HomeMy WebLinkAboutCT 2018-0001; WALNUT BEACH HOMES; FINAL - STORM WATER QUALITY MANAGEMENT PLAN; 2018-12-01CITY OF CARLSBAD
PRIORITY DEVELOPMENT PROJECT (PDP)
STORM WATER QUALITY MANAGEMENT PLAN (SWQMP)
FOR
WALNUT BEACH HOMES
362 WALNUT AVENUE
CT 2018-0001 I CDP 2018-0003 / PUD 2018-0001
DWG 513-1A / 2018-0029
ENGINEER OF WORK:
·1 ~7--..-
TYLERGLAWSON, PE #80356
RECEIVE
FEB O 1 7.019
LAND DEVELOPMENT
ENGINEER! G
PREPARED FOR:
RINCON REAL ESTATE GROUP
3005 S. EL CAMINO REAL
SAN CLEMENTE, CA 92672
PH: (949) 438-5494
PREPARED BY:
PASCO, LARET, SUITER & ASSOCIATES
535 N. HWY 101 , SUITE A
SOLANA BEACH, CA 92075
PH: (858) 259-8212
DATE:
JANUARY 2018
REVISED: MARCH 2018
RECORD COPY
Initial Date REVISED: MAY 2018
REVISED: JULY 2018
REVISED: SEPTEMBER 2018
REVISED: NOVEMBER 2018
FINAL: DECEMBER 2018
p__J'tb" J
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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 1 a: OMA Exhibit
Attachment 1 b: Tabular Summary of DMAs and Design Capture Volume Calculations
Attachment 1 c: Harvest and Use Feasibility Screening (when applicable)
Attachment 1 d: Categorization of Infiltration Feasibility Condition (when applicable)
Attachment 1 e: 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 2c: Geomorphic Assessment of Receiving Channels
Attachment 2d: Flow Control Facility Design
Attachment 3: Structural BMP Maintenance Thresholds and Actions
Attachment 4: Single Sheet BMP (SSBMP) Exhibit
Attachment 5: SWMM Model Output and Support Documentation
[Insert City's Storm Water Standard Questionnaire (Form E-34) here]
{ City of
Carlsbad
STORM WATER STANDARDS
QUESTIONNAIRE
Development Services
Land Development Engineering
1635 Faraday Avenue
(760) 602-2750
www .carlsbadca.gov
E-34
J 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: Walnut Beach Homes PROJECT ID: CT 20 18-000 I I CDP 20 18-000
ADDRESS: 362 Walnut Avenue APN : 204-1 32-17-00
The project is (check one): D New Development IZI Redevelopment
The total proposed disturbed area is: 25,020 ft2 ( 0.574 ) acres
The total proposed newly created and/or replaced impervious area is: 10,770 ft2 ( 0.25 ) 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 NIA SWQMP#: NIA
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.
E-34 Page 1 of 4 REV 02/16
3
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 incl udes 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.
STEP2
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; □ IX] b) Designed and constructed to be hydraulically disconnected from paved streets or roads;
c) Designed and constructed with permeable pavements or surfaces in accordance with USEPA
Green Streets quidance?
2. Retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in □ IX] 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.
E-34 Page 2 of 4 REV 04/17
STEP3
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, □ l'.[]
and oublic development oroiects on oublic 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 IX] □ more of impervious surface? This includes commercial, industrial, residential, mixed-use, and public
development orojects 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 □ l'.[]
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 □ IXl
development project includes development on any natural slope that is twenty-five percent or areater.
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
transoortation of automobiles, trucks, motorcvcles, 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 □ IX]
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 comminqled 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 □ IXl 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 (ADTJ of 100 or more vehicles oer dav.
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? □ [X]
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 statina "My project is a 'STANDARD PROJECT' ... " and complete applicant information.
E-34 Page 3 of 4 REV 04/17
STEP4
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) = 3,742 sq. ft. □ ~
Total proposed newly created or replaced impervious area (8) = 10,770 sq. ft.
Percent impervious area created or replaced (8/A)*100 = 288 %
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 "Mv oroiect is a PDP ... " and complete applicant information.
STEPS
CHECK THE APPROPRIATE BOX AND COMPLETE APPLICANT INFORMATION
IX] 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.
D 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: Kevin Dunn Applicant Title: Manager
Applicant Signature: Date:
.. • Environmentally Sensitive Areas include but are not limited to all Clean Water Act Section 303(d) 1mpa1red 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 Gities 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 Citv Use Onlv
YES NO
City Concurrence: □ □
By:
Date:
Project ID:
E-34 Page 4 of 4 REV 04/17
SITE INFORMATION CHECKLIST
Project Summary Information
Project Name Walnut Beach Homes
Project ID CT 2018-0001 / CDP 2018-0003 / PUD 2018-0001
Project Address 362 Walnut Avenue
Carlsbad, CA 92008
Assessor's Parcel Number(s) (APN(s)) 204-132-17-00
Project Watershed (Hydrologic Unit) Carlsbad 904.21 (Agua Hedionda HSA)
Parcel Area 0.574 Acres ( 25,020 Sauare Feet)
Existing Impervious Area
(subset of Parcel Area) 0.086 Acres ( 3,762 Square Feet)
Area to be disturbed by the project 0.574 Acres ( 25,020 Square Feet) (Proiect Area)
Project Proposed Impervious Area
(subset of Project Area) 0.247 Acres ( 10,770 Square Feet)
Project Proposed Pervious Area
(subset of Project Area) 0.327 Acres ( 14,250 Square Feet)
Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the
Project.
This may be less than the Parcel Area.
DescrtDtJon of Exlstina Site Condition and Dralnaae Patterns
Current Status of the Site (select all that apply):
✓ Existing development
□ Previously graded but not built out
□ Agricultural or other non-impervious use
D Vacant, undeveloped/natural
Description / Additional Information:
Existing Land Cover Includes (select all that apply):
✓ Vegetative Cover
✓ Non-Vegetated Pervious Areas
✓ Impervious Areas
Description/ Additional Information:
Underlying Soil belongs to Hydrologic Soil Group (select all that apply):
ONRCS Type A
✓ NRCS Type B
D NRCS Type C
D NRCS Type D
Approximate Depth to Groundwater (GW):
D GW Depth < 5 feet
o 5 feet < GW Depth < 10 feet
D 10 feet < GW Depth < 20 feet
✓ GW Depth > 20 feet
Existing Natural Hydrologic Features (select all that apply):
D Watercourses
□Seeps
□ Springs
□Wetlands
✓ None
Description / Additional Information:
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]:
(1) Existing drainage conveyance can be categorized as urban. However, there does not
appear to be any significant drainage infrastructure onsite to convey storm water, and water
travels through the site on the surface by way of sheet flow. Water eventually leaves the site to
the southwest towards Walnut Avenue, flowing on the surface and entering the public right-of-
way.
(2) There do not appear to be any existing onsite storm water conveyance systems. Water
eventually leaves the subject property at the southwest corner of the site toward Walnut
Avenue. Public storm drain infrastructure in Walnut Avenue then intercepts runoff and routes
east to the NCTD railroad right-of-way, discharging through a headwall and rip rap once through
Washington Street.
It should be noted that based on a study by Pasco, Laret, Suiter & Associates of the local
drainage basin draining to Walnut Avenue, the existing storm drain is at or very near capacity in
the current condition.
There appears to be a storm drain system located in the NCTD railroad right-of-way that
eventually intercepts runoff and routes it south towards the Agua Hedionda Lagoon.
(3) Offsite runoff is not conveyed through the project site. Existing residential developments
surrounding the property, in addition to Walnut Avenue to the south, preclude drainage from
entering the site by way of neighboring properties.
Description of ProDosed Site DeveloDment and Dralnaae Patterns
Project Description / Proposed Land Use and/or Activities:
The project proposes to demolish all existing onsite structures, clear and grub the site, and
construct 11 new multi-family condominium units along with a shared driveway and walkways.
List/describe proposed impervious features of the project (e.g., buildings, roadways, parking
lots, courtyards, athletic courts, other impervious features):
Proposed impervious features onsite include buildings and concrete walkways
List/describe proposed pervious features of the project (e.g., landscape areas):
Proposed pervious features onsite include landscaping, a treatment control BMP basin, and a
driveway consisting of large concrete pads with gravel-filled openings to promote infiltration
Does the project include grading and changes to site topography?
✓ Yes
□No
Description/ Additional Information:
Project proposes to precise the grade the site along with some changes to onsite topography.
The onsite grading consists of 675 CY of cut and 125 CY of fill, resulting in 550 CY of export.
The site has been designed to drain to a HMP-sized bioretention basin and a low point near the
northern portion of the lot.
Does the project include changes to site drainage (e.g., installation of new storm water
conveyance systems)?
✓ Yes
□No
Description/ Additional Information:
Onsite drainage is being modified to include a proposed private storm drain system and storm
water treatment basin. Different from the existing condition, water will not just sheet flow from
the property, but will be collected, treated, and detained prior to discharge from the property.
Runoff that is currently being conveyed from the site to a public storm drain system in Walnut
Avenue that is at capacity will be routed to the northeast corner of the site and discharge to
Washington Avenue.
Identify whether any of the following features, activities, and/or pollutant source areas will be
present (select all that apply):
✓On-site storm drain inlets
□ Interior floor drains and elevator shaft sump pumps
D Interior parking garages
✓Need for future indoor & structural pest control
✓ Landscape/Outdoor Pesticide Use
D Pools, spas, ponds, decorative fountains, and other water features
D Food service
D Refuse areas
D Industrial processes
D Outdoor storage of equipment or materials
□ Vehicle and Equipment Cleaning
D Vehicle/Equipment Repair and Maintenance
D Fuel Dispensing Areas
D Loading Docks
✓ Fire Sprinkler Test Water
D Miscellaneous Drain or Wash Water
D Plazas, sidewalks, and parking lots
Identification of Recelvlna 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):
Drainage leaving the site occurs from the northeast corner out to Washington Street. Once in
the Washington Street right-of-way, water is routed on the surface NE to storm drain
infrastructure in the NCTD railroad ROW. Once in the existing storm drain, it is routed back
south where it outlets to the Agua Hedionda Lagoon.
List any 303(d) impaired water bodies within the path of storm water from the project site to the
Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable), identify the
pollutant(s)/stressor(s) causing impairment, and identify any TMDLs for the impaired water
bodies:
303(d) Impaired Water Bodv Pollutant(s)/Stressor(s) TMDLs
Agua Hedionda Lagoon Enterococcus
Fecal Coliform
Manganese
Phosphorus
Selenium
Total Dissolved Solids
Identification of ProJect Sita Pollutants
Identify pollutants anticipated from the project site based on all proposed use(s) of the site (see
BMP Design Manual Aooendix B.6):
Also a Receiving
Not Applicable to Anticipated from the Water Pollutant of
Pollutant the Proiect Site Proiect Site Concern
Sediment X
Nutrients I X
Heavv Metals X
Oraanic Compounds X
Trash & Debris X
Oxygen Demanding
Substances X
Oil & Grease X
Bacteria & Viruses X
Pesticides X
Hvdromodlflcatlon Manaaement Reaulrements
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):
Critical Coarse Sediment Yield Areas*
*This Section only reaulred If hvdromodlflcatlon manaaement ranulrements annly
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.
o 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:
Flow Control for Post-Project Runotr
*This Section onlv reaulred If hvdromodlflcatlon manaaement reaulrements 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.
The point of compliance (POC-1) for this project is the location at which drainage leaves the
subject property. Refer to the HMP Exhibit included in Attachment 2 of this report and the
following page for a discussion of the project POC.
Has a geomorphic assessment been performed for the receiving channel(s)?
✓ No, the low flow threshold is 0.102 (default low flow threshold)
□ Yes, the result is the low flow threshold is 0.102
□ Yes, the result is the low flow threshold is 0.302
□ Yes, the result is the low flow threshold is 0.502
If a geomorphic assessment has been performed, provide title, date, and preparer:
N/A
Discussion/ Additional Information: (optional)
Other Site Raaulrements 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.
N/A
Ontional Additional Information or Continuation of Previous Sections As Needed
This space provided for additional information or continuation of information from previous
sections as needed.
Continued from "Flow Control for Post-Project Runoff':
This project proposes a micro-diversion of runoff within the Agua Hedionda Hydrologic Sub-
Area of the Carlsbad watershed. Flows leaving the subject property in the existing condition
currently appear to enter Walnut Avenue infrastructure from the southwest corner of the
property before discharging east to NCTD right-of-way. From there, runoff is conveyed south to
the Agua Hedionda Lagoon. In the proposed condition, storm water is collected and routed to
the northeast corner of the property for treatment and detention before outletting in the
Washington Street right-of-way. Once in Washington Street, existing curb and gutter route
flows north for a City block before also discharging east to NCTD right-of-way. These micro-
diverted flows are then conveyed south in the same storm drain system as in the existing
condition to outlet in the Agua Hedionda Lagoon.
For storm water modeling purposes using SWMM, the point of compliance for the project is
assumed to be the point that storm water discharges from the property in the existing and
proposed condition. However, to demonstrate compliance with the regional MS4 Permit, the
ultimate point of compliance occurs in NCTD right-of-way downstream to the southeast of the
subject property. Refer to Attachment 2 of this report for the project's HMP Exhibit and offsite
point of compliance.
The micro-diversion of flows occurs for only a short period before ultimately entering the same
storm drain system and reaching the outlet in the Agua Hedionda Lagoon. The micro-diversion
also helps alleviate an already sub-standard drainage condition by directing water away from
the storm drain system in Walnut Avenue that is currently at capacity. Additional options were
studied on where to ultimately discharge from the subject property, and the proposed solution
was deemed the most practical and feasible.
Continued from "Proposed Site Development and Drainage Patterns"
The panhandle portion of the existing parcel is self-mitigating in the proposed condition. The
project proposes to replace existing AC pavement with a concrete drive with gravel-filled
openings that will behave like a pervious material and provide LID treatment along with water
quality benefits.
C_cityof
Carlsbad
STANDARD PROJECT
REQUIREMENT
CHECKLIST
E-36
Project lnfonnatlon
Project Name: Walnut Beach Homes -362 Walnut Avenue
Project ID: CT 2018-0001 / CDP 2018-0003 / PUD 2018-0001
DWG No. or Building Permit No.:
Source Control BMPs
Development Services
Land Development Engineering
1635 Faraday Avenue
(760) 602-2750
www.carlsbadca.gov
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 (Volume 5 of City Engineering Standards) 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. Please add attachments if more space is needed.
• "NIA" 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 [i) Yes D No 0 N/A
Discussion/justification if SC-1 not implemented:
SC-2 Storm Drain Stenciling or Signage [i) Yes 0 No 0 N/A
Discussion/justification if SC-2 not implemented:
No public storm drain inlets proposed for stenciling and/or signage; provide signage for private storm
drain as needed and adjacent to BMP basin
SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On, Runoff, and Wind D Yes D No [i) N/A
Dispersal
Discussion/justification if SC-3 not implemented:
No permanent outdoor materials storage areas proposed by this project
E-36 Page 1 of 4 Revised 09/16
Source Control Reaulrement (continued) Annlled?
SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On, Runoff, and □Yes D No Iii NIA Wind Dispersal
Discussion/justification if SC-4 not implemented:
No permanent materials stored in outdoor work areas proposed by this project
SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal Iii Yes D No O NIA
Discussion/justification if SC-5 not implemented:
No permanent trash enclosure -private trash bin storage recesses proposed within each private
garage
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 Aooendix E.1 of BMP Manual for quidance).
Iii On-site storm drain inlets Iii Yes D No 0 NIA
□ Interior floor drains and elevator shaft sump pumps □ Yes D No Iii N/A
D Interior parking garages □ Yes D No Iii N/A
□ Need for future indoor & structural pest control □Yes D No Iii N/A
Iii Landscape/Outdoor Pesticide Use [ii Yes D No 0 N/A
□ Pools, spas, ponds, decorative fountains, and other water features D Yes D No Iii N/A
D Food service Iii Yes D No 0 N/A
Iii Refuse areas D Yes D No Iii N/A
□ Industrial processes □ Yes O No Iii N/A
□ Outdoor storage of equipment or materials □ Yes D No Iii N/A
□ Vehicle and Equipment Cleaning □Yes D No Iii NIA
□ Vehicle/Equipment Repair and Maintenance D Yes D No Iii N/A
D Fuel Dispensing Areas D Yes D No Iii N/A
D Loading Docks D Yes D No Iii N/A
Iii Fire Sprinkler Test Water [ii Yes D No 0 NIA
□ Miscellaneous Drain or Wash Water D Yes D No Iii N/A
□ Plazas, sidewalks, and oarkina lots D Yes D No lil N/A
For "Yes" answers, identify the additional BMP per Appendix E.1. Provide justification for "No" answers.
Only private area drains proposed for on-site storm drain inlets. No operational BMP's proposed.
Landscaping will be maintained using minimum or no pesticides
Trash receptacles provided in garage of each unit, so they will be covered. Dumping of liquid or
hazardous wastes will be prohibited
Fire sprinkler test water will be plumbed to sanitary sewer per CASQA fact sheet and latest building code
E-36 Page 2 of 4 Revised 09/16
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 (Volume 5 of City Engineering Standards) 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. Please add attachments if more space is needed.
• "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 I Applied?
SD-1 Maintain Natural DrainaQe Pathways and HydroloQic Features I D Yes I D No I ~ N/A
Discussion/justification if SD-1 not implemented:
No natural drainage pathways/ hydrologic features to maintain
SD-2 Conserve Natural Areas, Soils, and Vegetation T D Yes T ~ No I D N/A
Discussion/justification if SD-2 not implemented:
Entire project site is proposed to be graded to accommodate the proposed site plan
SD-3 Minimize Impervious Area T ~ Yes I D No I D N/A
Discussion/justification if SD-3 not implemented:
SD-4 Minimize Soil Compaction l ~ Yes I D No I D NIA
Discussion/justification if SD-4 not implemented:
Soil compaction outside of building envelopes will be minimized. Project drive aisle proposes modular
permeable pavers to promote infiltration. Minimal soil compaction under PCC pavers is proposed to
increase conductivity.
SD-5 Impervious Area Dispersion l ~ Yes I 0 No ID NIA
Discussion/justification if SD-5 not implemented:
Modular permeable pavers proposed for drive aisle.
E-36 Page 3 of 4 Revised 09/16
Site Dulan Ranulrement (continued) I Aoolled?
SD-6 Runoff Collection I lil Yes I 0 No ID N/A
Discussion/justification if SD-6 not implemented:
SD-7 Landscaping with Native or Drouqht Tolerant Species f lil Yes I O No I D N/A
Discussion/justification if SD-7 not implemented:
SD-8 Harvestinq and Usinq Precipitation I D Yes I lil No I D N/A
Discussion/justification if SD-8 not implemented:
No harvest and reuse proposed with this project -not feasible to implement
E-36 Page 4 of 4 Revised 09/16
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 individual
structural 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.
Based on the initial development of the project site plan, the location of the storm water pollutant
BMP was chosen towards the northern property line to accommodate the proposed drainage
design. Once the results of onsite infiltration testing were acquired in the area proposed for the
basin, it was determined that partial infiltration of the DCV was feasible for this project site.
The onsite drainage basin discharging to the project BMP was delineated, the DCV was then
calculated, and the BMP was sized to comply with hydromodification and storm water pollutant
control requirements of the MS4 Permit using the EPA Storm Water Management Model
(SWMM) software to conduct the analysis. Refer to Attachment 5 of this report for results from
the analysis.
A structural BMP is not proposed to treat the panhandle portion of the existing parcel, as this
area is considered self-retaining by means of site design BMPs in accordance with Section
5.2.3 of the BMP Design Manual. The project proposes to replace existing AC pavement with a
concrete drive with gravel-filled openings that will behave like a pervious material and provide
LID treatment along with water quality benefits.
[Continue on next page as necessary.]
Structural BMP Summary Information
[Copy this page as needed to provide Information for each lndlvldual proposed
structural BMPl
Structural BMP ID No. BMP-1
DWG 513-1A / GP 2018-0029 (CT 2018-0001\ Sheet No. 2-5
Type of structural BMP:
D 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):
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 Contents Checklist
Sequence
Attachment 1 a OMA Exhibit (Required)
Attachment 1 b
Attachment 1 c
Attachment 1 d
Attachment 1 e
See OMA Exhibit Checklist on the
back of this Attachment cover sheet.
(24"x36" Exhibit typically required)
Tabular Summary of DMAs Showing
OMA ID matching OMA Exhibit, OMA
Area, and OMA Type (Required)*
*Provide table in this Attachment OR
on OMA Exhibit in Attachment 1 a
Form 1-7, 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 1-7.
Form 1-8, 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 1-8.
Pollutant Control BMP Design
Worksheets I Calculations (Required)
Refer to Appendices B and E of the
BMP Design Manual for structural
pollutant control BMP design
guidelines
✓ Included
✓ Included on OMA Exhibit in
Attachment 1 a
□ Included as Attachment 1 b,
separate from OMA Exhibit
□ Included
✓ Not included because the entire
project will use infiltration BMPs
✓ Included
□ Not included because the entire
project will use harvest and use
BMPs
✓ Included
Use this checklist to ensure the required information has been included on the DMA
Exhibit:
The OMA Exhibit must identify:
l{I Underlying hydrologic soil group
Kl Approximate depth to groundwater
□ Existing natural hydrologic features (watercourses, seeps, springs, wetlands)
Kl Critical coarse sediment yield areas to be protected (if present)
Ki Existing topography and impervious areas
Kl Existing and proposed site drainage network and connections to drainage offsite
Ki Proposed grading
Kl Proposed impervious features
~ Proposed design features and surface treatments used to minimize imperviousness
Ki Drainage management area (OMA) boundaries, OMA ID numbers, and OMA areas (square
footage or acreage), and OMA type (i.e., drains to BMP, self-retaining, or self-mitigating)
Ki Structural BMPs (identify location and type of BMP)
Rincon Walnut Ave. Project 17-11664
Appendix I: Forms and Checklists
r~ ·~ ~ ·. fac~(oc sal:.;;:Ji·d1~f~=1A'miHIT'~'1~;tr·,. .. I I'.---:-·.
i f •• •
• ► •~ / ,~,.., .,.,_, ;-. •-."f•.~ " .,."T .-1r I \r.,. .. ~ .. "__.-..:::.__...--.... ~. r· : f.orrii 'f 9,
... , • ", -:--. c··.' • "i-'·. , · Worksheet • :j ~:•at'':...~~:.:-t.._~i---·__,_~-_: ~I I '-~~.JI".' __ ':.;~~' JJ .:...: ·":~ -.
f'actor Catcgon Factor Descnpnon Assigned Factor Product (p)
Weight (w) Value M p =w xv
Soil assessment methods 0.25 2 0.5
Predominant soil texture 0.25 2 0.5
Suitabilitr Site soil variability 0.25 2 0.5 A Assessment Depth to 1,>Toundwater I impervious
layer 0.25 1 0.25
Suitability Assessment Safety Factor, SA = :Ep 1.75
Level of pretreatment/ expected 0.5 2 I sediment loads
H Design Redundancy/ resiliency 0.25 2 .5
Compaction during construction 0.25 2 .5
Design Safety Pactor, Su = :Ep 2
Combined Safety Factor, S,oo~= S.1 x Sn 3.5
Observet! Jnfiltration Rate, inch/hr, K,.,,,·n·<J
4.0 (corrected for test-specific bias)
Desi~ Infiltration Rate, in/hr, Kic.,11" = K ,t...,n«I / S,o.,, 1.14
Supporting Data
Dricfly describe infiltration test and provide reference to test forms:
Simple open pit tesling was performed al 2 locations on the site per the requirements of the City of Carlsbad Storm Water
Standards, BMP Design Manual, 1n accordance with Appendix D.
Please refer lo our "Report of Preliminary Geotechnical Investigation" dated November 14, 2017 for details of the
comprehensive evaluation and mvestigallon conducted, simple open pit test rates and simple open pit rate to 1nfil1rat1on rate calculat,ons and maps representative of the study
1.7 February 2016
1
2
3
4
5
6
Appendix B: Storm Water Pollutant Control Hydrologic Calculations and Sizing Methods
Worksheet B.2-1. DCV
Design Capture Volume Worksheet B-2.1
85th percentile 24-hr storm depth from Figure B.1-1 d= 0.58 inches
Area tributary to BMP (s) A= 0.552 acres
Area weighted runoff factor (estimate using Appencfoc 0.27
B.1.1 and B.2.1) C= unitless
Tree wells volume reduction TCV= -cubic-feet
Rain barrels volume reduction RCV= -cubic-feet
Calculate DCV =
311
(3630 x C x d x A) -TCV -RCV DCV= cubic-feet
B-10 February 2016
Appendix B: Storm Water Pollutant Control Hydrologic Calculations and Sizing Methods
Worksheet B.5-1: Simple Sizing Method for Biofiltration BMPs
~■ma,ff,,n~
implementing retention BMPs 311 cubic-feet
Partial Retention
2 Infiltration rate from Form I-9 if partial infiltration is feasible -in/hr.
3 Allowable drawdown time for aggregate storage below the underdrain 36 hours
4 Depth of runoff that can be infiltrated [Line 2 x Line 3] 0 inches
5 Aggregate pore space 0.40 in/in
6 Required depth of gravel below the underdrain [Line 4/ Line 5] 0 inches
7 Assumed surface area of the biofiltration BMP 300 sq-ft
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 45 cubic-feet
10 DCV that requires biofiltration [Line 1 -Line 9] 266 cubic-feet
BMP Parameters
11 Surface Ponding [6 inch minimum, 12 inch maximum] 18 inches
12 Media Thickness [18 inches minimum], also add mulch layer thickness to 18 inches this line for sizing calculations
13 Aggregate Storage above underdrain invert (12 inches typical) -use 0 30 inches inches for sizing if the aggregate is not over the entire bottom surface area
14 Media available pore space 0.2 in/in
15 Media filtration rate to be used for sizing (5 in/hr. with no outlet control; 5 in/hr. if the filtration is controlled by the outlet, use the outlet controlled rate)
Baseline Calculations
16 Allowable Routing Time for sizing 6 hours
17 Depth filtered during storm [ Line 15 x Line 16] 30 inches
18 Depth of Detention Storage 33.6 inches [Line 11 + (Line 12 x Line 14) + (Line 13 x Line 5)]
19 Total D epth Treated [Line 17 + Line 18] 63.6 inches
Option 1 -Biofilter 1.5 times the DCV
20 Required biofiltered volume [1.5 x Line 10] 399 cubic-feet
21 Required Footprint [Line 20/ Line 19] x 12 75 sq-ft
Option 2 -Store 0.75 of remainin2" DCV in pores and pondin2
22 Required Storage (surface+ pores) Volume [0.75 x Line 10] 200 cubic-feet
23 Required Footprint [Line 22/ Line 18] x 12 71.3 sq-ft
Footprint of the BMP
24 Area draining to the BMP 24,020 sq-ft
25 Adjusted Runoff Factor for drainage area (Refer to Appendix B.1 and B.2) 0.27
26 Minimum BMP Footprint [Line 24 x Line 25 x 0.03] 193 sq-ft
27 Footprint of the BMP = Maximum(Minimum(Line 21, Line 23), Line 26) 300 sq-ft
Note: 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 Linc 21 or Linc 23)
B-26 February 2016
Appendix E: BMP Design Fact Sheets
Design Adaptations for Project Goals
Partial infiltration BMP with biofiltration treatment for storm water pollutant control.
Biofiltration with partial retention can be designed so that a portion of the DCV is infiltrated by
providing infiltration storage below the underdraio invert. The infiltration storage depth should be
determined by the volume that can be reliably infiltrated within drawdowo time limitations. Water
discharged through the underdrain is considered biofiltratioo treatment. Storage provided above the
underdrain within surface ponding, media, and aggregate storage is included in the biofiltration
treatment volume.
Integrated storm water flow control and pollutant control configuration. The system can be
designed to provide flow rate and duration control by primarily providing increased surface ponding
and/ or having a deeper aggregate storage layer. This will allow for significant detention storage, which
can be controlled via inclusion of an orifice in an outlet structure at the downstream end o f the
underdrain.
Design Criteria and Considerations
Biofiltration with partial retention must meet the following design criteria and co nsiderations.
Deviations from the below criteria may be approved at the discretion of the City Engineer if it is
determined to be appropriate:
Siting and Design
□
□
□
Placement observes geotechnical
recommendations regarding potential hazards
(e.g., slope stability, landslides, liquefaction
zones) and setbacks (e.g., slopes, foundations,
utilities).
Selection and design of basin is based on
infiltration feasibility criteria and appropriate
design infiltration rate (See Appendix C and
D).
Contributing tributary area shall be '.::'. 5 acres
('.::'. 1 acre preferred).
E-59
Intent/Rationale
Must not negatively impact existing site
geotechnical concerns.
Must operate as a partial infiltration
design and must be supported by
drainage area and in-situ infiltration rate
feasibility findings.
Bigger BMPs require additional design
features for proper performance.
Contributing tributary area greater than 5
acres may be allowed at the discretion of
the City Engineer if the following
conditions are met: 1) incorporate design
features (e.g. flow spreaders) to
minimizing short circuiting of flows in
the BMP and 2) incorporate additional
February 2016
Siting and Design
□ Finish grade of the facility is :S 2%.
Surface Ponding
□
□
□
□
Surface ponding is limited to a 24-hour
drawdown time.
Surface ponding depth is ~ 6 and :S 12 inches.
A minimum of 2 inches of freeboard is
provided.
Side slopes are stabilized with vegetation and
are = 3H:1V or shallower.
Vegetation
E-60
Appendix E: BMP Design Fact Sheets
Intent/Rationale
design features requested by the City
Engineer for proper performance of the
regional BMP.
Flatter surfaces reduce erosion and
channelization within the facility.
Surface ponding limited to 24 hours for
plant health.
Surface ponding drawdown time greater
than 24-hours but less than 96 hours
may be allowed at the discretion of the
City Engineer if certified by a landscape
architect or agronomist.
Surface ponding capacity lowers
subsurface storage requirements. D eep
surface ponding raises safety concerns.
Surface ponding depth greater than 12
inches (for additional pollutant control
or surface outlet structures or flow-
control orifices) may be allowed at the
discretion of the City Engineer if the
following conditions are met: 1) surface
ponding depth drawdown time is less
than 24 hours; and 2) safety issues and
fencing requirements are considered
(typically ponding greater than 18" will
require a fence and/ or flatter side slopes)
and 3) potential for elevated clogging risk
is considered.
Freeboard provides room for head over
overflow structures and minimizes risk
of uncontrolled surface discharge.
Gentler side slopes are safer, less prone
to erosion, able to establish vegetation
more quickly and easier to maintain.
February 2016
Siting and Design
□
□
Plantings are suitable for the climate and
expected ponding depth. A plant list to aid in
selection can be found in Appendix E.20
An irrigation system with a connection to
water supply should be provided as needed.
Mulch (Optional)
□
A minimum of 3 inches of well-aged, shredded
hardwood mulch that has been stockpiled or
stored for at least 12 months is provided.
Mulch must be non-floating to avoid clogging
of overflow structure.
Media Layer
□
□
Media maintains a minimum filtration rate of 5
in/hr over lifetime of facility. An initial
filtration rate of 8 to 12 in /hr is recommended
to allow for clogging over time; the initial
filtration rate should not exceed 12 inches per
hour.
Media is a minimum 18 inches deep, meeting
either of these two media specifications:
City of San Diego Storm Water Standards
Appendix F (February 2016, unless superseded
by more recent edition) or County of San
Diego Low Impact Development Handbook:
Appendix G -Bioretention Soil Specification
Qune 2014, unless superseded by more recent
edition).
Alternatively, for proprietary designs and
custom media mixes not meeting the media
specifications contained in the 2016 City of San
Diego Storm Water Standards or County LID
E-61
Appendix E: BMP Design Fact Sheets
Intent/Rationale
Plants suited to the climate and ponding
depth are more likely to survive.
Seasonal irrigation might be needed to
keep plants healthy.
Mulch will suppress weeds and maintain
moisture for plant growth. Aging mulch
kills pathogens and weed seeds and
allows the beneficial microbes to
multiply.
A filtration rate of at least 5 inches per
hour allows soil to drain between events,
and allows flows to relatively quickly
enter the aggregate storage layer, thereby
minimizing bypass. The initial rate
should be higher than long term target
rate to account for clogging over time.
However an excessively high initial rate
can have a negative impact on treatment
performance, therefore an upper limit is
needed.
A deep media layer provides additional
filtration and supports plants with deeper
roots.
Standard specifications shall be followed.
For non-standard or proprietary designs,
compliance with Appendix F.1 ensures
that adequate treatment performance will
be provided.
February 2016
Appendix E: BMP Design Fact Sheets
Siting and Design Intent/Rationale
□
□
Manual, the media meets the pollutant
treatment performance criteria in Section F.1 .
Media surface area is 3% of contributing area
times adjusted runoff factor or greater.
Where receiving waters are impaired or have a
TMDL for nutrients, the system is designed
with nutrient sensitive media design (see fact
sheet BF-2).
Filter Course Layer
□
□
□
A filter course is used to prevent migration of
fines through layers of the facility. Filter fabric
is not used.
Filter course is washed and free of fines.
Filter course calculations assessing suitability
for particle migration prevention have been
completed.
Aggregate Storage Layer
E-62
----------------
Greater surface area to tributary area
ratios: a) maximizes volume retention as
required by the MS4 Permit and
b) decrease loading rates per square foot
and therefore increase longevity.
Adjusted runoff factor is to account for
site design BMPs implemented upstream
of the BMP (such as rain barrels,
impervious area dispersion, etc.). Refer
to Appendix B.2 guidance.
Use Worksheet B.5-1 Line 26 to es timate
the minimum surface area required per
this criteria.
Potential for pollutant export is partly a
function of media composition; media
design must mininuze potential for
export of nutrients, particularly where
receiving waters are impaired for
nutrients.
Migration of m edia can cause clogging of
the aggregate storage layer void spaces or
subgrade. Filter fabric is more likely to
clog.
Washing aggregate will help eliminate
fines that could clog the facility
Gradation relationship between layers
can evaluate factors (e.g., bridging,
permeability, and uniformity) to
determine if particle sizing is appropriate
or if an intermediate layer is needed.
February 2016
Siting and Design
□
□
Class 2 Permeable per Caltrans specification
68-1.025 is recommended for the storage layer.
Washed, open-graded crushed rock may be
used, however a 4-6 inch washed pea gravel
filter course layer at the top of the crushed
rock is required.
Maximum aggregate storage layer depth below
the underdrain invert is determined based on
the infiltration storage volume that will
infiltrate within a 36-hour drawdown time.
/nDow, Underdrain, and OutDow Structures
□
□
□
□
□
□
□
Inflow, underdrains and outflow structures are
accessible for inspection and maintenance.
Inflow velocities are limited to 3 ft/ s or less or
use energy dissipation methods. (e.g., riprap,
level spreader) for concentrated inflows.
Curb cut inlets are at least 12 inches wide, have
a 4-6 inch reveal (drop) and an apron and
energy dissipation as needed.
Underdrain outlet elevation should be a
minimum of 3 inches above the bottom
elevation of the aggregate storage layer.
Minimum underdrain diameter is 6 inches.
Underdrains are made of slotted, PVC pipe
conforming to ASTM D 3034 or equivalent or
corrugated, HDPE pipe conforming to
AASHTO 252M or equivalent.
An underdrain cleanout with a minimum 6-
inch diameter and lockable cap is placed every
250 to 300 feet as required based on
underdrain length.
E-63
Appendix E: BMP Design Fact Sheets
Intent/Rationale
Washing aggregate will help eliminate
fines that could clog the aggregate
storage layer void spaces or subgrade.
A maximum drawdown time is needed
for vector control and to facilitate
providing storm water storage for the
next storm event.
Maintenance will prevent clogging and
ensure proper operation of the flow
control structures.
High inflow velocities can cause erosion,
scour and/ or channeling.
Inlets must not restrict flow and apron
prevents blockage from vegetation as it
grows in. E nergy dissipation prevents
erosion .
A minimal separation from subgrade or
the liner lessens the risk of fines entering
the underdrain and can improve
hydraulic performance by allowing
perforations to remain unblocked.
Smaller diameter underdrains are prone
to clogging.
Slotted underdrains provide greater
intake capacity, clog resistant drainage,
and reduced entrance velocity into the
pipe, thereby reducing the chances of
solids migration.
Properly spaced cleanouts will facilitate
underdrain maintenance.
February 2016
Siting and D esign
Appendix E: BMP Design Fact Sheets
Intent/Rationale
□
Overflow is safely conveyed to a downstream
storm drain system or discharge point. Size
overflow structure to pass 100-year peak flow
for on-line infiltration basins and water quality
peak flow for off-line basins.
Planning for overflow lessens the risk of
property damage due to flooding.
Nutrient Sensitive Media Design
To design biofiltration with partial retention with underdrain for storm water pollutant control only
(no flow control required), the following steps should be taken:
Conceptual Design and Sizing Approach for Storm Water Pollutant Control Only
To design biofiltration with partial retention and an underdrain for storm water pollutant control only
(no flow control required), the following steps should be taken:
1. Verify that siting and design criteria have been met, including placement reqw.rements,
contributing tributary area, maximum side and finish grade slopes, and the recommended
media surface area tributary ratio.
2. Calculate the DCV per Appendix B based on expected site design runoff for tributary areas.
3. Generalized sizing procedure is presented in Appendix B.5. The surface ponding should be
verified to have a maximum 24-hour drawdown time.
Conceptual Design and Sizing Approach when Storm Water Flow Control Is Applicable
Control of flow rates and/ or durations will typically require significant surface ponding and/ or
aggregate storage volumes, and therefore the following steps should be taken prior to determination
of storm water pollutant control design. Pre-development and allowable post-project flow rates and
durations should be determined as discussed in Chapter 6 of this manual.
1. Verify that siting and design criteria have been met, including placement requirements,
contributing tributary area, maximum side and finish grade slopes, and the recommended
media surface area tributary ratio.
2. Iteratively determine the facility footprint area, surface ponding and/ or aggregate storage layer
depth required to provide detention and/ or infiltration storage to reduce flow rates and
durations to allowable limits. Flow rates and durations can be controlled from detention
storage by altering outlet structure orifice size(s) and/ or water control levels. Multi-level
orifices can be used within an outlet structure to control the full range of flows.
3. If biofiltration with partial retention cannot fully provide the flow rate and duration control
required by this manual, an upstream or downstream structure with significant storage volume
such as an underground vault can be used to provide remaining controls.
4. After biofiltration with partial retention has been designed to meet flow control
E-64 February 2016
Appendix E: BMP Design Fact Sheets
requirements, calculations must be completed to verify if storm water pollutant control
requirements to treat the D CV have been met.
E-65 February 2016
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
Seauence
Attachment 2a
Contents
Hydromodification Management
Exhibit (Required)
Attachment 2b Management of Critical Coarse
Sediment Yield Areas (WMAA Exhibit
is required, additional analyses are
optional)
Attachment 2c
Attachment 2d
See Section 6.2 of the BMP Design
Manual.
Geomorphic Assessment of Receiving
Channels (Optional)
See Section 6.3.4 of the BMP Design
Manual.
Flow Control Facility Design and
Structural BMP Drawdown
Calculations (Required)
See Chapter 6 and Appendix G of the
BMP Desiqn Manual
Checklist
✓ Included
See Hydromodification Management
Exhibit Checklist on the back of this
Attachment cover sheet.
✓ 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
✓ Not performed
D Included
✓ Included
Use this checklist to ensure the required information has been included on the
Hydromodification Management Exhibit:
The Hydromodification Management Exhibit must identify:
~ Underlying hydrologic soil group
~ Approximate depth to groundwater
D Existing natural hydrologic features ( watercourses, seeps, springs, wetlands) NIA
® Critical coarse sediment yield areas to be protected (if present)
~ Existing topography
@ Existing and proposed site drainage network and connections to drainage offsite
00 Proposed grading
~ Proposed impervious features
~ Proposed design features and surface treatments used to minimize imperviousness
~ Point(s) of Compliance (POC) for Hydromodification Management
~ Existing and proposed drainage boundary and drainage area to each POC (when necessary,
create separate exhibits for pre-development and post-project conditions)
@ Structural BMPs for hydromodification management (identify location, type of BMP, and
size/detail)
Drawdown Calculation for BMP-A
Project Name
Project No
Surface Drawdown Time:
Surface Area
Surface Ponding (to invert of lowest
surface discharge opening in outlet
structure):
Amended Soil Depth:
Gravel Depth:
Effective Depth
Infiltration per Geotechnical Testing
362 Walnut Ave
2808
16.1
300
1.5
1.5
2.5
33.6
1.120
hr
sq ft
ft
ft
ft
in
in/hr
ATTACHMENT 3
Structural BMP Maintenance Information
Use this checklist to ensure the required information has been included in the Structural
BMP Maintenance Information Attachment:
Preliminary Design/Planning/CEQA level submittal:
Attachment 3 must identify:
o Typical maintenance indicators and actions for proposed structural BMP(s) based
on Section 7.7 of the BMP Design Manual
Final Design level submittal:
Attachment 3 must identify:
o Specific maintenance indicators and actions for proposed structural BMP(s). This
shall be based on Section 7.7 of the BMP Design Manual and enhanced to reflect
actual proposed components of the structural BMP(s)
□ How to access the structural BMP(s) to inspect and perform maintenance
o Features that are provided to facilitate inspection (e.g., observation ports,
cleanouts, silt posts, or other features that allow the inspector to view necessary
components of the structural BMP and compare to maintenance thresholds)
□ Manufacturer and part number for proprietary parts of structural BMP(s) when
applicable
o Maintenance thresholds for BMPs subject to siltation or heavy trash(e.g., silt level
posts or other markings shall be included in all BMP components that will trap and
store sediment, trash, and/or debris, so that the inspector may determine how full
the BMP is, and the maintenance personnel may determine where the bottom of
the BMP is . If required, posts or other markings shall be indicated and described
on structural BMP plans.)
o Recommended equipment to perform maintenance
□ When applicable, necessary special training or certification requirements for
inspection and maintenance personnel such as confined space entry or
hazardous waste management
APPENDIX 3a
BMP MAINTENANCE THRESHOLDS
BMP DESCRIPTION
I STORM WATER I.IANAGEI.IENT AND DISCHARGE CONTROL MAINTENANCE AGREE/JENT APPROVAL NO: BIOFIL TRA nON ( 300 SF) O&M RESPONSIBLE PARTY DESJGNEE: WALNUT BEACH HOMES HOA
POST-CONSTRUCTION PERMANENT BMP
OPERA T/ON & MAINTENANCE PROCEDURE DETAILS
MAINTENANCE IND/CA TORS MAINTENANCE ACTION
ACCUMULATION OF SEDIMENT, LITTER, OR DEBRIS REMOVE AND PROPERLY DISPOSE OF ACCUMULATED MATERIALS, WITHOUT DAMAGE TO THE VEGETATION
POOR VEGETATION ESTABLISHMENT RE-SffD, RE-PLANT, OR RE-ESTABLISH VEGETATION PER ORIGINAL PLANS
OVERGROWN VEGETATION MOW OR TRIM AS APPROPRIATE, BUT NOT LESS THAT THE DESIGN HEIGHT OF THE VEGETATION PER
ORIGINAL PLANS.
EROSION DUE TO CONCENTRATED /RR/GA TION FLOW REPAIR/RE-SffD/RE-PLANT ERODED AREAS AND ADJUST THE /RR/GA TION SYSTEM
REPAIR/RE-SffD/RE-PLANT ERODED AREAS AND MAKE APPROPRIATE CORRECTIVE MEASURES SUCH AS
EROSION DUE TO CONCENTRATED STORM WATER RUNOFF FLOW ADDING STONE AT FLOW ENTRY POINTS OR MINOR RE-GRADING TO RESTORE PROPER DRAINAGE
ACCORDING TO THE ORIGINAL PLAN.
STANDING WATER IN 8/0F/L TRA TION AREAS MAKE APPROPRIATE CORRECTIVE MEASURES SUCH AS ADJUSTING /RR/GA TION SYSTEM, REMOVING
OBSTRUCTION OF DEBRIS OR INVASIVE VEGETATION, OR CLEANING UNDERDRAINS
OBSTRUCTED INLET OR OUTLET STRUCTURE CLEAR OBSTRUCTIONS
DAMAGE TO INLET OR OUTLET STRUCTURE REPAIR OR REPLACE AS APPLICABLE
MAINTENANCE EQUIPMENT AND ACCESS
USE LANDSCAPE EQUIPMENT FOR MAINTENANCE; ACCESS BMP FROM PR/VA TE
ROAD AT NORTHEAST CORNER OF SITE
INSPECTION FACILITATION
INSTALL J' X J ' OUTLET RISER STRUCTURE TO PROVIDE OBSERVATION
ACCESS FOR INSPECTION OF MAINTENANCE THRESHOLDS; MARKING TO BE
PROVIDED ON BMP COMPONENTS TO DETERMINE HOW FULL BMP IS.
PASCO LARET SUITER
& ASSOCIATES
CML £HGINlllllNG + LAND PLANNING ♦ LANO &UltVEYINQ
SJS -mpw.y 101. Ito A., Solaaa-. CA '2875
p ISl,JSt.1212 ( & 151.lSUIIJ ( ~coa
ATTACHMENT JA
ATTACHMENT 4
City standard Single Sheet BMP (SSBMP) Exhibit
[Use the City's standard Single Sheet BMP Plan.]
ATTACHMENT 5
SWMM Model Output and Support Documentation
Attachment Sa -Basin Geometry
Attachment Sb -SWMM / Hydromodification Analysis Discussion
SWMM / Hydromodification Analysis / Discussion
5.1 Hydromodification Analysis
To satisfy the requirements of the MS4 Permit, a hydromodification management strategy has been
developed for the project based on the Final Hydromodification Management Plan dated March
2011 , (Final HMP). A continuous simulation model, the Environmental Protection Agency (EPA)
Storm Water Management Model (SWMM) version 5.1, was selected to size mitigation measures.
The SWMM model is capable of modeling hydromodification management facilities to mitigate
the effects of increased runoff from the post-development conditions and use changes that may
cause negative impacts (i.e. erosion) to downstream channels.
5.1.1 Hydromodification Criteria
Pursuant to the MS4 Permit, post-development runoff conditions (flow rates and durations) must
not exceed pre-development runoff conditions by more than 10% (for the range of flows that result
in increased potential for erosion, or degraded instream habitat downstream of the project. Based
on the Final HMP:
• For flow rates between the pre-project lower flow threshold (10%, 30%, or 50%) of the pre-
project 2-year runoff event (0.1 Q2, 0.3Q2, or 0.5Q2) to the pre-project l 0-year event (Q10), the
post-project discharge rates and durations may not deviate above the pre-project rates and
durations by more than I 0% over more than 10% of the length of the flow duration curve.
A channel screening analysis may be performed to determine a larger lower flow threshold,
however for this project a lower flow threshold of 0.1 Q2 (high susceptibility) is assumed.
5.1.2 SWMM Model Development
SWMM is a rainfall-runoff model used for single event or continuous simulation of runoff quantity
from primarily urban areas. SWMM calculates and routes runoff based on user-specified input
including precipitation data, subcatchment characteristics, soil data, routing information, and BMP
configuration. SWMM is capable of modeling various hydrologic processes including but not
limited to time-varying precipitation, evaporation, storage, infiltration, and retention LID facilities.
5.1.3 SWMM Input
A pre-development and post-development model were created using the following global
information:
Parameter lnout Source
Precioitation Oceanside Rainfall Data Proiect Clean Water
Evaporation Encinitas ETo Zone Data CIMIS ETo Zones Map
Soils B USDA Web Soil Survev Annlication
The HMP biofiltration basin has been designed to comply with both pollutant control and
hydro modification management criteria. Refer to Section 3 .5 for the pollutant control calculations.
The HMP biofiltration portion in the SWMM model is specified as an "LID Control" within the
"Subcatchment" to define the ponding depth, biofiltration soil layer and gravel layer.
5.1.4 SWMM Processing and Output
The HMP sizing was determined assuming a completely pervious existing site condition. The pre-
development project 0.1 Q2 and Q,o were determined to be 0.016 cfs and 0.35 cfs, respectively.
After routing through the HMP biofiltration basin, the post-development, mitigated project 0.1 Q2
and Q,o were determined to be 0.006 cfs and 0.32 cfs leaving the site, respectively. Refer to the
SWMM output included in Attachment 5 of the project SWQMP for detailed information and data
from the SWMM model including input files, rain gage and evaporation data, and flow duration
and frequency curves. Drawdown calculations are also included in Attachment 2 of the SWQMP.
5.2 Storm Water Pollutant Control
To meet the requirements of the MS4 Permit, the HMP biofiltration facility is designed to treat
onsite storm water pollutants contained in the volume of runoff from a 24-hour, 85th percentile
storm event by filtering runoff through an engineered soil layer and gravel layer.
5.2.1 Numeric Sizing Requirements for Pollutant Control BMPs
Pursuant to the MS4 Permit, Pollutant Control BMPs shall be designed to retain onsite pollutants
contained in the post-development Design Capture Volume (DCV). The DCV is the volume of
runoff resulting from the 24-hour, 85th percentile storm event. The DCV calculations for the project
are located in Attachment 1 of the project SWQMP. The Pollutant Control BMP proposed for the
project is an HMP biofiltration basin. The proposed HMP biofiltration basin does provide some
retention, therefore pursuant to the MS4 Permit, the HMP biofiltration basin is designed to biofilter
1.0 times the DCV.
Attachment Sc -Additional SWMM Support Documentation
2808 362 Walnut Ave
1/8/2018
SWMM MODEL SCHEMATICS
PRE-PROJECT MODEL
Oceanside
[21
OMA-A
"'
POC-1 •
POST-PROJECT MODEL
Oceanside
[2]
OMA-A
"' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
'
BMP-A ..
STOR1 BYPASS
LOWFLOW
OUTLETSTRUCTURE
POC-1
', ,_DIV1
J:\Active Jobs\2808 Walnut Rincon\CIVIL\REPORTS\SWMM\Output\2808_SWMM_Schematics.xlsx
2808 362 Walnut Ave
1/8/2017
PRE-PROJECT
OMA Basin
A 1
Area (ac)
0.551
Total: 0.551
POST-PROJECT
OMA BMP Area (ac)
A 1 0.54
BMP-1 1 0.00689
Total: 0.551
Infiltration:
Width
(Area/Flow
Length) (ft)
141.3
Width
(Area/Flow
Length) (ft)
182.5
15.0
B:I 0.2lin/hr
% Slope
0.7%
% Impervious
47.6%
0%
SWMM INPUT
Weighted Weighted Weighted
Infiltration Suction Head Initial
% Impervious % "B" Soils % "C" Soils % "D" Soils (in/hr): (in): Deficit:
0% 100% 0% 0% 0.200 3.000 0.310
Weighted Weighted Weighted
Infiltration Suction Head Initial
% Slope % "B" Soils % "C" Soils % "D" Soils (in/hr): (in): Deficit:
1.0% 100% 0.0% 0% 0.200 3.000 0.310
0.0% 100% 0.0% 0% 0.200 3.000 0.310
Suction Head : Initial Deficit
B:I 3lin B:I 0.31
[TITLE)
;;Project Title/Notes
2808 362 Walnut Ave
Pre-Project Condition
[OPTIONS)
; ; Option
FLOW UNITS
INFILTRATION
FLOW ROUTING
LINK OFFSETS
MIN SLOPE
ALLOW PONDING
SKIP STEADY STATE --
START DATE
START TIME
REPORT START DATE
REPORT START TIME
END DATE
END TIME
SWEEP START
SWEEP END
DRY DAYS
REPORT STEP
WET STEP
DRY STEP
ROUTING STEP
INERTIAL DAMPING
NORMAL FLOW LIMITED
FORCE_MAIN_EQUATION
VARIABLE STEP
LENGTHENING STEP
MIN SURFAREJI.
MAX TRIALS
HEAD TOLERANCE
SYS FLOW TOL - -LAT FLOW TOL --MINIMUM STEP
THREADS
[EVAPORATION]
Value
CFS
GREEN AMPT
KINWAVE
DEPTH
0
NO
NO
08/28/1951
05:00 :00
08/28/1951
05:00 :00
05/23/2008
23 :00 :00
01/01
12/31
0
01 :00 :00
00 :15 :00
04 :00 :00
0 :01:00
PARTIAL
BOTH
H-W
0 .75
0
12.557
8
0 .005
5
5
0 .5
1
;;Data Source Parameters
. ·------------------------------,,
POC-1
POC-1
0 FREE NO POC-1
[DIVIDERS)
; ; Name Elevation Diverted Link Type
CUTOFF
Parameters
··--------------'' DIVl
[STORAGE)
; ;Name
IMD
0
Elev .
. ·----------------------''
STORl 0
[CONDUITS)
; ;Name From Node
BYPASS
Max Depth
0 .5
0 .015 0 0
InitDepth Shape Curve Name/Params
0 TABULAR STORl
To Node Length Roughness InOffset
0 0
N/A Fevap Psi Ksat
0 0
OutOffset InitFlow MaxFlow
;;-------------------------------------------------------- --------------------------------------------------
BYPASS DIVl STORl 400 0 .01 0 0 0 0
LOWFLOW DIVl POC-1 400 0 .01 0 0 0 0
[OUTLETS]
; ;Name From Node To Node Offset Type QTable/Qcoeff Qexpon Gated
;;---------------------------------------------------------------------------------------------------------
OUTLET STRUCTURE
[XSECTIONS)
; ; Link
. ·--------------' ' BYPASS
LOWFLOW
[CURVES)
; ;Name
. ·--------------'' RISER
RISER
RISER
RISER
RISER
RISER
RISER
RISER
RISER
RISER
RISER
STORl
Shape
DUMMY
DUMMY
Type
Rating
POC-1
Geoml
0
0
X-Value Y-Value
0 TABULAR/DEPTH RISER
Geom2 Geom3 Geom4 Barrels Culvert
--------------------------------------------------
0 0 0 1
0 0 0 1
--------------------
0 0
.05 .074
.1 .211
.15 .387
.2 .596
.25 1. 28
.3 2 .359
.35 3 .701
. 4 5 .26
.45 6 .985
.5 7 .155
NO
SWMM OUTPUT REPORT PRE-PROJECT CONDITION
EPA STORM WATER MANAGEMENT MODEL -VERSION 5 .1 (Build 5 .1 .010)
2808 362 Walnut Ave
Pre-Project Condition
*********************************************************
NOTE : The summary statistics displayed in this report are
based on results found at every computational time step,
not just on r esults from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models :
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... NO
Water Quality .......... NO
Infiltration Method ...... GREEN AMPT
Starting Date ............ AUG-28-1951 05:00 :00
Endi ng Date .............. MAY-23-2008 23 :00 :00
Antecedent Dry Days ...... 0 .0
Report Time Step ......... 01:00 :00
Wet Time Step ............ 00:15:00
Dry Time Step ............ 04:00 :00
**************************
Runoff Quantity Continuity
**************************
Total Precipitation ..... .
Evaporation Loss ........ .
I nfiltration Loss ....... .
Surface Runoff .......... .
Final Storage ........... .
Continuity Error (%)
**************************
Flow Routing Continuity
**************************
Dry Weather Inflow ...... .
Wet Weather Inflow ...... .
Volume
acre-feet
30 .998
0 .097
30 .042
0 .938
0 .000
-0 .259
Volume
acre-feet
0 .000
0 .938
Depth
inches
675 .090
2.121
654 .281
20 .436
0 .000
Volume
10"6 gal
0 .000
0 .306
J:\Active Jobs\2808 Walnut Rincon\CIVIL\REPORTS\SWMM\Output\2808_PreProject_SWMM_results.docx
SWMM OUTPUT REPORT
OUTLET STRUCTURE DUMMY
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
POST-PROJECT CONDITION
0 .58 18857 11:51
Analysis begun on: Mon Jan 08 09 :57 :13 2018
Analysis ended on: Mon Jan 08 09 :57 :44 2018
Total elapsed time: 00:00:31
J:\Active Jobs\2808 Walnut Rincon\CIVIL\REPORTS\SWMM\Output\2808_PostProject_SWMM_results.docx
POC-1
Peak Flow Frequency Summary
Return Period Pre-project Qpeak Post-project -Mitigated Q
(cfs) (cfs)
LF = 0.lxQ2 0.016 0.006
2-year 0.164 0.055
5-year 0.265 0.173
10-year 0.3 50 0.323
J:\Active Jobs\2808 Walnut Rincon\CIVIL\REPORTS\SWMM\2808_SWMM_PostProcessing_Alt6.xlsx
Low-flow Threshold:11 10% i POC-1
O.lxQ2 (Pre): 0.016 els
QlO (Pre): 0.350 els
Ordinate#: 100
Incremental Q (Pre): 0.00334 cfs
Total Hourly Oata:I 497370 lhours The proposed BMP:! PASSED
Interval Pre-project Flow Pre-project Hours Pre-project% Post-project Post-project % Percentage Pass/Fail (ds) Time Exceeding Hours Time Exceeding
0 0.016 129 2.59E-04 96 1.93E-04 74% Pass
1 0.020 126 2.53E-04 82 l.65E-04 65% Pass
2 0.023 120 2.41E-04 75 1.SlE-04 63% Pass
3 0.026 118 2.37E-04 72 1.45E-04 61% Pass
4 0.030 115 2.31E-04 67 1.35E-04 58% Pass
5 0.033 114 2.29E-04 63 1.27E-04 55% Pass
6 0.036 108 2.17E-04 61 1.23E-04 56% Pass
7 0.040 106 2.13E-04 59 1.19E-04 56% Pass
8 0.043 106 2.13E-04 56 1.13E-04 53% Pass
9 0.046 97 1.95E-04 47 9.4SE-0S 48% Pass
10 0.050 94 1.89E-04 44 8.85E·05 47% Pass
11 0.053 94 1.89E·04 44 8.8SE-0S 47% Pass
12 0.056 90 1.81E-04 41 8.24E-0S 46% Pass
13 0.060 84 1.69E-04 40 8.04E-05 48% Pass
14 0.063 82 1.65E-04 39 7.84E-05 48% Pass
15 0.066 80 1.61E-04 34 6.84E-0S 43% Pass
16 0.070 67 1.35E-04 34 6.84E-05 51% Pass
17 0.073 66 l.33E-04 34 6.84E-05 52% Pass
18 0.077 64 l.29E·04 32 6,43E-05 50% Pass
19 0.080 64 l.29E-04 32 6.43E-05 50% Pass
20 0.083 64 l.29E·04 31 6.23E-0S 48% Pass
21 0.087 63 1.27E·04 29 S.83E-05 46% Pass
22 0.090 60 l.21E-04 26 S.23E-05 43% Pass
23 0.093 57 1.15E-04 26 S.23E-05 46% Pass
24 0.097 55 1.llE-04 26 S.23E-05 47% Pass
25 0.100 53 l.07E-04 25 5.03E-05 47% Pass
26 0.103 53 l.07E-04 25 5.03E-05 47% Pass
27 0.107 53 1.07E-04 25 S.03E-0S 47% Pass
28 0.110 so l.0lE-04 25 S.03E-05 50% Pass
29 0.113 49 9.8SE-05 25 5.03E-0S 51% Pass
30 0.117 49 9.8SE·0S 25 S.03E-05 51% Pass
31 0.120 48 9.65E-05 25 5.03E·05 52% Pass
32 0.123 48 9.65E-05 25 5.03E-05 52% Pass
33 0.127 47 9.45E·05 25 5.03E-05 53% Pass
34 0.130 46 9.25E-05 24 4.83E-05 52% Pass
35 0.133 46 9.25E-0S 24 4.83E-05 52% Pass
36 0.137 44 8.85E-05 21 4.22E-05 48% Pass
37 0.140 41 8.24E-05 21 4.22E-05 51% Pass
38 0.143 40 8.04E-05 20 4.02E-05 50% Pass
39 0.147 38 7.64E-05 19 3.82E-05 50% Pass
40 0.150 38 7.64E-05 19 3.82E-05 50% Pass
41 0.153 37 7.44E-05 18 3.62E-05 49% Pass
42 0.157 35 7.04E-05 16 3.22E-05 46% Pass
43 0.160 34 6.84E-05 16 3.22E-05 47% Pass
44 0.163 33 6.63E-05 16 3.22E-OS 48% Pass
45 0.167 32 6.43E-05 15 3.02E-05 47% Pass
46 0.170 32 6.43E·05 15 3.02E-05 47% Pass
47 0.173 32 6.43E-05 15 3.02E-05 47% Pass
48 0.177 32 6.43E-05 15 3.02E-05 47% Pass
49 0.180 31 6.23E-05 15 3.02E-05 48% Pass
so 0.183 31 6.23E-OS 14 2.SlE-05 45% Pass
51 0.187 29 5.83E-05 14 2.SlE-05 48% Pass
52 0.190 28 S.63E-0S 13 2.61E-0S 46% Pass
53 0.193 27 5.43E·05 13 2.61E-05 48% Pass
54 0.197 27 5.43E-05 13 2.61E-05 48% Pass
55 0.200 26 5.23E-05 12 2.41E-05 46% Pass
56 0.203 23 4.62E-05 12 2.41E-05 52% Pass
57 0.207 21 4.22E-0S 12 2.41E-05 57% Pass
58 0.210 21 4.22E-05 11 2.21E-05 52% Pass
59 0.213 21 4.22E-05 11 2.21E-05 52% Pass
60 0.217 20 4.02E-05 11 2.21E-05 55% Pass
61 0.220 19 3.82E-05 11 2.21E-05 58% Pass
62 0.223 19 3.82E-05 11 2.21E-05 58% Pass
63 0.227 19 3.82E-05 10 2.0lE-05 53% Pass
64 0.230 19 3.82E-05 10 2.0lE-05 53% Pass
65 0.233 19 3.82E-05 10 2.0lE-05 53% Pass
66 0.237 18 3.62E-05 10 2.0lE-05 56% Pass
67 0.240 18 3.62E·05 10 2.0lE-05 56% Pass
68 0.243 17 3.42E-05 10 2.0lE-05 59% Pass
69 0.247 17 3.42E-05 10 2.0lE-05 59% Pass
70 0.250 17 3.42E-05 10 2.0lE-05 59% Pass
71 0.254 16 3.22E-0S 10 2.0lE-05 63% Pass
72 0.257 16 3.22E-05 10 2.0lE-05 63% Pass
Interval Pre-project Flow Pre-project Hours Pre-project% Post-project Post-project% Percentage Pass/Fail (chi Time Exceeding Hours Time hceedlng
73 0.260 16 3.22E-05 9 1.81E-05 56% Pass
74 0.264 15 3.02E-05 9 l.81E·05 60% Pass
75 0.267 13 2.61E-05 9 l.81E-05 69% Pass
76 0.270 12 2.41E-05 9 l.81E-05 75% Pass
77 0.274 12 2.41E-05 9 l.81E·05 75% Pass
78 0.277 9 l.81E-05 9 l.81E-05 100% Pass
79 0.280 9 l.81E-05 9 l.81E·05 100% Pass
80 0.284 9 l.81E·05 8 l.61E-05 89% Pass
81 0.287 8 1.61E-05 8 l.61E-05 100% Pass
82 0.290 8 l.61E·05 8 l.61E-05 100% Pass
83 0.294 8 l.61E·05 8 l.61E-05 100% Pass
84 0.297 8 l.61E-05 8 l.61E·05 100% Pass
85 0.300 7 l.41E·05 7 l.41E-05 100% Pass
86 0.304 7 l.41E-05 6 l.21E·05 86% Pass
87 0.307 6 l.21E·05 6 l.21E-05 100% Pass
88 0.310 6 l.21E·05 6 l.21E-05 100% Pass
89 0.314 6 1.21E-05 6 l.21E·05 100% Pass
90 0.317 6 l.21E·05 6 l.21E-05 100% Pass
91 0.320 6 l.21E-05 6 l.21E·0S 100% Pass
92 0.324 6 l.21E·0S 6 l.21E·0S 100% Pass
93 0.327 6 l.21E·05 6 1.21E-05 100% Pass
94 0.330 6 1.21E·0S 6 l.21E·0S 100% Pass
95 0.334 6 l.21E-05 s l.0lE-05 83% Pass
96 0.337 s l.0lE-05 5 l.0lE·0S 100% Pass
97 0.340 s l .0lE-05 s l.0lE-05 100% Pass
98 0.344 5 l.0lE-05 5 l.0lE-05 100% Pass
99 0.347 5 l.0lE-05 5 l.0lE-05 100% Pass
100 0.350 5 l.0lE-05 s l.0lE-05 100% Pass
POC-1
SWMM Model Flow Coefficient Calculation and
Effective Ponding Depth Calculation
BMP-A
PARAMETER ABBREV.
Ponding Depth PD
Bioretention Soil Layer s
Gravel Layer G
TOTAL
Orifice Coefficient Cg
Low Flow Orifice Diameter D
Drain exponent n
Flow Rate (volumetric) Q
Ponding Depth Surface Area Apo
Bioretention Surface Area As,AG
As,AG
Porosity of Bioretention Soil n
Flow Rate (per unit area) q
Effective Ponding Depth PDett
Flow Coefficient C
Bio-Retent ion Cell
LID BMP
18 in
18 in
30 in
5.5 ft
66 in
0.6 --
0.5 in
0.5 --
0.015 cfs
568 ft2
300 ft2
0.0069 ac
1.00 -
2.213 in/hr
25.64 in
0.2729 --
Pond Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 30® 2016 by Autodesk, Inc. v10.5
Pond No. 7 -STOR BMP-A Alt 6
Pond Data
Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 101 .50 ft
Stage/ Storage Table
Stage (ft) Elevation (ft) Contour area (sqft) Iner. Storage (cuft) Total storage (cuft)
0.00 101.50 568 0 0
0.50 102.00 671 309 309
Culvert I Orifice Structures Weir Structures
[AJ [BJ [CJ [PrfRsrJ [AJ [BJ
Rise (in) 12.00 0.00 0.00 0.00 Crest Len (ft) = 12.00 2.00
Span (in) 12.00 0.00 0.00 0.00 Crest El. (ft) 101. 70 101.50
No. Barrels 1 0 0 0 Weir Coeff. = 3.33 3.33
Invert El. (ft) = 96.00 0.00 0.00 0.00 Weir Type = 1 Reel
Length (ft) = 117.00 0.00 0.00 0.00 Multi-Stage = Yes Yes
Slope (%) = 1.50 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff. = 0.60 0.60 0.60 0.60 Exfil.(inlhr) = 0.000 (by Contour)
Multi-Stage = n/a No No No TW Elev. (ft) = 0.00
Monday, 01 / 8 / 2018
[CJ [DJ
Inactive 0.00
101 .50 0.00
0.68 3.33
30 degV
Yes No
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (cc) control. Weir risers checi<ed for or~ice cond,tions (1c) and submergence (s).
Stage I Storage I Discharge Table
Stage Storage Elevation ClvA ClvB ClvC PrfRsr Wr A WrB WrC WrD Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
0.00 0 101.50 0.00 0.00 0.00 0.000
0.05 31 101.55 6.96 oc 0.00 0.07 0.074
0.10 62 101.60 6.96 oc 0.00 0.21 0.211
0.15 93 101.65 6.96 QC 0.00 0.39 0.387
0.20 124 101.70 6.96 oc 0.00 0.60 0.596
0.25 155 101.75 6.96 oc 0.45 0.83 1.280
0.30 186 101.80 6.96 oc 1.26 1.09 2.359
0.35 217 101.85 6.96 oc 2.32 1.38 3.701
0.40 247 101.90 6.96 oc 3.57 1.69 5.260
0.45 278 101.95 6.99 oc 5.00 1.99 s 6.985
0.50 309 102.00 7.16 oc 5.50 s 1.66 s 7.155
Drawdown Calculation for BMP-A
Project Name
P . tN roJec 0
Surface Drawdown Time:
Surface Area
Surface Ponding (to invert of lowest
surface discharge opening in outlet
structure):
Amended Soil Depth:
Gravel Depth:
Effective Depth
Infiltration per Geotechnical Testing
362 Walnut Ave
2808
16.1
300
1.5
1.5
2.5
33.6
1.120
hr
sq ft
ft
ft
ft
in
in/hr
Hydrologic Soil Group-San Diego County Area, California
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
D A
D AID
DB
D BID
oc
0 C/D
DD
D Not rated or not available
Soil Rating Lines
-.,,, A -AID -B -BID
C -CID -D
,. -Not rated or not available
Soil Rating Points
■ A
■ AID
■ B
■ BID
USDA Natural Resources
-Conservation Service
C
•
C
CID
■ D
□ Not rated or not available
Water Features
Streams and Canals
Transportation
t++ Rails
-Interstate Highways
-US Routes
Major Roads
Local Roads
Background
• Aerial Photography
Web Soil Survey
National Cooperative Soil Survey
The soil surveys that comprise your AOI were mapped at
1 :24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed l scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 12, Sep 13, 2017
Soil map units are labeled (as space allows) for map scales
1 :50,000 or larger.
Date(s) aerial images were photographed: Nov 3, 2014-Nov
22, 2014
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
12/11/2017
Page 2 of 4
Hydrologic Soil Group-San Diego County Area, California
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
MIC Marina loamy coarse B
sand, 2 to 9 percent
slopes
2.4
Totals for Area of Interest 2.4
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (ND, BID, and C/D). The groups are defined as follows:
Group A Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (ND, BID, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
USDA Natural Resources
:iiiiii Conservation Service
Web Soil Survey
National Cooperative Soil Survey
100.0%
100.0%
12/11/2017
Page 3 of 4