HomeMy WebLinkAboutCDP 2017-0024; Highland James Subdivision (Highland Drive Portion); Storm Water Quality Management Plan; 2020-12-08
CITY OF CARLSBAD
PRIORITY DEVELOPMENT PROJECT (PDP)
STORM WATER QUALITY MANAGEMENT PLAN (SWQMP) FOR
3980 HIGHLAND AVENUE
PROJECT ID (CT/MS/SDP/CDP/PD) CDP: 15-47, 15-48 & 15-49, 2017-0024, 2017-0025, CT-08-06
PARCEL Nos. 207-130-75 to 78 DRAWING No. (DWG 483-6B & 483-6C, 483-6D) SWQMP No. 16-28; GR2020-0028
ENGINEER OF WORK:
_____________________________________________________________________________
William O’Gorman CALIFORNIA PROFESSIONAL ENGINEER LICENSE #: 88286
PREPARED FOR:
VECK INVESTMENT PROPERTIES, INC. 33276 HIGHLAND DRIVE
CARLSBAD, CA 92008 (619) 204-4903
PREPARED BY:
REC Consultants, Inc.
2442 Second Ave.
San Diego, CA 92101 (619) 232-9200
DATE:
December 8th, 2020 WILLIAM M. O'G
ORMANCIV I LST
A
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OF CAL I F O R N IAREGISTERED P R O FESSION
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ENGI
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TABLE OF CONTENTS
Certification Page
Project Vicinity Map
FORM E-34 Storm Water Standard Questionnaire Site Information FORM E-36 Standard Project Requirement Checklist
Summary of PDP Structural BMPs
Attachment 1: Backup for PDP Pollutant Control BMPs
Attachment 1a: DMA Exhibit Attachment 1b: Tabular Summary of DMAs and Design Capture Volume Calculations
Attachment 1c: Harvest and Use Feasibility Screening (when applicable)
Attachment 1d: Categorization of Infiltration Feasibility Condition (when applicable)
Attachment 1e: Pollutant Control BMP Design Worksheets / Calculations Attachment 2: Backup for PDP Hydromodification Control Measures Attachment 2a: Hydromodification Management Exhibit
Attachment 2b: Management of Critical Coarse Sediment Yield Areas Attachment 3: Single Sheet BMP (SSBMP) Exhibit
CERTIFICATION PAGE
Project Name: __Highland-James Subdivision_ Project ID: _ CDP: 15-47, 15-48 & 15-49, 2017-0024, 2017-0025, CT-08-06_ Parcel Numbers: 207-130-75 to 80
I hereby declare that I am the Engineer in Responsible Charge of design of storm water BMPs for this project, and that I have exercised responsible charge over the design of the project as defined
in Section 6703 of the Business and Professions Code, and that the design is consistent with the requirements of the BMP Design Manual, which is based on the requirements of SDRWQCB Order No. R9-2013-0001 (MS4 Permit) or the current Order.
I have read and understand that the City Engineer has adopted minimum requirements for managing urban runoff, including storm water, from land development activities, as described in
the BMP Design Manual. I certify that this SWQMP has been completed to the best of my ability and accurately reflects the project being proposed and the applicable source control and site design BMPs proposed to minimize the potentially negative impacts of this project's land
development activities on water quality. I understand and acknowledge that the plan check review of this SWQMP by the City Engineer is confined to a review and does not relieve me, as the Engineer in Responsible Charge of design of storm water BMPs for this project, of my
responsibilities for project design.
_____________________________________________________
Engineer of Work's Signature, PE Number & Expiration Date
_William O’Gorman__________________________________________
Print Name
_REC Consultants, Inc.________________________________________
Company
_12/8/2020__________________________ Date WILLIA M M. O'G
O
RMANCI V I LST
A
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OF CAL I F O R N IAREGISTERE D P R OFESSION
A
L
ENGINEER
PROJECT VICINITY MAP
Project Name: __ Highland-James Subdivision_ Project ID: _ CDP: 15-47, 15-48 & 15-49, 2017-0024, 2017-0025, CT-08-06_
Parcel Numbers: 207-130-75 to 80
Project Vicinity Map
Source: Google Earth
E-34 Page 1 of 4 REV 03/19
Development Services
Land Development Engineering
1635 Faraday Avenue
(760) 602-2750
www.carlsbadca.gov
STORM WATER STANDARDS
QUESTIONNAIRE
E-34
INSTRUCTIONS:
To address post-development pollutants that may be generated from development projects, the city requires that new development and significant redevelopment priority projects incorporate Permanent Storm Water Best Management
Practices (BMPs) into the project design per Carlsbad BMP Design Manual (BMP Manual). To view the BMP Manual, refer to the Engineering Standards (Volume 5).
This questionnaire must be completed by the applicant in advance of submitting for a development application
(subdivision, discretionary permits and/or construction permits). The results of the questionnaire determine the level of storm water standards that must be applied to a proposed development or redevelopment project. Depending on the outcome, your project will either be subject to ‘STANDARD PROJECT’ requirements or be subject to ‘PRIORITY
DEVELOPMENT PROJECT’ (PDP) requirements.
Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts. City staff has responsibility for making the final assessment after submission of the development application. If staff
determines that the questionnaire was incorrectly filled out and is subject to more stringent storm water standards than initially assessed by you, this will result in the return of the development application as incomplete. In this case, please
make the changes to the questionnaire and resubmit to the city. If you are unsure about the meaning of a question or need help in determining how to respond to one or more of the
questions, please seek assistance from Land Development Engineering staff.
A completed and signed questionnaire must be submitted with each development project application. Only one completed and signed questionnaire is required when multiple development applications for the same project are
submitted concurrently.
PROJECT INFORMATION
PROJECT NAME: PROJECT ID:
ADDRESS: APN:
The project is (check one): New Development Redevelopment
The total proposed disturbed area is: ________ ft2 (________) acres
The total proposed newly created and/or replaced impervious area is: ________ ft2 (________) acres
If your project is covered by an approved SWQMP as part of a larger development project, provide the project ID and the
SWQMP # of the larger development project:
Project ID SWQMP #:
Then, go to Step 1 and follow the instructions. When completed, sign the form at the end and submit this with your application to the city.
Highland James - Lots 1 & 2
3970 & 3980 Highland Drive
16-28
207-130-79 & 80
45,200 1.04
CT 08-06
19,128 0.43
* = Because this project is covered by a previously approved SWQMP as part of a larger development, this form (including
the areas above) were completed for the final buildout of both projects. For just this permit, see below for the areas:
Total impervious per this permit only: 7,100 sf / 0.16 ac
Total disturbed area per this permit only: 22,250 sf / 0.51 ac
It should be noted that the impervious area from this permit is less than the planned impervious area from the previously
approved SWQMP (The impervious area from DMAs N1a, N1b,N2a & N2b was 10,118 sf)
*
*
CDP 2017-0024 & 25
C cityof
Carlsbad
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STEP 1 TO BE COMPLETED FOR ALL PROJECTS
To determine if your project is a “development project”, please answer the following question:
YES NO
Is your project LIMITED TO routine maintenance activity and/or repair/improvements to an existing building
or structure that do not alter the size (See Section 1.3 of the BMP Design Manual for guidance)?
If you answered “yes” to the above question, provide justification below then go to Step 5, mark the third box stating “my
project is not a ‘development project’ and not subject to the requirements of the BMP manual” and complete applicant information.
Justification/discussion: (e.g. the project includes only interior remodels within an existing building):
If you answered “no” to the above question, the project is a ‘development project’, go to Step 2.
STEP 2 TO BE COMPLETED FOR ALL DEVELOPMENT PROJECTS
To determine if your project is exempt from PDP requirements pursuant to MS4 Permit Provision E.3.b.(3), please answer the following questions:
Is your project LIMITED to one or more of the following: YES NO
1. Constructing new or retrofitting paved sidewalks, bicycle lanes or trails that meet the following criteria:
a) Designed and constructed to direct storm water runoff to adjacent vegetated areas, or other non-erodible permeable areas; OR
b) Designed and constructed to be hydraulically disconnected from paved streets or roads; OR c) Designed and constructed with permeable pavements or surfaces in accordance with USEPA
Green Streets guidance?
2. Retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in accordance with the USEPA Green Streets guidance?
3. Ground Mounted Solar Array that meets the criteria provided in section 1.4.2 of the BMP manual?
If you answered “yes” to one or more of the above questions, provide discussion/justification below, then go to Step 5, mark
the second box stating “my project is EXEMPT from PDP …” and complete applicant information.
Discussion to justify exemption ( e.g. the project redeveloping existing road designed and constructed in accordance with
the USEPA Green Street guidance):
If you answered “no” to the above questions, your project is not exempt from PDP, go to Step 3.
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E-34 Page 3 of 4 REV 03/19
STEP 3
TO BE COMPLETED FOR ALL NEW OR REDEVELOPMENT PROJECTS
To determine if your project is a PDP, please answer the following questions (MS4 Permit Provision E.3.b.(1)):
YES NO
1. Is your project a new development that creates 10,000 square feet or more of impervious surfaces
collectively over the entire project site? This includes commercial, industrial, residential, mixed-use,
and public development projects on public or private land.
2. Is your project a redevelopment project creating and/or replacing 5,000 square feet or more of
impervious surface collectively over the entire project site on an existing site of 10,000 square feet or more of impervious surface? This includes commercial, industrial, residential, mixed-use, and public
development projects on public or private land.
3. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface collectively over the entire project site and supports a restaurant? A restaurant is
a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption (Standard Industrial
Classification (SIC) code 5812).
4. Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a hillside development project? A hillside
development project includes development on any natural slope that is twenty-five percent or greater.
5. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface collectively over the entire project site and supports a parking lot? A parking lot is
a land area or facility for the temporary parking or storage of motor vehicles used personally for business or for commerce.
6. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more
of impervious street, road, highway, freeway or driveway surface collectively over the entire project site? A street, road, highway, freeway or driveway is any paved impervious surface used for the
transportation of automobiles, trucks, motorcycles, and other vehicles.
7. Is your project a new or redevelopment project that creates and/or replaces 2,500 square feet or more of impervious surface collectively over the entire site, and discharges directly to an Environmentally
Sensitive Area (ESA)? “Discharging Directly to” includes flow that is conveyed overland a distance of
200 feet or less from the project to the ESA, or conveyed in a pipe or open channel any distance as an
isolated flow from the project to the ESA (i.e. not commingled with flows from adjacent lands).*
8. Is your project a new development or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface that supports an automotive repair shop? An automotive repair
shop is a facility that is categorized in any one of the following Standard Industrial Classification (SIC)
codes: 5013, 5014, 5541, 7532-7534, or 7536-7539.
9. Is your project a new development or redevelopment project that creates and/or replaces 5,000 square
feet or more of impervious area that supports a retail gasoline outlet (RGO)? This category includes
RGO’s that meet the following criteria: (a) 5,000 square feet or more or (b) a project Average Daily
Traffic (ADT) of 100 or more vehicles per day.
10. Is your project a new or redevelopment project that results in the disturbance of one or more acres of land and are expected to generate pollutants post construction?
11. Is your project located within 200 feet of the Pacific Ocean and (1) creates 2,500 square feet or more of impervious surface or (2) increases impervious surface on the property by more than 10%? (CMC
21.203.040)
If you answered “yes” to one or more of the above questions, your project is a PDP. If your project is a redevelopment project, go to step 4. If your project is a new project, go to step 5, check the first box stating “My project is a PDP …”
and complete applicant information.
If you answered “no” to all of the above questions, your project is a ‘STANDARD PROJECT.’ Go to step 5, check the
second box stating “My project is a ‘STANDARD PROJECT’…” and complete applicant information.
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STEP 4
TO BE COMPLETED FOR REDEVELOPMENT PROJECTS THAT ARE PRIORITY DEVELOPMENT PROJECTS (PDP) ONLY
Complete the questions below regarding your redevelopment project (MS4 Permit Provision E.3.b.(2)):
YES NO
Does the redevelopment project result in the creation or replacement of impervious surface in an amount
of less than 50% of the surface area of the previously existing development? Complete the percent impervious calculation below:
Existing impervious area (A) = __________________________ sq. ft. Total proposed newly created or replaced impervious area (B) = _________________________sq. ft.
Percent impervious area created or replaced (B/A)*100 = __________%
If you answered “yes”, the structural BMPs required for PDP apply only to the creation or replacement of impervious
surface and not the entire development. Go to step 5, check the first box stating “My project is a PDP …” and complete applicant information.
If you answered “no,” the structural BMP’s required for PDP apply to the entire development. Go to step 5, check the
check the first box stating “My project is a PDP …” and complete applicant information.
STEP 5 CHECK THE APPROPRIATE BOX AND COMPLETE APPLICANT INFORMATION
My project is a PDP and must comply with PDP stormwater requirements of the BMP Manual. I understand I must prepare a Storm Water Quality Management Plan (SWQMP) for submittal at time of application.
My project is a ‘STANDARD PROJECT’ OR EXEMPT from PDP and must only comply with ‘STANDARD PROJECT’ stormwater requirements of the BMP Manual. As part of these requirements, I will submit a “Standard Project
Requirement Checklist Form E-36” and incorporate low impact development strategies throughout my project. Note: For projects that are close to meeting the PDP threshold, staff may require detailed impervious area calculations
and exhibits to verify if ‘STANDARD PROJECT’ stormwater requirements apply. My Project is NOT a ‘development project’ and is not subject to the requirements of the BMP Manual.
Applicant Information and Signature Box
Applicant Name: Applicant Title: Applicant Signature: Date:
* Environmentally Sensitive Areas include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); water bodies designated with the RARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); areas designated as preserves or their equivalent under the Multi Species Conservation Program within the Cities and County of San Diego; Habitat Management Plan; and any other equivalent environmentally sensitive areas which have been identified by the City.
This Box for City Use Only
City Concurrence:
YES NO
By:
Date:
Project ID:
Principal
10/16/20
Elizabeth Temple, Veck Investment Properties
4,340
19,128
440
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SITE INFORMATION CHECKLIST
Project Summary Information
Project Name Highland-James Subdivision
Project ID
CDP: 15-47, 15-48 & 15-49, 2017-0024,
2017-0025, CT-08-06
Project Address 3980 Highland Drive Carlsbad, CA 92008
Assessor's Parcel Number(s) (APN(s)) 207-130-75 to 80
Project Watershed (Hydrologic Unit) Carlsbad 904
Parcel Area 1.06 Acres (46,349 sq-ft)
Existing Impervious Area (subset of Parcel Area) 0.10 Acres (4,340 sq-ft)
Area to be disturbed by the project
(Project Area) 1.14 Acres (49,653 sq-ft)
Project Proposed Impervious Area
(subset of Project Area) 0.51 Acres (22,146 sq-ft)
Project Proposed Pervious Area
(subset of Project Area) 0.63 Acres (27,507 sq-ft)
Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the Project. This may be less than the Parcel Area
Please note that in this case the Area to be Disturbed by the Project is greater than the Parcel Area because there is some work (0.08 acres) associated with the project’s utility connections and
driveway aprons outside of the property lines (a.k.a. offsite work).
This SWQMP has been prepared for CDPs 15-47, 15-48, 15-49, 2017-0024, and 2017-0025 for Lots 1, 2
and 3 of Map 15082 and lots 1 & 2 of Map 16234, associated with APNs 207-130-75 to 80, respectively. The following table breaks down the total areas within each Lot in terms of proposed impervious and pervious areas and provides the associated CDPs and APNs for clarity.
LOT CDP APN Parcel
Area
Parcel
Area
Proposed
Imp. Area
Proposed
Imp. Area
Proposed
Perv. Area
Proposed
Perv. Area
# # # sq-ft ac sq-ft ac sf ac
1 of Map 15082 15-47 207-130-75 7505 0.17 3937 0.09 3568 0.08
2 of Map 15082 15-48 207-130-76 7505 0.17 4107 0.09 3398 0.08
3 of Map 15082 15-49 207-130-77 7505 0.17 3984 0.09 3521 0.08
1 of Map 16234 2017-0024 207-130-79 11917 0.27 3582 0.08 8335 0.19
2 of Map 16234 2017-0025 207-130-80 11917 0.27 3521 0.08 8396 0.19
There are 2 additional DMAs (N1a and N2a) in the Highland Ave. right-of-way that drain to Lots 4 and 5, as follows:
DMA Total
Area
Total
Area
Proposed
Imp. Area
Proposed
Imp. Area
Proposed
Perv. Area
Proposed
Perv. Area
# sq-ft ac sq-ft ac sf ac
N1a 1625 0.04 312 0.00 1313 0.03
N2a 1678 0.04 324 0.00 1354 0.03
Description of Existing Site Condition and Drainage Patterns
Current Status of the Site (select all that apply)
Existing development
Previously graded but not built out
Agricultural or other non-impervious use
Vacant, undeveloped/natural
Description / Additional Information The existing site contains one free standing home with a detached garage on APN 207-130-78.
Existing Land Cover Includes (select all that apply) Vegetative Cover
Non-Vegetated Pervious Areas
Impervious Areas
Description / Additional Information
Impervious features -- house, garage and driveway. Established vegetative cover on remainder.
Underlying Soil belongs to Hydrologic Soil Group (select all that apply):
NRCS Type A
NRCS Type B
NRCS Type C
NRCS Type D
According to a site-specific Soils Report generated on USDA NRCS WSS the site is Type B.
Approximate Depth to Groundwater: Groundwater Depth < 5 feet 5 feet < Groundwater Depth < 10 feet
10 feet < Groundwater Depth < 20 feet Groundwater Depth > 20 feet
The actual depth to groundwater is not known. A Soils Report generated on the USDA NRCS WSS indicates that the depth to water table is greater than 200 mm. A Site Inspection (09/02/05)
performed by Soil Testers, Inc., had borings up to 15-ft without encountering groundwater.
Existing Natural Hydrologic Features (select all that apply)
Watercourses
Seeps Springs
Wetlands None
Description / Additional Information None identified
Description of Existing Site Topography and Drainage [How is storm water runoff conveyed from
the site? At a minimum, this description should answer (1) whether existing drainage conveyance
is natural or urban; (2) describe existing constructed storm water conveyance systems, if applicable; and (3) is runoff from offsite conveyed through the site? if so, describe]:
The subject site is a residential parcel located on the easterly side of Highland Drive. The property
is located at the top of a rise with the east side of the site fronting James Drive approximately 15 to 20 feet lower than the west side. A 10-foot, approximately 2:1 cut slope extends midway through
the site from the south to north. A 2-to-3 feet fill slope is located at the top of the cut on the north end. The property is presently occupied by a one-story single-family residence with a detached garage and driveway. There is a four-foot retaining wall behind the garage and a 3-foot rock
retaining wall behind the house.
There is a 12-inch public storm drain (with a 5-ft easement) that conveys runoff from Highland
Drive eastward through the site along its northern perimeter down to James Drive; however the property does not contain any storm drain infrastructure for stormwater generated onsite. Existing
topography dictates that stormwater runoff sheet flows along the ground surface of the property
from west to east and discharge offsite and onto James Drive at the sites eastern edge. In pre-development conditions the entire site may be considered as a single drainage management
area with one point of discharge (at its eastern perimeter). Once the runoff discharges onto James Drive it is collected by a curb inlet on the west side of the
street which is part of the municipal separate storm sewer system (MS4) owned and operated by
the City of Carlsbad. The City MS4 conveys the runoff further downstream to the Agua Hedionda Lagoon with ultimate discharge into the Pacific Ocean along Carlsbad State Beach (at Tamarack
jetties and at the discharge for the Encina Power Station).
Description of Proposed Site Development and Drainage Patterns
Project Description / Proposed Land Use and/or Activities:
This SWQMP has been prepared for CDPs 15-47, 15-48, 15-49, 2017-0024, and 2017-0025 for
Lots 1, 2 and 3 of Map 15082 and lots 1 & 2 of Map 16234, associated with APNs 207-130-75 to 80, respectively.
The proposed development will demolish the existing home/detached garage, and ultimately
construct 5 new free standing single family homes with driveways. Post-development activities at the site will be consistent with typical residential activities currently conducted throughout the City.
List/describe proposed impervious features of the project (e.g., buildings, roadways, parking lots, courtyards, athletic courts, other impervious features):
Proposed impervious features include 5 free standing single family homes and their associated driveways. In total the project proposes 19,767 sq-ft (0.43 acres) of new impervious surfaces
List/describe proposed pervious features of the project (e.g., landscape areas):
Proposed pervious features include the front, back and side yards of the 5 free standing homes including the slope separating the two benches. Efforts will be made to preserve some of the existing vegetation, although grading activities are planned on almost the entire site. All of the
permeable areas will be vegetated/landscaped.
Does the project include grading and changes to site topography?
Yes
No
Description / Additional Information: The proposed grading will more or less maintain the same pattern, with the uphill portion tying into Highland Avenue and the downhill connecting to James Drive. The two existing benches at the
top and bottom of the slope will be extended in order to construct the proposed building pads for the homes. Swales will be incorporated to convey flows around the lower bench and along the
perimeters and in between Lots 1, 2 and 3.
Does the project include changes to site drainage (e.g., installation of new storm water
conveyance systems)?
Yes No
Description / Additional Information: A combination of swales and inlets/storm drain will be incorporated near the toe of the slope and
in between Lots 1, 2 and 3 of Map 15082. A series of swales and brow ditches will route runoff
from lots 1 &2 of of Map 16234 to two proposed biofiltration basins with partial retention prior to existing the basin via a storm drain pipe. Runoff will still discharge along the sites eastern edge
but will be collected by an onsite storm drain system and piped into the existing curb inlet on James Drive (this is the projects sole point of discharge). The swales convey drainage throughout the site and facilitate cross lot drainage in accordance with the existing drainage easements
detailed on Map 16021 for Carlsbad Tract CT-08-06-01. The proposed grading/swales/inlets effectively subdivide the site into 12 Drainage Management Areas (DMAs) which all combine and discharge into the City MS4 (at the James Drive inlet), and have the following characteristics:
• DMA N1a is 0.037-acres (19% impervious) and an area within the public right-of-way along
Highland Avenue that flows onto DMA N1b. DMA N1a consists of landscaping and the driveway for
Lot 2 of Map 16234 that ties into Highland Avenue.
• DMA N1b is 0.274-acres (29.5% impervious) and contains proposed Lot 2 of Map 16234. DMA N1b accepts run-on from DMA N1a. Runoff discharges into a Bioretention BMP for pollutant control. Flows leaving the BMP are managed by infiltration and an overflow weir. The overflow weir conveys
flows to DMA N1c.
• DMA N1c is 0.014-acres (0% impervious) and contains the western edge of Lot 3 and southern half of the western edge of Lot 2 (i.e. the 6-ft strip of landscaping with drainage swale above the
retaining wall). This DMA conveys runoff from DMAs N1a and N1b into the private storm drain system via the proposed riprap drainage swale which terminates at a catch basin.
• DMA N2a is 0.039-acres (19% impervious) and an area within the public right-of-way along
Highland Avenue that flows onto DMA N2b. DMA N2a consists of landscaping and the driveway for Lot 1 of Map 16234 that ties into Highland Avenue.
• DMA N2b is 0.274-acres (30% impervious) and contains proposed Lot 1 of Map 16234. DMA N2b accepts run-on from DMA N2a. Runoff discharges into a Bioretention BMP for pollutant control.
Flows leaving the BMP are managed by infiltration and an overflow weir. The overflow weir conveys flows DMA N2c.
• DMA N2c is 0.011-acres (0% impervious) and contains the western edge of Lot 1 and northern half
of the western edge of Lot 2 (i.e. the 6-ft strip of landscaping with drainage swale above the retaining wall). This DMA conveys runoff from DMAs N2a and N2b into the private storm drain
system via the proposed riprap drainage swale which terminates at a catch basin.
• DMA N3 is 0.082-acres (62% impervious) contains the southern half of Lot 3, and the drainage easement and storm drain infrastructure that coveys flows from Lot 4 and the southern half of Lot 3
along its southern perimeter prior to bending north into DMA N4 and discharging the City MS4.
• DMA N4 is 0.082-acres (50% impervious) contains the northern half of Lot 3, and a swale and storm
drain that coveys runoff along its northern edge prior to bending south and discharging into the City MS4. There is also a drainage easement along the eastern perimeter of DMA N4 that accepts flows
from Lots 1, 2 and 5. DMA N4 contains the projects sole point of discharge as flows from the entire site (Lots 1-5) will combine within the onsite storm drain system and will be piped into the back of
the curb inlet on James Drive (which is part of the City MS4).
• DMA N5 is 0.082-acres (65% impervious) contains the southern half of Lot 2, and a swale and storm drain that coveys flows eastward along the southern edge of Lot 2 to the drainage easement
along the eastern edge of Lot 3.
• DMA N6 is 0.082-acres (50% impervious) contains the northern half of Lot 2 and a swale and storm drain that coveys flows eastward along the northern edge of Lot 2 to the drainage easement along
the eastern edge of Lot 3.
• DMA N7 is 0.082-acres (61% impervious) contains the southern half of Lot 1, and the drainage
easement and storm drain infrastructure that coveys flows eastward from Lot 5 and the southern half of Lot 1 along its southern perimeter prior to bending south and discharging into the drainage
easement along the eastern edge of Lots 2 and 3.
• DMA N8 is 0.082-acres (49% impervious) and contains the northern half of Lot 1 and a swale and storm drain that conveys runoff eastward along the northern edge of Lot 1 to bending south and
discharging into the drainage easement along the eastern edge of Lots 2 and 3. DMA N8 also contains a 12-inch public storm drain with a 5-ft easement along its northern perimeter that conveys
flows from Highland eastward through the site and into storm drain under James Drive (please note that the project does not contribute runoff to this pipeline).
Identify whether any of the following features, activities, and/or pollutant source areas will be
present (select all that apply)
Onsite storm drain inlets Interior floor drains and elevator shaft sump pumps
Interior parking garages Need for future indoor & structural pest control Landscape/outdoor pesticide use
Pools, spas, ponds, decorative fountains, and other water features Food service Refuse areas
Industrial processes Outdoor storage of equipment or materials
Vehicle and equipment cleaning
Vehicle/equipment repair and maintenance Fuel dispensing areas
Loading docks
Fire sprinkler test water Miscellaneous drain or wash water
Plazas, sidewalks, and parking lots
Identification of Receiving Water Pollutants of Concern
Describe path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable):
In existing conditions the site does not contain any storm drain infrastructure for stormwater generated onsite, and topography dictates that runoff sheet flows along the ground surface
from west to east and discharges offsite and onto James Drive along the sites eastern edge.
The proposed storm will replace sheet flow with a combination of sheet, channel and pipe flows; however the point of discharge along the sites eastern edge will remain the same.
Once the runoff discharges onto James Drive it is collected by a curb inlet on which is part of the municipal separate storm sewer system (MS4) owned and operated by the City of Carlsbad.
The City MS4 conveys the runoff further downstream to the Agua Hedionda Lagoon with ultimate discharge into the Pacific Ocean along Carlsbad State Beach (at Tamarack jetties and at the discharge for the Encina Power Station).
Although there are not any 303(d) impaired water bodies within the path of stormwater from the site to the Pacific Ocean, the following pollutant(s)/stressor(s) and associated TMDLs, are listed
for the Agua Hedionda Creek which also discharges to the Agua Hedionda Lagoon.
303(d) Impaired Water Body Pollutant(s)/Stressor(s) TMDLs
Agua Hedionda Creek Enterococcus 2019
Agua Hedionda Creek Fecal Coliform 2019
Agua Hedionda Creek Manganese 2019
Agua Hedionda Creek Phosphorus 2019
Agua Hedionda Creek Selenium 2019
Agua Hedionda Creek Total Dissolved Solids 2019
Agua Hedionda Creek Total Nitrogen as N 2019
Agua Hedionda Creek Toxicity 2019
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Identification of Project Site Pollutants
Identify pollutants expected from the project site based on all proposed use(s) of the site (see
manual Appendix B.6):
Pollutant Not Applicable to
the Project Site
Expected from the
Project Site
Also a Receiving
Water Pollutant of Concern
Sediment X X
Nutrients X X
Heavy Metals X X
Organic
Compounds X X
Trash & Debris X
Oxygen Demanding
Substances X
Oil & Grease X
Bacteria & Viruses X X
Pesticides X
Toxicity X X
Hydromodification Management Requirements
Do hydromodification management requirements apply (see Section 1.6 of the BMP Design Manual)?
Yes, hydromodification management flow control structural BMPs required.
No, the project will discharge runoff directly to existing underground storm drains
discharging directly to water storage reservoirs, lakes, enclosed embayments, or the Pacific Ocean.
No, the project will discharge runoff directly to conveyance channels whose bed and bank
are concrete-lined all the way from the point of discharge to water storage reservoirs, lakes,
enclosed embayments, or the Pacific Ocean. No, the project will discharge runoff directly to an area identified as appropriate for an
exemption by the WMAA for the watershed in which the project resides.
Description / Additional Information (to be provided if a 'No' answer has been selected above):
According to the Hydromodification Exemption Analyses prepared by Chang Consultants
(September, 2015), the site is located within the hydromodification exempt area. Furthermore, maps included under Carlsbad Watershed Management Area Analysis (WMAA) Attachment B.2
indicate that the receiving public storm drain is also an exempt conveyance system. For further details, please refer to Attachment 2a of the SWQMP.
Critical Coarse Sediment Yield Areas* *This Section only required if hydromodification management requirements apply
Based on the maps provided within the WMAA, do potential critical coarse sediment yield areas
exist within the project drainage boundaries?
Yes
No, No critical coarse sediment yield areas to be protected based on WMAA maps
If yes, have any of the optional analyses presented in Section 6.2 of the BMP Design Manual been performed?
6.2.1 Verification of Geomorphic Landscape Units (GLUs) Onsite
6.2.2 Downstream Systems Sensitivity to Coarse Sediment
6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite
No optional analyses performed, the project will avoid critical coarse sediment yield areas
identified based on WMAA maps
If optional analyses were performed, what is the final result?
No critical coarse sediment yield areas to be protected based on verification of GLUs onsite
Critical coarse sediment yield areas exist but additional analysis has determined that
protection is not required. Documentation attached in Attachment 8 of the SWQMP.
Critical coarse sediment yield areas exist and require protection. The project will implement
management measures described in Sections 6.2.4 and 6.2.5 as applicable, and the areas
are identified on the SWQMP Exhibit.
Discussion / Additional Information:
According to the Potential Critical Coarse Sediment Yield Areas Exhibit (Attachment A.4 of the Carlsbad WMAA) the site is not located within an area known as a potentially critical source of
coarse sediment yield. For further details, please refer to SWQMP Attachment 2b.
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Flow Control for Post-Project Runoff*
*This Section only required if hydromodification management requirements apply
List and describe point(s) of compliance (POCs) for flow control for hydromodification
management (see Section 6.3.1). For each POC, provide a POC identification name or number correlating to the project's HMP Exhibit and a receiving channel identification name or number
correlating to the project's HMP Exhibit. N/A – according to the Hydromodification Exemption Analyses for select Carlsbad Watersheds
prepared by Chang Consultants (September, 2015), the site is located in a hydromodification
exempt area and is therefore exempt from the City’s hydromodification requirements.
Nevertheless, in post-development conditions the site will be subdivided into 8 Drainage Management Areas (DMAs) with one (1) points where stormwater exits the site at its only point of discharge into the curb inlet on James Drive (which is part of the City MS4) located along the
eastern edge of the subject property. Please refer to the Description of Proposed Site Development and Drainage Patterns Section of this SWQMP (above) for further information
regarding the 8 proposed DMAs.
Has a geomorphic assessment been performed for the receiving channel(s)?
No, the low flow threshold is 0.1Q2 (default low flow threshold)
Yes, the result is the low flow threshold is 0.1Q2
Yes, the result is the low flow threshold is 0.3Q2
Yes, the result is the low flow threshold is 0.5Q2
N/A, the site is exempt from the City’s hydromodification requirements.
If a geomorphic assessment has been performed, provide title, date, and preparer:
Discussion / Additional Information: (optional)
N/A – according to the Hydromodification Exemption Analyses for select Carlsbad Watersheds
prepared by Chang Consultants (September, 2015), the site is located in a hydromodification
exempt area and is therefore exempt from the City’s hydromodification requirements. For further details, please refer to Hydromodification Management Exhibit and the Hydromodification
Management Exemption Map included under Attachment 2a of the SWQMP.
□ □ □ □ cg]
Other Site Requirements and Constraints
When applicable, list other site requirements or constraints that will influence storm water management design, such as zoning requirements including setbacks and open space, or City
codes governing minimum street width, sidewalk construction, allowable pavement types, and drainage requirements.
Site constraints include the surrounding topography, multiple private drainage easements
throughout the site, existing 12-inch public storm drain (and easement) along the site’s northern
perimeter, the proposed property lines associated with the lot split, and changes in elevation from east-to-west across the site.
Optional Additional Information or Continuation of Previous Sections As Needed
This space provided for additional information or continuation of information from previous
sections as needed.
Although the site is challenged with the aforementioned constraints, it has fairly well draining soils
and the drainage easements may be more of a benefit then a constraint allowing for cross property drainage. The site has been designed to maximize the use of site design BMPs, such
that 6 of the 8 proposed DMAs may be considered Self-Retaining DMAs via Qualifying Site
Design BMPs. Structural BMPs (i.e. two bioretention basins) have been designed for the 2 DMAs that could not be treated solely with site design BMPs. The specific BMPs for the subject
development are Tree Wells (BMP SD-1), Impervious Area Dispersion (BMP SD-5), and
Biofiltration with partial retention (BMP PR-1) and they have been engineered in accordance with the City of Carlsbad BMP Design Manual (02/16/16).
E-36 Page 1 of 3 REV 02/16
Development Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
STANDARD PROJECT
REQUIREMENT
CHECKLIST
E-36
Project Information
Project Name:
Project ID:
DWG No. or Building Permit No.:
Source Control BMPs
All development projects must implement source control BMPs SC-1 through SC-6 where applicable and feasible.
See Chapter 4 and Appendix E.1 of the BMP Design Manual for information to implement source control BMPs
shown in this checklist.
Answer each category below pursuant to the following.
"Yes" means the project will implement the source control BMP as described in Chapter 4 and/or Appendix E.1
of the Model BMP Design Manual. Discussion/justification is not required.
"No" means the BMP is applicable to the project but it is not feasible to implement. Discussion/justification must
be provided.
"N/A" means the BMP is not applicable at the project site because the project does not include the feature that is
addressed by the BMP (e.g., the project has no outdoor materials storage areas). Discussion/justification may be
provided.
Source Control Requirement Applied?
SC-1 Prevention of Illicit Discharges into the MS4 Yes No N/A
Discussion/justification if SC-1 not implemented:
SC-2 Storm Drain Stenciling or Signage Yes No N/A
Discussion/justification if SC-2 not implemented:
SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On,
Runoff, and Wind Dispersal
Yes No N/A
Discussion/justification if SC-3 not implemented:
SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On,
Runoff, and Wind Dispersal
Yes No N/A
Discussion/justification if SC-4 not implemented:
SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind
Dispersal
Yes No N/A
Discussion/justification if SC-5 not implemented:
Highland-James Subdivision
x
x
x
There are not any proposed outdoor material storage areas associated with the subject
redevelopment
x
There are not any proposed outdoor work areas associated with the subject redevelopment
x
Trash will be stored within sealed containers issued by Waste Management, Inc. as is standard
throughout the City, with separate containers for trash, recyclables and green waste. Trash will
be stored such that it cannot come into direct contact with rainfall or stormwater flows.
CDP 15-47, 15-48 & 15-49, 2017-0024, 2017-0025
483-6B & 483-6C, 483-6D
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E-36 Page 2 of 3 REV. 02/16
Source Control Requirement Applied?
SC-6 Additional BMPs based on Potential Sources of Runoff Pollutants must
answer for each source listed below and identify additional BMPs. (See
Table in Appendix E.1 of BMP Manual for guidance).
On-site storm drain inlets
Interior floor drains and elevator shaft sump pumps
Interior parking garages
Need for future indoor & structural pest control
Landscape/Outdoor Pesticide Use
Pools, spas, ponds, decorative fountains, and other water features
Food service
Refuse areas
Industrial processes
Outdoor storage of equipment or materials
Vehicle and Equipment Cleaning
Vehicle/Equipment Repair and Maintenance
Fuel Dispensing Areas
Loading Docks
Fire Sprinkler Test Water
Miscellaneous Drain or Wash Water
Plazas, sidewalks, and parking lots
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
For “Yes” answers, identify the additional BMP per Appendix E.1. Provide justification for “No” answers.
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
The potential sources checked N/A above are considered not applicable because the
project does not include the feature or corresponding BMP. Onsite inlets will be
stenciled or stamped to discourage dumping and inform people that they drain to the
Ocean. Trash and refuse containers shall be sealed and water tight and it is
recommended that they be stored in such a manner that the refuse cannot come into
direct contact with rainfall or stormwater run-on/runoff. Potential sources checked No
are not applicable to small residential development (i.e. residents in Carlsbad are
allowed to clean and repair there vehicles on their property without installing a
commercial car wash or an auto repair shop, residents may encounter miscellaneous drain
or wash water at times, and the public sidewalk constructed as part of the project will
be built per City standards and will more than likely be dedicated to the City upon
completion). Furthermore, the grading/drainage has been designed such that any non-
stormwater generated onsite not addressed by the aforementioned Source Control BMPs
will drain to the proposed site design and/or structural LID BMPs to improve water
quality prior to offsite discharge.
x
x
x
x
x
xx
x
E-36 Page 3 of 3 REV. 02/16
Site Design BMPs
All development projects must implement site design BMPs SD-1 through SD-8 where applicable and feasible. See
Chapter 4 and Appendix E.2 thru E.6 of the BMP Design Manual for information to implement site design BMPs
shown in this checklist.
Answer each category below pursuant to the following.
"Yes" means the project will implement the site design BMPs as described in Chapter 4 and/or Appendix E.2
thru E.6 of the Model BMP Design Manual. Discussion / justification is not required.
"No" means the BMPs is applicable to the project but it is not feasible to implement. Discussion/justification must
be provided.
"N/A" means the BMPs is not applicable at the project site because the project does not include the feature that
is addressed by the BMPs (e.g., the project site has no existing natural areas to conserve).
Discussion/justification may be provided.
Site Design Requirement Applied?
SD-1 Maintain Natural Drainage Pathways and Hydrologic Features Yes No N/A
Discussion/justification if SD-1 not implemented:
SD-2 Conserve Natural Areas, Soils, and Vegetation Yes No N/A
Discussion/justification if SD-2 not implemented:
SD-3 Minimize Impervious Area Yes No N/A
Discussion/justification if SD-3 not implemented:
SD-4 Minimize Soil Compaction Yes No N/A
Discussion/justification if SD-4 not implemented:
SD-5 Impervious Area Dispersion Yes No N/A
Discussion/justification if SD-5 not implemented:
SD-6 Runoff Collection Yes No N/A
Discussion/justification if SD-6 not implemented:
SD-7 Landscaping with Native or Drought Tolerant Species Yes No N/A
Discussion/justification if SD-7 not implemented:
SD-8 Harvesting and Using Precipitation Yes No N/A
Discussion/justification if SD-8 not implemented:
x
Although grading will alter the topogrpahy, the site will still be characterized by surface flow
in a west-to-east direction and the single discharge point located at the sites southeast corner
will remain unchanged.
x
The proposed site plan requires grading throughout the site, still efforts have been made to
conserve some vegetation, and the infiltration capabilities of the soils onsite.
x
Impervious areas have been minimized as much as practical for the subject development.
Furthermore the site has been designed to drain impervious surfaces to permeable areas to promote
onsite infiltration of stormwater runoff.
x
Soil compaction will be minimized except where necessary (i.e. building pads for the homes,
trenches for utilities,construction of driveways, sidewalks, patios, etc.)
x
The site has been designed such that impervious surfaces drain to permeable areas to promote onsite
infiltration of stormwater prior to offsite discharge.
x
Runoff will be collected in bioretention basins and permeable vegetated swales to convey the
flows and promote onsite infiltration of stormwater.
x
The proposed landscaping will utilize native and/or drought tolerant species in accordance with
City standards.
x
Water quality requirements are met with Bioretention Basins and Self-Retaining DMAs via
Qualifying Site Design BMPs. Precipitation Harvest/Re-Use is not included as part of project,
but future home Owners could install catchments/cisterns on their own properties as they see fit.
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SUMMARY OF PDP STRUCTURAL BMPS
PDP Structural BMPs
All PDPs must implement structural BMPs for storm water pollutant control (see Chapter 5 of the BMP Design Manual). Selection of PDP structural BMPs for storm water pollutant control must be based on the selection
process described in Chapter 5. PDPs subject to hydromodification management requirements must also
implement structural BMPs for flow control for hydromodification management (see Chapter 6 of the BMP Design Manual). Both storm water pollutant control and flow control for hydromodification management can
be achieved within the same structural BMP(s). PDP structural BMPs must be verified by the City at the completion of construction. This may include requiring
the project owner or project owner's representative to certify construction of the structural BMPs (see Section 1.12 of the BMP Design Manual). PDP structural BMPs must be maintained into perpetuity and the City must
confirm the maintenance (see Section 7 of the BMP Design Manual).
Use this form to provide narrative description of the general strategy for structural BMP implementation at the
project site in the box below. Then complete the PDP structural BMP summary information sheet for each
structural BMP within the project (copy the BMP summary information page as many times as needed to provide summary information for each BMP).
Describe the general strategy for structural BMP implementation at the site. This information must describe how the steps for selecting and designing storm water pollutant control BMPs presented in Section 5.1 of the
BMP Design Manual were followed, and the results (type of BMPs selected). For projects requiring
hydromodification flow control BMPs, indicate whether pollutant control and flow control BMPs are integrated together or separate.
Since the site is exempt from the City’s hydromodification requirements, this evaluation was performed to address pollutant control BMPs only. First the site was evaluated at DMA scale to determine if portions of the
project could be considered “self-mitigating”, “de minimis” or “self-retaining”. The site was subdivided into 12
DMAs to convey runoff through the property with the intent that each DMA could be a Self-Retaining DMA via Qualifying Site Design BMPs. The grading and drainage of each DMA was designed to disperse runoff from
impervious areas to permeable areas to promote infiltration onsite (i.e. BMP SD-5: Impervious Area Dispersion). Review of the site-specific Soils Report generated on the USDA NRCS Web Soil Survey the entire site is underlain with Hydrologic Soil Group B. The impervious:pervious ratio required for compliance
with BMP SD-5 is less than or equal to one (1) in these types of soils.
Calculations (included under SWQMP Attachment 1e) determined the impervious:pervious ratios for each of the DMAs. The ratios for DMAs N1a, N1b, N1c, N2a, N2b, N2c, N4 and N8 are less than or equal to one so it
appears that these DMAs may be considered Self-Retaining DMAs via qualifying Site Design BMPs, and compliant with City requirements. It is however important to note that the majority of the receiving permeable
area for DMAs N1a, N1b, N2a, and N2b is sloped steeper than 5% and therefore is not eligible for impervious
area dispersion (BMP SD-5). Therefore additional stormwater measures (i.e. Biofiltration with partial retention Basins – PR-1) have been included in the design to treat the runoff from DMAs N1a, N1b, N2a, and N2b.
At this point in the analysis DMAs N1c, N2c, N4 and N8 are the only DMAs that may be considered as
Self-Retaining DMAs via qualifying Site Design BMPs via SD-5. Additional BMPs are needed for DMAs N1a, N1b, N2a, N2b, N3, N5, N6 and N7, so for these DMAs the required Design Capture Volume must be
calculated as the product of the C-value 85th percentile storm depth and the contributing drainage area. The
table below summarizes the calculations used to determine the DCV for each DMA and if each DMA could be treated by Impervious dispersion (BMP SD-5) alone:
DMA A A A,imp A,imp A,per A,per imp:perv C DCV WQ Compliant
sq-ft ac sq-ft ac sf ac Ratio cu-ft ai/ap < 1?
N1a 1625 0.037 312 0.007 1313 0.030 0.238 0.25 20 No*
N1b 11917 0.274 3521 0.081 8396 0.193 0.419 0.34 197 No*
N1a + N1b 13542 0.311 3833 0.088 9709 0.223 0.395 0.33 217 No*
N1c 605 0.014 0 0.000 605 0.014 0.000 0.10 3 Yes
N2a 1678 0.039 324 0.007 1354 0.031 0.239 0.25 21 No*
N2b 11917 0.274 3582 0.082 8335 0.191 0.430 0.34 199 No*
N2a + N2b 13595 0.312 3906 0.090 9689 0.222 0.403 0.33 220 No*
N2c 484 0.011 0 0.00 484 0.01 0.000 0.10 2 Yes
N3 3571 0.082 2202 0.05 1369 0.03 1.608 0.59 104 No
N4 3571 0.082 1782 0.04 1789 0.04 0.996 0.50 88 Yes
N5 3571 0.082 2309 0.05 1262 0.03 1.830 0.62 108 No
N6 3571 0.082 1798 0.04 1773 0.04 1.014 0.50 88 No
N7 3571 0.082 2172 0.05 1399 0.03 1.553 0.59 103 No
N8 3571 0.082 1765 0.04 1806 0.04 0.977 0.50 87 Yes
TOTAL 49652 1.14 19767 0.45 29885 0.69 0.661 0.42 1022
* = DMAs N1a, N1b, N2a and N2b meet the BMP SD-5 water quality requirement in terms of imp:perv ratio,
however the DCV reduction associated with BMP SD-5 has not been counted because a significant portion of the
receiving permeable area is sloped greater than 5%.
As noted in the table above the impervious:pervious ratios for DMAs N3, N5, N6 and N7 are larger than one
(1), and the receiving pervious area for DMAs N1a, N1b, N2a and N2c is steeper than 5%, so therefore these DMAs require additional BMPs for compliance. For these DMAs, the Runoff Factor (C) was calculated and
then adjusted by accounting for the effects of BMP SD-5 in accordance with City BMP Design Manual Section
5.3 and Appendix B.2. Next the Design Capture Volume (DCV) was re-calculated using the adjusted C factor. The adjusted C-values and DCVs for the DMAs requiring additional BMPs are provided in the table, below:
DMA C-Value DCV Adjustment Factor Adjusted C-Value Adjusted DCV # unitless cu-ft unitless unitless cu-ft
N1a + N1b 0.33 217 N/A 217
N1c 0.10 3 N/A 3
N2a + N2b 0.33 220 N/A 220
N2c 0.10 2 N/A 2
N3 0.59 104 0.16 0.13 23
N4 0.50 88 N/A 88
N5 0.62 108 0.22 0.17 29
N6 0.50 88 0.00 0.05 9
N7 0.59 103 0.15 0.12 21
N8 0.50 87 N/A 87
TOTAL DCV = 1115 TOTAL ADJUSTED DCV = 793
The City of Carlsbad allows up to 25% of total DCV to be treated by Tree Wells (BMP SD-1), and Tree Credit
Volumes may be issued at 10 cu-ft and 40 cu-ft for trees with canopies reaching 5-ft and 10-ft, respectively at
maturity. Tree Wells have been strategically located into the site landscaping and drainage plans to receive runoff from impervious surfaces, and treat the remainder DCV from DMAs N3, and N5-N8 as follows:
DMA Adjusted DCV Trees (d = 5 ft) TCV (d = 5 ft) Trees (d = 10 ft) TCV (d = 10 ft) Total TCV Adj. DCV (via SD-6) WQ Compliant? Struct. BMP needed?
# cu-ft # cu-ft/tree # cu-ft/tree cu-ft cu-ft Yes/No
N1a + N1b 217 Yes
N1c 3 No
N2a + N2b 220 Yes
N2c 2 No
N3 23 1 40 40 -17 Yes No
N4 88 No
N5 29 1 40 40 -11 Yes No
N6 9 1 10 10 -1 Yes No
N7 21 1 40 40 -19 Yes No
N8 87 No
Total TCV = 130
The City of Carlsbad BMP Design Manual allows for a Tree Credit Volume (TCV) up to up to 25% of the DCV
for the project, and as noted in the table above the project has a TCV equal to 130 cu-ft. It is not clear whether
the TCV is to be applied to the original DCV or the Adjusted DCV, so the project has been designed in compliance with both as follows:
Compliance Check for Project TCV (equal to 130 cu-ft): TCV must be less than 25% of DCV 0.25*DCV = 0.25 * 1,115 cu-ft = 279 cu-ft TCV = 130 cu-ft < 0.25*DCV = 279 cu-ft OK
TCV must be less than 25% of Adjusted DCV 0.25*Adjusted DCV = (0.25) * 793 cu-ft = 198 cu-ft TCV = 130 cu-ft < 0.25*Adjusted DCV = 198 cu-ft OK
As noted in the table above structural BMPs are still required for DMAs N1a, N1b, N2a and N2b. Also noted in
the summary table at the top of this section the DCV reduction associated with BMP SD-5 has not been counted for DMAs N1a, N1b, N2a and N2b. because a significant portion of the receiving permeable area is
sloped greater than 5%. So, two (2) Biofiltration with Partial Retention Basins (BMP PR-1) have been incorporated into the grading and drainage design to treat the runoff from N1a, N1b, and from N2a and N2b, respectively. Soils onsite are classified as Hydrologic Soil Type B and percolation testing indicates that they
infiltrate at 0.125 in/hr. Given these conditions, the 2 proposed Biofiltration with Partial Retention Basins have been designed in accordance with the requirements for Biofiltration with Partial Retention Basins (BMP PR-1)
as detailed in the Structural BMP Summary Information Section of this SWQMP (below) and the calculations
included under SWQMP Attachment 1e.
In summary, 2 Biofiltration with Partial Retention Basins (BMP PR-1a and PR-2b) have been designed to treat
runoff from the remaining DMAs (N1a/N1b and N2a/N2b) that could not be treated via qualifying Site Design BMPs. Impervious Area Dispersion (BMP SD-5) alone is sufficient for treating DMAs N1c, N2c, N4 & N8 and
a combination of Impervious Area Dispersion (BMP SD-5) and Tree Wells (BMP SD-1) was used to treat
DMAs N3, N5, N6 and N7. So, in total 8 out of the 12 proposed DMAs (DMAs N1c, N2c, & N3 – N8) may be
considered Self-Retaining DMAs via Qualifying Site Design BMPs, while the other 4 DMAs (DMAs N1a, N1b,
N2a and N2b) are treated with structural BMPs (i.e. 2 Biofiltration with Partial Retention Basins, 1 for DMAs N1a & N1b and the other for N2a & N2b). This proposed combination of site design and structural BMPs has
been engineered to adequately address post-development stormwater runoff from all 12 proposed DMAs in compliance with the City of Carlsbad water quality requirements as detailed in the BMP summary information below and in the LID BMP calculations included under SWQMP Attachment 1e.
Structural BMP Summary Information
Structural BMP ID No. PR-1a (for DMA N1a and N1b)
DWG _483-6D__ Sheet No. __3________
Type of structural BMP: Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1)
Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP
(provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in
discussion section below)
Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Discussion (as needed): The site is exempt from hydromodification requirements and a Biofiltration with Partial Retention Basin (BMP
PR-1a) has been designed solely to address DMAs N1a and N1b for water quality purposes. The treatment will
be achieved as stormwater is filtered vertically through amended soils prior to infiltrating into native soils onsite.
DMA N1a combines with DMA N1b on Lot 2 of Map 16234 and flows through the drainage easements on Lot 3 before discharging into the City MS4 along the sites eastern perimeter. The total area within DMAs N1a and N1b is 13,542 sq-ft (28% impervious), and it has been designed such that all of the proposed permeable areas
and impervious surfaces (i.e. house, sidewalks, and driveway) will drain to the Biofiltration with Partial Retention Basin (BMP PR-1a) to promote onsite infiltration.
The entire site is underlain by Hydrologic Soil Group B and Biofiltration with Partial Retention BMPs are an appropriate measure for treating stormwater runoff. Design calculations for BMP PR-1a are included under
SWQMP Attachment 1e, and a summary is provided below:
Worksheet B.2-1. DCV for DMAs N1a and N1b
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.31 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.33 unitless
4 Tree wells volume reduction TCV= 0 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = 217.35 cubic-feet
□ □ □ □ l:8J □ □
□ □
l:8J □ □ □ □
The receiving permeable area is steeper than 5% and cannot be utilized for BMP SD-5, so there is not any
C-value reduction for DMAs N1a and N1b. Furthermore, although the landscaping plans call out several
trees within the area, Tree Wells (BMP SD-1) have not been incorporated as measure for addressing the
DCV from these DMAs. As a result the DCV for DMAs N1a and N1b has been determined to equal 271.64
cu-ft. A Biofiltration with Partial Retention Basin (PR-1a) has been designed for DMA N1a and N1b with a
retention capacity of 107 cu-ft which is more than adequate for treating 37.5% of the DCV of 217 cu-ft -->
107 cu-ft > (0.375 * 217 cu-ft) = 81.4 cu-ft --> OK
A Biofiltration with Partial Retention Basin (PR-1a) was sized with sufficient capacity for addressing the DCV. The Biofiltration with Partial Retention Basin includes a 6-inch ponding depth, 18-inches of amended soils and
12-inches of gravel on top of native soils with a surface area of 318 sq-ft, bottom area of 77 sq-ft and 3:1 side
slopes, as detailed in the table below:
DMA A,BMP A,
req
Inf.
Rate
Inf.
Depth A,bot h,pond h,am h,gr V,BMP
(retained) V,BMP
(retained)
> 0.375
DCV?
Sf sf in/hr In sf ft ft ft cu-ft Fraction
of DCV Water Quality
Compliant?
N1a & N1b 318 133 0.063 2.25 77 0.50 1.50 1.0 107 0.494 YES
The gravel, amended soil and ponding layers of the BMP combined retain 107 cubic-feet of volume (i.e. volume retained = 107 cu-ft > 0.375 * DCV = 0.375 *217 cu-ft = 81.4 cu-ft OK). Biofiltration BMPs require
an area of 3% of the DMA accounting for the C-value (i.e. 13,542 sq-ft * 0.33 * 0.03 = 133 sq-ft). As noted
PR-1a provides 318 sq-ft which is larger than the area required (133 sq-ft), and therefore in compliance with City requirements (i.e. area provided = 318 sq-ft > area required = 133 sq-ft OK). Drawdown calculation
were performed using the Simple Sizing Method of Biofiltration BMPs as follows:
Worksheet B.5-1: Simple Sizing Method for Biofiltration BMPs
Simple Sizing Method for Biofiltration BMPs
BMP ID IDs of Tributary DMAs IDs of Retention BMPs Treating the Same DMAs
PR-1a DMAs N1a & N1b N/A
Initial Information
1a Total DCV of tributary DMAs 217 ft3
1b Volume reduction from implementation of retention BMPs 0 ft3
1 Remaining DCV after implementing retention BMPs (Line 1a - Line 1b) 217 ft3
Partial Retention
2 Infiltration rate from Worksheet D.5-1 if partial infiltration is feasible 0.063 in/hr
3 Allowable drawdown time for aggregate storage below the underdrain 36 hr
4 Depth of runoff that can be infiltrated [Line 2 x Line 3] 2.25 in
5 Aggregate pore space 0.4 in/in
6 Required depth of gravel below the underdrain [Line 4/ Line 5] 5.63 in
7 Assumed surface area of the biofiltration BMP 318 ft2
8 Media retained pore storage 0.1 in/in
9 Volume retained by BMP [[[Line 4 + (Line 12 x Line 8)]/12] x Line 7] 107 ft3
10 DCV that requires biofiltration [Line 1 – Line 9] 110 ft3
BMP Parameters
11 Surface Ponding [6 inch minimum, 12 inch maximum] 6 in
12
Soil Media Thickness [18 inches minimum], also add mulch layer thickness
to this line for sizing calculations 18 in
13 Aggregate Storage above underdrain invert 6 in
14 Soil Media available pore space 0.2 in/in
15
Soil Media filtration rate to be used for sizing (5 in/hr. with no outlet
control; if the filtration rate is controlled by the outlet use the outlet
controlled rate) 5 in/hr.
Baseline Calculations
16 Allowable Routing Time for sizing 6 hr
17 Depth filtered during storm [ Line 15 x Line 16] 30 in
18
Depth of Detention Storage
[Line 11 + (Line 12 x Line 14) + (Line 13 x Line 5)] 12 in
19 Total Depth Treated [Line 17 + Line 18] 42 in
Option 1 – Biofilter 1.5 times the DCV
20 Required biofiltered volume [1.5 x Line 10] 165 ft3
21 Required Footprint [Line 20/ Line 19] x 12 47 ft2
Option 2 - Store 0.75 of remaining DCV in pores and ponding
22 Required Storage (surface + pores) Volume [0.75 x Line 10] 239 ft3
23 Required Footprint [Line 22/ Line 18] x 12 239 ft2
Footprint of the BMP
24 Area draining to the BMP 13542 ft2
25 Adjusted Runoff Factor for drainage area (Refer to Appendix B.1 and B.2) 0.33
26
BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum
footprint sizing factor from Worksheet B.5-2, Line 11)
0.03
unitless
27 Minimum BMP Footprint [Line 24 x Line 25 x Line 26] 133 ft2
28 Footprint of the BMP = Maximum(Minimum(Line 21, Line 23), Line 27) 133 ft2
29 Calculate the fraction of the DCV retained by the BMP [Line 9/ Line 1] 0.494 unitless
30 Minimum required fraction of DCV retained for partial infiltration condition 0.375 unitless
31
Is the retained DCV > 0.375? If the answer is no increase the footprint sizing
factor in Line 26 until the answer is yes for this criterion Yes ☐ No
Notes
1. Line 7 is used to estimate the amount of volume retained by the BMP. Update assumed surface area in Line 7 until its
equivalent to the required biofiltration footprint (either Line 21 or Line 23)
2. The DCV fraction of 0.375 is based on a 40% average annual percent capture and a 36-hour drawdown time.
3. The increase in footprint for volume reduction can be optimized using the approach presented in Appendix B.5.2. The
optimized footprint cannot be smaller than the alternative minimum footprint sizing factor from Worksheet B.5-2.
4. If the proposed biofiltration BMP footprint is smaller than the alternative minimum footprint sizing factor from Worksheet
B.5-2, but satisfies Option 1 or Option 2 sizing, it is considered a compact biofiltration BMP and may be allowed at the
discretion of the [City Engineer], if it meets the requirements in Appendix F.
In summary by incorporating Biofiltration with Partial Retention Basin (PR-1a) into the site plan, DMAs N1a and N1b have been designed in compliance with City water quality requirements. For further details, please refer to
the BMP Design Calculations included under Attachment 1e of this SWQMP.
Structural BMP Summary Information
Structural BMP ID No. SMA-1 (for DMA N1c)
DWG __483-6B_ Sheet No. _4 & 5_____
Type of structural BMP: Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2) Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1) Biofiltration (BF-1) Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration
BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below) Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only Hydromodification control only Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and the self-mitigating area (SMA-1) has been designed solely to address DMA N1c for water quality purposes. The treatment will be achieved through
infiltration of stormwater onsite.
DMA N1c is 0.014-acres along the western edge of Lot 3 and the southern portion of the western edge of Lot
2 and contains a drainage swale for conveying overflows from Lot 4 (i.e. flows from storms larger than the
85th percentile event) through Lot 3. DMA N1c will be vegetated and will not contain any impermeable surfaces (i.e. 100% pervious). In order to comply with the City’s Self-Mitigating Area requirements the
incidental impervious areas must be less than 5% of the total DMA.
Compliance Check for SMA-1 (impervious area < 5% of DMA):
impervious area = 0 0 < 5% OK SMA-1 as designed is compliant.
Worksheet B.2-1. DCV for DMA N1c
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.01 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.10 unitless
4 Tree wells volume reduction TCV= 0 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = 2.97 cubic-feet
□ □ □ □ □ □ □
□ ~
Please note that SMA-1 has been designed in compliance with City water quality requirements as a Self-
Mitigating DMA. Compliance Check for SMA-1 (imperv. area must be < 5%): imperv. area = 0 --> 0 < 5% --> OK
In summary, SMA-1 has been designed in compliance with City water quality requirements as a
Self-Mitigating DMA because it is completely permeable. For further details, please refer to the BMP Design
Calculations included under Attachment 1e of this SWQMP.
Structural BMP Summary Information
Structural BMP ID No. PR-1b (for DMAs N2a and N2b)
DWG _483-6D__ Sheet No. __4________
Type of structural BMP:
Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1)
Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP
(provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in
discussion section below)
Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only
Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and a Biofiltration with Partial Retention Basin (PR-1b)
has been designed solely to address DMAs N2a and N2b for water quality purposes. The treatment will be achieved as stormwater is filtered vertically through amended soils prior to infiltrating into native soils onsite.
DMA N2a combines with DMA N2b on Lot 1 of Map 16234 and flows through the drainage easement on the southern edge of Lot 1 of Map 15082 before discharging to the City MS4, via the drainage easement along the
eastern edge of Lots 2 and 3 of Map 15082. The total area within DMAs N2a and N2b is 13,595 sq-ft (29%
impervious), and it has been designed such that all of the proposed permeable areas and impervious surfaces (i.e. home, sidewalks, and driveway) will drain to the Biofiltration with Partial Retention Basin (PR-1b) to
promote onsite infiltration. The entire site is underlain by Hydrologic Soil Group B and Biofiltration with Partial Retention BMPs are an
appropriate measure for treating stormwater runoff. Design calculations for BMP PR-1b are included under SWQMP Attachment 1e, and a summary is provided below:
Worksheet B.2-1. DCV for DMAs N2a and N2b
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.31 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.33 unitless
4 Tree wells volume reduction TCV= 0 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = 220.48 cubic-feet
□ □ □ □ cg]
□ □
□ □
cg]
□ □ □ □
The receiving permeable area is steeper than 5% and cannot be utilized for BMP SD-5, so there is not any
C-value reduction for DMAs N2a and N2b. Furthermore, although the landscaping plans call out several trees
within the area, Tree Wells (BMP SD-1) have not been incorporated as measure for addressing the DCV from
these DMAs. As a result the DCV for DMAs N2a and N2b has been determined to equal 220.48 cu-ft. A
Biofiltration with Partial Retention Basin (PR-2a) has been designed for DMA N2a and N2b with a retention
capacity of 100 cu-ft which is more than adequate for treating 37.5% of the DCV =of 260 cu-ft --> 100 cu-ft >
(0.375 * 260 cu-ft) = 97.4 cu-ft --> OK
A Biofiltration with Partial Retention Basin (PR-1b) was sized with sufficient capacity for addressing the DCV. The Bioretention Basin includes a 6-inch ponding depth, 18-inches of amended soils and 12-inches of gravel
on top of native soils with a surface area of 297 sq-ft, bottom area of 72 sq-ft and 3:1 side slopes, as detailed in
the table, below:
DMA A,BMP A,
req
Inf.
Rate
Inf.
Depth A,bot h,pond h,am h,gr V,BMP
(retained) V,BMP
(retained)
> 0.375
DCV?
Sf sf in/hr In sf ft ft ft cu-ft Fraction
of DCV Water Quality
Compliant?
N2a & N2b 297 135 0.063 2.25 72 0.50 1.50 1.0 100 0.455 YES
The gravel, amended soil and ponding layers of the BMP combined retain 100 cubic-feet of volume (i.e. volume retained = 100 cu-ft > 0.375 * DCV = 0.375 *220 cu-ft = 82.5 cu-ft OK). Biofiltration BMPs require
an area of 3% of the DMA accounting for the C-value (i.e. 13,595 sq-ft * 0.33 * 0.03 = 135 sq-ft). As noted
PR-2a provides 297 sq-ft which is larger than the area required (135 sq-ft), and therefore in compliance with City requirements (i.e. area provided = 297 sq-ft > area required = 135 sq-ft OK). Drawdown calculation
were performed using the Simple Sizing Method of Biofiltration BMPs as follows:
Worksheet B.5-1: Simple Sizing Method for Biofiltration BMPs
Simple Sizing Method for Biofiltration BMPs
BMP ID IDs of Tributary DMAs IDs of Retention BMPs Treating the Same DMAs
PR-1b DMAs N2a & N2b N/A
Initial Information
1a Total DCV of tributary DMAs 220 ft3
1b Volume reduction from implementation of retention BMPs 0 ft3
1 Remaining DCV after implementing retention BMPs (Line 1a - Line 1b) 220 ft3
Partial Retention
2 Infiltration rate from Worksheet D.5-1 if partial infiltration is feasible 0.063 in/hr
3 Allowable drawdown time for aggregate storage below the underdrain 36 hr
4 Depth of runoff that can be infiltrated [Line 2 x Line 3] 2.25 in
5 Aggregate pore space 0.4 in/in
6 Required depth of gravel below the underdrain [Line 4/ Line 5] 5.63 in
7 Assumed surface area of the biofiltration BMP 297 ft2
8 Media retained pore storage 0.1 in/in
9 Volume retained by BMP [[[Line 4 + (Line 12 x Line 8)]/12] x Line 7] 100 ft3
10 DCV that requires biofiltration [Line 1 – Line 9] 120 ft3
BMP Parameters
11 Surface Ponding [6 inch minimum, 12 inch maximum] 6 in
12
Soil Media Thickness [18 inches minimum], also add mulch layer
thickness to this line for sizing calculations 18 in
13 Aggregate Storage above underdrain invert 6 in
14 Soil Media available pore space 0.2 in/in
15
Soil Media filtration rate to be used for sizing (5 in/hr. with no outlet
control; if the filtration rate is controlled by the outlet use the outlet
controlled rate) 5 in/hr.
Baseline Calculations
16 Allowable Routing Time for sizing 6 hr
17 Depth filtered during storm [ Line 15 x Line 16] 30 in
18
Depth of Detention Storage
[Line 11 + (Line 12 x Line 14) + (Line 13 x Line 5)] 12 in
19 Total Depth Treated [Line 17 + Line 18] 42 in
Option 1 – Biofilter 1.5 times the DCV
20 Required biofiltered volume [1.5 x Line 10] 180 ft3
21 Required Footprint [Line 20/ Line 19] x 12 52 ft2
Option 2 - Store 0.75 of remaining DCV in pores and ponding
22 Required Storage (surface + pores) Volume [0.75 x Line 10] 223 ft3
23 Required Footprint [Line 22/ Line 18] x 12 223 ft2
Footprint of the BMP
24 Area draining to the BMP 13595 ft2
25
Adjusted Runoff Factor for drainage area (Refer to Appendix B.1 and
B.2)
0.33
26
BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum
footprint sizing factor from Worksheet B.5-2, Line 11)
0.03
unitless
27 Minimum BMP Footprint [Line 24 x Line 25 x Line 26] 135 ft2
28 Footprint of the BMP = Maximum(Minimum(Line 21, Line 23), Line 27) 135 ft2
29 Calculate the fraction of the DCV retained by the BMP [Line 9/ Line 1] 0.455 unitless
30
Minimum required fraction of DCV retained for partial infiltration
condition
0.375
unitless
31
Is the retained DCV > 0.375? If the answer is no increase the footprint
sizing factor in Line 26 until the answer is yes for this criterion Yes ☐ No
Notes
1. Line 7 is used to estimate the amount of volume retained by the BMP. Update assumed surface area in Line 7 until its
equivalent to the required biofiltration footprint (either Line 21 or Line 23)
2. The DCV fraction of 0.375 is based on a 40% average annual percent capture and a 36-hour drawdown time.
3. The increase in footprint for volume reduction can be optimized using the approach presented in Appendix B.5.2. The
optimized footprint cannot be smaller than the alternative minimum footprint sizing factor from Worksheet B.5-2.
4. If the proposed biofiltration BMP footprint is smaller than the alternative minimum footprint sizing factor from
Worksheet B.5-2, but satisfies Option 1 or Option 2 sizing, it is considered a compact biofiltration BMP and may be
allowed at the discretion of the [City Engineer], if it meets the requirements in Appendix F.
In summary by incorporating Biofiltration with Partial Retention Basin (PR-1b) into the site plan, DMAs N2a and
N2b have been designed in compliance with City water quality requirements. For further details, please refer to
the BMP Design Calculations included under Attachment 1e of this SWQMP.
Structural BMP Summary Information
Structural BMP ID No. SMA-2 (for DMA N2c)
DWG __483-6B_ Sheet No. _3_________
Type of structural BMP: Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2) Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1) Biofiltration (BF-1) Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration
BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below) Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only Hydromodification control only Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and the self-mitigating area (SMA-2) has been designed solely to address DMA N2c for water quality purposes. The treatment will be achieved through
infiltration of stormwater onsite.
DMA N2c is 0.011-acres along the western edge of Lot 1 and the northern portion of the western edge of Lot
2 and contains a drainage swale for conveying overflows from Lot 5 (i.e. flows from storms larger than the
85th percentile event) through Lot 1. DMA N2c will be vegetated and will not contain any impermeable surfaces (i.e. 100% pervious). In order to comply with the City’s Self-Mitigating Area requirements the
incidental impervious areas must be less than 5% of the total DMA.
Compliance Check for SMA-2 (impervious area < 5% of DMA):
impervious area = 0 0 < 5% OK SMA-2 as designed is compliant.
Worksheet B.2-1. DCV for DMA N2c
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.01 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.10 unitless
4 Tree wells volume reduction TCV= 0 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = 2.38 cubic-feet
□ □ □ □ □ □ □
□ ~
Please note that SMA-2 has been designed in compliance with City water quality requirements as a Self-
Mitigating DMA. Compliance Check for SMA-2 (imperv. area must be < 5%): imperv. area = 0 --> 0 < 5% --> OK
In summary, SMA-2 has been designed in compliance with City water quality requirements as a Self-Mitigating DMA because it is completely permeable. For further details, please refer to the BMP Design
Calculations included under Attachment 1e of this SWQMP.
Structural BMP Summary Information
Structural BMP ID No. SRA-1 (for DMA N3)
DWG _483-6B___ Sheet No. _5_________
Type of structural BMP:
Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1)
Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP
(provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in
discussion section below)
Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only
Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and the self-retaining area (SRA-1) has been
designed solely to address DMA N3 for water quality purposes. The treatment will be achieved by dispersing the runoff from the impervious areas to permeable areas (BMP SD-5) and incorporating Tree Wells (BMP
SD-1) into the site design to promote onsite infiltration.
DMA N3 contains the southern half of Lot 3, and the drainage easement and storm drain infrastructure that
coveys flows from DMAs N1 and N3 along the southern perimeter of Lot 3 prior to discharging to the City MS4.
DMA N3 has been designed such that its 2,202 sq-ft (61.7%) of proposed impervious surfaces (i.e. home, sidewalks, and driveway) will drain to its 1,369 sq-ft (38.3%) of permeable/landscaped area to promote onsite
infiltration. The entire site is underlain by Hydrologic Soil Group B, so in order to comply with the BMP SD-5 requirements
outlined in the City BMP Design Manual the impervious:pervious ratio for DMA N3 must be less than 1.0.
Compliance Check for SRA-1 (imp:perv ratio must be < 1.0): imp:perv ratio = (0.617)/(0.383) = 1.608 1.608 > 1.0 SRA-1 requires additional BMPs Since the impervious:pervious ratio for DMA N3 is larger than 1.0, additional BMPs are required for
compliance. First however, it is important to quantify the impacts of BMP SD-5 by adjusting the Runoff Factor (C) as follows:
• Baseline C = Σ𝐶𝑥𝐴𝑥/Σ𝐴𝑥 = ((0.9 * 0.051-ac) + (0.1 * 0.031-ac))/0.082-ac = 0.59 Baseline C = 0.59.
• imp:perv ratio = (0.617)/(0.383) = 1.608 1.0 < 1.668 < 4.0, since ratio > 1.0, compliance cannot be achieved
through BMP SD-5 alone, but since ratio < 4.0 C Factor adjustment can be claimed.
□ □ □ □ □ □ □
□ l:8J
l:8J □ □ □ l:8J
• Adjustment factors for hydrologic soil group B and a ratio of 1 = 0.0, ratio of 2 = 0.27 (Table B.2-1).
• Linear interpolated adjustment factor for a ratio of 1.608 = 0.0 + (0.27 - 0.0) / (2 - 1) * (1.608 - 1) = 0.16
adjustment factor = 0.16.
• Adjusted C = (0.9 * 0.16 * 0.051-ac + 0.1 * 0.031-ac / 0.082-ac = 0.13 Adjusted C = 0.13
Next, the adjusted C factor is used to calculate the Design Capture Volume (DCV) which is equal to the volume
of runoff in excess of what can be treated through the implementation of BMP SD-5. The DCV may be
calculated simply as follows:
• DCV = C * d * A = 0.13 * 0.59 * 0.082-ac * 43,560 sq-ft/ac * 12-in/ft = 22.74 DCV = 22.7 cu-ft
Finally, a Tree Well (BMP SD-1) was incorporated into the site design to treat the DCV from DMA N3. Tree
wells can further reduce runoff and help to eliminate the DCV because of the water demands of the vegetation
and underlying roots. The Carlsbad BMP Design Manual allows for Tree Credit Volumes (TCV) of 10 cu-ft/tree and 40 cu-ft/trees for proposed tree wells with 5-ft and 10-ft canopy diameters at maturity, respectively.
The project proposes one (1) new tree with a 10-ft canopy diameter at maturity to address the remaining DCV
(22.7 cu-ft) from DMA N3. The final adjusted DCV is determined by simply subtracting DCV from TCV as outlined in Worksheet B.2-1, below:
Worksheet B.2-1. DCV for DMA N3
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.08 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.13 unitless
4 Tree wells volume reduction TCV= 40 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = -17.26 cubic-feet
By Dispersing Runoff from Impervious Areas (SD-5) and with Hydrologic Soil Group B, and an
impervious:pervious ration < 1, the Runoff Factor (C = 0.59) was reduced significantly (adjusted C = 0.13). This
combined with one tree well (with an anticipated 10-ft diameter canopy) reduced the original Design Capture
Volume (DCV = 104 cu-ft) significantly such that the adjusted DCV is negative and does not require further
treatment (adjusted DCV = -17.26 cu-ft) --> DCV = -17.3 < 0 --> OK
Compliance Check for SRA-1 (Final DCV < 0):
Final DCV = DCV – TCV = 22.74 cu-ft – 40 cu-ft = -17.26 cu-ft Final DCV = -17.3 cu-ft
Final DCV = -17.3 < 0 SRA-1 as designed is compliant.
In summary by incorporating Impervious Area Dispersion (BMP SD-5) and a Tree Well (BMP SD-1),
into the site plan, SRA 3 has been designed in compliance with City water quality requirements as a
Self-Retaining DMA via qualifying Site Design BMPs. Please refer to the BMP Design calculations included under SWQMP Attachment 1e.
Structural BMP Summary Information
Structural BMP ID No. SRA-2 (for DMA N4)
DWG __483-6B_ Sheet No. _5_________
Type of structural BMP:
Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1)
Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP
(provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in
discussion section below)
Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only
Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and the self-retaining area (SRA-4) has been
designed solely to address DMA N4 for water quality purposes. The treatment will be achieved by dispersing the runoff from the impervious areas to permeable areas (BMP SD-5) and incorporating tree wells (BMP SD-1)
into the site design to promote onsite infiltration.
DMA N4 is 0.082-acres (49.9% impervious) and contains the northern half of Lot 3, and a swale and storm drain that conveys runoff along the northern edge of Lot 3 prior to discharging to the City MS4. There is also a
drainage easement along the eastern perimeter of DMA N4 that accepts flows from Lots 1 and 2 and conveys them to the back of the curb inlet on James Drive.
The total area within DMA N4 is 3,571 sq-ft (0.082-acres), and it has been designed such that its 1,782 sq-ft (49.89) of proposed impervious surfaces (i.e. home and sidewalks) will drain to its 1,789 sq-ft (50.1%) of
permeable/landscaped area to promote onsite infiltration.
The entire site is underlain by Hydrologic Soil Group B, so in order to comply with the BMP SD-5 requirements
outlined in the City BMP Design Manual the impervious:pervious ratio for DMA N3 must be less than 1.0. Compliance Check for SRA-2 (imp:perv ratio must be < 1.0):
imp:perv ratio = (0.499)/(0.501) = 0.996 0.996 < 1.0 OK SRA-2 as designed is compliant.
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Worksheet B.2-1. DCV for DMA N4
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.08 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.50 unitless
4 Tree wells volume reduction TCV= 0 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = 87.65 cubic-feet
Please note that SRA 2 has been designed in compliance with City water quality requirements as a
Self-Retaining DMA via qualifying Site Design BMPs. Compliance Check for SRA-2 (imp:perv ratio must be <
1.0): imp:perv ratio = (0.499)/(0.501) = 0.996 --> 0.996 < 1.0 --> OK
In summary by incorporating Impervious Area Dispersion (BMP SD-5) into the site plan, SRA 2 has been
designed in compliance with City water quality requirements as a Self-Retaining DMA via Qualifying Site Design BMPs. For further details, please refer to the BMP Design Calculations included under Attachment 1e
of this SWQMP.
Structural BMP Summary Information
Structural BMP ID No. SRA-3 (for DMA N5)
DWG __483-6B_ Sheet No. _4_________
Type of structural BMP:
Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1)
Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP
(provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in
discussion section below)
Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only
Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and the self-retaining area (SRA-3) has been
designed solely to address DMA N5 for water quality purposes. The treatment will be achieved by dispersing the runoff from the impervious areas to permeable areas (BMP SD-5) and incorporating Tree Wells (BMP
SD-1) into the site design to promote onsite infiltration.
DMA N5 is 0.082-acres contains the southern half of Lot 2, and a swale and storm drain that conveys runoff
along the southern edge of Lot 2 prior to discharging to the City MS4 (via the drainage easement along the
eastern edge of Lot 3). DMA N5 has been designed such that its 2,309 sq-ft (64.7%) of proposed impervious surfaces (i.e. home, sidewalks, and driveway) will drain to its 1,262 sq-ft (35.3%) of permeable/landscaped
area to promote onsite infiltration. The entire site is underlain by Hydrologic Soil Group B, so in order to comply with the BMP SD-5 requirements
outlined in the City BMP Design Manual the impervious:pervious ratio for DMA N4 must be less than 1.0.
Compliance Check for SRA-3 (imp:perv ratio must be < 1.0): imp:perv ratio = (0.647)/(0.353) = 1.830 1.830 > 1.0 SRA-3 requires additional BMPs Since the impervious:pervious ratio for DMA N5 is larger than 1.0, additional BMPs are required for
compliance. First however, it is important to quantify the impacts of BMP SD-5 by adjusting the Runoff Factor (C) as follows:
• Baseline C = Σ𝐶𝑥𝐴𝑥/Σ𝐴𝑥 = ((0.9 * 0.053-ac) + (0.1 * 0.029-ac))/0.082-ac = 0.62 Baseline C = 0.62.
• imp:perv ratio = (0.65)/(0.35) = 1.830 1.0 < 1.830 < 4.0, since ratio > 1.0, compliance cannot be achieved
through BMP SD-5 alone, but since ratio < 4.0 C Factor adjustment can be claimed.
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• Adjustment factors for hydrologic soil group B and a ratio of 1 = 0.0, ratio of 2 = 0.27 (Table B.2-1).
• Linear interpolated adjustment factor for a ratio of 1.830 = 0.0 + (0.27 - 0.0) / (2 - 1) * (1.830 - 1) = 0.22
adjustment factor = 0.22.
• Adjusted C = (0.9 * 0.22 * 0.053-ac + 0.1 * 0.029-ac / 0.082-ac = 0.17 Adjusted C = 0.17
Next, the adjusted C factor is used to calculate the Design Capture Volume (DCV) which is equal to the volume
of runoff in excess of what can be treated through the implementation of BMP SD-5. The DCV may be
calculated simply as follows:
• DCV = C * d * A = 0.09 * 0.59 * 0.082-ac * 43,560 sq-ft/ac * 12-in/ft = 29.09 DCV = 29.1 cu-ft
Finally, a Tree Well (BMP SD-1) was incorporated into the site design to treat the DCV from DMA N5. Tree
wells can further reduce runoff and help to eliminate the DCV because of the water demands of the vegetation
and underlying roots. The Carlsbad BMP Design Manual allows for Tree Credit Volumes (TCV) of 10 cu-ft/tree and 40 cu-ft/trees for proposed tree wells with 5-ft and 10-ft canopy diameters at maturity, respectively.
The project proposes one (1) new tree with a 10-ft canopy diameter at maturity to address the remaining DCV
(29.1 cu-ft) from DMA N5. The final adjusted DCV is determined by simply subtracting DCV from TCV as outlined in Worksheet B.2-1, below:
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.08 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.17 unitless
4 Tree wells volume reduction TCV= 40 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = -10.91 cubic-feet
By Dispersing Runoff from Impervious Areas (SD-5) and with Hydrologic Soil Group B, and an
impervious:pervious ration < 1, the Runoff Factor (C = 0.62) was reduced significantly (adjusted C = 0.17). This
combined with one tree well (with an anticipated 10-ft diameter canopy) reduced the Design Capture
Volume (DCV = 108 cu-ft) significantly such that the adjusted DCV is negative and does not require further
treatment (adjusted DCV = -10.91 cu-ft) --> DCV = -10.9 < 0 --> OK
Compliance Check for SRA-3 (Final DCV < 0):
Final DCV = DCV – TCV = 29.09 cu-ft – 40 cu-ft = -10.91 cu-ft Final DCV = -10.9 cu-ft Final DCV = -10.9 < 0 SRA-3 as designed is compliant.
In summary by incorporating Impervious Area Dispersion (BMP SD-5) and Tree Wells (BMP SD-1),
into the site plan, SRA 3 has been designed in compliance with City water quality requirements as a Self-Retaining DMA via qualifying Site Design BMPs. Please refer to the BMP Design calculations
included under SWQMP Attachment 1e.
Structural BMP Summary Information
Structural BMP ID No. SRA-4 (for DMA N6)
DWG __483-6B_ Sheet No. _4_________
Type of structural BMP:
Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1) Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1) Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below)
Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only Hydromodification control only
Combined pollutant control and hydromodification control Pre-treatment/forebay for another structural BMP Other (describe in discussion section below)
Discussion (as needed): The site is exempt from hydromodification requirements and the self-retaining area (SRA-4) has been designed solely to address DMA N6 for water quality purposes. The treatment will be achieved by dispersing
the runoff from the impervious areas to permeable areas (BMP SD-5) and incorporating tree wells (BMP SD-1) into the site design to promote onsite infiltration.
DMA N6 is 0.082-acres and contains the northern half of Lot 2 and a swale and storm drain that conveys runoff along the northern edge of Lot 2 prior to discharging to the City MS4 (via the drainage easement along the
eastern edge of Lot 3). DMA N6 has been designed such that its 1,798 sq-ft (50.4%) of proposed impervious
surfaces (i.e. homes, sidewalks, and driveways) will drain to its 1,773 sq-ft (49.6%) of permeable/landscaped area to promote onsite infiltration.
The entire site is underlain by Hydrologic Soil Group B, so in order to comply with the BMP SD-5 requirements outlined in the City BMP Design Manual the impervious:pervious ratio for DMA N6 must be less than 1.0.
Compliance Check for SRA-4 (imp:perv ratio must be < 1.0): imp:perv ratio = (0.504)/(0.496) = 1.014 1.014 > 1.0 SRA-4 requires additional BMPs
Since the impervious:pervious ratio for DMA N6 is larger than 1.0, additional BMPs are required for compliance. First however, it is important to quantify the impacts of BMP SD-5 by adjusting the Runoff Factor
(C) as follows:
• Baseline C = Σ𝐶𝑥𝐴𝑥/Σ𝐴𝑥 = ((0.9 * 0.041-ac) + (0.1 * 0.041-ac))/0.082-ac = 0.50 Baseline C = 0.50.
• imp:perv ratio = (0.504)/(0.496) = 1.014 1.0 < 1.014 < 4.0, since ratio > 1.0, compliance cannot be achieved through BMP SD-5 alone, but since ratio < 4.0 C Factor adjustment can be claimed.
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• Adjustment factors for hydrologic soil group B and a ratio of 1 = 0.0, ratio of 2 = 0.27 (Table B.2-1).
• Linear interpolated adjustment factor for a ratio of 1.014 = 0.0 + (0.27 - 0.0) / (2 - 1) * (1.042 - 1) = 0.004
adjustment factor = 0.004.
• Adjusted C = (0.9 * 0.004 * 0.041-ac + 0.1 * 0.041-ac / 0.082-ac = 0.05 Adjusted C = 0.05
Next, the adjusted C factor is used to calculate the Design Capture Volume (DCV) which is equal to the volume
of runoff in excess of what can be treated through the implementation of BMP SD-5. The DCV may be calculated simply as follows:
• DCV = C * d * A = 0.05 * 0.59 * 0.082-ac * 43,560 sq-ft/ac * 12-in/ft = 9.02 DCV = 9.0 cu-ft
Finally, a Tree Well (BMP SD-1) was incorporated into the site design to treat the DCV from DMA N6. Tree wells can further reduce runoff and help to eliminate the DCV because of the water demands of the vegetation
and underlying roots. The Carlsbad BMP Design Manual allows for Tree Credit Volumes (TCV) of 10 cu-ft/tree and 40 cu-ft/trees for proposed tree wells with 5-ft and 10-ft canopy diameters at maturity, respectively.
The project proposes one (1) new tree with a 5-ft canopy diameter at maturity to address the remaining DCV (10 cu-ft) from DMA N6. The final adjusted DCV is determined by simply subtracting DCV from TCV as outlined
in Worksheet B.2-1, below:
Worksheet B.2-1. DCV for DMA N6
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.08 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.05 unitless
4 Tree wells volume reduction TCV= 10 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = -0.98 cubic-feet
By Dispersing Runoff from Impervious Areas (SD-5) and with Hydrologic Soil Group B, and an
impervious:pervious ration < 1, the Runoff Factor (C = 0.50) was reduced significantly (adjusted C = 0.05). This
combined with one tree well (with an anticipated 5-ft diameter canopy) reduced the Design Capture Volume
(DCV = 88 cu-ft) significantly such that the adjusted DCV is negative and does not require further treatment
(adjusted DCV = -0.98 cu-ft) --> DCV = -0.98 < 0 --> OK
Compliance Check for SRA-4 (Final DCV = -0.98 cu-ft):
Final DCV = DCV – TCV = 9.02 cu-ft -- 10 cu-ft = -0.98 cu-ft Final DCV = -0.98 cu-ft Final DCV = 0 SRA-4 as designed is compliant.
In summary by incorporating Impervious Area Dispersion (BMP SD-5) and a Tree Well (BMP SD-1), into the
site plan, SRA 4 has been designed in compliance with City water quality requirements as a Self-Retaining DMA via Qualifying Site Design BMPs. For further details, please refer to the BMP design calculations included
under SWQMP Attachment 1e.
Structural BMP Summary Information
Structural BMP ID No. SRA-5 (for DMA N7)
DWG __483-6B_ Sheet No. _3_________
Type of structural BMP: Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2) Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1)
Biofiltration (BF-1) Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration
BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below) Detention pond or vault for hydromodification management
Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only Combined pollutant control and hydromodification control
Pre-treatment/forebay for another structural BMP Other (describe in discussion section below)
Discussion (as needed):
The site is exempt from hydromodification requirements and the self-retaining area (SRA-5) has been designed solely to address DMA N7 for water quality purposes. The treatment will be achieved by dispersing the runoff from the impervious areas to permeable areas (BMP SD-5) and incorporating tree wells (BMP
SD-1) into the site design to promote onsite infiltration.
DMA N7 is 0.082-acres and contains the southern half of Lot 1, and the drainage easement and storm drain
infrastructure that coveys flows from DMAs N2 and N7 along the southern perimeter of Lot 1 prior to discharging to the City MS4 (via the drainage easement along the eastern edge of Lots 2 and 3). DMA N7
has been designed such that its 2,172 sq-ft (60.8%) of proposed impervious surfaces (i.e. homes, sidewalks,
and driveways) will drain to its 1,399 sq-ft (39.2%) of permeable/landscaped area to promote onsite infiltration.
The entire site is underlain by Hydrologic Soil Group B, so in order to comply with the BMP SD-5 requirements outlined in the City of Carlsbad BMP Design Manual the impervious:pervious ratio for DMA N7
must be less than 1.0.
Compliance Check for SRA-5 (imp:perv ratio must be < 1.0):
imp:perv ratio = (0.608)/(0.392) = 1.553 1.553 > 1.0 SRA-5 requires additional BMPs Since the impervious:pervious ratio for DMA N7 is larger than 1.0, additional BMPs are required for
compliance. First however, it is important to quantify the impacts of BMP SD-5 by adjusting the Runoff Factor (C) as follows:
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• Baseline C = Σ𝐶𝑥𝐴𝑥/Σ𝐴𝑥 = ((0.9 * 0.050-ac) + (0.1 * 0.032-ac))/0.082-ac = 0.59 Baseline C = 0.59.
• imp:perv ratio = (0.608)/(0.392) = 1.553 1.0 < 1.553 < 4.0, since ratio > 1.0, compliance cannot be achieved through BMP SD-5 alone, but since ratio < 4.0 C Factor adjustment can be claimed.
• Adjustment factors for hydrologic soil group B and a ratio of 1 = 0.0, ratio of 2 = 0.27 (Table B.2-1).
• Linear interpolated adjustment factor for a ratio of 1.553 = 0.0 + (0.27 - 0.0) / (2 - 1) * (1.553 - 1) =
0.15 adjustment factor = 0.15.
• Adjusted C = (0.9 * 0.15 * 0.050-ac + 0.1 * 0.032-ac / 0.082-ac = 0.12 Adjusted C = 0.12
Next, the adjusted C factor is used to calculate the Design Capture Volume (DCV) which is equal to the volume of runoff in excess of what can be treated through the implementation of BMP SD-5. The DCV may
be calculated simply as follows:
• DCV = C * d * A = 0.12 * 0.59 * 0.082-ac * 43,560 sq-ft/ac * 12-in/ft = 21.22 DCV = 21.2 cu-ft
Finally, a Tree Well (BMP SD-1) was incorporated into the site design to treat the DCV from DMA N7. Tree
wells can further reduce runoff and help to eliminate the DCV because of the water demands of the vegetation and underlying roots. The Carlsbad BMP Design Manual allows for Tree Credit Volumes (TCV) of
10 cu-ft/tree and 40 cu-ft/trees for proposed tree wells with 5-ft and 10-ft canopy diameters at maturity,
respectively.
The project proposes one (1) new tree with a 10-ft canopy diameter at maturity to address the remaining DCV (10 cu-ft) from DMA N7. The final adjusted DCV is determined by simply subtracting DCV from TCV as outlined in Worksheet B.2-1, below:
Worksheet B.2-1. DCV for DMA N7
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.08 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.12 unitless
4 Tree wells volume reduction TCV= 40 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = -18.78 cubic-feet
By Dispersing Runoff from Impervious Areas (SD-5) and with Hydrologic Soil Group B, and an
impervious:pervious ration < 1, the Runoff Factor (C = 0.59) was reduced significantly (adjusted C = 0.12). This
combined with one tree wells (with an anticipated 10-ft diameter canopy) reduced the Design Capture Volume
(DCV = 103 cu-ft) significantly such that the adjusted DCV is negative and does not require further treatment
(adjusted DCV = -18.78 cu-ft) --> DCV = -18.8 < 0 --> OK
Compliance Check for SRA-5 (Final DCV < 0): Final DCV = DCV – TCV = 40 cu-ft – 21.22 cu-ft = -18.78 cu-ft Final DCV = -18.78 cu-ft
Final DCV = -18.78 cu-ft < 0 SRA-5 as designed is compliant.
In summary by incorporating Impervious Area Dispersion (BMP SD-5) and a Tree Well (BMP SD-1), into the
site plan, SRA 5 has been designed in compliance with City water quality requirements as a Self-Retaining
DMA via qualifying Site Design BMPs. Please refer to the BMP Design calculations included under SWQMP Attachment 1e.
Structural BMP Summary Information
Structural BMP ID No. SRA-6 (for DMA N8)
DWG __483-6B_ Sheet No. _3________
Type of structural BMP:
Retention by harvest and use (HU-1) Retention by infiltration basin (INF-1) Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1) Biofiltration (BF-1)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below)
Detention pond or vault for hydromodification management Other (describe in discussion section below)
Purpose: Pollutant control only
Hydromodification control only
Combined pollutant control and hydromodification control Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Discussion (as needed): The site is exempt from hydromodification requirements and the self-retaining area (SRA-6) has been
designed solely to address DMA N8 for water quality purposes. The treatment will be achieved by dispersing
the runoff from the impervious areas to permeable areas (BMP SD-5) and incorporating tree wells (BMP SD-1) into the site design to promote onsite infiltration.
DMA N8 is 0.082-acres and contains the northern half of Lot 1 and a swale and storm drain that conveys runoff along the northern edge of Lot 1 prior to discharging to the City MS4 (via the drainage easement along
the eastern edge of Lots 2 and 3). DMA N8 has been designed such that its 1,765 sq-ft (49.4%) of proposed
impervious surfaces (i.e. home and sidewalks) will drain to its 1,806 sq-ft (50.6%) of permeable/landscaped area to promote onsite infiltration.
The entire site is underlain by Hydrologic Soil Group B, so in order to comply with the BMP SD-5 requirements outlined in the City of Carlsbad BMP Design Manual the impervious:pervious ratio for DMA N8
must be less than 1.0. Compliance Check for SRA-6 (imp:perv ratio must be < 1.0):
imp:perv ratio = (0.494)/(0.506) = 0.977 0.977 < 1.0 OK SRA-6 as designed is compliant.
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Worksheet B.2-1. DCV for DMA N8
Design Capture Volume Worksheet B-2.1
1 85th percentile 24-hr storm depth from Figure B.1-1 d = 0.59 inches
2 Area tributary to BMP (s) A = 0.08 acres
3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1) C = 0.50 unitless
4 Tree wells volume reduction TCV= 0 cubic-feet
5 Rain barrels volume reduction RCV= 0 cubic-feet
6
Calculate DCV =
(3630 x C x d x A) - TCV - RCV DCV = 86.98 cubic-feet
Please note that SRA 6 has been designed in compliance with City water quality requirements as a
Self-Retaining DMA via qualifying Site Design BMPs. Compliance Check for SRA-6 (imp:perv ratio must be < 1.0):
imp:perv ratio = (0.494)/(0.506) = 0.977 --> 0.977 < 1.0 --> OK
In summary by incorporating Impervious Area Dispersion (BMP SD-5) into the site plan, SRA 6 has been
designed in compliance with City water quality requirements as a Self-Retaining DMA via Qualifying Site Design BMPs. For further details, please refer to the BMP Design Calculations included under Attachment
1e of this SWQMP.
ATTACHMENT 1 BACKUP FOR PDP POLLUTANT CONTROL BMPS
This is the cover sheet for Attachment 1.
Check which Items are Included behind this cover sheet:
Attachment Sequence Contents Checklist
Attachment 1a DMA Exhibit (Required)
See DMA Exhibit Checklist on the
back of this Attachment cover sheet. (24”x36” Exhibit typically required)
Included
Attachment 1b Tabular Summary of DMAs Showing
DMA ID matching DMA Exhibit, DMA Area, and DMA Type (Required)*
*Provide table in this Attachment OR
on DMA Exhibit in Attachment 1a
Included on DMA Exhibit in
Attachment 1a
Included as Attachment 1b, separate from DMA Exhibit
Attachment 1c Form I-7, Harvest and Use Feasibility Screening Checklist (Required unless
the entire project will use infiltration BMPs)
Refer to Appendix B.3-1 of the BMP Design Manual to complete Form I-7.
Included
Not included because the entire
project will use infiltration BMPs
Attachment 1d Form I-8, Categorization of Infiltration Feasibility Condition (Required unless
the project will use harvest and use BMPs)
Refer to Appendices C and D of the BMP Design Manual to complete Form
I-8.
Included
Not included because the entire
project will use harvest and use
BMPs
Attachment 1e Pollutant Control BMP Design
Worksheets / Calculations (Required)
Refer to Appendices B and E of the
BMP Design Manual for structural pollutant control BMP design
guidelines
Included
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Use this checklist to ensure the required information has been included on the DMA Exhibit:
The DMA Exhibit must identify:
Underlying hydrologic soil group -- B
Approximate depth to groundwater – Greater than 15 ft
Existing natural hydrologic features (watercourses, seeps, springs, wetlands) – N/A
Critical coarse sediment yield areas to be protected (if present) – N/A
Existing topography and impervious areas – See DMA Exhibit
Existing and proposed site drainage network and connections to drainage offsite – See DMA
Exhibit
Proposed grading – See DMA Exhibit
Proposed impervious features – See DMA Exhibit
Proposed design features and surface treatments used to minimize imperviousness – See DMA
Exhibit,
Drainage management area (DMA) boundaries, DMA ID numbers, and DMA areas (square
footage or acreage), and DMA type (i.e., drains to BMP, self-retaining, or self-mitigating)
DMA Area (sq-ft) Type
N1a 1625 Drains to Structural BMP – Bioretention Basin PR-1a
N1b 11917 Drains to Structural BMP – Bioretention Basin PR-1a
N1c 605 Self-Mitigating Area (SMA-1)
N2a 1678 Drains to Structural BMP – Bioretention Basin PR-1b
N2b 11917 Drains to Structural BMP – Bioretention` Basin PR-1b
N2c 484 Self-Mitigating Area (SMA-2)
N3 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-1)
N4 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-2)
N5 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-3)
N6 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-4)
N7 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-5)
N8 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-6)
Structural BMPs (identify location and type of BMP):
o PR-1a for DMAs N1a and N1b
o PR-1b for DMAs N2a and N2b
o SMA-1 – Self-Mitigating Area for DMA N1c
o SMA-2 – Self-Mitigating Area for DMA N2c
o SRA-1 – Self-Retaining Area via Qualifying Site Design BMPs for DMA N3
o SRA-2 – Self-Retaining Area via Qualifying Site Design BMPs for DMA N4
o SRA-3 – Self-Retaining Area via Qualifying Site Design BMPs for DMA N5
o SRA-4 – Self-Retaining Area via Qualifying Site Design BMPs for DMA N6
o SRA-5 – Self-Retaining Area via Qualifying Site Design BMPs for DMA N7
o SRA-6 – Self-Retaining Area via Qualifying Site Design BMPs for DMA N8
o TW-1 – 5-ft diameter canopy One (1) Tree Well on the north side of Lot 2 for DMA N6
o TW-2 – 10-ft diameter canopy – 3 total
1 on the south side of Lot 3 for DMA N3,
1 on the south side of Lot 2 for DMA N5, and
1 on the south side of Lot 1 for DMA N7.
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ATTACHMENT 1A: DMA EXHIBIT
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/
LEGEND
(E) : EXISTING , (N) : NEW/ PROPOSED
--- ---(E) PROPERTY LINE
- ---(E) MAJOR CONTOUR
- --(E) MINOR CONTOUR
====== (E)CURB&GUTTER
- -12" SD -(E) 12" RCP STORM DRAIN PIPE
- -18" SD -(E) 18" RCP STORM DRAIN PIPE
- -48" SD-(E) 48" RCP STORM DRAIN PIPE
El (E) STORM DRAIN INLET
-~~~-~ (E)RETAININGWALL c=J-(E)ACPAVEMENT
~---(E)BUILDING
• • -(E) CONCRETE □---(E)VEGETATION
---DRAINAGE DIRECTION
--DMA BOUNDARY
@ DMALABEL
C
VICINITY MAP
NTS
0 20 40 80 160 ~~--1-----------11
SCALE: 1" = 40 FEET
PRE-DEVELOPMENT CONDITION
DRAINAGE AREA MAP
POST-DEVELOPMENT CONDITION
DRAINAGE AREA MAP
DMA EXHIBIT NOTES:
1. ENTIRE SITE IS UNDERLAIN WITH HYDROLOGIC SOIL GROUP B
2. THE APPROXIMATE DEPTH TO GROUNDWATER IS GREATER THAN 15 FT
3. THE SITE DOES NOT CONTAIN ANY EXISTING NATURAL HYDROLOGIC FEATURES (WATERCOURSES, SEEPS,
SPRINGS, WETLANDS)
4. THE SITE DOES NOT CONTAIN ANY CRITICAL COARSE SEDIMENT YIELD AREAS TO BE PROTECTED
5. PROPOSED DESIGN FEATURES AND SURFACE TREATMENTS USED TO MINIMIZE IMPERVIOUSNESS INCLUDE TREE
WELLS (BMP SD-1) AND IMPERVIOUS AREA DISPERSION (BMP SD-5) SUCH THAT EACH OF THE DMAs N3 THOURGH N8
MAY BE CONSIDERED SELF RETAINING AREAS VIA QUALIFYING SITE DESIGN BMPS
6. STRUCTURAL BMPS WERE INCORPORATED TO MEET WATER QUALITY REQUIREMENTS FOR DMAs N1 & N2.
0
SCALE: 1" =FEET
40 4020 80 160
40
I )
)
EX
DWY
r ----lh-J-.-·.
I
~ ---(160)
I / I -~-r
L-~ -,/
i~--l1 ---I -I
SD-
/
-
EX
DWY
,-----I
◊
'-----..._,_ ---
48" SD~ -48" SD-
,
/
LEGEND
(E) : EXISTING , (N): NEW/ PROPOSED
---(E) PROPERTY LINE
------(E) MAJOR CONTOUR
(E) MINOR CONTOUR
======== (E)CURB&GUTTER
--(E) STRIPING
--------(N) MAJOR CONTOUR
--------(N) MINOR CONTOUR
- -12" SD -(E)12"RCPSTORMDRAINPIPE
- -18" SD -(E)18"RCPSTORMDRAINPIPE
- -48" SD-(E)48"RCPSTORMDRAINPIPE
§ (E) STORM DRAIN INLET
-~-~-~--(E) RETAINING WALL
-(E) CONCRETE
~----(N) BIORETENTION BMP
~-(N) BUILDING
~ (N) HARDSCAPE
OMA AREA (SF) TYPE/NOTES
~~~-~~~-(N)RETAININGWALL
--- - - - ---(N) EARTHEN SWALE FLOWLINE
~Mkl (N) RIPRAP SWALE
4" SD --(N)4"0SDPIPE
--611 SD --(N)6"0SDPIPE
--8" SD --(N)8"0SDPIPE
--10" SD --(N)10"0SDPIPE
--18" SD --(N) 18" 0 SD PIPE
Cl (N) SD CATCH BASIN 0 ---TREEWELL10'CANOPY 0--TREE WELL 5' CANOPY
-DRAINAGE DIRECTION --
-DMA BOUNDARY
GD DMALABEL ~
N1a 1,635 SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN INF -2a
N1b 11,917 SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN INF -2a
N1c 605SF SELF-MITIGATING AREA (SMA-1)
N2a 1,669 SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN INF -2b
N2b 11,917SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN INF -2b
N2c 484SF SELF-MITIGATING AREA (SMA-2)
N3 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-1)
N4 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-2)
N5 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-3)
N6 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-4)
N7 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-5)
N8 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-6)
ATTACHMENT 1B: DMA SUMMARY TABLE
Tabular Summary of DMAs Showing DMA ID matching DMA Exhibit, DMA Area, and DMA Type
(Required)*
DMA ID AREA (sq-ft) TYPE
N1a 1625 Drains to Structural BMP – Bioretention Basin PR-1a
N1b 11917 Drains to Structural BMP – Bioretention Basin PR-1a
N1c 605 Self-Mitigating Area (SMA-1)
N2a 1678 Drains to Structural BMP – Bioretention Basin PR-1b
N2b 11917 Drains to Structural BMP – Bioretention Basin PR-1b
N2c 484 Self-Mitigating Area (SMA-2)
N3 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-1)
N4 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-2)
N5 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-3)
N6 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-4)
N7 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-5)
N8 3571 Self-Retaining Area via Qualifying Site Design BMPs (SRA-6)
ATTACHMENT 1C: FORM I-7, HARVEST AND USE FEASIBILITY SCREENING CHECKLIST
Harvest and Use Feasibility Checklist Form I-7
1. Is there a demand for harvested water (check all that apply) at the project site that is reliably present during the wet season?
Toilet and urinal flushing
Landscape irrigation
Other:______________
2. If there is a demand; estimate the anticipated average wet season demand over a period of 36 hours. Guidance for planning
level demand calculations for toilet/urinal flushing and landscape irrigation is provided in Section B.3.2.
• Toilet/Urinal Demand was determined using BMP Design Manual Table B.3-1 as follows: o Assumptions – residential use, assumed 4 residents per household for each of the 5
proposed homes 18.5 flushes/person/day o Toilet/Urinal Demand = 186 flushes * 1.6 gallons/flush = 297.6 gpd, which converts 446.4 gallons/36-hours or 59.7 cu-ft 36-Hour Toilet Demand = 59.7 cu-ft
• Landscape Demand was calculated using the Modified Estimated Total Water Use equation outlined under BMP Manual Section B.3.2.2.1 as follows:
Modified ETWU = (EToWet × (SUM (PF*HA)/IE) + SLA) * 0.015) via BMP Manual page B-15
Modified ETWU = Estimated daily average water use during wet season
ETOWet = 2.8 in/month via BMP Manual page B-15 using CIMS Zone 4 from Table G.1-1
Plant Factor (PF) = 0.5 via BMP Manual Table B.3-2 using Moderate plant water use
Hydrozone Area (HA) = 29,885 sq-ft (this analysis evaluates the water demand from all 5 Lots combined)
Hydrozone Area (HA) = 0.69 acre
Irrigation Efficiency (IE) 0.9 assumed 90% per BMP Manual page B-16
Special Landscaped Areas (SLA) = 0 * if reclaimed water is available then SLA = HA, if unavailable then SLA = 0
3-day irrigation shut down after rain event = 0.015 (1 mo/30 days) * (I ft/12-in) * (7.48 gal/cu-ft) * (7 out of 10 days with irrigation demand in rainy season)
Modified ETWU = 701.32 gpd
36-hr Landscape Demand = 1,052 gallons
36-hr Landscape Demand = 140.6 cu-ft The simplified planning level irrigation demand as outlined under BMP Design Manual Section B.3.2.2.2.was also used to check the Landscape Demand calculations as follows:
check via Simplified ETWU -- site has 27,507 sq-ft (0.63 acres) of landscaping requiring irrigation
Hydrozone Moderate plant water use = 1470 gallons per irrigated acre per 36-hour period via Table B.3-3
36-hr Landscape Demand = 1,014 gallons per 36-hour period
36-hr Landscape Demand = 135.6 cu-ft
To be conservative the higher value 36-hr Landscape Demand = 140.6 cu-ft is used
3. Calculate the DCV using worksheet B-2.1.
DCV = __1,022________ (cubic feet)
~
~
□
I
I
-
3a. Is the 36 hour demand greater than or
equal to the DCV?
Yes / No
3b. Is the 36 hour demand greater than
0.25DCV but less than the full DCV?
Yes / No
3c. Is the 36 hour demand less than
0.25DCV?
Yes
Harvest and use appears to be
feasible. Conduct more detailed evaluation and sizing calculations
to confirm that DCV can be used at an adequate rate to meet
drawdown criteria.
Harvest and use may be feasible.
Conduct more detailed evaluation and sizing calculations to determine
feasibility. Harvest and use may only be able to be used for a portion of the site, or
(optionally) the storage may need to be upsized to meet long term capture targets
while draining in longer than 36 hours.
Harvest and use is considered to be
infeasible.
Is harvest and use feasible based on further evaluation?
Yes, refer to Appendix E to select and size harvest and use BMPs.
No, select alternate BMPs.
□ ~ ~ □ ~ ~ ~
i i i
□ ~
ATTACHMENT 1D: FORM I-8, CATEGORIZATION OF INFILTRATION FEASIBILITY CONDITION
Categorization of Infiltration Feasibility Condition Form I-8
Part 1 - Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
1
Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response to this Screening Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.2 and Appendix D.
X
Provide basis:
An onsite percolation study was conducted on the subject property which indicates that the soils underneath
the proposed Biofiltration with Partial Retention Basin infiltrate at 0.125 inch/hour (please note that the soils
near the proposed tree wells infiltrate at significantly higher rates – from 2.9- up to 6.0 in/hr).
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
For further details, please refer to the Percolation Test Results prepared by Construction Testing &
Engineering, Inc. (March, 2016).
2
Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2.
X
Provide basis:
N/A -- onsite percolation testing indicates that soils will not infiltrate at rates greater than 0.5-in/hr (rates
near BMP measured at 0.125 in/hr).
The project includes 5 proposed free-standing homes, their driveways, utility connections and a slope and
storm drain easement. The development of the site will produce a relatively small increase in the amount of
runoff which shall be addressed through the implementation of Site Design BMPs (specifically BMP SD-1 and
SD-5) and Biofiltration with Partial Retention Basins (PR-1). The site has been designed to direct runoff from
impervious surfaces to permeable areas onsite. It is not anticipated that the infiltration associated with the
selected BMPs will increase the risk of geotechnical hazards. The proposed Biofiltration with Partial
Retention Basins have been designed with vertical impermeable liners to direct the infiltration downward
and better protect the surrounding soils.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
For further details, please refer to the Percolation Test Results prepared by Construction Testing &
Engineering, Inc. (March, 2016).
I
Form I-8 Page 2 of 4
Criteria Screening Question Yes No
3
Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of groundwater contamination (shallow water table, storm water pollutants or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a
comprehensive evaluation of the factors presented in Appendix C.3.
X
Provide basis:
N/A -- onsite percolation testing indicates that soils will not infiltrate at rates greater than 0.5-in/hr (rates
near BMP measured at 0.125 in/hr).
The actual depth to groundwater is not known. A Site Inspection was performed by Soil Testers, Inc., that
included borings up to 15 feet in depth without encountering groundwater. It is not anticipated that the
proposed infiltration will increase the risk of groundwater contamination.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
For further details, please refer to the Site Inspection prepared by Soil Testers, Inc. (September, 2005).
4
Can infiltration greater than 0.5 inches per hour be allowed without causing potential water balance issues such as change of seasonality of ephemeral streams or increased discharge of contaminated groundwater to surface waters? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3.
X
Provide basis:
N/A -- onsite percolation testing indicates that soils will not infiltrate at rates greater than 0.5-in/hr (rates
near BMP measured at 0.125 in/hr).
The Geotechnical study did not evaluate potential water balance issues such as change of seasonality of
ephemeral streams or increased discharge of contaminated groundwater to surface waters; however it is not
anticipated to be problematic due to the relatively small amount of runoff generated by the project. It is
unlikely that implementing biofiltration with partial infiltration-based BMPs on this 1.14-acre will result in
water balance issues for the surrounding watershed.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability.
For further details, please refer to the Site Inspection prepared by Soil Testers, Inc. (September, 2005), and
the Percolation Test Results prepared by Construction Testing & Engineering, Inc. (March, 2016).
Part 1 Result*
If all answers to rows 1 - 4 are “Yes” a full infiltration design is potentially
feasible. The feasibility screening category is Full Infiltration
If any answer from row 1-4 is “No”, infiltration may be possible to some extent but would not generally be feasible or desirable to achieve a “full
infiltration” design. Proceed to Part 2
Infiltration may be possible
– continue to Part 2, below.
*To be completed using gathered site information and best professional judgment considering the definition of MEP in the MS4
Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings.
Form I-8 Page 3 of 4
Part 2 – Partial Infiltration vs. No Infiltration Feasibility Screening Criteria
Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
5
Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Screening Question shall be based on a
comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D.
X
Provide basis:
As noted in the results from Part 1 above, the soils onsite are not conducive for a full infiltration design. An
onsite percolation study was conducted on the subject property which indicates that the soils underneath
the proposed BMP discharge locations infiltrate at 0.125 inch/hour (please note that the soils near the
proposed tree wells infiltrate at significantly higher rates – from 2.9- up to 6.0 in/hr).
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates.
For further details, please refer to the Percolation Test Results prepared by Construction Testing &
Engineering, Inc. (March, 2016).
6
Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, groundwater
mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a
comprehensive evaluation of the factors presented in Appendix C.2.
X
Provide basis:
As noted in the results from Part 1 above, the soils onsite are not conducive for a full infiltration design. An
onsite percolation study was conducted on the subject property which indicates that the soils underneath
the proposed BMP discharge locations infiltrate at 0.125 inch/hour. It is not anticipated that the infiltration
associated with the selected BMPs will increase the risk of geotechnical hazards. The proposed Biofiltration
with partial retention basins have been designed with vertical impermeable liners to direct the infiltration
downward and better protect the surrounding soils.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates.
For further details, please refer to the Percolation Test Results prepared by Construction Testing &
Engineering, Inc. (March, 2016).
Form I-8 Page 4 of 4
Criteria Screening Question Yes No
7
Can Infiltration in any appreciable quantity be allowed without posing significant risk for groundwater related concerns (shallow water table, storm water pollutants or other factors)? The response to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
X
Provide basis:
As noted in the results from Part 1 above, the soils onsite are not conducive for a full infiltration design. An
onsite percolation study was conducted on the subject property which indicates that the soils underneath
the proposed BMP discharge locations infiltrate at 0.125 inch/hour. The actual depth to groundwater is not
known. A Site Inspection was performed by Soil Testers, Inc., that included borings up to 15 feet in depth
without encountering groundwater. It is not anticipated that the infiltration associated with the selected
BMPs will increase the risk of groundwater contamination.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates.
For further details, please refer to the Site Inspection prepared by Soil Testers, Inc. (September, 2005).
8 Can infiltration be allowed without violating downstream water rights? The response to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
X
Provide basis:
It is not anticipated that the infiltration associated with the selected BMPs will violate any downstream water
rights.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability.
Preliminary research into water rights downstream of the subject property did not yield results that could be
impacted by implementing the selected BMPs.
Part 2 Result*
If all answers from row 1-4 are yes then partial infiltration design is potentially feasible. The feasibility screening category is Partial Infiltration.
If any answer from row 5-8 is no, then infiltration of any volume is considered to be infeasible within the drainage area. The feasibility screening category is No Infiltration.
Partial
Infiltration
*To be completed using gathered site information and best professional judgment considering the definition of MEP in the MS4 Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings.
ATTACHMENT 1E: POLLUTANT CONTROL BMP DESIGN CALCULATIONS
Summary Calculations
DMA A A A,imp A,imp A,per
sq-ft
A,per
ac
imp:perv
Ratio
BMP SD-5
Compliance
Check
(imp:perv <
1.0)
C d** DCV
sq-ft ac sq-ft ac in cu-ft
N1a 1625 0.037 312 0.01 1313 0.03 0.238 No* 0.25 0.59 20
N1b 11917 0.274 3521 0.08 8396 0.19 0.419 No* 0.34 0.59 197
N1a + N1b 13542 0.311 3833 0.09 9709 0.22 0.395 No* 0.33 0.59 217
N1c 605 0.014 0 0.00 605 0.01 0.000 Yes 0.10 0.59 3
N2a 1678 0.039 324 0.01 1354 0.03 0.239 No* 0.25 0.59 21
N2b 11917 0.274 3582 0.08 8335 0.19 0.430 No* 0.34 0.59 199
N2a + N2b 13595 0.312 3906 0.09 9689 0.22 0.403 No* 0.33 0.59 220
N2c 484 0.011 0 0.00 484 0.01 0.000 Yes 0.10 0.59 2
N3 3571 0.082 2202 0.05 1369 0.03 1.608 No 0.59 0.59 104
N4 3571 0.082 1782 0.04 1789 0.04 0.996 Yes 0.50 0.59 88
N5 3571 0.082 2309 0.05 1262 0.03 1.830 No 0.62 0.59 108
N6 3571 0.082 1798 0.04 1773 0.04 1.014 No 0.50 0.59 88
N7 3571 0.082 2172 0.05 1399 0.03 1.553 No 0.59 0.59 103
N8 3571 0.08 1765 0.04 1806 0.04 0.98 Yes 0.50 0.59 87
49652 1.14 19767 0.45 29885 0.69 0.66
0.42 0.59 1022
* = DMAs 1 and 2 meet the BMP SD-5 water quality requirement in terms of imp:perv ratio, however the DCV reduction associated with BMP SD-5 has
not been counted because a significant portion of the receiving permeable area is sloped greater than 5%.
** d is the depth of precipitation produced by the 85th percentile storm event (P85 = 0.59 inches)
Linear Interpolation for C Factor Adjustment -- Hydrologic Soils Group B)
DMA imp:perv
Ratio
imp:perv
Ratio <=1
imp:perv
Ratio =2
Adjustment Adjustment Adjustment
Factor -- Low Factor -- High Factor
N1a 0.238 0.00 0.27 1 2 0.000
N1b 0.419 0.00 0.27 1 2 0.000
N1a + N1b 0.395 0.00 0.27 1 2 0.000
N1c 0.000 0.00 0.27 1 2 0.000
N2a 0.239 0.00 0.27 1 2 0.000
N2b 0.430 0.00 0.27 1 2 0.000
N2a + N2b 0.403 0.00 0.27 1 2 0.000
N2c 0.00 0.00 0.27 1 2 0.000
N3 1.61 0.00 0.27 1 2 0.164
N4 1.00 0.00 0.27 1 2 0.000
N5 1.83 0.00 0.27 1 2 0.224
N6 1.01 0.00 0.27 1 2 0.004
N7 1.55 0.00 0.27 1 2 0.149
N8 0.98 0.00 0.27 1 2 0.000
Summary Calculations Continued
DMA
imp:perv
Ratio
Adj. Adj. C
Adj. DCV
(via SD-
5)
Trees
(d = 5 ft)
TCV
(d = 5 ft)
Trees
(d =
10 ft)
TCV
(d = 10
ft)
Total
TCV
Adj.
DCV
(via
SD-5) WQ Compliant?
Factor cu-ft #
cu-
ft/tree #
cu-
ft/tree cu-ft cu-ft
N1a 0.238 N/A, slopes too steep for SD-5 20.26 N/A, DMA N1a is treated by BMP PR-1a
N1b 0.419 N/A, slopes too steep for SD-5 197.08 N/A, DMA N1b is treated by BMP PR-1a
N1a + N1b 0.395 N/A, slopes too steep for SD-5 217.35 N/A, DMAs N1a and N1b are treated by BMP PR-1a
N1c 0.000 N/A, slopes too steep for SD-5 2.97 N/A, DMA N1c is a Self-Mitigated Area -- SMA-1
N2a 0.239 N/A, slopes too steep for SD-5 20.99 N/A, DMA N2a is treated by BMP PR-1b
N2b 0.430 N/A, slopes too steep for SD-5 199.48 N/A, DMA N2b is treated by BMP PR-1b
N2a + N2b 0.403 N/A, slopes too steep for SD-5 220.48 N/A, DMAs N2a and N2b are treated by BMP PR-1b
N2c 0.00 N/A, slopes too steep for SD-5 2.38 N/A, DMA N2c is a Self-Mitigated Area -- SMA-2
N3 1.61 0.16 0.13 22.74 1.00 40.00 40.00 -17.26 Yes
N4 1.00 N/A, SD-5 alone is sufficient 87.65 N/A, DMA N4 is fully treated by BMP SD-5 (Impervious Area Dispersion)
N5 1.83 0.22 0.17 29.09 1.00 40.00 40.00 -10.91 Yes
N6 1.01 0.00 0.05 9.02 1.00 10.00 10.00 -0.98 Yes
N7 1.55 0.15 0.12 21.22 1.00 40.00 40.00 -18.78 Yes
N8 0.98 N/A, SD-5 alone is sufficient 86.98 N/A, DMA N8 is fully treated by BMP SD-5 (Impervious Area Dispersion)
Total Adjusted DCV = 793 cu-ft Total TCV = 130.00 cu-ft
Total TCV = 130 cu-ft which is less than 25% of DCV
-25% of DCV = 0.25 * DCV = 0.25* 1115 cu-ft --> 25% of DCV = 278.80 cu-ft > TCV = 130 cu-ft --> OK
Total TCV = 150 cu-ft which is also less than 25% of the Adjusted DCV
-25% of Adjusted DCV = 0.25 * DCV = 0.25* 793 cu-ft --> 25% of DCV =
Bioretention BMP Summary
198.36
cu-ft > TCV = 130 cu-ft --> OK
DMA A,BMP A,req 3%
Inf. Rate Inf. Depth
A,bot h,pond h,am h,gr
V,BMP
(retained)
V,BMP
(retained)
> 0.375 *
DCV?
sf sf Check in/hr In sf ft ft ft cu-ft Fraction of DCV WQ Compliant?
N1a + N1b 318 133 OK 0.063 2.25 77 0.50 1.5 1 107 0.494 Yes
N2a + N2b 297 135 OK 0.063 2.25 72 0.50 1.5 1 100 0.455 Yes
I
Table 4. DMA Summary
A B C D
DMA ID
Structural
BMP ID(s)
that
Provide
Pollutant
Control
Structural BMP
ID(s) that Provide
Hydromodification
(Flow) Control
No BMPs:
Self-
Mitigating
DMA1
No
BMPs:
De
Minimis
DMA2
Self-
Retaining
DMA
Treated
Using
Only Site
Design3
Total
Area
(sq-ft)
Total
Area
(acre)
Imp
Area
(sq-ft)
Imp
Area
(acre)
Imp
Area
(%)
Perv
Area
(sq-ft)
Perv
Area
(acre)
Perv
Area
(%)
Runoff
Factor (C)
N1a 1625 0.04 312 0.01 0.19 1313 0.03 0.81 0.254
N1b 11917 0.27 3521 0.08 0.30 8396 0.19 0.70 0.336
N1a + N1b 13542 0.31 3833 0.09 0.28 9709 0.22 0.72 0.326
N1c 605 0.01 0 0.00 0.00 605 0.01 1.00 0.100
N2a 1678 0.04 324 0.01 0.19 1354 0.03 0.81 0.254
N2b 11917 0.27 3582 0.08 0.30 8335 0.19 0.70 0.340
N2a + N2b 13595 0.31 3906 0.09 0.29 9689 0.22 0.71 0.330
N2c 484 0.01 0 0.00 0.00 484 0.01 1.00 0.100
N3 3571 0.08 2202 0.05 0.62 1369 0.03 0.38 0.593
N4 3571 0.08 1782 0.04 0.50 1789 0.04 0.50 0.499
N5 3571 0.08 2309 0.05 0.65 1262 0.03 0.35 0.617
N6 3571 0.08 1798 0.04 0.50 1773 0.04 0.50 0.503
N7 3571 0.08 2172 0.05 0.61 1399 0.03 0.39 0.587
N8 3571 0.08 1765 0.04 0.49 1806 0.04 0.51 0.495
49653 1.14 22146 0.51 0.45 27507 0.63 0.55 0.457
1. See BMP Design Manual Section 5.2.1 for characteristics required to qualify.
2. See BMP Design Manual Section 5.2.2 for characteristics required to qualify.
3. See BMP Design Manual Section 5.2.3. If this option is selected, the site design BMPs must be shown to achieve a DCV of 0 using the
DMA Summary Worksheet
Table 6. Structural BMP Summary Table
BMP ID No.
Structural BMP Type
(Select from the list below this table)
Purpose(s)
DMA(s)
draining to
BMP
Construction Plan Sheet
No(s). Pollutant Control Hydromodification Control BMP-PR-1a Biofiltration with Partial Retention (PR-1a) N1a & N1b DWG 483-6D, Sheet No. 3
BMP-PR-1b Biofiltration with Partial Retention (PR-1b) N2a & N2b DWG 483-6D, Sheet No. 4
Structural BMP Types:
• Harvest and use (HU-1) • Biofiltration (without retention) (BF-1)
• Infiltration basin (INF-1) • Biofiltration with Nutrient Sensitive Media Design (BF-2)
• Bioretention (INF-2) • Detention pond or vault for hydromodification management
• Permeable pavement (INF-3) • Other (describe)
• Biofiltration with partial retention (PR-1)
Notes
• Proprietary Biofiltration (BF-3) can only be used if it meets the requirements of Appendix F
• Flow-thru treatment control BMPs, unless used solely for pre-treatment, may only be used as part of an alternative compliance
program. See Section 1.8 of the BMP Design Manual for more information.
Pre-treatment BMPs
All structural BMPs that will be used for pre-treatment purposes only are described below, including the type of BMP and
which of the BMPs from the table above it provides pre-treatment for. Sizing calculations are included in Appendix E.
There are not any Pretreatment BMPs proposed at the project.
Appendix C.3 DMA Design Capture Volume Calculations
85th Percentile Rainfall (inches): 0.59
DMA ID: N1a
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: sidewalks, driveway
draining to BMP 312 0.90 None Claimed N/A 1 0.9 N/A N/A 114
B Pervious: Landscape draining to BMP 1,313 0.10 None Claimed N/A 1 0.1 N/A N/A 6
Total DMA Area (ft2) 1,625
Weighted Average C Factor for DMA 0.25 Total DCV for DMA (ft3) 20
85th Percentile Rainfall (inches): 0.59
DMA ID: N1b
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 3,521 0.90 None Claimed N/A 1 0.9 N/A N/A 156
B Pervious: Landscape draining to BMP 8,396 0.10 None Claimed N/A 1 0.1 N/A N/A 41
Total DMA Area (ft2) 11,917
Weighted Average C Factor for DMA 0.34 Total DCV for DMA (ft3) 197
85th Percentile Rainfall (inches): 0.59
DMA ID: N1a & N1b
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 3,833 0.90 None Claimed N/A 1 0.9 N/A N/A 170
B Pervious: Landscape draining to BMP 9,709 0.10 None Claimed N/A 1 0.1 N/A N/A 48
Total DMA Area (ft2) 13,542
Weighted Average C Factor for DMA 0.33 Total DCV for DMA (ft3) 217
85th Percentile Rainfall (inches): 0.59
DMA ID: N1c
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: N/A 0 0.90 Runoff Dispersion
(SD-5) 0.00 1 0.9 N/A N/A 0
B Pervious: Landscaping 605 0.10 None Claimed N/A 1 0.1 N/A N/A 3
Total DMA Area (ft2) 605
Weighted Average C Factor for DMA 0.10 Total DCV for DMA (ft3) 3
It is important to note that the ai:ap ratio for DMA N1c is less than 1 and therefore the DMA can be fully treated with Impervious Dispersion (BMP SD-5)
85th Percentile Rainfall (inches): 0.59
DMA ID: N2a
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: sidewalks, driveway
draining to BMP 324 0.90 None Claimed N/A 1 0.9 N/A N/A 14
B Pervious: Landscape draining to BMP 1,354 0.10 None Claimed N/A 1 0.1 N/A N/A 7
Total DMA Area (ft2) 1,678
Weighted Average C Factor for DMA 0.25 Total DCV for DMA (ft3) 21
85th Percentile Rainfall (inches): 0.59
DMA ID: N2b
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 4,545 0.90 None Claimed N/A 1 0.9 N/A N/A 159
B Pervious: Landscape draining to BMP 7,372 0.10 None Claimed N/A 1 0.1 N/A N/A 41
Total DMA Area (ft2) 11,917
Weighted Average C Factor for DMA 0.34 Total DCV for DMA (ft3) 199
85th Percentile Rainfall (inches): 0.59
DMA ID: N2a & N2b
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 3,906 0.90 None Claimed N/A 1 0.9 N/A N/A 173
B Pervious: Landscape draining to BMP 9,689 0.10 None Claimed N/A 1 0.1 N/A N/A 48
Total DMA Area (ft2) 13,595
Weighted Average C Factor for DMA 0.33 Total DCV for DMA (ft3) 220
85th Percentile Rainfall (inches): 0.59
DMA ID: N2c
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: N/A 0 0.90 Runoff Dispersion
(SD-5) 0.00 1 0.9 N/A N/A 0
B Pervious: Landscaping 484 0.10 None Claimed N/A 1 0.1 N/A N/A 2
Total DMA Area (ft2) 484
Weighted Average C Factor for DMA 0.10 Total DCV for DMA (ft3) 2
It is important to note that the ai:ap ratio for DMA N2c is less than 1 and therefore the DMA can be fully treated with Impervious Dispersion (BMP SD-5)
85th Percentile Rainfall (inches): 0.59
DMA ID: N3
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 2,202 0.90 Runoff Dispersion
(SD-5) 1.608 0.16 0.15 40.00 N/A -24
B Pervious: Landscaping 1,369 0.10 NA (Pervious) N/A N/A 0.1 N/A N/A 7
Total DMA Area (ft2) 3,571
Weighted Average C Factor for DMA 0.13 Total DCV for DMA (ft3) -17
85th Percentile Rainfall (inches): 0.59
DMA ID: N4
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building & sidewalks
draining to BMP 1,782 0.90 Runoff Dispersion
(SD-5) 0.996 1.00 0.90 N/A N/A 79
B Pervious: Landscaping 1,789 0.10 NA (Pervious) N/A N/A 0.1 N/A N/A 9
Total DMA Area (ft2) 3,571
Weighted Average C Factor for DMA 0.50 Total DCV for DMA (ft3) 88
It is important to note that the ai:ap ratio for DMA N4 is less than 1 and therefore the DMA can be fully treated with Impervious Dispersion (BMP SD-5)
85th Percentile Rainfall (inches): 0.59
DMA ID: N5
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 2,309 0.90 Runoff Dispersion
(SD-5) 1.83 0.22 0.20 40.00 N/A -17
B Pervious: Landscaping 1,262 0.10 NA (Pervious) N/A N/A 0.1 N/A N/A 6
Total DMA Area (ft2) 3,571
Weighted Average C Factor for DMA 0.17 Total DCV for DMA (ft3) -11
85th Percentile Rainfall (inches): 0.59
DMA ID: N6
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building & sidewalks
draining to BMP 1,798 0.90 Runoff Dispersion
(SD-5) 1.01 0.004 0.00 10.00 N/A -10
B Pervious: Landscaping 1,773 0.10 NA (Pervious) N/A N/A 0.1 N/A N/A 9
Total DMA Area (ft2) 3,571
Weighted Average C Factor for DMA 0.05 Total DCV for DMA (ft3) -1
85th Percentile Rainfall (inches): 0.59
DMA ID: N7
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building, sidewalks,
driveway draining to BMP 2,172 0.90 Runoff Dispersion
(SD-5) 1.55 0.15 0.14 40.00 N/A -26
B Pervious: Landscaping 1,399 0.10 NA (Pervious) N/A N/A 0.1 N/A N/A 7
Total DMA Area (ft2) 3,571
Weighted Average C Factor for DMA 0.12 Total DCV for DMA (ft3) -19
85th Percentile Rainfall (inches): 0.59
DMA ID: N8
Hydrolog
ic Soil
Group
(A, B, C,
or D)
Post-Project Surface Type
(See Table B.1-1)
Area of
Surface
Type
(ft2)
Post-Project
Surface Runoff
Factor (C)
(See Table B.1-1)
Runoff Reduction
from Site Design
BMPs
(Select Only One)
Tributary
Impervious/
Receiving
Pervious
Area Ratio1
C Factor
Adjustment2
(See Table
B.2-1)
Final C
Factor
Street Tree
Volume
Reduction3
(ft3)
Rain Barrel
Volume
Reduction4
(ft3)
Design
Capture
Volume
(DCV)5
(ft3)
B Impervious: building & sidewalks
draining to BMP 1,765 0.90 Runoff Dispersion
(SD-5) 0.977 0.02 0.02 N/A N/A 2
B Pervious: Landscaping 1,806 0.10 NA (Pervious) N/A N/A 0.1 N/A N/A 9
Total DMA Area (ft2) 3,571
Weighted Average C Factor for DMA 0.06 Total DCV for DMA (ft3) 10
It is important to note that the ai:ap ratio for DMA N8 is less than 1 and therefore the DMA can be fully treated with Impervious Dispersion (BMP SD-5)
Notes
1. If the area is pervious or if runoff dispersion site design BMPs are not proposed, enter "NA".
2. If the area is pervious or if runoff dispersion site design BMPs are not proposed, enter "1" in this column.
3. Include a separate line item in this table for each street tree and its tributary drainage area, or include supplemental information to demonstrate
that the 85th percentile runoff of the impervious area draining to each street tree does not exceed the volume reduction credit being claimed for
each street tree. Also include supplemental information documenting the mature tree canopy size of the street tree. Trees must be implemented
in accordance with SD-1. Total tree volume reduction must be less than 0.25 times the DCV for the entire project, and each single tree volume
credit must be less than 400 cu-ft (see Appendix B.2.2.1 for more information).
4. To be granted a credit here, rain barrels must meet the standards described in Section B.2 and fact sheet SD-8. Enter credit in cubic feet, not
gallons.
5. DCV = (Final C Factor) x (85th Percentile Rainfall)/12 x (Area of Surface Type) - (Street Tree Volume Reduction) - (Rain Barrel Volume Reduction).
Note that only one Site Design volume reduction credit can be applied for each area, however. For example, runoff dispersion and rain barrel
volume reduction cannot both be claimed for the same line item area.
Table D.5‐1: Suitability Assessment Related Considerations for Infiltration Facility Safety Factors
Consideration High Concern – 3 points
Medium Concern –2
points Low Concern – 1 point
Assessment methods
Use of soil survey maps or
simple texture analysis to
estimate short‐term
infiltration rates
Use of well permeameter
or borehole methods with
accompanying continuous
boring log
Direct measurement with
localized (i.e., small‐scale)
infiltration testing methods at
relatively high resolution1
(see explanation
below)
Use of well permeameter
or borehole methods
without accompanying
continuous boring log
Direct measurement of
infiltration area with
localized infiltration
measurement methods
(e.g., infiltrometer) or
Relatively sparse testing
with direct infiltration
methods
Moderate spatial
resolution
Use of extensive test pit
infiltration measurement
methods2
Texture Class
Silty and clayey soils with
significant fines Loamy soils
Granular to slightly loamy
soils
Site soil variability
Highly variable soils
indicated from site
assessment, or
Soil borings/test pits
indicate moderately
homogeneous soils
Soil borings/test pits indicate
relatively homogeneous soils Unknown variability
Depth to
groundwater/
impervious layer <5 ft below facility bottom
5‐15 ft below facility
bottom >15 below facility bottom
1 ‐ Localized (i.e., small scale) testing refers to methods such as the double‐ring infiltrometer and
borehole tests. A relatively high resolution generally means two or more tests directly within the
proposed BMP’s footprint.
2 ‐ Extensive infiltration testing refers to methods that include excavating a significant portion of the
proposed infiltration area, filling the excavation with water, and monitoring drawdown. The excavation
should be to the depth of the proposed infiltration surface and ideally be at least 30 to 100 square feet.
Form I‐9/Worksheet D.5‐1: Factor of Safety and Design Infiltration Rate Worksheet
Factor of Safety and Design Infiltration Rate
Worksheet Form I‐9
Factor Category Factor Description
Assigned
Weight
(w)
Factor
Value1 (v)
Product
(p)
p = w x
v
A Suitability
Assessment
Soil assessment methods 0.25 3 0.75
Predominant soil texture 0.25 3 0.75
Site soil variability 0.25 2 0.5
Depth to groundwater / impervious layer 0.25 2 0.5
Suitability Assessment Safety Factor, SA = p 2.5
B Design
Level of pretreatment/ expected sediment
loads 0.5 3 1.5
Redundancy/ resiliency 0.25 3 0.75
Compaction during construction 0.25 3 0.75
Design Safety Factor, SB = p 3
Combined Safety Factor, Stotal= SA x SB 2
Observed Infiltration Rate, inch/hr, Kobserved 0.125 (corrected for test‐specific bias)
Design Infiltration Rate, in/hr, Kdesign = Kobserved / Stotal 0.0625
Supporting Data
Briefly describe infiltration test and provide reference to test forms:
Although the analysis indicates that the safety factor should be 7.5, the BMP Design Manual (Appendix
D.5.4 recommends a maximum safety factor of 2.0, which has been implemented into the design).
Additionally, an onsite percolation study was conducted on the subject property which indicates that
the soils underneath the proposed Biofiltration with Partial Retention Basin infiltrate at 0.125 inch/hour
(please note that the soils near the proposed tree wells infiltrate at significantly higher rates – from 2.9‐
up to 6.0 in/hr). For further details, please refer to the Percolation Test Results prepared by
Construction Testing & Engineering, Inc. (March, 2016), included under Appendix E of this SWQMP.
Note
1. Factor values are assigned per Table D.5‐1 in the BMP Design Manual.
Worksheet B.5‑1: Simple Sizing Method for Biofiltration BMPs
Simple Sizing Method for Biofiltration BMPs
BMP ID IDs of Tribuary DMAs
PR-1a DMAs N1a & N1b
1a 217 ft3
1b 0 ft3
1 217 ft3
2 0.063 in/hr
3 36 hr
4 2.25 in
5 0.4 in/in
6 5.63 in
7 318 ft2
8 0.1 in/in
9 107 ft3
10 110 ft3
11 6 in
12 18 in
13 6 in
14 0.2 in/in
15 5 in/hr.
16 6 hr
17 30 in
18 12 in
19 42 in
20 165 ft3
21 47 ft2
22 239 ft3
23 239 ft2
24 13542 ft2
25 0.33
Allowable drawdown time for aggregate storage below the underdrain
Volume reduction from implementation of retention BMPs
Remaining DCV after implementing retention BMPs (Line 1a - Line 1b)
Total DCV of tributary DMAs
Initial Information
IDs of Retention BMPs Treating the Same DMAs
N/A
Partial Retention
Infiltration rate from Worksheet D.5-1 if partial infiltration is feasible
Soil Media available pore space
Depth of runoff that can be infiltrated [Line 2 x Line 3]
Aggregate pore space
Required depth of gravel below the underdrain [Line 4/ Line 5]
Assumed surface area of the biofiltration BMP
Media retained pore storage
Volume retained by BMP [[[Line 4 + (Line 12 x Line 8)]/12] x Line 7]
DCV that requires biofiltration [Line 1 – Line 9]
BMP Parameters
Surface Ponding [6 inch minimum, 12 inch maximum]
Soil Media Thickness [18 inches minimum], also add mulch layer thickness to
this line for sizing calculations
Aggregate Storage above underdrain invert
Required Storage (surface + pores) Volume [0.75 x Line 10]
Soil Media filtration rate to be used for sizing (5 in/hr. with no outlet control;
if the filtration rate is controlled by the outlet use the outlet controlled rate)
Baseline Calculations
Allowable Routing Time for sizing
Depth filtered during storm [ Line 15 x Line 16]
Depth of Detention Storage
[Line 11 + (Line 12 x Line 14) + (Line 13 x Line 5)]
Total Depth Treated [Line 17 + Line 18]
Option 1 – Biofilter 1.5 times the DCV
Required biofiltered volume [1.5 x Line 10]
Required Footprint [Line 20/ Line 19] x 12
Option 2 - Store 0.75 of remaining DCV in pores and ponding
Required Footprint [Line 22/ Line 18] x 12
Footprint of the BMP
Area draining to the BMP
Adjusted Runoff Factor for drainage area (Refer to Appendix B.1 and B.2)
26 0.03 unitless
27 133 ft2
28 133 ft2
29 0.494 unitless
30 0.375 unitless
Notes
1. Line 7 is used to estimate the amount of volume retained by the BMP. Update assumed surface area in Line 7 until its equivalent
to the required biofiltration footprint (either Line 21 or Line 23)
2. The DCV fraction of 0.375 is based on a 40% average annual percent capture and a 36-hour drawdown time.
3. The increase in footprint for volume reduction can be optimized using the approach presented in Appendix B.5.2. The optimized
footprint cannot be smaller than the alternative minimum footprint sizing factor from Worksheet B.5-2.
4. If the proposed biofiltration BMP footprint is smaller than the alternative minimum footprint sizing factor from Worksheet B.5-
2, but satisfies Option 1 or Option 2 sizing, it is considered a compact biofiltration BMP and may be allowed at the discretion of the
[City Engineer], if it meets the requirements in Appendix F.
BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum footprint
sizing factor from Worksheet B.5-2, Line 11)
Minimum BMP Footprint [Line 24 x Line 25 x Line 26]
Footprint of the BMP = Maximum(Minimum(Line 21, Line 23), Line 27)
Calculate the fraction of the DCV retained by the BMP [Line 9/ Line 1]
Minimum required fraction of DCV retained for partial infiltration condition
31 Yes ☐ No
Is the retained DCV > 0.375? If the answer is no increase the footprint sizing
factor in Line 26 until the answer is yes for this criterion
Worksheet B.5‑1: Simple Sizing Method for Biofiltration BMPs
Simple Sizing Method for Biofiltration BMPs
BMP ID IDs of Tribuary DMAs
PR-1b DMAs N2a & N2b
1a 220 ft3
1b 0 ft3
1 220 ft3
2 0.063 in/hr
3 36 hr
4 2.25 in
5 0.4 in/in
6 5.63 in
7 297 ft2
8 0.1 in/in
9 100 ft3
10 120 ft3
11 6 in
12 18 in
13 6 in
14 0.2 in/in
15 5 in/hr.
16 6 hr
17 30 in
18 12 in
19 42 in
20 180 ft3
21 52 ft2
22 223 ft3
23 223 ft2
24 13595 ft2
25 0.33
IDs of Retention BMPs Treating the Same DMAs
N/A
Initial Information
Total DCV of tributary DMAs
Volume reduction from implementation of retention BMPs
Remaining DCV after implementing retention BMPs (Line 1a - Line 1b)
Partial Retention
Infiltration rate from Worksheet D.5-1 if partial infiltration is feasible
Allowable drawdown time for aggregate storage below the underdrain
Depth of runoff that can be infiltrated [Line 2 x Line 3]
Aggregate pore space
Required depth of gravel below the underdrain [Line 4/ Line 5]
Assumed surface area of the biofiltration BMP
Media retained pore storage
Volume retained by BMP [[[Line 4 + (Line 12 x Line 8)]/12] x Line 7]
DCV that requires biofiltration [Line 1 – Line 9]
BMP Parameters
Surface Ponding [6 inch minimum, 12 inch maximum]
Soil Media Thickness [18 inches minimum], also add mulch layer thickness to
this line for sizing calculations
Aggregate Storage above underdrain invert
Soil Media available pore space
Soil Media filtration rate to be used for sizing (5 in/hr. with no outlet control;
if the filtration rate is controlled by the outlet use the outlet controlled rate)
Baseline Calculations
Allowable Routing Time for sizing
Depth filtered during storm [ Line 15 x Line 16]
Depth of Detention Storage
[Line 11 + (Line 12 x Line 14) + (Line 13 x Line 5)]
Total Depth Treated [Line 17 + Line 18]
Option 1 – Biofilter 1.5 times the DCV
Required biofiltered volume [1.5 x Line 10]
Required Footprint [Line 20/ Line 19] x 12
Option 2 - Store 0.75 of remaining DCV in pores and ponding
Required Storage (surface + pores) Volume [0.75 x Line 10]
Required Footprint [Line 22/ Line 18] x 12
Footprint of the BMP
Area draining to the BMP
Adjusted Runoff Factor for drainage area (Refer to Appendix B.1 and B.2)
26 0.03 unitless
27 135 ft2
28 135 ft2
29 0.455 unitless
30 0.375 unitless
BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum
footprint sizing factor from Worksheet B.5-2, Line 11)
Minimum BMP Footprint [Line 24 x Line 25 x Line 26]
Footprint of the BMP = Maximum(Minimum(Line 21, Line 23), Line 27)
Calculate the fraction of the DCV retained by the BMP [Line 9/ Line 1]
Minimum required fraction of DCV retained for partial infiltration condition
31
Is the retained DCV > 0.375? If the answer is no increase the footprint sizing
factor in Line 26 until the answer is yes for this criterion Yes ☐ No
Notes
1. Line 7 is used to estimate the amount of volume retained by the BMP. Update assumed surface area in Line 7 until its equivalent
to the required biofiltration footprint (either Line 21 or Line 23)
2. The DCV fraction of 0.375 is based on a 40% average annual percent capture and a 36-hour drawdown time.
3. The increase in footprint for volume reduction can be optimized using the approach presented in Appendix B.5.2. The optimized
footprint cannot be smaller than the alternative minimum footprint sizing factor from Worksheet B.5-2.
4. If the proposed biofiltration BMP footprint is smaller than the alternative minimum footprint sizing factor from Worksheet B.5-2,
but satisfies Option 1 or Option 2 sizing, it is considered a compact biofiltration BMP and may be allowed at the discretion of the
[City Engineer], if it meets the requirements in Appendix F.
ATTACHMENT 2
BACKUP FOR PDP HYDROMODIFICATION CONTROL MEASURES
[This is the cover sheet for Attachment 2.]
Indicate which Items are Included behind this cover sheet:
Attachment
Sequence
Contents Checklist
Attachment 2a Hydromodification Management
Exhibit (Required) Included
See Hydromodification Management
Exhibit Checklist on the back of this Attachment cover sheet.
Attachment 2b Management of Critical Coarse Sediment Yield Areas (WMAA Exhibit
is required, additional analyses are
optional)
See Section 6.2 of the BMP Design
Manual.
Exhibit showing project drainage boundaries marked on WMAA Critical Coarse Sediment Yield
Area Map (Required)
Optional analyses for Critical Coarse
Sediment Yield Area Determination
6.2.1 Verification of Geomorphic Landscape Units Onsite
6.2.2 Downstream Systems
Sensitivity to Coarse Sediment
6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite
Attachment 2c Geomorphic Assessment of Receiving Channels (Optional)
See Section 6.3.4 of the BMP Design Manual.
Not performed
Included
Attachment 2d Flow Control Facility Design and Structural BMP Drawdown
Calculations (Required)
See Chapter 6 and Appendix G of the BMP Design Manual
Included
N/A
~
~
□
□
□
~
□
□
~
ATTACHMENT 2A: HYDROMODIFICATION MANAGEMENT EXHIBIT
Please note that the site is located in a hydromodification exempt area and is therefore exempt from the
City’s hydromod requirements. Any of the typical items required on the Hydromodification Management Exhibit that are relevant to this project have been included on the DMA Exhibit under SWQMP
Attachment 1A. For further details, please refer to the Hydromodification Exemption Exhibits below:
HYDROMODIFICATION MANAGEMENT EXHIBIT
Source: Hydromodification Exemption Analyses for select Carlsbad Watersheds prepared by Chang Consultants
(September, 2015).
--~ OAA'.flN3E SASllf 90U+CAA:Y
•••• 11..0'# f>AlW
,// ,' !fftJ!OllQlRCA~ ()tlilPi AAf.A
HYDROMODIFICATION MANAGEMENT EXEMPTION MAP
Source: Receiving Waters and Conveyance Systems Exempt form hydromodification Management Requirements prepared by
Geosyntec and Consultants and Rick Engineering (09/08/2014) included under Attachment B.4 of the Carlsbad Watershed Management Area Analysis (WMAA)
Watershed Boundaries
Q Municipol loundmies
llegionol WMM Streams
-Exemptlk>dies: Wolref Slofage IM«'-l'On, lakes,
fnelos.ed Emboymem. l'OCific ocean. 8uenD VlSlo lagoon
~Exempt liver lie-aches:
boches of son tuis 1:ey liver. son ~ liver, son Oiegoliver,
foresle-raeek,.sweet-Nah!JIIM!r.
Olay ....
--Exempt Conveyance Sys:lems:
Exismg undergound storm <i'<Jm or
~ chaWM!ls 'MH>5e bed
and bank me conaete-ined,
dischmgmQ di'ecly lo exempt waler bodies. exempt riwrs, or localzed
a-eosof AgU<Jffedondot.agoonmld --
Carlsbad Watershed Management Area
HU 904.00, 211 mi2
Receiving Waters and Conveyance Systems Exempt
from Hydromodification Management Requirements
2.5 10 Mlle, ~
Exhibtt Dale: Sept. 8, 2014 Ge~~~!~" "''"•' n ~
ATTACHMENT 2B: CRITICAL COARSE SEDIMENT YEILD AREA MAP
Please note that the site is located outside of the noted critical coarse sediment yield areas and therefore
exempt from the City’s critical coarse sediment yield requirements. For further details, please refer to the Critical Coarse Sediment Yield Area Map below:
Critical Coarse Sediment Yield Area Map
Source: Potential Critical Coarse Sediment Yield Areas Map prepared by Geosyntec and Consultants and Rick Engineering (09/08/2014) included under Attachment A.4 of the Carlsbad Watershed Management Area Analysis (WMAA)
Watershed Boundaries
Q Municipal Boundaries
--liven l Streams
-l~nal WMAAStreams
,-7 ,_____7_
Potential Critical Coarse Sediment Yield Areas
Carlsbad Watershed -HU 904.00, 211 mi2
:.
l.:a ltd t •~~Ir,
GeosyntecC> 1;f1118 Il
Exhibit Date: Sept. 8, 2014 <'on.'4!J1ams t-o, "~ p--H~, L
ATTACHMENT 3
City Standard Single Sheet BMP (SSBMP) Exhibit
0SCALE: 1" =FEET202010408020HIGHLAND JAMES SUBDIVISION111234232444333112244321555555555512"12"18"TOP OF SLOPE WIDTHBASIN BOTTOM WIDTHAMENDED SOILS WIDTH30 MIL IMPERMEABLE LINERINSTALLED VERTICALLYSEE GRADING PLANSFOR DIMENSIONSGRADED WEIR.SEE DETAIL BELOW.AMENDED SOILGRAVELNATIVE SOILFLOW CONVEYS TODOWNSTREAMCONCRETE SWALE.3" PONDING FOR POLLUTANT CONTROL6"3:13:11. THESE BMPS ARE MANDATORY TO BE INSTALLED PERMANUFACTURER'S RECOMMENDATIONS OR THESE PLANS.2. NO CHANGES TO THE PROPOSED BMPS ON THIS SHEETWITHOUT PRIOR APPROVAL FROM THE CITY ENGINEER.3. NO SUBSTITUTIONS TO THE MATERIAL OR TYPES OR PLANTINGTYPES WITHOUT PRIOR APPROVAL FROM THE CITY ENGINEER.4. NO OCCUPANCY WILL BE GRANTED UNTIL THE CITY INSPECTIONSTAFF HAS INSPECTED THIS PROJECT FOR APPROPRIATE BMPCONSTRUCTION AND INSTALLATION.5. REFER TO MAINTENANCE AGREEMENT DOCUMENT.6. SEE PROJECT SWMP FOR ADDITIONAL INFORMATION.5'3'3"SCALE:1BIORETENTION BMP DETAILNTSARBOR GUARDMODEL # AG8-4TURF AREAS ONLY:PLAN VIEWTREE CANOPY(2) CINCH TIES, TACK TO STAKE WITH GALVANIZED NAILS TO PREVENT SLIPPING(2) 2" DIA. X 8' LONG UNTREATED LODGEPOLE PINE STAKES FOR 5 GAL. TREES, OR(2) 2" DIA. X 10' LONG UNTREATED LODGEPOLE PINE TAKES FOR 15 GAL.- 36" BOX TREES,SET STAKES OUTSIDE ROOTBALL. ANGLE TOP OF STAKE AWAY FROM BRANCH STRUCTURE.TREE TRUNK1 X 4 DOUG. FIR BRACE, TACK TO LODGEPOLE STAKES WITH GALV. NAILSROOT BALL, DO NOT PENETRATE WITH STAKE.TREE TIE NOTE:1. INSTALL TREE TIES AND STAKES ONLY TO PROPER LEVEL TO HOLDTREE UPRIGHT. PROPER HEIGHT IS 6" ABOVE POINT WHERE THE TREEWILL SNAP TO AN UPRIGHT POSITION BY ITSELF IF TOP IS PULLED TOONE SIDE AS IF WIND LOADED AND THEN RELEASED. DO NOT TOPTREES IN ORDER TO REDUCE SIZE OR WEIGHT OF TREE CROWN,CONTACT LANDSCAPE ARCHITECT PRIOR TO ANY PRUNING OF TREES. MAX PREVAILING WIND18"12"SECTION VIEWSCALE:2TREE WELL DETAILNTS123456164235123456TREE WELL NOTESSECTION VIEWGRADED SWALE DETAIL3SCALESCALE:CATCH BASIN STENCILING/SIGNAGE1. DMA N1c CONVEYS FLOWS FROM N1a & N1b TOTHE PRIVATE STORM DRAIN SYSTEM.2. DMA N2c CONVEYS FLOW FROM N2a & N2b TOTHE PRIVATE STORM DRAIN SYSTEM.1i ,,1-I I I ~I I r I l • , 3993 HIGHLAND DRIVE -,-) 3990 HIGHLAND DRIVE \ f \ 0 \... ---Nlc 0.014 ac ------1 I \ 7 \ ----• . " ... 4·. •· . Nlb • • • • • 3985 HIGHLAND DRIVE /r J • • • • • • • • • • • • • .. 4 / •• • . •· -6 J_ I I I !~,: ' I I I --+-~l---:=,-1~1 EX ~ ,-EX DWY DWY 0.038 ac \ N2c 0.011 ac 0 N8 0.082 ac 3971 JAMES DRIVE .. • LEGEND / (E) : EXISTING , (NJ: NEW/ PROPOSED / --- -- ---(E) PROPERTY LINE / - - - - - - -(E) MAJOR CONTOUR ' (E) MINOR CONTOUR (E) CURB & GUTTER (E) STRIPING (NJ MAJOR CONTOUR (NJ MINOR CONTOUR ---12" SD--12" SD--(E) 12" RCP STORM DRAIN PIPE ---18" SD--18" SD-----48" SD--48" SD--(E) 18" RCP STORM DRAIN PIPE (E) 48" RCP STORM DRAIN PIPE § (E) STORM DRAIN INLET 0--b]-1··.· ... :1---• • • . . . m1-·-· _· --4" SD -6" SD -8" SD -10" SD -18" SD --4" SD --6" SD --8" SD --10" SD --18" SD Cl 0 0-0----1--Nl ## ac (E) RETAINING WALL (E) CONCRETE (E) VEGETATION (NJ BUILDING (NJ HARDSCAPE (N) LANDSCAPE (NJ BIORETENTION BMP (NJ RETAINING WALL (NJ EARTHEN SWALE FLOWLINE (NJ RIPRAP SWALE (NJ 4" 0 SD PIPE (NJ 6" 0 SD PIPE (NJ 8" 0 SD PIPE (NJ 10" 0 SD PIPE (NJ 18" 0 SD PIPE (NJ SD CATCH BASIN TREE WELL 10' CANOPY TREE WELL 5' CANOPY STREET TREE {IN PUBLIC ROW) DRAINAGE DIRECTION OMA BOUNDARY DMALABEL EASEMENT NOTES • PUBLIC 5.00' WIDE DRAINAGE EASEMENT DEDICATED TO THE CITY OF CARLSBAD ® INDICATES A COVENANT FOR PRIVATE STORM DRAIN EASEMENT TO BENEFIT REMAINDER PARCEL @ INDICATES A COVENANT FOR PRIVATE STORM DRAIN EASEMENT TO BENEFIT LOTS 1, 2, AND REMAINDER PARCEL @ INDICATES A COVENANT FOR PRIVATE STORM DRAIN EASEMENT TO BENEFIT LOT 1 AND REMAINDER PARCEL SWQMP NO. ____ _ PARTY RESPONSIBLE FOR MAINTENANCE: NAME ________ _ ADDRESS _______ _ PHONE NO. ______ _ PLAN PREPARED BY: NAME JASON EVANS COMPANY TERRAMAR ENGINEERING ADDRESS 2888 LOKER AVENUE EAST SUITE 303 CARLSBAD, CA, 92010 PHONE NO. 760-603 -1900 BMP NOTES: CONTACT _____ _ SIGNATURE CERTIFICATION ____ _ .<II --:s:::: \ __, Q -~48" SD--48" SD--48" SD--48" S --9-~ .. 0s~ ~-4;,~SDCfS_ 48" SD--48" i~--48" SD--48" SD-J 48" SD--48" Su_.,... -48" SD--VI VI / ---¥----t j JAMES DRIVE ___ I __ -------;--DMANOTES: 7 ~ ....... \ . ; // BEST MANAGEMENT PRACTICE (BMP) TABLE BMP ID# BMPTYPE SYMBOL CITYBMP# QUANTITY DRAWING NO. INSPECTION/ MAINTENANCE FREQUENCY MONTliLY · INSPECT FOR ERODED SOILS & BUILT UP TRASH AND DEBRIS. ™ INF-2 281 SF DETAIL 1 SEMI-ANNUALLY -INSPECT/REMOVE/REPLACE DAMAGED/DEAD VEGETATION, VEGETATIVE COVER DAMAGED BY EROSION. INF-2A BIORETENTION I----+-----+-----+-----+------+-------< SEMI-ANNUALLY -REMOVE BUil T-UP SEDIMENTS, RE-MULCH VOIDED AREAS, TREAT VEGETATION, MOW TURF AREAS, INF-2B BIORETENTION INF-2 261 SF DETAIL 1 REPAIR EROSION AT INFLOW POINTS, REPAIR DAMAGES TO OUTFLOW STRUCTURE, UNCLOG UNDER-DRAIN AND SMA-1 SMA-2 SRA-1 SRA-2 SRA-3 SRA-4 SRA-5 SRA-6 TW-5' TW-10' SELF-MITIGATING AREA-1 SELF-MITIGATING AREA-2 SELF-RETAINING AREA-1 SELF-RETAINING AREA-2 SELF-RETAINING AREA-3 SELF-RETAINING AREA-4 SELF-RETAINING AREA-5 SELF-RETAINING AREA-6 TREE WELL 5'CANOPY TREE WELL 10'CANOPY b 5 2 I SD-5 605SF I? Z9 SD-5 484SF SD-5 3,571 SF SD-5 3,571 SF SD-5 3,571 SF SD-5 3,571 SF SD-5 3,571 SF SD-5 3,571 SF 0 SD-1 1 EACH • SD-1 3EACH HYDROMODIFICATION & TREATMENT CONTROL NIA NIA NIA NIA NIA NIA NIA NIA DETAIL2 DETAIL2 HYDROMODIFICATION: SITE IS LOCATED IN AN AREA THAT IS HYDROMODIFICATION EXEMPT. REGULA TE SOIL pH ON AN AS-NEEDED BASIS. NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP NOT APPLICABLE -SITE DESIGN BMP TREATMENT CONTROL: TREATMENT CONTROL IS ATTAINED THROUGH A COMBINATION OF SITE DESIGN BMPS (SD-1 & SD-5)AND STRUCTURAL BMPS ( ). LOW IMPACT DESIGN (L.1.D.) WATER QUALITY COMPLIANCE IS BEING ADDRESSED THROUGH A COMBINATION OF SITE DESIGN BMPS (SD-1 & SD-5) AND STRUCTURAL BMPS ( ). SOURCE CONTROL BMP ID# 0 0 0 0 BMPTYPE TRASH STORAGE INTERIOR GARAGE INDOOR PEST CONTROL OUTDOOR PEST CONTROL SYMBOL • ■ ♦ CITYBMP# SC-5 SC-6A SC-6B SC-SC QUANTITY 5EACH 1 PER HOUSE 5EACH 1 PER HOUSE 5EACH 1 PER HOUSE 5EACH 1 PER HOUSE DETAIL NO. NIA NIA NIA NIA INSPECTION FREQUENCY AS NEEDED AS NEEDED AS NEEDED AS NEEDED MAINTENANCE FREQUENCY AS NEEDED AS NEEDED AS NEEDED AS NEEDED 0 INLET STENCILING /SIGNAGE NIA SC-2 11 EACH DETAIL 3 AS NEEDED AS NEEDED NOTES: PLACARD MUST HAVE SIMILAR WORDING" NO DUMPING! DRAINS TO OCEAN". MUST BE CITY APPROVED. □ □ □[ □ □ □ --0 ~ CITY OF CARLSBAD I SHE1ETS I 1----1-----+-----------------t------1---+----+------1 L__l_J ENGINEERING DEPARTMENT 1----l-----+-----------------+------l---+----+------I SWQMP BMP EXHIBIT FOR: RECORD COPY PROJECT NO. DA lE INITIAL DA lE INITIAL DA lE INITIAL DRAWING NO. ENGINEER OF WORK REVISION DESCRIPTION OTHER APPROVAL CITY APPROVAL INITIAL DATE