HomeMy WebLinkAboutCT 03-13; BLACK RAIL RIDGE; STORM WATER MANAGEMENT PLAN; 2003-08-28I
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ENGINEERING
Pro f e s s ion a lei v i lEn gin e era n d Lan d S II r iJ e y o' r
STORM WATER MANAGEMENT PLAN
for
Black Rail Ridge Tentative Map
Prepared for:
Pacific Coast Development
6575 Black Rail Road567 San Nocolas Drive, Suite 130
Newport Beach, CA 92660
949759-7720
Project Site Address
S.W. Corner, Black Rail Road & Poinsettia, Carlsbad, CA 92009
Prepared by:
Michael L. Benesh, R.C.E. 37893
Date:
August 28, 2003
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX 760 897-2165 • E-MAIL: MLBENESH@PAGB"ELL.NET
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Engineering
storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentotive Map
Contents
Section 1. Introduction ................................................................................. ~.~ ............ 3
Section 1.01 Introduction ..................................................................................... ~ .... 3
Section 2. Project ........................................................................................................ ~
Section 2.01 Description ............................................................................................ 3
Section 2.02 Topography and Land Use .............................................................. .4
Section 2.03 Hydrologic Unit Contributions .......................................................... .4
Section 3. Water Quality Environment ....................................................... ~ ............... 4
Section 3.01 Beneficial Uses ........................................................................ ~ ........... ~4 -
3.01.1 Inland Surface Waters .........................................................•.............. 6,
3.01.2 Grou ndwater ....................................................................................... 6
Section 3.02 303(d) Status ............................................................... _ ..... .-.................... 6
Section 4. Characterization of Project Runoff ........ _ ...•.......................................... _ .... 6
Section 4.01 Existing and Post Construction Drainage ......•................................ 6
Section 4.02 Post-Construction Expected Discharges ................................. , ...... 8
Section 4.03 3.3 Soil Characteristics ........................................................................ 9 '
Section 5. Mitigation Measures To Protect Water Quality ....................................... 9
Section 5.01 Construction BMPs .............................................................................. 9
Section 5.02 Post-construction BMPs .................................................................... 10
5.02.1 Site Design BMPs .... ~ ........................................................................... 1 0
5.02.2 Source Control BMPs ........................................................................ 1 0
5.02.3 Treatment Control BMPs .................................................................. 11
5.02.3(i) Bio-Filters .................................................................... : .................. 11
5.02.3 (i) (a) Appropriate Applications and Siting Constraints: ......... 11
5.02.3{ii) Gravel Check Dams ............................................................... -... 12-
5.02.3 (ii) (a) Appropriate Applications ....................................... , ........... 13
Section 6. Operation and Maintenance Program ....•......................•........•......••.....•. 14
Section 6.01 Bio-Filters .................................. : ........................................................... 14
6.01.1 Inspection Frequency ...................................................................... 14
6.01.2 Aesthetic and Functional Maintenance ..................................... 14
6.01.2(i) Aesthetic Maintenance ............................................................ 15
6.01.2(ii) Functional Maintenance .......................................................... 15 .
6.01.2 (ii) (a) Preventive Maintenance .................................................... 15
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Engineering
storm W~r Management Plan (SWMP)
Black Rail Ridge Tentative Map
6.01.2 (ii) (b) Corrective Maintenance .................................................... 16
6.01.3 Maintenance Frequency ................................................................ 17
6.01.4 Debris and Sediment Disposal. ....................................................... 1 7
Section 6.02 Gravel Chack Dams ......................................................................... 17
6.02.1 Inspection Frequency ...................................................................... 17
6.02.2 Aesthetic and Functional Maintenance ..................................... 17
6.02.2(i) Aesthetic Maintenance ............................•............................... 18
6.02.2(ii) Functional Maintenance .......................................................... 18
6.02.2 (ii) {a} Preventive Maintenance .................................................... 18
6.02.2 (ii)(b) Corrective Maintenance .................................................... 18
6.02.3 General Facility Maintenance ....................................................... 19
6.02.4 Maintenance Frequency ................................................................ 19
6.02.5 Debris and Sediment Disposal ........................................................ 19
Section 7. Mechanisms to Assure Maintenance ..•......•.••••.....•••......•..•.••••....•.....••... 19
Section 7.01 Stormwater Ordinance Requirement: .......................................... 20
Section 7.02 Public Nuisance Abatement: ...................................................... : .. 20
Section 7.03
Section 7.04
Section 7.05
Notice to Purchasers ........................................................................ 20
Subdivision Public Report ................................................................ 20
Funding: ............................................................................ ·.· .................. 20
Section S.
Section 9.
Summary Conclusions •..••••.•.........••.•..•.••....•.................•••...••.......•........•• 21'
Certification ............................................ ~ ................................................ 22
Attachment A -Vicinity" Map ........................................................................................... ~ ••• A-l
Attachment B -Site Plan ...................................................................................................... B-1
Attachment C -Computation Sheet for Runoff Coefficients •••••...•••••••••••••••••••••••••••••••••.• C-1
Affachment D -Drainage Study ....................................................................................•. ~ .. 0-1
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storm Wafer Management Pian (SWMP)
Black Rail Ridge Tentative Map
Engineering
Section 1.
Introduction
Section 1.01 Introduction
The storm Water Management Plan (SWMP) requirement is required under the County
of San Diego Watershed Protection, Storm Water Management, and Discharge
Control Ordinance (section 67.817). The purpose of this SWMP is to address the water
quality impacts from the proposed improvements on the Black Rail Ridge Subdivision.
Best Management Practices (BMPs) will be utilized to provide a long-term solution to
water quality. This SWMP is also intended to ensure the effectiveness of the BMPs
through proper maintenance that is based on long-term fiscal planhing. The SWMP is
subject to revisions as needed by the engineer.
Section 2.
Project
Section 2.01 Description
The project is a 3.6 acre site located in the City of Carlsbad, California.
The site is bordered by Black Rail Road on the East, an as of yet l)nnamed and
unpaved Street 'A' on the South and Poinsettia Lane on the North.
The site is adjacent to single family homes on South and North. The southerly homes
being located on 1 + acre parcels and the northerly homes in a residential subdivision.
The proposed project will subdivide the existing parcel of land into 11 lots of
approximately one-quarter acres each. Construction will include street and utility
improvements along Black Rail Road, Poinsettia Lane, Street "A" and Street "B", as well
as on-site grading to create building pads. The amount of anticipated grading is
approximately 9,000 cubic yards.
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Engineering
Section 2.02 Topography and Land Use
Storm Waler Management Plan .(SWMP)
Black Rail Ridge Tentative Map
The site is currently being used for agricultural purposes and has no permanent
structures.
The surface of the land falls from the East to the West, with Black Rail Road being the
high side of the site. Storm water runoff currently drains across the site to the westerly
property line via sheet flow and concentrated flow in the unimproved Street I A". From
there, it continues across the neighboring properties in a similar manner until it reaches
a natural drainage area on the southerly side of Poinsettia approximately 600 feet
West of the site.
Through a series of storm drain culverts and natural drainage areos the strom water
runoff from this site eventually reaches the Batiquitos Lagoon and the Pacific Ocean.
After development, the existing drainage pattern will remain for the site.
Section 2.03 Hydrologic Unit Contributions
The project is located in the Batiquitos watershed and in the Carlsbad hydrologic unit·
(904.51). The project drains via surface flow to the west, and eventually, through a
series of storm drain culverts and natural drainage areas the strom water runoff from
this site eventually reaches the Batiquitos Lagodn and the Pacific Ocean.
Section 3.
Water Quality Environment
Section 3.01 Beneficial Uses
The beneficial uses for the hydrologic unit are included in Tables 3.1 and 3.2. These
tables have been extracted from the Water Quality Control Plan for the San Diego
Basin. The beneficial uses are defined as follows:
• MUN -Municipal and Domestic Supply: Includes uses of water for community,
military, or individual water supply systems including, but not limited to, drinking
water supply.
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Engineering
storm Wafer Management Plan (SWMP)
Black Rqil Ridge Tentative Map
• AGR -Agricultural Supply: Includes uses of water for farming, horticulture, or
ranching including, but not limited to, irrigation, stock watering, or support of
vegetation for range grazing.
• IND -Industrial Services Supply: Includes uses of water for industrial activities that
do not depend primarily on water quality including, but not limited to, mining,
cooling water supply, hydraulic conveyance, gravel washing, fire protection, or oil
well re-pressurization.
• BIOL -Preservation of Biological Habitats of Special Significance: Includes uses of
water that support designated areas or habitats.
• ~ST -Estuarine Habitat: Includes uses of water that support estuarine ecosystems,
including but not limited to preservation or enhancement of estuarine habitats,
vegetation, fish, shellfish, or wildlife.
• MAR -Marine Habitat: Includes uses of water that support marine ecosystems,
including but not limited to preservation or enhancement of marine hdbitats,
vegetation, fish, shellfish, or wildlife.
• MIGR -Migration of Aquatic Organisms: Includes uses of water that support habitats
necessary for migration, acclimatization between fresh and salt water, or other
temporary activities by aquatic organisms, such as anadramous fish.
• RARE -Rare, threatened or endangered species: Includes uses of water necessory, .
alleast in part, for the survival and successful maintenance of plant or animal
species established under State or Federal Law as rare, threatened or endangered.
• RECl -Contact Recreation: Includes uses of water for recreational activities
involving body contact with water, where ingestion of water is reasonably possible.
These uses include, but are not limited to, swimming, wading, water-skiing, skin and
SCUBA diving, surfing, white water activities, fishing, or use of natural hot springs.
• REC2 -Non-Contact Recreation: Includes the uses of water for recreational
involving proximity to water, but not normally involving body contact with water,
where ingestion of water is reasonably possible. These uses include, but are not
limited to, picnicking, sunbathing, hiking, camping, boating, tide pool and marine
life study, hunting, sightseeing, or aesthetic enjoyment in conjunction with the
above activities.
• SPWN -Spawning, reproduction or early development: Includes uses of water that
support high quality aquatic habitats suitable for reproduction and early
development of fish.
• WILD -Wildlife Habitat: Includes uses of water that support terrestrial ecosystems
including, but not limited to, preservation and enhancement of terrestrial habitats,
vegetation, wildlife, (e.g., mammals, birds, reptiles, amphibians, invertebrates), or
wildlife water and food sources.
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storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
Engineering
3.01.1 Inland Sunace Waters
Inland Surface waters have the following beneficial uses as shown on Table 3.1.
Table 3.1-Beneficial Uses for Inland Surface Waters
Hydrologic Unit
0=: w -C"4 Z Z 0=: -' 0=: C> 0=: U u 3: c
:::) t') c 0 t-< ;...I
~ z -en ~ ~ < w W Q... 3: < -ca w 0=: 0=: 0=: en
904.51 • • • • • • • • •
• Existing Beneficial Use
3.01.2 Groundwater
Groundwater beneficial uses includes areas shown in Table 3.2.
Table 3.2 -Beneficial Uses for Groundwater
Hydrologic Unit
0=: w -C"4 Z C Z 0=: ...I 0=: t') 0=: U u 3: :::) C> c 0 t-< ...I
~ < Z en ~ ~ < w w c.. 3: -CIQ W 0=: 0=: 0=: en
904.51 • • •
• Existing Beneficial Use
Section 3.02 303( d) Status
According to the California 2002303(d) list published by the San Diego Regional Water
Quality Control Board, the water bodies that are associated with this project are not
impaired.
Section 4.
Characterization of Project Runoff
Section 4.01 Existing and Post Construction Drainage
The proposed project will not significantly alter drainage pdttemson the site or the
surrounding area. The Storm water discharge points will not divert runoff from existing
conditions.
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Engineering
stann Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
While there will be a substantial increase to the amount of impervious area, a large
part of the increase is accounted for by the widening of Black Rail Road. Poins?t.tia
Lane and the construction of Streets "A" and "B". Black RailRoad will be increased in
width by about 4 feet and curb gutter and sidewalk will be installed. Poinsettia Lane
will be increased in width by about 14 feet and curb gutter and sidewalk will be
installed. Street "A", which is currently an unimproved dirt road, will be 32 feet in width
of AC pavement, curb, gutter and sidewalk. Street "B" will be fully improved to 36 feet
of pavement with curb, gutter and sidewalk. This increase in pervious area will be
offset by the inclusion of vegetated swales along the north side of the property which
will slow the runoff and increase the time of concentration for the site.
Approximately 0.80 acres of open ground will be covered by the single-family
residences and appurtenant driveways and an additional 1.1 acres of open' ground
will be paved for the above mentioned street improvements. Thus, the impervious
area on the site will increase from 0 acres to 1.9 acres.
This change in land use will increase the composite runoff coefficient, of the project,
from C=OAO to C=0.55. Also, the total peak flow rate will increase from 3.8 cfs under
the existing condition to 3.9 cfs under the proposed condition. A detoiled description
of the drainage pattems and flows are discussed in the Drainage Report submitted to
the City of Carlsbad. A copy of this report is included in Attachment C to this report.
See Table 4.1 and Attachment D for Impervious area calculations.
Table 4.1 -Impervious Areas & Runoff Coefficients
Construction site area 3.6 aGres
Percentage impervious area before construction 0 % ..
Runoff coefficient before construction (1) DAD
Percentage impervious area after construction 52 %
Runoff coefficient after construction (1) 0.55
Anticipated off-site storm water flow on to the 0 cfs construction site
(1) Calculations are shown in Attachment C
The runoff from this site both in the existing state and the proposed development is
directed to two distinct outflows. Most of the current runoff discharges via sheet flow
across the property to the West, which, like this site, is currently rural residential «0.5
Units/Acre). The existing semi-natural environment serv~s as a bio-filter for the runoff
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storm Wafer Management Pian (SWMP)
Black Rail Ridge Tentative Map
Engineering
generated from the area. A similar quantity of post-construction runoff will be directed
through an on-site vegetated swale prior to discharging into this same area.
The remainder of the runoff, predominantly originating on the pavement on Street "A" ,
and Black Rail Road, will be directed via curb and gutter westerly on Street "A".
At the time when the property to the West of the proposed knuckle on Street "A" is
developed, a storm drain system with a filter system should be installed. As this would
be on private property not owned by the City or this developer, it is impractical at this
time.
Refer to the Site Map in Attachment B for post construction BMP locations.
Summaries of the post-construction water quality flows are included in Table 4.2. The
flows were developed using the 85th Percentile Precipitation map developed by the
County, which was obtained from the website http://www.co.san-
diego.ca .us/dpw /Iand/flood.htm
Table 4.2 -Post Construction Water Quality Flows
Outfall Tributary Area
Ql0 QWQ (Acres)
A (Street A) 1.0 1.2 0.1
B (W'ly PL) 2.7 2.1 0.2
(lJ Calculations are shown in Attachment D
Section 4.02 Post-Construction Expected Discharges
There are no sampling data available for the existing site condition. In addition, the
project is not expected to generate significant amounts of non-visible pollutants.
However, the following constituents are commonly found on similar developments and
could affect water quality:
• Sediment discharge due to construction activities and post-construction areas left
bare.
• Nutrients from fertilizers
• Trash and debris deposited in drain inlets.
• Hydrocarbons from paved areas.
• Pesticides from landscaping and home use.
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storm water ManagemenfPlan (SWMP)
Black Rail Ridge Tentative Map
Engineering
Section 4.03 3.3 Soil Characteristics
The project area consists of soil group C with a minimum saturated ihfiltration rate of
6.3 mm/h. The project will not have slopes steeper than 2: 1. All slopes will include slope
protection for construction and post-construction.
(Note: Information regarding soil conditions is also available in the Soil Survey~San
Diego Area, California, US Department of Agriculture, 1973.)
Section 5.
Mitigation Measures To Protect Water Quality
To address water quality for the project, BMPs will be implemented during construction
and post-construction.
Section 5.01 Construction BMPs
A detailed description of the construction BMPs is included in the SWPPP and-the
Grading Plans for this project. A summary of the included BMPs is as follows:
• SS-l, Scheduling
• SS-3, Hydraulic Mulching
• SS-4, Hydroseeding
• SS-9, Earth Dikes/Drainage Swales & Lined Ditches
• SS-10, Outlet Protection/ Velocity Dissipation Devices
• SC-1, Silt Fence
• SC-4, Check Dams
• SC-5, Fiber Rolls
• SC-7, Street Sweeping and Vacuuming
• SC-7, Street Sweeping and Vacuuming
• TC-l , Stabilized Construction Entrance
• TC-3, Entrance/Outlet Tire Wash
• WE-1, Wind Erosion Control
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storm water Management Pian (SWMP)
Black Rail Ridge Tentative Map
Engineering
• NS-l, Water Conservation Practices
• NS-2, Dewatering Operations
• NS-3, Paving and Grinding Operations
• NS-6, Illicit Connection/Illegal Dischdrge Detection and Reporting
• NS-7, Potable Water/Irrigation
• WM-l, Material Delivery and Storage
• WM-2, Material Use
• WM-4, Spill Prevention and Control
Section 5.02 Post-construction BMPs
Pollutants of concern as noted in Section 4 will be addressed through three types of
BMPs. These types of BMPs are site design, source control and treatment control.
5.02.1 Site Design BMPs
The project is designed to minimize the use of impervious areas. Streets and building
pad areas have been designed to meet the minimum City Standard widths~ All slopes
will be landscaped and irrigated. The landscaping will consist of both native and non-
native plants. The goal is to achieve plant establishment expeditiously to reduce
erosion. The irrigation system for these landscaped areas will be monitored to reduce
over irrigation. Also, riprap will be placed at lined ditch outfalls to reduce veloCities.
5.02.2 Source Control BMPs
Source control BMPs will consist of measures to prevent polluted runoff. This program
will include an educational component directed at each homeowner. The
homeowners will receive a set of brochures developed by the County's Environmental
Health Department. These will include the following:
• Storm water Runoff Pollution Fact Sheet.
• storm water Runoff Pollution Prevention Tips for Homeowners.
• Storm water Pollution Prevention Yard Work (Landscaping, Gordening, Pest
Control).
• Storm water Pollution Prevention Pet Waste.
• Storm water BMP Swimming Pool and Spa Cleaning.
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Engineering
5.02.3 Treatment Control BMPs
storm Wafer Management Pian (SWMP)
Black Rail Ridge Tentative Map
The following treatment control BMPs will be implemented to address water quality:
• Bic-Filters
• Gravel Check Dams
Placements of the BMPs are noted on the Project Site Plan (Attachment B).
5.02.3(i) Bio-Filters
Bic-filtration swales are vegetated channels that receive directed flow and convey
storm water. A schematic illustration of bic-filter is shown in Figure 5.1.
Pollutants are removed by filtration through the grass, sedimentation, adsorption to soil
particles, and infiltration through the soil. Swales are mainly effective at removing
debris and solid particles, although some dissolved constituents are removed by
adsorption onto the soil.
5.02.3 (i)(a) Appropriate Applications and Siting Constraints:
Swales and strips should be considered wherever site conditions and climate allow
vegetation to be established and where flow velocities are not high enough to cause
scour. Even where strips cannot be sited to accept directed sheet flow, ve~etated
areas provide treatment of rainfall and reduce the overall impervious surface.
FACTORS AFFECTING PRELIMINARY DESIGN:
Swales have two design goals: 1) maximize treatment, 2} provide adequate hydroulic
function for flood routing, adequate drainage and scour prevention. Treatmenf is
maximized by designing the flow of water through the swale to be as shallow and long
as site constraints allow. No minimum dimensions are required for treatment purposes;
as this could exclude swales from consideration at some sites. Swales should also be
sized as a conveyance system calculated according to County procedures for flood
routing and scour.
To maximize treatment efficiency, strips should be designed to be as long {in the
direction of flow} and as flat as the site will allow. No minimum lengths or maximum
slopes are required for treatment purposes. The area to be used for the strip should be
free of gullies or rills that can concentrate overland flow and cause erosion.
Vegetation mixes appropriate for various climates and locations will be developed by
District landscape staff. Table 3.3.1 summarizes preliminary design fa~tors for bio-
filtration.
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Engineering
4:1 t1IN. SIDE SLOPE
_____ sz__ _ _____ ~ _ ____ ==__ 1-
DESIG. FLOW DEPTH
WA TER QUALITY FLow DEPTH
~-----Wmm'----~
SECTION
No SCALE
SECTION
No SCALE
storm Wafer ¥anagement Plan (SWMP)
Black Rail Ridge Tentative Map
ENGINEERED CHECK Dm (50'oc)
Figure 5-1 -Vegetated Swale
5.02.3(ii) Gravel Check Dams
A check dam is a small device constructed of rocks, gravel bags, Of fiber rolls, placed
across a natural or man make channel or drainage ditch. A schematic illustration of
rock check dam is shown in Rgure 5.2.
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Engineering
storm Water Management Plan (SWMP)
Black Rail Ridge Tentative Map
Check dams reduce scour and channel erosion by reducing flow velocity and
encouraging sediment dropout. Checkdams are mainly effective at removing debris
and sediment, although some dissolved constituents are removed by adsorption onto
COARSE AGGFlfGA TE
the soil.
SECTION A-A
NT.S.
SECTION 8-8
Mrs
Figure 5-2 Gravel Check Dam
5.02.3 (ii)(a) Appropriate Applications
Check dams may be installed in small open channels, steep channels where storm
water velocities exceed 5 fps, during establishment of grass linings in drainage ditches
ot channels, and in temporary ditches where a short length of service does not
warrant establishment of erosion resistant linings ..
FACTORS AFFECTING PRELIMINARY DESIGN:
Check Dams have two design goals: 1) maximize treatment, 2) provide adequate
hydraulic function for flood routing, adequate drainage and scour prevention.
Treatment is maximized by locating the check dams at distances and heights that
allow small pools to form behind them. Backwater from downstream check dam
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stonn Wafer Management Plan (SWMP)
Block Roil Ridge Tentativ~ Map
Engineering
should reach the toe of the upstream dam. Dams should be designed such that high
flows shall safely flow over the check dam without increase in upstream flooding or
damage to the check dam.
Section 6.
Operation and Maintenance Program
The operation and maintenance requirements for each type of BMP is as follows:
Section 6.01 Bio-Filters
The operational and maintenance needs of a Swale are:
• Vegetation management to maintain adequate hydraulic functioning and to limit
habitat for disease-carrying animals.
• Animal and vector control.
• Periodic sediment removal to optimize performance.
• Trash, debris, grass trimmings, tree pruning, and leaf collection and removal to
prevent obstruction of a Swale and monitoring equipment.
• Removal of standing water, which may contribute to the development of aquatic
plant communities or mosquito breeding areas.
• Preventive maintenance on sampling, flow measurement, and associated BMP
equipment and structures.
• Erosion and structural maintenance to prevent the loss of soil and maintain the
performance of the Swale.
6~0 1.1 Inspection Frequency
The facility will be inspected and inspection visits will be completely documented:
• Once a month at a minimum.
• After every large storm (after every storm monitored or those storms with more than
0.50 inch of precipitation.) ,
• On a weekly basis during extended periods of wet weather.
6.01.2 Aesthetic and Functional Maintenance
Aesthetic maintenance is important for public acceptance of stormwater facilities.
Functional maintenance is important for performance and ,safety reasons.
Both forms of maintenance will be combined into an overall Stormwater Management
System Maintenance.
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Engineering
6.01.2{i) Aesthetic Maintenance
storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
The following activities will be included in the aesthetic maintenance program:
• Grass Trimming. Trimming of grass will be done on the Swale, around fences,_ at the
inlet and outlet structures, and sampling structures.
• Weed Control. Weeds will be removed through mechanical means. Herbicide will
not be used because these chemicals may impact the water quality monitoring.
6.01.2(ii) Functional Maintenance
Functional maintenance has two components:
Preventive maintenance
Corrective maintenance
6.01.2 (ii)( a) Preventive Maintenance
Preventive maintenance activities to be instituted at a Swale are:
• Grass Mowing. Vegetation seed mix within the Swale is designed to be kept short to
maintain adequate hydraulic functioning and to limit the development of faunal
habitats.
• Trash and Debris. During each inspection and maintenance visit to the site, debris
and trash removal will be conducted to reduce the potential for inlet and outlet
structures and other components from becoming clogged and inoperable during
storm events.
• Sediment Removal. Sediment accumulation, as part of the operation and
maintenance program at a Swale, will be monitored once a month during, the dry
season, after every large storm (0.50 inch), and monthly during the wet season.
Specifically, if sediment reaches a level at or near plant height, or could interfere
with flow or operation, the sediment will be removed. If accumulation of debris or
sediment is determined to be the cause of decline in design performance,-prompt
action (Le., within ten working days) will be taken to restore the Swale to design
performance standards. Actions will include using additional fill and vegetation
and/or removing accumulated sediment to correct channeling or ponding.
Characterization and Appropriate disposal of sediment will comply with applicable
local, county, state, or federal requirements. The swale will be regraded, if the flow
gradient has changed, and then replanted with sod.
• Removal of Standing Water. Standing water must be removed if it contributes to
the development of aquatic plant communities or mosquito breeding areas.
• Mechanical and Electronic Components. Regularly scheduled 'maintenance will be
performed on fences, gates, locks, and sampling and monitoring equipment in
accordance with the manufacturers' recommendations. Electronic and
mechanical components will be operated during each maintenance inspection to
assure continued performance.
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Engineering
storm water Managem~nt Plan (SWMP)
Black RailRidge Tentative Map
• Fertilization and Irrigation. The vegetation seed mix has been designed so that
fertilization and irrigation is not necessary. Fertilizers and irrigation will not be used to
maintain the vegetation.
• Elimination of Mosquito Breeding Habitats. The most effective mosquito control
program is one that eliminates potential breeding habitats.
6.01.2 (ii)(b) Corrective Maintenance
Corrective maintenance is required on an emergency or non-routine basis to correct
problems and to restore the intended operation and safe function of a Swale.
Corrective maintenance activities include:
• Removal of Debris and Sediment. Sediment, debris, and trash, which impede the
hydraulic functioning of a Swale and prevent vegetative growth, will be removed
and properly disposed. Temporary arrangements will be made for handling the
sediments until a permanent arrangement is made. Vegetation will be re-
established after sediment removal.
• Structural Repairs. Once deemed necessary, repairs to structural components of a
Swale and its inlet and outlet structures will be done within 10 working days'.
Qualified individuals (Le., the designers or contractors) will conduct repairs Where,
structural damage has occurred.
• Embankment and Slope Repairs. Once deemed necessary, damage to the"
embankments and slopes of Swales will be repaired within lO'working days).
• Erosion Repair. Where a reseeding program has been ineffective, or where other
factors have created erosive conditions (Le., pedestrian traffic, concentrated flow,
etc.), corrective steps will be taken to prevent loss of soil and any subsequent
danger to the performance of a Swale. There are a number of corrective actions
than can be taken. These include erosion control blankets, rip-rap, sodding, or
reduced flow through the area. Designers or contractors will be consulted to
address erosion problems if the solution is not evident.
• Fence Repair. Repair of fences will be done within 30 days to maintain the security
of the site.
• Elimination of Animal Burrows. Animal burrows will be filled and steps taken to
remove the animals if burrowing problems continue to occur (filling and
compacting). If the problem persists, vector control specialists will be consulted
regarding removal steps. This consulting is necessary as the threat Of rabies in some
areas may necessitate the animals being destroyed rather than relocated. If the-
BMP performance is affected, abatement will begin. Otherwise, abatement will be
performed annually in September.
• General Facility Maintenance. In addition to the above elements of corrective
maintenance, general corrective maintenance will address the overall facility and
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storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
Engineering
its associated components. If corrective maintenance is being done to one
component, other components will be inspected to see if maintenance is needed.
6.01.3 Maintenance Frequency
The maintenance indicator document, included as Appendix B, lists the schedule of
maintenance activities to be implemented at a Swale.
• After every large storm (after every storm monitored or those storms with more than
0.50 inch of precipitation).
• On a weekly basis during extended periods of wet weather.
• On a monthly basis during the non-rainy season or periods of dry weather.
6.01.4 Debris and Sediment Disposal
Waste generated at Swales is ultimately the responsibility of Mr. Lynn until such time as
the parcel is sold, then the new property owner will assume responsibility. Disposal of
sediment, debris, and trash will comply with applicable local, county, state, and
federal waste control programs.
Section 6.02 Gravel Chack Dams
The operational and maintenance needs of an Gravel Check Dam are:
• Periodic sediment removal in accordance with the 1/3 depth threshold.
• Monitoring of the check dams to ensure it is completely and properly drained.
• Vegetation management to prevent marsh vegetation from taking hold, and to
limit habitat for disease-carrying fauna.
• Removal of grass trimmings, weeds, tree pruning, leaves, litter, and debris.
• Vegetative stabilization of eroding banks areas.
6.02.1 Inspection Frequency
The facility will be inspected and inspection visits will be completely documented:
• Once a month at a minimum. .
• After every large storm (after every storm monitored or those storms with more than
0.50 inch of precipitation).
• On a weekly basis during extended periods of wet weather.
6.02.2 Aesthetic and Functional Maintenance
August 28, 2003 Page 17
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Engineering
Storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
Functianal maintenance is impartant far perfarmance and safety reasons. Aesthetic
maintenance is impartant far public acceptance af starm water focilities.
6.02.2(i) Aesthetic Maintenance
The fallawing activities will be included in the aesthetic maintenance program:
• . Grass Trimming. Trimming af grass will be dane araund fences! the basin, autlet
structures, and sampling structures.
• Weed Cantral. Weeds will be remaved through mechanical means.
6.02.2(ii) Functional Maintenance
Functional maintenance has two components:
• Preventive maintenance.
• Corrective maintenance.
6.02.2 (ii){a) Preventive Maintenance
Preventive maintenance that will be done on a regular basis.
• Trash and Debris. During each inspection and maintenance visit to the site, debris
and trash removal will be conducted to reduce the potential for inlet and autlet
structures and other companents fram becaming clagged and inaperdble during
starm events.
• Sediment Management. Alluvial depasits at the check dams may create zanes af
ponded water. Upan these occurrences these depasits will be graded within the
channel in an effart to. maintain the functianality of the BMP. Sediment grading will
be accomplished by manually raking the depasits.
• Sediment Remaval. Surface sediments will be removed when sediment
accumulatian is greater than 1/3 the height of the check darn. Veg~tatian
removed with any surface sediment excavatian activities will be replaced thraugh
reseeding. Dispasal of sediments will comply. with applicable local, county, state, or
federal requirements.
• Elimination of Mosquito Breeding Habitats. The most effective mosquito
contro.l program is ane that eliminates potential breeding habitats.
6.02.2 (ii)(b) Corrective Maintenance
Carrective maintenance is required on an emergency or non-ro.utine basis to carrect
problems and to restore the int~nded operatian and safe functian af an the check
dams. Corrective maintenance activities include:
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storm water Management Plan (SWMP)
Black Rail Ridge Tentative Map
Engineering
• Removal of Debris and Sediment. Sediment debris, and trash, which threaten the
ability to convey water, will be removed immediately and properly disposed of.
• Embankment and Slope Repairs. Damage to the embankments and slopes will be
repaired quickly (e.g., within 10 working days).
• Erosion Repair. Where a reseeding program has been ineffective, or where other
factors have created erosive conditions (Le., pedestrian traffic, concentrqtedflow,
etc.), corrective steps will be taken to prevent loss of soil and any subsequent
danger to the performance of the check dams. There are a number of corrective
actions than can be taken. These include erosion control blankets, rip-rap, sodding,
or reduced flow through the area. Design engineers will be consulted to address
erosion problems if the solution is not evident.
• Elimination of Animal Burrows. Animal burrows will be filled and steps taken to
remove the animals if burrowing problems continue to occur (filling and .
compacting). If the problem persists, vector control specialists will be consulted
regarding removal steps. This consulting is necessary as the threat of rabies in some
areas may necessitate the animals being destroyed rather than relocated.
6.02.3 General Facility Maintenance.
In addition to the above elements of corrective maintenance, general corrective
maintenance will address the overall faciiity and its associated components. If
corrective maintenance is being done to one component other components will be
inspected to see if maintenance is needed.
6.02.4 Maintenance Frequency
The maintenance schedule for the checkdams should be as follows:
• After every large storm (after every storm monitored or those storms with more than
0.50 inch of precipitation).
• On a weekly basis during extended periods of wet weather.
6.02.5 Debris and Sediment Disposal
Mr. Lynn is responsible for disposal of sediment debris, and trash in accordance with
local, county, state, and federal waste control programs.
Section 7.
Mechanisms to Assure Maintenance
This section is intended to provide information regarding the ability of the
owner/developer to ensure the construction and maintenance of post-construction
BMPs.
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Engineering
storm Wafer Mana~ement Pktn (SWMP)
Black Rail Ridge Tentative Map,
Section 7.01 Stormwater Ordinance Requirement:
The County of San Diego Watershed Protection, Storm water Management, and
Discharge Control Ordinance (S.O.) requires this ongoing maintenance. In the event
that the mechanisms below prove ineffective, or in addition to enforcing those
mechanisms, civil action, criminal action or administrative citation could also be
pursued for violations of the ordinance.
Section 7.02 Public Nuisance Abatement:
Under the S.O. failure to maintain a BMP would constitute a public nuisance, which
may be abated under the Uniform Public Nuisance Abatement Procedure. This
provides an enforcement mechanism additional to the above, and would allow costs
of maintenance to be billed to the owner, a lien placed on the property, and the tax
collection process to be used.
Section 7.03 Notice to Purchasers.
Section 67.B19(e) of the SO requires developers to-provide clear written notification to
persons acquiring land upon which a BMP is located, or others 9ssuming a BMP
maintenance obligation, of the maintenance duty.
Section 7.04 Subdivision Public Report
Tentative Map and Tentative Parcel Map approvals will be conditioned to require
that, prior to approval of a Final or Parcel Map, the subdivider shall provide evidence
to the Director of Public Works, that the subdivider has requested the Colifornia
Department of Real Estate'to include in the public report to be issued for the sales of
lots within the subdivision, a notification regarding the maintenance requirement. (The
requirement for this condition would not be applicable to subdivisions which are
exempt from regulation under the Subdivided Lands Act, or for which no public report
will be issued.)
Section 7.05 Funding:
None Required.
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Engineering
Section 8.
Summary Conclusions
storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
This SWMP has been prepared in accordance with the Watershed Protection, storm
water Management, and Discharge Control Ordinance and the Storm water
Standards Manual. This SWMP has evaluated and addressed the potential pollutants
associated with this project and their effects on water quality. A summary of the facts
and findings associated with this project and the measures addressed by this SWMP is
as follows:
• The beneficial uses for the receiving waters have been identified. None of these
beneficial uses will be impaired or diminish due to the construction and operation
of this project. .
• The Lynn Minor Subdivision project will not significantly alter drainage pattemson
the site. The discharge points will not be changed and gravel check ddms will be
placed to attenuate the flow velocities. Thus preventing downstream erosion.
• Open areas and slopes will be landscaped to reduce or eliminate sediment
discharge.
• The vegetated swales proposed as part of the project will provide some mitigation
of the increased peak flows by detaining flows, reducing the velocities, and
providing opportunities for infiltration. _
• The proposed construction and post-construction BMPs address mitigation
measures to protect water quality and protection of water quality objectives and
beneficial uses to the maximum extent practicable.
August 28, 2003 Page 21
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~ngineering
Section 9.
Certification
storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
This Storm Water Management Plan has been prepared under the direction of the
following Registered Civil Engineer. The Registered Civil Engineer attests to the
technical information contained herein and the engineering data upon which'
recommendations, conclusions, and decisions are based.
Michael L. Benesh, RCE 37893
Exp,. 3/31/05
August 28. 2003
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Date
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Engineering
storm Wafer Management Plan (SWMP)
Black Rail Ridge Tentative Map
AHachment A -Vicinity Map
1 Black Rail Ridge Subdivision I·
Portion of U.S.G~S Encinitas Quadrangle
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)I~JIJ storm Wafer Management Plan (SWMP)
1 Black Rail Ridge Tentative Map
Engineering
I Attachment B -Site Plan
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POOR
QUALITY
ORIGINAL S
....... ;
.SCAl.E: 1'=100'
I" "';:::~':I':'; ~~~~~":<':' :';' ::::~~:F~==:::;;~SITE; f'ERII1E~~/ER;'"~
1:;_ V::_I~ "";'i:,: • _ ,;;:'/-POINsETTIA LANE
'.~~~1~~:)~!
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storm Wafer Pollution Prevention Plan. (SWPPP)
Black Rail Ridge Tentative Map
Engineering
Attachment C -Computation Sheet for Runoff Coefficients
Total Site Area 3.6 Acres .............................................................................•....•......... (A)
Existing Site Conditions
Impervious Area 1 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••.•••••••••••••••••. 0· Acres
(B)
Impervious Area Runoff Coefficient2 ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 0.95
(C)
Pervious Area3 3.7 Acres ................................................................................•........... (D)
Pervious Area Runoff Coefficient4 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 0.40
(E)
Combined Runoff Coefficient ................................................................................. 0.40
[(BxC)+(DxE)]/ A
'.proposed Site Conditions
.. 1 . 0 Impervious Area ............................................................................................... 1 .. Acres
Notes:
(F)
Impervious Area Runoff Coefficient2 ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• ~ ••• 0.95
(G)
Pervious Area3 2.6 Acres ..................................................................................•......... (H)
Pervious Area Runoff Coefficient4 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 0.40
(I)
Combined Runoff Coefficient ................................................................................. 0.55
[(FxG)+(Hxl)]/ A
1. Includes paved areas, areas covered by buildings and other impervious areas.
2. 95% assumed.
3. Includes areas of vegetation, unpaved soil areas, and other pervious areas. '
4. Runoff Coefficient for rural areas per Appendix IX, Soil Type C, San Diego Hydrology
Manual.
August 28, 2003 PagE:) C-1
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Affachment D -Drainage. Study
storm Wafer Pollution Prevention Plan (SWPPP)
Black Rail Ridge Tentative Map
Refer to Drainage Study for Black Rail Ridge Subdivision, CT 03-_ prepared by MLB
Engineering, Dated August 28, 2003.
August 28, 2003 Page D-1
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