HomeMy WebLinkAboutCT 03-13; BLACK RAIL RIDGE; STORM WATER MANAGEMENT PLAN; 2004-08-02I
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ENGINEERING
Professional Civil Engineer and Land Surveyor
STORM WATER MANAGEMENT PLAN
for
CT 03·13 • Black Rail Ridge Subdivision
Prepared for:
Mayfair Hom~s
3443 Camino Del Rio South, Suite 312
San Diego, CA 92108
(619) 280-5777
Project Site Address
S.W. Corner, Black Rail Road & PoinseHia, Carlsbad, CA 92009
Prepared by:
Michael L. Benesh, R.C.E. 37893
Date:
August 2, 2004
600 s. ANDREASEN DRIVE' SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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storm water Management Plan (SWMP)
CT 03-13 -Black Rail Ridge Subdivision
Contents
Section 1. Introduction .................................................................................. 11 •••••••••••• 3
Section 1.01 Introduction .......................................................................................... 3
Section 2. Project ......................................................................................................... 3
Section 2.0 1 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 Groundwater ....................................................................................... 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 .................................................................... 1 0
5.02.1 Site Design BMPs ................................................................................ 10
5.02.2 Source Control BMPs ........................................................................ 10
5.02.3 Treatment Control BMPs .................................................................. 10
5.02.3(i) Sio-Filters ....................................................................................... 11
5.02.3 (i){a) Appropriate Applications and Siting Constraints: ......... 11
Section 6. Operation and Maintenance Program ....................... ~ ............................ 13
Section 6.01 Sio-Filters .............................................................................................. 13
6.01.1 Inspection Frequency ...................................................................... 1-3
6.01.2 Aesthetic and Functional Maintenance ...................................... 13
6.01.2(i) Aesthetic Maintenance ............................................................ 13
6.01.2(ii) Functional Maintenance .......................................................... 14
6.01.2 (ii}(a) Preventive Maintenance .................................................... 14
6.01.2 (ii) (b) Corrective Maintenance .................................................... 15
6.01.3 Maintenance Frequency ................................................................ 15
August 2, 2004 Pagei
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Engineering
storm Wafer Management Plan (SWMP)
CT 03-J3 -Black Rail Ridge Subdivision
6.01.4 Debris and Sediment Disposal ........................................................ 1 6
Section 7. Mechanisms to Assure Maintenance ..................................................... 16
Section 7.01
Section 7.02
Section 7.03
Section 7.04
Stormwater Ordinance Requirement: .......................................... 16
Notice to Purchasers ........................................................................ 1 6
Subdivision Public Report ................................................................ 16
Funding: ............................................................................................... 17
Section 8.
Section 9.
Summary Conclusions ............................................................................ 17
Certification ............................................................ l1li •••••••••••••••••••••••••••••••• 18
Attachment A -Vicinity Map ...................................................................................•.......... A-l
AHachment B .. Site Plan ....................................................................................................... 8-1
AHachment C -Computation Sheet for Runoff Coefficients ........................................... C-l
AHachment D -Drainage Study ..........................................................•.............................. D-1
August 2, 2004 Pageii
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Section 1.
Introduction
Section 1.01 Introduction
storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail RIdge Subdlvls10n
Per the National Pollution Discharge Elimination System {NPDES) permit (Order No.
2001-01 NPDES No. CAS0108758) the City of Carlsbad requires development and
significant redevelopment. that fall under the category of "priority projects" I include
Best Management Practices (BMP's) be incorporated to ensure that those projects
reduce potential urban pollutant runoff to the maximum extent practicable (MEP).
. The purpose of this SWMP is to address the water qualify impacts from the proposed
improvements on the Black Rail Ridge Subdivision. Best Management Practices (BMP$)
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.
Section 2.
Project
Section 2.01 Description
The project is a 3.6 acre site located in the City of Carlsbad I California.
The site is bordered by Black Rail Road on the East, Triton Street on the South and
Poinsettia Lane on the North.
The site is adjacent to single family homes on the South and North. To the East of the
project is a church site and to the West of the project is agricultural land with
greenhouses.
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, and Triton Street, as well as on-
site grading to create building pads. The amount of anticipated grading is
approximately 12/000 cubic yards.
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Section 2.02 Topography and Land Use
Storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rai' Ridge Subdivision
The site is currently being used for agricultural purposes, specifically as a nursery, and
has no permanent structures.
The surface of the land falls from the East to the West, with Black Rqil 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 Triton Street.
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 areas the strom water
runoff from this site eventually reaches the Batiquitos Lagoon arid the Pacific Ocean.
After development, the existing storm drain system in Poinsettia Lane will be extended
to the westerly border of the site. The storm drain system outlets into the natural
drainage area 600 feet west of 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 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.
August 2, 2004 Page 4
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Engineering
storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
• 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.
• 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 preservation 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 anadramous fish.
• RARE -Rare, threatened or endangered species: Includes uses of water necessary,
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)
CT 03-J 3 -Black Rail Ridge Subdivision
3.01. J Inland Sul1ace 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
AI: w -N Z Q Z AI: ...... AI: <.-' AI: U u 3: :':) <.-' Q 0 I-<t ...... z V) i <t w w A. -=e <C -&iii w =e AI: AI: AI: V) 3:
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
I:t:: w -N Z Q Z AI: ...... I:t:: = <.-' Q 0 I-<C <.-' AI: U u 3: ...... z V) i <C w w a.. -:e <C -;; w =e I:t:: I:t:: I:t:: V) 3:
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 patterns on the site or the
surrounding area. The Storm water discharge points will not divert runoff from existing
conditions.
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storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
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, Poinsettia
Lane and the construction of Triton Street. Black Rail Road 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.
Triton Street, which is currently only partially improved, will be 32 feet in width of AC
pavement, 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 0.7 acres of open ground will be covered by the single-family
residences and appurtenant driveways and an additional 0.6 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 1.3 acres.
This change in land use will increase the composite runoff coefficient, of the project,
from C=0.36 to C=0.52. Also, the total 10 year peak flow rate will increase from 3.8 cfs
under the existing condition to 6.2 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 Carlsbad. A copy of this report is included in Attachment D to
this report. See Table 4.1 and Attachment C for Impervious area calculations.
Table 4.1 -Impervious Areas & Runoff Coefficients
Construction site area 3.6 acres
Percentage impervious area before construction 10 %
Runoff coefficient before construction (1) 0.36
Percentage impervious area after construction 37 %
Runoff coefficient after construction (l) 0.52
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 the same outflow. 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 serves as a bio-filter for the runoff
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storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
generated from the area. A similar quantity of post-construction runoff will be directed
through an on-site vegetated swale prior to discharging into a storm drain system.
The remainder of the runoff, predominantly originating on the pavement on Triton
Street, will be directed via curb and gutter westerly on Triton Street where it will be
picked up by the storm drain system.
The storm drain system outlets into the natural drainage area westerly of the site.
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 (Triton Street) 1.6 3.3 0.24
B (Open 2.0 2.8 0.23 Space)
(1) Calculations are shown in Attachment 0
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 Wafer Management Plan (SWMP)
CT 03-J 3 -Slack Rail Ridge Subdivision
Section 4.03 3.3 Soil Characteristics
The project area consists of soil group C 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: 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 8MPs
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-l, Silt Fence
• SC-4, Check Dams
• SC-5, Fiber Rolls
• SC-7, Street Sweeping and Vacuuming
• TC-1, Stabilized Construction Entrance
• TC-3, Entrance/Outlet Tire Wash
• WE-1, Wind Erosion Control
• NS-l, Water Conservation Practices
• NS-2, Dewatering Operations
• NS-3, Paving and Grinding Operations
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storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
Engineering
• NS-6, Illicit Connection/Illegal Discharge 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 8MPs
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, Gardening, Pest
Control).
• Storm water Pollution Prevention Pet Waste.
• Storm water BMP Swimming Pool and Spa Cleaning.
5.02.3 Treatment Control BMPs
The following treatment control BMPs will be implemented to address water quality:
• Bio-Filters (Vegetated buffer strips and swales)
Placements of the BMPs are noted on the Project Site Plan (Attachment B) .
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N ~J Engineering
5.02.3(1) Bio-Filters
storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
Bio-filtration swales are vegetated channels that receive directed flow and convey
storm water. A schematic illustration of bio-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 ApplicaHons and SiHng 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: l} 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. Recommended minimum length for treatment purposes is 100
feet. Also, the maximum recommended width is 10 feet and the maximum
recommended depth of flow is 4 inces. Swales should also be sized as a cbnveyance
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. A minimum of 15 feet in length in the
direction of flow is recommended 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
landscape staff. Table 3.3.1 summarizes preliminary design factors for bio-filtration.
August 2, 2004 Page 11
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August 2, 2004
Storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
4:1 MIN. SIDE SLOPE
6" FREEBOARD
_____ JZ__ _ ______ _
________ I
DESIG FLOW DEPTH
WA TER QUALITY FLOW DEPTH
*------Wmml------~
SECTION
No SCALE
SECTION
No SCALE
ENGINEERED CHECK DAN (50'oc)
Figure 5-1 -Vegetated Swale
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~I·U. t :~} t:.J
Storm Wafer Management Plan (SWMP)
CT 03-13 -Black Rail Ridge SubdIvIsion
Engineering
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.
6.01.1 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.
6.01.2(i) 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.
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storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
• Weed Control. Weeds will be removed through mechanical means. Herbicide will
not be used because these chemicals may impact the water quolity monitoring.
6.01.2(6) 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 tb 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.
• 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.
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Engineering
6.01.2 (Ii)(b) Corrective Maintenance
Storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
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 10 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
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.
August 2, 2004 Page 15
C:\ProJect Documents\Lond Projects 2005\04-sdll 0 -CT03-13\SWMP.d<;>c
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storm water Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
• 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 the vegetated swale on lot 12 is ultimately the responsibility of
the Homeowners Association. Vegetated buffer strips on each residential lot will be
maintained by the individual homeowners. 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 City of Carlsbad 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 Notice to Purchasers.
Developers are required 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 7.03 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 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 app.licable to subdivisions which are
August 2, 2004 Page 16
C:\ProJect Documents\Land Projects 2005\04-sdll0-CT03-13\SWMP.doc
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;'~ ID<"J ., !,-
~~ J";
Engineering
storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
exempt from regulation under the Subdivided Lands Act, or for which no public report
will be issued.)
Section 7.04 Funding:
The homeowners association will be funded through monthly fees paid by the
homeowners as outlined in the public report to be issued for the sales of lots within the
subdivision.
Section 8.
Summary Conclusions
This SWMP has been prepared in accordance with the applicble City of Carlsbad
requirements. 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 Black Rail Ridge Subdivision project will not significantly alter drainage patterns
on the site.
• 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 2, 2004 Page 17
C:\Project Documents\Land Projects 2005\04-sdll0-CT03-13\SWMP.doc
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Engineering
Section 9.
Certification
storm Water Management Plan (SWMP)
CT 03-J 3 -alack Rail Ridge Subdivision
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
recommendationsl conclusionsl and decisions are based.
Michael L. Benesh l RCE 37893
EXp. 3/31 /d'f
August 2, 2004
C:\ProJect Documents\land Projects 2005\04-sdllO-CT03-13\SWMP.doc
Page 18
POOR
QUALITY
ORIGINAL S
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E';' ,',
" ;; /J ~ '1iW '
Engineering
storm Wafer Management Plan (SWMP)
CT 03-J 3 -Black Rail Ridge Subdivision
Attachment A -Vicinity Map
Black Rail Ridge Subdivision
Portion of U.S.G.S Encinitas Quadrangle
August 2, 2004 PageA-1
C:\Project Documenls\Lond Projects 2Q05\04-sdll 0 -CT03-13\SWMP.doc
I storm Wafer Management Plan (SWMP)
I CT 03-J 3 -Black Rail Ridge Subdivision
Engineering
I AHachment B -Site Plan
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II August 2, 2004 Page 8-1
! C:\ProJect Documents\Land Projects 2005\04-sdl10 -CT03-13\SWMP.doc
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:1
SCALE: /"=100'
--~~--------------------~ ---LANE
, __ --.------.--------1----
---=t-T I -----T"----" 1------f
IltD
BIO-FILTER LOCATION (TYf)
VEGETATED FILTER STRIP
INCORPORATED IN FRONT
YARD LANDSCAPING
Engineering
Profossional CitJil Engineers anti Land SIIfV!Yors
600 South ADdrcucn Dmc, SuiIc B. BacoDdIdo, CA 92029
Phoac 7(1) 741-3577 P.AX7(1) 897-2165 B-Md: ~
ONSTRUCTION SITE PERIMETER
CT 03-/3
SWMP SITE PLAN
SHEET I OF I
.------------------------------
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storm Wafer Pollution Prevention Plan (SWPPP)
CT03-13 -Black Rail Ridge Subdivision
Engineering
Affachment C -Computation Sheet for Runoff Coefficients
Total Site Area 3.6 Acres .....................................................................•...................... (A)
existing Site Conditions
Impervious Areal (B) ....................................................................................... 0.36 Acres
% Impervious Area (BI A) .............................................................................................. 10
Runoff Coefficient4 .................................................................................................... 0.36
Proposed Site Conditions
Impervious Areal (F) ........................................................................................ 1.33 Acres
% Impervious Area (F/ A) ........................................................................................... 0.37
Runoff Coefficient4 .................................................................................................... 0.52
Notes:
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 per Table 3-1, San Diego County Hydrology Manual.
August 2, 2004 Page C-1
C;lProject DocumentslLand Projects 2005\04·sd11 0 • CT03-13ISWMP.doc
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Engineering
Affachment 0 -Drainage Study
August 2, 2004
C;\Project Documents\Land Projects 2005\Q4.sd110 -CT03-13\SWMP.doc
storm Wafer Pollution Prevention Plan (SWPPP)
CT03-13 -alack Rail Ridge Subdivision
Page 0-1
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ENGINEERING
Professional Civil Engineer and Land Surveyor
DRAINAGE STUDY
TENTATIVE MAP CT 03-13
BLACK RAIL RIDGE SUBDIVISION
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Purpose
CT 03-13 Drainage Study
August 2, 2004
Page 1
The purpose of this Drainage Study is to determine and compare the Pre-Development and Post-Development ultimate
storm £lows for the proposed project, and to determine the Water Quality Design Storm flows for the developed site.
Ultimate Storm £lows will be based on the 10 year and 100 year 6 hour storm as defined in the San Diego County
Hydrology Manual. Water Quality Treatment Design Storm Flows will be based a storm event of 0.2 in/hr., which approximates
an 85th percentile storm event.
Site Description
The proposed site consists of approximately 3.6 acres and adjoins Black Rail Road to the East, Poinsettia Lane to the North
and Triton Street to the South. Currently the site is used for a plant nursery. There are no existing permanent structures.
The proposed development is an 11 lot subdivision.
There are no existing off-site storm £lows entering the site.
The storm runoff from the site, currently sheet £lows across the westerly property line to the adjoining properties.
Ultimately, all the runoff from this and adjacent sites ends up in a natural drainage area 600' westerly of this site. After
development, a storm drain system will carry the runoff from this site to the natural channel
Ifydrology
The Rational Method as outlined in the San Diego Hydrology Manual is used to determine peak flows. Initial time of
concentration, Ti is derived from Table 3-2 for the undeveloped site and for the developed site. Travel time is determined using
either Figure 3-4 (for the undeveloped site), Figure 3-6 (for street flows) of the manning equation for trapezoidal channels for
flows in earth or concrete swales. Soil Type for the site is Type B per the latest San Diego County Soils Group Map.
Table 1 -Anticipated vs. Existing 10 year Storm Flows
Drainage Facility Existing Condition Proposed Proposed
Flow from site, Q10 Development Flow Development Flow, Q2
(CFS) from site, Ql0 (CFS)
(CFS)
Triton Street -3.3 2.0
Westerly Property Line -2.8 2.4
Total 4.4 6.1 4.4
Desigll qf Vegetated Swale (Lots 1-5)
Ideally, vegetated swales should be used on sites with slopes of less than 4 percent; runoff velocities within channels can
become too high on steeper slopes, causing erosion and inhibiting infiltration and filtering in the swale. Swale bottoms should
not exceed 8 feet in width, with 4H:1V or flatter side slopes. The depth of the swale should carry the anticipated 10-year storm
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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cr 03-13 Drainage Study
August 2, 2004
Page 2
runoff with approximately 6 inches of freeboard. Typically, the swale should be designed to convey the runoff from a 2-year
storm event, without erosion. Table 2 summarizes the results of the hydrology and hydraulic calculations for the proposed
vegetated swale in Drainage Area 2c.
Table 1
Hydrologic and Hydraulic Results for Proposed Vegetated Swale, Area 2c
" § II '+1
i ~ ........ .E
0 .~ ~ u ~ Q '" '" s 8 = en ~ ~ ..... .E ~ '" ~ = ...... U 0
0 0 ~ '"
<:<S" '0 0 :! cJ ,.e..
~ ::s ~ l \:l:: I:t .e;. 0 8 0 & '0
0 J 0 ~ \:l:: ~ ~ o:S ~ ·m 0 I'< ~ ~ J ~~ ~ fr ~
Q ::E Q ::E
Water Quality Storm, 1.97 0.46 9.7 0.2 0.18 0.4 0.6
(1=0.2 in/hr.)
2-Year Storm 1.97 0.46 9.7 2.23 2.0 1.5 1.8
10-Year Storm 1.97 0.46 9.7 3.09 2.8 1.9 2.1
The total depth of the swale varies but is at least l' below the pad grades. The bottom width of the swale is approximately 8
feet, with a 2:1 slope against Poinsettia Lane, and a slope of approximately 4:1 on the southerly side.
A general rule of thumb for sizing vegetated swales. as noted in the information included in Appendix A, is one percent of
the area that drains into the swale. For the proposed swale on this project, the area required would be approximately 1180 square
feet, or a swale 8 feet wide by 148 feet long, The actual dimensions of this sWale will be 8 feet wide by 290 feet long
Based on the maximum velocity expected for the design storm, and the length of the swale, the hydraulic residence time for
runoff flowing through the swale is approximately 8 minutes.
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Tc & Imp Area Calculati01JS
Node 100 -101
Area = 0.24 Ac
Imp Area = 0.12 Ac
% Imp = 0.12/0.24 = 50%
Slope = 77.0-72.5/156 = 3%
Ti = 6.0 min.
Li = 90'
Using.
Tc = 6 min.
A = 90/156 * 0.24 = 0.14
I = 6.56 in/hr
C=0.60
Then Q = 0.6 cfs
Assuming £low of Q/2 for each side of the lot
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.3000 cfs
Slope ........................... 0.0300 ft./ft.
Manning's n ..................... 0.0200
Height .......................... 6.0000 in
Bottom width .................... 0.0000 in
Left. slope ...................... 0.0200 ft./ ft.
Right slope ..................... 0.0200 ft./ ft.
Computed Results:
Depth ........................... 0.8039 in
Velocity ........................ 1.3370 fps
Flow area ....................... 0.2244 ft2
Flow perimeter .................. 80.4031 in
Hydraulic radius ................ 0.4019 in
Top width ....................... 80.3871 in
Area ............................ 12.5000 ft2
Perimeter ....................... 600.1200 in
Percent full .................... 13.3978 %
Then V= 1.3 fps
Tt= (156-90)/(1.3*60) = 0.8 min.
Tc = 6.0 + 0.8 = 6.8 min.
Node 101 -102
Area = 1.40 Ac
Imp Area = 0.70 Ac
% Imp = 0.7/1.4 = 50%
Slope = 72.5-36.7/565 = 6%
CT 03-13 Drainage Study
August 2, 2004
Page 3
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Assuming Avg Q = 1.4*3/2 + 0.9 =3 cfs
V = 5.2 fps (Fig: 3.6)
Tt = 565/ (5.2*60)=1.8 min.
Node 200 -102
Area = 0.83 Ac
Imp Area = 0.54 Ac
% Imp = 0.53/0.83 = 64% use 65%
Node 300 -301
Area = 0.58 Ac
Imp Area = 0.20 Ac
% Imp = 0.20/0.58 = 34% use 35%
Slope = 67.0-64.0/200 = 1.5% use 2%
Ti = 7.8 min. (fable 3-2, interpolated between 30% and 40% Imp.)
Li = 80'
Using:
Tc = 7.8 min.
A = 80/200 * 0.58 = 0.23
I = 5.54 in/hI:
C =0.52
Then Q = 0.7 cfs
Assuming flow of Q/2 for each side of each lot:
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.2000 cfs
Slope ........................... 0.0150 ft/ft
Manning's n ..................... 0.0200
Height .......................... 6.0000 in
Bottom width .................... 0.0000 in
Left slope ...................... 0.0200 ft/ ft
Right slope ..................... 0.0200 ft/ft
Computed Results:
Depth ........................... 0.7863 in
Velocity ........................ 0.9316 fps
Flow area ....................... 0.2147 ft2
Flow perimeter .................. 78.6469 in
Hydraulic radius ................ 0.3931 in
Top width ....................... 78.6312 in
Area ............................ 12.5000 ft2
Perimeter ....................... 600.1200 in
Percent full .................... 13.1052 %
Use V= 1 fps
Tt= (200-80)/(1*60) = 2.0 min.
Tc = 7.8 + 2.0 = 9.8 min.
600 S. ANDREASEN DRIVE' SUITE E • ESCONDIDO, CA 92029
CT 03-13 Drainage Study
August 2, 2004
Page 4
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Node 301-302
Area = 0.27 Ac
Open Space/Landscape area, use 0% Imp.
Ignore Length of Downdrain in determining Tt.
Assuming Avg Q = 0.27*1/2 + 1.3 =1.45 cfs (1 cfs/ac -open space)
Manning Pipe Calculator
Given Input Data:
Shape ........................... Elliptical
Solving for ..................... Depth of Flow
Minor axis ...................... 24.0000 in
Major axis ...................... 36.0000 in
Flowrate ........................ 1.4500 cfs
Slope ........................... 0.0200 ft./ft.
Manning's n ..................... 0.0150
Computed Results:
Depth ........................... 3.0212 in
Area ............................ 4.7124 ft2
Wetted Area ..................... 0.3435 ft2
Wetted Perimeter ................ 24.9215 in
Perimeter ....................... 95.1927 in
Velocity ........................ 4.2214 fps
Hydraulic Radius ................ 1.9847 in
Percent Full .................... 12.5882 %
Full flow Flowrate .............. 46.6548 cfs
Full flow velocity .............. 9.9005 fps
Use V= 4.2 fps
Node 302 -303
Area = 1.12 Ac
Imp Area = 0.15 Ac
% Imp = 13% use 20%
Ignore Length of Downdrain in determining Tt.
Assuming Avg Q = 1.12*2/2 + 1.6 =2.7 cfs (2 cfs/ac)
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 2.7000 cfs
Slope ........................... 0.0200 ft./ft.
Manning's n ..................... 0.0200
Height .......................... 6.0000 in
Bottom width .................... 96.0000 in
Left. slope ...................... 0.5000 ft./ ft.
Right slope ..................... 0.2500 ft./ft.
Computed Results:
Depth ........................... 1.5128 in
Velocity ........................ 2.5564 fps
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
CT 03-13 Drainage Study
August 2, 2004
Page 5
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Flow area ....................... 1.0562 ft2
Flow perimeter .................. 105.6200 in
Hydraulic radius ................ 1.4400 in
Top width ....................... 105.0766 in
Area ............................ 4.7500 ft2
Perimeter ....................... 134.1550 in
Percent full .................... 25.2128 %
Use V= 2.6 fps
Storm Drain f!ydraulic Grade line Calculatio1ls
cr 03-13 Drainage Study
August 2, 2004
Page 6
Hydraulic grade line calculations are based on the Mannings equation. Outlet losses are based on the velocity head.
In cases of subcritical flow, the grade line is calculated in an upstream direction for the reach adding friction loss to the
downstream grade line elevation.
In the case of supercritical flow; the grade line is based on an assumption of critical depth at the manhole or Catch Basin
outlet and flow in the downstream pipe is assumed to be normal depth for the reach.
Catch Basin Capacity -T fito1l Street
In the interim condition, with the berm installed at the West end of Triton Street to direct the street flow across the street
from the South, the catch basin will operate in a sump condition. Ultimately, when Triton is widened to its full 40' width and a
catch basin is installed to pick up the South side flows, the catch basin will operate in an intercept condition.
Interim Condition:
Q100=7.8 cfs
L=14'
S= 0.01
Local Depression = 0.33'
Therefore: Depth @ Inlet = (QI (L *3.0)) 2/3 = 0.33'
Ultimate Condition
Q100=4.9 cfs
L=14'
S= 0.01
Local Depression = 0.33'
Depth of Flow in Gutter = 0.38' (Using Figure 3-6)
Capacity = 0.7(0.33+0.38) 3/2 (14)=5.9 cfs > 4.9 cfs
Capacity of Type F AC Dike
Q100 = 7.8-4.9 = 2.9 cfs
S = 0.04
Therefore:
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Solving for ..................... Depth of Flow
Flowrate ........................ 2.9000 cfs
Slope ........................... 0.0400 ft./ ft.
Manning's n ..................... 0.0175
Height .......................... 6.0000 in
Bottom width .................... 0.0000 in
Left. slope ...................... 0.3000 ft./ ft.
Right slope ..................... 0.0200 ft./ ft.
Computed Results:
Depth ........................... 2.1486 in
Velocity ........................ 3.3921 fps
Flow area ....................... 0.8549 ft2
Flow perimeter .................. 114.9312 in
Hydraulic radius ................ 1.0712 in
Top width ....................... 114.5943 in
Area ............................ 6.6667 ft2
Perimeter ....................... 320.9406 in
Percent full .................... 35.8107 %
Depth of Flow = (2.15/12) = 0.18' < 0.5' OK
HGL @ existing Manhole -Sta 0+00
From Dwg, No. 360-3B, Ql00 existing at outlet of SD = 12.7 cfs.
Adding Q from site and ignoringTc variations, Qtotal = 12.7 + 10.2 = 22.9 cfs
Section Downstream of Pipe = 2.5' Wide Rectangular channel, s=0.02
Therefore:
Channel Calculator
Given Input Data:
Shape ........................... Rectangular
Solving for ..................... Depth of Flow
Flowrate ........................ 22.9000 cfs
Slope ........................... 0.0200 ft./ ft.
Manning's n ..................... 0.0150
Height .......................... 30.0000 in
Bottom width .................... 30.0000 in
Computed Results:
Depth ........................... 11.7142 in
Velocity ........................ 9.3835 fps
Flow area ....................... 2.4405 ft2
Flow perimeter .................. 53.4284 in
Hydraulic radius ................ 6.5775 in
Top width ....................... 30.0000 in
Area ............................ 6.2500 ft2
Perimeter ....................... 90.0000 in
Percent full .................... 39.0474 %
Depth Down Stream of Outlet = (11.7/12) = 1.0'
Assume Hgl @ outlet = soffit of pipe = 309.50
Therefore:
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
CT 03-13 Drainage Study
August 2, 2004
Page 7
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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Manning Pipe Calculator
Given Input Data:
Shape ........................... Circular
Solving for ..................... Friction Slope
Diameter ........................ 18.0000 in
Depth ........................... 18.0000 in
Flowrate ........................ 22.9000 cfs
Manning's n ..................... 0.0150
Computed Results:
Slope ........................... 0.0633 ftlft
Area ............................ 1.7671 ft2
Wetted Area ..................... 1.7671 ft2
Wetted Perimeter ................ 56.5487 in
Perimeter ....................... 56.5487 in
Velocity ........................ 12.9587 Cps
Hydraulic Radius ................ 4.5000 in
Percent Full .................... 100.0000 %
Full flow Flowrate .............. 22.9000 cfs
Full flow velocity .............. 12.9587 fps
Sf, flowing full = 0.063
V= 13.0 fps
HGL @ S'ly Inlet = 309.50 + (0.063)(51.79) = 312.76'
Inlet Loss = 1.2 V2/2g = 3.15'
HGL upstream = 312.76 + 3.15 = 315.91'
Q upstream = 7.3 + 10.2 = 17.5 cfs
Therefore:
Manning Pipe Calculator
Given Input Data:
Shape ........................... Circular
Solving for ..................... Friction Slope
Diameter ........................ 18.0000 in
Depth ........................... 18.0000 in
Flowrate ........................ 17.5000 cfs
Manning's n ..................... 0.0150
Computed Results:
Slope ........................... 0.0370 ftlft
Area ............................ 1.7671 ft2
Wetted Area ..................... 1.7671 ft2
Wetted Perimeter ................ 56.5487 in
Perimeter ....................... 56.5487 in
Velocity ........................ 9.9030 fps
Hydraulic Radius ................ 4.5000 in
Percent Full .................... 100.0000 %
Full flow Flowrate .............. 17.5000 cfs
Full flow velocity .............. 9.9030 fps
Sf, flowing full = 0.0370
V upstream = 9.90 fps
HGL @ Proposed Manhole = 315.91 +,28.38(0.037) = 316.96'
600 S. ANDREASEN DRIVE' SUITE E • ESCONDIDO, CA 92029
CT 03-13 Drainage Study
August 2, 2004
Page 8
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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HGL @ Manhole-Sta 2+42.64
Q downstream = Q upstream = 10.2 cfs
Invert Downstream of manhole = 328.50'
18" RCP
s=0.0802
Therefore:
Manning Pipe Calculator
Given Input Data:
Shape ........................... Circular
Solving for ..................... Depth of Flow
Diameter ........................ 18.0000 in
Flowrate ........................ 10.2000 cfs
Slope ........................... 0.0802 ft/ ft
Manning's n ..................... 0.0150
, Computed Results:
Depth ........................... 7.8685 in
Area ............................ 1.7671 ft2
Wetted Area ..................... 0.7425 ft2
Wetted Perimeter ................ 26.0054 in
Perimeter ....................... 56.5487 in
Velocity ........................ 13.7371 fps
Hydraulic Radius ................ 4.1115 in
Percent Full .................... 43.7141 %
Full flow Flowrate .............. 25.7815 cfs
Full flow velocity .............. 14.5893 fps
Critical Information
Critical depth .................. 15.4735 in
Critical slope .................. 0.0095 ft/ft
Critical velocity ............... 6.0257 fps
Critical area ................... 1.6928 ft2
Critical perimeter .............. 41.2213 in
Critical hydraulic radius ....... 5.9134 in
Critical top width .............. 18.0000 in
Specific energy ................. 3.5883 ft
Minimum energy .................. 1.9342 ft
Froude number ................... 3.4285
Flow condition .................. Supercritical
Supercritical flow condition, assume Dc at outlet.
Dn = 7.9/12 = 0.66'
Vn = 13.7 fps
Dc=15.5/12 = 1.29'
Vc=6.0 fps
Outlet Loss = 1.2v2/2g = 0.67'
HGL @ Manhole = 328.50 + 0.67 + 1.29 = 330.46'
600 S. ANDREASEN DRIVE' SUITE E • ESCONDIDO, CA 92029
CT 03-13 Drainage Study
August 2, 2004
Page 9
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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HGL @ CB -St04+ 30.80
Q downstream = 10.2 cfs
Q upstream = 7.8 cfs
Invert Downstream of CB = 332.45'
18" RCP
s=0.02
Therefore:
Manning Pipe Calculator
Given Input Data:
Shape ........................... Circular
Solving for ..................... Depth of Flow
Diameter ........................ 18.0000 in
Flowrate ........................ 10.2000 cfs
Slope ........................... 0.0200 ft/ ft
Manning's n ..................... 0.0150
Computed Results:
Depth ........................... 12.0925 in
Area ............................ 1.7671 ft2
Wetted Area ..................... 1.2624 ft2
Wetted Perimeter ................ 34.5880 in
Perimeter ....................... 56.5487 in
Velocity ........................ 8.0799 fps
Hydraulic Radius ................ 5.2557 in
Percent Full .................... 67.1805 %
Full flow Flowrate .............. 12.8747 cfs
Full flow velocity .............. 7.2856 fps
Critical Information
Critical depth .................. 15.4735 in
Critical slope .................. 0.0095 ft/ft
Critical velocity ............... 6.0257 fps
Critical area ................... 1.6928 ft2
Critical perimeter .............. 41.2213 in
Critical hydraulic radius ....... 5.9134 in
Critical top width .............. 18.0000 in
Specific energy ................. 2.0217 ft
Minimum energy .................. 1.9342 ft
Froude number ................... 1.5617
Flow condition .................. Supercritical
Supercritical flow condition, assume Dc at outlet.
Dn = 12.09/12 = 1.01'
Vn = 8.1 fps
Dc=15.5/12=1.29'
Vc=6.03 fps
Outlet Loss = 1.2v2/2g = 0.68'
HGL @ CB = 332.45 + 0.68 + 1.29 = 334.42'
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
cr 03-13 Drainage Study
August 2, 2004
Page 10
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@'PACBELL.NET
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HGL@CB-Sta4+30.80
Q downstream = 7.8 cfs
Invert Downstream of CB = 333.15'
18" RCP
s=0.005
Depth of Water @ 4+32.30 = 334.42-332.57 = 1.85'
Therefore:
Manning Pipe Calculator
Given Input Data:
Shape ........................... Circular
Solving for ..................... Friction Slope
Diameter ........................ 18.0000 in
Depth ........................... 18.0000 in
Flowrate ........................ 7.8000 cfs
Manning's n ..................... 0.0150
Computed Results:
Slope ........................... 0.0073 ftl ft
Area ............................ 1.7671 ft2
Wetted Area ..................... 1.7671 ft2
Wetted Perimeter ................ 56.5487 in
Perimeter ....................... 56.5487 in
Velocity ........................ 4,4139 fps
Hydraulic Radius ................ 4.5000 in
Percent Full .................... 100.0000 %
Full flow Flowrate .............. 7.8000 cfs
Full flow velocity .............. 4.4139 fps
Critical Information
Critical depth .................. 13.2558 in
Critical slope .................. 0.0087 ft/ft
Critical velocity ............... 5.5102 fps
Critical area ................... 1.4155 ft2
Critical perimeter .............. 36.7860 in
Critical hydraulic radius ....... 5.5412 in
Critical top width .............. 18.0000 in
Specific energy ................. 1.7344 ft
Minimum energy .................. 1.6570 ft
Froude number ................... 0.5916
Flow condition .................. Subcritical
Subcritical flow condition.
Sf flowing full = 0.0073
V=4,41 fps
HGL Downstream of CB = 334.42 + (0.0073)(116.41) = 335.27'
Outlet Loss = = 1.2v2/2g = 0.36'
HGL @ CB = 335.27 + 0.36 = 335.63'
TC @ Inlet = 337.10
CF = 6" + 4" = 10" =0.83'
Freeboard = 337.10 0.83 335.63
600 S. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
CT 03-13 Drainage Study
August 2, 2004
Page 11
= 0.64'
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
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San Diego County Soils Group Map
Group A
GroupB
Group C
GroupD
Undetermined
Unknown
600 s. ANDREASEN DRIVE· SUITE E • ESCONDIDO, CA 92029
PHONE: 760 741-3577 • FAX: 760 897-2165 • E-MAIL: MLBENESH@PACBELL.NET
-------------------
Rational Method Calculation Form
Project: CT 03-13
Drainage Soil & A C CA I:CA I
Frequency 100 Year
Post-Development
Q Slope Section
Area Development Acres In.lHr. CFS
100-101 B -50'10 Imp 0.24 0.58 0.14 0.14 6.05 0.8
B -50'10 Imp 0.06 112 St 101-102 1.40 0.58 0.81 0.95 5.20 4.9
200-102 B -65'10 Imp 0.83 0.67 0.56 1.51 5.20 7.8 0.005 21" RCP
300-301 B -35'10 Imp 0.58 0.48 0.28 0.28 4.78 1.3 0.02 301-302 B -0'Yo Imp 0.27 0.25 0.07 0.35 4,60 1.6 D-75
Swale 302-303 B -20'Yo Imp 1.12 0.38 0.43 4:14 0.02 0.77 3.2
Conf 303 Qn See SD County Hydrology Manual 10.2
Qu See SD County Hydrology Manual 9.4
303 Qn 4.44 2.28 10.2
"
,'.' .
'.
,
.' .;;:~}:.\.:.~.:.:,
V L T
'/Sec. Ft. Min.
5.2 565 1.8
4.5 120 0.4
4.2 150 0.6
2.6 290 1.9
SumT
6.8
8.6
8.6
9.1
9.8
10.4
12.3
10.9
Calculated by MB
Date:2 August 2004
Remarks
See Tc Cales.
Fig. 3.6, See Cales
S 'Iy Side Triton
Conf@ 303
See Tc Cales.
2'Yo V-Gutter
2'10 Swale -Conf 303
Te=[(I(CA)7.44P6 )/Q]1.55
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-------------------
Rational Method Calculation Form
Project: CT 03-13
Drainage SoU & A
Area Development Acres
100-101 B -50% Imp 0.24
101·102 B -50'Yo Imp 1.40
200-102 B -65'Yo Imp 0.83
300-301 B -35'Yo Imp 0.58
301-302 B -O'Yo Imp 0.27
302-303 B -20% Imp 1.12
C CA l:CA I
In./Hr.
0.58 0.14 0.14 3.89
0.58 0.81 0.95 3.34
0.67 0.56 1.51 3.34
0.48 0.28 0.28 3.07
0.25 0.07 0.35 2.96
0.38 0.43 0.77 2:66
Conf 303 Qn See so County Hydrology Manual
QT2 See SO County Hydrology Manual
303 Qn 4.44 2.28
........ "
::~ ~::~!:: '" ';0
Frequency 10 Year
Post-Development
Q Slope Section
CFS
0.5
3.2 0.06 112 St
5.0 0.005 21" RCP
0.9
1.0 0.02 0-75
0.02 Swale 2.1
6.6
6.1
6.6
V L
'/Sec. Ft.
5.2 565
4.5 120
4.2 150
2.6 290
T SumT
Min.
1.8 6.8
8.6
0.4 8.6
9.1
9.8 0.6 10.4 1.9 12.3
10.9
Calculated by MB
Date:2 August 2004
Remarks
See Te Cales.
Fig. 3.6, See Cales
S 'Iy Side Triton
Conf @ 303
See T e Cales.
2'Yo V-Gutter
2'Yo Swale -Conf 303
Te=[(I(CA)7.44P6)/Q]1.55
~ ----------~ -----
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~~-----~~~-~-~-~-----------------------------..... -------------------
Rational Method Calculation Form
Project: CT 03-13
Drainage Soil & A
Area Development Acres
100-101 B -50% Imp 0.24
101-102 B -50'Yo Imp 1.40
200-102 B -65% Imp 0.83
300-301 B -35,},o Imp 0.58
301-302 B -O'Yo Imp 0.27
302-303 B -20'Yo Imp 1.12
C CA ~CA I
In.lHr.
0.58 0.14 0.14 2.81
0.58 0.81 0.95 2.41
0.67 0.56 1.51 2.41
0.48 0.28 0.28 2.22
0.25 0.07 0.35 2.14
0.38 0.43 0.77 1.92
Conf 303 Qn See SD County Hydrology Manual
QT2 See SD County Hydrology Manual
303 Qn 4.44 2.28
. , .
.
. ~ '\ ~ ' .. ', ': ~
Frequency 2 Year
Post-Development
Q Slope Section
CFS
0.4
2.3 0.06 112 St
3.6 0.005 21" RCP
0.6 0.02 D-75 0.7 0.02 Swale 1.5
4.7
4.4
4.7
V L
'/See. Ft.
5.2 565
4.5 120
4.2 150
2.6 290
T SumT
Min.
1.8 6.8
8.6
8.6 0.4 9.1
9.8 0.6 10.4 1.9 12.3
10.9
Calculated by MB
Date:2 August 2004
Remarks
See Te Cales.
Fig. 3.6, See Cales
S 'Iy Side Triton
Conf@ 303
See Te Cales.
2% V-Gutter
2'Yo Swale -Conf 303
Tc=[(I(CA)7.44P6)/Q]1.55
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Rational Method Calculation Form
Project: CT 03·13
Drainage Soil & A
Area Development Acres
Area A B -10% Imp 3.58
.
·;,·:--.:i ....
C CA :ECA
0.32 1.15 1.15
.,."
I
Frequency 100 Year
Pre·Development
Q Slope Section
In.IHr. CFS
4.54 5.2
..
V L
'/See. Ft.
T SumT
Min.
10.6
Calculated by MB
Date:2 August 2004
Remarks
L= 675'
Slope::: 7"10
Table 3-2 (Interpolated)
Lm:::l00', Ti:::7.4 Min
Tt= 3.2 Min (Fig 3-4)
Tc:::7.4+3.2=10.6
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Rational Method Calculation Form
Project: CT 03·13
Drainage Soil & A
Area Development Acres
Area A B -1010 Imp 3.58
. .:~. :/~~·i?~ ... , .. ,
C CA I:CA I
hl.lHr.
0.32 1.15 1.15 2.92
..
' .
. ..
Frequency 10 Year
Pre.Development
Q Slope Section
CFS
3.3
V L T
'/See. Ft. Min.
SumT
.
10.6
Calculated by MB
Date:2 August 2004
Remarks
L = 675'
Slope = 7%
Table 3"2 (Interpolated)
Lm=100', Ti=7,4 Min
Tt= 3.2 Min (Fig 3-4)
Tc=7.4+3.2=10.6
1
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---~ , -------------------
\,'-.J
\:)
( (
COUNTY OF SAN DIEGO
DEPARTMENT OF SANITATION ,
FLOOD CONTROL
10-YEAR 6·HOU~ PRECIPITATIOr-J
r16-ISGPLUVIAlSlof 1Q-YEAR (}-UaUn
45' -I 'lo!~~
.'
30 1 I I ' " -( h lJJ " j
IS' I 1'''\ 1 ... 1-1
3)'
4S' 1 I . .. I J ._.-.... __ ..... --_. --...-. .--. , . _ . .,
PNlI'l"d by
t1.S, DEPARTME~T OF COM~ERCE
NATIONAl., OCEANIC ANI) /t.1' l()IU'rnUjl~ ADMINISTRATION
SP!:CfAt. 'STUDfU DltANCU. O"Ief: OF I OROLOOY, HATIONAI. W£ATHllt IlltVJCI
30 I I '~ .. ---.
IISQ Its' 30' 15' 1170
:.:;, "',
45' 30',
(
IS' 116-
-------------------
.... ' ... =r~ --o
1 . ,
COi./i\lTY OF SAN OIEGO. •
DEPARTMENT OF SANITATION So
FLOOD CONTROL 10-YEAR 24-HOUR PRECIPITATION
'-20./ ISOPlUVIAlS bf 10-YEAR 24 .. HOUR
45' ;p"> < '.\f{~ '~
151 1'1---:-+----1
33·
4S' I ~
U.S. DEPARTMEfi'I' OF COMMERCE
NATION AL OCEANIC AND "TI.lO!IJIIlItRIC !'.RWl"ISTRATIOH
30'4·1---I------iI---_i-____ t-____ ~-_
n6° 45' 30' lS' 117° tiS I 30'
,
IS' Jl6°
-------------------)
COUNTY OF SAN DIEGO .
DEPARTMENT OF S~~tTATrON &
FLOOD CONTROL
J
2-YEAR 6-HOUR PRECIPITATIO~l
;-10-ISOPLUVIALS OF 2·YEAR 6 .. HOUR
4S I I 'l;!wr,.'I{",...J "~'.,,,
30' I 'l
15' I I) l-.lt \. ; .,
3'·'
4; t ; I' ,I uif. (AN}1I0a 1":Sl~ <1J.' ,r ~~
, P'.P~~db)'
U,S. DEPART~IENT OF COMMERCE
NATIONAL OCtANIC Al'lb ATMOSPHERIC AOMIN1'TRATlON
'II:C1A1. STUDIU BRAl'lCH. OFFiCe of IIVnROLOO\'. NATIONAL "'BATH~Jt IERVICI
\~
~
30 1
II SO I.; J 30' I 45' 30' tit IS'
.,
15 I , 1,6·
-------------------
'.
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" .
COUNTY OF SAN DIEGO • DEPARTMENT OF SANITATION &
FLOOD CONTROL
• '\ .. '
.. ,,-,
45'
30'
IS'
4$'
I Pr.p.'"d by
I U.S. DEPARTMENT OF COMMERCE
NATIONAL O(:F.Aj-llt: AjIIO "TMO!WHEIUC ADMINISTItATlO"
SPECIAL S'rI.lDI!! DRANCH, O"'ICt 0' HYDROLOGY, NAT10N"t. lV&ATHEIt S~"YlCC
'1.01--' I T
M 'r :r OON
v.J
30'
1180
....
..
'.5' 30' lS' l1t
1
45' 30' 15' 1160
---
10.0
9.0
8.0
7.0
6.0
~
~
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5.0 )"
01' loo.
4.
.... ....
....
I"-.~
....
.... '" . , ,.,.. 3.
2
'C' i -5 1 .S ...... 0 ~ l!lO
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o 1
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~
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---
~ " i'o " "" ~ .....
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"'" '" I-"" ~ ... I' r.... ...."" ~
"-~"" ~ ~ r"-i'o ~
t..... l' " ,,... "-
.... " I I' "I ~
l'r-
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:
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5 6 7 8 910 15 20 30
Mihute!\)
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40 50
Duration
---
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EQUATION
I ::i 7.44 P6 0-0.645
I = Intensity (in/hr)
Ps = 6·Hour Precipitation ( in) o = Duration (min)
i
'-1'-0
~ I'-o~ I' r"-I'" I~I"-. " I· I'~I'
1,,,1'
1"0-i' I'
I' I
Ii' 1-
~ J ~
f'" I
I· "" '" I I ,...
I-i'o
~t'-
1"0-" -
~ .... -. -~.--
" I 1
r
Hours
-
~ if Si
'0 iii
6.0 ~,
5.5 ~
5.0 !f
4.55-
4.d g. 3.S!
3.0
2.5
2.0
1.5
1.0
Intenslty..ouratlon Design Chart -Template
------
Directions for Application:
(1) From precipitation maps determine S hr and 24 hr amounts
for the selected frequency. These maps are induded In the
County Hydrology Manual (10, 50. and 100 yrmaps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it is within
the range of 45% to 65% of the 24 hr precipitation (not
applicaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart.
(4) Draw a line through the pOint parallel to the plotted lines.
(5) This line Is the intenslty-dUration curve for the location
being analyzed.
Application Form:
(a) Selected frequency ~ year
P /.-
(b)P6= ~ln"P24" "2.D 'P:4= ~%(2)
(c) Adjusted P6(~)" ..l..::..:L in.
(d) tx" __ min.
(e) I ,. __ in.lhr.
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
P6 , 1.5'("2" .... 2'.5 3' 3.5! 4 4.5 5' 5.5 .. 6" Ouralloni I . Ii'" . i ':"''1''' .. j ...... j" ..... ( ..... ,":""j': I
... : .... ~.~ "g .. ?~ ;~ .. ~~t ~,.??.6.5~ ..7-99: 9.~: 10.54. 1~.86: 13.1?! 14:49. 1~,.~1
" ... 7 . ?c12".~:~~t ~.?4 .. 5,!3Q;.6:~. 7.42, ~.4S.; 9.54 : lq.60111.66: 12.72
10 1.66 2.53! 3.37 4.21! 5.05' 5.90. 6.74 7.&8 6.42, 9.27 10.1\ ..... L ..t:~:jA~~~~~E~;2E~;~~;~;~~"5.)~ : .. ~~.:. 6;4("J.,1(:t7?:.
20 1.08; 1.6212 •. 15 ;.?.6~; ~,2.:,J; ~:.?7 ...:...4:!3L.1,-f!~"'"S.!~~.i.?.~3., ti,4!l 25 0.93 1.4011.87 2.33 2.80:3.27: 3.73 4.20; 4,67' 5.13: 5.60
sO ii.8S i1.?.ii 1,66),67:2 . .(9~2.9~; 3 .. ~g: ~:.13.: ~,15; ~,!?6! 4.98 .... 1~ .M9 ; 1.0~{ 1.,38 .. 1.72.2.07,2.41: 2.76. 3.10 : 3.45: 3.79 i 4.13
liP 0:60. :q:~O!..1..1.9: 1..49 .. p9 ,?,~~ ?39 , 2,!?~ ... ?,j18 .;.=!.g~ ~ ~.!?ll
.. _ .... ~ .0.53 ;0.8°11.06.1.33: 1.59.1.86; 2.12.2.39: 2.6512.92; 3.16
........ ?I! .. 9..~1 .• O.61LQ·~. 1.,<>2".H?;.1.1!3. 1:6~ .. 1.81; '~'~.: .?·~§.i ?.~?
l;lO 0.34 ;O,51l 1l.6B;0.85: 1.02: '1.19: 1.36.1.53 .1.70',1.87\ 2.04 ..... li: -~~X·~g::~!·g:;~·jg:~~··~:~1·~~'·U~· ~:~~; ~:~; ;'~:~~H:~;'
.: ..... : 2~ ~Q,~ .. : 0.33r9A~j ~:~ .. :.9:~~~.O.~~; o'i,'i . O:9if~ 1.~: :'.1)~.L..1:~9 ..
300 0.19 0.28'0.38'0.47;0:56'0.00 0.75 0.85' 0.94 1.03! 1.13 360 '0,17 '0.251'0:33; 0:·i2';·o:sij"O:5S"·O.6i 0.75'; ·0.84· .... 0:92 i 1:00'
FIGURE ~
-
---
10.0
9.0
8.0
7.0 .....
i'
t'
, ..... 6.0
5.0 Ii'
4. ) I
N....
3. ) :
2
J <.:11 .5 ~o ~ r .sO
o
, ,
['0.,
) .
i
I
.0
9
. 8
7 I
.6 ;
"" .,....
.....
" ..... . .....
t--. '" •
"'"
'" ......
° .5 : . ,
o
: f lJ
.4 ! I !
o "'3 I
'.2
"""
:-1-H-"
I ..
--
"""
.... [00.
"" ~
~ i'o ~
..... i'o I'--I-I'--
I'" ~ ..... " !."
r-., "I' ....
[00., I'~ '" ~ ""'.
'" ~
f' "I ! .....
[oo.,r-.,
1'-0.
" I
I I 1
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Dumtion
---
1 .1
I II I I 1
EQUATION
I = 7.44 Pe 0-0.645
I :: Intensity (in/hr)
Pa = 6.Hour Precipitation (I n)
D = Duration (min)
I I
i 1""'1'-0. I I
1'-0. 1'-0. "" .... 1'--I .. I'--
I"'-1'''
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-
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5.5 g
5.0 g'
4.55-
4.0 ~
3.5 !!!-
3.0
2.5
2.0
1.5
1.0
2 3 4 5 6
Hours
Intensity-Duration' Design Chart· Template
------
Directions for Application:
(1) From precipitation maps determine 6 hr and 24 hr amounts
for the selected frequency. These maps are induded in the
County Hydrology Manual {10, 50, and 100 yr maps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it is within
the range of 45% to 65% of the 24 hr precipitation (not
appllcaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart.
(4) Draw a line through the point parallel to the plotted lines.
(5) This line is the intensity-duration curve for the location
being analyzed.
Application Form:
(a) Selected frequency ltJ£L year
(b)P6= 2.€:> in"P24= 4.5 .;a = ~ %(2)
"7 (1 24 (c) Adjusted Pe(2) = ~in.
(d) tx = __ min.
(e) J ;:: __ in.lhr.
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
P6 .. 1" "1.s'1""··f . '~:5" 3 3.5 4 4,5 5 ~ 5.5 6
Duration 1 I'; j' . j"" j · ..... C·;· T" j" ... ,. r' "."': ",
. "-""5 2.63 3.9515.27' 6.59 7.90'9.22: 10.54 11.!16·13.17j 14.49,15.81 .......... .t .·.g;12 ):l.·~r 4:24 ;·@).:6.36:7.42; 8.48: 9.54 : 1<?60111;6~] 1':1:'12
10 1 .. ~. ?A:ll~!~:L.1,.?L!?.!.~?. .. §·.9!L .~.,?1_ .... ?,§!L .. ~,1?~.n?. J.(H~. ... 1~ .. !:~~ .. JJ..?f&'~§!:~?1.:.~.~~; ~.~~; 5,19 .. ~~1 ... ~.4.9.i..7,1.~.; 7,?l'!.
20 1.08. 1.62! 2.1.5 i.~,!,!~ : 3!g;q:!.?.~~1.....i&f! .... !):.~. ~. ?:~: ~,4~ ~~ . o:~~ . ~ .491 1.~!; 2.~ . ?:80. 3,27: 3.73 . 4,20 ; 4.67 i 5.13: 5.60.
30 0.83; 1.?411.66:2.07.2.4~:~·~9; ~,~~. ~.73.: 4.15 L4.5!?: 4.98
~ .O.t?9 . 1.0:1!1.~8: 1.72.2.01.2.41: 2.76. 3.10. 3.45 ~ 3.7914.13
~ O.6~ .0.90.f 1.1J!: 1;~9 .. ).79 .. 2.Q~: ? .. 3~ .. ~,6~ .. , ?·~~.l 3:2.~.1. ~,~!I. 60 0.53 '0.80' 1.06: 1.33 1.59 1.86' 2.12' 2.39 2.65 i 2.92: 3.18
::.":.:' .. ~ ·.9.:~t l~·~.llQ·~~: 1 .. !!(.1,2~;1:4~: ).:~:( 1.~.: ~,p4:! ~:J.~; ?'.~~. ~~ 0.34 iO.51\0.68:0.85;1.02:1.19i 1.39; 1.53. 1.70~ 1.67,2.04
.... J.~!L9.Z!., 0.44 •. Q:~~.l.~ . .1.~ .• .9. .. ~~ :.):.(l .. ~., 1:.18.: 1.32 , 1.47 • 1.£!? U.:!.6 ....... J~ . Q;2!3 .• O,39!51,§? i.9:~5.~ o.?!>; !J.9.1.!.1A4 ; .. 1:1.!-1. ... ).:~1 ..... 1:~; ~.57
.. ...... ~~ .Q,~ .. iQ:~~l.Q·.13"()I~,g .. l!l};.O}!3~ M7: 0.98. 1·~ .. , I:J.~.d .. 39..
. ~ .. ():~9 .. !0.28;.Q!?81.~:~U!'~; o.~~: .().7.!! .iJ)·~ ~ .9.'.~ .. ;)-,~. U .. J!3 360 0.17 0.25;0.33.0.42'0.50 0.560.67; 0.75' 0.840.92' 1.00
FIGURE ~
-
----
10.0
9.0
8.0
7.0
6.0
...... ....
~
"
5. ~ l"
4.
3.
2.
I -g1
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...... i'" ~ I" .... I .... " , ~ " i', ,
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'" ~
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15 20 30 M/riUfa'~
- -
t 1 il
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,
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40 50
Duration
----
----~--------
III 1
. lUll ~
1111 1
EQUATION
I -= 7.44 P6 0-0.645
I = Intensity (In/hr)
Pa = 6·Hour Precipitation
D = Duration (min)
1'1'
I' l' I"l'" i"'or-. I" ~
'1'1'
'1'1' I' , I'
r-. ,
" 1 I 1'1' '" ,
I .. i'
"
"I' i"'o~ t
-
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2 3
Hours
I
J
I
(in)
i
'U iil 6.0~:
5.5 ~
5.0 g
4.55-
4.0 g.
3.5 !
3.0
2.5
2.0
1.5
1.0
lntenlity-Duratlon Design Chart -Template
---- --
Directions for Application:
(1) From precipitation maps determine 6 hr and 24 hr amounts
for the selected frequency. These maps are included in the
County Hydrology Manual (10, 50, and 100 yr maps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it is within
the range of 45% to 65% of the 24 hr precipitation (not
applicaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart.
(4) Draw a line through the point parallel to the plotted lines .
(5) This line is Ihe intenslty.duration curve for the location
being analyzed.
Application Form:
(a) Selected frequency ~ year
(b) Pa = .L..fL in., P24 = ~ ,pPs :: 58 %(2) 24 --
(C) Adjusted P6(2} = J.J.L in.
(d) tx :: __ min.
(e) I = __ in.lhr.
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
P6 '''1' 1.5·i" 2'" 2',5' 3 "'3.5: 4 . 4.5' 5 : '5.5'" 6'
Duration' I . ,": '('" i'" 'r'" ",": T"'j .... ·1 .; .... 1' .. ; j'
......... ) .. ~:.~. '~'~~f.!?:.?1. .. ~~9 ].90. 9.;22pO.54. 11.86. 13:17; 1~.49J.-?~I.
. ......... 1.? .. 1~. :3'.\.~14.l?'U.ilO".6:3~. 7.42~.8.48 . ~.54 .. IO.69111.6SiI2.72 10 .1:® : 2.5~1 ~:~? d:g,I.~.~,~? :.~:~o..l.~,?4 .. ...?·~ .... 8'.1? .U~:~.? ; 1.D., ~) .
.. ,,1.~ )!~tL.~:~.~.;..?:~.~_;~,?1.:.~c8~:~.?1. 5.J~.: ~.~4 .. ~.1H?·1~.f..? .. !9..
20 1.08 '.1.62; 2.15.; ?:?~ . ~.!?~: .. ?T!3:.~~ ..... _1:jI'?' .. ,.~:~.l.?:~~ : 6.~6 ~~ 9:9~.; 1.4~i 1'1I! I ;?:?~ . 2 .. 80 . 3.27 i S.73 : 4.20 . 4.67 : 5.13 : 5.S!>.
30 0.88! 1.24! 1'~12,07 .2.49 .2.~~;.~ .. ~~ .. , .~?~ .. 4 •. 15i 4.,f?~ i 4.98 .... '!9. .. O,~ : 1.03[ 1.~8: 1.72.2.07.2.41 i 2.76 . 3.10 . 3.45; 3.79 i 4.1? ~ 0.60. :q:~o.L1 .. 1j1~ ,:~~. F9 .2:Q~i ~:39 :.~~~ .. 2,~ t ~:2~ L 3.!?8 . .• " .... §4) .0 .. 5;3 ;0.80/1.06: 1.33.1.59. I.B6; 2.12 . 2.39 • 2.65 i 2.92: 3.18
...... ~ .!!.~1. iO.61\.0~~:U .. .Q.?.,; giU.:43: 1:~3_j .1.!\4 •. ?:~ ~.~.?l!j.2.~~. 1~ 0.34 10.5110.68iO.85; '1.02.1.19,1.36; 1.53: 1.70: un; 2.04
150 0.29 :0.441 0.59iO.73· 0.88: 1.03' 1.18' 1.32' 1.47 1.62".76 ...... "-' " ..... ,. r'''''' , ... " .. " ....................... ' .. . '" "" ........ , .. ..... "..1~ 9,,2~.iO.3!\9.:?~i ~ .. ~5.:I?:~!I:.O':~~.:.1·~~.l .. U.~l.1.:~L .. ~:~ ~ '1.57 240 0.22 :O.3310.43.0.54·0.6510.76! 0.87,0.98: 1.OS 1.19' 1.30 .... ~ -Q.j9:: O.28r9.;~·!.QA~A,~;M6: Q.7~ ~.Q.~5 .:. 9:9(. (9.:(":i'.'1.3:
3fiO 0.17 0.2510.33;0.42·0.50'0.58 0.67; 0.7510.84 0.92! 1.00
FIGURE ~
-
-------------------
1.\"
San Diego County Hydrology Manual
Date: June 2003
Table 3-1
Section:
Page:
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use Runoff Coefficient "C"
Soil TIEe
NRCS Elements Coun Elements %IMPER. A B
Undisturbed Natural Terrain (Natural) Pennanent Open Space 0* 0.20 0.25
Low Density Residential (LOR) Residential, 1.0 DU/A or less 10 0.27 0.32
Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38
Low Density Residential (LOR) Residential, 2.9 DU/A or less 25 0.38 0.41
Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45
Medium Density Residential (MDR) Residentil:ll, 7.3 DU/A or less 40 0.48 0.51
Medium DQ1lSity Residential (MDR) Residentil:ll, 10.9 DU!A or less 45 0.52 0.54
Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58
High Density Residential (HDR) Residential, 24.0 DUI A or less 65 0.66 0.67
High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77
C01IllllerciaIlIndustrial (N. Com) Neighborhood Co1Illllercial . 80 0.76 0.77
ComItlerciallIndustrial (G. Com) General Commercial 85 0,80 0.80
CommerciaIlIndustrial (O.P. Com) Office Professional/Commercial 90 0.83 0,84
CommerciaIlIndustrial (Limited I.) Limited Industrial 90 0.83 0.84
General Industrial 95 0.87 0.87
C
0.30
0.36
0.42
0.45
0.48
0.54
0.57
0.60
0.69
0.78
0.78
0.81
0.84
0,84
0.87
3
6 of 26
D
0.35
0.41
0,46
0,49
0.52
0.57
0.60
0.63
0.71
0.79
0.79
0.82
0.85
0.85
0.87
*The values associated with 0% impervious may be used for direct calCtilation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff
coefficient, Cp, for the soil type), orfor areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area
is located in Cleveland National Forest).
DUI A = dwelling units pet acre
NRCS = National Resources Conservation Service
3-6
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I
San Diego County Hydrology Manual
Date: June 2003
Section:
Page:
3
12 of 26
Note that the Initial Time of Concentration should be reflective of the general land-use at the
upstream end of a drainage basin. A single lot with an area of two or less acres does not have
a significant effect where the drainage basin area is 20 to 600 acres.
Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in
hydrology studies. Initial Ti values based on average C values for the Land Use Element are
also included. These values can be used in planning and design applications as described
below. Exceptions may be approved by the "Regulating Agency" when submitted with a
detailed study.
Table 3-2
MAXIMUM OVERLAND FLOW LENGTH (41)
& INITIAL TIME OF CONCENTRATION (Til
Element* nUl .5% 1% 2% 3% 5% 10%
Acre LM Ti LM Ti LM Ti LM Ti LM Ti LM Ti
Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9
LDR 1 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4
LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8
LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6
MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3
MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8
MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5
MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3
HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5
HDR 43 50 5.3 65 4.7 . 75 4.0 85 3.8 95 3.4 100 2.7
N.Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7
G.Com 50 4.7 60 4.1 75 3.6-85 3.4 90 2.9 100 2.4
O.PJCom 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2 .. 6 100 2.2
General 1. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9
*See Table 3-1 for more detailed description
3-12
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I
EQUATION
.6.E
Feet Tc = c~~3r·385
5000 Tc
L =
4000 = .6.e
Time of concenlr"ation (hours)
Watercourse Distance (miles)
Change in elevation along
effective slope line (See Figure 3-5)(feet)
3000
2000
.6.E
SOURCE: California Division of Highways {1941} and Kirpich (1940)
L Miles Feet
3000 ,
l
, ,
Tc
Hours Minutes
,
3
" , ,
Tc
240
180
120
50
20
Nomograph for Determination of
Time of Concentration (Tel or Travel Time (Ttl for Natural 'M:Ifersheds
I
I
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I
·1
I
I
I
I
'I
I
I
1
I
II
/
........,n = .015-+-~ _
2% _ __ _n=.0175 --------~------~ 2%
2
EXAMPLE:
Concrete
Gutter
Given: Q = 10 S = 2.50/.
3
Paved
0.13
4 5 6 7 8 9 10
Discharge (C_F.S.)
Chart gives: Depth = 0.4, Velocity = 4.4 f.p.s.
SOURCE: San Diego County Depaltment of Special District Services Design Manual
Gutter and Roadway Discharge -Velocity Chart
ZQ_--
RESIOENllAL STREET
ONESIDEONLY
20 30 40 50
FIGURE ~
~~~
WlPOS'ED S. D. pE!/.:1t1Muff.Il
'O<;:)~
t.)tO"
II II
'vI
0 1
ir
••
1
...
----
-
---------:QIO = I. 0 ,.~"-.----
RECONST. DRIVEWAY TO JOIN-"£/ Ss PROPOSED STREET IMPROVEt1ENTS
DWG 422-8
-------
4:lt SLOPE
8 067}J
PRIVA TE SHARED ACct'sSf
8 UTILITY EASEM'ENT ::.'i~I-
61.21'
~\PJ\j 2j-5~070~OB
-"" . .--,'
/vJ~S ~
POST -DEVELOPMENT HYDROLOGY
--
PRE-DEVELOPMENT HYDROLOG Y
S~HT DISTANCE CORRIIOOR,
PER FINAL HAp
0.27 Ac -------. "'-
o % / M P ______ '"
:'24 AC\
50%"IMP \ I: r-\
(i=J74!J I·---r--(i=J771>-&\
. ~\ 1
.)
I
~~--~ ----
/-----
ir
1
1
1
SCALE 1"=40'
+ SCALE 1'=40'
CT 03-/3
Engineering
Proftssional Civil Engineers and LAnd S uroryors
600 South Andreasen Drive. Suite E. Escondido, CA 92029
HYDROLOGY MAP -02/010/0100
phone 760741-3571 PAX 760 897-2165 E-Mail: MLBencsh@padlciLnet
I: .