HomeMy WebLinkAboutCT 14-06; AFTON WAY; PRIORITY DEVELOPMENT PROJECT (PDP) STORM WATER QUALITY MANAGEMENT PLAN (SWQMP) FOR AFTON WAY TM; PUD 14-09, HDP 14-05, DWG 495-9, DWG 495-9A, GR2016-0050, ROW 2016-0061, SWMP 16-26; 2017-01-09J
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CITY OF CARLSBAD
PRIORITY DEVELOPMENT PROJECT (PDP)
STORM WATER QUALITY MANAGEMENT PLAN (SWQMP)
FOR
AFTON WAY TM
CT 14-06
DWG 495-9 & 495-9A
SWQMP NO. 16-26
ENGINEER OF WORK:
)-9-11
RONALD HOLLOWAY DATE
PREPARED FOR:
PRESIDIO PEBBLE CREEK CARLSBAD & LLC
301 WEST 28TH STREET, SUITE A
NATIONAL CITY, CA 91950
619-938-0312
PREPARED BY:
bl.A ln,---H ' ,,',_.,
civil
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008-4387
(760) 931-8700
DATE: RE
JANUARY 9, 2017
W.O. 983-1326-600
JAN 1--0 2017
LAND D VELOPMENT
ENGINEERING
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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 1d: Categorization of Infiltration Feasibility Condition (when applicable)
Attachment 1 e: Pollutant Control BMP Design Worksheets I 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: ''Technical Memorandum: SWMM Modeling for Hydromodification Compliance of
Afton Way, City of Carlsbad, Revised June 17, 2015", prepared by Tory R.
Walker Engineering.
''Technical Memorandum: Determination of Pre-and Post-Developed 100-year
Peak Flow, Afton Way, City of Carlsbad, June 17, 2015", prepared by Tory R.
Walker Engineering.
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Project Name: 2200 Afton Way
Project ID: CT 14-06
CERTIFICATION PAGE
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 de ign.
R.C.E. 29271 Ex . 03/31/2017
Eng in ature, PE Number & Expiration Dabt,,,,,.
Ronald Hollowa
Print Name
bliA, Inc
November 8, 2016
Date
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PROJECT VICINITY MAP
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City of
Carlsbad
STORM WATER STANDARDS
QUESTIONNAIRE
Development Services
Land Development Engineering
1635 Faraday Avenue
(760) 602·2750
www.carlsbadca.gov
E-34
To address pcist·development poHutants that may be generated from development projects, the city requires that new
development and signrficant redevelopment priority projects incorporate Permanent Storm Water Best Management
Practices (BMPs) into the proje.ct design per Carlsbad BMP Deslgh Mimual {BMP Manual). To view the BMP Manual,
refer to the Engineering Standards (Volume 5).
This questicmnaire must b~ completed by the applicaht in advanc.e of submitting for a development appncation
(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' (POP} requlrements.
Yourresponses 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. l.f 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 proje~t application. Only one
completed and signed questionnaire is required when rnultipl.e development applications for the same project are
submitted concurrently.
: i.·.·· > ······· ·········.·• ){}{!.,/ .....•.. ·"•' ...... ·-···· \iti.:•·••.::• ...... -. ,..,.,
PROJECT NAME: Afton Way PROJECT !D:CT 14-06, HDP 14-05, HMP .15-03
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ADDRESS: 2200 AftonWay, Carlsbad, CA 92008 APN:167-53145, 167~250-06
The project is (check one): lKl New Development D Redevelopment
The total proposed disturbed area is: 146,606 ft2 ( 3.37 ) acres
The total proposed newly created and/or replaced impervious area is: 54,744 ft2 ( 1.26 ) acres
If your project is covered by an approved SWQMP as part of a larger developmentproject, provide the projectlD 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.
E-34 Page 1 of 4 REV 02116
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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 repairfimprovements to an existing building D OO
or structure that do not alter the size (See Section 1.3 of the BMP Design Manual for guidahce)?
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):
To determine if your project is exempt from PDP requirements pursuant to MS4 Permit Provision E.3.b.(3), please answer
the followlng questions:
Is your project LIMITED to one or more of the following:
1.
2.
3.
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;
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 uidance?
Retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constr1,Jcted in
accordance with the USEPA Green Stre1;its guidance?
Ground Mounted Solar Array that meets the criteria provided in section 1.42 of the BMP manual?
YES NO
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If you answered uyes" to one or more of the.above questions, provide discussion~ustifrcation 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 guidahce):
Page 2 pf4 REV02/t6
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To determine if your project ls a PDP, please l:inswerthe following questions (MS4 Permit Provision E.3.b.(1)):
YES NO
1. ls 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 ublic develo ment ro·ects on ublic or rivate 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
deve/o ment ro ·ects on ublic or riVate Janel,
3. IS your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more
of impervious surface collectively overthe 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
refreshmenf·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
develo ment ro'ect includes devefo ment on an natural slo ethat is twen -five erceht or reater.
5. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more
ofimpervious 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 surface collectively over the entire project site and supports a street, road, highway
freeway or driveway? A street, road, highway, freeway or driveway is any paved impervious surface
used for the trans Ottation of automobiles, trucks, motarc cles, and other vehicles.
7. Is your project a new or redevelopment project that creates ahd/or replaces 2,SOO square feet or inore
of impervious surtace co!lectiliely over the eritire site, and discharges directly to an Environmentally
Sensitive Area {ESA)? "Discharging Directly .to" includes now that is conveyed overland a distance of
200 feet or fess 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 act:acentlahds). *
8. Is your project a new development or redevelopment projectthat 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 CJass1Tication (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 5,000square
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 Dr,1ily
Traffic AD T) of 100 or more vehicles $r da .
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1 o. Is your project a new or redevelopment project that results in the disturbance ofone or more acres of land 'X1
and are expected to generate pollutants post construction? lfr.l
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%? (CMG
21.203.040
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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, che(!k the first box stating "My project is a PDP ... "
and complete applicant information.
If you answered "no" to atl of the above questions, your project is a 'STANDARD PROJECT.' Go to step 5, check the
second box statin "M ro· ecfis a 'STANDARD PROJECT' ... " and com lete a licant information.
Page 3 of 4 REV 02/16
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Complete the questions below regarding your redevelopment pfoject (MS4 Permit Provision E.3.b.(2)):
YES NO
Does the redevelopment project result in the creation or replacement of impervious $Urface 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. O D
Total proposed newly created or replaced impervious area (B) = ___________ ,sq.ft.
Percent impervious area created or replaced (8/A)*tOO = ____ %
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 statin "M to' ectis a PDP .. .'' and com lete a Ii cant infotmation.
00 My project is a POP and must comply with PDP stormwater requirements ofthe BMP Manual. I understand I must
prepare a Storm Water Quality Management Plan (SWQMP) for submittal at time of application.
0 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.
0 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: Gary Arnold Applicant Title:_O~p_e_ra_ti_ng,,_·· _M-'-a_n_ag.._e_r ______ _
Applicant Signature: ~~ :)__ .~ Date: -:fu"N'E. zB~ W\ b
·• 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 Stale Water Resources Control Board (Water Quanty Control Plan for the San Diego Basin (1994) and amendments); water bodies
designated with the RARE beneficial use by \he State Water Resources Control Board. (Water Quality Control Plan for the San Diego Basin (1994) and
amendments); are.is designated as pft:!serves 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.
his ox or City Use Only
YES NO
City Concurrence; 0 D
By:
Date:
Project ID:
E-34 Page 4 of4 REV02/16
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SITE INFORMATION CHECKLIST
Project Name
Project ID
Project Address
Assessor's Parcel Number(s) (APN(s))
Project Watershed (Hydrologic Unit)
Project Hydrologic Unit Hydrologic Area
Parcel Area
(total area of Assessor's Parcel(s)
associated with the project)
Area to be disturbed by the project
(Project Area)
Project Proposed Impervious Area
(subset of Project Area)
Project Proposed Pervious Area
(subset of Project Area)
2200 Afton Way
CT 14-06
2200 Afton Way, Carlsbad, CA
167-531-45 and 167-250-06
12] Carlsbad 904
Select One:
D Loma Alta 904.1
12] Buena Vista Creek 904.2
D Agua Hedionda 904.3
D Encinas 904.4
D San Marcos 904.5
D Escondido Creek 904.6
4.94 Acres ( 214,993 Square Feet)
3.37 Acres ,_-'-14.:....:6'"'-,6=5:a..::5'---Square Feet)
1.26 Acres 54 7 44 Square Feet)
2.11 Acres 91 911 Square Feet)
Note: Proposed Impervious Area+ Proposed Pervious Area= Area to be Disturbed by the
Project.
This may be less than the Parcel Area.
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Current Status of the Site (select all that apply):
IZI Existing development
D Previously graded but not built out
D Agricultural or other non-impervious use
IZI Vacant, undeveloped/natural
Description I Additional Information:
The project site is divided by east and westbound Carlsbad Village Drive. The subject
property located south of Carlsbad Village Drive, known as Parcel 1 for reference, is
approximately 4.57 acres and currently contains a single family residential home, driveway,
and detached garage. The remaining site is vacant and bordered by Carlsbad Village Drive
to the north, and existing residential developments to the east, south, and west. Existing
land-use is 1.00 DU/Ac.
The subject property located north of Carlsbad Village Drive, Parcel 2, is approximately 0.37
acres and is bordered by Carlsbad Village Drive to the south, Rising Glen Way to the east, and
a multi-story apartment complex to the north. Existing land-use is undisturbed natural terrain
and proposes to remain undisturbed.
Existing Land Cover Includes (select all that apply):
D Vegetative Cover
IZI Non-Vegetated Pervious Areas
1Z1 Impervious Areas
Description I Additional Information:
Parcel 1 includes an existing residential house, driveway, and detached garage in the
northwestern portion of the site. The remaining site is undisturbed natural terrain with few
scattered shrubs.
Parcel 2 is an undeveloped hillside with few scattered shrubs.
Underlying Soil belongs to Hydrologic Soil Group (select all that apply):
0 NRCS Type A
IZ! NRCS Type B
0 NRCS Type C
IZ! NRCS Type D
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Approximate Depth to Groundwater (GW):
D GW Depth < 5 feet
D 5 feet < GW Depth < 10 feet
D 10 feet < GW Depth < 20 feet
~ GW Depth > 20 feet
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Existing Natural Hydrologic Features (select all that apply):
D Watercourses
D Seeps
D Springs
D Wetlands
IZI None
Description I Additional Information:
There are no existing natural hydrologic features.
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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]:
Parcel 1 is bordered by Carlsbad Village Drive to the north, and existing residential developments
to the east, south, and west. Topographically, the property consists of gently sloping hillside
terrain with elevations ranging from a high of approximately 280 feet Mean Sea Level (MSL) near
the southwestern property line to a low of approximately 205 feet MSL at the property's
northeastern corner. Currently, the property is occupied by one residential structure with two
sheds. An existing crib wall, approximately 26 feet high and 300 feet long, is located along the
north boundary of the site. Site drainage is presently accomplished through a generally
northeasterly trending ravine and sheet flows southeasterly to drainage facilities along Carlsbad
Village Drive. Existing brow ditches at the top of cut slopes along the southeastern project
boundary direct runoff to existing catch basins, which ultimately discharge into the storm drain
system underneath Carlsbad Village Drive. Existing brow ditches at the top of cut slopes along
the crib wall direct runoff to sidewalk underdrain pipes at various locations along Carlsbad Village
Drive and eventually enter the storm drain system underneath Carlsbad Village Drive via Type-B
Curb Inlet at the east corner of the project boundary. Vegetation consists of native grasses and
eucalyptus trees over the majority of the site. The on-site soil classification is Type-Band Type-
D from USDA Web Soil Survey (see References).
Parcel 2 is bordered by Carlsbad Village Drive to the south, Rising Glen Way to the east, and a
multi-story apartment complex to the north. Topographically, the property is a hillside dominated
by an east to west trending ridge that rises approximately 50 feet above the lowest site terrain
along the northwestern property line. Site terrain continues to support bare ground and scattered
shrubs. The on-site soil classification is Type-D from USDA Web Soil Survey (see References).
The existing drainage area is divided into six basins and one POC, located east of the project site
near Carlsbad Village Drive. The Existing Condition Hydrology Map shows the four drainage
Basins labeled A through D for Parcel 1 and drainage Basins E and F for Parcel 2. Basin A sheet
flows from the southwest side of the existing residence, across the existing driveway and into an
existing brow ditch at the top of the cut slope along the southeasterly project boundary line. An
existing catch basin at the east corner of the project boundary intercepts this runoff and connects
to the existing storm drain system underneath Carlsbad Village Drive.
Basin B sheet flows from the top of the southwesterly ravine and towards the easterly boundary
of the subject property and into an existing brow ditch. The brow ditch conveys flow into an
existing catch basin where it enters the storm drain system underneath Afton Way. This storm
drain system connects with the existing storm drain system underneath Celinda Drive and
eventually Carlsbad Village Drive.
Basin C is limited to the storm flows that land on the existing driveway, with some flow-on from
the ravine located between the neighboring properties and upstream of the driveway. Runoff is
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carried through the existing curb and gutter along the driveway and discharges onto Afton Way
and toward curb inlets on Celinda Drive.
Basin D is north of Basin A and sheet flows from the top of the ridge west of the existing on-site
property and towards Carlsbad Village Drive through a series of brow ditches and sidewalk
underdrain pipes. Basin D also includes run-on coming from the highest point of Carlsbad Village
Drive to the existing Type-B Curb Inlet at the southwest corner of the intersection of Celinda Drive
and Carlsbad Village Drive.
Basin E is in the northwest portion of Parcel 2. Runoff sheet flows from the top of the ridge and
onto Carlsbad Village Drive, then discharges into an existing Type-B Curb Inlet at the northwest
corner of Celinda Drive and Carlsbad Village Drive. Basin E also includes run-on coming from
the highest point of Carlsbad Village Drive to the existing curb inlet.
Basin F is located in Parcel 2 and sheet flows east from the top of the hill towards the existing
parking lot in the back of the existing multi-story apartment complex. This area that acts in a
sheet flow condition comprises of approximately 0.23 acres. Sheet flow analysis is not necessary
for this area as the proposed project does not propose any new impervious area added to Basin
F. In addition, no impervious contributing area is added to Basin E and therefore does not include
a post-development hydrologic analysis.
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Project Description I Proposed Land Use and/or Activities:
The Afton Way Project proposes the development of 8 residential lots and grading of pads and
driveways, and a new public cul-de-sac on Afton Way. The project also proposes drainage facility
improvements consisting of minor concrete drainage channels, storm drain pipes, curb inlets, and
two detention-biofiltration basins for storm water treatment and hydromodification. Storm water
runoff from the project site is routed to one POC, located east of the project site near Carlsbad
Village Drive. Runoff is drained to tow independent onsite receiving biofiltration LID IMPs called
Basin 1 and Basin 2. The disturbed area is approximately 3.37 acres of the 4.94 acre site.
Proposed land-use is 2.88 DU/Ac.
LisVdescribe proposed impervious features of the project (e.g., buildings, roadways, parking
lots, courtyards, athletic courts, other impervious features):
The proposed impervious features of the project include the 8 proposed single-family
residences and driveways and the new cul-de-sac on Afton Way.
LisVdescribe proposed pervious features of the project (e.g., landscape areas):
The proposed pervious features of the project include landscape areas surrounding the
proposed residences and the (2) proposed biofiltration basins on Lot 9.
Does the project include grading and changes to site topography?
[gl Yes
D No
Description I Additional Information:
Project grading will occur on approximately 3.37 acres of the project. Grading on the site has
been minimized to the maximum extent possible. The existing residential house and sheds
located on site will be removed as part of the project. The project as proposed will endeavor to
maintain the existing cross lot drainage condition for both overall rate and flow conditions. See
the OMA Exhibit for post-development drainage patterns. Impervious surfaces have been
minimized where feasible.
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Does the project include changes to site drainage (e.g., installation of new storm water
conveyance systems)?
IZI Yes
D No
Description I Additional Information:
The proposed drainage pattern will be similar to the existing drainage pattern with some
modifications to incorporate the Best Management Practices (BMPs) into the project design to
mimic the impacts on storm water runoff and quality. The proposed runoff from the project site is
divided into five (5) Drainage Management Areas (DMAs): (1) DMA Draining to a Biofiltration IMP
and (4) Self-Mitigating DMAs. One Point of Compliance (POC-1) has been identified at Node
105, which is the point at which the majority of the proposed site runoff will be discharge to the
Carlsbad MS4 system (see Attachment 1 for Drainage Management Area (DMA) Exhibit).
Only Basins A through D are being developed and will consider urban runoff flow rates, durations
and velocities. The developed Basin A, or DMA 1, will encompass runoff from Lots 1-6, which
will be directed to the front of each lot and onto the proposed cul-de-sac. Runoff will then travel
via curb and gutter to a proposed Type-B Curb Inlet on the south side of Afton Way. Runoff from
Lots 7 and 8 will be directed to the front of each lot and onto the proposed cul-de-sac, then travel
via curb and gutter to a proposed Type-B Curb Inlet on the north side of Afton Way. The proposed
curb inlets will connect to a proposed 18"-dia PVC storm drain pipe adjacent to the eastern project
boundary. The 18"-dia storm drain pipe will discharge into a modified Type A-7 Clean Out (per
SDRSD D-09). The cleanout will include (2) orifices to distribute flow. The size of the orifices are
a function of the size of each basin divided by the area of the two basins combined. Once flows
are routed via the proposed orifices, the flows are then conveyed via storm drain pipes to the
receiving biofiltration LID I MPs called Basin 1 and Basin 2 for treatment and detention. Outflows
from the basins will be conveyed via 12"-dia storm drain pipe to the existing Type-B Curb Inlet at
POC-1.
The majority of the off-site run-on from Basin B will be intercepted by a proposed brow ditch along
the southern and eastern project boundary line and directed to a proposed catch basin on the
south side of Afton Way. The catch basin will connect to a proposed 18"-dia storm drain system
which will connect to the existing 18"-dia storm drain system underneath Afton Way and
eventually Carlsbad Village Drive. The existing slopes will remain undisturbed and will drain
directly offsite, therefore being considered a Self-mitigating DMA, SM 1, per Chapter 5 Section
5.2.1 of the City of Carlsbad BMP Design Manual (BMP DM).
The off-site run-on from Basin C will be intercepted by a proposed brow ditch along the western
project boundary line and directed to a proposed catch basin near the congruent property line of
Lot 4 and Lot 5. The catch basin will outlet to a proposed 18"-dia PVC storm drain system which
will travel under the proposed cul-de-sac and connect to the existing 18"-dia storm drain system
underneath Afton Way and eventually Carlsbad Village Drive. The existing slopes will remain
undisturbed and will drain directly offsite, therefore being considered a Self-mitigating DMA, SM
2, per the BMP DM.
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The remaining runoff in Basin D is proposed to be intercepted by the existing brow ditches at the
top of cut slopes along the crib wall and directed to the existing sidewalk underdrain pipes at
various locations along Carlsbad Village Drive. The runoff will then enter the existing storm drain
system underneath Carlsbad Village Drive as historically. The existing slopes will remain
undisturbed and will drain directly offsite, therefore being considered a Self-mitigating OMA, SM-
3, per the BMP OM.
The proposed drainage facility improvements will consist of minor concrete drainage channels,
storm drain pipes, curb inlets, and two detention-biofiltration basins. The biofiltration basins
proposed for the four main Drainage Basins A - D are designed so that increases in the drainage
discharge rate and velocity will be mitigated up to the 100-year runoff. The proposed biofiltration
basins will serve to detain the very minor calculated increase in runoff created by the proposed
development, and to mitigate any concentration of storm water discharge that might cause
erosion.
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Identify whether any of the following features, activities, and/or pollutant source areas will be
present (select all that apply):
C8J On-site storm drain inlets
D Interior floor drains and elevator shaft sump pumps
D Interior parking garages
C8J Need for future indoor & structural pest control
C8J 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
D Vehicle and Equipment Cleaning
D Vehicle/Equipment Repair and Maintenance
D Fuel Dispensing Areas
D Loading Docks
D Fire Sprinkler Test Water
D Miscellaneous Drain or Wash Water
D Plazas, sidewalks, and parking lots
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Describe path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or
reservoir, as applicable):
From the project site, runoff flows into a storm water conveyance system that discharges into
Buena Vista Creek, which eventually discharges into Buena Vista Lagoon and the Pacific
Ocean.
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 Body Pol I utant( s )/Stress or( s) TMDLs
Sediment Toxicity
Buena Vista Creek 904.2
Selenium
Indicator bacteria
Buena Vista Lagoon 904.2 Nutrients
Sedimentation/siltation
Identify pollutants expected from the project site based on all proposed use(s) of the site (see
BMP Design Manual Appendix B.6):
Not Applicable to the Expected from the Also a Receiving
Project Site Project Site Water Pollutant of
Pollutant Concern
Sediment D [gJ [gJ
Nutrients D [gJ [gJ
Heavy Metals D [gJ [gJ
Organic Compounds D [gJ [gJ
Trash & Debris D [gJ [gJ
Oxygen Demanding
Substances D [gJ [gJ
Oil & Grease D [gJ [gJ
Bacteria & Viruses D [gJ [gJ
Pesticides D [gJ [gJ
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Do hydromodification management requirements apply (see Section 1.6 of the BMP Design
Manual)?
IZI Yes, hydromodification management flow control structural BMPs required.
D 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.
D 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.
D 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 I Additional Information (to be provided if a 'No' answer has been selected above):
Project is subject to hydromodificaiton management requirements.
Based on the maps provided within the WMAA, do potential critical coarse sediment yield
areas exist within the project drainage boundaries?
0Yes
IZI 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?
D 6.2.1 Verification of Geomorphic Landscape Units (GLUs) Onsite
D 6.2.2 Downstream Systems Sensitivity to Coarse Sediment
D 6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite
D 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?
D No critical coarse sediment yield areas to be protected based on verification of GLUs
on site
D Critical coarse sediment yield areas exist but additional analysis has determined that
protection is not required. Documentation attached in Attachment 8 of the SWQMP.
D 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 I Additional Information:
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Critical coarse sediment yield areas do not exist on site or upstream of the project.
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.
One Point of Compliance (POC-1) has been identified at the existing Type B curb inlet on the
south side of Carlsbad Village Drive, which is the point at which the majority of the proposed site
runoff will be discharge to the Carlsbad MS4 system (see Attachment 1 for Drainage
Management Area (DMA) Exhibit). A SWMM analysis has been prepared that describes the pre
and post-development hydrologic analysis and ensures that post-development peak flow is less
than or equal to pre-development peak flow for the 6-hour 100-yn ear storm event at the
project's point of compliance (POC-1 ). See the HMP Exhibit and Attachment 2 for
hydromodification control details. See Attachment 5 for copy of SWMM reports.
Has a geomorphic assessment been performed for the receiving channel(s)?
IZ1 No, the low flow threshold is 0.102 (default low flow threshold)
D Yes, the result is the low flow threshold is 0.102
D Yes, the result is the low flow threshold is 0.302
D Yes, the result is the low flow threshold is 0.502
If a geomorphic assessment has been performed, provide title, date, and preparer:
Discussion I Additional Information: (optional)
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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
local codes governing minimum street width, sidewalk construction, allowable pavement
types, and drainage requirements.
The project proposes single family residential dwellings constructed on lots that range from
12,200 sf to 19,200 sf. The space available to install suitable private biofiltration basins is very
limited .
The Type-D soil existing on-site provides little opportunity for infiltration of storm water runoff
into native soils. Storm water strategies that utilize infiltration are not suitable; therefore
biofiltration basins will be lined with an impermeable liner to prevent infiltration of storm water.
The site currently has a northerly-facing slope descending from the project site to Carlsbad
Village Drive. An open space between the grading of pads and the northerly boundary line will
remain untouched to protect the steep slope from failure and erosion. Special precautions must
be taken while grading the pads so that the open space does not channel the flow in any way,
but instead the pads display an even grade and distribute the runoff evenly to the proposed cul-
de-sac.
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Project Name: Afton Way
STANDARD PROJECT
REQUIREMENT
CHECKLIST
E-36
Project 10:CT 14-06, HOP 14-05, HMP 15-03
DWG No. or Building Permit No.:
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 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.
• "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.
SC-1 Prevention of Illicit Discharges into the MS4
Discussion/justification if SC-1 not implemented:
Irrigation water and vehicle and wash water will be directed away from impervious surfaces.
SC-2 Storm Drain Stenciling or Signage IZI Yes D No D N/A
Discussion/justification if SC-2 not implemented:
Storm drains will be stenciled or stamped with anti-dumping message. See OMA Exhibit for location of storm drain inlets.
SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On, Runoff, and Wind
Dispersal
Discussion/justification if SC-3 not implemented:
No outdoor materials storage areas proposed.
E-36 Page 1 of 4
OYes D No IZI N/A
Revised 03/16
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SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On, Runoff, and
Wind Dispersal
Discussion/justification if SC-4 not implemented:
No materials will be stored in outdoor work areas.
SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal O Yes 0 No Ill N/A
Discussion/justification if SC-5 not implemented:
No trash areas proposed.
SC-6 Additional BMPs based on Potential Sources of Runoff Pollutants must answer for each source listed below and
identif additional BMPs. See Table in Appendix E.1 of BMP Manual for uidance .
Ill On-site storm drain inlets OYes 0 No 0 N/A
O Interior floor drains and elevator shaft sump pumps OYes D No Ill N/A
O Interior parking garages OYes 0 No Ill N/A
O Need for future indoor & structural pest control Ill Yes D No 0 N/A
D Landscape/Outdoor Pesticide Use Ill Yes D No 0 N/A
O Pools, spas, ponds, decorative fountains, and other water features OYes 0 No Ill N/A
O Food service OYes D No Ill N/A
O Refuse areas OYes D No Ill N/A
O Industrial processes OYes 0 No 1Z1 N/A
O Outdoor storage of equipment or materials O Yes D No 1Z1 N/A
D Vehicle and Equipment Cleaning OYes 0 No 1Z1 N/A
O Vehicle/Equipment Repair and Maintenance O Yes O No 1Z1 N/A
O Fuel Dispensing Areas O Yes D No 1Z1 N/A
D Loading Docks OYes 0 No IZI N/A
O Fire Sprinkler Test Water OYes D No 1Z1 N/A
O Miscellaneous Drain or Wash Water O Yes D No 121 N/A
121 Plazas, sidewalks, and parkin lots IZi Yes 0 No 0 N/A
For "Yes" answers, identify the additional BMP per Appendix E.1. Provide justification for "No" answers.
An Operation and Maintenance (O&M) Plan will be provided to future occupants that will acknowledge the potential
pollutant sources and provide educational materials to prevent illicit discharges to the storm drain system. The following will
discuss how source control requirements will be applied to the project:
• Storm drain inlets and catch basins will be labeled with "No Dumping Drains to Waterways". See OMA Exhibit for
structural BMP label.
• Pest-resistant or well-adapted plant varieties such as drought tolerant and/or native plants will be planted in landscape
areas. Integrated Pest Management (1PM) educational materials will be distributed to future occupants as a component of
the O&M Plan that address physical pest elimination techniques such as relying on natural enemies to consume pests,
weeding, pruning, and etc.
E-36 Page 2 of 4 Revised 03/16
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.
_J • "Yes" means the project will implement the site design BMPs as described in Chapter 4 and/or Appendix E.2 thru E.6 of
_J
the Model BMP Design Manual. Discussion I 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
rovided.
SD-1 Maintain Natural Drainage Pathways and Hydrologic Features
Discussion/justification if SD-1 not implemented:
The overall drainage patterns of the site will be maintained
SD-2 Conserve Natural Areas, Soils, and Vegetation ~Yes D No D N/A
Discussion/justification if SD-2 not implemented:
Natural areas will exist on the project site due to minimized grading.
SD-3 Minimize Impervious Area Ill Yes D No D N/A
Discussion/justification if SD-3 not implemented:
_J Landscape buffers will be incorporated between sidewalks and Afton Way.
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SD-4 Minimize Soil Compaction Ill Yes D No D N/A
Discussion/justification if SD-4 not implemented:
Soil compaction will be minimized in natural landscape areas. Disturbed slope soils will also be amended and aerated.
SD-5 Impervious Area Dispersion IZJ Yes D No D N/A
Discussion/justification if SD-5 not implemented:
Landscape will effectively receive and infiltrate, and treat runoff from impervious areas as much as possible. Roof drains
will be directed to landscape areas prior to discharging to storm water conveyance.
E-36 Page 3 of 4 Revised 03/16
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Discussion/justification if SD-6 not implemented:
Although landscape areas will effectively receive and infiltrate runoff as much as possible into native soils, the landscape
areas are not designed to retain runoff in a way that can be credited towards reducing the overall DCV.
SD-7 Landscaping with Native or Drought Tolerant Species Ill Yes D No ON/A
Discussion/justification if SD-7 not implemented:
Slope soils will be amended, aerated, and planted with native or drought tolerant non-native plants. Other landscape or
pervious areas will incorporate native or drought tolerant landscape design.
OYes 0 No ON/A
No rain-water harvesting strategies proposed. Harvest and use is considered to be infeasible for this project. See Form 6
in Attachment 1 c for Harvest and Use Feasibility Checklist.
E-36 Page 4 of 4 Revised 03/16
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SUMMARY OF 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 local jurisdiction 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 local jurisdiction 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 (page 3 of this form) 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 or separate.
For the purpose of this SWOMP, the proposed site condition has been divided into (5) Drainage
Management Areas (DMAs): (1) OMA Draining to a Biofiltration IMP and (4) Self-Mitigating
DMAs. The DMAs have been delineated based on onsite drainage patters and BMP locations.
Biofiltration basins (BF-1) were chosen as the structural BMP for DMAs draining to I MPs. Two
biofiltration basins, Basin 1 and Basin 2, will be used for pollutant control and peak flow control
for the project stormwater runoff.
The outlet structure for Basin 1 and Basin 2 have been designed based on results from the
Technical Memorandum: SWMM Modeling for Hydromodification Compliance for Afton Way,
dated April 9, 2015 from Tory R. Walker Engineering under separate cover (see Attachments
section of this Report for copy of Technical Memorandum). This SWMM Model demonstrates
Hydromodification Compliance at the proposed basins for the 02 to 010 return periods as
specified in the County of San Diego Hydromodification Plan (HMP). Based on the hydrologic
model used in the technical memorandum titled above, a separate SWMM analysis has been
prepared that describes the pre and post-development hydrologic analysis ensures that post-
development peak flow is less than or equal to pre-development peak flow for the 6-hour 100-
year storm event at the project's point of compliance (POC-1 ). See References for copy of Title
Page, Technical Memorandum: Determination of Pre-and Post-Developed 100-year Peak Flow
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from Tory R. Walker Engineering dated June 17, 2015. The Rational Method study provided in
the associated Drainage Report for this project incorporates the outlet structure design in the
Technical Memorandum, and is meant to enhance the study from Tory R. Walker Engineering,
Inc. to show the site can sufficiently convey the 100 year storm event.
The two I MPs are responsible for handling hydromodification requirements for the project site. In
developed conditions, both Basins 1 and 2 will have a surface depth of 3 feet and 2.5 feet, and a
riser spillway structure (see dimensions in the DMA/IMP Sizing Exhibit in Attachments). Flows
will discharge from the biofiltration cells via a low flow orifice outlet within the gravel layer or a
surface slot with the riser structure. The top of the riser structure will act as a spillway, such that
peak flows can be safely discharged to the receiving storm drain system.
Beneath the invert of the basins' lowest surface discharge lies the proposed LID biofiltration
portion of the drainage facility. This portion of the basins is comprised of 12 inches of surface
storage, an 18-inch layer of amended soil (a highly sandy, organic rich composite with an
infiltration capacity of at least 5 inches/hr.) and a 12-inch layer of gravel for additional detention
and to accommodate the French drain system. These systems will treat storm water and convey
flows to a small diameter lower outlet orifice. Once flows have been routed by the outlet
structures, flows will then discharge independently from each basin to the receiving POC
discharge location.
The biofiltration basins were modeled using the biofiltration LID module within SWMM. Please
refer to Appendix 1 of the Technical Memorandum: Determination of Pre-and Post-Developed
100-year Peak Flow for details explaining the biofiltration module.
The DCV for DMA 1 has been calculated based on the proposed impervious roof and landscape
areas draining to each BMP. Worksheet B.5-1 in Attachment 1 d further demonstrates that the
full DCV can be treated within the biofiltration BMPs.
Based on recommendations from the Geotechnical report, infiltration from the biofiltration basins
is not considered to be appropriate for the project. The bottom of the basins will be lined with an
impermeable liner to prevent infiltration of storm water. See copy of Geotechnical report titled
"Geotechnical Investigation, Proposed Afton Way Residential Development for 2200 Afton Way,
Carlsbad, CA", by Leighton and Associates, Inc. in Attachments section.
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Structural BMP ID No. Basin 1
DWG Sheet No.
Type of structural BMP:
D Retention by harvest and use (HU-1)
D Retention by infiltration basin (INF-1)
D Retention by bioretention (INF-2)
D Retention by permeable pavement (INF-3)
D Partial retention by biofiltration with partial retention (PR-1)
~ Biofiltration (BF-1)
D Flow-thru treatment control with prior lawful approval to meet earlier PDP requirements
(provide BMP type/description in discussion section below)
D 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)
D Flow-thru treatment control with alternative compliance (provide BMP type/description in
discussion section below)
D Detention pond or vault for hydromodification management
D Other (describe in discussion section below)
Purpose:
D Pollutant control only
D Hydromodification control only
~ Combined pollutant control and
hydromodification control
D Pre-treatment/forebay for another structural
BMP
D Other (describe in discussion section below)
Discussion (as needed):
Basin 1 will be used for pollutant control and peak flow control for the project stormwater runoff.
The outlet structure for Basin 1 has been designed based on results from the Technical
Memorandum: SWMM Modeling for Hydromodification Compliance for Afton Way, dated April 9,
2015 from Tory R. Walker Engineering under separate cover (see Attachments section of this
Report for copy of Technical Memorandum). See Attachment 1 for DCV calculations.
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Structural BMP ID No. Basin 2
DWG Sheet No.
Type of structural BMP:
D Retention by harvest and use (HU-1)
D Retention by infiltration basin (INF-1)
D Retention by bioretention (INF-2)
D Retention by permeable pavement (INF-3)
D Partial retention by biofiltration with partial retention (PR-1)
[8J Biofiltration (BF-1)
D Flow-thru treatment control with prior lawful approval to meet earlier PDP requirements
(provide BMP type/description in discussion section below)
D 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)
D Flow-thru treatment control with alternative compliance (provide BMP type/description in
discussion section below)
D Detention pond or vault for hydromodification management
D Other (describe in discussion section below)
Purpose:
D Pollutant control only
D Hydromodification control only
[8J Combined pollutant control and
hydromodification control
D Pre-treatment/forebay for another structural
BMP
D Other (describe in discussion section below)
Discussion (as needed):
Basin 2 will be used for pollutant control and peak flow control for the project stormwater runoff.
The outlet structure for Basin 2 has been designed based on results from the Technical
Memorandum: SWMM Modeling for Hydromodification Compliance for Afton Way, dated April 9,
2015 from Tory R. Walker Engineering under separate cover ( see Attachments section of this
Report for copy of Technical Memorandum). See Attachment 1 for DCV calculations.
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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) IZI Included
Attachment 1 b
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
D Included on OMA Exhibit in
Attachment 1 a
IZI Included as Attachment 1 b,
separate from OMA Exhibit
Attachment 1 c Form 1-7, Harvest and Use Feasibility IZI Included
Attachment 1 d
Attachment 1 e
Screening Checklist (Required unless D Not included because the entire
the entire project will use infiltration project will use infiltration BMPs
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.
IX! Included
D Not included because the entire
project will use harvest and use
BMPs
Pollutant Control BMP Design IZI Included
Worksheets I Calculations (Required)
Refer to Appendices B and E of the
BMP Design Manual for structural
pollutant control BMP design
guidelines
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Attachment 1 a
DMA Exhibit
26
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K,\Civil 3D\1326\PROD\DWG\HYDRO & SWMP\1326-DMA-HMP EXHIBIT.dwg, 11/11/201611:06'44 AM
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'-UNDERDRAIN '-f":'J/:: ,,:,. ' ,. ' . ,,
-i,: DRAINAGE MANAGEMENT AREA EXHIBIT
~
AFTON WAY SUBDIVISION, CARLSBAD, CA
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PROJECT CHARACTERISTICS
SOIL TYPE B&D
PROJECT AREA 4.94 ACRES
DISTURBED AREA 3.37 ACRES
PROPOSED IMPERVIOUS AREA 1.26 ACRES
PROPOSED PERVIOUS AREA 2.11 ACRES
GENERAL NOTES
1. BIOFILTRATION BASINS TO BE USED AS COMBINED POLLUTANT
CONTROL AND FLOW CONTROL BMP. I,
2. BIOFILTRATION BASINS TO INCLUDE A PERFORATED UNDERDRAIN
PIPE WITH A LOW FLOW ORIFICE BELOW THE BOTTOM OF THE GROWING
MEDIUM. BIOFILTRA TION BASINS TO INCLUDE AN IMPERMEABLE LINER
BELOW THE GRAVEL LAYER TO RESTRICT INFILTRATION.
3. THE OUTLET STRUCTURE FOR BASlr, 1 AND BASIN 2 HAVE BEEN
DESIGNED BASED ON RESULTS FROM Tl;IE "TECHNICAL MEMORANDUM:
SWMM MODELING FOR HYDROMODIFICATION COMPLIANCE FOR AFTON
WAY, CITY OF CARLSBAD, REVISED JUNE 17, 2015", PREPARED BY
TORY R. WALKER ENGINEERING. SEE SWQMP FOR COPY OF REPORT.
l SC-1 l
lSC-2l
JSC-6l
[6]
[Q]
SOURCE CONTROL BMPS:
PREVENTION OF ILLICIT DISCHARGES INTO THE MS4
STORM DRAIN STENCILING AND SIGNAGE
ADDITIONAL BMPS BASED ON POTENTIAL RUNOFF POLLUTANTS:
ON-SITE STORM DRAIN INLETS
NEED FOR FUTURE INDOOR & STRUCTURAL PEST CONTROL
l1J LANDSCAPE/OUTDOOR PESTICIDE USE
[Q] PLAZAS, SIDEWALKS, DRIVEWAYS, AND PARKING LOTS
l SD-1
lSD-2
lSD 3
!SD 4
LID AND SITE DESIGN=
MAINTAIN NATURAL DRAINAGE PATHWAYS AND HYDROLOGIC FEATURES
CONSERVE NATURAL AREAS, SOILS, AND VEGETATION
MINIMIZE IMPERVIOUS AREA
MINIMIZE SOIL COMPACTION
l SD 5 l IMPERVIOUS AREA DISPERSION
l SD-7 l LANDSCAPING WITH NATIVE OR DROUGHT TOLERANT SPECIES
LEGEND:
DMA DRAINING TO IMP
SELF MIT/GA TING DMA
POINT OF CONCENTRATION
DMA LIMIT
FLOW DIRECTION
BIOFIL TRA TION BASIN
CONCRETE CUL-DE-SAC
IMPERVIOUS DR/1-f'WA Y
RIP RAP ENERGY DISS/PATER
PROPER TY LINE
BROW DITCH
SOIL CLASS/FICA TION
BOUNDARY
OMA 1
SM 1
POC 1
f+++++I
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SELF-MITIGATING DMAS=
VEGETATION IN THE NATURAL OR LANDSCAPE AREA IS
NATIVE OR NON-NATIVE DROUGHT TOLERANT SPECIES.
SOILS ARE UNDISTURBED NATIVE TOPSOIL.., OR DISTURBED
SOILS HAVE BEEN AMENDED AND AERATt.D TO PROMOTE
WATER RETENTION CHARACTERISTICS EQUIVALENT TO
UNDISTURBED NATIVE TOPSOIL.
INCIDENTAL IMPERVIOUS AREAS ARE LESS THAN 5
PERCENT OF THE SELF-MITIGATING AREA.
IMPERVIOUS AREAS CALCULATED WITHIN THE
SELF-MITIGATED AREA SHOULD NOT BE HYDRAULICALLY
CONNECTED TO OTHER IMPERVIOUS AREAS UNLESS IT IS
A STORM WATER CONVEYANCE SYSTEM (SUCH AS BROW
DITCHES).
THE SELF-MITIGATING AREA IS HYDRAULICALLY
SEPARATE FROM DMAS THAT CONTAIN PERMANENT
STORM WATER POLLUTION CONTROL BMPS.
r1\
..... ·.7·· .. ·····
'
.
PROHBllVE DUMPING SIGNAGE
TYPE B BROW DITCH~
PER SDRSD D-75
:>l'W 220· -DEEP ROOTED, DENSE, DROUGHT
SLOT ORIFICE TO ALLOW
700 YR PREDEVELOPMENT
FLOW
18" ENGINEERED
SOIL MIX
1' V2 STORAGE LA YER """'--
(2"-PEA GRAVEL 01-f'R '-
10"-3/4" CRUSHED ROCK) 2125'
6" PERFORATED PVC
UNDERDRAIN PIPE
-T01£f!ANT PLANTING SUITABLE ~
FOR WEU._ DRAINED SOIL \
TYPE G-1 CATCH BASIN WITH GRATED INLET
TW 215'
BASIN 1
FOR POST DEVELOPMENT IOOYR FLOW
214.25 RIM -
'D BASIN .2c.----"< -
209.25'
./"' EXIST. GROUND <r-TYPE G-1 CATCH BASIN
--JYITH GRATED INLET FOR POST
DEI/UOPMENT IOOYR FLOW
'--'!'..'. 210· -----
n·\ -
PLACE PIPE WITH PERFORATIONS ~El~::~,"-
AT THE INVERT BW 210'-207.5'
2.5' v -
[=::r~::+---:7'-SLOT ORIFICE TO ALLOI(
700 YR PREDEVEL OPMEN T
FLOW
IMPERMEABLE LINER THROUGHOUT----"
RESTRICTOR PLATE TO LIMIT FLOW FROM V2
STORAGE AREA, 2.25" DRAIN DOWN HOLE
·1---RESTRICTOR PLATE AT END OF
i,,;;,s:;,J PERF PIPE IN BASIN 2 TO LIM/ T
FLOW FROM V2 STORAGE AREA,
1.00" DRAIN DOWN HOLE 18" ENGINEERED SOIL MIX PER
G.1. 5. J. 1 OF BMP DESIGN MANUAL ----
STORM DRAIN CASING--i]2~03~.~76~~~:::~~~:;;==::=:j
~lfEiO~U~T~~~=:l~_j~~;==~ 203.07 g_o3 BW IE OUT OUTFLOW
/' V2 STORAGE LA YER
{2"-PEA GRA 1-f'L OVER
10"-3/4" CRUSHED ROCK)
12" HDPE 6" PERFORATED PVC UNDERDRAIN
PIPE
PLACE PIPE WITH PERFORATIONS
AT THE INVERT
SECTION: '~-A II
12" HOPE OUTLET PIPE
FROM RISER/BASIN 1
IMPERMEABLE LINER
THROUGHOUT
-OUTLET PIPE
BIOFILTRATION BASIN DETAIL
NOT TO SCALE
50' 100' 150'
~~~iiiiiiiiiiiii~~
SCALE: 1" = 50'
b~A,lnc.
land planning, cMI engineering, surveying
5115 AVENIDA ENCINAS
SUITE "L"
CARLSBAD, CA. 92008-4387
(760) 931-8700
DRAINAGE MANAGEMENT
AREA EXHIBIT
AFTON WAY SUBDIVISION
CARLSBAD, CA
Attachment 1 b
Tabular Summary of DMAs and Design Capture Volume Calculations
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DMA Impervious Area Tabulation
Surface Name Surface T e
R1 Conventional Roof and Patio
PCC1 Concrete Drivewa
R2 Conventional Roof and Patio
PCC2 Concrete Driveway
R3 Conventional Roof and Patio
PCC3 Concrete Driveway
R4 Conventional Roof and Patio
PCC4 Concrete Driveway
RS Conventional Roof and Patio
PCCS Concrete Drivewa
R6 Conventional Roof and Patio
PCC6 Concrete Driveway
R7 Conventional Roof and Patio
PCC7 Concrete Drivewa
RS Conventional Roof and Patio
PCCS Concrete Drivewa
AC1 As
ervious Area ft2
DMA Pervious Area Tabulation
Surface Name
L1
L2
L3
L4
LS
L6
L7
LS
L9
Total Pervious Area (ft2)
TotalDMA A
Total Im ervious Area (ft2) /Total DMA ft2) = Percent Impervious
Soil T
DMA Runoff Coefficient "C"
85th Percentile Rainfall (I)
ture Volume VC) = C)(I)(A) / 12
28
Area (ft2
3,500
1,040
3,500
2,000
3,500
4,040
3,500
1,324
3,500
1,450
3,500
1,920
3,500
2,2S9
3,500
1,533
11,14S
54,744
5,S49
7,09S
10,S99
10,761
7,316
11,105
12,496
19,927
4,193
S9,644
144,3SS
3S%
D
0.53
0.6
3,808
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D MA Classification Quantity Subtotal DMA (ft2) Subtotal DMA (acres)
Self-Miti a. 4 139,312 3.20
0 0 0
Surfaces Dr · · DMAs 0 0 0
Bioretention IMPs 0 0 0
1 Flow Thro h Planter IMPs 2 144,025 3.31
J Infiltration IMP 0 0 0
Conventional Ve etated Swale 0 0 0
Extended (D ) Detention Basins 0 0 0
Media (Sand) Filter 0 0 0
l Wet Pond 0 0 0
j Constructed Wetland 0 0 0
0 0 0
Inlet Filter 0 0 0
Areas Not Feasible to Treat 0 0 0
--, Total DMA 283,337 6.50
Total Parcel Area 214,993 4.94
I Comment:
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Attachment 1 c
Form 1-7, Harvest and Use Feasibility Screening Checklist
1. Is there a demand for harvested water (check all that apply) at the project site that is reliably present during the
wet season?
IZ! Toilet and urinal flushing
IZ! Landscape irrigation
D 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.
Modified ETWU = ETowe,x [[L(PF x HA)/IE] + SLA] x O.Q15
Using an average value for HA over the 8 residential lots and Low Plant Water Use (per Table B.3-2);
Modified ETWU = 2.7 x [[(0.2 x 91,911)/0.9] + OJ x O.o15
Modified ETWU = 827
(Total pervious area= 91,911 sf)
3. Calculate the DCV using worksheet B-2.1.
DCV = ~3=8~0~8 ___ ( cubic feet)
3a. Is the 36 hour demand greater
than or equal to the DCV?
D Yes I ~ No
~ c:>
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.
3b. Is the 36 hour demand greater than
0.25DCV but less than the full DCV?
D Yes I ~ No
~ c:>
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.
32
3c. Is the 36 hour demand
less than 0.25DCV?
~ Yes
Harvest and use is considered
to be infeasible.
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Is harvest and use feasible based on further evaluation?
D Yes, refer to Appendix E to select and size harvest and use BMPs.
IZ! No, select alternate BMPs
Harvest and use BMPs are considered infeasible. Drought tolerant landscape, as proposed in SD-7 in Form E-36,
requires low plant water use. Project will implement other LID strategies such as impervious area dispersion. The
full DCV can be treated in the proposed biofiltration basins. Property owners will be encouraged to use rain
barrels after construction to reduce runoff volumes.
33
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Attachment 1 d
Form 1-8, Categorization of Infiltration Feasibility Condition
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.
Provide basis:
No
Percolation testing was performed in the location of the proposed biofiltration basins to evaluation
suitability of the site for infiltration of storm water. According to the Geotechnical Investigation, 2200 Afton
W ~' Carlsbad, CA by Leighton and Associates, Inc., "The results of the percolation test indicated that the
site soils had a percolation rate of greater than 125 minutes per inch (mpi). Generally a percolation rate
less than 120 mpi is considered necessary to consider a site suitable for onsite infiltration of storm water.
Additionally the presence of shallow clayey sand and clay materials present in much of the site would be
expected to impede infiltration and a 30-mil HDPE should be considered to line any proposed infiltration
basin."
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.
Provide basis:
Yes
According to the Geotechnical Investigation, "the presence of shallow clayey sand and clay materials
present in much of the site would be expected to impede infiltration." Clayey sand and clay materials have
a high shrink-swell potential, a high water table, a claypan or clay layer at or near the surface, and are
shallow over nearly impervious material. These soils have a very slow rate of water transmission. It is also
noted by geotechnical engineer that saturation of storm water into the proposed slopes can result in shallow
slope failure. But provided that the recommendations contained in the geological report are incorporated
into the final design, subsurface and surface water are not anticipated to affect site development.
34
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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.
Provide basis:
No
Although groundwater was not encountered within the geotechnical report, an infiltration rate greater than
0.5 inches per hour cannot be achieved.
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.
Provide basis:
No
Although there are no potential water balance issues or contaminated groundwater, an infiltration rate
greater than 0.5 inches per hour cannot be achieved .
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
35
No
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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
AppendixD.
Provide basis:
Yes
Per the Geotechnical Investigation, "percolation test indicated that the site soils had a percolation rate of greater
than 125 minutes per inch (mpi). Generally a percolation rate less than 120 mpi is considered necessary to
consider a site suitable for onsite infiltration of storm water." Additionally the presence of shallow clayey
sand and clay materials present in much of the site would be expected to impede infiltration and a 30-rnil
HDPE should be considered to line any proposed infiltration basin." Therefore the soil will allow for a
percolation rate greater than 125 mpi, although the rate is unacceptable for a suitable infiltration basin. See
Attachment 8 of Technical Memorandum: SWMM Modeling for Hydromodificaiton Compliance of: Afton
Way, Carlsbad, CA for copy of geotechnical study.
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.
Provide basis:
No
Based on recommendations from the geotechnical report, infiltration basins could "potentially create
adverse perched ground water conditions both on-site and off-site. Therefore given the site geologic
conditions, impermeable subsurface material, and project type, infiltration type LID measures are not
considered to be appropriate for this site and project, 30 mil HDPE Liners should be used where detention
areas are proposed near slopes or retaining walls, near buildings, or over utilities."
36
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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.
Provide basis:
See comment to Criteria 6.
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.
Provide basis:
No
Yes
The project will mimic existing drainage conditions. There are no downstream water rights applicable.
Part 2
Result
*
If all answers from row 5-8 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.
37
No
Infiltration
Attachment 1 e
Pollutant Control BMP Design Worksheets I Calculations
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BMP1
3 Allowable drawdown time for a
4 Depth of runoff that can be infiltrated [Line 2 x Line 3]
5 A
6 Required depth of gravel below the underdrain [Line 4 / Line 5]
7 Assumed surface area of the biofiltration BMP
8 Media retained pore space
9 Volume retained by BMP [[Line 4 + (Line 12 x Line 8)]/12] x Line 7
10 DCV that requires biofiltration [Line 1 -Line 9]
11 Surface Ponding [6 inch minimum, 12 in maximum]
12 Media Thickness [18 inches minimum]
13 Aggregate Storage above underdrain invert (12 inches typical -use O inches for
14
17
18
27 Foot rint of the BMP = Maximum(Minimum(Line 21, Line 23), Line 26)
.J Used BMP Foot rint
__ .)
39
, _ _)
hours
inches
in/in
inches
2,290 sq-ft
in/in
cubic-feet
3,803 cubic-feet
12 inches
18 inches
12 inches
30 inches
15.6 inches
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1) The biofiltration basin has be designed in accordance with City of Carlsbad BMP Design
Manual (BMP DM) sizing criteria, which includes minimum BMP footprint and draw
down requirements. The DMA has been delineated based on onsite drainage patterns and
BMP locations. Based on Chapter 3 Section 3.3.3 of the BMP DM, a single DMA may
not drain to more than one BMP. Therefore the biofiltration BMP must be sized to treat
the DCV from the total drainage area draining to the BMP.
Used BMP Footprint= 2,290 sf= 1,805 sf (Basin 1) + 485 sf (Basin 2)
2) Since partial infiltration is considered infeasible, the infiltration rate in Line 2 is set to 0
inches/hour. Therefore the volume retained by the BMP is essentially O cubic-feet and
the DCV that requires biofiltration, Line 10, is equal to Line 1.
40
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The applicant must provide documentation of compliance with each criterion in this checklist as
part of the project submittal. The right column of this checklist identifies the submittal information
that is recommended to document compliance with each criterion. Biofiltration BMPs that
substantially meet all aspects of Fact Sheets PR-1 or BF-1 should still use this checklist; however
additional documentation (beyond what is already required for project submittal) should not be
required.
·· ····· ·········· · ··· i-:Si~ftltt~tion BMPs must be allowed td. be used only as d~-~cribed • in t:he BMP
selection process based on a documented feasibility analysis;
Intent: This manual defi111:;s a specific prioritization of pollutant treatment BMPs; where Blvf Ps that
retain<water (retained includes evapotranspired, infiltrated, and/or harvested and used) mµstbe used
before considering BMPs thathave a biofiltered discharge to the M§4 or surface waters .. Use of a
bioftlti:ation BMP in a manner in conflict with this .prioritization Q.e., without a feasibility analysis
justifying its use) is not permitted, rega,rdless. of the adequacy of the sizing and design of the system,
•••v•••v••••w,••••• • ••••-••••• .... •••••• ••••_,.,_.,~,. .. ~••• .. v,.-•••-,.•••vn .. •v•••• ,-a. .. v,-•••-••«v-••--~ ••• , •••• ••••, '"""" • •••w•'""""'""vnssw,,••••v .... wn•"~
The project applicant has demonstrated that it D 1: 'bili' 1 . d fi d' · . . . . ocument 1eas1 ty ana ys1s an m mgs m
1s not techrucally feasible to retam the full DCV th SWQMP A di C
onsite. e per ppen x .
""'""~""""""""" "'""""""'"""""""M""VNNS.VN""" " .......... '> """""">'>N'SSU•""'"'""'"'"""""'~~-""'"""""' _, """"""'"'"""""""'" """"'M"''''"""'°"'""'-
2. Biofiltration BMPs must be sized<using acceptable sizing methods.
Intent; The MS4 Permitand this manual defmes specific sizing methods that must be used to size
blofiltration BMPs. Sizing of biofilttation BMPs is a.fundamental factor in the amount of storm
water that can be treated and also influences volume aµd pollutant retention processes.
The project applicant has demonstrated that
biofiltration BMPs are sized to meet one of the
biofiltration sizing options available (Appendix
B).
Submit sizing worksheets (Appendix B) or
other equivalent documentation with the
SWQMP.
········ ·············"···,·· .................... "._ .. ,."······ ............................................................... ._._ ...
3. Biofiltration BMPs must be sited and designed to achieve maximum feasible
infiltration.and.evapotranspiration.
Intent: Various decisions about BMP placement and design influence how much water is retained via
inttltration and evapotranspiratioh. Thf JvIS4 Perriiit: requires that bioftltratlon BMPs achieve
maximunifeasible retention ( evapotranspiratlon a.nd infiltration) of storm water volume.
, __ )
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D
D
The biofiltration BMP is sited to allow for
maximum infiltration of runoff volume based
on the feasibility factors considered in site
planning efforts. It is also designed to
maximize evapotranspiration through the use
of amended media and plants (biofiltration
designs without amended media and plants may
be permissible; see Item 5).
For biofiltration BMPs categorized as "Partial
Infiltration Condition," the infiltration storage
depth in the biofiltration design has been
selected to drain in 36 hours or an alternative
value shown to maximize infiltration on the
site.
-----------------·--··--····-------------
For biofiltration BMP locations categorized as
"Partial Infiltration Condition," the infiltration
storage is over the entire bottom of the
biofiltration BMP footprint.
For biofiltration BMP locations categorized as
"Partial Infiltration Condition," the sizing
factor used for the infiltration storage area is
not less than the minimum biofiltration BMP
sizing factors calculated using Worksheet B.5.3.
An impermeable liner or other hydraulic
restriction layer is only used when needed to
avoid geotechnical and/ or subsurface
contamination issues in locations identified as
"No Infiltration Condition."
The use of "compact" biofiltration BMP design
is permitted only in conditions identified as
"No Infiltration Condition" and where site-
specific documentation demonstrates that the
use of larger footprint biofiltration BMPs
would be infeasible.
Document site planning and feasibility analyses
in the SWQMP per Section 5.4.
Included documentation of estimated
infiltration rate per Appendix D; provide
calculations using Appendix B.4 and B.5 to
show that the infiltration storage depth meets
this criterion. Note, depths that are too shallow
or too deep may not be acceptable.
Document on plans that the infiltration storage
covers the entire bottom of the BMP (i.e., not
just underdrain trenches); or an equivalent
footprint elsewhere on the site.
Provide a table that compares the minimum
sizing factor from Appendix B.5 to the
provided sizing factor. Note: The infiltration
storage area could be a separate storage feature
located downstream of the biofiltration BMP,
not necessarily within the same footprint.
If using an impermeable liner or hydraulic
restriction layer, provide documentation of
feasibility findings per Appendix C that
recommend the use of this feature.
Provide documentation of feasibility findings
that recommend no infiltration is feasible.
Provide site-specific information to
demonstrate that a larger footprint biofiltration
BMP would not be feasible.
'"'''""-· ----------------,----·---•--M'-••-"•"M"••-'-••------•••• --"--~--•,ceM.-.e._,._______________ ""''-""'"""M"" .-c .. ,.,c._,.,_ • ._,,__, --------------------
4. · Bioftltration BMPs must be designed with a hydraulic loading rate to maximize
pollutant retention, preserve pollutant conttol processes, and minimize potential for
pollutant washout.
Intent:Various decisions ~boutbiofiltration BMP design influence the degree to which pollutants are
retained. The· MS4 Permit requires that biofiltration. BMPs achieve maximum feasible retention of
storm water pollutants,
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••••on••""""'""""""
Media selected for the biofiltration BMP meets
minimum quality and material specifications
per 2016 City Storm Water Standards or
County LID Manual, including the maximum
allowable design filtration rate and minimum
thickness of media.
OR
Alternatively, for proprietary designs and
custom media mixes not meeting the media
specifications contained in the 2016 City Storm
Water Standards or County LID Manual, field
scale testing data are provided to demonstrate
that proposed media meets the pollutant
treatment performance criteria in Section F.1
below.
. ........ ,, .... ,. .... ,. ... ,,, .... ,..
To the extent practicable, filtration rates are
outlet controlled ( e.g., via an underdrain and
orifice/weir) instead of controlled by the
infiltration rate of the media.
Provide documentation that media meets the
specifications in 2016 City Storm Water
Standards or County LID Manual.
Provide documentation of performance
information as described in Section F.1.
Include outlet control in designs or provide
documentation of why outlet control is not
practicable.
........ ················· ··················
The water surface drains to at least 12 inches
below the media surface within 24 hours from
the end of storm event flow to preserve plant
health and promote healthy soil structure.
If nutrients are a pollutant of concern, design
of the biofiltration BMP follows nutrient-
sensitive design criteria.
Media gradation calculations or geotextile
selection calculations demonstrate that
migration of media between layers will be
prevented and permeability will be preserved.
Include calculations to demonstrate that
drawdown rate is adequate.
Surface ponding drawdown time greater than
24-hours but less than 96 hours may be allowed
at the discretion of County staff if certified by a
landscape architect or agronomist.
Follow specifications for nutrient sensitive
design in Fact Sheet BF-2. Or provide
alternative documentation that nutrient
treatment is addressed and potential for
nutrient release is minimized.
Follow specification for choking layer or
geotextile in Fact Sheet PR-1 or BF-1. Or
include calculations to demonstrate that
choking layer is appropriately specified.
5. Biofiltration BMPs ~ust be desigped ·t,>promote appropriate biological activity to
support attd maintain treatment processes.
Intent: Biological processes are an impottarit element .ofbioftltration performance and longevity.
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Plants have been selected to be tolerant of
project climate, design ponding depths and the
treatment media composition.
Plants have been selected to minimize irrigation
requirements.
····································· .................... .
Plant location and growth will not impede
expected long-term media filtration rates and
will enhance long term infiltration rates to the
extent possible.
If plants are not part of the biofiltration design,
other biological processes are supported as
needed to sustain treatment processes (e.g.,
biofilm in a subsurface flow wetland).
Provide documentation justifying plant
selection. Refer to the plant list in Appendix
E.20 .
..................................... ....................... .
Provide documentation describing irrigation
requirements for establishment and long term
operation .
Provide documentation justifying plant
selection. Refer to the plant list in Appendix
E.20.
.. ................ ,. ... _, .......... -. .................... """""'"
For biofiltration designs without plants,
describe the biological processes that will
support effective treatment and how they will
be sustained.
6 .. Bioft1.t;;tlon· IiKfi=,~·-must be design~d with i-·-hydrautic toarlh~i·;;te .. to-·prevent
erosion, scour, and. channeling within the BMP .
D
Intent: Erosion, scour,. and/or channeling ca,n disrupt treatment processes and reduce biofiltration
effectiveness.
Scour protection has been provided for both
sheet flow and pipe inflows to the BMP, where
needed.
........................ _. ... ,. .... ,, .. _.,,_. ..
Where scour protection has not been provided,
flows into and within the BMP are kept to non-
erosive velocities .
.....................................................
For proprietary BMPs, the BMP is used in a
Provide documentation of scour protection as
described in Fact Sheets PR-1 or BF-1 or
approved equivalent .
Provide documentation of design checks for
erosive velocities as described in Fact Sheets
PR-1 or BF-1 or approved equivalent.
manner consistent with manufacturer Provide copy of manufacturer
guidelines and conditions of its third-party recommendations and conditions of third-party
certification 19 (i.e., maximum tributary area, certification.
maximum inflow velocities, etc., as applicable) .
19 Certifications or verifications issued by the Washington Technology Acceptance Protocol-Ecology program and the
New Jersey Corporation for Advanced Technology programs are typically accompanied by a set of guidelines regarding
appropriate design and maintenance conditions that would be consistent with the certification/verification
7.
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Biofiltratiort BMP •· must include operations. an4 maintenance . ctesign !eatures . and
planning considerations for continued .. effectiveness of pollutant and · flow control
functions.
Intent: Biofiltration BMPs require regufat maintenance in order provide ongoing function as
intended. Adclitib11ally,h is nof possible to fore:see and avoid potentiaLissues as patt of design;
therefore plans must be 1h place to correct issut:s ff they arise ..
...........................
The biofiltration BMP maintenance plan
describes specific inspection activities,
regular/periodic maintenance activities and
specific corrective actions relating to scour,
erosion, channeling, media clogging, vegetation
health, and inflow and outflow structures.
Adequate site area and features have been
provided for BMP inspection and maintenance
access.
For proprietary biofiltration BMPs, the BMP
maintenance plan is consistent with
manufacturer guidelines and conditions of its
third-party certification (i.e., maintenance
activities, frequencies).
Include maintenance plan with the SWQMP as
described in Chapter 7.
Illustrate maintenance access routes, setbacks,
maintenance features as needed on project
water quality plans.
Provide copy of manufacturer
recommendations and conditions of third-party
certification.
J
1
Potential Sources of
Runoff Pollutants
[8] A. Onsite storm drain
inlets
D Not Applicable
[8]
! __
2
Permanent Controls-Show on
Drawings
Locations of inlets.
L--_!
3 4
Permanent Controls-List in Table
and Narrative
Operational BMPs-Include in
Table and Narrative
[8] Mark all inlets with the words "No I [8]
Dumping! Flows to Bay" or similar.
See stencil template provided in I [8]
Appendix I-4
Maintain and periodically repaint
or replace inlet markings.
Provide storm water pollution
prevention information to new
site owners, lessees, or operators.
[8] See applicable operational BMPs
in Fact Sheet SC-44, "Drainage
System Maintenance," in the
CASQA Storm Water Quality
Handbooks at
,v\vw.casqa.org/ resources/bmp-
handbooks/rnunicipal-bmp-
handbook.
[8] Include the following in lease
agreements: "Tenant shall not
allow anyone to discharge
anything to storm drains or to
store or deposit materials so as to
create a potential discharge to
storm drains."
L
D
Iii
D
IXI
IB]
D
1
Potential Sources of
Runoff Pollutants
B. Interior floor
drains and elevator
shaft sump pumps
Not Aeelicable
C. Interior parking
·garages.
Not Applicable
D1. Need for future
indoor & structural
pest control
Not Applicable
J :__
2
Permanent Controls-Show on
Drawings
__J ~
3
Permanent Controls-List in Table
and Narrative
D State that interior floor drains and
elevator shaft sump pumps will be
plumbed to sanitary sewer.
D State that parking garage floor
drains will be plumbed to the
sanitary sewer.
4
Operational BMPs-lnclude in
Table and Narrative
D Inspect and maintain drains to
prevent blockages and overflow.
D Inspect and maintain drains to
prevent blockages and overflow.
IB] Note building design features that I IBl
discourage entry of pests.
Provide Integrated Pest
Management information to
owners, lessees, and operators.
1
Potential Sources of
Runoff Pollutants
IBl D2. Landscape/
Outdoor Pesticide
Use
0 Not Applicable
2
Permanent Controls-Show on
Drawings
[8]
[8]
[8]
Show locations of existing
trees or areas of shrubs and
ground cover to be
undisturbed and retained.
Show self-retaining landscape
areas, if any.
Show storm water treatment
facilities.
3
Permanent Controls-List in Table and
Narrative
State that final landscape plans will I IBl
accomplish all of the following.
IBl Preserve ex1stmg drought tolerant I IBl
trees, shrubs, and ground cover to the
maximum extent possible.
IBl Design landscaping to m1rum1ze
irrigation and runoff, to promote
surface infiltration where appropriate,
and to minimize the use of fertilizers
and pesticides that can contribute to
storm water pollution.
IBl Where landscaped areas are used to
retain or detain storm water, specify
plants that are tolerant of periodic
saturated soil conditions.
IBl Consider using pest-resistant plants,
especially adjacent to hardscape.
IBl To ensure successful establishment,
select plants appropriate to site soils,
slopes, climate, sun, wind, rain, land
use, air movement, ecological
consistency, and plant interactions.
I IBl
4
Operational BMPs-lnclude in
Table and Narrative
Maintain landscaping using
minimum or no pesticides.
See applicable operational
BMPs in Fact Sheet SC-41,
"Building and Grounds
Maintenance," in the CASQA
Storm Water Quality
Handbooks at
www.casqa.org/resources /bmp
-handbooks /municipal-bmp-
handbook.
Provide IPM information to
new owners, lessees and
operators.
I,.::.._ __ __]
1
Potential Sources of
Runoff Pollutants
D E. Pools, spas,
ponds, decorative
fountains, and other
water features.
ii Not Applicable
D F. Food service
ii Not Applicable
L__ -~r '·--_J
2 3 I 4
D
Permanent Controls-Show on
Drawings
Show location of water feature
and a sanitary sewer cleanout in
an accessible area within 10 feet.
Permanent Controls-List in Table
and Narrative
D If the local municipality requires
pools to be plumbed to the sanitary
sewer, place a note on the plans and
state in the narrative that this
connection will be made according to
local requirements.
D For restaurants, grocery stores, I D Describe the location and features of
the designated cleaning area. and other food service
operations, show location I 0
(indoors or in a covered area
outdoors) of a floor sink or other
area for cleaning floor mats,
containers, and equipment.
D On the drawing, show a note that
this drain will be connected to a
grease interceptor before
discharging to the sanitary sewer.
Describe the items to be cleaned in
this facility and how it has been sized
to ensure that the largest items can be
accommodated.
Operational BMPs-Include
in
Table and Narrative
D See applicable operational
BMPs in Fact Sheet SC-72,
"Fountain and Pool
Maintenance," in the CASQA
Storm Water Quality
Handbooks at
www.casqa.org/resources /bm
p-handbooks/municipal-
bmp-handbook.
1
Potential Sources
of
D G. Refuse areas
ll9 Not Applicable
2
Permanent Controls-Show
on Drawings
D Show where site refuse and
recycled materials will be
handled and stored for
pickup. See local municipal
requirements for sizes and
other details of refuse areas.
D If dumpsters or other
receptacles are outdoors,
show how the designated
area will be covered, graded,
and paved to prevent run-
on and show locations of
berms to prevent runoff
from the area. Also show
how the designated area will
be protected from wind
dispersal.
D Any drains from dumpsters,
compactors, and tallow bin
areas must be connected to
a grease removal device
before discharge to sanitary
sewer.
3
Permanent Controls-List
in Table and Narrative
D State how site refuse will
be handled and provide
supporting detail to what
is shown on plans.
D State that signs will be
posted on or near
dumpsters with the
words "Do not dump
hazardous materials
here" or similar.
4
Operational BMPs-lnclude in
Table and Narrative
D State how the following will be implemented:
Provide adequate number of receptacles. Inspect
receptacles regularly; repair or replace leaky
receptacles. Keep receptacles covered.
Prohibit/prevent dumping of liquid or hazardous
wastes. Post "no hazardous materials" signs. Inspect
and pick up litter daily and clean up spills
immediately. Keep spill control materials available
on-site. See Fact Sheet SC-34, "Waste Handling and
Disposal" in the CASQA Storm Water Quality
Handbooks at www.casqa.org/resources/bmp-
handbooks /municipal-bmp-handbook.
_J
1
Potential Sources of
Runoff Pollutants
D H. Industrial
processes.
IXI Not Applicable
D I. Outdoor storage
of equipment or
materials. (See rows J
and K for source
control measures for
vehicle cleaning,
repair, and
maintenance.)
IX! Not Applicable
L L J
2
Permanent Controls-Show on
Drawings
D Show process area.
D
D
Show any outdoor storage
areas, including how materials
will be covered. Show how
areas will be graded and
bermed to prevent run-on or
runoff from area and
protected from wind dispersal.
Storage of non-hazardous
liquids must be covered by a
roof and/ or drain to the
sanitary sewer system, and be
contained by berms, dikes,
liners, or vaults.
D Storage of hazardous materials
and wastes must be in
compliance with the local
hazardous materials ordinance
and a Hazardous Materials
Management Plan for the site.
L
3
Permanent Controls-List in Table and
Narrative
D If industrial processes are to be located
onsite, state: "All process activities to be
performed indoors. No processes to
drain to exterior or to storm drain
system."
D Include a detailed description of
materials to be stored, storage areas, and
structural features to prevent pollutants
from entering storm drains.
Where appropriate, reference
documentation of compliance with the
requirements of local Hazardous
Materials Programs for:
• Hazardous Waste Generation
• Hazardous Materials Release
Response and Inventory
• California Accidental Release
Prevention Program
• Aboveground Storage Tank
• Uniform Fire Code Article 80
Section 103(b) & (c) 1991
• Underground Storage Tank
4
Operational BMPs-Include
in Table and Narrative
Table and Narrative
D See Fact Sheet SC-10, "Non-
Storm Water Discharges" in
the CASQA Storm Water
Quality Handbooks at
https://v,lww.casqa.org/resou
rces/bmp~handbooks.
D See the Fact Sheets SC-31,
"Outdoor Liquid Container
Storage" and SC-33,
"Outdoor Storage of Raw
Materials" in the CASQA
Storm Water Quality
Handbooks at
W\Vw.casqa.org /resources /bm
p-handbooks/municipal-bmp-
handbook.
1
Potential Sources of
Runoff Pollutants
D J. Vehicle and
Equipment Cleaning
IXI Not Applicable
2
Permanent Controls-Show on Drawings
D Show on drawings as appropriate:
(1) Commercial/industrial facilities having
vehicle / equipment cleaning needs must
either provide a covered, bermed area for
washing act1v1t1es or discourage
vehicle/ equipment washing by removing
hose bibs and installing signs prohibiting such
uses.
(2) Multi-dwelling complexes must have a
paved, bermed, and covered car wash area
(unless car washing is prohibited onsite and
hoses are provided with an automatic shut-
off to discourage such use).
(3) Washing areas for cars, vehicles, and
equipment must be paved, designed to
prevent run-on to or runoff from the area,
and plumbed to drain to the sanitary sewer.
( 4) Commercial car wash facilities must be
designed such that no runoff from the facility
is discharged to the storm drain system.
Wastewater from the facility must discharge
to the sanitary sewer, or a wastewater
reclamation system must be installed.
L
3
Permanent Controls-List in
Table and Narrative
D If a car wash area is not
provided, describe measures
taken to discourage onsite
car washing and explain how
these will be enforced.
4
Operational BMPs-Include in
Table and Narrative
Describe operational measures to
implement the following (if
applicable):
D Washwater from vehicle and
equipment washing operations
must not be discharged to the
storm drain system.
D Car dealerships and similar
may rinse cars with water
only.
D See Fact Sheet SC-21,
"Vehicle and Equipment
Cleaning," in the CASQA
Storm Water Quality
Handbooks at
www.casqa.org/resources/bm
p-handbooks/municipal-bmp-
handbook.
1
Potential Sources of
Runoff Pollutants
D K.
Vehicle/Equipment
Repair and
Maintenance
l8l Not Applicable
D
D
D
2
Permanent Controls-Show on
Drawings
Accommodate all vehicle
equipment repair and
maintenance indoors. Or
designate an outdoor work area
and design the area to protect
from rainfall, run-on runoff, and
wind dispersal.
Show secondary containment for
exterior work areas where motor
oil, brake fluid, gasoline, diesel
fuel, radiator fluid, acid-
containing batteries or other
hazardous materials or hazardous
wastes are used or stored. Drains
must not be installed within the
secondary containment areas.
Add a note on the plans that
states either (1) there are no floor
drains, or (2) floor drains are
connected to wastewater
pretreatment systems prior to
discharge to the sanitary sewer
and an industrial waste discharge
permit will be obtained.
L
Permanent Controls-List in
Table and Narrative
Operational BMPs-Include in
Table and Narrative
D
D
State that no vehicle repair or
maintenance will be done
outdoors, or else describe the
required features of the
outdoor work area.
State that there are no floor
drains or if there are floor
In the report, note that all of the following
restrictions apply to use the site:
D No person must dispose of, nor permit
the disposal, directly or indirectly of
vehicle fluids, hazardous materials, or
rinsewater from parts cleaning into
storm drains.
drains, note the agency from I 0
which an industrial waste
discharge permit will be
obtained and that the design
meets that agency's
requirements.
D State that there are no tanks,
containers or sinks to be used
for parts cleaning or rinsing
No vehicle fluid removal must be
performed outside a building, nor on
asphalt or ground surfaces, whether
inside or outside a building, except in
such a manner as to ensure that any
spilled fluid will be in an area of
secondary containment. Leaking
vehicle fluids must be contained or
drained from the vehicle immediately.
or, if there are, note the I 0
agency from which an
industrial waste discharge
permit will be obtained and
that the design meets that
agency's requirements.
No person must leave unattended drip
parts or other open containers
containing vehicle fluid, unless such
containers are in use or in an area of
secondary containment.
1
Potential Sources of
Runoff Pollutants
D L. Fuel Dispensing
Areas
~ Not Applicable
2
Permanent Controls-Show on
Drawings
D Fueling areas 16 must have
impermeable floors (i.e., portland
cement concrete or equivalent smooth
impervious surface) that are (1) graded
at the minimum slope necessary to
prevent ponding; and (2) separated
from the rest of the site by a grade
break that prevents run-on of storm
water to the MEP.
D Fueling areas must be covered by a
canopy that extends a minimum of ten
feet in each direction from each
pump. [Alternative: The fueling area
must be covered and the cover's
minimum dimensions must be equal
to or greater than the area within the
grade break or fuel dispensing areal.]
The canopy [or cover] must not drain
onto the fueling area.
3
Permanent Controls-List
in Table and Narrative
4
Operational BMPs-Include in
Table and Narrative
D The property owner must dry sweep
the fueling area routinely.
D See the Business Guide Sheet,
"Automotive Service-Service
Stations" in the CASQA Storm
Water Quality Handbooks at
https: //www.casqa.org/resources /b
mp-handbooks.
16 The fueling area must be defined as the area extending a minimum of 6.5 feet from the comer of each fuel dispenser or the length at which the hose and nozzle assembly may be
operated plus a minimum of one foot, whichever is greater.
1
Potential Sources of
Runoff Pollutants
M. Loading Docks
IXI Not Applicable
__J _j
2
Permanent Controls-Show on
Drawings
D Show a preliminary design for the
loading dock area, including
roofing and drainage. Loading
docks must be covered and/ or
graded to minimize run-on to and
runoff from the loading area. Roof
downspouts must be positioned to
direct storm water away from the
loading area. Water from loading
dock areas should be drained to
the sanitary sewer where feasible.
Direct connections to storm
drains from depressed loading
docks are prohibited.
D Loading dock areas draining
directly to the sanitary sewer must
be equipped with a spill control
valve or equivalent device, which
must be kept closed during
periods of operation.
D Provide a roof overhang over the
loading area or install door skirts
(cowling) at each bay that enclose
the end of the trailer.
, _
3
Permanent
Controls-List in
. __J I __
4
Operational BMPs-Include in
Table and Narrative
D Move loaded and unloaded items indoors as
soon as possible.
D See Fact Sheet SC-30, "Outdoor Loading and
Unloading," in the CASQA Storm Water
Quality Handbooks at
www.casqa.org/resources/bmp-
handbooks/municipal-bmp-handbook.
1
Potential Sources of
Runoff Pollutants
D N. Fire Sprinkler
Test Water
Ix! Not Applicable
0. Miscellaneous Drain
or Wash Water
D Boiler drain lines
D Condensate drain
lines
D Rooftop
equipment
D Drainage sumps
D Roofing, gutters,
and trim
IX) Not Applicable
2
Permanent Controls-
Show on Drawings
D
L_
3
Permanent Controls-List in Table and
Narrative
Provide a means to drain fire sprinkler test water
to the sanitary sewer.
D Boiler drain lines must be directly or indirectly
connected to the sanitary sewer system and may
not discharge to the storm drain system.
D Condensate drain lines may discharge to
landscaped areas if the flow is small enough that
runoff will not occur. Condensate drain lines
may not discharge to the storm drain system.
D Rooftop mounted equipment with potential to
produce pollutants must be roofed and/ or have
secondary containment.
D Any drainage sumps onsite must feature a
sediment sump to reduce the quantity of
sediment in pumped water.
D Avoid roofing, gutters, and trim made of copper
or other unprotected metals that may leach into
runoff.
4
Operational BMPs-Include in
Table and Narrative
D See the note in Fact Sheet SC-
41, "Building and Grounds
Maintenance," in the CASQA
Storm Water Quality
Handbooks at
www.casqa.org/resources/bm
p-handbooks/municipal-bmp-
handbook
1
Potential Sources of
Runoff Pollutants
1211 P.
sidewalks,
parking lots.
0 Not Applicable
Plazas,
and
_j ' L. J L
2
Permanent Controls-Show on
Drawings
L L __ L _j
3
Permanent Controls-List in
Table and Narrative
j
4
Operational BMPs-lnclude in
Table and Narrative
IXI Plazas, sidewalks, and parking lots must
be swept regularly to prevent the
accumulation of litter and debris.
Debris from pressure washing must be
collected to prevent entry into the
storm drain system. Washwater
containing any cleaning agent or
degreaser must be collected and
discharged to the sanitary sewer and
not discharged to a storm drain.
,_j
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,,
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, _ _j
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 Contents Checklist
Seauence
Attachment 2a Hydromodification Management ~ Included
Exhibit (Required)
See Hydromodification Management
Exhibit Checklist on the back of this
Attachment cover sheet.
Attachment 2b Management of Critical Coarse ~ Exhibit showing project drainage
Sediment Yield Areas (WMAA boundaries marked on WMAA
Exhibit is required, additional Critical Coarse Sediment Yield Area
analyses are optional) Map (Required)
See Section 6.2 of the BMP Design Optional analyses for Critical
Manual. Coarse Sediment Yield Area
Determination
D 6.2.1 Verification of Geomorphic
Landscape Units Onsite
D 6.2.2 Downstream Systems
Sensitivity to Coarse Sediment
D 6.2.3 Optional Additional
Analysis of Potential Critical Coarse
Sediment Yield Areas Onsite
Attachment 2c Geomorphic Assessment of ~ Not performed
Receiving Channels (Optional) D Included
See Section 6.3.4 of the BMP Design
Manual.
Attachment 2d Flow Control Facility Design and ~ Included
Structural BMP Drawdown
Calculations (Required)
See Chapter 6 and Appendix G of
the BMP Design Manual
41
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Attachment 2a
Hydromodification Management Exhibit
42
------------------------------------------··----
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K:\Civil 3D\1326\PROD\DWG\HYDRO & SWMP\1326 -DMA-HMP EXHIBIT,dwg, 11/11/201610:36:52 AM
--~------·-----------·--· ···-------··-,-----------------------
PROPOSED CONDITION HYDROMODIFICATION MANAGEMENT EXHIBIT . -. ' ' ' ' '. ' ' ,' ' .
;.:· ' \
\
PROPOS[D:
_:J>:BROW ,:
:,, ', DITCH '-'!
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AFTON WAY SUBDIVISION, CARLSBAD, CA
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LEGEND:
DMA DRAINING TO IMP
SELF MlllGA TING DMA
POINT OF CONCENTRATION
OMA LIMIT
FLOW DIRECTION
BIOFIL TRA TION BASIN
CONCRETE CUL-DE-SAC
IMPERVIOUS DRIVEWAY
RIP RAP ENERGY DISS/PATER
PROPERTY LINE
BROW DITCH
SOIL CLASS/FICA TION
BOUNDARY
DMA ,1
SM I
POC 1
I++~+ +I
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~
PROJECT CHARACTERISTICS
SOIL TYPE B&D
PROJECT AREA 4.94 ACRES
DISTURBED AREA 3.37 ACRES
PROPOSED IMPERVIOUS AREA 1.26 ACRES
PROPOSED PERV/OUS AREA 2.11 ACRES
GENERAL NOTES
1. BIOFILTRATION BASINS TO BE USED AS COMBINED POLLUTANT
CONTROL AND FLOW CONTROL BMP. -
2. BIOFIL TRA TION BASINS TO INCLUDE A PERFORATED UNDERDRAIN
PIPE WITH A LOW FLOW ORIFICE BELOW THE BOTTOM OF THE
GROWING MEDIUM. BIOFIL TRATION BASINS TO INCLUDE AN
IMPERMEABLE LINER BELOW THE GRAVEL LA YER TO RESTRICT
INFILTRATION.
3. THE OUTLET STRUCTURE FOR BASIN 1 AND BASIN 2 HA VE BEEN
DESIGNED BASED ON RESULTS FROM THE "TECHNICAL MEMORANDUM:
SWMM MODELING FOR HYDROMODIFICATION COMPLIANCE FOR AFTON
WAY, CITY OF CARLSBAD, REVISED JUNE 17, 2015", PREPARED BY
TORY R_ WALKER ENGINEERING. SEE SWQMP FOR COPY OF REPORT.
TYPE B BROW DITCH --ILA"i ;>JW ~· DEEP ROOTED, DENSE. DROUGHT
PER SDRSD D-75 ------TO!.f!?_ANT PLANTING SUITABLE ~
FOR WRL_ DRAINED SOIL _ . _ \
SLOT ORIFICE TO ALLOW ------_TYPE G-7 CATCH BASIN WITH GRATED INLET
700 YR PREDEVELOPMENT TW 215.5' FOR POST DEVELOPMENT 100YR FLOW
FLOW 2 14,25 RIM -------EXIST GROUND 18" ENGINEERED BASIN ~
SOIL MIX -____ TYPE G-1 CATCH BASIN
1 • V2 STORAGE LA YER ~ c:, BASIN--"2_ -____WfTH GRATED INLET FOR POST
"i DtVE'tOPMENT 100YR FLOW (2"-PEA GRAVEL OVER , ~ 210'
10"-J/4" CRUSHED ROCK) 21Z5 209.25' ~---------,.---___
6" PERFORATED PVC
UNDERDRAIN PIPE
PLACE PIPE WITH PERFORATIONS _J=f!;!~~"-
AT THE INVERT BW 270'
IMPERMEABLE LINER THROUGHOUT---_.,,
RESTRICTOR PLATE TO LIMIT FLOW FROM V2 ·
STORAGE AREA, 2.25" DRAIN DOWN HOLE '
18" ENGINEERED SOIL MIX PER
G_ 1.5,J.1 OF BMP DESIGN MANUAL ----
STORM DRAIN CASING------
SECTION· '~-A"
BIOFILTRATION BASIN DETAIL
NOT TO SCALE
SU~MARY OF DEVELOPED DUAL PURPOSE IMP
BIOFIL TRA TION BMP AREA GRAVEL AMENDED SURFACE LOWER
DEPTH, DEPTH ORIFICE IMP (SF) (1) (IN) (2) SOIL (IN) (FT) (3) (IN) (4)
BASIN 1 1,805 12 18 12, 30 1.25
BASIN 2 485 12 18 12, JO 1.25
NOTES: (1) AREA OF AMENDED SOIL AREA EQUAL TO AREA OF
GRAVEL.
(2) GRAVEL DEPTH NEEDED TO COMPLY WITH
HYDROMODIFICA TION CONDITIONS.
(3) FIRST NUMBER IS THE SURFACE DEPTH OF THE BMP UP
TO THE SLOT INVERT. SECOND NUMBER IS THE TOTAL
SURFACE DEPTH FROM BOTTOM OF SURFACE POND TO TOP OF
POND WALL.
(4) DIAMETER OF ORIFICE IN GRAVEL LAYER WITH INVERT AT
BOTTOM OF LA YER; TIED WITH HYDROMOD MIN
THRESHOLD (10%Q2).
50· 1 oo· 150'
111111111111111111111111~ 1._._iiiii I """"""""""""~I
SCALE: 1" = 50'
b~A,lnc.
land planning, cMI engineering , suiveylng
5115 AVENIDA ENCINAS
SUITE "L"
CARLSBAD, CA. 92008-4387
(760) 931-8700
SUMMARY OF BIOFILTRATION BASIN
RISER DETAILS
HMP SLOT DIMENSIONS SLOT WEIR LENGTH, INVERT DETENTION BSLOT ELEVATION INVERT
BASIN H (IN) (IN) (IN) (1) ELEVATION (2)
BASIN 1 3 24 12 8' @ 1. 75' ELEV.
BASIN 2 3 24 12 8' @ 1. 75' ELEV.
NOTES: (1) ALL ELEVATIONS MEASURED FROM THE BOTTOM OF
THE SURFACE BASIN.
(2) ASSUMED J' X 3' BOX RISER WITH INTERNAL 2' X
2' OPENING (8 FEET INTERNAL PERIMETER) .
PROPOSED CONDITION
HYDROMODIFICATION
MANAGEMENT EXHIBIT
AFTON WAY SUBDIVISION
CARLSBAD, CA
I
--"
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Attachment 2b
WMAA Exhibit
43
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Attachment 2d
Flow Control Facility Design and Structural BMP Drawdown Calculations
See "Technical Memorandum: SWMM Modeling for Hydromodification Compliance of Afton
Way, City of Carlsbad, Revised June 17, 2015", prepared by Tory R. Walker Engineering.
See "Technical Memorandum: Determination of Pre-and Post-Developed 100-year Peak Flow,
Afton Way, City of Carlsbad, June 17, 2015': prepared by Tory R. Walker Engineering .
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DEEP ROOTED, DENSE, DROUGHT
::::-TOLERANT PLANTING SUITABLE
L L
SLOT ORIFICE TO ALLOW
100 YR ?REDEVELOPMENT
FLOW
FOR--w£LL__QRAINED SOIL ~
TYPE G-1 CATCH BASIN WITH GRATED INLET
TW 215' / FOR POST DEVELOPMENT 100YR FLOW
' 214.25 RIM ......___
18" ENGINEERED
SOIL MIX
1' V2 STORAGE LAYER~
(2"-PEA GRAVEL OVER "'-
10"-3/4" CRUSHED ROCK) 212.5'
6" PERFORATED PVC
UNDERDRAIN PIPE
PLACE PIPE WITH PERFORATIONS
BASIN 1
ATTHEINVERT BW 210' , ..... , .. ;~.; 5 t~
IMPERMEABLE UNER THROUGHOUT-----
RESTRICTOR PLATE TO LIMIT FLOW FROM V2
STORAGE AREA, 2.25" DRAIN DOWN HOLE
18" ENGINEERED SOIL MIX PER
G.1.5.3.1 OF BMP DESIGN MANUAL
~ EXIST. GROUND
~;-TYPE G-1 CATCH BASIN
Wf__TH GRATED INLET FOR POST
D£T1£L-OeyENT 100YR FLOW
......___ ,,210'
'-...___ ~ '-...___
OT ORIFICE TO ALL-e.14(
100 YR PREDEVELOPMENT
FLOW
·• RESTRICTOR PLATE AT END OF
PERF PIPE IN BASIN 2 TO LIM/i
FLOW FROM V2 STORAGE AREA,
1. 00" DRAIN DOWN HOLE
1' V2 STORAGE LA YER
I ~ t \ .a~ -203.07
203 BW 7-,.:;:I \ \ -;,IE OUT
(2"-PEA GRAVEL OVER
10"-3/4" CRUSHED ROCK)
-12" HOPE 6" PERFORATED PVC UNDERDRAIN
PIPE
PLACE PIPE WITH PERFORATIONS
AT THE INVERT
203.40
IE IN
12" HOPE OUTLET PIPE
FROM RISER/BASIN 1
IMPERMEABLE LINER
THROUGHOUT SECTION· '11-A"
BIOFILTRATION BASIN DETAIL ··----..
OUTLET PIPE
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TABLE 1-Summary Of Developed Dual Purpose IMP
IMP DIMENSIONS
Biofiltration BMPArea<1> Gravel Amended Soil Surface Lower Orifice
IMP (ft2) Depth<2> (in) (in) Depthl4 l (in) D (in)l3l
Basin 1 1,805 12 18 12,30 1.25
Basin 2 485 12 18 12,30 1.25
Notes: (1): Area of amended soil equal to area of gravel.
(2): Gravel depth needed to comply with hydromodification conditions.
(3): Diameter of the orifice in the gravel layer with invert at bottom of layer, tied with HMP min.
threshold (10%Qz).
(4): First number is the surface depth of the BMP up to the slot invert. Second number is the total
surface depth from bottom of surface pond to top pond wall.
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B --1
SLOI IN\/Er9 T ELE\l
t
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Btot = BOX D1fv1ENSi01\/
NOT TO SCALE
TABLE 2-Summary Of Biofiltration Basin Riser Details
Slot Dimensions Slot Invert
HMP Detention Elevationl 1> (in) Weir Length,
Basin Hs (in) BsLor (in) Invert Elevationl 2>
Basin 1 3 24 12 8'@ 1.75' Elev.
.. .I Basin 2 3 24 12 8'@ 1.75' Elev.
Notes: (1): All elevations measured from the bottom of the surface of the basin.
(2): Assumed 3' x 3' box riser with internal 2' x 2' opening (8 feet internal perimeter).
47
------------------··-------·--A .... --
jJ =
ORIFICE DETAIL
_ _J IMP D(in) d (in)
1 6 1.25
2 6 1.25
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JNlET 1fr
SD UNE B
B~
4.oo' I
2.00' . . , 12.00~ .•
B
PLAN VIEW
SECTJONA-A
OUTLET 12"
SD UNF B2
SECTIONB .. B
MODIFIED TYPEA-4 CLEAN OUT DETAIL
NOT ro SCALE
49
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Structural BMP Maintenance Information
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Attachment 3a
Structural BMP Maintenance Thresholds and Actions
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PRIVATE TREATMENT CONTROL BMP
OPERATION AND MAINTENANCE VERIFICATION FORM
BIORETENTION FACILITIES, VEGETATED SWALES & HIGHER RATE
BIOFILTERS
1. Transcribe the following information from your notification letter and make corrections as necessary:
Permit No.:
BMP Location:
Responsible Party:
Phone Number: Email:
Responsible Party Address:
Number Street Name & Suffix City/Zip
D Check here for Address or phone number change
2. Using the Table below, please describe the inspections and maintenance activities that have been conducted during
the fiscal year (July 1 -June 30), and date(s) maintenance was performed. Under "Results of Inspection," indicate
whether maintenance was required based on each inspection, and if so, what type of maintenance. If maintenance
was required, provide the date maintenance was conducted and a description of the maintenance. REFER TO
THE BACK OF THIS SHEET FOR MORE INFORMATION DESCRIBING TYPICAL
MAINTENANCE INDICATORS AND MAINTENANCE ACTIVITIES. If no maintenance was required
based on the inspection results, state "no maintenance required."
Results of
Inspection: Date Maintenance Completed and
Date Work needed? Description of Maintenance Conducted
What To Look For? Inspected (Yes/No)
Accumulation of
Sediment, Litter,
Grease
Standing Water
Erosion
Overgrown
Vegetation
Poor Vegetation
Establishment
Structural Damage
3. Attach copies of available supporting documents (photographs, copies of maintenance contracts, and/or
maintenance records).
4. Sign the bottom of the form and return to:
Signature of Responsible Party
County of San Diego Watershed Protection Program
Treatment Control BMP Tracking
5201 Ruffin Road, Suite P, MS 0326
San Diego, CA 92123 OR
Email: Watersheds@sdcounty.ca.gov
Print Name Date
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PRIVATE TREATMENT CONTROL BMP
OPERATION AND MAINTENANCE VERIFICATION FORM
BIORETENTION FACILITIES, VEGETATED SWALES & HIGHER RATE
BIOFIL TERS-SIDE 2
This guide sheet provides general indicators for maintenance only and for a wide array of treatment
control BMPs. Your developer prepared maintenance plans specifically for your treatment control
BMP as an appendix to the Stormwater Management Plan. Also, if you have a manufactured
structure, please refer to the manufacturer's maintenance instructions.
Biofilters include the following :
a Vegetated Filter Strip/Swale a Bioswale a Bioretention Facility a Planter Boxes
a Manufactered Higher-Flow-Rate Biofilters, such as Tree-Pit-Style Units.
Routine maintenance is needed to ensure that flow is unobstructed, that erosion is prevented, and that soils are held
together by plant roots and are biologically active. Typical maintenance consists of the following:
Bioretention BMPs Inspection and Maintenance Checklist
Typical Maintenance Indicators Typical Maintenance Actions
Accumulation of sediment (over 2 inches deep or Remove and properly dispose of accumulated materials,
covers vegetation), litter, or debris without damage to the vegetation. Confirm that soil is not
clogging and that the area drains after a storm event. Till
or replace soil as necessary.
Poor vegetation establishment Ensure vegetation is healthy and dense enough to provide
filtering and to protect soils from erosion. Replenish mulch
as necessary (if less than 3 inches deep), remove fallen
leaves and debris, prune large shrubs or trees, and mow
turf areas.
Overgrown vegetation-woody vegetation not part Mow or trim as appropriate, but not less than the design
of design is present and grass excessively tall height of the vegetation (typically 4-6 inches for grass).
(greater than 10 inches) Confirm that irrigation is adequate and not excessive and
that sprays do not directly enter overflow grates. Replace
dead plants and remove noxious and invasive weeds.
Erosion due to concentrated irrioation flow Repair/re-seed eroded areas and adjust the irrioation.
Erosion due to concentrated stormwater runoff flow Repair/re-seed eroded areas and make appropriate
corrective measures such as adding erosion control
blankets, adding stone at flow entry points, or re-grading
where necessary.Remove obstructions and sediment
accumulations so water disperses.
Standing water (BMP not draining) . If mosquito Where there is an underdrain, such as in planter boxes
larvae are present and persistent, contact the San and manufactured biofilters, check the underdrain piping
Diego County Vector Control Program at (858) 694-to make sure it is intact and unobstructed. Abate any
2888. Mosquito larvicides should be applied only potential vectors by filling holes in the ground in and
when absolutely necessary and then only by a around the biofilter facility and by insuring that there are
licensed individual or contractor. no areas where water stands longer than 96 hours
followino a storm .
Obstructed inlet or outlet structure Clear obstructions.
Damage to structural components such as weirs, Repair or replace as applicable.
inlet, or outlet structures
Before the wet season and after rain events: remove Where cisterns are part of the system
sediment and debris from screens and overflow
drains and downspouts; ensure pumps are
functioning, where applicable; check integrity of
mosquito screens; and; check that covers are
properly seated and locked.
For manufactured high-flow-rate biofilters, see
manufacturer's maintenance guidelines
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Attachment 3b
Draft Maintenance Agreement
I. Purpose and Scope
This section was prepared based on the Chapter 7 of City of Carlsbad BMP Design Manual The
goal is to insure that the Project proponent accepts responsibility for all facilities maintenance,
repair, and replacement from the time they are constructed until the ownership and maintenance
responsibilities is formally transferred to the new owner. Facilities shall be maintained in perpetuity
and comply with the City's self-inspection, reporting, and verification requirements.
II. Inspection, Maintenance Log and Self-Verification Forms
Fill the forms on the following pages for each BMP using the maintenance schedule here and the
inspection-maintenance checklists in Section VII. These forms shall be signed by the responsible
party and retained for at least (5) years. Use the OMA Exhibit for the location of BMPs. (Make
duplicate copies of these forms and fill out those, not the original ones.)
Ill. Updates, Revisions and Errata
This maintenance plan is a living document and based on the changes made by maintenance
personnel, such as replacement of mechanical equipments, addition maintenance procedure
shall be added and maintenance plan shall be kept up to date.
Please add the revisions and updates to the maintenance plan to this section if any, these
revisions maybe transmitted to the City at any time. However, at a minimum, updates to the
maintenance plan must accompany the annual inspection report.
IV. Introduction
The 2200 Afton Way Project is located in the City of Carlsbad. The project site is divided by east
and westbound Carlsbad Village Drive. The subject property located south of Carlsbad Village
Drive, known as Parcel 1 for reference, is approximately 4.56 acres and is bordered by Carlsbad
Village Drive to the north, and existing residential developments to the east, south, and west.
Currently, the property is occupied by one residential structure with two sheds.
The subject property located north of Carlsbad Village Drive, Parcel 2, is approximately 0.36 acres
and is bordered by Carlsbad Village Drive to the south, Rising Glen Way to the east, and a multi-
story apartment complex to the north. Existing land-use is undisturbed natural terrain and
proposes to remain undisturbed. For the nature of this report, only Parcel 1 is proposing to be
developed.
The project site drains to one Point of Compliance (POC), located east of the project site near
Carlsbad Village Drive.
The project proposes the development of eight (8) residential lots and related drainage features.
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The project also proposes (2) biofiltration basins for storm water treatment and detention. The
biofiltration basins will discharge into a proposed storm drain system which will discharge at an
existing Type B curb inlet on the south side of Carlsbad Village Drive, also shown as POC-1 on
the OMA Exhibit.
V. Responsibility for Maintenance
A. General
Presidio Pebble Creek Carlsbad & LLC will enter into a Stormwater Facilities Maintenance
Agreement (SWFMA) with the City of Carlsbad to maintain designated facilities herein this
section for the Afton Way Project.
The SWFMA will serve as the mechanism to ensure that proper inspection and maintenance
is done in an efficient and timely manner.
Responsible Party
Presidio Pebble Creek Carlsbad & LLC
301 West 281h Street, Suite A
National City, CA 91950
Presidio Pebble Creek Carlsbad & LLC will have the direct responsibility for maintenance of
Stormwater controls. A Home Owner's Association (HOA) shall be formed, or establish
another mechanism to the satisfaction of the City. Funding for the maintenance activities shall
be provided by Presidio Pebble Creek Carlsbad & LLC, the HOA, or other mechanism to the
satisfaction of the City.
Whenever the property is sold and whenever designated individual change, immediately the
updated contact information must be provided to the City of Carlsbad.
B. Staff Training Program
Staff training and education program shall be carried out twice a year, once prior to the rainy
season (October 1s1) and once during the early dry season (April 301h).
The inspection and maintenance training program consists of the operation and function of
the biofiltration basins. Please refer to the sections VI and VI I for fact sheets and checklists.
It is the responsibility of Presidio Pebble Creek Carlsbad & LLC to convey the maintenance
and inspection information to the employees. Maintenance personnel must be qualified to
properly maintain stormwater management facilities. Inadequately trained personnel can
cause additional problems resulting in additional maintenance costs.
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C. Records
Presidio Pebble Creek Carlsbad & LLC shall retain education, inspection, and maintenance
forms and documents for at least five (5) years.
D. Safety
Keep safety considerations at the forefront of inspection procedures at all times. Likely
hazards should be anticipated and avoided. Never enter a confined space (outlet structure,
manhole, etc) without proper training or equipment. A confined space should never be
entered without at least one additional person present.
If a toxic or flammable substance is discovered, leave the immediate area and contact the
local Sheriff at 911 .
Potentially dangerous (e.g., fuel, chemicals, hazardous materials) substances found in the
areas must be referred to the local Sheriffs Office immediately for response by the Hazardous
Materials Unit. The emergency contact number is 911.
Vertical drops may be encountered in areas located within and around the facility. Avoid
walking on top of retaining walls or other structures that have a significant vertical drop. If a
vertical drop is identified within the pond that is greater than 48" in height, make the
appropriate note/comment on the maintenance inspection form.
VI. Summary of Drainage Areas and Stormwater Facilities
A. Drainage Areas
The proposed development consists of eight residential home pads, driveways, retaining
walls, brow ditches, storm drain pipes, and two (2) biofiltration basins. The proposed
improvements will disturb 3.37 acres.
The proposed drainage pattern will be similar to the existing drainage pattern with some
modifications to incorporate the Best Management Practices (BMPs) into the project design
to mimic the impacts on storm water runoff and quality. The proposed runoff from the project
site is divided into five (5) Drainage Management Areas (DMAs): (1) DMA Draining to a
Biofiltration IMP and (4) Self-Mitigating DMAs. One Point of Compliance (POC-1) has been
identified the existing Type B curb inlet on the south side of Carlsbad Village Drive, which is
the point at which the majority of the proposed site runoff will be discharge to the Carlsbad
MS4 system (see Attachment 1 for Drainage Management Area (DMA) Exhibit).
Only Basins A through D are being developed and will consider urban runoff flow rates,
durations and velocities. The developed Basin A, or DMA 1, will encompass runoff from Lots
1-6, which will be directed to the front of each lot and onto the proposed cul-de-sac. Runoff
will then travel via curb and gutter to a proposed Type-B Curb Inlet on the south side of Afton
Way. Runoff from Lots 7 and 8 will be directed to the front of each lot and onto the proposed
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cul-de-sac, then travel via curb and gutter to a proposed Type-B Curb Inlet on the north side
of Afton Way. The proposed curb inlets will connect to a proposed 18"-dia PVC storm drain
pipe adjacent to the eastern project boundary. The 18"-dia storm drain pipe will discharge
into a modified Type A6 Cleanout (per SDRSD D-09). The cleanout will include (2) orifices to
distribute flow. The size of the orifices are a function of the size of each basin divided by the
area of the two basins combined. Once flows are routed via the proposed orifices, the flows
are then conveyed via storm drain pipes to the receiving biofiltration LID IMPs called Basin 1
and Basin 2 for treatment and detention. Outflows from the basins will be conveyed via 12"-
dia storm drain pipe to the existing Type-B Curb Inlet at POC-1.
The majority of the off-site run-on from Basin B will be intercepted by a proposed brow ditch
along the southern and eastern project boundary line and directed to a proposed catch basin
on the south side of Afton Way. The catch basin will connect to a proposed 18"-dia storm
drain system which will connect to the existing 18"-dia storm drain system underneath Afton
Way and eventually Carlsbad Village Drive. The existing slopes will remain undisturbed and
will drain directly offsite, therefore being considered a Self-mitigating DMA, SM-1, per Chapter
5 Section 5.2.1 of the City of Carlsbad BMP Design Manual (BMP DM).
The off-site run-on from Basin C will be intercepted by a proposed brow ditch along the
western project boundary line and directed to a proposed catch basin near the congruent
property line of Lot 4 and Lot 5. The catch basin will outlet to a proposed 18"-dia PVC storm
drain system which will travel under the proposed cul-de-sac and connect to the existing 18"-
dia storm drain system underneath Afton Way and eventually Carlsbad Village Drive. The
existing slopes will remain undisturbed and will drain directly offsite, therefore being
considered a Self-mitigating DMA, SM-2, per the BMP DM.
The remaining runoff in Basin D is proposed to be intercepted by the existing brow ditches at
the top of cut slopes along the crib wall and directed to the existing sidewalk underdrain pipes
at various locations along Carlsbad Village Drive. The runoff will then enter the existing storm
drain system underneath Carlsbad Village Drive as historically. The existing slopes will
remain undisturbed and will drain directly offsite, therefore being considered a Self-mitigating
DMA, SM-3, per the BMP DM.
The proposed drainage facility improvements will consist of minor concrete drainage
channels, storm drain pipes, curb inlets, and two detention-biofiltration basins. The
biofiltration basins proposed for the four main Drainage Basins A - D are designed so that
increases in the drainage discharge rate and velocity will be mitigated up to the 100-year
runoff. The proposed biofiltration basins will serve to detain the very minor calculated increase
in runoff created by the proposed development, and to mitigate any concentration of storm
water discharge that might cause erosion.
B. Treatment and Flow-Control Facilities
All stormwater runoff will be treated by the biofiltration basins. Flows will discharge from the
biofiltration cells via a low flow orifice outlet within the gravel layer or a surface slot within the
riser structure. The top of the riser will act as a spillway, such that peak flows can be safely
55
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discharged to the receiving storm drain system. A perforated under-drain pipe will be located
at the bottom of the basins and will connect to the proposed storm drain system. The
proposed storm drain system will outlet at the existing Type B curb inlet on Carlsbad Village
Drive.
See the OMA Exhibit for the location of BMPs.
The biofiltration basins are designed to treat and detain runoff. Pollutants are removed as
the runoff passes through the soil layer and the underlying layer of gravel or drain rock. A
perforated underdrain pipe will convey flow to the proposed storm drain system. Infiltration of
the storm water will not be allowed, and the basins will be lined with a 30-mil HOPE
impermeable liner. There will be an overflow outlet, which will convey flows that exceed the
capacity of the basins. The basins for this Project are sized for pollutant control and
hydromodification control, based on the City of Carlsbad BMP Design Manual.
VII. Facility Documentation
Please see the following pages regarding the BMPs details and maintenance fact sheets.
VIII. Maintenance Schedule and Checklist
Fill out the Checklists in the following pages for each BMP. The Required Maintenance activities
are at the end of this section. At the discretion of the Project proponent, a qualified Stormwater
company may be hired to perform the required inspection and maintenance and provide
necessary reports.
56
Bio Retention Basin Inspection & Maintenance Checklist
I Property:
Property Owner:
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Date of Inspection: lnspector(s) Name:
Address:
Basin Location: OMA# __ Phone:
Type of Inspection 0Monthly D pre-wet season 0Atter heavy runoff
D End of wet season Oother:
( 1" or greater)
Y=Yes N=No MR=Maintenance Required NA= Not Applicable
J Vegetation & Irrigation:
§Vegetation is dead or diseased
Vegetation & Irrigation systems in good condition
Overgrown D Neat and orderly in appearance
Required Maintenance:
-1
Soil:
0Too deep or too shallow
(the distance from the top of mulch to the top of riser pipe shall be 4"}
Required Maintenance:
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Mulch:
§Missing or Patchy in Appearance
Depth of mulch layer less than 3-in
Areas of Bare earth
Sediment, Trash & Debris:
Clogs:
Structural Components:
0Accumulated sediment, trash,and debris present D Drain time exceeds 4 hours
§Soil too deep or too shallow
accumulated sediment, trash and debris
Drain time more than 5 days after rainfall
Flow to basin is impeded
inflow pipes or downspouts are cloged/damaged
damaged splash/rock blocks
Over flow pipe in damaged or cloged
Underdrain pipes cloged or damaged
Planter is cracked, leaking or falling apart
Page 2 of 3
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Inspector Signature:. _________ _ Date: _______ _
Inspector Signature: _________ _ Date: _______ _
The basin shall be drained within 5 days after each storm event, standing water
for more than 5 days will cause mosquito breeding, contact County of San Diego Vector Control
Program at (858) 694-2888.
** The Responsible Party shall retail the maintenance/inspection records for a minimum of 5 years
from the date of maintenance.The records shall be made available to the County of San Diego for
inspection upon request at any time. Page 3of 3
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~ BIORETENTION FACILITIES
These facilities remove pollutants primarily by filtering runoff slowly through aerobic, biologically
active soil. Routine maintenance is needed to ensure that flow is unobstructed, that erosion is
prevented, and that soils are held together by plant roots and are biologically active. Typical
maintenance consists of the following:
•
•
•
•
•
•
•
Inspect inlets for channels, exposure of soils, or other evidence of erosion. Clear any
obstructions and remove any accumulation of sediment. Examine rock or other material
used as a splash pad and replenish if necessary.
Inspect outlets for erosion or plugging .
Inspect side slopes for evidence of instability or erosion and correct as necessary .
Observe the surface of bioretention facility soil for uniform percolation throughout. If
portions of the bioretention facility do not drain within 24 hours after the end of a storm,
the soil should be tilled and replanted. Remove any debris or accumulations of sediment.
Confirm that check dams and flow spreaders are in place and level and that rivulets and
channelization are effectively prevented.
Examine the vegetation to ensure that it is healthy and dense enough to provide filtering
and to protect soils from erosion. Replenish mulch as necessary, remove fallen leaves and
debris, prune large shrubs or trees, and mow turf areas. When mowing, remove no more
than 1/3height of grasses. Confirm that irrigation is adequate and not excessive and that
sprays do not directly enter overflow grates. Replace dead plants and remove noxious and
invasive vegetation.
Abate any potential vectors by filling holes in the ground in and around the bioretention
facility and by insuring that there are no areas where water stands longer than 48 hours
following a storm. If mosquito larvae are present and persistent, contact the San Diego
County Vector Control Program for information and advice. Mosquito larvicides should
be applied only when absolutely necessary and then only by a licensed individual or
contractor.
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ATTACHMENT 4
City standard Single Sheet BMP (SSBMP) Exhibit
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57
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K:\Civil 30\1326\PROD\DWG\HYDRO & SWMP\1326-DMA-HMP EX_HIBIT 12-28-16.dwg, 12/29/20161:30:09 PM
LOT4
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SWMP NO. ~1~6-=26~--
PARTY RESPONSIBLE FOR MAINTENANCE:
NAME PRESIDIO PEBBLE CREEK CARLSBAD & LLC
ADDRESS 301 WEST 28TH STREET
SUITE A
CONTACT GARY ARNOLD
NATIONAL CITY. CA 91950
PHONE NO. (619) 938-0312
PLAN PREPARED BY:
NAME RONALD HOLLOWAY
COMPANY ~B~H~A~IN~C~------
ADDRESS 5115 AVENIDA ENCINAS
SUITE L
CARLSBAD. CA 92008
PHONE NO. (760\ 931-8700
BMP NOTES:
SI NATUR
CERTIFICATION-----
1. THESE BMPS ARE MANDATORY Td BE INSTALLED PER MANUFACTURER'S
RECOMMENDATIONS OR THESE PLANS.
2. NO CHANGES TO THE PROPOSED BMPS ON THIS SHEET WITHOUT PRIOR
APPROVAL FROM THE CITY ENGINEER.
3. NO SUBSTITUTIONS TO THE MATERIAL OR TYPES OR PLANTING TYPES
WITHOUT PRIOR APPROVAL FROM THE CITY ENGINEER.
4. NO OCCUPANCY WILL BE GRANTED UNTIL THE CITY INSPECTION STAFF
HAS INSPECTED THIS PROJECT FOR APPROPRIATE BMP CONSTRUCTION
AND INSTALLATION.
5. REFER TO MAINTENANCE AGREEMENT DOCUMENT.
6. SEE PROJECT SWMP FOR ADDITIONAL INFORMATION.
BMP TABLE
BMP ID# BMPTYPE SYMBOL CASQA NO. QUANTITY
HYDROMODIFICATION & TREATMENT CONTROL
(i) BIOFILTRATION + + + + TC-32 -1.llll5... SF. AREA + + + + + + + + +
CD BIOFILTRATION ........ TC-32 ---'1lli.. SF. AREA .... + + + ........
LOW IMPACT DESIGN (L.I.D.)
0-@ ROOF DRAIN TO • SD-11 BEA. LANDSCAPING
SOURCE CONTROL
®-@ STENCILS NO DUMPING SD-13 DRAINS TO OCEAN
* CHOOSE FROM THE LIST BELOW FOR COMPLETING THE FIELDS
IN THE INSPECTIONS & MAINTENANCE FRENQUENCY COLUMNS:
ANNUAL
SEMI-ANNUALLY
QUARTERLY
BIMONTHLY
MONTHLY
AS NEEDED
NONE
WEEKLY
1 TIME PER YEAR
2 TIMES PER YEAR
3 TIMES PER YEAR
4 TIMES PER YEAR
0
GRAPHIC SCALE 1"=50'
50 100 150
DRAWING NO.
't!S -q0
~95 -~-'
~~5-qA
SHEET NO.(S) INSPECTION * MAINTENANCE *
FREQUENCY FREQUENCY
4,5 QUARTERLY SEMI-ANNUALLY
4,5 QUARTERLY SEMI-ANNUALLY
4,5 ANNUALLY ANNUALLY
>------------------t--+---+----+----<lsH1EETI CITY OF CARLSBAD 1sHElE~1
ENGINEERING DEPARTMENT
'-·'t------------------------t---+---t----+----t :====-==================:
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SINGLE SHEET BMP SITE PLAN
AFTON WAY TM
1:-· 1 ' .
DATE INITIAL DATE INITIAL
REVISION DESCRIPTION OTHER APPROVAL CITY APPROVAL
RECORD COPY
I ) I 'I /, 7
tOATE 1
PROJECT NO.
CT 14-06
DRAWING NO.
DWG 495-9 & 495-9A
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ATTACHMENT 5
"Technical Memorandum: SWMM Modeling for Hydromodification Compliance of Afton
Way, City of Carlsbad, Revised June 5, 2015", prepared by Tory R. Walker Engineering.
"Technical Memorandum: Determination of Pre-and Post-Developed 100-year Peak Flow,
Afton Way, City of Carlsbad, June 17, 2015': prepared by Tory R. Walker Engineering.
58
ECHNICAL MEMORANDUM:
SWMM Modeling for
Hydromodification Compliance of:
Afton Way, Carlsbad, CA
Prepared for:
Presidio Mana Carlsbad 9, LLC
April 9, 2015 (Revised June 5, 2015)
LKER ENCINEERING
\IN WATER RESOURCES
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FROM:
DATE:
RE:
TORY R. WALKER ENGINEERING
RELIABLE SOLUTIONS IN WATER RESOURCES
TECHNICAL MEMORANDUM
Presidio Mana Carlsbad 9, LLC
Tory Walker, PE, CFM, LEED GA
April 9, 2015 (Revised June 5, 2015)
Summary of SWMM Modeling for Hydromodification Compliance for Afton Way,
Carlsbad, CA.
INTRODUCTION
This memorandum summarizes the approach used to model the Afton Way project in the City of
Carlsbad, CA, using the Environmental Protection Agency (EPA) Storm Water Management Model 5.0
(SWMM). SWMM analyses were prepared for the pre and post-developed conditions at the site in order
to determine if the proposed LID biofiltration facilities meet the Hydromodification Management Plan
(HMP) requirements from the San Diego Regional Water Quality Control Board (SDRWQCB) as
established in the Final HMP Document dated March 2011, prepared by Brown & Caldwell for the
County of San Diego Copermittees, which includes the City of Carlsbad.
SWMM Model Development
The Afton Way project proposes 8 single-family homes with associated landscaping and hardscape
improvements on the property at 2200 Afton Way in Carlsbad, CA, which currently consists of an
existing residential structure with two sheds, an access road and open space with native grasses and
eucalyptus trees on most of the site. Two SWMM simulations were prepared for this study: the first for
the pre-development and the second for the post-developed conditions. The project site drains to one
Point of Compliance (POC). For both SWMM simulations, flow duration curves were prepared to
determine if the proposed HMP facility is sufficient to meet the current HMP requirements.
The inputs required to develop SWMM simulations include rainfall, watershed characteristics, and BMP
configurations. The Oceanside Gage from the Project Clean Water website was used for this study, since
it is the most representative of the project site precipitation due to elevation and proximity to the
project site. Evaporation for the site was modeled using average monthly values from the County hourly
dataset. The site was modeled with Type B/C and Type D hydrologic soils as determined from the
"Geotechnical Investigation, Proposed Afton Way Residential Development, 2200 Afton Way Carlsbad,
CA", by Leighton and Associates, Inc. (see Attachment 8). In existing conditions, soils have been
assumed to be uncompacted for the pervious area, compacted for the impervious area of the site in the
existing conditions, and fully compacted in the post developed conditions. Other SWMM inputs for the
subareas are discussed in the attachments to this document and in Reference [1], where the selection of
the parameters is explained in detail.
WATERSHED, FLOODPLAIN et STO!iM WATER MANAGEMENT· RlVER RESTORATlON • FLOOD FACIUTIES DESIGN· SEDIMENT~ EROSION
122. CIVIC CENTER DRIVE, SUITE 2.06, VISTA CA 92084 • 760-414-92.12 • TRWENCINEERING.COM
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Presidio Mana Carlsbad 9, LLC
Afton Way HMP
HMP MODELING
DEVELOPED CONDITIONS
Storm water runoff from the proposed project site is routed to one POC, located east of the project site
near Carlsbad Village Drive. Runoff is drained to two independent onsite receiving biofiltration LID I MPs
called Basin 1 and Basin 2. The area that drains to each basin is a function of the size of each basin
divided by the area of the two basins combined (See Table 1). Once flows are routed via the proposed
LID I MPs, the flows are then conveyed via storm drain to the aforementioned POC.
TABLE 1-TRIBUTARY AREAS TO EACH BASIN
1 1,805 79% 2.83 79%
2 485 21% 0.76 21%
Total 2,290 100% 3.59 100%
(l) This area does not include the area of the biofiltration basin.
The two IMPs are responsible for handling hydromodification requirements for the project site. In
developed conditions, both Basins 1 and 2 will have a surface depth of 2.5 feet and a riser spillway
structure (see dimensions in Tables 2 and 3). Flows will discharge from the biofiltration cells via a low
flow orifice outlet within the gravel layer or a surface slot within the riser structures. The top of the riser
structures will act as a spillway, such that peak flows can be safely discharged to the receiving storm
drain system.
Beneath the invert of the basins' lowest surface discharge lies the proposed LID biofiltration portion of
the drainage facility. This portion of the basins is comprised of 12 inches of surface storage, an 18-inch
layer of amended soil (a highly sandy, organic rich composite with an infiltration capacity of at least 5
inches/hr) and a 12-inch layer of gravel for additional detention and to accommodate the French drain
system. These systems will treat storm water and convey flows to a small diameter lower outlet orifice.
Once flows have been routed by the outlet structures, flows will then discharge independently from
each basin to the receiving POC discharge location.
The biofiltration basins were modeled using the biofiltration LID module within SWMM. The
biofiltration module can model the underground gravel storage layer, underdrain with an orifice plate,
amended soil layer, and a surface storage pond up to the elevation of the invert of the lowest surface
discharge opening in the basins' riser structure. Ponding above the invert of the lowest surface
discharge opening in the riser structures is modeled as a detention basin: elevation vs area and
elevation vs discharge tables are needed by SWMM for Modified Puls routing purposes.
It should be noted that detailed outlet structure location and elevations will be shown on the
construction plans based on the recommendations of this study.
2 Job# 359-01
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Presidio Mana Carlsbad 9, LLC
Afton Way HMP
BMP MODELING FOR HMP PURPOSES
Modeling of HMP IMP
Two LID IMP biofiltration basins are proposed for hydromodification conformance for the project site.
Basin dimensions are summarized in Table 2 below.
TABLE 2 -SUMMARY OF DEVELOPED DUAL PURPOSE IMP
Basin 1 2.875 1805 12 18 12,30 1.25
Basin 2 0.773 485 12 18 12,30 1.25
Notes: (1): Area of amended soil equal to area of gravel.
(2): Gravel depth needed to comply with hydromodification conditions.
(3): Diameter of the orifice in the gravel layer with invert at bottom of layer, tied with HMP min. threshold (10%Q,).
(4): First number is the surface depth of BMP up to the slot invert. Second number is the total surface depth from the
bottom of surface pond to top of pond wall.
Table 3 provides a summary of the proposed outlet structures' dimensions (a detailed sketch of the riser
structure is provided in Attachment 5 of this memo).
TABLE 3 -SUMMARY OF BIOFILTRATION BASIN RISER DETAILS
1 3 24 12 8'@ 1.75' Elev.
2 3 24 12 8'@ 1. 75' Elev.
Notes: (1): All elevations measured from the bottom of the surface of the basin.
(2): Assumed 3' x 3' box riser with internal 2' x 2' opening (8 feet internal perimeter).
Drawdown Calculations
To ensure compliance with the 72 hour drawdown requirements per Section 6.4.6 of the Final HMP
dated March 2011, drawdown calculations are provided in Attachment 4 of this report. The calculated
drawdown times for Basin 1 and 2 are 12 hours and 3.7 hours respectively.
3 Job# 359-01
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Afton Way HMP
FLOW DURATION CURVE COMPARISON
The Flow Duration Curve (FDC) for the site was compared at the POC by exporting the hourly runoff time
series results from SWMM to a spreadsheet. The 02 and 0 10 were determined with a partial duration
statistical analysis of the runoff time series in an Excel spreadsheet using the Cunnane plotting position
method (which is the preferred plotting methodology in the HMP Permit). As the SWMM Model
includes a statistical analysis based on the Weibull Plotting Position Method, the Weibull Method was
also used within the spreadsheet to ensure that the results were similar to those obtained by the
SWMM Model.
For this project, the low threshold for the range of analysis is 10% of 0 2 • The range between 10% of Qi
and 010 was divided into 100 equal time intervals; the number of hours that each flow rate was
exceeded was counted from the hourly series. Additionally, the intermediate peaks with a return period
"i" were obtained (0; with i=3 to 9). For the purpose of the plot, the values were presented as
percentage of time exceeded for each flow rate. FDC comparison at the POC is illustrated in Figures la
and lb in both normal and logarithmic scale. Attachment 5 provides a detailed drainage exhibit for the
pre-and post-developed condition.
As can be seen in Figures la and lb, the FDC for the proposed condition with the HMP IMP is within
110% of the curve for the existing condition in both peak flows and durations for the POC. The
additional runoff volume generated from developing the site will be released to the existing point of
compliance at a flow rate below the 10% Qi lower threshold for the POC. Additionally, the project will
also not increase peak flow rates between the 0 2 and the 0 10, as shown in the graphic and also in the
peak flow tables in Attachment 1.
SUMMARY
This study has demonstrated that the proposed HMP IMPs provided for the Afton Way site are sufficient
to meet the current HMP criteria if the cross-sectional areas and volumes recommended within this
technical memorandum, and the respective low flow orifice, slots and outlet structure are incorporated
as specified within the proposed project site.
KEY ASSUMPTIONS
1. Soils Type B/C and Type Dare representative of the existing condition site.
4 Job# 359-01
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Afton Way HMP
-TRWE -
Afton Way -Flow Duration Curve
·-·-·-·-·-·-·-·-·-· \~·-·-·-·-·-
1.50
! a
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1 .00
0.75
0.50
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...
' ... ...
_snz-·-·-·-·-·-·-·-•-·-·-·-·-·-·-·-·-1-·-'~-----·-_·_-_._-_·-_·_-_.""" _________ _.
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·-·-·o:1Qz
0.00 +---------'---------.._.,.---~------'----'-------
0 .001 O.ot 0 .1
..... _... of time ........ '"'
Afton Way -Flow Duration Curve
2 .75 ..-----,----,--------,-------.----.------.---.------,---,.1-~---,
o·-·-·-·-,-·-·-·-·-·-·-·-·-·-· 1·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-•-·-·-·-·-·-·-<tio
2 .50 ·-·-·---1---·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-----·-·-·-·-·-·-·-·-·-·-Q. ·-·-·-·-,-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·---,-----·-·-·-· ·-·-·---,-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-~---·-·-·-·-· 2 .25 f"'l~---,-------;-------r--t----<-----------,--;----1,
. :=:=:=!=:=:=:=:=:=:=:=·=:=:=:=:=:-:=:=:=:=:=:=:=:=:=:=:=:=:=:=:='.=:=: 1:=:=:=:~ 2 .00
\ I Q;,------1---------·-----·-·-·-·-·-·-·----·-·-·-·-----·------·-·-·-·-·-·-·-·-·""1l.,
1.50
1.25 +---\------'h------<-------------;-----+-i --Existing
1 .00
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o.~--·-·-·- ---·--·-·-·-·-·-,-·-·-·- --·---,-·-·-·-·-·-·-·-·
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0.00 +-------~----...----~---'--,-------~---.-----;
0 0 .01 0 .02 0 .03 0 .04 0 .05 0 .06 0.07 0 .08
,en:enroc• of time •Uffded '"'
Figure la and lb. Flow Duration Curve Comparison for POC -1 (logarithmic and normal "x" scale)
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Afton Way HMP
REFERENCES
[1] -"Review and Analysis of San Diego County Hydromodification Management Plan (HMP):
Assumptions, Criteria, Methods, & Modeling Tools -Prepared for the Cities of San Marcos,
Oceanside & Vista", May 2012, TRW Engineering.
[2] -"Final Hydromodification Management Plan (HMP) prepared for the County of San Diego",
March 2011, Brown and Caldwell.
[3] -Order R9-2007-001, California Regional Water Quality Control Board San Diego Region
(SDRWQCB).
[4] -"Handbook of Hydrology", David R. Maidment, Editor in Chief. 1992, McGraw Hill.
ATTACHMENTS
1. 02 to Q10 Comparison Tables
2. FDC Plots {log and natural "x" scale) and Flow Duration Table.
3. List of the "n" largest Peaks: Pre-Development and Post-Development Conditions
4. Elevations vs. Discharge & Stage-Storage Curves to be used in SWMM
5. Post Development Maps, Project plan and section sketches
6. SWMM Input Data in Input Format (Existing and Proposed Models)
7. SWMM Screens and Explanation of Significant Variables
8. Geotechnical Report.
9. Summary files from the SWMM Model
6 Job# 359-01
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02 to 010 Comparison Tables
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ATTACHMENT 1
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Qi to Q10 Comparison Table -POC-1
Return Period Existing Condition (cfs) Mitigated Condition (cfs) Reduction, Exist -
Mitigated (cfs)
2-year 1.569 0.959 0.610
3-year 1.901 1.275 0.627
_j 4-year 2.040 1.565 0.474
5-year 2.161 1.804 0.357
J 6-year 2.201 1.890 0.311
7-year 2.292 1.961 0.331
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8-year 2.348 2.109 0.239
9-year 2.439 2.279 0.160
10-year 2.605 2.291 0.315
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ATTACHMENT 2
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FDC Plots (log and natural "x" scale) and Flow Duration Table
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ATTACHMENT 2
FLOW DURATION CURVE ANALYSIS
1) Flow duration curve shall not exceed the existing conditions by more than 10%, neither in
peak flow nor duration.
The figures on the following pages illustrate that the flow duration curve in post-development
conditions, after the proposed IMPs, is below the existing flow duration curve. The flow
duration curve table following the curves shows that if the interval 0.1002 -U10 is divided in
100 sub-intervals, then a) the post development divided by pre-development durations are
never larger than 110% (the permit allows up to 110%); and b) there are no more than 10
intervals in the range 101%-110% which would imply an excess over 10% of the length of the
curve (the permit allows less than 10% of excesses measured as 101-110%).
Consequently, the design passes the hydromodification test.
It is important to note that the flow duration curve can be expressed in the "x" axis as
percentage of time, hours per year, total number of hours, or any other similar time variable. As
those variables only differ by a multiplying constant, their plot in logarithmic scale is going to
look exactly the same, and compliance can be observed regardless of the variable selected.
However, in order to satisfy the City of Carlsbad HMP example, % of time exceeded is the
variable of choice in the flow duration curve. The selection of a logarithmic scale in lieu of the
normal scale is preferred, as differences between the pre-development and post-development
curves can be seen more clearly in the entire range of analysis. Both graphics are presented just
to prove the difference.
In terms of the "y" axis, the peak flow value is the variable of choice. As an additional analysis
performed by TRWE, not only the range of analysis is clearly depicted (10% of Ui to Q10) but
also all intermediate flows are shown (Ui, (h, O,i, Os, QG, U1, Us and Qg) in order to demonstrate
compliance at any range Ux-Ux+1, It must be pointed out that one of the limitations of both the
SWMM and SDHM models is that the intermediate analysis is not performed (to obtain Qi from
i = 2 to 10). TRWE performed the analysis using the Cunnane Plotting position Method (the
preferred method in the HMP permit) from the "n" largest independent peak flows obtained
from the continuous time series.
The largest "n" peak flows are included in this attachment, as well as the values of Qi with a
return period "i", from i=2 to 10. The Qi values are also added into the flow-duration plot.
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Afton Way -Flow Duration Curve
2 .75
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1.25 -t--------+----+---+-.1....:Jf-----!----:-----l-----"lr--t---------'----~--~-~--+--+--+~
' ' 1.00 ....,
0 .75 4--IJ~~------+-----+---+----!---+-......_--+---!f--f----'1..----------"=-------+---~-----;----+-+--
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0.00
0 0 .01 0.02 0 .03 0.04 0 .05 0 .06 0.07 0 .08
Pe rce nt age of time excee de d (%)
Flow Duration Curve Data for Afton Way, Carlsbad, CA
Q2= 1.57 cfs Fraction 10 %
Q10= 2.61 cfs
Step= 0.0247 cfs
Count= 499679 hours
57.00 years
1 0.157 310 6.20E-02 338 6.76E-02 109% Pass
2 0.182 300 6.00E-02 298 5.96E-02 99% Pass
J 3 0.206 287 5.74E-02 268 5.36E-02 93% Pass
4 0.231 274 5.48E-02 244 4.88E-02 89% Pass
5 0.256 265 5.30E-02 226 4.52E-02 85% Pass
6 0.281 257 5.14E-02 212 4.24E-02 82% Pass
7 0.305 249 4.98E-02 192 3.84E-02 77% Pass
8 0.330 237 4.74E-02 183 3.66E-02 77% Pass
9 0.355 217 4.34E-02 173 3.46E-02 80% Pass
10 0.379 195 3.90E-02 163 3.26E-02 84% Pass
11 0.404 194 3.88E-02 152 3.04E-02 78% Pass
12 0.429 189 3.78E-02 145 2.90E-02 77% Pass
13 0.454 186 3.72E-02 130 2.60E-02 70% Pass
14 0.478 180 3.60E-02 112 2.24E-02 62% Pass
15 0.503 175 3.SOE-02 101 2.02E-02 58% Pass
16 0.528 168 3.36E-02 97 1.94E-02 58% Pass
17 0.553 159 3.18E-02 90 1.80E-02 57% Pass
18 0.577 149 2.98E-02 83 1.66E-02 56% Pass
19 0.602 135 2.70E-02 79 1.58E-02 59% Pass
20 0.627 132 2.64E-02 73 1.46E-02 55% Pass
21 0.652 127 2.54E-02 70 1.40E-02 55% Pass
22 0.676 125 2.SOE-02 64 1.28E-02 51% Pass
23 0.701 116 2.32E-02 57 1.14E-02 49% Pass
24 0.726 108 2.16E-02 56 1.12E-02 52% Pass
25 0.750 104 2.08E-02 54 1.08E-02 52% Pass
26 0.775 100 2.00E-02 51 1.02E-02 51% Pass
27 0.800 97 1.94E-02 48 9.61E-03 49% Pass
28 0.825 95 1.90E-02 46 9.21E-03 48% Pass
29 0.849 92 1.84E-02 43 8.61E-03 47% Pass
30 0.874 89 1.78E-02 40 8.01E-03 45% Pass
31 0.899 85 1.70E-02 39 7.81E-03 46% Pass
32 0.924 85 1.70E-02 37 7.40E-03 44% Pass
33 0.948 83 1.66E-02 36 7.20E-03 43% Pass
34 0.973 79 1.58E-02 34 6.80E-03 43% Pass
35 0.998 79 1.58E-02 34 6.BOE-03 43% Pass
36 1.022 75 1.50E-02 33 6.60E-03 44% Pass
37 1.047 68 l.36E-02 30 6.00E-03 44% Pass
1111~!<1::
38 1.072 66 1.32E-02 29 5.80E-03 44% Pass
39 1.097 53 1.06E-02 28 5.60E-03 53% Pass
40 1.121 52 1.04E-02 28 5.60E-03 54% Pass
41 1.146 51 1.02E-02 28 5.60E-03 55% Pass
42 1.171 49 9.81E-03 27 S.40E-03 55% Pass
43 1.196 45 9.0lE-03 25 5.00E-03 56% Pass
44 1.220 45 9.0lE-03 25 5.00E-03 56% Pass
45 1.245 45 9.0lE-03 24 4.80E-03 53% Pass
46 1.270 44 8.81E-03 23 4.60E-03 52% Pass
47 1.295 44 8.81E-03 23 4.60E-03 52% Pass
48 1.319 43 8.61E-03 22 4.40E-03 51% Pass
49 1.344 42 8.41E-03 22 4.40E-03 52% Pass
so 1.369 42 8.41E-03 22 4.40E-03 52% Pass
51 1.393 42 8.41E-03 22 4.40E-03 52% Pass
52 1.418 39 7.81E-03 22 4.40E-03 56% Pass
53 1.443 37 7.40E-03 22 4.40E-03 59% Pass
_I 54 1.468 34 6.80E-03 21 4.20E-03 62% Pass
55 1.492 34 6.80E-03 20 4.00E-03 59% Pass
56 1.517 34 6.80E-03 18 3.60E-03 53% Pass
57 1.542 34 6.80E-03 18 3.60E-03 53% Pass
58 1.567 33 6.60E-03 17 3.40E-03 52% Pass
59 1.591 32 6.40E-03 16 3.20E-03 50% Pass
60 1.616 32 6.40E-03 16 3.20E-03 50% Pass
61 1.641 32 6.40E-03 16 3.20E-03 50% Pass
62 1.665 32 6.40E-03 16 3.20E-03 50% Pass
63 1.690 31 6.20E-03 16 3.20E-03 52% Pass
64 1.715 30 6.00E-03 15 3.00E-03 50% Pass
65 1.740 29 5.80E-03 14 2.80E-03 48% Pass
_J 66 1.764 28 5.60E-03 14 2.80E-03 50% Pass
67 1.789 28 5.60E-03 14 2.80E-03 50% Pass
68 1.814 26 5.20E-03 13 2.60E-03 50% Pass
69 1.839 23 4.60E-03 12 2.40E-03 52% Pass
70 1.863 23 4.60E-03 12 2.40E-03 52% Pass
71 1.888 22 4.40E-03 11 2.20E-03 50% Pass
72 1.913 22 4.40E-03 11 2.20E-03 50% Pass
73 1.938 21 4.20E-03 11 2.20E-03 52% Pass
74 1.962 21 4.20E-03 10 2.00E-03 48% Pass
75 1.987 20 4.00E-03 10 2.00E-03 50% Pass
76 2.012 20 4.00E-03 9 l.80E-03 45% Pass
77 2.036 17 3.40E-03 9 1.80E-03 53% Pass
78 2.061 17 3.40E-03 9 1.80E-03 53% Pass
79 2.086 16 3.20E-03 9 1.80E-03 56% Pass
80 2.111 15 3.00E-03 9 1.80E-03 60% Pass
81 2.135 15 3.00E-03 9 1.80E-03 60% Pass
82 2.160 14 2.80E-03 9 l.80E-03 64% Pass
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83 2.185 12 2.40E-03 9 1.80E-03 75% Pass
84 2.210 10 2.00E-03 9 1.80E-03 90% Pass
85 2.234 10 2.00E-03 9 l.80E-03 90% Pass
' 86 2.259 10 2.00E-03 8 1.60E-03 80% Pass
87 2.284 8 1.60E-03 7 1.40E-03 88% Pass
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88 2.309 8 1.60E-03 6 l.20E-03 75% Pass
' 89 2.333 7 1.40E-03 6 l.20E-03 86% Pass
_j 90 2.358 7 1.40E-03 5 1.00E-03 71% Pass
91 2.383 7 1.40E-03 5 1.00E-03 71% Pass
l 92 2.407 6 l.20E-03 5 1.00E-03 83% Pass
.J 93 2.432 6 1.20E-03 5 1.00E-03 83% Pass
94 2.457 6 1.20E-03 5 1.00E-03 83% Pass
--, 95 2.482 6 l.20E-03 5 l.OOE-03 83% Pass
_J 96 2.506 6 l.20E-03 5 l.OOE-03 83% Pass
97 2.531 6 1.20E-03 4 8.0lE-04 67% Pass
98 2.556 6 1.20E-03 4 8.0lE-04 67% Pass
__ J 99 2.581 6 1.20E-03 4 8.0lE-04 67% Pass
100 2.605 6 l.20E-03 4 8.0lE-04 67% Pass
Peak Flows calculated with Cunnane Plotting Position
'-·-1
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' 10 2.605 2.291 0.315
._J 9 2.439 2.279 0.160
8 2.348 2.109 0.239
-1
7 2.292 1.961 0.331
J 6 2.201 1.890 0.311
5 2.161 1.804 0.357
4 2.040 1.565 0.474
3 1.901 1.275 0.627
-1 2 1.569 0.959 0.610
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ATTACHMENT 3
List of the "n" largest Peaks: Pre-Development
and Post-Development Conditions
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ATTACHMENT 3
List of the "n" Largest Peaks: Pre & Post-Developed Conditions
Basic Probabilistic Equation:
R = 1/P R: Return period (years).
P: Probability of a flow to be equaled or exceeded any given year (dimensionless).
Cunnane Equation:
p = i-0.4
n+0.2
Weibull Equation:
i P=-n+1
i: Position of the peak whose probability is desired (sorted from large to small)
n: number of years analyzed.
Explanation of Variables for the Tables in this Attachment
Peak: Refers to the peak flow at the date given, taken from the continuous simulation hourly
results of then year analyzed.
Position: If all peaks are sorted from large to small, the position of the peak in a sorting analysis
is included under the variable position.
Date: Date of the occurrence of the peak at the outlet from the continuous simulation
Note: all peaks are not annual maxima; instead they are defined as event maxima, with a threshold to
separate peaks of at least 12 hours. In other words, any peak P in a time series is defined as a value
where dP/dt = 0, and the peak is the largest value in 25 hours (12 hours before the hour of occurrence
and 12 hours after the occurrence, so it is in essence a daily peak).
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List of Peak events and Determination of Q2 and Q10 (Pre-Development)
Afton Way, Carlsbad, CA
T Cunnane Weibull Period of Return
(Year) (cfs) (cfs) Peaks (cfs) (Years)
10 2.61 2.73 Date Posit Weibull Cunnane
9 2.44 2.52 1.046 11/24/1983 57 1.02 1.01
8 2.35 2.37 1.066 12/10/1965 56 1.04 1.03
7 2.29 2.31 1.073 3/8/1968 55 1.05 1.05
6 2.20 2.22 1.079 3/15/1952 54 1.07 1.07
5 2.16 2.17 1.08 2/23/2005 53 1.09 1.09
4 2.04 2.05 1.084 2/13/1992 52 1.12 1.11
3 1.90 1.91 1.086 9/18/1963 51 1.14 1.13
2 1.57 1.57 1.086 1/11/2005 so 1.16 1.15
1.088 2/18/1980 49 1.18 1.18
1.09 1/15/1978 48 1.21 1.20
Note: 1.091 12/24/1988 47 1.23 1.23
Cunnane is the preferred 1.092 2/4/1994 46 1.26 1.25
method by the HMP permit. 1.122 8/17/1977 45 1.29 1.28
1.15 2/6/1969 44 1.32 1.31
1.163 3/1/1991 43 1.35 1.34
1.178 2/22/1998 42 1.38 1.38
1.178 2/12/2003 41 1.41 1.41
1.179 12/2/1961 40 1.45 1.44
1.18 11/8/2002 39 1.49 1.48
1.251 3/2/1980 38 1.53 1.52
1.312 3/11/1995 37 1.57 1.56
1.336 2/14/1998 36 1.61 1.61
1.422 2/12/1992 35 1.66 1.65
1.422 1/18/1993 34 1.71 1.70
1.449 2/15/1986 33 1.76 1.75
1.457 1/29/1980 32 1.81 1.81
1.464 1/16/1978 31 1.87 1.87
1.565 2/17/1998 30 1.93 1.93
1.569 12/30/1991 29 2.00 2.00
1.679 2/23/1998 28 2.07 2.07
1.724 2/16/1980 27 2.15 2.15
1.756 11/22/1965 26 2.23 2.23
1.809 10/20/2004 25 2.32 2.33
1.811 1/29/1983 24 2.42 2.42
1.814 2/27/1983 23 2.52 2.53
1.828 2/3/1998 22 2.64 2.65
' 1.829 2/10/1978 21 2.76 2.78
1.872 10/27/2004 20 2.90 2.92
1.928 3/17/1982 19 3.05 3.08
1.971 1/16/1952 18 3.22 3.25
2.012 11/15/1952 17 3.41 3.45
2.019 12/19/1970 16 3.63 3.67
2.027 10/29/2000 15 3.87 3.92
2.071 3/1/1978 14 4.14 4.21
2.1 4/1/1958 13 4.46 4.54
2.157 1/14/1993 12 4.83 4.93
2.185 2/18/2005 11 5.27 5.40
2.197 2/20/1980 10 5.80 5.96
2.271 2/4/1958 9 6.44 6.65
2.323 9/23/1986 8 7.25 7.53
2.383 2/25/1969 7 8.29 8.67
2.641 2/25/2003 6 9.67 10.21
3.162 1/4/1995 5 11.60 12.43
3.29 1/15/1979 4 14.50 15.89
3.624 1/4/1978 3 19.33 22.00
3.636 10/1/1983 2 29.00 35.75
4.021 4/14/2003 1 58.00 95.33
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List of Peak events and Determination of Q2 and QlO (Post-Development)
Afton Way, Carlsbad, CA
T Cunnane Weibull Period of Return
(Year) (cfs) (cfs) Peaks {cfs) {Years)
10 2.29 2.33 Date Posit Weibull Cunnane
9 2.28 2.28 0.543 2/6/1969 57 1.02 1.01
8 2.11 2.20 0.554 1/29/1957 56 1.04 1.03
7 1.96 1.98 0.57 12/24/1971 55 1.05 1.05
6 1.89 1.90 0.586 1/13/1997 54 1.07 1.07
5 1.80 1.81 0.615 2/17/1998 53 1.09 1.09
4 1.57 1.60 0.615 2/26/2004 52 1.12 1.11
3 1.27 1.28 0.62 2/18/1980 51 1.14 1.13
2 0.96 0.96 0.624 9/23/1986 50 1.16 1.15
0.652 3/1/1991 49 1.18 1.18
0.666 11/22/1996 48 1.21 1.20
Note: 0.666 10/29/2000 47 1.23 1.23
Cunnane is the preferred 0.669 4/1/1958 46 1.26 1.25
method by the HMP permit. 0.693 1/25/1969 45 1.29 1.28
0.727 11/16/1965 44 1.32 1.31
0.737 1/14/1993 43 1.35 1.34
0.768 2/13/1992 42 1.38 1.38
0.771 9/18/1963 41 1.41 1.41
0.772 1/15/1993 40 1.45 1.44
0.778 3/11/1995 39 1.49 1.48
0.798 1/20/1962 38 1.53 1.52
0.82 10/20/2004 37 1.57 1.56
0.827 3/5/1995 36 1.61 1.61
0.833 3/1/1983 35 1.66 1.65
0.84 11/15/1952 34 1.71 1.70
0.867 1/13/1957 33 1.76 1.75
0.875 2/23/2005 32 1.81 1.81
0.92 1/12/1960 31 1.87 1.87
0.921 1/16/1993 30 1.93 1.93
0.959 12/5/1966 29 2.00 2.00
0.964 2/18/2005 28 2.07 2.07
1.004 1/15/1978 27 2.15 2.15
1.025 3/8/1968 26 2.23 2.23
1.03 1/9/2005 25 2.32 2.33
1.062 1/6/1979 24 2.42 2.42
1.18 8/17/1977 23 2.52 2.53
1.185 2/15/1986 22 2.64 2.65
1.234 12/19/1970 21 2.76 2.78
1.248 2/3/1998 20 2.90 2.92
1.299 12/30/1991 19 3.05 3.08
1.462 2/23/1998 18 3.22 3.25
1.474 1/29/1980 17 3.41 3.45
1.506 10/27/2004 16 3.63 3.67
1.51 1/16/1978 15 3.87 3.92
1.703 3/17/1982 14 4.14 4.21
1.733 1/16/1952 13 4.46 4.54
1.8 11/22/1965 12 4.83 4.93
1.826 2/10/1978 11 5.27 5.40
1.887 2/20/1980 10 5.80 5.96
1.941 3/1/1978 9 6.44 6.65
1.991 2/4/1958 8 7.25 7.53
2.275 2/25/1969 7 8.29 8.67
2.293 1/4/1978 6 9.67 10.21
2.521 2/25/2003 5 11.60 12.43
2.947 1/15/1979 4 14.50 15.89
2.949 10/1/1983 3 19.33 22.00
3.303 1/4/1995 2 29.00 35.75
4.161 4/14/2003 1 58.00 95.33
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ATTACHMENT 4
Elevation vs. Area Curves and Elevation vs. Discharge Curves
to be used in SWMM
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ATTACHMENT 4
AREA VS ELEVATION
The area vs elevation curve in the SWMM model is calculated in Excel and imported into the
model. The summary of elevations has been provided on the following page.
The LID depth beneath the weir (w/ slots or orifices) is accounted for in the LID module as
illustrated in Attachment 7.
DISCHARGE VS ELEVATION
The orifices have been selected to maximize their size while still restricting flows to conform to
the required 10% of the Q2 event flow as mandated in the Final Hydromodification
Management Plan by Brown & Caldwell, dated March 2011. While TRWE acknowledges that
these orifices are small, to increase the size of these outlets would impact the basin's ability to
restrict flows beneath the HMP thresholds, thus preventing the IMP from conformance with
HMP requirements.
In order to reduce the risk of blockage of the orifices, regular maintenance of the riser and
orifices must be performed to ensure potential blockages are minimized. A detail of the orifice
and riser structure is provided in Attachment 5 of this memorandum.
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DISCHARGE EQUATIONS
1) Weir:
Qw = Cw . L . H3f2 (1)
2) Slot:
As an orifice: Q5 = B5 • h5 • Cg · j2g ( H -~s) (2.a)
As a weir: Qs = Cw , Bs . H3f2 (2.b)
For H > hs slot works as weir until orifice equation provides a smaller discharge. The elevation such that
equation (2.a) = equation (2.b) is the elevation at which the behavior changes from weir to orifice .
3) Vertical Orifices
As an orifice: Q0 = 0.25 · n:D 2 ·Cg· j2g ( H -;) (3.a)
As a weir: Critical depth and geometric family of circular sector must be solved to determined Q as a function of
H:
Q'fi A~r Acr I D 2
-= -; H = Yer +-2 . T ; Tcr = 2-vYcrCD -Yer); Acr = -8 [acr -sin(acr)];
g Tcr er
Yer = ~ [1 -sin(0.5 · acr)] (3.b.1, 3.b.2, 3.b.3, 3.b.4 and 3.b.5)
There is a value of H (approximately H = 110% D) from which orifices no longer work as weirs as critical depth is
not possible at the entrance of the orifice. This value of H is obtained equaling the discharge using critical
equations and equations (3.b).
A mathematical model is prepared with the previous equations depending on the type of discharge.
The following are the variables used above:
Ow, Os, Oo = Discharge of weir, slot or orifice (cfs)
Cw, Cg: Coefficients of discharge of weir (typically 3.1) and orifice (0.61 to 0.62)
L, Bs, D, h5 : Length of weir, width of slot, diameter of orifice and height of slot, respectively; (ft)
H: Level of water in the pond over the invert of slot, weir or orifice (ft)
Am Tw Ym acr: Critical variables for circular sector: area (ft2), top width (ft), critical depth (ft), and angle to the center,
respectively.
1 Stage-Area for Basin 1
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Elevation (ft) Area (ft 2
) Volume (ft3)
0.00 1805 0
0.08 1809 151
0.17 1815 302
0.25 1822 453
0.33 1828 605
0.42 1834 758
0.50 1840 911
0.58 1847 1065
0.67 1853 1219
0.75 1860 1373
0.83 1866 1529
0.92 1873 1684
1.17 1893 2155
1.25 1899 2313
1.33 1906 2472
1.42 1913 2631
1.50 1920 2790
1.58 1926 2951
1.67 1933 3112
1.75 1940 3273
1.83 194 7 3435
1.92 1954 3598
2.00 1961 3761
2.08 1969 3924
2.17 1976 4089
2.25 1983 4254
2.33 1990 4419
2.42 1997 4585
2.50 2005 4752
SUB SURFACE STORAGE BASIN BR-80
Elevation (ft)
-1.50
-2.50
Gravel & Amended Soil TOTAL =
Surface Total TOTAL =
IMP TOTAL=
Volume (ft3
)
812.3 Amended Soil Base (0.3 voids)
1---1-2_2_.o _ ____,,,,,, 4:fftiliJl1PJ!lllllifR~~;~
1534.3 (ft3
)
4752.1 (ft3
)
6286.4 (ft3
)
(1): The area at any surface elevation corresponds to the area of gravel and amended soil (Bio-retention layer)
~1 (2): Volume at this elevation coresponds with surface volume for WQ purposes (invert of lowest surface outlet)
IEffective Depth: 12.24 in
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1 Stage-Area for Basin 2
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Elevation (ft) Area (ft2
) Volume (ft3)
0.00 485 0
0.08 495 41
0.17 504 82
0.25 513 125
0.33 522 168
0.42 532 212
0.50 541 257
0.58 551 302
0.67 560 348
0.75 569 395
0.83 579 443
0.92 589 492
1.17 617 643
1.25 627 694
1.33 637 747
1.42 647 801
1.50 657 855
1.58 666 910
1.67 676 966
1.75 686 1023
1.83 696 1080
1.92 706 1139
2.00 716 1198
2.08 727 1258
2.17 737 1319
2.25 747 1381
2.33 757 1444
2.42 767 1507
2.50 778 1572
SUB SURFACE STORAGE BASIN BR-80
Elevation (ft) Volume (ft3)
-1.50 218.3 Amended Soil Base (0.3 voids)
__ 1_9_4-.o--'~Ii~Bll!l!llllltit~~r~~:: -2.50
Gravel & Amended Soil TOTAL =
Surface Total TOTAL =
IMP TOTAL=
412.3 (ft3)
1571.7 (ft3)
1983.9 (ft3
}
(1): The area at any surface elevation corresponds to the area of gravel and amended soil (Bio-retention layer)
(2): Volume at this elevation coresponds with surface volume for WQ purposes (invert of lowest surface outlet)
IEffective Depth: 13.38 in
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Outlet structure for Discharge of Biofiltration 1 and 2
Discharge vs Elevation Table
Low orifice: 1.000" Lower slot
Number: 0 Invert: 0.00 ft
Cg-low: 0.62 B 2.00 ft
Middle orifice: 1" h,10,: 0.250 ft
number of orif: 0 Upper slot
Cg-middle: 0.62 Invert: 0.00 ft
invert elev: 0.000 ft B: 0.00 ft
h,10,: 0.000 ft
*Note: All elevations measure 1 feet above the ammended soil.
h H/D-low H/D-mid Qlow-orif QI ow-weir Qtot-low
(ft) --(els) (els) (cfs)
0.000 0.000 0.000 0.000 0.000 0.000
0.042 0.500 0.500 0.000 0.000 0.000
0.083 1.000 1.000 0.000 0.000 0.000
0.125 1.500 1.500 0.000 0.000 0.000
0.167 2.000 2.000 0.000 0.000 0.000
0.208 2.500 2.500 0.000 0.000 0.000
0.250 3.000 3.000 0.000 0.000 0.000
0.292 3.500 3.500 0.000 0.000 0.000
0.333 4.000 4.000 0.000 0.000 0.000
0.375 4.500 4.500 0.000 0.000 0.000
0.417 5.000 5.000 0.000 0.000 0.000
0.458 5.500 5.500 0.000 0.000 0.000
0.500 6.000 6.000 0.000 0.000 0.000
0.542 6.500 6.500 0.000 0.000 0.000
0.583 7.000 7.000 0.000 0.000 0.000
0.625 7.500 7.500 0.000 0.000 0.000
0.667 8.000 8.000 0.000 0.000 0.000
0.708 8.500 8.500 0.000 0.000 0.000
0.750 9.000 9.000 0.000 0.000 0.000
0.792 9.500 9.500 0.000 0.000 0.000
0.833 10.000 10.000 0.000 0.000 0.000
0.875 10.500 10.500 0.000 0.000 0.000
0.917 11.000 11.000 0.000 0.000 0.000
0.958 11.500 11.500 0.000 0.000 0.000
1.000 12.000 12.000 0.000 0.000 0.000
1.042 12.500 12.500 0.000 0.000 0.000
1.083 13.000 13.000 0.000 0.000 0.000
1.125 13.500 13.500 0.000 0.000 0.000
1.167 14.000 14.000 0.000 0.000 0.000
1.208 14.500 14.500 0.000 0.000 0.000
1.250 15.000 15.000 0.000 0.000 0.000
1.292 15.500 15.500 0.000 0.000 0.000
1.333 16.000 16.000 0.000 0.000 0.000
1.375 16.500 16.500 0.000 0.000 0.000
1.417 17.000 17.000 0.000 0.000 0.000
1.458 17.500 17.500 0.000 0.000 0.000
1.500 18.000 18.000 0.000 0.000 0.000
Emergency weir:
Invert: 0.75 ft
B: 8.00 ft
Qmid-orif Qmid-weir Qtot-med Qslot Qslot-upp Qemerg Qtot
(els) (els) (cfs) (cfs) (cfs) (cfs) (cfs)
0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.000 0.000 0.000 0.053 0.000 0.000 0.053
0.000 0.000 0.000 0.149 0.000 0.000 0.149
0.000 0.000 0.000 0.274 0.000 0.000 0.274
0.000 0.000 0.000 0.422 0.000 0.000 0.422
0.000 0.000 0.000 0.590 0.000 0.000 0.590
0.000 0.000 0.000 0.775 0.000 0.000 0.775
0.000 0.000 0.000 0.977 0.000 0.000 0.977
0.000 0.000 0.000 1.117 0.000 0.000 1.117
0.000 0.000 0.000 1.224 0.000 0.000 1.224
0.000 0.000 0.000 1.322 0.000 0.000 1.322
0.000 0.000 0.000 1.413 0.000 0.000 1.413
0.000 0.000 0.000 1.499 0.000 0.000 1.499
0.000 0.000 0.000 1.580 0.000 0.000 1.580
0.000 0.000 0.000 1.657 0.000 0.000 1.657
0.000 0.000 0.000 1.731 0.000 0.000 1.731
0.000 0.000 0.000 1.801 0.000 0.000 1.801
0.000 0.000 0.000 1.869 0.000 0.000 1.869
0.000 0.000 0.000 1.935 0.000 0.000 1.935
0.000 0.000 0.000 1.998 0.000 0.211 2.209
0.000 0.000 0.000 2.060 0.000 0.597 2.657
0.000 0.000 0.000 2.120 0.000 1.096 3.216
0.000 0.000 0.000 2.178 0.000 1.687 3.865
0.000 0.000 0.000 2.234 0.000 2.358 4.593
0.000 0.000 0.000 2.290 0.000 3.100 5.390
0.000 0.000 0.000 2.343 0.000 3.906 6.250
0.000 0.000 0.000 2.396 0.000 4.773 7.169
0.000 0.000 0.000 2.448 0.000 5.695 8.143
0.000 0.000 0.000 2.498 0.000 6.670 9.168
0.000 0.000 0.000 2.548 0.000 7.695 10.243
0.000 0.000 0.000 2.596 0.000 8.768 11.364
0.000 0.000 0.000 2.644 0.000 9.887 12.530
0.000 0.000 0.000 2.691 0.000 11.049 13.740
0.000 0.000 0.000 2.737 0.000 12.254 14.990
0.000 0.000 0.000 2.782 0.000 13.499 16.281
0.000 0.000 0.000 2.826 0.000 14.785 17.611
0.000 0.000 0.000 2.870 0.000 16.108 18.978
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TORY R. WALKER ENGINEERING Project Name ...... .
Project No ............ .
Afton Way
359-01
6/5/2015 REUAIH.E SOLUTlONS IN WATER RESOURCES Date ...................... .
Drawdown Calculation for IMP 1
Total Drawdown Time: 12.0 hours
Underdrain Orifice Diameter:
C:
Amended Soil Depth:
Gravel Depth:
Surface Depth (ft) Volume (cf) <lorifice ( cfs)
1.75 3273 0.085
1.67 3112 0.085
1.58 2951 0.084
1.50 2790 0.083
1.42 2631 0.082
1.33 2472 0.081
1.25 2313 0.080
1.17 2155 0.079
1.08 1998 0.078
1.00 1841 0.077
0.92 1684 0.077
0.83 1529 0.076
0.75 1373 0.075
0.67 1219 0.074
0.58 1065 0.073
0.50 911 0.072
0.42 758 0.071
0.33 605 0.070
0.25 453 0.069
0.17 302 0.067
0.08 151 0.066
0.00 0 0.065
Note: Drawdown time is calculated assuming an initial water
surface depth equal to the invert ofthe riser structure.
aT (hr) Total Time (hr)
0.000 0.0
0.527 0.5
0.531 1.1
0.534 1.6
0.538 2.1
0.542 2.7
0.546 3.2
0.550 3.8
0.555 4.3
0.559 4.9
0.564 5.4
0.569 6.0
0.574 6.6
0.580 7.2
0.586 7.8
0.592 8.3
0.598 8.9
0.605 9.5
0.612 10.2
0.619 10.8
0.627 11.4
0.636 12.0
_I
Surface Depth (ft) Volume(cf) Q.,,ifice ( cfs) AT(hr) Total Time (hr)
_i
TORY R. WALKER ENGINEERING
RELIABLE SOLUTIONS IN WATER RESOURCES
Project Name ...... .
Project No ............ .
Date ...................... .
Afton Way
359-01
6/5/2015
1 Drawdown Calculation for IMP 1
Total Drawdown Time: 3.7 hours
l
.J Underdrain Orifice Diameter:·•· ix YT l'.2'5 in
C:
Amended Soil Depth:
Gravel Depth:
Surface Depth (ft) Volume (cf) Clorifice ( cfs)
1.75 1023 0.085
1.67 966 0.085
1.58 910 0.084
1.50 855 0.083
1.42 801 0.082
1.33 747 0.081
1.25 694 0.080
~l 1.17 643 0.079
1.08 592 0.078
1.00 541 0.077
0.92 492 0.077
0.83 443 0.076
0.75 395 0.075
0.67 348 0.074
0.58 302 0.073
0.50 257 0.072
0.42 212 0.071
0.33 168 0.070
0.25 125 0.069
0.17 82 0.067
0.08 41 0.066
0.00 0 0.065
. l
, __ j
~.I
Note: Drawdown time is calculated assuming an initial water
surface depth equal to the invert of the riser structure.
AT (hr) Total Time (hr)
0.000 0.0
0.185 0.2
0.185 0.4
0.184 0.6
0.183 0.7
0.182 0.9
0.181 1.1
0.181 1.3
0.180 1.5
0.179 1.6
0.178 1.8
0.178 2.0
0.177 2.2
0.176 2.3
0.176 2.5
0.175 2.7
0.175 2.9
0.174 3.0
0.174 3.2
0.173 3.4
0.173 3.6
0.172 3.7
·1
-~)
• . .I
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j
ATTACHMENT 5
Vicinity Map, Pre & Post-Developed OMA Maps,
Project Plan and Detention Section Sketches
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EXISTING CONDITION HYDROLOGY MAP
AFTON WAY SUBDIVISION, CARLSBAD, CA
j
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WEIGHTED RUNOFF COEFFICIENT VALUE TABLE:
Existing Hydrology-Afton Way
Up Node Down Node Total Acreage C1 Al (acres) c, A2 (acres) c, A3 (acres) Ceo mp
3 1 1.60 0.25 0.48 0.35 0.95 0.87 0.14 0.36
6 4 2.61 0.25 2.61 0.35 0.00 0.87 0.00 0.25
8 7.1 0.37 0.25 0.36 0.35 0.00 0.87 0.01 0.26
7.1 7 0.10 0.25 0.06 0.35 0.00 0.87 0.04 0.50
15 13 0.64 0.25 0.64 0.35 0.00 0.87 0.00 0.25
13 12 0.31 0.25 0.12 0.35 0.00 0.87 0.19 0.63
12 11 0.62 0.25 0.45 0.35 0.00 0.87 0.17 0.42
11 10 0.42 0.25 0.00 0.35 0.07 0.87 0.35 0.73
10 1.1 0.36 0.25 0.00 0.35 0.19 0.87 0.17 0.41
19 18 1.14 0.25 0.00 0.35 0.13 0.87 1.01 0.77
Note: (-values taken from Table 3-1 of San Diego County Hydrology Manual, consistent with on-
site existing soil types. See References.
LEGEND:
SURFACE NODE
SURFACE RUNOFF
BASIN AREA (ACRES)~
BASIN LIMIT
SUB-BASIN LIMIT
FLOWPATH
------
PROJECT BOUNDARY
100· 150'
SCALE: 1" = 50'
EXISTING CONDITION
HYDROLOGY MAP
AFTON WAY SUBDIVISION
CARLSBAD, CA
b~A,lnc.
land planning, civil engineering, suiveylng
5115 AVENIDA ENCINAS
SUITE "L"
CARLSBAD, CA. 92008-4387
(760) 931-8700
DMA DRAINAGE AND
SURFACE TYPE CALCULATIONS:
Rain Low Flow
Soil Type Slope Class Gauge Threshold
B Flat/Moderate Oceanside 0.1Q2
D Flat/Moderate Oceanside 0.1Q2
Post~
DMA OMA OMA Area/sq Project
Name Descri tion t su ace
3,500 roof
Latl 1,050 dwy
7,602 Jandsape
3,500 roof
Lot 2 500 dwy
9,040 Jandsape
3,500 roof
Lot3 4,500 dwy
12,273 Jandsape
3,500 roof
Lot4 1,724 dwy
DMA-1 10,945 landsape
3,500 raaf
Lot 5 1,850 dwy
7,797 londsape
3,500 roof
Lot6 2,320 dwy
11,121 landsape
3,500 roof
Lot 7 2,700 dwy
20,018 landsape
3,500 roof
Lat8 500 dwy
21,480 landsape
Street & 11,148 pavement DMA-2
4,323 landsape Landsca e
Total 158,891
Self Treatina Areas -
DMAName Area (sqft)
OMA-6A 47,087
DMA-68 12,458
OMA-SA 11,614
DMA-58 8,686
DMA-7A 5,819
DMA-78 10,225
Bioretention Basins usina SWMM Madelina
IMP Sizing Volume,
Factor, A 1 Vl
0.035 N/A
DMA
Runoff DMAArea
5/o e Factor xruno
Flat 1.0 3,500
Flat 1.0 1,050
Moderate 0.1 760
Flat 1.0 31500
Flat 1.0 500
Mod.erate 0.1 904
Flot 1.0 3,500
Flat 1.0 4,500
Moderate 0.1 1,227
Flat 1.0 3,500
Flat 1.0 1,724
Moderate 0.1 1,095
Flat 1.0 3,500
Flat 1.0 1,850
Moderate 0.1 780
Flat 1.0 3,500
Flat 1.0 2,320
Moderate 0.1 1,112
Flat 1.0 3,500
Flat 1.0 2,700
Moderate 0.1 2,002
Flat 1.0 3,500
Flot 1.0 500
Moderate 0.1 2,148
Flat 1.0 11,148
Flat 0.1 432
Total !me Area 54,292
Total Ldse Area 10,460
Total 64,752
.,1 .
Subsurface
Volume, Vl
N/A
Pro osed /MPs
IMP Sizing
Factor, A 1
0.035
0.035
0.035
·'/ / /•
' I / ''
' ' //', i /
. ' /;
Min Area
1,900
366
2,266
-----~ '-·//;-...
,. ,
_;-,
/ F
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Proposed
Area
2;2ss
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K:\Civil 3D\1326\PROD\EXHIB!TS\HYDRO & SWMP\1-2015\1326-SWMP rev 2.dwg, 4/7/2015 4:58:06 PM
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Proposed Proposed
Basin 1 Basin 2
Proposed Proposed
Basin 1 Basin 2
1,805 485 t
.. I,
·, )
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0
i t,. ·.,:['-: ..
.
----------·-· -------··---------------
~" DRAINAGE MANAGEMENT AREA MAP
AFTON WAY SUBDIVISION, CARLSBAD, CA
--~··' . .. -. ·.. \ I .
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TW 220'
DEEP ROOTED, DENSE,
DROUGHT TOLERANT
PLAN TING SUI TABLE FDR WELL
DRAINED SOIL
TW 215'
214.5' SPILLWAY
209.5'
~ EXIST. GROUND
CATCH BASIN TYPE G
WITH GRATED INLET
210'
24" 'f·\ t---[-;~~-;:.:~2::_·~5t--;r-SLOT ORIFICE TO ALLOW
100 YR
PREDEVELOPMENT FLOW
12" PVC
OUTLET PIPE
RESTRICTOR PLATE TO LIMIT
FLOW FROM V2 STORAGE
AREA, 1.0" DRAIN DOWN HOLE
• I_ \ •• ' PLACE PIPE WITH
PERFORATIONS AT THE
INVERT
BIORETENTION BASIN 1 DETAIL
NOT TO SCALE
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---
25' o' 50' 1 oo' 150'
111111111111111111111111 liiiiiiiiiiiiliiiiiiiiiiii I"""""""~
SCALE: 1'' = 50'
L~GEND:
'----'--....,) BIO-RETENTION BASIN
DMA LIMIT
0
OMA-/
PROPERTY LINE
DMA REFERENCE NUMBER,
SEE "AFTON WAY DMA
DRAINAGE AND SURFACE
TYPE CALCULATIONS"
IN HYDROLOGY AND SWMP
REPORT FOR THIS PROJECT
DMA ID
FLOWLINES
=== CONCRETE BROW DITCH
DRAINAGE MANAGEMENT
AREA MAP
AFTON WAY SUBDIVISION
CARLSBAD, CA
b~A,lnc.
land planning, civil englneerjng, surveying
5115 AVENIDA ENCINAS
SUITE "L"
CARLSBAD, CA. 92008-4387
(760) 931-8700
L '~-
3"H X 24"W SLOT
{SLOT WIDTH CAN BE DISTRIBUTED
ON TWO SIDES TO TOTAL 24 ")
EXIST. GROUND
'~
RISER OUTLET STRUCTURE
18" AMENDED SOIL
MIN. INFIL TRA T/ON
RATE 5"/HR.
~
BASIN TOP ELEV {2.50')
RISER TOP ELEV (1. 75 ')
BASIN INVERT {0.00')
'--r--BOTTOM OF AMENDED SOIL {-1.50')
LID INVERT-BOTTOM OF GRAVEL {-2.50')
1.25-INCH LID ORIFICE {UNDERDRAIN ORIFICE)
BIORETEN T/ON AREA
BIORETENTION AREA CROSS SECTION
NOT TO SCALE
IMP H{FT) Hmax {FT) Hg {FT) LID Orifice {IN) Ag (Fr) Abot {Fr) Atop {Fr)
1 1.00 2.50 1.00 1.25 1805 1805 2005
2 1.00 2.50 1.00 1.25 485 485 778
J -~-
RISER BOX WALL------
<J
RESTR/CTOR PLATE
FRENCH DRAIN __/
D
~LID ORIFICE
<J LJ . Ll ·4
GRAVEL STORAGE LA YER . LJ
D = 4"
ORIFICE DETAIL
NOT TO SCALE
SLOT
INVERT ELEV
~-
I-B • I
I· Bs ·lj_ H
Hs
T
I · B tot = BOX DIMENSION • I
OUTLET STRUCTURE DETAIL -SECTION (TYP)
NOT TO SCALE
SLOT
OUTLET
Bs (FT) Hs (FT) ELEV (FT) L (FT)
1 2.00 0.25 1.00 8.00
2 2.00 0.25 1.00 8.00
NOT£· L = TOTAL LENGTH OF WEIR {FT). AS RISER IS SQUARE, L=B FT
8s: THIS WIDTH OF THE SLOT CAN BE DISTRIBUTE ON TWO SIDES.
WEIR
H (FT)
1.75
1.75
- J
_J
I
' J
_ j
ATTACHMENT 6
SWMM Input Data in Input Format
(Existing & Proposed Models)
' _J
- J
[TITLE]
[OPTIONS]
FLOW UNITS
INFILTRATION
FLOW ROUTING
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
ALLOW PONDING
INERTIAL DAMPING
VARIABLE STEP
LENGTHENING STEP
MIN SURFAREA
NORMAL FLOW LIMITED
SKIP STEADY STATE - -FORCE_MAIN_EQUATION
LINK OFFSETS
MIN SLOPE
[EVAPORATION]
CFS
GREEN AMPT
KINWAVE
10/17/1948
00:00:00
10/17/1948
00:00:00
10/17/2005
23:00:00
01/01
12/31
0
01:00:00
00:15:00
04:00:00
0:01:00
NO
PARTIAL
0.75
0
0
BOTH
NO
H-W
DEPTH
0
;;Type Parameters
.. ----------''
PRE-DEVELOPMENT
MONTHLY 0.041 0.076 0.118 0.192 0.237 0.318 0.308 0.286 0.217 0.14
DRY ONLY NO
[RAINGAGES]
'' Rain Time Snow Data
; ;Name Type Intrvl Catch Source
. ·---------------------------------'' OCEANSIDE INTENSITY 1:00 1. 0 TIMESERIES OCEANSIDE
[SUBCATCHMENTS]
;; Total Pent. Pent.
; ;Name Raingage Outlet Area Imperv Width Slope
0.067 0.041
Curb Snow
Length Pack
··------------------------------------------------------'' Compacted
Uncompacted
[SUBAREAS]
;;Subcatchment
. ·--------------
Compacted
Uncompacted
[INFILTRATION]
;;Subcatchment
··--------------'' Compacted
Un compacted
[LID CONTROLS] -
'' ··--------------'' LID Al
LID Al
LID Al
LID Al
LID Al
[LID _USAGE]
OCEANSIDE
OCEANSIDE
N-Imperv
----------
.012
.012
Suction
----------
6.3
6.3
Type/Layer
----------
BC
SURFACE
SOIL
STORAGE
DRAIN
POC 0.19 0 22 12 0
POC 3.45764 0 402 12 0
N-Perv S-Imperv S-Perv Pct Zero RouteTo PctRouted
---------- ---------- ---------- ----------
--------------------
.05 .02 0.1 25 OUTLET
.05 .02 0.1 25 OUTLET
HydCon IMDmax
--------------------
.075 0.31
.10 0.31
Parameters
----------
16 0 0 0.1 5
24 0.4 0.2 0.1 5 5 1. 5
18 0.67 0.01875 0
0.1999 0.5 0 6
1
PRE-DEVELOPMENT
__ J ;;Subcatchment LID Process Number Area Width InitSatur Fromimprv ToPerv Report File
··--------------------------------------------------------- ---------- -------------------------------
_J
_ _J
''
[OUTFALLS]
; ;Name
,,--------------
POC
[TIMESERIES]
Invert
Elev.
Outfall
Type
0 FREE
Stage/Table
Time Series
;;Name Date Time Value
··--------------------------------------------'' OCEANSIDE
[REPORT]
INPUT NO
CONTROLS NO
SUBCATCHMENTS ALL
FILE "OsideRain.prn"
_ J NODES ALL
LINKS ALL
_I
-,
[TAGS]
[MAP]
DIMENSIONS 2197.410 5592.134 2215.386 6341.510
Units None
[COORDINATES]
; ;Node X-Coord Y-Coord
··--------------------------------------------------'' POC 2192.087 5869.247
[VERTICES]
; ;Link
··--------------''
[Polygons]
;;Subcatchment
··--------------'' Compacted
Uncompacted
[SYMBOLS]
X-Coord
X-Coord
2281.812
2079.385
Y-Coord
Y-Coord
6023.978
6020.009
;;Gage X-Coord Y-Coord
. ·--------------------------------------------------'' OCEANSIDE 2193.697 6097.010
Tide
Gate
NO
2
_j
- J
J
_J
[TITLE]
[OPTIONS]
FLOW UNITS
INFILTRATION
FLOW ROUTING
START DATE
START TIME
REPORT START DATE - -REPORT START TIME
END DATE
END TIME
SWEEP START
SWEEP END
DRY DAYS
CFS
GREEN AMPT
KINWAVE
10/17/1948
00:00:00
10/17/1948
00:00:00
10/17/2005
23:00:00
01/01
12/31
0
REPORT STEP 01:00:00
WET STEP 00:15:00
DRY STEP 04:00:00
ROUTING STEP 0:01:00
ALLOW PONDING NO
INERTIAL DAMPING PARTIAL
VARIABLE STEP 0.75
LENGTHENING STEP 0
MIN SURFAREA 0
NORMAL FLOW LIMITED BOTH
SKIP STEADY STATE NO - -FORCE_MAIN_EQUATION H-W
LINK OFFSETS
MIN SLOPE
[EVAPORATION]
; ;Type
.. ----------''
DEPTH
0
Parameters
POST-DEVELOPMENT
MONTHLY 0.041 0.076 0.118 0.192 0.237 0.318 0.308 0.286 0.217 0.14
DRY ONLY NO
[RAINGAGES]
;;Name
Rain
Type
Time Snow Data
Intrvl Catch Source
··-----------------------'' OCEANSIDE INTENSITY 1:00 1. 0 TIMESERIES OCEANSIDE
[SUBCATCHMENTS]
;; Total Pent.
Snow
Pent.
0.067 0.041
Curb
;;Name Raingage Outlet Area Imperv Width Slope Length
Pack
··------------------------------ ---------------------------------------- -----------------''
AREA 1
LID 1
AREA 2
LID 2
[SUBAREAS]
;;Subcatchment
··--------------'' AREA 1
LID 1
AREA 2
LID 2
[ INFILTRATION]
;;Subcatchment
··--------------'' AREA 1
LID 1
AREA 2
LID 2
[LID_ CONTROLS]
OCEANSIDE
OCEANSIDE
OCEANSIDE
OCEANSIDE
N-Imperv
----------
0.012
.012
0.012
.012
Suction
----------
6.3
6.3
6.3
6.3
N-Perv
LID 1
DIV 1
LID 2
DIV 2
----------
0.05
.05
0.05
.05
HydCon
----------
0.075
.10
0.075
.10
2.83366 34.7 239 5 0
0.041437 0 10 1 0
0.76140 34.7 64 5 0
0.011134 0 10 1 0
S-Imperv S-Perv PctZero RouteTo PctRouted
-------------------- ------------------------------
0.02 0.1 25 OUTLET
.02 .1 25 OUTLET
0.02 0.1 25 OUTLET
.02 .1 25 OUTLET
IMDmax
----------
0.31
0.31
0.31
0.31
1
_j
. ·--------------'' BMP 1
BMP-1
BMP 1
BMP 1
BMP 1
BMP 2
BMP 2
BMP 2
BMP 2
BMP 2
Type/Layer
----------
BC
SURFACE
SOIL
STORAGE
DRAIN
BC
SURFACE
SOIL
STORAGE
DRAIN
Parameters
----------
12.24
18
12
0.2882
13.38
18
12
1. 0727
POST-DEVELOPMENT
0.05 0
0.4 0.2
0.67 0
0.5 0
.05 0
0.4 0.2
0.67 0
0.5 0
0
0.1
0
6
0
0.1
0
6
5
5
5
5
5 1.5
5 1. 5
[LID_USAGE]
;;Subcatchment
Report File
LID Process Number Area Width InitSatur Fromimprv ToPerv
. ·--------------''
LID 1
LID 2
[OUTFALLS]
;;
; ;Name
BMP 1
BMP 2
Invert
Elev.
1
1
Outfall
Type
1805
485
Stage/Table
Time Series
0
0
Tide
Gate
0
0
··--------------------------------------------------'' POC 0 FREE
[DIVIDERS]
Invert Diverted
; ;Name Elev. Link
··----------------------------------------,,
DIV 1
0
DIV 2
0
[STORAGE]
0
0
,, Invert
;;Name Elev.
Infiltration Parameters
··----------------------''
BASIN 1
BASIN 2
[CONDUITS]
;;
Init. Max.
; ;Name
Flow Flow
··--------------''
BYPASS 1
0
DUM 1
0
BYPASS 2
0
DUM 2
0
[OUTLETS]
Flap
; ;Name
Qexpon Gate
. ·--------------''
0
0
Inlet
Node
DIV 1
DIV 1
DIV 2
DIV 2
Inlet
Node
BYPASS
BYPASS
Max.
Depth
1. 50
1. 50
-
1
2
Init.
Depth
0
0
Outlet
Node
BASIN 1
POC
BASIN 2 -
POC
Outlet
Node
NO
Divider
Type Parameters
--------------------
CUTOFF
CUTOFF
Storage
Curve
TABULAR
TABULAR
0.4102
.04102
Curve
Par ams
BR 1
BR 2
Length
10
10
10
10
Outflow
Height
0
0
Manning
N
0.01
0.01
0.01
0.01
Outlet
Type
100
100
Inlet
0
0
0
0
Ponded
Area
1805
485
0
0
Outlet
Offset Offset
0 0
0 0
0 0
0 0
Qcoeff/
QT able
OUTLET 1
NO
BASIN 1 POC 0 TABULAR/DEPTH Outlet 1
2
Evap.
Frac.
1
0
0
0
0
0
J
J
OUTLET 2
NO
[XSECTIONS]
; ;Link
. ·--------------'' BYPASS 1
DUM 1
BYPASS 2
DUM 2
[LOSSES]
; ;Link
··--------------''
[CURVES]
;;Name
. ·--------------'' Outlet 1
Outlet 1 -Outlet 1
Outlet 1 -Outlet 1 -Outlet 1
Outlet 1
Outlet 1 -Outlet 1
Outlet 1 -Outlet 1
Outlet 1 -Outlet 1 -Outlet 1 -Outlet 1 -Outlet 1
Outlet 1
Outlet 1 -Outlet 1 -Outlet 1
Outlet 1
Outlet 1
Outlet 1
Outlet 1 -Outlet 1
Outlet 1 -Outlet 1
Outlet 1 -Outlet 1 -Outlet 1 -Outlet 1
Outlet 1 -Outlet 1 -
Outlet 1 -Outlet 1 -Outlet 1
Outlet 1
Outlet 2 -Outlet 2 -Outlet 2
Outlet 2
Outlet 2 -Outlet 2
Outlet 2
Outlet 2 -Outlet 2 -Outlet 2
Outlet 2
Outlet 2 -Outlet 2 -Outlet 2
Outlet 2
BASIN 2
Shape
DUMMY
DUMMY
DUMMY
DUMMY
Inlet
----------
Type
----------
Rating
Rating
POST-DEVELOPMENT
POC 0 TABULAR/DEPTH Outlet 2
Geoml Geom2 Geom3 Geom4 Barrels
--------------------------------------------------------
0 0 0 0 1
0 0 0 0 1
0 0 0 0 1
0 0 0 0 1
Outlet Average Flap Gate
------------------------------
X-Value Y-Value
--------------------
0.000 0.000
0.042 0.053
0.083 0.149
0.125 0.274
0.167 0.422
0.208 0.590
0.250 0.775
0.292 0.977
0.333 1.117
0.375 1. 224
0.417 1.322
0.458 1. 413
0.500 1. 499
0.542 1. 580
0.583 1. 657
0.625 1. 731
0.667 1. 801
0.708 1. 869
0.750 1.935
0.792 2.209
0.833 2.657
0.875 3.216
0.917 3.865
0.958 4.593
1. 000 5. 390
1. 042 6.250
1. 083 7.169
1.125 8.143
1.167 9.168
1. 208 10.243
1. 250 11. 364
1.292 12.530
1.333 13.740
1.375 14.990
1. 41 7 16.281
1. 458 17. 611
1.500 18. 978
0.000 0.000
0.042 0.053
0.083 0.149
0.125 0.274
0.167 0.422
0.208 0.590
0.250 0.775
0.292 0.977
0.333 1.117
0.375 1. 224
0.417 1. 322
0.458 1. 413
0.500 1. 499
0.542 1. 580
0.583 1. 657
3
POST-DEVELOPMENT -,
Outlet 2 0.625 1.731
Outlet 2 0.667 1. 801 -Outlet 2 0.708 1. 869 -Outlet 2 0.750 1.935
_J Outlet 2 0.792 2.209
Outlet 2 0.833 2.657 -Outlet 2 0.875 3.216
Outlet 2 0.917 3. 865
Outlet 2 0.958 4.593 -Outlet 2 1. 000 5.390 -Outlet 2 1.042 6.250
Outlet 2 1. 083 7.169
Outlet 2 1.125 8.143 -Outlet 2 1.167 9.168 -Outlet 2 1.208 10.243 -Outlet 2 1. 250 11.364 -Outlet 2 1. 292 12.530 -Outlet 2 1.333 13.740 -Outlet 2 1. 375 14.990
Outlet 2 1. 417 16.281
Outlet 2 1. 458 1 7. 611
Outlet 2 1. 500 18.978 -
BR 1 Storage 0.00 1879
BR 1 0.08 1886
BR 1 0.17 1893
BR 1 0.25 1899
_J BR 1 0.33 1906
BR 1 0.42 1913
BR 1 0.50 1920
BR 1 0.58 1926
BR 1 0.67 1933
J BR 1 0.75 1940
BR 1 0.83 1947
BR 1 0.92 1954
BR 1 1. 00 1961
BR 1 1. 08 1969
BR 1 1.17 1976
BR 1 1.25 1983
BR 1 1. 33 1990
BR 1 1. 42 1997
BR 1 1. 50 2005
BR 2 Storage 0.00 598
BR 2 0.08 608
BR 2 0.17 617
BR 2 0.25 627
BR 2 0.33 637
BR 2 0.42 647
BR 2 0.50 657
BR 2 0.58 666
BR 2 0.67 676
BR 2 0.75 686
--, BR 2 0.83 696
BR 2 0.92 706
BR 2 1. 00 716
BR 2 1. 08 727
BR 2 1.17 737
BR 2 1.25 747
BR 2 1.33 757
BR 2 1. 42 767
BR 2 1. 50 778
[TIMESERIES]
; ;Name Date Time Value
,,--------------------------------------------
OCEANSIDE FILE "OsideRain.prn"
[REPORT]
INPUT NO
CONTROLS NO
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SUBCATCHMENTS ALL
NODES ALL
LINKS ALL
[TAGS]
[MAP]
POST-DEVELOPMENT
DIMENSIONS 145.937 4732.028 1987.467 5730.960
Units None
[COORDINATES]
; ;Node
··--------------'' POC
DIV 1
DIV 2
BASIN 1
BASIN 2
[VERTICES]
; ;Link
. ·--------------''
[Polygons]
;;Subcatchment
··--------------'' AREA 1
AREA 1
LID 1
AREA 2
LID 2
[SYMBOLS]
; ;Gage
··--------------'' OCEANSIDE
X-Coord
1153.425
756.944
1445.641
229.643
1903.761
X-Coord
X-Coord
751.862
751.862
753.748
1446.285
1445.222
X-Coord
1104.408
Y-Coord
4777.434
5245.370
5269.489
5244.981
5269.489
Y-Coord
Y-Coord
5682.363
5682.363
5467.442
5685.554
5480.345
Y-Coord
5678.592
5
ATTACHMENT 7
SWMM Screens and Explanation of Significant Variables
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ATTACHMENT 7
EPA SWMM FIGURES AND EXPLANATIONS
Per the attached, the reader can see the screens associated with the EPA-SWMM Model in both
pre-development and post-development conditions. Each portion, i.e., sub-catchments,
outfalls, storage units, weir as a discharge, and outfalls (point of compliance), are also shown.
Variables for modeling are associated with typical recommended values by the EPA-SWMM
model and typical values found in technical literature (such as Maidment's Handbook of
Hydrology). Recommended values for the SWM M model have been attained from the interim
Orange County criteria established for their SWMM calibration. Currently, no recommended
values have been established by the San Diego County HMP Permit for the SWMM Model.
Soil characteristics of the existing soils were determined from the site specific Geotechnical
Analysis {See Attachment 8).
Some values incorporated within the SWMM model have been determined from the
professional experience of TRWE using conservative assumptions that have a tendency to
increase the size of the needed BMP and also generate a long-term runoff as a percentage of
rainfall similar to those measured in gage stations in Southern California by the USGS.
ii[
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1.:· ·# ti
Outfalls
PRE-DEVELOPED CONDITION
OCEANSIDE
12]
Uncompac!ed .. .
\ POC ..
Compacte<l
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Tag .. '. :-:··:
,,,· .. · ...... ., __ ,.., .. • ••••••••w••w•ss00 ss,·'···/.u,.:.C".
Rain Format .•·•••.•••!INTENSITY
""w.w."""·""'w=w.•.•.
Tirne Interval ... • ;1 :00
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ftlropl:ltY
N~Perv
D$tOrt:t·1mperv.
Land Otes
lniti91 Bwildup
• ·:.·. •• •••• ••••••••••,•,•mmssSs,• •• wu.u
Curb Length
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Title/Notes
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POST-DEVELOPED CONDITION
.! i!+~>\:,.:t$i
AREA 1 ' -
LID 1 r -
BYPASS_1 DJV_1
OUTLET_1
LID 2 . -
D1\t_2 BYPASS_2 B-'\S1N_2
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' '
Infiltration
Groundwater
Snow Pack
1.,1 D Control:S
LandUres
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, __ )
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EXPLANATION OF SELECTED VARIABLES
Sub Catchment Areas:
Please refer to the attached diagrams that indicate the OMA and Biofiltration IMP (IMP) sub areas
modeled within the project site at both the pre and post developed conditions draining to the POC.
Parameters for the pre-and post-developed models include soil type B/C (an average of types B and C)
and type D as determined from the Geotechnical Analysis (see Attachment 8). Suction head,
conductivity and initial deficit corresponds to average values expected for these soils types, according to
sources consulted, professional experience, and approximate values obtained by the interim Orange
County modeling approach. For this particular project weighted values were used to model the site, as
about 60% of the soils are Type B/C and 40% are Type D. Table 1 below shows the breakdown of the Soil
types and Table 2 shows the weighted values that were used.
TABLE 1-SUMMARY OF SOIL TYPES
B/C 96109 60%
D 62782 40%
Total 158891 100%
TABLE 2 -SUMMARY OF GREEN_AMPT VALUES
Suction Head 3 6 4.5 9 6.3
Undeveloped Conductivity 0.2 0.1 0.15 0.025 0.100
Developed Conductivity 0.15 0.075 0.1125 0.01875 0.075
Initial deficit 0.32 0.31 0.315 0.3 0.31
t1lTypical Values used for SWMM modeling.
t2l Average of Type Band Type C values.
TRWE selected infiltration values, such that the percentage of total precipitation that becomes runoff is
realistic for the soil types and slightly smaller than measured values for Southern California watersheds.
Selection of a Kinematic Approach: As the continuous model is based on hourly rainfall, and the time of
concentration for the pre-development and post-development conditions is significantly smaller than 60
minutes, precise routing of the flows through the impervious surfaces, the underdrain pipe system, and
the discharge pipe was considered unnecessary. The truncation error of the precipitation into hourly
steps is much more significant than the precise routing in a system where the time of concentration is
much smaller than 1 hour.
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Sub-catchment IMP:
The area of each of the bio-filtration must be equal to the area of the development tributary to the bio-
filtration facility (area that drains into the bio-filtration, equal external area plus bio-retention itself).
Five (5) decimal places were given regarding the areas of the bio-retention to insure that the area used
by the program for the LID subroutine corresponds exactly with this tributary.
% of Sul:u:atchrnenfOccupied
Top Width of0ve1land Flow
Surface of !:,~ch Unit (ft or ITI}
% Initially Saturated
Nun1bertfReplicale Units
lEJUD Occupiesfull S ubcatchmenC-
Area of Each Unit ( sq ft or sq m) 485
.. . .
% of Subca\ehment Oc:l'.ajpied
Top Width of Overland Flow
Surface ofEabh Unit~tor
·z Initial~ Saturati::d
% of Impervious Area T rei:lted
100.0
100
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Storage Depth
(in. ormm)
Vegetation Volume
Fraction
Surf ace Roughness
(Mannings n)
Surf ace Slope
(percent)
(in. ormm)
Void Ratio
[Voids I Solids)
Conductivit_l!
(in/hr or mm/hr)
Clogging Factor
0.05
0
0
12
0.67
0
0
Note: use a Conductivit_l! of O if the LID
unit has an impermeable bottom.
Process Layer;:
rW!flg:~oil l,$tpi¥1,MPd!!tw~·· ----------"·"·-·-· ··1
Thickness
(in. ormm)
Porosity
( volume fr action)
Field Capacity
(volume fraction)
Wilting Point
(volume fraction)
Conductivity
(in/hr or mm/hr)
Conductivity Slope
Suction Head
(in. or mm)
18
0.4
0.2
0.1
5
5
1.5
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!
I ,·
i
!
····· ..... -............... --................................ .J
Drain Coefficient
(in/hr or mm/hr)
Drain Exponent
Drain Offset Height
[in. ormm)
0.2882
0.5
Note: use a Drain Coefficient of O if the
LID unit has no underdr ain.
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5 tor age Depth
[in. or mm)
Vegetation Volume
Fraction
Surf ace Roughness
(Mannings n)
5 urf ace Slope
[percent)
Height
[in. or mm)
Void Ratio
[\I oids I Solids)
Conductivity
[in/hr or mm/hr)
Clogging Factor
13.38
.05
0
0
12
0
0
Note: use a Conductivity of O if the LID
unit has an impermeable bottom.
Thickness
[in. ormm)
Porosity
(volume fraction)
Field Capacity
[volume fraction)
'Wilting Point
[volume fraction)
Conductivity
[in/hr or mm/hr)
Conductivity Slope
5 uction Head
[in. ormm)
Drain Coefficient
[in/hr or mm/hr J
Drain Exponent
Drain Offset Height
[in. or mm)
18
0.4
0.2
0.1
5
5
1.5
.1.0727
0.5
0
Note: use a Drain Coefficient of O if the
LID unit has no underdr ain.
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LID Control Editor: Explanation of Significant Variables
Storage Depth:
The storage depth variable within the SWMM model is representative of the storage volume
provided beneath the engineered soil and mulch components of the biofiltration facilities.
In those cases where the surface storage has a variable area that is also different to the area of
the gravel and amended soil, the SWMM model needs to be calibrated as the LID module will
use the storage depth multiplied by the IMP area as the amount of volume stored at the
surface.
Let A1MP be the area of the IMP (area of amended soil and area of gravel). The proper value of
the storage depth S0 to be included in the LID module can be calculated by using geometric
properties of the surface volume. Let Ao be the surface area at the bottom of the surface pond,
and let Ai be the surface area at the elevation of the invert of the first row of orifices (or at the
invert of the riser if not surface orifices are included). Finally, let hi be the difference in
elevation between Ao and Ai. By volumetric definition:
A S -(Ao+Ai) h
IMP. D -2 i (1)
Equation (1) allows the determination of S0 to be included as Storage Depth in the LID module.
Porosity: A porosity value of 0.4 has been selected for the model. The amended soil is to be
highly sandy in content in order to have a saturated hydraulic conductivity of approximately 5
in/hr.
TRWE considers such a value to be slightly high; however, in order to comply with the HMP
Permit, the value recommended by the Copermittees for the porosity of amended soil is 0.4,
per Appendix A of the Final Hydromodification Management Plan by Brown & Caldwell, dated
March 2011. Such porosity is equal to the porosity of the gravel per the same document.
Void Ratio: The ratio of the void volume divided by the soil volume is directly related to
porosity as n/(1-n). As the underdrain layer is composed of gravel, a porosity value of 0.4 has
been selected (also per Appendix A of the Final HMP document), which results in a void ratio of
0.4/(1-0.4) = 0.67 for the gravel detention layer.
Conductivity: Due to the natural soil and geotechnical conditions existing on site, infiltration is
not considered a viable addition to the LID design.
Clogging factor: A clogging factor was not used (0 indicates that there is not clogging assumed
within the model). The reason for this is related to the fairness of a comparison with the SDHM
model and the HMP sizing tables: a clogging factor was not considered, and instead, a
conservative value of infiltration was recommended.
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Drain (Flow) coefficient: The flow coefficient in the SWMM Model is the coefficient needed to
transform the orifice equation into a general power law equation of the form:
q = C(H-Hvr (1)
where q is the peak flow in in/hr, n is the exponent (typically 0.5 for orifice equation), HD is the
elevation of the centroid of the orifice in inches (assumed equal to the invert of the orifice for
small orifices and in our design equal to O) and His the depth of the water in inches.
The general orifice equation can be expressed as:
Q _ Tr D 2 z (H-Hn) -c -g -4 g 144 12 (2)
where Q is the peak flow in cfs, D is the diameter in inches, Cg is the typical discharge coefficient
for orifices (0.61-0.63 for thin walls and around 0.75-0.8 for thick walls), g is the acceleration of
gravity in ft/s2, and Hand HD are defined above and are also used in inches in Equation (2).
Detention Basin
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m ..... ww.•,•
Flap Gatit< No<
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Description
==--=,,,-.. """=",.
. . . . . . . . : . . . ....... . ..... . . ·· ... ·.. . . .· ...... ·.···.•·.•.· .......... Jt]
0.042 0.053
3 0.083 0.149
4 0.125 0.274
0.422
0.590
_J 0.977
User-assigned name of outlet
Note: The complete storage and rating curves and the respective explanation is shown at the end of
Attachment 4. A variable area vs. elevation storage curve was used for the final model, and a discharge
that is a function of the outlet structure in the surface was used also.
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ATTACHMENT 8
Geotechnical Report
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GEOTECHNICAL INVESTIGATION,
PROPOSED AFTON WAY RESIDENTIAL
DEVELOPMENT
2200 AFTON WAY, CARLSBAD, CALIFORNIA
Prepared for:
PRESIDO MANA CARLSBAD 9, LLC
5927 Balfour Court
Carlsbad, California 92008
Project No. 10690.002
September 29, 2014
----Leighton and Associates 1 Inc. ~-~
A lE!(HHON GROUP COMPtU\!Y
Leighton and Associates 1 Inc,
A LEIGHTON GROUP COMPANY
Preside Mana Carlsbad 9, LLC
5927 Balfour Court
Carlsbad, California 92008
Attention: Mr. Orville Power
September 29, 2014
Subject: Geotechnical Investigation
Proposed Afton Way Residential Development,
Project No. 10690.002
2200 Afton Way, Carlsbad, San Diego County, California
In accordance with your request and authorization, we have conducted a geotechnical
investigation of the property for the design and construction of the proposed residential
development project.
Based on the results of our study, it is our professional opinion that the site is suitable to
receive the proposed improvements. The accompanying report presents a summary of
our current investigation and provides geotechnical conclusions and recommendations
relative to the proposed site development.
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongroup.com
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If you have any questions regarding our report, please do not hesitate to contact this
office. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
Mike Jensen, CEG 2457
Project Geologist
!v'L 1J.&L ______ _
William D. Olson, RCE 45283
Associate Engineer
Bryan Voss, PG 8709
Project Geologist
Distribution: (3) Addressee
Geotechnical Investigation, 2200 Afton Way. Carlsbad, California 10690.002
TABLE OF CONTENTS
Section
1.0 INTRODUCTION .............................................................................................. 1
1.1 PURPOSE AND SCOPE ... ········· ................................................................................. 1
1.2 SITE LOCATION AND DESCRIPTION ............................................................................ 1
1.3 PROPOSED DEVELOPMENT ...................................................................................... 2
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING ......... 3
2.1 SITE INVESTIGATION································································································ 3
__ _.I 2.2 LABORATORY TESTING ............................................................................................ 3
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS ...................................... 4
3.1 GEOLOGIC SETTING ................................................................................................ 4
3.2 SITE-SPECIFIC GEOLOGY ........................................................................................ 4
3.2.1 Artificial Fill -Undocumented -(Afu) ............................................................. 4
3.2.2 Colluvium (Qc) ............................................................................................... 5
3.2.3 Slope Wash Deposits (Qsw) .......................................................................... 5
3.2.4 Very Old Paralic Deposits (Qvop) .................................................................. 5
3.2.5 Santiago Formation (Tsa) .............................................................................. 6
3.3 SURFACE AND GROUND WATER··············································································· 6
3.4 ENGINEERING CHARACTERISTICS OF ON-SITE SOILS .................................................. 6
3.4.1 Expansion Potential ....................................................................................... 7
3.4.2 Compressible Soils ........................................................................................ 7
3.4.3 Soil Corrosivity .............................................................................................. 7
3.4.4 Infiltration ....................................................................................................... 7
3.4.5 Excavation Characteristics ............................................................................ 8
3.5 SLOPE STABILITY···································································································. 8
3.6 EARTHWORK SHRINKAGE AND BULKING .................................................................... 9
4.0 SEISMIC AND GEOLOGIC HAZARDS ..................................................... 10
4.1 REGIONAL TECTONIC SETTING ............................................................................... 10
4.2 LOCAL FAUL TING ················································· ················································· 10
4.3 SEISMICITY ........................................................................................................... 10
4.4 SEISMIC HAZARDS ................................................................................................ 10
4.4.1 Shallow Ground Rupture ............................................................................. 11
4.4.2 Mapped Fault Zones ................................................................................... 11
4.4.3 Site Class .................................................................................................... 11
4.4.4 Building Code Mapped Spectral Acceleration Parameters .......................... 11
4.5 SECONDARY SEISMIC HAZARDS ............................................................................. 12
4.5.1 Liquefaction and Dynamic Settlement ......................................................... 12
4.5.2 Lateral Spread ............................................................................................. 13
4.5.3 Tsunamis and Seiches ................................................................................ 13
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
TABLE OF CONTENTS (Continued)
__ J Section
4.6 LANDSLIDES ............ ············ ................................................................................. 13
4.7 FLOOD HAZARD .................................................................................................... 14
-, 5.0 CONCLUSIONS .............................................................................................. 15
: _J 6.0 RECOMMENDATIONS .................................................................................. 17
6.1 EARTHWORK ............................................................................................ ······ ...... 17
j 6.1.1 Site Preparation ........................................................................................... 17
6.1.2 Removal of Compressible Soils ................................................................... 17
-, 6.1.3 Cut/Fill Transition Mitigation ........................................................................ 18
6.1.4 Excavations and Oversize Material ............................................................. 18
6.1.5 Engineered Fill ............................................................................................ 19
6.1.6 Import Soils ................................................................................................. 20
6.1.7 Expansive Soils and Selective Grading ....................................................... 20
6.1.8 Buttress/Replacement Fill. ........................................................................... 20
6.2 FOUNDATION AND SLAB CONSIDERATIONS .............................................................. 21
6.2.1 Conventional Foundations ........................................................................... 21
6.2.2 Foundation Setback .................................................................................... 23
6.2.3 Settlement ................................................................................................... 24
6.2.4 Moisture Conditioning .................................................................................. 25
6.2.5 Post-Tension Foundation Recommendations .............................................. 26
6.3 LATERAL EARTH PRESSURES AND RETAINING WALL DESIGN .................................... 27
6.4 GEOCHEMICAL CONSIDERATIONS ........................................................................... 29
6.5 CONCRETE FLATWORK .......................................................................................... 29
6.6 PRELIMINARY PAVEMENT DESIGN ........................................................................... 29
6.7 CONTROL OF GROUND WATER AND SURFACE WATERS ............................................ 31
6.8 CONSTRUCTION OBSERVATION ·············································································· 32
6.9 PLAN REVIEW .................................................... ············ ....................................... 32
7. 0 LIMITATIONS ................................................................................................. 33
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
TABLE OF CONTENTS (Continued)
TABLES
TABLE 1 -EARTHWORK SHRINKAGE AND BULKING ESTIMATES-PAGE 9
TABLE 2-2013 CBC MAPPED SPECTRAL ACCELERATION PARAMETERS-PAGE 12
TABLE 3-MINIMUM FOUNDATION AND SLAB DESIGN RECOMMENDATIONS FOR
CONVENTIONAL REINFORCED FOUNDATIONS -PAGE 22
TABLE 4-MINIMUM FOUNDATION SETBACK FROM SLOPE FACES -PAGE 24
TABLE 5-PRESOAKING RECOMMENDATIONS BASED ON FINISHED GRADE
SOIL EXPANSION POTENTIAL -PAGE 25
TABLE 6-POST-TENSIONED FONDATION DESIGN RECOMMENDATIONS-PAGE 26
TABLE 7-STATIC EQUIVALENT FLUID WEIGHT (PCF)-PAGE 28
TABLE 8-PRELIMINARY PAVEMENT SECTIONS -PAGE 30
FIGURE AND PLATES
FIGURE 1 -SITE LOCATION MAP -REAR OF TEXT
PLATE 1 -GEOTECHNICAL MAP -REAR OF TEXT
PLATE 2-GEOLOGIC CROSS-SECTION A-A' -REAR OF TEXT
APPENDICES
APPENDIX A -REFERENCES
APPENDIX B -TEST PIT LOGS AND BORING LOGS
APPENDIX C-LABORATORY TESTING PROCEDURES AND TEST RESULTS
APPENDIX D-GENERAL EARTHWORK AND GRADING SPECIFICATIONS FOR ROUGH GRADING
APPENDIX E-ASSOCIATION OF ENGINEERING FIRMS PRACTICING IN THE GEOSCIENCES
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
1.0 INTRODUCTION
We recommend that all individuals utilizing this report read the preceding information
sheet prepared by ASFE (the Association of Engineering Firms Practicing in the
Geosciences) and the Limitations, Section 7.0, located at the end of this report.
1.1 Purpose and Scope
This report presents the results of our geotechnical investigation for the site
_J located at 2200 Afton Way in the City of Carlsbad, California (Figure 1 ). The
intent of this report is to provide specific geotechnical conclusions and
recommendations for the currently proposed project.
1.2 Site Location and Description
The subject property encompasses approximately 3.92 acres of essentially
undeveloped land located at 2200 Afton Way in Carlsbad, California (see Site
Location Map, Figure 1 ). The site is bordered by Carlsbad Village Drive to the
north, and existing residential developments to the east, south, and west.
Topographically, the property consists of gently sloping hillside terrain with
elevations ranging from a high of approximately 280 feet Mean Sea Level (MSL)
near the southwestern property line to a low of approximately 205 feet (MSL) at the
property's northeastern corner. Currently, the property is occupied by one
residential structure with two sheds. An existing crib wall, approximately 26 foot
high and 300 feet long, is located along the north of the boundary of the site and
appears to have been constructed during the alignment of Carlsbad Village Drive.
It should be noted that the existing cribwall may be impacted by the proposed
improvements and require remedial grading activities. Site drainage is presently
accomplished through a generally southeasterly trending ravine and ultimately
through controlled drainage facilities along Carlsbad Village Drive. Vegetation
consists of native grasses and eucalyptus trees over the majority of the site.
Site Latitude and Longitude
33.1721° N
117.3268° w
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
1.3 Proposed Development
Based on our review of the provided preliminary grading plan by BHA, Inc. (BHA,
Inc., 2014), the property will be developed with nine, one-or two-story single-family
homes, with associated infrastructure and underground utility improvements. We
further understand that the residential structures would utilize conventional
continuous footings with slab-on-grade and/or post-tension systems. Building
loads are assumed to be typical for these types of relatively light structures.
Currently, no structural plans for the proposed buildings are available.
Typical cut and fill grading techniques would be required to bring the site to design
elevations. Based on our review, cut and fill slopes are proposed at inclinations of
2:1 (horizontal:vertical [H:V]), or flatter, with maximum planned slope heights of
about 10 and 23 feet, respectively. Cuts and fills are currently proposed up to
about 13 and 12 feet in thickness, respectively, (excluding remedial grading
removals). Sewage disposal is understood to be accommodated by tying into the
regional municipal system.
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2.1
2.2
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING
Site Investigation
Our exploration consisted of the excavation, logging, and sampling three large
diameter borings (LD-1 through LD-3) and 6 test pit excavations (TP-1 through
TP-6). Excavation depths ranging from of approximately 9 feet to 51 feet below
the existing ground surface (bgs). The approximate locations of the explorations
are shown on the Geotechnical Map (Plate 1 ). Subsequent to the subsurface
investigation, the test pits were backfilled with tamped soils and the large
diameter boring excavations were backfilled with spoils and layers of bentonite in
accordance with the San Diego County DEH Boring Permit Wavier. During the
exploration operations, a geologist from our firm prepared geologic logs and
collected bulk and undisturbed samples for laboratory testing and evaluation.
Logs of the explorations are presented in Appendix B.
Laboratory T estinq
Laboratory testing performed on soil samples representative of on-site soils
obtained during the recent subsurface exploration included, expansion potential,
grain size analysis, corrosion test, direct shear tests on drive samples, moisture
test, and atterberg limits. A discussion of the laboratory tests performed and a
summary of the laboratory test results are presented in Appendix C.
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3.1
3.2
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS
Geologic Setting
The project area is situated in the Peninsular Ranges Geomorphic Province. This
geomorphic province encompasses an area that extends approximately 900
miles from the Transverse Ranges and the Los Angeles Basin south to the
southern tip of Baja California, and varies in width from approximately 30 to 100
miles (Norris and Webb, 1990). The province is characterized by mountainous
terrain on the east composed mostly of Mesozoic igneous and metamorphic
rocks, and relatively low-lying coastal terraces to the west underlain by late
Cretaceous-age, Tertiary-age, and Quaternary-age sedimentary units. Most of
the coastal region of the County of San Diego, including the site, occur within this
coastal region and are underlain by sedimentary units. Specifically, the subject
site is located within the coastal plain section of the Peninsular Range Geomorphic
Province of California, which generally consists of subdued landforms underlain by
sedimentary bedrock.
Site-Specific Geology
Based on our subsurface exploration and review of pertinent geologic literature
and maps (Appendix A), the geologic units underlying the site consist of localized
undocumented artificial fill, colluvium, and slope wash deposits overlying terrace
deposits (Quaternary-aged Very Old Paralic Deposits) and Tertiary-age Santiago
Formation across the entire site area. A brief description of the geologic units
encountered on the site is presented below. The general distribution of earth
materials are shown on Plate 1 .
3.2.1 Artificial Fill -Undocumented -(Afu)
During our subsurface exploration, an approximately 2-to 10-foot thick
layer of undocumented artificial fill soils was encountered at several of the
exploration locations. The fill was apparently placed during the site's initial
construction and isolated deeper fills may exist that were not observed
during our exploration. An as-graded report was not available for our
review, and it is assumed that no engineering observations of these
localized fill soils were provided at the time of grading. These fill soils
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generally consisted of a mixture of silty sand and sandy clay, are dry,
loose and may settle appreciably under additional fill or foundation and
improvement loading. Therefore, all undocumented fills (soil) should be
removed and recompacted. These materials may be reused provided they
are cleared of trash and debris. All trash and debris should be removed,
and properly disposed offsite, prior to fill placement and/or remedial
grading.
3.2.2 Colluvium (Qc}
In general, the southern portion of the site is mantled by a relatively thin
layer of colluvium. The colluvium was generally observed to be reddish
brown to brown, dry, porous, loose, silty sand. Locally roots and rootlets
were noted within these surficial soils. The colluvium was generally
encountered ranging from approximately 2 to 4 feet in thickness. Due to
the potentially compressible nature of these surficial soils, they are
considered unsuitable for the support of structures and/or improvements in
their existing state. Therefore, these soils will need to be removed and
recompacted, if not removed during planned excavation, should
settlement sensitive improvements be proposed within their influence.
3.2.3 Slope Wash Deposits (Qsw)
The northern portion of the site is mantled by a layer of slope wash. The
slope wash was generally observed to be orange brown to grayish brown,
dry to moist, porous, loose, silty sand to clayey sand. The slope wash was
generally encountered ranging from 9 to 10 feet in thickness. Due to the
potentially compressible nature of these surficial soils, they are considered
unsuitable for the support of structures and/or improvements in their
existing state. Therefore, these soils will need to be removed and
recompacted, if not removed during planned excavation, should
settlement sensitive improvements be proposed within their influence.
3.2.4 Very Old Paralic Deposits (Qvop}
Quaternary-aged Very Old Paralic Deposits (previously referred to as
terrace deposits) underlie the colluvium soils at southern portion site. This
unit primarily consists of massively bedded, reddish-to orange brown,
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3.3
oxidized, weakly to moderately cemented, dense to very dense, silty
sandstone and clayey sandstone, and are locally weathered near the
surface. The weathered near surface Very Old Paralic Deposits (upper 1
to 2 feet), where encountered, should be removed and recompacted, if not
removed during planned excavation, should settlement sensitive
improvements be proposed within their influence.
3.2.5 Santiago Formation (Tsa)
Sandstone, clayey siltstone, and claystone sedimentary bedrock
belonging to Eocene-age Santiago Formation, was encountered onsite.
These deposits occur at depth within the property. Where unweathered,
these rocks are considered suitable for structural support. Bedding
structures observed in our large diameter explorations indicate a
northwesterly trend with a southeasterly dip on the order of 10 degrees.
Surface and Ground Water
The regional groundwater table was not encountered in the explorations, to a
depth of 51 feet deep. Based on our review of the topographic quadrangle map
(USGS, 1967), groundwater level are anticipated at least 200 feet below the site
surface, which corresponds with Buena Vista Lagoon, north of the subject site.
Therefore, we anticipate the lowest site foundations will be well above the
existing static ground water table at the site.
Seeps, springs, or other indications of a high groundwater level were not noted
on the subject property during the time of our field study. However, seepage may
occur locally (due to heavy precipitation or irrigation) in areas where fill soils
overlie silty or clayey soils. Such soils may be encountered at the site. Mitigation
of seepage may be necessary during site grading.
3.4 Engineering Characteristics of On-site Soils
Based on the results of our laboratory testing of representative on-site soils, and
our professional experience on similar sites with similar soils conditions, the
engineering characteristics of the on-site soils are discussed below.
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3.4.1 Expansion Potential
Laboratory testing was performed to evaluate the expansion index of
materials characteristic of the site. The sample tested had an expansion
index of 53. Based on our field observations, subsurface investigation, and
laboratory testing, low to medium expansive soils are anticipated for this
site. High expansive soils may be encountered during site grading in
isolated layers.
3.4.2 Compressible Soils
Based on our experience on similar projects in the Carlsbad and our site
specific exploration, we expect that the upper 2 to 10 feet of the site is
underlain by undocumented fill, colluvium, or slope wash deposits which
are considered compressible. Recommendations for remedial grading of
these soils are provided in the following sections of this report.
3.4.3 Soil Corrosivity
A preliminary corrosive soil screening for the on-site materials was
completed to evaluate their potential effect on concrete and ferrous
metals. The corrosion potential was evaluated using the results of
laboratory testing on one representative soil sample obtained during our
subsurface evaluation.
Laboratory testing was performed to evaluate pH, minimum electrical
resistivity, and chloride and soluble sulfate content. The samples tested had
a measured pH of 7.19, and a measured minimum electrical resistivity of
8,240 ohm-cm. Test results also indicated that the samples had a chloride
content of 62.3 ppm, and a soluble sulfate content of less than 0.015
percent.
3.4.4 Infiltration
We performed percolation testing in Percolation Holes P-1 and P-2 to
evaluate suitability of the site for infiltration of storm water. The results of
the percolation test indicated that the site soils had a percolation rate of
greater than 125 minutes per inch (mpi). Generally, a percolation rate less
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than 120 mpi is considered necessary to consider a site suitable for onsite
infiltration of storm water. Additionally, the presence of shallow clayey
sand and clay materials present in much of the site would be expected to
impede infiltration and a 30-mil HOPE should be considered to line any
proposed infiltration basins. Further evaluation of proposed LIDs is
needed to determine potential down gradient impacts.
3.4.5 Excavation Characteristics
The site is underlain by undocumented fill, colluvium, slope wash deposits,
Very Old Paralic Deposits, and Santiago Formation generally consisting of
silty to clayey sands and sandy claystone to clayey sandstone. With
regards to the proposed project, it is anticipated these on-site soils can be
excavated with conventional heavy-duty construction equipment. Oversize
cobble material (typically over 6 inches in maximum dimension) is present
locally in the Paralic Deposits. Oversize cobble material should be placed
in non-structural areas or hauled off-site.
3.5 Slope Stability
Based on the available data, it is anticipated that proposed fill slopes will be
generally stable assuming proper construction and maintenance. Cut slopes, up to
proposed heights of 10 feet, that are constructed in Very Old Paralic Deposits and
earth materials belonging to Santiago Formation, are also anticipated to be
generally stable assuming proper construction and maintenance. However,
southeast-facing cut slopes constructed in the Santiago Formation may exhibit
i adverse (out of slope) bedding orientations and may require stabilization and
buttressing. Cut slopes constructed to the anticipated heights in competent
bedrock should perform adequately at gradients of 2:1 (H:V), or flatter, and are
considered to be generally stable assuming proper construction and maintenance.
Additional site specific analysis may be warranted once final 40-scale grading
plans have been developed. All cut slopes constructed will require observation
during grading in order to verify the findings and conclusions presented herein.
The cut slope in the northwestern portion of the site adjacent to Lot 4 will likely
expose slope wash material which will require removal and construction of a
buttress replacement fill with a key way at the toe of slope. Recommendations for
the buttress/replacement fill is presented on the Geotechnical Map (Plate 1 ).
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3.6
All slopes may be susceptible to surficial slope instability and erosion given
substantial wetting of the slope face. Surficial slope stability may be enhanced by
providing proper site drainage. The site should be graded so that water from the
surrounding areas is not able to flow over the top of slopes. Diversion structures
should be provided where necessary. Surface runoff should be confined to gunite-
lined swales or other appropriate devices to reduce the potential of erosion. Slopes
should be planted with vegetation that will increase the surficial stability.
Earthwork Shrinkage and Bulking
The volume change of excavated on-site materials upon recompaction as fill is
expected to vary with materials and location. Typically, the surficial soils and
bedrock materials vary significantly in natural and compacted density, and
therefore, accurate earthwork shrinkage/bulking estimate cannot be determined.
We do not anticipate significant grading at the site where bulking and shrinkage
estimates are necessary. However, if needed, the following factors (based on
evaluation of our subsurface investigation, laboratory testing, geotechnical
analysis and professional experience on similar sites) are provided on Table 1 as
guideline estimates. If possible, we suggest an area where site grades can be
adjusted be provided as a balance area.
Table 1
Earthwork Shrinkage and Bulking Estimates
Geologic Unit Estimated Shrinkage/bulking
Colluvium/Undocumented fill 5 to 15 percent shrinkage
Slope Wash Deposits 4 to 8 percent shrinkage
Paralic Deposits and 2 to 10 percent bulking
Santiago Formation
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4.1
4.0 SEISMIC AND GEOLOGIC HAZARDS
Regional Tectonic Setting
During the late Pliocene, several new faults developed in Southern California,
creating a new tectonic regime superposed on the flat-lying section of Tertiary
and late Cretaceous rocks in the San Diego region. One of these fault systems is
the Rose Canyon Fault Zone.
The principal known onshore faults in southernmost California are the San
Andreas, San Jacinto, Elsinore, Imperial and Rose Canyon faults, which
collectively transfer the majority of this deformation. The balance of the plate
margin slip, is taken by the offshore zone of faults which include the Coronado
Bank, Descanso, San Diego Trough, and San Clemente faults off of the San
Diego and northern Baja California coastline. Most of the offshore faults coalesce
south of the international border, where they come onshore as the Agua Blanca
fault which transects the Baja California peninsula (Jennings, 2010).
4.2 Local Faulting
Our review of available geologic literature (Appendix A) indicates that there are
no known significant or active or potentially active faults transecting, or projecting
toward the site. The nearest active fault is the Rose Canyon I Newport -
Inglewood (offshore) fault zone located approximately 6.9 miles west of the site
within the Pacific Ocean (Treiman, 1993).
4.3 Seismicity
The site can be considered to lie within a seismically active region, as can all of
Southern California. As previously mentioned above, the Rose Canyon fault zone
located approximately 6.9 miles west of the site, is the 'active' fault considered
having the most significant effect at the site from a design standpoint.
4.4 Seismic Hazards
Severe ground shaking is most likely to occur during an earthquake on one of the
regional active faults in Southern California. The effect of seismic shaking may
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be mitigated by adhering to the California Building Code or state-of-the-art
seismic design parameters of the Structural Engineers Association of California.
4.4.1 Shallow Ground Rupture
As previously discussed, no faults are mapped transecting or projecting
toward the site. Therefore, surface rupture hazard due to faulting is
considered very low. Ground cracking due to shaking from a seismic event
is not considered a significant hazard either, since the site is not located
near slopes.
4.4.2 Mapped Fault Zones
The site is not located within a State mapped Earthquake Fault Zone
(EFZ). As previously discussed, the subject site is not underlain by known
active or potentially active faults.
4.4.3 Site Class
Utilizing 2013 California Building Code (CBC) procedures, we have
characterized the site soil profile to be Site Class D based on our
experience with similar sites in the project area and the results of our
subsurface evaluation.
4.4.4 Building Code Mapped Spectral Acceleration Parameters
The effect of seismic shaking may be mitigated by adhering to the
California Building Code and state-of-the-art seismic design practices of
the Structural Engineers Association of California. Provided below in
Table 2 are the risk-targeted spectral acceleration parameters for the
project determined in accordance with the 2013 California Building Code
(CBSC, 2013a) and the USGS Worldwide Seismic Design Values tool
(Version 3.1.0).
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4.5
Table 2
2013 CBC Mapped Spectral Acceleration Parameters
Site Class D
Fa = 1.056 Site Coefficients Fv = 1.573
Mapped MCER Spectral Ss = 1.110
Accelerations S1 = 0.427
Site Modified MCER Spectral SMs = 1.172
Accelerations SM1 = 0.672
Sos = 0.781 Design Spectral Accelerations
So1 = 0.448
Utilizing ASCE Standard 7-10, in accordance with Section 11.8.3, the
following additional parameters for the peak horizontal ground
acceleration are associated with the Geometric Mean Maximum
Considered Earthquake (MCEG). The mapped MCEG peak ground
acceleration (PGA) is 0.432g for the site. For a Site Class D, the FPGA is
1.068 and the mapped peak ground acceleration adjusted for Site Class
effects (PGAM) is 0.461 g for the site.
Secondary Seismic Hazards
In general, secondary seismic hazards can include soil liquefaction, seismically-
induced settlement, lateral displacement, surface manifestations of liquefaction,
landsliding, seiches, and tsunamis. The potential for secondary seismic hazards
at the subject site is discussed below.
4.5.1 Liquefaction and Dynamic Settlement
Liquefaction and dynamic settlement of soils can be caused by strong
vibratory motion due to earthquakes. Granular soils tend to density when
subjected to shear strains induced by ground shaking during earthquakes.
Research and historical data indicate that loose granular soils underlain by
a near surface ground water table are most susceptible to liquefaction,
while the most clayey materials are not susceptible to liquefaction.
Liquefaction is characterized by a loss of shear strength in the affected
soil layer, thereby causing the soil to behave as a viscous liquid. This
effect may be manifested at the ground surface by settlement and,
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possibly, sand boils where insufficient confining overburden is present
over liquefied layers. Where sloping ground conditions are present,
liquefaction-induced instability can result.
The site is underlain at depth by moderately cemented sandstones and
moderately well indurated siltstone and claystone. Since loose surficial fill
and weathered Very Old Paralic Deposits are recommended for removal,
the underlying dense character of the on-site formational deposits, and the
lack of a shallow ground water table, it is our opinion that the potential for
liquefaction and seismic related settlement across the site is nil.
4.5.2 Lateral Spread
Empirical relationships have been derived (Youd et al., 1999) to estimate
the magnitude of lateral spread due to liquefaction. These relationships
include parameters such as earthquake magnitude, distance of the
earthquake from the site, slope height and angle, the thickness of
liquefiable soil, and gradation characteristics of the soil.
The susceptibility to earthquake-induced lateral spread is considered to be
low for the site because of the low susceptibility to liquefaction and
relatively level ground surface in the site vicinity.
4.5.3 Tsunamis and Seiches
Based on a site elevation of approximately 200 feet msl, and the distance
the site is located from the Pacific coastline, there is no potential for flood
damage to occur at the site from a tsunami or seiche.
4.6 Landslides
Several formations within the San Diego region are particularly prone to
landsliding. These formations generally have high clay content and mobilize
when they become saturated with water. Other factors, such as steeply dipping
bedding that project out of the face of the slope and/or the presence of fracture
planes, will also increase the potential for landsliding.
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No landslides or indications of deep-seated landsliding were indicated at the site
during our field exploration or our review of available geologic literature,
topographic maps, and stereoscopic aerial photographs. Furthermore, our field
explorations indicate the site is generally underlain by favorable oriented geologic
structure, consisting of sandstone, claystone, and siltstone. Therefore, the
potential for significant landslides or large-scale slope instability at the site is
considered low.
4. 7 Flood Hazard
According to a Federal Emergency Management Agency (FEMA) flood insurance
rate map (FEMA, 2012); the site is not located within a floodplain. Based on our
review of topographic maps, the site is not located downstream of a dam or
within a dam inundation area. Based on this review and our site reconnaissance,
the potential for flooding of the site is considered very low.
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5.0 CONCLUSIONS
Based on the results of our geotechnical investigation of the site, it is our opinion that
the proposed residential development is feasible from a geotechnical standpoint,
provided the following conclusions and recommendations are incorporated into the
project plans and specifications.
• Generally, loose soils having depths of up to approximately 1 to 10 feet locally
underlie the site and are considered compressible. Therefore, these soils are not
considered suitable for the support of structural loads or the support of engineered
fill soils and site improvements in their present condition. Section 6.1.2 of this report
provides specific recommendations regarding mitigation of these soil materials.
• The mapped MCEG peak ground acceleration (PGA) is 0.432g for the site, and for
site Class D, the mapped peak ground acceleration, adjusted for Site Class effects
(PGAM) is 0.461g.
• Based on the results of our subsurface explorations and our experience with similar
projects in the site area, we anticipate regional ground water to be at a depth of 200
feet or more. Therefore, ground water is not anticipated to be a constraint during site
construction, and we do not anticipate that temporary dewatering will be necessary.
• The underlying Very Old Paralic Deposits and Santiago Formation are not subject to
liquefaction based on their age, generally dense character, and the lack of a shallow
ground water table.
• The cut slope adjacent to Lot 4 will likely require a buttress/replacement fill to
stabilize slope wash material.
• Due to the lack of adverse geologic conditions, landsliding and mass movement is
considered to be unlikely. However, cut slopes should be evaluated during site
grading to verify slope bedding is as anticipated.
• Based on the results of our subsurface exploration, we anticipate that the onsite
materials should be generally rippable with conventional heavy-duty earthwork
equipment. The existing onsite soils are suitable for reuse as engineered fill provided
they are relatively free of organic material, debris, and rock fragments larger than 6
inches in maximum dimension. In addition, unknown items such as buried concrete
footings left from previous site development should be anticipated.
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• Based on laboratory testing and visual classification, materials derived from the on-
site soil materials possess a low to medium expansion potential.
• Although Leighton does not practice corrosion engineering, laboratory test results
indicate the soils present on the site have a negligible potential for sulfate attack on
normal concrete. However, the onsite soils are considered to be moderately
corrosive to buried uncoated ferrous metals.
• It should be noted that the existing cribwall at the north east property line may be
impacted by the proposed improvements and require remedial grading activities.
• The existing onsite soils were found to have a very low permeability and are not
considered suitable for storm water management strategies that utilize infiltration.
Additional investigation regarding the infiltration characteristics of the site soils will
be required before recommendations for the use of infiltration type LID devices can
be provided. The proposed infiltration basins should be lined with a 30-mil HOPE
liner to prevent lateral migration of storm water. In addition, subsurface
improvements down gradient could be affected by some proposed LID measures
and should therefore be fully evaluated before being considered.
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6.1
6.0 RECOMMENDATIONS
Earthwork
We anticipate that earthwork at the site will consist of site preparation, shallow
excavation and fill operations. We recommend that earthwork on the site be
performed in accordance with the following recommendations and the General
Earthwork and Grading Specifications for Rough Grading included in Appendix
D. In case of conflict, the following recommendations supersede those in
Appendix D.
6.1.1 Site Preparation
Prior to grading, all areas to receive structural fill, engineered structures,
or hardscape should be cleared of surface and subsurface obstructions,
including any existing debris and undocumented, loose, compressible, or
unsuitable soils, and stripped of vegetation. Removed vegetation and
debris should be properly disposed off site. All areas to receive fill and/or
other surface improvements should be scarified to a minimum depth of 8
inches, brought to optimum or above-optimum moisture conditions, and
recompacted to at least 90 percent relative compaction based on ASTM
Test Method D1557.
6.1.2 Removal of Compressible Soils
Potentially compressible undocumented fill soils, colluvium, slope wash
deposits, and weathered Paralic Deposits at the site may settle as a result
of wetting or settle under the surcharge of engineered fill and/or structural
loads supported on shallow foundations. Therefore, remedial grading is
recommended across the entire site to remove undocumented fill,
colluvium, slope wash deposits, and weathered Paralic Deposits. These
soils should be removed to undisturbed Paralic Deposits ("Formation")
and/or Santiago Formation and replaced as moisture conditioned
engineered fill. In general, removal depths will range from 2 to 10 feet
below the existing ground surface across the site. The removal depths
should extend to a depth of at least 4 feet below finished building pad
grade. The lateral limits of the removal bottom should extend at least 5
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feet beyond the foundation limits. The bottom of all removals should be
evaluated by a Certified Engineering Geologist to confirm conditions are
as anticipated.
In general, the soil that is removed may be reused and placed as
engineered fill provided the material is moisture conditioned to at least 2
percent above optimum moisture content, and then recompacted prior to
additional fill placement or construction. Soil with an expansion index
greater than 70 should not be used within 5 feet of finish grade in the
building pad. The actual depth and extent of the required removals should
be confirmed during grading operations by the geotechnical consultant.
6.1.3 Cut/Fill Transition Mitigation
Our review of the preliminary grading plans indicates that several lots may
result in the creation of cut/fill transitions. The introduction of materials (fill
compared to native sandstone) having differing permeability and density
into the site may create a condition where surface infiltration of water may
accumulate below grade. As such, overexcavation of the Paralic Deposits
should be sloped at 1 percent toward the streets or deeper fills. To mitigate
the impact of the underlying cut/fill transition condition beneath possible
structures that are planned across existing or future cut/fill transitions, the
cut portion should be over-excavated to at least 3 feet below the bottoms of
proposed foundations. The overexcavation should laterally extend at least 5
feet beyond the building pad area and all associated settlement-sensitive
structures. The over-excavated material should be replaced with properly
compacted fill. Maximum to minimum fill thickness within a given lot should
not exceed ratio of 3:1. As such, deeper over excavation will be necessary
for fill lots with maximum fills in excess of approximately 9 feet. Final
overexcavation depths should be determined and documented in the field
based on site conditions.
6.1.4 Excavations and Oversize Material
Excavations of the onsite materials may generally be accomplished with
conventional heavy-duty earthwork equipment. Due to the generally friable
nature of the fill and Paralic Deposits, temporary excavations, such as
utility trenches with vertical sides, may slough over time.
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In accordance with OSHA requirements, excavations deeper than 5 feet
should be shored or be laid back if workers are to enter such excavations.
Temporary sloping gradients should be determined in the field by a
"competent person" as defined by OSHA. For preliminary planning,
sloping of fill soils at 1 :1 (horizontal to vertical) may be assumed.
Excavations supporting structures or greater than 20 feet in height will
require an alternative sloping plan or shoring plan prepared by a California
registered civil engineer.
6.1.5 Engineered Fill
In areas proposed to receive engineered fill, the existing upper 8 inches of
subgrade soils should be scarified then moisture conditioned to moisture
content at or above the optimum content and compacted to 90 percent or
more of the maximum laboratory dry density, as evaluated by ASTM D
1557. Soil materials utilized as fill should be free of oversized rock,
organic materials, and deleterious debris. Rocks greater than 6 inches in
diameter should not be placed within 2 feet of finished grade. Fill should
be moisture conditioned to at least 2 percent above the optimum moisture
content and compacted to 90 percent or more relative compaction, in
accordance with ASTM D 1557. Although the optimum lift thickness for fill
soils will be dependent on the type of compaction equipment utilized, fill
should generally be placed in uniform lifts not exceeding approximately 8
inches in loose thickness.
In vehicle pavement areas, the upper 12 inches of subgrade soils should
be scarified then moisture conditioned to a moisture content above
optimum content and compacted to 95 percent or more of the maximum
laboratory dry density, as evaluated by ASTM D 1557.
Placement and compaction of fill should be performed in general
accordance with current City of Carlsbad grading ordinances, California
Building Code, sound construction practice, these recommendations and
the General Earthwork and Grading Specifications for Rough Grading
presented in Appendix D.
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6.1.6 Import Soils
If import soils are necessary to bring the site up to the proposed grades,
these soils should be granular in nature, environmentally clean, have an
expansion index less than 50 (per ASTM Test Method D4829) and have a
low corrosion impact to the proposed improvements. Import soils and/or
the borrow site location should be evaluated by the geotechnical
consultant prior to import. The contractor should provide evidence that all
import materials comply with DTSC requirements for import materials.
6.1.7 Expansive Soils and Selective Grading
Based on our laboratory testing and observations, we anticipate the onsite
soil materials possess a low to medium expansion potential (Appendix C).
Should an abundance of medium to highly expansive · materials be
encountered, selective grading may need to be performed, such as
placing these materials in the deeper portions of the planned fill areas. In
addition, to accommodate conventional foundation design, the upper 5
feet of materials within the building pad and 5 feet outside the limits of the
building foundation should have a very low to low expansion potential
(E1<70).
6.1.8 Buttress/Replacement Fill
Based on our subsurface exploration (Appendix B), we anticipate the cut
slope in the north western portion of the site adjacent to Lot 4 may be
surficially unstable and may require the construction of buttress or
replacement fill. The replacement fill key should be constructed a
minimum of 15 feet wide, at least 2 feet below the toe-of-slope grade, and
have a minimum 2 percent into-the-slope inclination. The approximate
location of the replacement fill key is presented on the Geotechnical Map
(Plate 1.) A typical detail for stability fill construction is provided in the
attached General Earthwork and Grading Specifications (Appendix D).
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6.2 Foundation and Slab Considerations
At the time of drafting this report, building loads were not known. However, based
on our understanding of the project, the proposed residential buildings may be
constructed with conventional foundations or post-tensioned foundations. In
general foundations and slabs should be designed in accordance with structural
considerations and the following recommendations. The foundation
recommendations below assume that the all building foundations will be
underlain by properly compacted fill.
6.2.1 Conventional Foundations
Conventionally reinforced foundations should be designed and constructed
in accordance with the recommendations contained in Table 3 based on a
very low to low expansion potential. Residential structures placed on deep fill
areas (considered to be greater than 40 feet in depth), underlain by
differential fill thicknesses of 20 or more feet, and/or having moderate to
highly expansive soils (an expansive potential greater than 51) at finish
grade should be constructed with a post-tension foundation (as indicated in
Section 6.2.5) instead of a conventional reinforced foundation.
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Table 3
Minimum Foundation and Slab DesiQn Recommendations For Conventional Reinforced Foundations
Design Criteria
Minimal Fill Thickness, Minimal Fill Differential, and a Very Low to
Low Expansion Potential (an Expansion Potential less than 50)
I-Story Footings All footings 12 inches deep. Reinforcement for continuous footings: two
(See Note 1) No. 5 bar top and bottom.
2-Story Footings All footings 18 inches deep. Reinforcement for continuous footings: two
(See Note 1) No. 5 bar top and bottom.
Minimum Footing Width Continuous: 12 inches for 1-story
Continuous: 15 inches for 2-story
Isolated column: 24 inches (18 inches deep minimum)
Garage Door Grade Beam A grade beam 12 inches wide and 18 inches deep
(SeeNote2) should be provided across the garage entrance.
Living Area Floor Slabs Minimum 5 inch thick slab with No. 3 bars@ 18 inches on center, each
(See Notes 3, 4 and 6) way (at mid-height) on 2 inches clean sand over moisture barrier over 2
inches clean sand.
Garage Floor Slabs Minimum 5 inch thick concrete slab with No. 3 bars@ 18 inches on center,
(See Notes 4, 5 and 6) each way (at mid-height) on 2 inches sand base over moisture barrier on
pad. Slab should be quarter-sawn.
Presoaking of Living Area 120 percent of the optimum moisture content to a depth of 12 inches.
and Garage Slabs (see note)
Allowable Bearing Capacity 2,000 pounds per square foot (one-third increase for short term loading)
Expected Foundation Deflection: 1/2 inch in 50 feet
Notes:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Depth of interior or exterior footing to be measured from lowest adjacent finish grade or drainage
swale flowline elevation.
The base of the grade beam should be at the same elevation as that of the adjoining footings.
Living area slabs should be tied to the footings as directed by the structural engineer.
10-mil non-recycled plastic sheeting is acceptable. Equivalents are acceptable. All laps and
penetrations should be sealed.
Garage slabs should be isolated from stem wall footings with a minimum 3/8-inch expansion joint.
Sand base should have a Sand Equivalent of30 or greater (e.g. washed concrete sand).
Where the foundation is within 3 feet (horizontally) of adjacent drainage swales, the adjacent
footing should be embedded a minimum depth of 12 inches below the swale flow line.
The recommendations presented above assume that proper maintenance irrigation and drainage
are maintained around the structure.
The vapor barrier recommended in Table 2 should be sealed at all
penetrations and laps. Moisture vapor transmission may be additionally
reduced by use of concrete additives. Moisture barriers can retard but not
eliminate moisture vapor movement from the underlying soils up through the
slabs. We recommend that the floor covering installer test the moisture vapor
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flux rate prior to attempting applications of the flooring. "Breathable" floor
coverings should be considered if the vapor flux rates are high. A slipsheet
or equivalent should be utilized above the concrete slab if crack-sensitive
floor coverings (such as ceramic tiles, etc.) are to be placed directly on the
concrete slab.
Our experience indicates that use of reinforcement in slabs and foundations
will generally reduce the potential for drying and shrinkage cracking .
However, some cracking should be expected as the concrete cures. Minor
cracking is considered normal; in addition, it is often aggravated by a high
water content, high concrete temperature at the time of placement, small
nominal aggregate size, and rapid moisture loss due to hot, dry and/or windy
weather conditions during placement and curing. Cracking due to
temperature and moisture fluctuations can also be expected. The use of low
water content concrete can reduce the potential for shrinkage cracking.
The slab subgrade soils underlying the conventional foundation systems
should be presoaked as indicated in Section 6.2.4 prior to placement of the
moisture barrier and slab concrete.
6.2.2 Foundation Setback
We recommend a minimum horizontal setback distance from the face of
slopes for all structural foundations, footings, and other settlement-
sensitive structures as indicated on the Table 4 below. The minimum
recommended setback distance from the face of a retaining wall is equal to
the height of the retaining wall. The distance is measured from the outside
bottom edge of the footing, horizontally to the slope or retaining wall face,
and is based on the slope or wall height. However, the foundation setback
distance may be revised by the geotechnical consultant on a case-by-case
basis if the geotechnical conditions are different than anticipated.
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Table 4
Minimum Foundation Setback from Slope Faces
Slope Height Setback
less than 5 feet 5 feet
5 to 15 feet ?feet
Please note that the soils within the structural setback area possess poor
lateral stability, and improvements (such as retaining walls, sidewalks,
fences, pavements, etc.) constructed within this setback area may be
subject to lateral movement and/or differential settlement. Potential distress
to such improvements may be mitigated by providing a deepened footing or
a grade beam foundation system to support the improvement.
In addition, open or backfilled utility trenches that parallel or nearly parallel
structure footings should not encroach within an imaginary 1: 1 (horizontal
to vertical) downward sloping line starting 9 inches above the bottom edge
of the footing and should also not be located closer than 18 inches from the
face of the footing. Deepened footings should meet the setbacks as
described above. Also, over-excavation should be accomplished such that
deepening of footings to accomplish the setback will not introduce a cut/fill
transition bearing condition.
Where pipes cross under footings, the footings should be specially
designed. Pipe sleeves should be provided where pipes cross through
footings or footing walls and sleeve clearances should provide for possible
footing settlement, but not less than 1 inch around the pipe.
6.2.3 Settlement
Fill depths between 3 and 13 feet are anticipated beneath the proposed
building foundations following final grading. For conventional footings, the
recommended allowable-bearing capacity is based on a maximum total
and differential static settlement of 3/4 inch and 1/2 inch, respectively.
Since settlements are a function of footing size and contact bearing
pressures, some differential settlement can be expected where a large
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differential loading condition exists. However for most cases, differential
settlements are considered unlikely to exceed 1/2 inch.
6.2.4 Moisture Conditioning
The slab subgrade soils underlying the foundation systems should be
presoaked in accordance with the recommendations presented in Table 5
prior to placement of the moisture barrier and slab concrete. The subgrade
soil moisture content should be checked by a representative of Leighton
prior to slab construction.
Presoaking or moisture conditioning may be achieved in a number of ways.
But based on our professional experience, we have found that minimizing
the moisture loss on pads that has been completed (by periodic wetting to
keep the upper portion of the pad from drying out) and/or berming the lot
and flooding for a short period of time (days to a few weeks) are some of
the more efficient ways to meet the presoaking recommendations. If
flooding is performed, a couple of days to let the upper portion of the pad
dry out and form a crust so equipment can be utilized should be
anticipated.
Table 5
Presoaking Recommendations Based on Finish Grade Soil Expansion
Potential
Expansion Potential PresoakinQ Recommendations
Very Low Near-optimum moisture content to a minimum
depth of 6 inches
Low 120 percent of the optimum moisture content to
a minimum depth of 12 inches below slab
subQrade
Medium 130 percent of the optimum moisture content to
a minimum depth of 18 inches below slab
subQrade
High 130 percent of the optimum moisture content to
a minimum depth of 24 inches below slab
subgrade
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6.2.5 Post-Tension Foundation Recommendations
As an alternative to the conventional foundations for the buildings, post-
tensioned foundations may be used. We recommend that post-tensioned
foundations be designed using the geotechnical parameters presented in
table below and criteria of the 2013 California Building Code and the Third
Edition of Post-Tension Institute Manual. A post-tensioned foundation
system designed and constructed in accordance with these
recommendations is expected to be structurally adequate for the support of
the buildings planned at the site provided our recommendations for surface
drainage and landscaping are carried out and maintained through the
design life of the project. Based on an evaluation of the depths of fill
beneath the building pads, the attached Table 6 presents the
recommended post-tension foundation category for residential buildings for
this site.
Table 6
Post-Tensioned Foundation Design Recommendations
Catego!Y I Catego!Y II Catego!Y Ill Very Low to Medium High Low Design Criteria Expansion Expansion Expansion
Potential Potential Potential (El 50 to 90) (El 90 to 130) (El Oto 50)
Edge Center 9.0 feet 8.3 feet 7.0 feet
Moisture Lift:
Variation, Edge 4.8 feet 4.2 feet 3.7 feet em Lift:
Center 0.46 inches 0.75 inches 1.09 inches
Differential Lift:
Swell, Ym Edge 0.65 inches 1.09 inches 1.65 inches Lift:
Perimeter Footing 18inches 24inches 30inches Depth:
Allowable Bearing 2,000 psf
Capacity
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The post-tensioned (PT) foundation and slab should also be designed in
accordance with structural considerations. For a ribbed PT foundation, the
concrete slabs section should be at least 5 inches thick. Continuous
footings (ribs or thickened edges) with a minimum width of 12 inches and a
minimum depth of 12 inches below lowest adjacent soil grade may be
designed for a maximum allowable bearing pressure of 2,000 pounds per
square foot. For a uniform thickness "mat" PT foundation, the perimeter cut
off wall should be at least 8 inches below the lowest adjacent grade.
However, note that where a foundation footing or perimeter cut off wall is
within 3 feet (horizontally) of adjacent drainage swales, the adjacent footing
should be embedded a minimum depth of 12 inches below the swale flow
line. The allowable bearing capacity may be increased by one-third for
short-term loading. The slab subgrade soils should be presoaked in
accordance with the recommendation presented in Table 5 above prior to
placement of the moisture barrier.
The slab should be underlain by a moisture barrier as discussed in
Section 6.2.1 above. Note that moisture barriers can retard, but not
eliminate moisture vapor movement from the underlying soils up through
the slabs. We recommend that the floor covering installer test the moisture
vapor flux rate prior to attempting applications of the flooring. "Breathable"
floor coverings should be considered if the vapor flux rates are high. A slip-
sheet or equivalent should be utilized above the concrete slab if crack-
sensitive floor coverings (such as ceramic tiles, etc.) are to be placed
directly on the concrete slab. Additional guidance is provided in ACI
Publications 302.1 R-04 Guide for Concrete Floor and Slab Construction
and 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive
Floor Materials.
6.3 Lateral Earth Pressures and Retaining Wall Design
Table 7 presents the lateral earth pressure values for level or sloping backfill for
walls backfilled with and bearing against fully drained soils of very low to low
expansion potential (less than 50 per ASTM D4829).
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Table 7
Static Equivalent Fluid Weight (pcf)
Conditions Level 2:1 Slope
Active 35 55
At-Rest 55 65
Passive 350 150
(Maximum of 3 ksf) (sloping down)
Walls up to 10 feet in height should be designed for the applicable pressure
values provided above. If conditions other than those covered herein are
anticipated, the equivalent fluid pressure values should be provided on an
individual case-by-case basis by the geotechnical engineer. A surcharge load for
a restrained or unrestrained wall resulting from automobile traffic may be
assumed to be equivalent to a uniform lateral pressure of 75 psf which is in
addition to the equivalent fluid pressure given above. For other uniform
surcharge loads, a uniform pressure equal to 0.35q should be applied to the wall.
The wall pressures assume walls are backfilled with free draining materials and
water is not allowed to accumulate behind walls. A typical drainage design is
contained in Appendix D. Wall backfill should be compacted by mechanical
methods to at least 90 percent relative compaction (based on ASTM D1557). If
foundations are planned over the backfill, the backfill should be compacted to 95
percent. Wall footings should be designed in accordance with the foundation
design recommendations and reinforced in accordance with structural
considerations. For all retaining walls, we recommend a minimum horizontal
distance from the outside base of the footing to daylight as outlined in
Section 6.2.2.
Lateral soil resistance developed against lateral structural movement can be
obtained from the passive pressure value provided above. Further, for sliding
resistance, the friction coefficient of 0.35 may be used at the concrete and soil
interface. These values may be increased by one-third when considering loads of
short duration including wind or seismic loads. The total resistance may be taken
as the sum of the frictional and passive resistance provided that the passive
portion does not exceed two-thirds of the total resistance.
To account for potential redistribution of forces during a seismic event, retaining
walls providing lateral support where exterior grades on opposites sides differ by
more than 6 feet fall under the requirements of 2013 CBC Section 1803.5.12
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and/or ASCE 7-10 Section 15.6.1 and should also be analyzed for seismic
loading. For that analysis, an additional uniform lateral seismic force of 8H should
be considered for the design of the retaining walls with level backfill, where H is
the height of the wall. This value should be increased by 150% for restrained
walls.
6.4 Geochemical Considerations
6.5
6.6
Concrete in direct contact with soil or water that contains a high concentration of
soluble sulfates can be subject to chemical deterioration commonly known as
"sulfate attack." Soluble sulfate results (Appendix C) indicated negligible soluble
sulfate content. We recommend that concrete in contact with earth materials be
designed in accordance with Section 4 of ACI 318-11 (ACI, 2011 ).
Based on our experience in the site vicinity and laboratory tests, the site soils
have a moderately corrosion potential to buried uncoated metal conduits. We
recommend measures to mitigate corrosion be implemented during design and
construction.
Concrete Flatwork
Concrete sidewalks and other flatwork (including construction joints) should be
designed by the project civil engineer and should have a minimum thickness of 4
inches. For all concrete flatwork, the upper 12 inches of subgrade soils should be
moisture conditioned to at least 3 percent above optimum moisture content and
compacted to at least 90 percent relative compaction based on ASTM Test
Method D1557 prior to the concrete placement.
Preliminary Pavement Design
The preliminary pavement section design below is based on an assumed Traffic
Index (Tl), our visual classification of the subject site soils, experience with other
projects in the area, and our limited laboratory testing. Actual pavement
recommendations should be based on R-value tests performed on bulk samples
of the soils that are exposed at the finished subgrade elevations across the site
at the completion of the mass grading operations. Flexible pavement sections
have been evaluated in general accordance with the Caltrans method for flexible
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pavement design. Based on an assumed R-value of 10, preliminary pavement
sections for planning purposes is given in Table 8 below:
Table 8
Preliminary Pavement Sections
Assumed Traffic Asphalt Concrete Aggregate Base
Index (Tl) (inches) (inches)
4.5 4.0 5.0
5.0 4.0 6.0
6.0 4.0 13.0
Prior to placement of the aggregate base, the upper 12 inches of subgrade soils
should be scarified, moisture-conditioned to at least optimum moisture content and
compacted to a minimum 95 percent relative compaction based on American
Standard of Testing and Materials (ASTM) Test Method D1557.
Class 2 Aggregate Base or Crushed Aggregate Base should then be placed and
compacted at a minimum 95 percent relative compaction in accordance with ASTM
Test Method D1557. The aggregate base material (AB) should be a maximum of 6
inches thick below the curb and gutter and extend a minimum of 6 inches behind the
back of the curb. The AB should conform to and placed in accordance with the
approved grading plans, and latest revision of the Standard Specifications Public
Works Construction (Greenback).
The Asphalt Concrete (AC) material should conform to Caltrans Standard
Specifications, Sections 39 and 92, with a Performance Grade (PG) of 64-10, and
the City of Carlsbad requirements. The placement of the AC should be in
accordance with the approved grading plans, Section 203-6 of the "Greenback"
Standard Specifications for Public Works Construction, and the City of Carlsbad
requirements. AC sections greater than 3-inches thick, should be placed in two
lifts. The 1st lift should be a 2-inch minimum base course consisting of a 3/4-inch
maximum coarse aggregate. The 2nd lift should be a 2-inch minimum surface
capping course consisting of a 1/2-inch maximum coarse aggregate. No single lift
shall be greater than 3 inches.
If pavement areas are adjacent to heavily watered landscaping areas, we
recommend some measures of moisture control be taken to prevent the subgrade
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
soils from becoming saturated. It is recommended that the concrete curbing,
separating the landscaping area from the pavement, extend below the aggregate
_1 base to help seal the ends of the sections where heavy landscape watering may
have access to the aggregate base. Concrete swales should be designed if
asphalt pavement is used for drainage of surface waters.
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6.7 Control of Ground Water and Surface Waters
Regarding Low Impact Development (LID) measures, we are of the opinion that
bioswales, infiltration basins, and other onsite storm water retention and infiltration
systems can potentially create adverse perched ground water conditions both on-
site and off-site. Therefore, given the site geologic conditions, impermeable
subsurface material, and project type, infiltration type LID measures are not
considered to be appropriate for this site and project. 30 mil HOPE Liners should
be used where detention areas are proposed near slopes or retaining walls, near
buildings, or over utilities.
Surface drainage should be controlled at all times and carefully taken into
consideration during precise grading, landscaping, and construction of site
improvements. Positive drainage (e.g., roof gutters, downspouts, area drains, etc.)
should be provided to direct surface water away from structures and improvements
and towards the street or suitable drainage devices. Ponding of water adjacent to
structures or pavements should be avoided. Roof gutters, downspouts, and area
drains should be aligned so as to transport surface water to a minimum distance of
5 feet away from structures. The performance of structural foundations is
dependent upon maintaining adequate surface drainage away from structures.
Water should be transported off the site in approved drainage devices or
unobstructed swales. We recommend a minimum flow gradient for unpaved
drainage within 5 feet of structures of 2 percent sloping away.
The impact of heavy irrigation or inadequate runoff gradient can create perched
water conditions, resulting in seepage or shallow ground water conditions where
previously none existed. Maintaining adequate surface drainage and controlled
irrigation will significantly reduce the potential for nuisance-type moisture
problems. To reduce differential earth movements such as heaving and shrinkage
due to the change in moisture content of foundation soils, which may cause
distress to a structure and improvements, moisture content of the soils surrounding
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the structure should be kept as relatively constant as possible. Below grade
planters should not be situated adjacent to structures or pavements unless
provisions for drainage such as catch basins and drains are made.
All area drain inlets should be maintained and kept clear of debris in order to
function properly. In addition, landscaping should not cause any obstruction to site
drainage. Rerouting of drainage patterns and/or installation of area drains should
be performed, if necessary, by a qualified civil engineer or a landscape architect.
All area drain inlets should be maintained and kept clear of debris in order to
J function properly. In addition, landscaping should not cause any obstruction to site
drainage. Rerouting of drainage patterns and/or installation of area drains should
be performed, if necessary, by a qualified civil engineer or a landscape architect.
6.8 Construction Observation
The recommendations provided in this report are based on preliminary design
information and subsurface conditions disclosed by widely spaced excavations.
·· J The interpolated subsurface conditions should be checked by Leighton and
Associates, Inc. in the field during construction. Construction observation of all
onsite excavations and field density testing of all compacted fill should be
performed by a representative of this office. We recommend that all excavations
be mapped by the geotechnical consultant during grading to determine if any
potentially adverse geologic conditions exist at the site.
6.9 Plan Review
Final project grading and foundation plans should be reviewed by Leighton and
Associates as part of the design development process to ensure that
recommendations in this report are incorporated in project plans.
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7.0 LIMITATIONS
The conclusions and recommendations presented in this report are based in part upon
data that were obtained from a limited number of observations, site visits, excavations,
samples, and tests. Such information is by necessity incomplete. The nature of many
sites is such that differing geotechnical or geological conditions can occur within small
distances and under varying climatic conditions. Changes in subsurface conditions can
and do occur over time. Therefore, the findings, conclusions, and recommendations
presented in this report can be relied upon only if Leighton has the opportunity to
observe the subsurface conditions during grading and construction of the project, in
order to confirm that our preliminary findings are representative for the site .
33
Figure and Plates
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Project: 10690.002 Eng/Geel: BEV/MDJ
Scale :1 "= 2,000 ' Date : September 2014
Base Map: ESRI ArcGIS Online 2014
Thematic Information: Leighton
Autha: (mmurphy)
Map Saved as P :\draftir9110690'()02\GIS'<>f_2014-0!l-19\Figure1 .mxd on 91 19/2014 9:15:17 AM
SITE LOCATION MAP
2200 Afton Way
Carlsbad, California
Figure 1
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Appendix A
References
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
APPENDIX A
REFERENCES
California Geologic Survey (CGS), 2007, Fault Rupture Hazard Zones in California,
Special Publication No. 42, Revised 2007 (Interim Version).
California Building Standards Commission (CBSC), 2013, California Building Code,
Volumes 1 and 2.
FEMA, 2012, Flood Insurance Maps, Panel 1035 of 2375, dated May 16.
Jennings, C.W., 2010, Fault Activity Map of California and Adjacent Areas: California
Division of Mines and Geology, California Geologic Map Series, Map No. 6
Kennedy, M.P., and Tan, S.S., 2007, Geologic Map of the Oceanside Quadrangle,
California, California Geologic Survey, 1: 100,000 scale.
Kennedy, M.P. and Tan, S.S., 2005, Geologic Map of the San Diego 30' X 60'
Quadrangle, California Compiled by Michael P. Digital Preparation by Kelly R. Bovard,
Anne G. Garcia and Diane Burns, California Geological Survey.
Tan, S.S., and Kennedy, M.P, 1996, Geologic Maps of the Northwestern Part of San
Diego County, California, Plate 1, Scale 1 :24,000.
Treiman, J.A., 1993, The Rose Canyon Fault Zone, Southern California: California
Division of Mines and Geology, Open File Report 93-02, 45p.
United States Department of Agriculture, 1953, Aerial Photographs, Flight AXN-8M,
Numbers 75 and 76, scale approximately 1 :24,000, dated March 31.
A-1
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Appendix B
_! Test Pit and Boring Logs
LOG OF TRENCH: --"'I-"-J-1...__ __
Project Name: Afton Way. Logged by: Cl\/
ENGINEERING PROPERTIES
Project Number: 10690002 Elevation: 254 feet mean sea level
Equipment: Backhoe Location/Grid: . S011them Sample Moisture Density
GEOLOGIC uses
DATE: 6/12/14 DESCRIPTION: GEOLOGIC No. (%) (pcf}
ATTITUDES UNIT
COLLUVIUM Qc
@ 0-2': Silty SAND, brown, dry, loose; roots and rootlets, porous, fine to SM
medium grained, weakly cemented ,, I VERY OLD PARALIC DEPOSITS Qvop
! @ 2'-11 ': Silty SAND, orang-brown, dry, medium dense to very dense with SM B-1
depth; massive @
0'-4'
'
' i
i
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 2-4°NE TREND:
' I t I I !
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\ ..... \.\ I !
» f
I I l Total Depth = 11 Feet
I .. \) i No Ground Water Encountered
(1 ' ' Backfilled: 6/12/14
\ \ ;
1~\ I j
...
LOG OF TRENCH: _ _,T.,..-2.__ __ _
Project Name: Aftoa Way_ Logged by: RV
ENGINEERING PROPERTIES
Project Number: 1QB90 002 Elevation: 242 feet mean sea level
Equipment: . Backhoe . Location/Grid: Middle S011ib
GEOLOGIC uses Sample Moisture Density
DATE: 6/12/14 DESCRIPTION: GEOLOGIC No. (%) (pcf)
ATIITUDES UNIT
''
COLLUVIUM Qc
@ 0-2': Silty SAND, dark brown, dry, loose SM 8-1
Qvop @
VERY OLD PARALIC DEPOSITS 0'-4'
@ 2'-4': Silty SAND, orange brown to reddish brown, dry, medium dense to SM
dense with depth; massive, grades into clayey sand at 4 feet
TsA 8-2
§ANTIAGO FORMATION @
8'-12'
@4'-12': Clayey SANDSTONE, light brown, moist, very stiff, massive, caliche SC
strings along fractures
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 2-4°NE TREND:
I
I I ~·. ;1 l I I ______-·-
i -----1 ..... ! )""·----) l... r i <, . (, • \ 2 J ' , , , l I j
I
W,'/.'~
\ ' 'j ! l I
,.,,,,,,..,.,.,..
i' ~· <I . I
I " ' ' ' '' ' ' ' ' ! l ·.·.··· .. ·1,/y /Ii
! \ ·r. /r'I'' ' I
:> .. .. .,.,,_ ~ \ ...... · /·.···< ,,.f' I i
\. / .. · /i;' .. / ·/" .·' I , / / . .. / r • I , \;: ' ,/ ' ·1 . /.. i ,, / / / i i
' ~,/: --,4---', ' ;,~ ! --+'""''
/' / /.f' 1~ >"" .. / I.,.""' // / .... ' /" i Total Depth= 12 Feet . ,. , .· / I i ,/, ;/ /.f'/ f' .' No Ground Water Encountered ,1 f ... ,,"/ j I I 'K /''.. f/' .·· Backfilled: 6/12/14
/' ,,-/'i / !
1 1 ~1~~/ I i
! !
Project Name: Afton Way Logged by: __ __l,Llt___ _________ _
Project Number: . 10690 002 Elevation: 256 feet mean sea level
Equipment: Backhoe Location/Grid: Middle West
GEOLOGIC
ATTITUDES
1ATE: 6/12/14 DESCRIPTION:
COLLUVIUM
@0-2': Silty SAND, dark brown, dry, loose; roots and rootlets, porous
VERY OLD PARALIC DEPOSITS
@ 2'-7': Silty SAND, reddish brown, dry, dense
@ 7': Gravel lense
@ 7'-12': Silty SAND, orange-brown, dry to moist, very dense
GEOLOGI
UNIT
Qc
Qvop
LOG OF TRENCH: _....lI~-31o1.--__ _
ENGINEERING PROPERTIES
uses ! Sample
No.
SM
SM
B-1
@
2'-3'
Moisture
(%}
Density
(pcf)
GRAPHICAL REPRESENTATION: SCALE: 1 »=5' SURFACE SLOPE: 2-3°NE TREND:
·-·--·,,.,.,.,.,..,.,.»
Total Depth= 12 Feet
No Ground Water Encountered
Backfilled: 6/12/14
L-L_ L -,_
LOG OF TRENCH: _ _..I.....,-4......._ __
Project Name: Afton Way Logged by: BY
ENGINEERING PROPERTIES Project Number: _ ..... 1..,.0fi.,..9-0....,..,00,,..2...,_,. ______ _ Elevation: 254 feet mean sea level
Equipment: Backhoe
GE
ATTI . TE: 6/12/14
Location/Grid: ----S .... acu.1..,1th.,,e..,r"'n.__ __________ _
DESCRIPTION:
GEOLOGIC I uses I sample
UNIT No .
Moisture I Density
(%) I {pcf)
COLLUVIUM
@ 0-4': Silty SAND, brown, dry, loose, roots and rootlets
VERY OLD PARALIC DEPOSITS
@ 4'-8': Silty SAND, orange-brown, dry, dense, massive
@ 8'-1 O': Becomes very dense
GRAPHICAL REPRESENTATION: SCALE: 1 "=5'
QC
I I SM
Qvop
I
SM
SURFACE SLOPE: 1-2°NE TREND:
<-»>'""""'"""''------------!-----1
I '
I ~ 1 ,
! ' ~ \ ' <(' ! i\--_-\ . I , , ! -• I \
I ' '--,. . t ( •
i-------I_ ~ I J, .... 4-, ) __ '_ i Total Dep: ;!~;:~~ountered
' ' .. rl --,r·· -_--l No Gkfirollue"d· 6/12/14 I ·.: eac, ·
" -~
-/
/
j \ \~ . \ .
\,-{ \ '
t -"-i t \lj_
L
LOG OF TRENCH: I-5 .....
Project Name: Afton Way Logged by: _____ ..._w.v........ __________ _
Pr~ectNumber. ~-1"0~6™9~0~PwP~2~~--~~~~~ Elevation: 264 feet mean sea level
ENGINEERING PROPERTIES
Equipment: Backhoe
GEOLOGIC
ATTITUDES E:v6/12/14
Location/Grid: S011tbem J· sample I Moisture
uses . No. (%) DESCRIPTION:
Density
(pcf)
ARTIFICIAL FILL-undocumented Afu
@ 0-2.5': Silty SAND, brown, dry, loose SM I 8·1
@
SLOPE WASH Qsw 4'-6'
SC
@ 2.5'-9': Clayey SAND, grayish-brown, moist, loose I
SANTIAGO FORMATION Tsa B-2
@
@ 9'-12': Silty CLAYSTONE, olive-gray to light brown, moist, medium stiff CL ! 9'-10'
PHICAL REPRESENTATION; SCALE: 1"=5' SURFACE SLOPE: 0-1°NE TREND:
/
Total Depth = 12 Feet
No Ground Water Encountered
Backfilled: 6/12114
L ~-
Project Name: Afton Way Logged by: __ ...,..wx.._ __________ _
Project Number: _....,;1..,o~aa...,o .... ...,oa .... 2.__-__ Elevation: 224 feet mean sea level
Equipment: 6ac:ld1ae Location/Grid: _ __.s..,0.,..1 ... it,.,.he.,..rn....._ __________ _
GEOLOGIC
ATTITUDES l DATE: 6/12/14 DESCRIPTION:
ARTIFICIAL FILL:.:undocumented
@0-10': Sandy CLAY, brown to yellowish brown, moist, loose to stiff with
depth; trash 2 6'; asphalt debris at 8'
1. SANTIAGO FORMATION
@ 10'-12': Sandy CLAYSTONE, light brown, moist, stiff to very stiff
Tsa
LOG OF TRENCH: _ _.I1;.:::-6,.,._ __ _
ENGINEERING PROPERTIES
uses I Sample I Moisture J Density
No. (%) (pcf)
CL B-1
@
0'-6'
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 5-8°NE TREND:
-k----------'1------·~; .,-,--------< ------,---~---,,,~
------
-------·""=r --/ +---~~,,,__-------
Total Depth= 12 Feet
No Ground Water Encountered
Backfilled: 6/12/14