HomeMy WebLinkAboutCT 04-01; Yamamoto Subdivision; Storm Water Manage Plan; 2005-06-13ENGINEERING
Professional Civil Engineer and Land Sitrveyo
STORM WATER MANAGEMENT PLAN
for
Yamamoto Property, CT 04-01
Prepared for:
McCulloogh-Ames Development
11828 Rancho Bernardo Road, Suite 205
San Diego, CA 92128
858 675-6400
Profecf Site Address
S.E. Corner, Black Rail Road & Songbird Avenue, Carisbad, CA 92009
Prepared by:
Michael L. Benesh, R.C.E. 37893
Dafe:
June 13, 2005
600 S. ANDREASEN DRIVE • SUITE E • ESCONDIDO. CA 92029
'HONE: 760 741 -3577 • FAX 760 897-21 65 • E-MAIL: MLBENESH@PACBELL.NET
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Engineering
Sform Wcrfer Management Pton (SWMPj
yamamoto Property, CT04-0J
Contents
,1 Section 1. Introduction
Section 1.01 Introduction 1
Section 2. Project ^
Section 2.01 Description 2
Section 2.02 Topograplny and Land Use 2
Section 2.03 Hydrologic Unit Contributions..... 3
Section 3. Water Quality Environment 3
Section 3.01 Beneficial Uses 3
3.01.1 Inland Surface Waters ^
3.01.2 Groundwater 5
Section 3.02 303(d) Status 5
Section 4. Characterization of Project Runoff 5
Section 4.01 Existing and Post Construction Drainage ...5
Section 4.02 Post-Construction Expected Disctiarges 7
Section 4.03 3.3 Soil Characteristics 8
Section 5. Mitigation Measures To Protect Water Quality 8
Section 5.01 Construction BMPs 8
Section 5.02 Post-construction BMPs 9
6.02.1 Site Design BMPs 9
5.02.2 Source Control BMPs 9
5.02.3 Treatment Control BMPs 10
5.02.3(i) Vegetated (Bio-Filtration) Swales 10
5.02.3 (i) (a) Appropriate Applications and Siting Constraints: 12
5.02.3(ii) Infiltration Trench 12
5.02.3 (ii) (a) Appropriate Applications 13
Section 6. Operation and Maintenance Program......^. 14
Section 6.01 Vegetated Swales 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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6.01.2 (ii)(b) Corrective Maintenance 16
6.01.3 Maintenance Frequency 17
6.01.4 Debris and Sediment Disposal 17
Section 6.02 Infiltration Trench 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 Maintenance Frequency 19
6.02.4 Debris and Sediment Disposal 19
Section 7. Mechanisms to Assure Maintenance 19
Section 7.01 Stormwater Ordinance Requirement: 19
Section 7.02 20
Section 7.03 20
Section 7.04 20
Section 7.05 20
.A-1
Section 8. Summary Conclusions 20
22
Sections. Certification • "
Attachment A - Vicinity Map
Attachment B - Site Plan ^"^
Attachment C - Computation Sheet for Runoff Coefficients C-2
Attachment D - Drainage Study ^'^
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^ T? •riK- ^'^'^ tAanagement Plan (SWMP)
Vamamoto Property, CT 04-01
Engineering
Section 1.
Introduction
Section 1.01 Introduction
The purpose of this SWMP is to address the water quality impacts from the proposed
improvements on the Yamamoto Property 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 planning. The SWMP is subject to revisions as needed by the
engineer.
"The requirement to implement storm water BMP requirements for development
projects is based on Section 402 (p) of the Clean Water Act. The Federal Clean Water
Act amendments of 1987 established a framework for regulating storm water
discharges from municipal, industrial, and construction activities under the NPDES
program. Under the Federal Clean Water Act, municipalities throughout the nation are
issued a Municipal NPDES Permit. The primary goal of the Municipal Permit is to reduce
polluted discharges from entering the storm water conveyance system and local
receiving and coastal waters and to ensure the beneficial uses of protected receiving
waters. In California, the State Water Resources Control Board (SWRCB), through the
nine Regional Boards, administers the NPDES storm water municipal permitting
program. Based on the San Diego Municipal Permit issued by the San Diego Regional
Board, Cities are required to develop and implement construction and permanent
storm water BMPs addressing pollution from new private and public development
projects.
Per the National Pollution Discharge Elimination System (NPDES) permit (Order No.
2001-01 NPDES No. CASOl 08758) the City of Carisbad requires development and
significant redevelopment, that fall under the category of "priority projects", include
Best Management Practices (BMP's) be incorporated to ensure that those projects
reduce potential urban pollutant runoff to the maximum extent practicable (MEP)."
By definition, detached residential projects of more than 10 units, of which the
Yamamoto Subdivision is one, are classified as "priority projects".
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storm Water tAanagement Plan (SWMP)
Yamamoto Property, CT 04-01
Engineering
Section 2.
Project
Section 2.01 Description
The project is a 4.9 acre site located in the City of Carisbad, California.
The site is bordered by Black Rail Road to the East, Songbird Avenue and CT 00-13 to
the North, CT 99-10 to the South and CT 92-3 to the East.
The site is adjacent to single family homes on South, East and North. The site is
adjacent to agricultural land to the West.
The proposed project will subdivide the existing parcel of land into 16 lots of a
rninimum 0^7500 quare feet each. Construction will include street and utility
memenH^^^^ Black Rail Road, Songbird Avenue, Surfcrest Avenue and Street
Tas wel os on-site grading to create building pads. The amount of anticipated
grading is approximately 19,000 cubic yards.
Section 2.02 Topography and Land Use
The site is currently vacant and has been used for agricultural purposes. There are no
existing permanent structures.
Th^ surface of the land is divided by a small North to South running ridge with the
To^mng^^^^ the West and a smaller portion sloping to the East A portion
S Song^^^^^^^ has already been constructed on s.te -
pavernent, curb and gutter and a slope cut along the northerly edge of the site.
Storm water runoff westeriy of the natural ridge currently drains across the site to Black
Rc^^ Road via sheet flow and concentrated flows in Songbird Avenue. From there, it
contS sS^jtS abng Black Rail Road to a storm drain inlet 400 f^et ^^^^^^^'^ f..
'he L h^s ofm dr^^^^ outlets to a natural drainage area so~^rly of the
interVection of Black Rail Road and Aviara Parkway, approximately 1500 feet
southwesteriy of the project site.
Th^ storm water runoff easteriy of the natural ridge currently drains via sheet flow to an
ex Wu"'^di"ch^^^ the easterly property line, then northerly along the ditch to
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Songbird Avenue. Once in Songbird Avenue, runoff continues northerly and easterly,
along Cabella Place, and Docena Road to a storm drain system in the Aviara
development. This storm drain system outlets to a natural drainage area
approximately 1500 feet easteriy of the project site.
Through a series of storm drain culverts and natural drainage areas the storm water
runoff from this site eventually reaches the Batiquitos Lagoon and the Pacific Ocean.
After development, the existing drainage pattern will remain essentially the same for
the site with a small increase in the area draining to the east.
Section 2.03 Hydrologic Unit Contributions
The project is located in the Batiquitos watershed and in the Carisbad hydrologic unit
(904.51). The project drains via surface flow to the east and west, and eventually,
through a series of storm drain culverts and natural drainage areas, the storm water
runoff from this site reaches the Batiquitos Lagoon 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.
• 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.
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• BIOL - Preservation of Biological Habitats of Special Significance: Includes uses of
water that support designated areas or habitats.
• EST - 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 presen/ation or enhancement of marine habitats,
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 anadromous fish.
• RARE - Rare, threatened or endangered species: Includes uses of water necessary,
al least in part, for the sun/ival 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.
3.0 ?. J Inland Surface Waters
Inland Surface waters have the following beneficial uses as shown on Table 3.1.
Table 3.1 - Beneficial Uses for inland Surface Waters
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Hydrologic Unit MUN AGR o z BIOL «/>
LU MAR MIGR RARE REC 1 REC 2 SPWN WILD 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 MUN oc O
<
a z
_j
O
ea
t—
LU MAR MIGR RARE REC 1 REC 2 SPWN WILD 904.51 • m •
• Existing Beneficial Use
Section 3.02 303(d) Status
According to the California 2002 303(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 patterns on the site or the
surrounding area. The Storm water discharge points will not significantly divert runoff
from existing conditions.
While there will be a substantial increase to the amount of impervious area, a large
port of the increase is accounted for by the widening of Black Rail Road, Songbird
Avenue and the construction of Surfcrest Avenue through the site and Street "A".
Black Rail Road will be increased in width by about 4 feet and curb gutter and
sidewalk will be installed. Songbird Avenue will is already paved to full width, but a
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Yamamoto Property, CT 04-01
sidewalk will be added on the side adjoining the project. Surfcrest Avenue, which
currently dead ends into the site, will be extended through the site to Songbird Avenue
and be paved with 36 feet of AC pavement, curb gutters and sidewalk. Street "A" will
be fully improved to 36 feet of pavement with curb, gutter and sidewalk.
Approximately 1.5 acres of open ground will be covered by the single-family
residences and appurtenant driveways and an additional 0.7 acres of open ground
will be paved for the above mentioned street improvements. Thus, the impervious
area on the site will increase from 0.3 acres to 2.5 acres.
This change in land use will increase the composite runoff coefficient, of the project,
from C=0.45 to C=0.55. Also, the total peak 10 year storm flow rate will increase from
4.3 cfs under the existing condition to 5.7 cfs under the proposed condition. A
detailed description of the drainage patterns and flows are discussed in the Drainage
Report submitted to the City of Carisbad. 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 - Imoervious Areas & Runoff Coefficients
Construction site area 4.9 acres
Percentage impervious area before construction 6 %
Runoff coefficient before construction n) 0.45
Percentage impervious area after construction 41 %
Runoff coefficient after construction o 0.65
Anticipated off-site storm water flow on to the
construction site 0 cfs
(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. Both outflows lead to natural drainage areas via
paved streets and storm drain systems. The existing natural environment sen/es as a
bio-filter for the runoff generated from the area.
Each residential lot will incorporate the following post construction BMP's to reduce
and treat the amount of storm runoff leaving the site:
1. Vegetated Swales will be incorporated in to the yard drainage system for each
lot, treating the roof and yard runoff before it leaves each lot.
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2. Small infiltration basins will be incorporated into each lots drainage system to
increase infiltration and reduce storm water runoff.
3. Pervious interiocking paving blocks shall be utilized in the driveways to each lot
to reduce the impervious area created by the subdivision and increase
infiltration.
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 mop developed by the
County, which was obtained from the website http://wvw.co.san-
diego.ca.us/dpw/land/flood.htm
Table 4.2 - Post Construction Water Quality Flows
Outfall Tributary Area
(Acres) Qio QwQ
A (East) 2.2 2.7 0.9
B (West) 2.6 3.0 1.0
(1) Calculations are shown in Attachment D
Section 4.02 Post-Construction Expected Discharges
jhere 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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Section 4.03 3.3 Soil Characteristics
The project area consists of soil group D with a minimum saturated infiltration 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: Informafion regarding so/7 conditions is also available in fhe 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 summaiy of the included BMPs is as follows:
• SS-1, 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-1, Stabilized Construction Entrance
• TC-3, Entrance/Outlet Tire Wash
• WE-1, Wind Erosion Control
• NS-1, Water Conservation Practices
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• NS-2, Dewatering Operations
• NS-3, Paving and Grinding Operations
• NS-6, Illicit Connection/Illegal Discharge Detection and Reporting
• NS-7, Potable Water/Irrigation
• WM-1, 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
pod areas have been designed to meet the minimum City Standard widths and
driveways will be constructed of pervious interiocking concrete pvaers. Streets, where
allowed by the City, will be designed using the livable streets guidelines. All slopes will
be landscaped and protected from storm runoff by directing flows away from the tops
of slopes. 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.
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, Gardening, Pest
Control).
• Storm water Pollution Prevention Pet Waste.
• Storm water BMP Swimming Pool and Spa Cleaning.
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5.02.3 Treatment Control BMPs
The following treatment control BMPs will be implemented to address water quality:
• Vegetated swales
• infiltration Basins
Placements of the BMPs are noted on the Project Site Plan (Attachment B).
5.02.3(i) Vegetated (Bio-Filtration) Swales
Vegetated swales are plant lined channels that receive directed flow and convey
storm water. A schematic illustration of vegetated swale is shown in Figure 5.1.
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Storm Water Management Pton fSWMPJ
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MiiM. SIDE SLOPE
/ r 6" FREEBOARD
\7
DESIGN ^£.01'/ DEPTH-
WATER QUALITY FLOW DEPTH-^
.
SECTION
No SCALE
rENGINEERED CHECK DAM (50'OC)
/
6" TOPSOIL OVER NATIVE-^
SECTION
No SCALE
Figure 5-1 - Vegetated Swale
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.
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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, vegetated
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 hydraulic
function for flood routing, adequate drainage and scour prevention. Treatment 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 overiand flow and cause erosion.
Vegetation mixes appropriate for various climates and locations will be developed by
District landscape staff. Table 3.3.1 summarizes preliminar/ design factors for bio-
filtration.
5.02.3(il) Infiltration Trench
An infiltration trench is an excavated trench, usually 3 to 12 feet deep, backfilled with
a stone aggregate, and lined with filter fabric. A small portion of the runoff, usually the
first flush, is diverted to the infiltration trench, which is located either underground or at
grade. Pollutants are filtered out of the runoff as it infiltrates the surrounding soils.
Infiltration trenches also provide groundwater recharge and preserve base flow in
nearby streams.
A schematic illustration of an infiltration trench is shown in Figure 5.2.
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REMOVABVLE
WELL CAP
GEOTEXTILE
FILTER FABRIC
UNDISTURBED SOIL
MINIMUM INFILTRATION RATE
OF 0.50 INCH PER HOUR
9 INCH SQUARE STEEL FOOT PLATE
4 FT DEEP TRENCH
FILLED WITH 1-3 INCH
CLEAN STONE
6 INCH
DIAMETER
PVC PIPE
1/2 INCH DIAMETER REBAR ANCHOR
Figure 5-2 Infiltration Trench
5.02.3 (ii)(a) Appropriate Applications
Infiltration trenches are often used in place of other Best Management Practices
where limited land is available. Infiltration trenches are most widely used in warmer,
less arid regions of the U.S.
Runoff that contains high levels of sediments or hydrocarbons (oil and grease) that
may clog the trench ore often pretreated with other BMPs. Examples of some
pretreatment BMPs include grit chambers, water quality inlets, sediment traps,
swales, and vegetated filter strips.
FACTORS AFFECTING PRELIMINARY DESIGN:
Feasible sites should have a minimum of 4 feet to bedrock in order to reduce
excavation costs. There should also be at least 4 feet below the trench to the water
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table to prevent potential ground water problems. Trenches should also be located at
least 100 feet upgradient from water supply wells and as far as practical from building
foundations. Land availability, the depth to bedrock, and the depth to the water table
will determine whether the infiltration trench is located underground or at grade.
Underground trenches receive runoff through pipes or channels, whereas surface
trenches collect sheet flow from the drainage area.
Section 6.
Operation and Maintenance Program
The operation and maintenance requirements for each type of BMP is as follows:
Section 6.01 Vegetated Swales
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.
6.0L1 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 d uring extended periods of wet weather.
6.0 T .2 Aesttietic and Functional Maintenance
Aesthetic maintenance is important for public acceptance of stormwater facilities.
Functional maintenance is important for performance and safety reasons^
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Both forms of maintenance will be combined into an overall Stormwater Management
System Maintenance.
6.01.2(1) Aesthetic Maintenance
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:
1. Preventive maintenance
2. Corrective maintenance
6.01.2 {li)(a) Preventive Maintenance
Preventive maintenance activities to be instituted at a Swale are:
• Gross Mowing. Vegetation seed mix within the Swale is designed to be kept short to
maintain adequate hydraulic functioning and to limit the development of founol
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 interi'ere
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 (i.e., 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
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mechanical components will be operated during each maintenance inspection to
assure continued performance.
. 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 (li)(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 wili be made for handling the
sediments until a permanent arrangement is mode. 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 (i.e., 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 10 working days).
. Erosion Repair. Where a reseeding program has been ineffective, or where other
factors have created erosive conditions (i.e., pedestrian traffic, concentrated flow,
etc.), corrective steps will be taken to prevent loss of soil and any subsequent
danger to the peri'ormance 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.
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. General Facility Maintenance. In addition to the above elements of corrective
maintenance, general corrective maintenance will address the overall facility and
its associated components. If corrective maintenance is being done to one
component, other components will be inspected to see if maintenance is needed.
6.01.3 Ma/ntenance 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.
6.0 7.4 Debris ond Sediment Disposal
Waste generated at Swales is ultimately the responsibility of the property owner.
Disposal of sediment, debris, and trash will comply with applicable local, county, state,
and federal waste control programs.
Section 6.02 Infiltration Trench
The operational and maintenance needs of an infiltration Trench are:
. Animal and vector control.
. Periodic sediment removal to optimize performance.
. Trash and debris collection and removal to prevent obstruction of a infiltration
trench and monitoring equipment.
. Removal of standing water, which may contribute to the development of aquatic
plant communities or mosquito breeding areas.
6.02.7 Inspecfton Frequency
The facility will be inspected and inspection visits will be completely documented:
. Once every three months 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 Aesttietic and Functional Maintenance
Aesthetic maintenance is important for public acceptance of stormwater facilities.
Functional maintenance is important for peri^ormance and safety reasons.
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Both forms of maintenance will be combined into on overall Stormwater Management
System Maintenance.
6.02.2(i) Aesthetic Maintenance
The foiiowing activities will be included in the aesthetic maintenance program:
• Weed Control. Weeds will be removed through mechanical means. Herbicide will
not be used because these chemicals may impact the water quality monitoring.
6.02.2(ii) Functional Maintenance
Functional maintenance has two components:
1. Preventive maintenance
2. Corrective maintenance
6.02.2 (ii)(a) Preventive Maintenance
Preventive maintenance activities to be instituted at an infiltration trench are:
. 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, will be monitored once every three months during the dry
season, after every large storm (0.50 inch), and monthly during the wet season.
Specifically, if accumulation of debris or sediment is determined to be the cause of
decline in design performance, prompt action (i.e., within ten working days) will be
taken to restore the Infiltration Trench to design performance standards. Actions will
include removing accumulated sediment and replacement of filter fabric and
upper layer of clean gravel. Characterization and Appropriate disposal of sediment
will comply with applicable local, county, state, or federal requirements.
. Removal of Standing Water. Standing water is an indication of an excess build up
of sediment in the gravel and filter cloth.
. Elimination of Mosquito Breeding Habitats. The most effective mosquito control
program is one that eliminates potential breeding habitats.
6.02.2 (ii)(b) Con-ective Maintenance
Corrective maintenance is required on on emergency or non-routine basis to correct
problems and to restore the intended operation and safe function of an Infiltration
Trench. Corrective maintenance activities include:
. Removal of Debris and Sediment. Sediment, debris, and trash, which impede the
hydraulic functioning of an infiltration trench will be removed and properly
disposed. Temporary arrangements will be made for handling the sediments until a
permanent arrangement is made.
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yomomoto Property, CT 04-01
. structural Repairs. Once deemed necessar/, repairs to structural components of an
Infiltration Trenche and its inlet and outlet structures will be done within 10 working
days. Qualified individuals (i.e., the designers or contractors) will conduct repairs
where structural damage has occurred.
. General Facility Maintenance. In addition to the above elements of corrective
maintenance, general corrective maintenance will address the overall facility and
its associated components. If corrective maintenance is being done to one
component, other components will be inspected to see if maintenance is needed.
6.02.3 Mo/nfenance Frequency
The maintenance indicator document, included as Appendix B, lists the schedule of
maintenance activities to be implemented at an Infiltration Trench.
. 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 quarterly basis during the non-rainy season or periods of dry weather.
6.02.4 Debris and Sediment Disposal
Waste generated at Infiltration Trenches is ultimately the responsibility of the property
owner. Disposal of sediment, debris, and trash will comply with applicable 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.
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.
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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 67.819(e) of the SO requires developers to provide clear written notification to
persons acquiring land upon which a BMP is located, or others assuming a BMP
maintenance obligation, of the maintenance duty.
Section 7.04 Subdivision Public Report
Tentative Mop 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 California
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.
Section 8.
Summary Conclusions
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:
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The beneficial uses for the receiving waters hove been identified. None of these
beneficial uses will be impaired or diminish due to the construction and operation
of this project.
The Yamamoto Property Subdivision project will not significantly alter drainage
patterns on the site. The discharge points will not be changed and gravel check
dams 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 and infiltration trenches 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.
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Section 9.
Certification
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 Date
Exp. 3/31/07
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Attachment A - Vicinity IVlap
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Storm Water PoHuHon Prevention Plan (SWPPP)
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Attactiment B - Site Plan
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SCALI: I'=i00'
CONSTRUCTION SITE PERIMETER
s
?3
-VEGETATED SWALE & INFILTRATION TfSNCH (TYP.)
NLB Engineering
Professional GvilEngneen and L/md Surveyors
600 Sooth Antenen DdfC Suiic E, BKOuUdaw CA 92029
Phone 760 74WS77 FAX 760 897-216S B^Mifl; MLBeneihapidxJljiet
YAMAMOTO PROPERTY TENTATIVE MAP
SWMP SITE PLAN
SHEET I OF I
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Attactiment C - Computation Sheet for Runoff Coefficients
Total Site Area 4.9 Acres (A)
Existing Site Conditions
Impen/ious Areai 0.3 Acres (B)
Impervious Area Runoff Coefficients 0.95 (C)
Pervious Area3 4.6 Acres (D)
Pervious Area Runoff Coefficient^ 0.45 (E)
Combined Runoff Coefficient 0.48 [BC+DE]/A
Proposed Site Conditions
Impen/ious Area^ 2.0 Acres (F)
Impervious Area Runoff Coefficients 0.95 (G)
Pervious Area3 2.9 Acres (H)
Pervious Area Runoff Coefficient* 0.45 (!)
Combined Runoff Coefficient 0.65 [FG+HI]/A
Notes:
1. Includes paved areas, areas covered by buildings and other impen/ious areas.
2. 95% assumed.
3. Includes areas of vegetation, unpaved soil areas, and other pen/ious areas.
4. Runoff Coefficient for rural areas per Appendix IX, Soil Type D, Son Diego Hydrology
Manual.
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Attachment D - Drainage Study
Refer to Drainage Study for Yamamoto Property Subdivision, CT 04-01 prepared by
MLB Engineering.
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