagoon or other receiving water
p within an environmentally sensitive area
Projects, active or inactive, adjacent or tributary to sensitive water bodies
^ \ B) Medium Priority
1) Capital Improvement Projects where grading occurs, however a Storm Water
Pollution Prevention Plan (SWPPP) is not required under the State General
Construction Permit (i.e., water and sewer replacement projects, intersection
and street re-alignments, widening, comfort stations, etc.)
2) Permit projects in the public right-of-way where grading occurs, such as
installation of sidewalk, substantial retaining walls, curb and gutter for an
entire street frontage, etc., however SWPPPs are not required.
3) Permit projects on private property where grading permits are required,
however, Notice Of Intents (NOIs) and SWPPPs are not required.
• C) Low Priority
1) Capital Projects where minimal to no grading occurs, such as signal light and
loop installations, street light installations, etc.
2) Permit projects in the public right-of-way where minimal to no grading occurs,
such as pedestrian ramps, drive.way additions, small retaining walls, etc.
3) Permit projects on private property where grading permits are not required,
such as small retaining walls, single-family homes, small tenant
53 improvements, etc.
32
LAND DEVELOPMENT IVIANUAL- STORM W.i.TER STANDARDS MAY 2003
rable 1. Standard Deveiopment Project & Priorit/ Proisct Storm Water BMP Requirements Matrix,
BMPs Applicable to Individual
Priority Project Categories^'
Site
Design
BMPsf"
Source
Conirol a. Private Roads b. Residentlal Driveways & Guest Parkinq c. Dock Areas d. Maintenance Bays e.- Vehicle Wash Areas f. Equipmant V\/ash Areas g. Outdoor Processing 1 Areas h. Surface Parking Areas 1. Fueling Areas j. Hillside Landi;caping Treafmenf
Control
BMPs^"'
standard Projects R R 0 0 0 0 0 0 0 0' 0 0 0
Priority Projects:
Detached Residential
Development R R R R R S
Attached Residential
Development R R R s
Commercial
Development grealer
than 100,000 ft^
R R R R R R S
Automotive Repair
Shop R R R R R R R s
Restaurants R R R R S
Steep Hillsids
Development greater
than 5,000 ft"
R R R R S
Parking Lots R R S
streets. Highways &
Freeways R R s
R = Rsquired; select ons or more applicable and appropriate BMPs from the applicable steps in
Section I11.2.A-D, or equivalent as identified in Appendix C.
0 = Optional/ or may ba rsquirsd by City staff. As appropriate, applicants are encouraged to
incorporate treatment contro! BMPs and BMPs applicable to individual priority project categories
into the projact design. City staff may require one or more of these BMPs, v/here appropriate.
S = Select ons or mors applicable and appropriate treatmsnt controi BMPs from Appendix C.
(1) Refer to Section 111.2.A.
(2) Refer to Section 111.2.B.
(3) Priority project caiegories must apply specific storm water BMP requirements, where applicable.
Priority projects are subject to the requirements of all priority project categories that apply.
(4) Referto Section 1II.2.D.
(5) Applies if ths paved area totals >5,000 square fest or with >15 parking spaces and is potentially
exposed to urban mnoff.
B. Construction Stonn Water BMP Rsguirements
Projects subject to the construction storm water best management practices
requirements must comply with the standards included in Section IV, "Construction
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Managennent Plan
Chapter 3 - WATER QUALITY ENVIRONMENT
3.1 - Beneficial Uses
As shown in the watershed map on the following page, the pre-developed La Costa
Greens Neighborhoods 1.1-1.3 site drains to an unnamed tributary pf San Marcos
Creek which eventually discharges to the Batiquitos Lagoon within the San Marcos
Creek watershed.
Development of the site will not cause any diversion to or from the existing watershed
to the storm drain system.
The Regional Water Quality Control Board has identified San Marcos Creek as part
ofthe Carlsbad Hydrologic Unit, San Marcos Creek Watershed, and the Batiquitos
Hydrologic Subarea (basin number 904.51).
The beneficial use for this hydrologic subunit is found in the California Regional
Water Quality Control Board San Diego Region Basin Plan, dated May 5, 1998.
3.2 - Surface Waters
3.2.1. Surface Water Quality Objectives and Beneficial Uses
Beneficial uses for the Batiquitos Lagoon and San Marcos Creek include
agricultural supply, contact water recreation, non-contact recreation, warm
freshwater habitat, and wildlife habitat.
3.3 - Groundwater
No infiltration facilities will be used on site; therefore groundwater will not be an issue.
3.4 - 303(d) Status
Section 303(d) ofthe Federal Clean Water Act (CWA) requires the State to identify
surface waters that do not meet applicable water quality standards with certain
technology-based controls. The State Water Resources Control Board has approved
the 2002 303(d) List of Water Quality Limited Segment
The project location and watersheds have been compared to the current published
303(d) List of Water Quality Limited SegmenL and the nearest impaired water body is
the Pacific Ocean Shoreline at Moonlight State Beach, impaired by Bacterial
Indicators.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
3.5 - Conditions of Concern - Developed Condition Hydrology Summary
Table 3 below summarizes developed conditions drainage areas and resultant lOO-
year peak flowrates at the storm drain discharge location. Per San Diego County
rainfall isolpluvial maps, the design 100-year rainfall depth for the site area is 2.9
inches.
Table 3 - Summary of Developed Conditions Peak Flows
Drainage Location Drainage Area
(Ac)
100-Year Peak Flow
(cfs)
Southern Outlet
(Neighborhood 1.3) 5.3 18.6
Poinsettia Lane
36-inch RCP Headwall 42.8 64.4
Development ofthe mass graded La Costa Greens Neighborhood 1.1-1.3 site has
been anticipated per the "Master Detention Study for La Costa Greens" prepared by
Hunsaker & Associates and dated August 2003. Developed flows from the northern
portions ofthe La Costa Greens development, inclusive of flows from the near by
Bressi Ranch are conveyed via storm drain to the regional detention basin located at
the intersection of Alicante Road and Poinsettia Lane.
Per Dwg. 397-2H (attached), a headwall has been constructed to intercept flows
discharged from the La Costa Greens Neighborhood 1.1-1.3 site and tributary hillside
terrain. This receiving headwall discharges to an existing 36-inch RCP storm drain,
with a corresponding design capacity of 63.6 cfs. The proposed ultimate conditions
La Costa Greens Neighborhood 1.1-1.3 site drains approximately 64.4 cfs to this
receiving headwall, an increase of 0.8 cfs. As this is a very minor increase from that
ofthe design flow, the downstream receiving storm drain system will have negligible
impacts from the development of the project site.
Increase in developed flow due to the regional development ofthe La Costa Greens
(inclusive of Neighborhoods 1.1-1.3) project is mitigated by this large detention
facility. Routed flows are then conveyed in a southerly direction via the La Costa
Greens Golf Course, draining to three (3) 96-inch RCP culverts within Alga Road.
Peak flow rates listed above were generated based on criteria set forth in the "2003
San Diego County Hydrology Manual". For further information in regards to this
rational method analysis, please refer to the "TM Drainage Study for La Costa
Greens Neighborhoods 1.1 -1.3" dated January, 2006 by Hunsaker & Associates.
DE:DE h:\reports\2352M41\swmp02.l)oc
w.o. 2352-141 1/24/06 1:28 PM
WATERSHED BOUNDARY
INITIAL SUBAREA BNDY
PROJECT BOUNDARY
PROPOSED PROJECT BNDY
HYDROLOGY NODES
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•MP^ Kiinley4tom
ML-J and Associaies, Inc.
Enqln««rlng. Ranning and EnvIponm«nta1 Conatitants
ar Foi^th Avwiue - Suit* 301- Son DlBgo, Co. - SZW
Tali 1619)234-941 Taxi (619} 234-9433
ANO STREET IMPROVEICNTS
SEE DVG. aSST-2I.
CAUTIONI1
LOCATION OF EXISTING UTILITIES ON TIIESE PLANS ARE AfTROXIMATE ANO
SHALL BE VERIFIED BY CONTRACTOR
PRICR TO CONSTRUCTION.
SrOfiA/ DRA/N DATA
m. RAD/US REUARKS
ffl isf 01'3a' M34. 00-ISO. IS' 24- KCP (13S0-D)
(V) H34. 00' 271. 97' 24- HCP 11350-0)
ih i-S-IS'16-H34. 00' 131. 7T 36- RCP (I3SO-0)
N7S-00-09-E 4a. 79' J«' KCP 11350-01
«. 50' 2/. SJ' la' RCP (1350-D)
@ mO-35'32-W S2.4a-la- RCP (1350-01
{h N6S-35'3I-II 7. 45-JS- RCP (1350-0)
ih mo-30'3i-w 31.33-36- RCP (I3SO-0)
li-30-I6'4Z-90. 00' 46. 24-36' RCP (1350-0)
>rro-37-3s-£ 221. 05-36- RCP JI350-0)
s i.2B-29-29-«. 50' 23. OS-JS- RCP (1350-0)
Nia-OZ'03'E la. 31-ta' RCP (1350-D)
"WAT£R TIGHT JOIKTS
ENGINEER OF WORK
VALLECITOS WATER bISTRICT
TIMOTHY J. OEWITT R.C.E. 46579 DATE
(FOR antam onm
>«JT6N
GRAPHIC SCALE P= W
BENCHMARK;
0ESCRIPHCN:ST/WO4«O STREET SMNEt UODUMCHT
LOCATION: STA^SS^ £C 0* C£*r£/tt/«e OF a. CAmO REM.
RECORD FROH.-SW DIECO COumy VEHTICM. COKTmu RS-iB00.2Sa.e9
•AS BUILT"
REVIEWED BY:
s/2s/a^ A/twaezT* KvisEO smmi DHAiii MO SHEET
8 CITY OF CARLSBAD
ENCMmmC DEPARnENT
SHEETS
24 SRAOmS Tn SHEET
8 CITY OF CARLSBAD
ENCMmmC DEPARnENT
SHEETS
24 ^— Si
SHEET
8 CITY OF CARLSBAD
ENCMmmC DEPARnENT
SHEETS
24
EMMS AMD OtHMBE AAS
POINSETTIA LANE
AT LA COSTA GREENS
sTAitsaeo TO Btaai
EMMS AMD OtHMBE AAS
POINSETTIA LANE
AT LA COSTA GREENS
sTAitsaeo TO Btaai
EMMS AMD OtHMBE AAS
POINSETTIA LANE
AT LA COSTA GREENS
sTAitsaeo TO Btaai
EMMS AMD OtHMBE AAS
POINSETTIA LANE
AT LA COSTA GREENS
sTAitsaeo TO Btaai
EMMS AMD OtHMBE AAS
POINSETTIA LANE
AT LA COSTA GREENS
sTAitsaeo TO Btaai
APPROVED:^/'
OTY ENSINEER R.»!t"A.»* C»P V?T** 'D/TTE
DATC NTUL
REVISION OESCRPTION
DATE NTIAL DATE MTIAL DWN BY!
CHKO BY RVWD BY
PROJECT NO.
CTS9-03
DRAWING NO.
39r-2H ENCKEII OF nni REVISION OESCRPTION OTHEB APPROVU. arr APPROVAL
DWN BY!
CHKO BY RVWD BY -==
PROJECT NO.
CTS9-03
DRAWING NO.
39r-2H
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
3.6 - Identification of Primarv & Secondarv Pollutants of Concern
As stated previously in segment 3.4, the nearest 303(d) listed endangered water
body the La Costa Greens Neighborhoods 1.2 & 1.3 development is tributary to the
Pacific Ocean Shoreline at Moonlight State Beach. This water body is listed as being
sensitive to Bacterial Indicators.
Thus, there are no primary pollutants of concern from the proposed RV Storage Site.
Secondary pollutants generated by the project site include Nutrients Sediment,
Heavy Metals, Trash and Debris, Oil and Grease, Oxygen Demanding Substances,
Nutrients, Pesticides and Viruses & Bacteria.
DE:DE h:\report5\2352\141\swmp02.c)oc
w.o. 2352-141 1/22/06 3:32 PM
r n
WATEnSHEO MAP FOR
LA COSTA GREENS
NEIGHBORHOODS 1.1-1.3
CITY OP CAHLBOAD. CALIFORNIA
FIO
1
2002 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENT ^^^^ ' • '
SAN DIEGO REGIONAL WATER QUALITY CONTROL BOARD
KM KIN IMI N\Mi \\VII I Slill) I Ol I LI VM'MUI SSOK' Mil |{( I ><
I Mill I M IM\il I) I'KQPOSEDi^rMDL
I'KIOUin M/l Mi'PKGfEB.f *ico¥li>LEiTiON •
9 C PiiciricOccHiiSliorcliiic, Snn Diequito llll 90511000
Bactcriii ludiciilurii Low 0.86 Miles
Impainttciil healed at San Dieguito Lagoon Mouth, Solana Beach.
Nou|iaiiil/I'uiiit Source
9 C P.iciric Ocean Shoreline, SauJoiiquiii Hills 90I1I0U0
USA
BiK'teriii Iiidicnlors Low 0.63 Miles
Impait itieiil locaied al Cameo Cove al btine Cove Dr./Riviera Way. Heisier Pai k-Noi lh
Urban KuHoff/Sloriii Sewers
Unknown Nonpoini Source
liuliiiown poinl source
9 C Pacinc Ocean Sliurcllne, San Luis RcyllU 90311000
Bacleria Indicalors Low 0.49 Miles
hnpairineiu located at San Lui.s Rey River Month.
Nonpoinl/PuinI Source
9 C Pacific Ocean Shoreline, San Marcos IIA 90451000
Bacleria Indicalors Low 0.5 Miles
iDipuirmenI heated al Moonlight Slate Beach.
Nonpoiut/Poinl Source
^s^!KiB*^^,i3S^as^:^I^SiSi^^
9 C Pacific Ocean Shoreline, Scripps IIA 90630UOO
Bacleria Indicalors Medium 3.9 Miles
linpairinent healed at La Jolla Shores Beach at El Pasco Grande, La Jolla Shores Beach al Caininilo Del Oi o, La Jolla
Shores Beach at Vnllecilos, La Jolla Shores Beach cn Ave de la I'laya, Casa Beach (Childrens Pool), South Ca.ia Beach at
Coast Blvd., WliLipering Sands Beach al Ravina St., Windansea Beach at Visla de la Playa, Windansea Beach al Bonair St.,
Windansea Beach al Playa del Norte. Windansea Beach al Palomar.-Ive., Tourmaline Surf Park, Pacific Beach al Grand
Ave.
Nuupoinl/Puinl Source
9 C Pacific Ocean Shoreline, Tijuana nil 91111000
Bacteria Indicators Low 3 Miles
hiipairiiieni locatedfrom the border, extetiding norlh along the shore.
Nonpoinl/Poiul Source
9 R Pine Valley CrecU (Upper) 91141000
Enterococci Medium 2.9 Miles
Grazing-Related Sources
Concentriitcd Animal Feeding Opcraliuus
(permitted, poinl source)
I runsieni encampinenls
Page 7 of 16
^-'^I'-iS^^^N^' •««:xami i^jm^ -^jmm '^jmma >^mma niwiKui£fU c:v"-4JiiCS.KU s=';:jtBii»ii:'i:iJ =::..ii)it*>ja
Table 2-2. BENEFICIAL USES OF INLAIMD SURFACE WATERS
1.2
Inland Surface Waters . Hydrologic Unit
Basin Number
BENEFICIAL USE
1.2
Inland Surface Waters . Hydrologic Unit
Basin Number
M
U
N
A
G
R
1
N
D
P
R
0
C
G
W
R
F
• R
S
H
P
0
W
R
E
C
1
R
£
C
2
B
1
0
L
W
A
R
M
C
0
. L
D
W
1
L
D
R
A
R
E
S
P
W
N
Sdn DFego Counly Coastal Streams - continued
Buena Visla Lagoon 4.21 See Coaslal Waters-Table 2-3
Buena Vlsta Creek 4.22 e a a a 0)
Buena Vlsta Greek • 4.21 + ffi a a a a a -
Agua Hedionda 4.31 See Coaslal Waters- Tabla 2-3
Agua HetJionda Creek 4.32 o a o « 0 o a
Buena Creek 4.32 o 9 V a « a o
Agua Hedionda Crook 4.31 « 0 a a o a a
Leilerbox canyon 4.31 e a e 0 a o
Canyon de las Encinas 4.40 0 a a a
San Marcos Creek Watershed
Batiquitos Lagoon 4.51 See Coastal Walers- Table 2-3
San Marcos Creek 4.52 + a o o e tt
unnamed InlGrmlttent streams 4.53 o « a « a
San IViarcos Creek Walershod
San Marcos Creek 4.51 -1-s o « a a
Enclnllas Creek 4.51 + a o a o a
O Potential BDnaflclal Use
-1- Excepted From MUN (See Texl)
Walerbodies are listed mulliple limes If lhay cross Iiydrologic area or sub area boundaries.
Beneficial use deslgnallons apply lo all fribularies lo Ihe Indicated walerbody, if nol lisled separalely.
•falila 2-2
UENEFICIAL USES 2-27 March 12, 13U7
Table 2-3, BEIMEFICIAL USES QF COASTAL WATERS
Coastal Waters
Pacific Ocean
Dana Point Harbor
Del Mar Boat Basin
Mission Bay
Oceanside Harbor
San Diogo Bay
Coastal Lagoons
• Tijuana River Estuary
Moutli ot San Diego River
Los Penasquitos Lagoon
San Dieguito Lagoon
Batiquitos. Lagoon
San Elijo Lagoon
Aqua' Hedionda Lagoon
Hydroiogic
Unit Basin
Number
BENEFICIAL USE
I
N
D
N
A
V
n
E
C
2
C
.O
M
M
B
I
O
L
E
S
T
W
I
L
D
R
A
R
E
M
A
R
A
Q
U
A
M
I
G
n
s
p
W
N
11.11
7.11
6.10
B.11
4.51
. 5.61
4.31
&
1 Indudas the tidal prisms of the Otay and Sweotwnter.Rivers.
i Rshlno from shore or boat permittod, but olhar water contact reeraotional (REC-1) usos nro prohibited.
® Existing Beneficial Uso
Tablo 2-3
DENEPICIAL USES 2^7
W
A
R
M
S
l-l
E
L
L
Morch 12, 19Q7
^^d^h^mm^ MMm smsm mmm mMm mim^ •^'^^ at^!23a ,m»t»3Saa .^ctisiaa .r..^\ramm. .....<rm^ ....v.i.ita. .-...a--••
iS Table 3-3. WATER QUALITY OBJECTIVE
Concentrations not to ba exu-BBdad more than 10% of the time during any one year period.
Ground Water Hydrologic
Basin Unit
Number
Constituent {ma/L or aa noted)
Ground Water Hydrologic
Basin Unit
Number
TDS Cl S04 %Na N03 Fe Mn MBAS Q ODOR
Turb
NTU
Color
Units F
Buana Vlsta Creek HA 4.20
El Salto HSA a 4.21 3500 BOO 500 60 45 0.3 0.05 0,5 2.0 nono 5 15 1,0
Vlsta HSA a 4.22 1000 b 400 b-500 b 60 10 b 0.3 b 0.05 b 0.5 0.75 b none 5 15 1.0
Aoua Hedionda HA a 4.30 1200 500 500 60 10 0.3 0.05 0.5 0,76 nono 5 16 1.0
Los Monos HSA BJ 4.31 3G00 800 500 GO 45 0.3 0.05 0.5 2.0 none 5 15 1.0
Encinas • HA o 4.40 3500 b BOO ^ 500 b 60 45 b 0.3 b 0.05 l3 • 0.5 2.0 I' none 5 15 1.0
San Marcos HA ae 4.50 1000 400 BDO BD 10 0.3 . 0.05 0,5 0.75 none 5 16 1.0
Batiquitos HSA oak 4.51 3500 800 500 60 45 0.3 0.05 0.5 2.0 none 5 15 1.0
Escondldo Creek HA « 4.60 750 300 300 60 10 0.3 0.05 0.5 0.75 none 5 15 1.0
San Ellio . HSA a 4.61 2B00 700 600 60 45 0.3 O.OS O.G 1.0 none 5 15 1.0
Escondldo HSA 4.B2 1000 300 400 60 10 0.3 0.05. 0.5 0.75 none 5 15 1.0
SAN DIEGUITO HYDnOLOGIG UNIT 905.00
Solana Beach • • HA a G,10' 1E00 b 500 b 500 b 60 45 b 0.85 b 0.15 b 0.5 0.76 b none 5 16 1.0
Hod(jQ3 HA 5,20 1000 b 400 b 500 b 00 10 b 0.3 b 0.05 b d.s 0,75 b none 6 16 1.0'
San Pasqual HA B.30 1000 b 400 b 500 b 60 10 b 0.3 b 0.05 b 0.5 0.75 b nono B 15 1.0
Santa Maria Valley HA B.40 1000 400 BOO BO 10 0.3 O.OB .0.5 0.75 none 5 IB • 1.0
Santa Ysabel HA B.50 GOO 2G0 250 80 5 0.3 0.05 0.5 0.75 none 5 1G 1.0
PENASQUITOS HYDROLOGIC UNIT goo.oo
Miramar Reservoir HA 6.10 1200 500 600 60 10 0.3 0.05 0.5 0.75 none 5 1 5 1.0
Poway HA 6.20 7G0 q 300 300 60 10 0.3 0.05 0.5 0.75 none 5 15 1.0
Scripps • HA 8.30 ------------
Mlrnmnr HA 0 6.40 7G0 300 300 60 10 0.3 0.05 O.G 0.75 none 5 15 1.0
Tecolote HA 6.50 -------— " 1
HA - llydroloolo Araa
MSA - llydroloolo Sub Arco ILawor cacn lollors Intllcnto undnotaa lollowlno lha tablo.)
Tablo 3-3
WATEn QUALITY ODJECTIVES PODO 3-23 OclohDr 13, 1394
La Costa Greens Neighbortioods 1.2 & 1.3
Storm Water IVIanagement Plan
Chapter 4 - IDENTIFICATION OF TYPICAL POLLUTANTS
4.1 - Anticipated Pollutants from Project Site
Tlie following table details typical anticipated and potential pollutants generated by
various land use types. For this current piiase of tine La Costa Greens
Neighborhoods 1.2 & 1.3 development, the project site will consist of and RV site.
Thus, the Parking Lots and Streets and Highways and Freeways categories have
been highlighted to clearly illustrate which general pollutant categories are
anticipated from the project area.
General Pollutant Categories
Priority
Project
Categories Sediments Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances Oii & Grease Bacteria & Viruses Pesticides Detached
Residential
Development
X X X X X X X
Attached
Residential
Development
X X X p(i) p(2) P X
Commercial
Development
> 100,000 ft^
P<
1) pd) p(2) X p(5) X p(3) p(5)
Automotive
Repair Shops X X(4)(5) X X
Restaurants X X X X
Hillside
Development>
5,000 ff
X X X X X X
Parking Lots P'
1) pd) X X p(l) X pd)
Streets.
Highways &
Freeways
X pd) X X p(5)
X = anticipated
P = potential
(1) A potential pollutant if landscaping exists on-site.
(2) A potential pollutant if the project includes uncovered parking areas.
(3) A potential pollutant if land use involves food or animal waste products.
(4) Including petroleum hydrocarbons.
(5) Including solvents.
DE:DE h:\reportsV2352M41\svmip02.doc
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
4.2 - Sediment
Soils or other surface materials eroded and then transported or deposited by the
action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills,
reduce spawning habitat, smother bottom dwelling organisms, and suppress aquatic
vegetative growth.
4.3 - Nutrients
Inorganic substances, such as nitrogen and phosphorous, that commonly exist in the
form of mineral salts that are either dissolved or suspended in water. Primary
sources of nutrients in urban runoff are fertilizers and eroded soils. Excessive
discharge of nutrients to water bodies and streams can cause excessive aquatic
algae and plant growth. Such excessive production, referred to as cultural
eutrophication, may lead to excessive decay of organic matter in the water body, loss
of oxygen in the water, release of toxins in sediment, and the eventual death of
aquatic organisms.
4.4 - Trash & Debris
Examples include paper, plastic, leaves, grass cuttings, and food waste, which may
have a significant impact on the recreational value of a water body and aquatic
habitat. Excess organic matter can create a high biochemical oxygen demand in a
stream and thereby lower its water quality. In areas where stagnant water is present,
the presence of excess organic matter can promote septic conditions resulting in the
growth of undesirable organisms and the release of odorous and hazardous
compounds such as hydrogen sulfide.
4.5 - Oxvgen-Demanding Substances
Biodegradable organic material as well as chemicals that react with dissolved oxygen
in water to form other compounds. Compounds such as ammonia and hydrogen
sulfide are examples of oxygen-demanding compounds. The oxygen demand of a
substance can lead to depletion of dissolved oxygen in a water body and possibly the
development of septic conditions.
4.6 - Oil & Grease
Characterized as high high-molecular weight organic compounds. Primary sources
of oil and grease are petroleum hydrocarbon products, motor products from leaking
vehicles, oils, waxes, and high-molecular weight fatty acids. Elevated oil and grease
content can decrease the aesthetic value ofthe water body, as well as the water
quality.
DE:DE h:\reports\2352M41\smmp02.doc
w.o. 2352-141 1/22/06 3:17 PM
I
I
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water IVIanagement Plan
4.7 - Pesticides
Pesticides (including herbicides) are chemical compounds commonly used to control
nuisance growth or prevalence of organisms. Excessive application of a pesticide
may result in runoff containing toxic levels of its active component.
4.8 - Organic Compounds
Organic compounds are carbon-based. Commercially available or naturally occurring
organic compounds are found in pesticides, solvents and hydrocarbons. Organic
compounds can, at certain concentrations, indirectly or directly constitute a hazard to
life or health. When rinsing off objects, toxic levels of solvents and cleaning
compounds can be discharged to storm drains. Dirt, grease and grime retained in
the cleaning fluid or rinse water may also adsorb level of organic compounds that are
harmful or hazardous to aquatic life.
4.9 - Metals
Metals are raw material components in non-metal products such as fuels, adhesives,
paints and other coatings. Primary sources of metal pollution in storm water are
typically commercially available metals and metal products. Metals of concern
include cadmium, chromium, copper, lead, mercury and zinc. Lead and chromium
have been used as corrosion inhibitors in primer coatings and cooler tower systems.
At low concentrations naturally occurring in soil, metals are not toxic. However, at
higher concentrations, certain metals can be toxic to aquatic life. Humans can be
impacted from contaminated groundwater resources, and bioaccumulation of metals
in fish and shellfish. Environmental concerns, regarding the potential for release of
metals to the environment, have already led to restricted metal usage in certain
applications.
DE:DE h:Veporl5\2352M41\swnnp02.doc
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Chapter 5 - FLOW-BASED BMPs
5.1 - Design Criteria
Flow-based BMPs shall be designed to mitigate the maximum flowrate of runoff
produced from a rainfall intensity of 0.2 inch per hour. Such BMP's utilize either
mechanical devices (such as vaults that produce vortex effects) or non-mechanical
devices (based on weir hydraulics and specially designed filters) to promote settling
and removal of pollutants from the runoff.
Per the request of the County of San Diego, 85'^ percentile flow calculations were
performed using the Rational Method. The basic Rational Method mnoff procedure is
as follows:
Design flow (Q) = C * I * A
Runoff Coefficient C - In accordance with the County of San Diego standards, the
weighted runoff coefficient for all the areas draining to the treatment unit was
determined using the areas analyzed in the final engineering hydrology report. The
runoff coefficient is based on the following characteristics ofthe watershed:
- Land Use - RV/Automotive Storage Site
- Soil Type - Hydrologic soil group D was assumed for all areas. Group D
soils have very slow infiltration rates when thoroughly wetted. Consisting
chiefly of clay soils with a high swelling potential, soils with a high
permanent water table, soils with clay pan or clay layer at or near the
surface, and shallow soils over nearly impervious materials. Group D soils
have a very slow rate of water transmission.
Rainfall Intensity (I) - Regional Water Quality Control Board regulations and NPDES
criteria have established that flow-based BMPs shall be designed to mitigate a rainfall
intensity of 0.2 inch per hour.
Watershed Area (A) - Corresponds to total area draining to treatment unit.
5.2 - Grass Lined Swales
Grass-lined swales, herein referred to as grassy swale, is an example of a flow-
based BMP. Designed to trap pollutants through filtration, grassy swales have the
following basic requirements:
• Serves areas with soil groups C or D (A or B with liners)
• Maximum maintained side slopes = 3:1
• Water application rate = peak flow rate from water quality design storm
DE:DE h:\repoi1s\2352M41\swmp02-1.doc
w.o. 2352-141 1/23/06 12:57 PM
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Per the City of Portland, Oregon Storm Water Management Manual
(September 2000), the swale width and profile shall be designed to convey the water
quality design storm event as follows:
• Maximum design depth = 0.33 foot
• Maximum design velocity = 0.9 foot per second
• Hydraulic residence time > 9 minutes
• Minimum longitudinal slope = 0.5 percent
• Maximum longitudinal slope = 5 percent
• For longitudinal slopes > 5 percent, use check dams
• Use Manning "n" value of 0.25
• Minimum swale length = 100 feet
A minimum of 1 foot of freeboard above the standard storm design water surface
shall be provided for facilities not protected by high-flow diversion devices. Velocity
through the facility shall not exceed 3 feet per second during the high-flow events.
The swale shall incorporate a flow-spreading device at the inlet. The flow spreader
shall provide a uniform flow distribution across the swale bottom. In swales with a
bottom width greater than 8 feet, a flow spreader shall be installed at least every 100
feet. To minimize flow channelization, the swale bottom shall be smooth, with
uniform longitudinal slope, and with a minimum bottom width of 4 feet. Check dams
may need to be installed to reduce flow channelization.
Woody or shrubby vegetation shall not be planted in the active treatment area ofthe
swale. Grasses shall be established as soon as possible after the swale is
completed. Grasses shall be seeded within 2 days. The initial rate of application
shall be 5 pounds of see mix per 1,000 square feet, or as approved by the City.
A single grassy swale will be located on the mass graded pad to treat all 35**^
percentile treatment flows prior to discharging to the desilt basin located to the
southwest of the project site.
5.3 - FloGard Treatment Units
The treatment BMP's proposed forthe widening of El Camino Real incorporate the
use of a FloGard filter treatment unit for the storm drain system and energy
dissipation at the outfall.
FloGard filter treatment unit inserts are a flexible storm drain catchment and filtration
liner designed to collect contaminants and debris prior to discharge into storm drain
systems.
DE:DE h:Ve[iorts\2352\14Hswnip02-1.doc
w.o. 2352-141 1/23/06 12:57 PM
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
As perthe attached FloGard documents, FloGard filter treatment units are suitable
for all pollutants typically found on land developments, including heavy metals and
hydrocarbons.
The units are installed within the storm drain inlet, the pollutants being absorbed
within the FloGard filter treatment unit until it is replaced by a new filtration liner.
5.4 - Pollutant Removal Efficiencv Table
The table on the following page shows the generalized pollutant removal efficiencies
for bio swales and drainage inserts.
5.5 - Maintenance Reguirements
Grassy Swales
Maintenance for grassy swales is minimal and aimed at keeping grass cover dense
and vigorous. A pest management plan should be developed for vegetated areas
specifying how problem insects and weeds will be controlled with minimal use of
insecticides and herbicides. Lawn-mowing should be performed routinely throughout
the growing season. Grass height should be maintained at two inches above the
design water depth. Swales should be inspected at least twice annually to check for
erosion and damage to vegetation, debris and litter. Excess sediment should be
removed periodically as determined through inspection.
FloGard Inlet Filters
Maintenance ofthe FloGard filter treatment unit requires quarterly annual inspections
during the dry season (June through September) and monthly during the wet season
(October through May). The units need to be cleaned out quarterly to remove trash,
debris and excess sediment. The FloGard filter treatment unit requires replacing
annually at which time the filter shall be disposed of in accordance with state and
federal environmental protection requirements. The replacement filter is then placed
into the existing bracket within the downstream cleanout.
Maintenance ofthe site BMPs will be the responsibility ofthe Homeowners
Association. A maintenance plan will be developed and will include the following
information:
Specification of routine and non-routine maintenance activities to be
performed
A schedule for maintenance activities
Name, qualifications, and contact information for the parties responsible
for maintaining the BMPs
For proper maintenance to be performed, the storm water treatment facility must be
accessible to both maintenance personnel and their equipment and materials.
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m
pi
Chapter 4: Guidance for Selection of Permanent BIVIPs
Table 4.3 Treatment Control BIWP Selection Matrix'^'.
Pollutant of
Concern Treatment Control BMP Categories
Biofiiters Detention
Basins
Infiltration
Basins'^'
Wet Ponds
or Wetlands
Drainage
Inserts
Filtration Hydrodynamic
Separator
Systems'"
Sediment M H H H L H M
Nutrients L M M M L M L
Heavy
Metals M M M H L H L
Organic
Compounds • u U U M L M L
Trash &
Debris L . H U H M H M
Oxygen
Demanding
Substances
L M M M L M L
Bacteria u U H H L M L
0il&
Grease IVI M U U L H L
Pesticides U U U L L U L
(1) Copermittees are encouraged to periodically assess the perfomiance characteristics of many of these BMPs to
update this table.
(2) Including trencfies and porous pavemenL
(3) Also known as hydrodynamic devices and baffle boxes.
U Low removal efficiency):
M: Medium removal efficiency):
H: High removal efficiency):
U: Unknown removal efficiency
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
5.6 - Schedule of Maintenance Activities
5.6.1 Grassy Swale
Target Maintenance Dates - June 15"^, September 15'^^ (Dry Season Inspections)
Maintenance Activity - Inspection of swales, mowing and maintenance.
Target Maintenance Dates - 15**^ of each month; October through April (Rainy
Season Inspections)
Maintenance Activity - Inspection of swales, mowing and maintenance.
Target Maintenance Date - March 15'*^, June 15*^^, September 15'^, December 15"^
Maintenance Activity - Inspection of swales, mowing and maintenance.
5.6.2 FloGard Inlet Filters
Target Maintenance Dates - June 15*, September 15'*^ (Dry Season Inspections)
Maintenance Activity - Regular inspection to ensure that filter unit is functioning
properly, has not become clogged, and does not need to be replaced;
Target Maintenance Dates - 15'*^ of each month; October through April (Rainy
Season Inspections)
Maintenance Activity - Regular inspection to ensure that filter unit is functioning
properly, has not become clogged, and does not need to be replaced;
Target Maintenance Date - March 15"^, June 15"^, September 15"^, December 15'^
Maintenance Activity - Quarterly cleanouts; Cleanout filter, remove trash, debris
and excess sediment.
Target Maintenance Dates - March 15'^
Maintenance Activity - Annual filter replacement; Remove and replace filter.
Dispose of used filter according to state and federal environmental protection
guidelines. Place new filter in existing bracket below the storm drain entrance.
For proper maintenance to be performed, the storm water treatment facility must be
accessible to both maintenance personnel and their equipment and materials.
5.7 - Annual Operations & Maintenance Costs
The following costs are intended only to provide a magnitude ofthe costs involved in
maintaining BMPs. Funding shall be provided by the Home Owners Association for
the La Costa Greens development.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Approximate annual maintenance costs for the proposed grassy swale are outlined
below. Costs assume a 3 man crew:
Maintenance for Grassy Swales:
- Cut Vegetation to average height of 6" = $540
- Ensure adequate vegetation = $550
- Inspect for debris and sediment (General Maintenance) = $1,050
- Inspection = $750
Grassy Swale Subtotal = $2,890
Approximate annual maintenance costs forthe proposed FloGard filter treatment
units are outlined below. Costs assume a 3 man crew:
Periodic Inspection and Cleanout ($100 per inlet x 4 times annually
x 1 unit) = $400
Annual Filter Replacement = $200/unit x 1 inlet = $200
FloGard Subtotal = $600
BMP Subtotal = $3,490
10% Contingency = $349
Approximate Total Annual Maintenance Costs = $3,839
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Flo-Gard+Plus Rter installed
Flo-Gard™ +Plus
A multipurpose catch basin insert designed to capture sediment, debris, trash & oiis/grease from low (first flush) flows.
A (dual) high-flow bypass allows flows to bypass the device while retaining sediment and larger floatables (debris & trash)
AND allows sustained maximum design flows under extreme weather conditions.
Flo-Gard™ +Plus inserts are available in sizes to fit most industry-standard drainage inlets (...flat grated, combination,
curb and round inlets).
Flo-Gard™ -i-Plus catch basin inserts are recommended for areas subject to silt and debris as well as low-to-moderate
levels of petroleum hydrocarbon (oils and grease). Examples of such areas are vehicle parking lots, aircraft ramps, truck
and bus storage yards, corporation yards, subdivision streets and public streets.
Questions? Contact Kristar at (800) 579-8819. 05/03/04
Flo-Gard-*-Plus Filter
installed
SPECIFIER CHART
Model No.
inlet Width
(in)
Solids Storage
Capacity (cuft)
Filtered Fiow
(cfs)
Total Bypass
Cao. (cfs)
FGP-24a 24 0.9 0.8 5.6
F6P-30a 30 1.1 1.0 6.7
FGP-36a 36 1.4 1.2 7.9
FGP42a 42 1.6 1.4 8.8
FGP48a 48 1.9 1.5 9.9
FGP.5.OCI 60 2.3 1.8 11.6
FGP.6.0C1 72 2.8 2.2 13.8
FGP-7.0CI 84 3.2 2.5 15.9
FGP.«.OCI 96 3.7 2.9 18.0
FGP-IO.Oa 120 4.6 3.5 21.9
FGP-12.0a 144 5.6 4.2 26.2
FGP-14.0CI 168 6.5 4.9 30.1
FGP-16.0CI 192 7.5 5.6 34.4
FGP-18.0CI 216 8.3 6.2 38.2
FGP-21.0a 252 9.7 7.2 44.3
FGP-28.0a 336 13.0 9.5 58.6
NOTES:
1. storage capacity reflects 80% of maximuni solids
collection prior to impeding filtering bypass.
2. Filtered flow rate includes a safety factor of 2.
3. Ro-Gard+Plus Catch Basin Rlter inserts are available
In the standard sizes (see above) or in custom sizes.
Call for details on custom size inserts.
4. Available with recessed mount package including ig
tray alovang maintenance access from manhole.
5. Ro-Gard+Plus filter inserts should be used in conjunction
with a regular maintenance program. Referto
manufacturei's recommended maintenance guidelines.
US PATENT
FLO-GARD™+PLUS
CATCH BASIN FILTER INSERT
(Curb Mount)
CURB INLET
KriStar Enterprises, Inc., Santa Rosa, CA (800) 579-8819
05/04
Kristar Enterprises, Inc.
1219 Briggs Avenue
PO Box 7352
Santa Rosa, CA 95407-0352
(800) 579-8819
FloGard® -i-Plus Performance Assessment in City of Honolulu Testing
FloGard -i-Plus catch basin insert filters were recently evaluated in an 18-month field study
commissioned by the City of Honolulu, Hawaii and conducted by the University of Hawaii to assess the
effectiveness and practical utility of catch basin insert filters. (Df four catch basin insert filters tested,
only two were recommended as viable for implementation, including the FloGard® -i-Plus. Results for
the FloGard® -i-Pius indicated:
> 80% removal of typical road sediment (effective filtration down to 100 lirn - see chart below) in
short-term testing.
> 20-40% PAH removal.
> Effective metal retention associated with sediment removal.
> Viable for large scale urban implementation based on evaluation of performance, installation
and maintenance features and costs.
Of those filters recommended for potential use in the City, FloGard® -i-Plus provided the most TSS
removal capability and the only local sales and service.
u. c o
ts
n
u.
Honolulu Street Deposited Sediment Profile
Material sampled from 400 block of Cooke St., Kakaako Area
120.0
100.0
80.0
60.0
40.0
20.0 -
0.0
10 100 1000
Particle Size (micron)
10000
- Honolulu Road Sediment -Woodward-Clyde (a\^) (1997) NURP (1986)
09/04
Grassy Swale
Collection/ overflow facility at
downstream end of swale to acceptable
disposal point per Section 1.4
2 ft. min.
flat
Bottom
for
private, 4
ft. min.
for public
6" to 12"
swale depth
Minimum 12"
depth growing
medium
6 ft. Minimum, 12 ft. Maximum
Section Not to Scale ermeable filter fabric,
optional
Stormwater Management Goals Achieved Acceptable Sizing Methodologies
V PoUution Reduction SlMi, PRES^
V Flow Control SIM^
V Destination/ Disposal PRES^
This facility is not classified as an Underground Injection Control structure (UIC).
SIM=Simplified Approach, PRES= Presumptive Approach, PERF= Performance Approach
Notes: 1) Flow and volume contiol credit will only be given for projects with less than
15,000 square-feet of impervious area to manage. 2) For projects with more than
15,000 square-feet of impervious area to manage, the presumptive approach must be
used to size the swale for pollution reduction, and additional facilities may be
required to meet flow contiol requirements. Grassy swales can be used to manage
runoff from parking lots, rooftops, and private stieets. For public stieet runoff, the
stieet swale criteria must be used. 3) The surface infiitiation facility design procedure
frnm fiprtinn 2.2-2 mav bp ii.<;prl tn rprpivp rrpdit fnr .<?tnrmwatpr rlisnn.«;al
Stormwater Management Manual
Adopted July 1,1999; revised September 1, 2004
Page 2-69
Grassy Swale
Description: Grassy swales are long narrow grassy depressions used to collect
and convey stormwater runoff, allowing pollutants to settle and filter out as the
water infiltiates into the ground or flows through fhe facility. In addition to
providing pollution reduction, flow rates and volumes can also be managed for
small projects (<15,000 square feet of impervious surface) with grassy swales.
Swales should be integrated into the overall site design and can be used to help
fulfill a site's required landscaping area requirement. An approved conveyance
and disposal method per Section 1.4 will be required at the end of the swale.
Design Considerations: When designing grassy swales, slopes and depth should
be kept as mild as possible to avoid safety risks and prevent erosion within the
facility.
Construction Considerations: Grassy swale areas should be clearly marked
before site work begins to avoid soil disturbance during constiuction. No
vehicular tiaffic, except that specifically used to construct the facility, should be
allowed within 10 feet of swale areas.
Design Requirements:
Soil Suitability: Grassy swales are appropriate for all soil types. Topsoil shall be
used within the top 12 inches of the facihty, or the soil shall be amended per
Appendix F to support plant growth.
Dimensions and Slopes: Facility storage depth may vary from 6 to 12 inches.
Maximum side slopes are 4 horizontal to 1 vertical. Minimum flat bottom width
is 2 feet for private swales, and 4 feet for public swales. Maximum longitudinal
slope is 5%, while minimum slope is 0.5%. Maximum surrounding groimd
slopes shall be 10%.
Stormwater Management Manual
Adopted July 1,1999; revised September 1, 2004
Page 2-70
Grassy Swale
Setbacks: Required setback from centeriine of swale to property lines is 5 feet,
and 10 feet from building foimdations unless lined with impermeable fabric.
Sizing: Grassy swales sized with the simplified approach shall be designed to
receive less than 15,000 square-feet of impervious area runoff. For these projects,
a simplified approach sizing factor of 0.1 may be used to receive credit for
pollution reduction and flow contiol. A high-flow by-pass mechanism will not
be required in these cases, but a high-flow overflow must be provided at the
downstteam end of the swale to an approved disposal point, per Section 1.4. In
cases when pollution reduction is the only stormwater management goal, or
there is more than 15,000 square feet of impervious area to manage, the
presumptive approach must be used size the swale for pollution reduction, and
additional facilities will be required to meet flow control requirements, where
applicable.
Presumptive Approach Sizing Criteria:
Exhibit 2-15 shows swale side slopes of 4:1 and lengthwise slopes of IV2 percent,
3 percent, and 5 percent. These charts are based on the City standards shown
below and may be used to easily determine swale length, given the peak flow
rate and the desired swale bottom width.
Stormwater Management Manual Page 2-71
Adopted July 1,1999; revised September 1, 2004
Grassy Swale
0)
.0)
ra c
_J
n
(0
180
170
160
150
140
130
120
110
100
90
Exhibit 2-15 (Sheetl)
Swale Length at 1.5% Longitudinal Slope
Bottom Width = 4'
Bottom Width = 6'
Bottom Width = 8'
slopes are 4:1
length is
0.2 0.4 0.6
Flow Rate, Q, cfs
0.8
Stormwater Management Manual
Adopted July 1,1999; revised September 1, 2004
Page 2-72
Grassy Swale
270
250
230
•S 210
.0)
Exhibit 2-15 (Sheet 2)
Swale Length at 3.0% Longitudinal Slope
Swale Data
Side slopes are 4:1
Minimum length is ICQ'
0.2 0.4 0.6 0.8
Flow Rate, Q, cfs
340
0)
Exhibit 2-15 (Sheet 3)
Swale Length at 5.0% Longitudinal Slope
Bottom Width = 6'
Swale Data
Side slopes are 4:1
Minimum lengtti Is 100'
Bottom Widtti = 4'
Stormwater Management Manual
Adopted July 1,1999; revised September 1, 2004
Page 2-73
Grassy Swale
1) The swale width and profile shall be designed to convey runoff from the
pollution reduction design storm intensity (see Section 1.5.2) at:
• Maximum design depth of 0.33 feet.
• Maximum design velocity of 0.9 feet per second.
• Minimum hydrauhc residence time (time for Qdesign to pass through
the swale) of 9 minutes.
• Minimum longitudinal slope of 0.5 percent, maximum slope of 5
percent. For slopes greater than 5 percent, check dams shall be used
(one 6-inch high dam every 10 feet).
• Designed using a Manning "n" value of 0.25.
• 4:1 (or flatter) side slopes in the tteatment area.
• Minimum length of 100 feet.
A minimum of 1 foot of freeboard above the water surface shall be
provided for facilities not protected by high-flow storm diversion devices.
Swales without high-flow diversion devices shall be sized to safely convey
the 25-year storm event, analyzed using the Rational Method (peak 25-
year, 5 minute intensity = 3.32 inches per hour).
Velocity through tiie faciHty shall not exceed 3 feet per second (fps) during
the high-flow events (i.e., when flows greater than those resulting from
the pollution reduction design intensity are not passed around the
facility).
2) The swale shall incorporate a flow-spreading device at the inlet. The flow
spreader shall provide a uniform flow disttibution across the swale
bottom. In swales with a bottom width greater than 6 feet, a flow
spreader shall be installed at least every 50 feet.
3) To minimize flow channelization, fhe swale bottom shall be smooth, with
uniform longitudinal slope, and with a minimum bottom width of 2 feet
for private facihties and 4 feet for public facilities. Maximum bottom
width shall be 8 feet.
4) Grasses or sod shall be established as soon as possible after the swale is
completed, and before water is allowed to enter the faciUty.
5) Unless vegetation is estabUshed, biodegradable erosion conttol matting
appropriate for low-velocity flows (approximately 1 foot per second) shaU
be installed in the flow area of the swale before allowing water to flow
through the swale.
Stormwater Management Manual Page 2-74
Adopted July 1,1999; revised September 1, 2004
Grassy Swale
6) Access routes to the swale for maintenance purposes must be shown on the
plans. PubUc swales wiU need to provide a minimum 8-foot wide access
route, not to exceed 10 percent in slope.
Stormwater Report Requirements For Presumptive Approach: See Exhibit 2-2.
Landscaping: Plantings shaU be designed at the foUowing quantities per 200
square feet of faciUty area. Facility area is equivalent to the area of the swale
calculated from Form SIM. (Note: Facilities smaller than 200 square feet shall
have a minimum of one tiee per facUity.):
1 Evergreen or Deciduous ttee:
Evergreen ttees: Minimum height: 6 feet.
Deciduous ttees: Minimum caliper: 1 Vi inches at 6 inches above
base.
Grass: Seed or sod is required to completely cover the grassy swale
bottom and side slopes. (Shrubs are optional)
For the swale flow path, approved native grass mixes are preferable and may be
substituted for standard swale seed mix. Seed shaU be applied at the rates
specified by the suppUer. The applicant shall have plants established at the time
of facUity completion (at least 3 months after seeding). No runoff shall be
allowed to flow in the swale until grass is estabUshed. Trees and shrubs may be
aUowed in the flow path within swales if the swale exceeds the minimum length
and widths specified.
Native wildflowers, grasses, and ground covers used for BES-maintained
facUities shaU be designed not to require mowing. Where mowing cannot be
avoided, faciUties shall be designed to require mowing no more than once or
twice annuaUy. Turf and lawn areas are not aUowed for BES-maintained
facUities; any exceptions wUl require BES approval.
Enviroiunental zones shall meet requirements established by Titie 33 for grass in
E-zones.
*Link to Grassy Swale Recommended Seed Mixes
Checklist of minimal information to be shown on the permit drawings:
(Additional information may be required on the drawings during permit review,
depending on individual site conditions.)
Stormwater Management Manual Page 2-75
Adopted July 1,1999; revised September 1, 2004
Grassy Swale
1) Facility dimensions and setbacks from property lines and sttuctures
2) ProfUe view of facUity, including typical cross-sections with dimensions
3) Growing medium specification
4) FUter fabric specification (if appUcable)
5) AU stormwater piping associated with fhe facility, including pipe materials,
sizes, slopes, and invert elevations at every bend or connection
6) Landscaping plan
Inspection requirements and schedule: The following table shall be used to
determine which stormwater facility components require City inspection, and
when the inspection shall be requested:
Facility Component Inspection Requirement
Swale grading Call for inspection
Piping CaU for inspection
FUter fabric (if applicable)
Growing medium
Plantings/ seeding/ sod Call for inspection
Operations and Maintenance requirements: See Chapter 3.0.
* Link to grassy swale O&M form
Additional photos and drawings:
* Link to grassy swale photos
* Link to grassy swale drawings
Stormwater Management Manual Page 2-76
Adopted July 1,1999; revised September 1, 2004
La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water IVIanagement Plan
Chapter 6 - SOURCE CONTROL BMPS
6.1 - Landscaping
Manufactured slopes shall be landscaped with suitable ground cover or installed with
an erosion control system. Homeowners will be educated as to the proper routine
maintenance to landscaped areas including trimming, pruning, weeding, mowing,
replacement or substitution of vegetation in ornamental and required landscapes.
Perthe RWQCB Order, the following landscaping activities are deemed unlawful and
are thus prohibited:
Discharges of sediment
Discharges of pet waste
Discharges of vegetative clippings
Discharges of other landscaping or construction-related wastes.
6.2 - Urban Housekeeping
Fertilizer applied by homeowners, in addition to organic matter such as leaves and
lawn clippings, all result in nutrients in storm water runoff. Consumer use of
excessive herbicide or pesticide contributes toxic chemicals to runoff. Homeowners
will be educated as to the proper application of fertilizers and herbicides to lawns and
gardens.
The average household contains a wide variety of toxins such as oil/grease,
antifreeze, paint, household cleaners, and solvents. Homeowners will be educated
as to the proper use, storage, and disposal of these potential storm water runoff
contaminants.
Perthe RWQCB Order, the following housekeeping activities are deemed unlawful
and are thus prohibited:
Discharges of wash water from the cleaning or hosing of impervious surfaces
including parking lots, streets, sidewalks, driveways, patios, plazas, and
outdoor eating and drinking areas (landscape irrigation and lawn watering, as
well as non-commercial washing of vehicles in residential zones, is exempt
from this restriction)
Discharges of pool or fountain water containing chloride, biocides, or other
chemicals
Discharges or runoff from material storage areas containing chemicals, fuels,
grease, oil, or other hazardous materials
Discharges of food-related wastes (grease, food processing, trash bin wash
water, etc.).
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
6.3 - Automobile Use
Urban pollutants resulting from automobile use include oil, grease, antifreeze,
hydraulic fluids, copper from brakes, and various fuels. Homeowners will be
educated as to the proper use, storage, and disposal ofthese potential storm water
contaminants.
Perthe RWQCB Order, the following automobile use activities are deemed unlawful
and are thus prohibited:
Discharges of wash water from the hosing or cleaning of gas stations, auto
repair garages, or other types of automotive sen/ice facilities.
Discharges resulting from the cleaning, repair, or maintenance of any type of
equipment, machinery, or facility including motor vehicles, cement-related
equipment, port-a-potty servicing, etc.
Discharges of wash water from mobile operations such as mobile automobile
washing, steam cleaning, power washing, and carpet cleaning.
The Homeowners Association will make all homeowners aware of the
aforementioned RWQCB regulations through a homeowners' education program
(educational homeowner material is attached at the end of this chapter).
6.4 - Integrated Pest Management (IMP) Principles
Integrated pest management (IPM) is an ecosystem-based pollution prevention
strategy that focuses on long-term prevention of pests or their damage through a
combination of techniques such as biological control, habitation manipulation,
modification of cultural practices, and use of resistant plant varieties. Pesticides are
used only after monitoring indicates they are needed according to established
guidelines. Pest control materials are selected and applied in a manner that
minimizes risks to human health, beneficial and non-target organisms, and the
environment. More information may be obtained at the UC Davis website
(http://www.ipn.ucdavis.eduAA/ATER/U/index.html).
IPM is achieved via the following:
- Eliminate and/or reduce the need for pesticide use in the project design by:
(1) Plant pest resistant or well-adapted plant varieties such as native plants.
(2) Discouraging pests by modifying the site and landscape design.
Pollution prevention is the primary "first line of defense" because pollutants
that are never used do not have to be controlled or treated (methods which
are inherently less efficient).
- Distribute IPM educational materials to future site residents/tenants.
Minimally, educational materials must address the following topics:
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La Costa Greens Neighborhoods 1.2 & 1.3
storm Water Management Plan
(1) Keeping pests out of buildings and landscaping using barriers, screens
and caulking.
(2) Physical pest elimination techniques, such as, weeding, squashing,
trapping, washing, or pruning out pests.
(3) Relying on natural enemies to eat pests.
(4) Proper use of pesticides as a last line of defense.
6.5 - Storm Water Convevance Svstems Stenciling and Signage
The proposed development will incorporate concrete stamping, or equivalent, of all
storm water conveyance system inlets and catch basins within the project area with
prohibitive language (e.g., "No Dumping - I Live in «name receiving water»"),
satisfactory to the City Engineer. Stamping may also be required in Spanish.
6.6 - Trash Storage Areas
All outdoor trash container areas shall meet the following requirements. A "trash
containment area" refers to an area where a trash receptacle or receptacles are
located for use as a repository for solid wastes. Design for such areas will include:
- Paved with an impervious surface, designed not to allow run-on from
adjoining areas, screened or walled to prevent off-site transport of trash.
- Provide attached lids on all trash containers that exclude rain, roof or awning
to minimize direct precipitation.
6.7 - Efficient Irrigation Practices
All Home Owners' Association (HOA) maintained landscaped areas will include rain
shutoff devices to prevent irrigation during and after precipitation. Flow reducers and
shutoff valves triggered by pressure drop will be used to control water loss from
broken sprinkler heads or lines.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Chapter 7 - SITE DESIGN BMPS
7.1 - Site Design BMPs
Priority projects, such as the La Costa Greens Neighborhoods 1.2 & 1.3
development, shall be designed to minimize, to the maximum extent practicable the
introduction of pollutants and conditions of concern that may result in significant
impact, generated from site runoff to the storm water conveyance system. Site
design components can significantly reduce the impact of a project on the
environment.
As the La Costa Greens Neighborhoods 1.2 & 1.3 development is currently a
Tentative Map stage development and no specific site plan has been developed for
the future Neighborhood 1.3 site, the following site design techniques have been
proposed to be possibly implemented within the precise grading design at the Final
Engineering stage of the development.
7.2 - Minimize Impervious Footprint
Methods of accomplishing this goal include:
- Constructing streets, sidewalks, and parking lots to the minimum widths
necessary without compromising public safety.
- Incorporating landscaped buffer areas between sidewalks and streets.
- Minimizing the number of residential street cul-de-sacs and incorporate
landscaped areas to reduce their impervious cover.
- Increase building density while decreasing the building footprint.
- Reduce overall lot imperviousness by promoting alternative driveway surfaces
and shared driveways that connect two or more homes together.
- Reduce overall imperviousness associated with associated with parking lots
by providing compact car spaces, minimizing stall dimensions, incorporating
efficient parking lanes and using porous pavement materials in spillover
parking areas.
7.3 - Conserve Natural Areas
The proposed La Costa Greens Neighborhoods 1.2 & 1.3 site has been mass graded
per the "Grading & Erosion Control Plans for La Costa Greens Neighborhoods 1.01-
1.03" and is awaiting future development.
As such, there currently is no natural area to conserve in ultimate developed
conditions.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
7.4 - Permeable Pavements
Site design BMP alternatives such as pen/ious pavements were also considered for
use within the La Costa Greens Neighborhoods 1.2 & 1.3 project site. However, the
use of pervious pavements has several disadvantages such as:
Many pavement engineers and contractors lack expertise with this
technology.
Porous pavement has a tendency to become clogged if improperly
installed or maintained.
Porous pavement has a high rate of failure.
Anaerobic conditions may develop in underlying soils if the soil is
unable to dry out between storm events. This may impede
microbiological decomposition.
Clay soils typically found within the project site are not sufficiently
permeable to convey storm water runoff - leading to possible soil
swelling and ultimately cracking of the pavement layer.
These factors listed influenced the decision to not include pervious pavements within
the site design.
7.5 - Minimize Directiv Connected Impervious Areas
Methods of accomplishing this goal include:
Draining rooftops into adjacent landscaping prior to discharging to the
storm drain.
Draining parking lots into landscape areas co-designed as biofiltration
areas.
Draining roads, sidewalks and impervious trails into adjacent
landscaping.
7.6 - Siope & Channel Protection / Hillside Landscaping
Methods of accomplishing this goal include:
Use of natural drainage systems to the maximum extent practicable.
Stabilize permanent channel crossings.
Planting native or drought tolerant vegetation on slopes.
Energy dissipaters, such as riprap, at the outlets of new storm drains,
culverts, conduits, or channels that enter unlined channels.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
7.7 - Residentiai Drivewavs & Guest Parking
As this is a multi-family residential development and not a single family residential
development, no driveways have been proposed for the project site. Residences are
serviced by communal private alley's, with no allowance for parking of vehicles in this
area.
As such, no site design has been specified forthis purpose.
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La Costa Greens Neighborhoods 1.2 & 1.3
storm Water Management Plan
Chapter 8 - TREATMENT CONTROL BMP DESIGN
GRASSY SWALE
8.1 - BMP Locations
Runoff from the developed site will discharge to one (1) curb outlet, located to the
south west corner of the future Neighborhood 1.3 project site. Developed site runoff
will be conveyed via the aforementioned super-elevated roadway to the mass graded
pad located to the south ofthe RV storage site. Runoff will then drain in a south
westerly direction via a proposed Grassy Swaie to be constructed within the mass
graded pad. Flows will then drain to the receiving desilt basin located to the south
west of the project site prior to discharging from the project bounds.
Flows that are not intercepted via the proposed grassy swale-are then conveyed via
the AC berm to a curb inlet located at the entrance to the project site from the
adjacent El Camino Real. A FloGard Curb Inlet Filter unit will be located at the inlet
structure to provide treatment for flows generated by the proposed access road. See
attached BMP exhibit.
8.2 - Determination of Design Treatment Flows
The 85**^ percentile design flow rates have been calculated using the Rational
Method. Required data for the Rational Method treatment flow determination include
the following:
- Runoff Coefficient (C)
- Rainfall Intensity (I) = 0.20 inches per hour
Drainage area to treatment unit (A)
The following table summarizes the parameters used for determination of design
flows to the Grassy Swale.
DESIGN RUNOFF DETERMINATION SUMMARY TA BLE
Treatment
Unit
Drainage
Area
(acres)
Rainfall
Intensity
(inches/hour)
Runoff
Coefficient
85*^
Percentile
Flow (cfs)
RV Tributary
to Swale 0.5 0.2 0.87 0.1
Overall Swale
Tributary 2.7 0.2 0.6* 0.3
FloGard Inlet
Filter 0.8 0.2 0.55* 0.1
: weighted 0 coefficient
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Rational Method calculations predicted 85'^ percentile runoff flow of approximately
0.1 cfs from the proposed RV storage site. The swale however is tributary to an area
of approximately 2.7 Ac inclusive ofthe RV site, such that the interim treatment flow
directed to the swale is approximately 0.3 cfs. The rational method also
approximates a treatment flow of 0.1 cfs to be generated via the proposed roadway
to the south of the swale.
8.3 - Grassv Swale Sizing
The grassy swale has been designed with a 4 foot bottom width, a depth of 0.33 ft, a
channel slope of 1 % and a side slope of 1:3. The required flow length to attain the 9
minute hydraulic residence time is 135 linear feet. Based on these parameters,
calculations (included at the end of this chapter) show the grassy swales are capable
of treating a peak flow of 0.4 cfs (refer to section 8.2 for treatment flow determination
and treatment flow determination spreadsheets at the end of this chapter).
8.4 -BMP Unit Selection Discussion
8.4.1 Extended Detention Basins
Extended detention basins collect the first flush runoff volume and retain it in the
basin for a period of 24-48 hours.
85'^ percentile runoff volume, contained below the overflow elevation ofthe basin
riser, will be slowly discharged from the treatment control basin via low flow orifices in
the basin riser. After passing through the riser, an outlet pipe will dewater the basin
and discharge runoff to the natural drainage course downstream.
Advantages
• Due to the simplicity of design, extended detention basins are relatively
easy and inexpensive to construct and operate.
• Extended detentions basins can provide substantial capture of
sediment and the toxics fraction associated with particulates.
• Widespread application with sufficient capture volume can provide
significant control of channel erosion and enlargement caused by
changes to flow frequency relationships resulting from the increase of
impervious cover in the watershed.
Limitations
• Limitation of the diameter of the orifice may not allow use of extended
detention in watersheds of less than 5 acres (would require an orifice
with a diameter of less than 0.5 inches that would be prone to clogging).
• Dry extended detention ponds have only moderate pollutant removal
when compared to some other structural stormwater practices, and they
are relatively ineffective at removing soluble pollutants.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
Dry ponds can detract from the value of a home due to the adverse
aesthetics of dry, bare areas and inlet and outlet structures.
Conclusion:
Due to the minimal footprint area available for the BMP treatment units, construction
of an extended detention basin is not a feasible option for the La Costa Greens
Neighborhoods 1.2 & 1.3 project site.
8.4.2 Vegetated Swale
Vegetated swales are open, shallow channels with vegetation covering the side
slopes and bottom that collect and slowly convey runoff through filtering by the
vegetation in the channel, filtering through a subsoil matrix, and/or infiltration into the
underlying soils. Swales can be natural or manmade. They trap particulate
pollutants (suspended solids and trace metals), promote infiltration, and reduce the
velocity of stormwater runoff. Vegetated swales can serve as part of a stormwater
drainage system and can replace curbs, gutters and stormwater systems.
Advantages
• If properly designed, vegetated, and operated, swales can serve as an
aesthetic, potentially inexpensive urban development or roadway
drainage conveyance measure with significant collateral water quality
benefits.
Limitations
Can be difficult to avoid channelization.
May not be appropriate for industrial sites or locations where spills may
occur.
Grassed swales cannot treat a very large drainage area. Large areas
may be divided and treated using multiple swales.
A thick vegetative cover is needed for these practices to function
properly.
They are impractical in areas with steep topography.
They are not effective and may even erode when flow velocities are
high, ifthe grass cover is not properly maintained.
In some places, their use is restricted by law: many local municipalities
require curb and gutter systems in residential areas.
Swales are more susceptible to failure if not properly maintained than
other treatment BMPs.
Conclusion:
Due to site design constraints (lack of drainage infrastructure), a grassy swale
provides the most practical treatment option for the RV project site.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
8.4.3 Infiltration Basins
An infiltration basin is a shallow impoundment that is designed to infiltrate
stormwater. Infiltration basins use the natural filtering ability ofthe soil to remove
pollutants in stormwater runoff. Infiltration facilities store runoff until it gradually
exfiltrates through the soil and eventually into the water table. This practice has high
pollutant removal efficiency and can also help recharge groundwater, thus helping to
maintain low flows in stream systems. Infiltration basins can be challenging to apply
on many sites, however, because of soils requirements. In addition, some studies
have shown relatively high failure rates compared with other management practices.
Advantages
• Provides 100% reduction in the load discharged to surface waters.
• The principle benefit of infiltration basins is the approximation of pre-
development hydrology during which a significant portion ofthe average
rainfall runoff is infiltrated and evaporated rather than flushed directly to
creeks.
• If the water quality volume is adequately sized, infiltration basins can be
useful for providing control of channel forming (erosion) and high
frequency (generally less than the 2-year) flood events.
Limitations
• May not be appropriate for industrial sites or locations where spills may
occur.
• Infiltration basins require a minimum soil infiltration rate of 0.5
inches/hour, not appropriate at sites with Hydrologic Soil Types C and
D.
• Infiltration rates exceeding 2.4 inches/hour, the runoff should be treated
prior to infiltration to protect groundwater quality.
• Not suitable on fill sites or steep slopes.
• Risk of groundwater contamination in very coarse soils.
• Upstream drainage area must be completely stabilized before
construction.
• Difficult to restore functioning of infiltration basins once clogged.
Conclusion:
Due to the type D clay soils typically located in the region and limited footprint
available, infiltration basins are not a feasible option forthe La Costa Greens
Neighborhoods 1.2 & 1.3 project site.
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storm Water Management Plan
8.4.4 Wet Ponds
Wet ponds are constructed basins that have a permanent pool of water throughout
the year (or at least throughout the wet season) and differ from constructed wetlands
primarily in having a greater average depth. Ponds treat incoming stormwater runoff
by settling and biological uptake. The primary removal mechanism is settling as
stormwater runoff resides in this pool, but pollutant uptake, particularly of nutrients,
also occurs to some degree through biological activity in the pond. Wet ponds are
among the most widely used stormwater practices. While there are several different
versions ofthe wet pond design, the most common modification is the extended
detention wet pond, where storage is provided above the permanent pool in orderto
detain stormwater runoff and promote settling.
Advantages
• If properly designed, constructed and maintained, wet basins can
provide substantial aesthetic/recreational value and wildlife and wetland
habitat.
• Ponds are often viewed as a public amenity when integrated with a park
setting.
• Due to the presence of the permanent wet pool, properly designed and
maintained wet basins can provide significant water quality
improvements across a relatively broad spectrum of constituents
including dissolved nutrients.
• Widespread application with sufficient capture volume can provide
significant control of channel erosion and enlargement caused by
changes to flow frequency relationships resulting from the increase of
impervious cover in a watershed.
Limitations
• Some concern about safety when constructed where there is public
access.
• Mosquito and midge breeding is likely to occur in ponds.
• Cannot be placed on steep unstable slopes.
• Need for base flow or supplemental water if water level is to be
maintained.
• Require a relatively large footprint.
• Depending on volume and depth, pond designs may require approval
from the State Division of Safety of Dams.
Conclusion:
Due to the minimal footprint area available forthe BMP treatment units and proximity
to residences (vector issues) wet ponds are not a feasible option for the La Costa
Greens Neighborhoods 1.2 & 1.3 project site.
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La Costa Greens Neighborhoods 1.2 & 1.3
storm Water Management Plan
8.4.5 Media Filters
Stormwater media filters are usually two-chambered including a pre-treatment
settling basin and a filter bed filled with sand or other absorptive filtering media. As
stormwater flows into the first chamber, large particles settle out, and then finer
particles and other pollutants are removed as stormwater flows through the filtering
media in the second chamber.
Advantages
Limitations
Relatively high pollutant removal, especially for sediment and
associated pollutants.
Widespread application with sufficient capture volume can provide
significant control of channel erosion and enlargement caused by
changes to flow frequency relationships resulting from the increase of
impervious cover in a watershed.
More expensive to construct than many other BMP's.
May require more maintenance than some other BMP's depending
upon the sizing of the filter bed.
Generally require more hydraulic head to operate properly (min 4 feet).
High solids loads will cause the filter to clog.
Work best for relatively small, impervious watersheds.
Filters in residential areas can present aesthetic and safety problems if
constructed with vertical concrete walls.
• Certain designs maintain permanent sources of standing water where
mosquito's and midge breeding is likely to occur.
Conclusion:
Due to the minimal footprint area available forthe BMP treatment units and overall
unit cost, media filters are not a feasible option for the La Costa Greens
Neighborhoods 1.2 & 1.3 project site.
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La Costa Greens Neighborhoods 1.2 & 1.3
Storm Water Management Plan
8.4.6 Drainage Inserts
Drainage inserts are manufactured filters or fabric placed in a drop inlet to remove
sediment and debris. There are a multitude of inserts of various shapes and
configurations, typically falling to one of three different groups: socks, boxes and
trays. The sock consists of a fabric, usually constructed of polypropylene. The fabric
may be attached to a frame or the grate of the inlet holds the sock. Socks are meant
for vertical (drop) inlets. Boxes are constructed of plastic or wire mesh. Typically a
polypropylene "bag" is placed in the wire mesh box. The bag takes form of the box.
Most box products are one box; that is, the setting area and filtration through media
occur in the same box. Some products consist of one or more trays and mesh
grates. The trays may hold different types of media. Filtration media vary by
manufacturer. Types include polypropylene, porous polymer, treated cellulose and
activated carbon.
Advantages
• Does not require additional space as inserts as the drain inserts are
already a component of the standard drainage systems.
• Easy access for inspection and maintenance.
• As there is no standing water, there is little concern for mosquito
breeding.
• A relatively inexpensive retrofit option.
Limitations
• Performance is likely significantly less than treatment systems that are
located at the end ofthe drainage system such as ponds and vaults.
• Usually not suited for large areas or areas with trash or leaves that can
plug the insert.
Conclusion:
Due to site design restraints and efficiency of treatment for pollutants generated via
the proposed access roadway and adjacent mass graded pad, a single curb inlet
filter at the receiving inlet south of the grassy swale provides the most feasible
treatment alternative at this location.
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La Costa Greens Neighborhoods 1.2 & 1.3
storm Water Management Plan
8.4.7 Hydrodvnamic Separator Svstems
Hydrodynamic separators are flow-through structures with a settling or separation
unit to remove seciiments and other pollutants that are widely used in storm water
treatment. No outside power source is required, because the energy of the flowing
water allows the sediments to efficiently separate. Depending on the type of unit, this
separation may be by means of swirl action or indirect filtration. Variations of this unit
have been designed to meet specific needs. Hydrodynamic separators are most
effective where the materials to be removed from runoff are heavy particulates -
which can be settled - or floatables -which can be captured, ratherthan solids with
poor settleability or dissolved pollutants. In addition to the standard units, some
vendors offer supplemental features to reduce the velocity ofthe flow entering the
system. This increases the efficiency of the unit by allowing more sediments to settle
out.
Advantages
• May provide the desired performance in less space and therefore less
cost.
• May be more cost-effective pre-treatment devices than traditional wet or
dry basins.
• Mosquito control may be less of an issue than with traditional wet
basins.
Limitations
• As some of the systems have standing water that remains between
storms, there is concern about mosquito breeding.
• It is likely that vortex separators are not as effective as wet vaults at
removing fine sediments, on the order 50 to 100 microns in diameter
and less.
• The area served is limited by the capacity of the largest models.
• As the products come in standard sizes, the facilities will be oversized
in many cases relative to the design treatment storm, increasing cost.
• The non-steady flows of stormwater decreases the efficiency of vortex
separators from what may be estimated or determined from testing
under constant flow.
• Do not remove dissolved pollutants.
• A loss of dissolved pollutants may occur as accumulated organic matter
(e.g., leaves) decomposes in the units.
Conclusion
Due to site design constraints (lack of drainage infrastructure), a hydrodynamic
separator unit was deemed infeasible for the project site. At the ultimate
development phase however, a hydrodynamic unit could be viable.
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85TH PERCENTILE PEAK FLOW AND VOLUME DETERMINATION
Modified Rational Method - Effective for Watersheds < 1.0 mi^
Hunsaker & Associates - San Diego
Note: Only Enter Values in Boxes - Spreadsheet Will Calculate Remaining Values
Project Name La Costa Greens 1.2 & 1.3 |
Work Order 2352-141 1
Jurisdiction City of Carslbad |
BMP Location [Grassy Swale - RV Tributary
Developed Drainage Area = 0.6 acres
Natural Drainage Area = 0.0 acres
Total Drainage Area to BiVIP = 0.6 acres
Dev. Area Runoff Coefficient = 0.87
Runoff Coefficient = 0.87
RATIONAL METHOD RESULTS
Q = CIA where Q = 85th Percentile Peak Flow (cfs)
C = Runoff Coefficient
I = Rainfall Intensity (0.2 inch/hour per RWQCB mandate)
A = Drainage Area (acres)
Using the Total Drainage Area:
C = 0.87
I = 0.2 inch/hour
A = 0.6 acres
Q= 0.10 cfs
85TH PERCENTILE PEAK FLOW AND VOLUME DETERMINATION
Modified Rational Method - Effective for Watersheds < 1.0 mi^
Hunsaker & Associates - San Diego
Note: Only Enter Values in Boxes - Spreadsheet Will Calculate Remaining Values
Project Name La Costa Greens 1.2 & 1.3 |
Work Order 2352-141 1
Jurisdiction City of Carslbad |
BMP Location |Curb Inlet Filter
Developed Drainage Area = 0.8 acres
Natural Drainage Area = 0.0 acres
Total Drainage Area to BMP = 0.8 acres
Dev. Area Runoff Coefficient = 0.55
Runoff Coefficient = 0.55
RATIONAL METHOD RESULTS
Q = CiA where Q = 85th Percentile Peak Flow (cfs)
C = Runoff Coefficient
I = Rainfall Intensity (0.2 inch/hour per RWQCB mandate)
A = Drainage Area (acres)
Using the Total Drainage Area:
C = 0.55
I = 0.2 inch/hour
A = 0.8 acres
Q = 0.09 cfs
85TH PERCENTILE PEAK FLOW AND VOLUME DETERMINATION
Modified Rational Method - Effective for Watersheds < 1.0 mi^
Hunsaker & Associates - San Diego
Note: Only Enter Values in Boxes - Spreadsheet Will Calculate Remaining Values
Project Name La Costa Greens 1.2 & 1.3 |
Work Order 2352-141 1
Jurisdiction City of Carslbad 1
BMP Location jCrassy Swale - OVERALL Tributary"
Developed Drainage Area = 2.7 acres
Natural Drainage Area = 0.0 acres
Total Drainage Area to BMP = 2.7 acres
Dev. Area Runoff Coefficient = 0.60
Nat. Area Runoff Coefficient =
Runoff Coefficient = 0.60
RATIONAL METHOD RESULTS
Q = CiA where Q = 85th Percentile Peak Flow (cfs)
C = Runoff Coefficient
I = Rainfall Intensity (0.2 inch/hour per RWQCB mandate)
A = Drainage Area (acres)
Using the Total Drainage Area:
C =
I =
A =
Q =
0.60
0.2 inch/hour
2.7 acres
0.32 cfs
Rational Method Results at: Grassy Swale
0.87 0.35
Development Area (ac)
1.30 1.40
c =
Sum of Areas 1.3 1.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 = 2.7 ac.
45.7% impervious % Impervious 95 0 =
2.7 ac.
45.7% impervious
Weighted Average C = 0.60
Rational Method Results at: Curb Inlet Filter
0.87 0.35
Development Area (ac)
0.30 0.50
c =
Sum of Areas 0.3 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 = 0.8 ac.
% Impervious 95 0 = 35.6% impervious
Weighted Average C = 0.55
Worksheet for Trapezoidal Channel - 1
Project Description
Flow Element:
Friction Method:
Solve For;
Input Data
Roughness Coefficient:
Channel Slope:
Normal Depth:
Left Side Slope:
Right Side Slope:
Bottom Width:
Result?
Discharge:
Flow Area:
Wetted Perimeter:
Top Width:
Critical Depth:
Critical Slope:
Velocity:
Velocity Head:
Specific Energy:
Froude Number:
Flow Type:
GVF Input Data
Downstream Depth:
Length:
Number Of steps:
GVF Output Data
Upstream Depth:
Profile Description:
Headloss:
Downstream Velocity:
Upstream Velocity:
Normal Depth:
Critical Depth:
Channel Slope:
Trapezoidal Channel
Manning Formula
Discharge
0.250
0.01000
0.33
3.00
3.00
4.00
0.41
1.65
6.09
5.98
0.07
2.28357
0.25
0.00
0.33
0.08
Subcritical
0.00
0.00
0
0.00
N/A
0.00
0.00
0.00
0.33
0.07
0.01000
ft/ft
ft
ft/ft (H:V)
ft/ft (H:V)
ft
ftVs
ft=
ft
ft
ft
ft/ft
ft/s
ft
ft
ft
ft
ft
ft/s
ft/s
ft
ft
ft/ft
Cross Section for Trapezoidal Channel - 1
Project Description
Flow Element:
Friction Method:
Solve For:
Section Data
Roughness Coefficient:
Channel Slope:
Normal Depth:
Left Side Slope:
Right Side Slope:
Bottom Width:
Discharge:
Trapezoidal Channel
Manning Formula
Discharge
0.250
0.01000
0.33
3.00
3.00
4.00
0.41
ft/ft
ft
ft/ft (H:V)
ft/ft (H:V)
ft
ftVs
0.33 «
.4,00 ft.
WATERSHED BOUNDARY
ELOWLINE
GRASSY SWALE
—7 7 I —TT^
Ri\O510M,Hyd\0510$HO7-BMP-lE.dw9[ Boe5]jQn-23-2006il3i03
La Costa Greens Neighborhoods 1.2 & 1.3
storm Water Management Plan
Chapter 9 - FISCAL RESOURCES
9.1 - Agreements (Mechanisms to Assure Maintenance)
There is a Grassy Swale and Curb Inlet Filter Unit within the proposed La Costa
Greens Neighborhoods 1.2 & 1.3 for storm water quality treatment.
Funding for the water quality treatment devices will be provided by the La Costa
Greens HOA. The La Costa Greens HOA will be responsible to perform the
maintenance activities and to ensure adequate funding.
The City of Carlsbad Watershed Protection, Stormwater Management, and Discharge
Control Ordinance require ongoing maintenance of BMPs to ensure the proper
function and operation of theses BMPs. The treatment unit will require maintenance
activities as outlined in Section 5 of this report.
It should be noted that this is an intenm BMP for the RV site only. At the ultimate stage
ofdevelopmeni, a larger BMP treatment control alternative will be constructed per future
residential development of the adjacent mass graded pads.
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