HomeMy WebLinkAboutCT 05-14; La Costa Oaks Neighborhood 3.1; La Costa Oaks North Neighborhood 3.1; 2010-08-19Amendment No. 1 to Storm Water Management Plan
For
La Costa Oaks Neighborhood 3.1, PUD 05-11(8)
August 19, 2010
Introduction:
This Storm Water Management Plan Amendment has been prepared for Standard Pacific to accompany
application for a Planned Development Permit Amendment allowing construction of 80 homes on existing
single family lots La Costa Oaks North, Neighborhood 3.1 "the project". The application has been filed and
assigned Planned Development Permit Amendment No. PUD 05-11(B) and will cover lots previously subdivided
by Carlsbad Tract CT 05-l#/The completed Storm Water Standards Questionnaire has identified the project as
a Priority Development Project (see Appendix A)
Project Setting:
Currently the site is fully graded and has partial improvements installed per approved Drawing No.'s 446-4A
and 446-4 respectively. All post-construction Treatment Control BMP's for this Neighborhood are currently in
place and operational per the City Dwg. No. 446-4 and as approved in the underlying SWMP for La Costa Oaks
North Neighborhood 3.1 & 3.3-3.5, which also identifies Pollutants-of-Concern and Selection of Treatment
Control BMP's for those activities. This report addendum covers construction on residential lots and therefore
provides recommendations for treatment measures within those lots to augment previously approved and
installed measures for the grading and public improvement plans.
Hydromodification:
Grading for the lots and streets is complete, and therefore the requirements for Hydromodification do not ^>^
apply. See footnote 3 on page 17 of the SWRCB order. ^^
Drainage Study: ^**
Drainage Study for La Costa Oaks North Neighborhood 3.1 & 3.3-3 5 as referenced below is approved and is on ^^V
file at the City. I
Integrated Low Impact Development (LID): ^^^
Per City of Carlsbad SUSMP, Section 4, LID Design Guide, there are four conceptual LID Strategies for managing
runoff. .-7^
1. Optimize the Site Layout '-^r •»2. Use of Pervious Surfaces ^w
3. Dispersion of Runoff ^^
4. Integrated Management Practices * ^"
Combinations of these strategies are recommended to provide multiple, complementary benefits to a project. $-&
LO
surfaces include the construction of front and rear yard turf areas in conjunction with landscape areas. Typical £ *fc^t^y
locations of proposed pervious areas for each building type can be seen in Appendix B.
^^
Addendum in SWMPfoi 1.1 foM.i D.iks Noith \oigh ? P,ip,f 1
net.:
Dispersion of Runoff is another proposed strategy incorporated on every lot within this project. Impervious roof
area will convey and disperse runoff at multiple locations around the perimeter of the building to adjacent
pervious areas. This project proposes the use of roof drains with downspouts. The roof downspouts shall not be
tied into an underground drainage system, but be discharged into adjacent landscape areas after the erosive
force is dissipated by a splash block. Other proposed impervious hardscape features shall also direct runoff to
pervious areas to the maximum extent practicable. Typical impervious roof and hardscape areas for each
building type in relation to adjacent pervious areas that will accept anticipated runoff can also be seen in
Appendix B.
Optimize the Site Layout was considered in the initial project planning resulting in the preservation of
significant open space within the Master Plan. At this point, no further optimization is feasible due to the
recorded final map as well as grading and improvements installed to date.
Integrated Management Practices are also not a recommended strategy as most IMP's use water infiltration
into the soil, a method that is not recommended by the Geotechnical Engineer (See Letter attached as
Appendix C). The site soils are identified as group D and any installation of infiltration measures on the lot
would require a sub-drain, as directed in the Carlsbad SUSMP. Unavailability for connection of the sub-drain
also precludes infiltration use. The only IMP option not requiring infiltration is a Vegetated Roof. Currently a
feasible technology for treating single family homes with vegetated roof systems is not available, so this also is
not a viable IMP option.
Based on the above, we find that the only practicable opportunity to add LID strategies is to implement a
combination of Dispersion of Runoff and Use of Pervious Surfaces strategies on each lot in an effort to treat
runoff to the Maximum Extent Practicable.
References:
Storm Water Management Plan for La Costa Oaks North Neighborhood 3.1 & 3.3-3.5, Approved 7/12/2007
Rough Grading Plan, Dwg. 446-4A, for La Costa Oaks North Neighborhood 3.1, Approved 7/12/2007
Improvement Plan, Dwg. 446-4, for La Costa Oaks North Neighborhood 3.1., Approved 7/12/2007
Drainage Study for La Costa Oaks North Neighborhood 3.1 & 3.3-3.5, Approved 7/12/2007
Final Map No. 15595 for City of Carlsbad Tract 05-14, La Costa Oaks North Neighborhood 3.1, Rec 8/22/2007
State Water Resource Control Board Order no. R9-20007-0001 dated January 24, 2007
Addendum to SWMP for l,a Costa Oaks North Neigh. 3 Page 2
DECLARATION OF RESPONSIBLE CHARGE
I HEREBY DECLARE THAT I AM THE ENGINEER OF WORK FOR THIS PROJECT, THAT I HAVE EXERCISED
RESPONSIBLE CHANGE OVER THE DESIGN OF THE PROJECT AS DEFINED IN SECTION 6703 OF THE BUSINESS AND
PROFESSIONS CODE, AND THAT THE DESIGN IS CONSISTENT WITH CURRENT STANDARDS.
I UNDERSTAND THAT THE CHECK OF PROJECT DRAWINGS AND SPECIFICATIONS BY THE COUNTY OF SAN DIEGO
IS CONFINED TO A REVIEW ONLY AND DOES NOT RELIEVE ME, AS ENGINEER OF WORK, OF MY
RESPONSIBILITIES FOR PROJECT DESIGN.
BY:DATE:
RAYMOND L. MARTIN
HUNSAKER & ASSOCIATES SAN DIEGO, INC.
9707 WAPLES STREET, SAN DIEGO, CA 92121
RCE NO : 48670 _ EXPIRES: 06/30/2012.
Addendum to SWMH for U Costa O.iks North Neigh. 3 Page 3
Appendix A
^S? CITY OF
CARLSBAD
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Development Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
SECTION 1 NEW DEVELOPMENT
PRIORITY PROJECT TYPE
Does you project meet one or more of the following criteria:YES NO
1. Housing subdivisionf of 10 or more dwelling units.
condominium and apartments
Examples: single family homes, multi-family homes,
Commercial - greater than f-aere. Any development other than heavy industry or residential. Examples: hospitals;
laboratories and other medical facilities; educational institutions; recreational facilities; municipal facilities; commercial
nurseries; multi-apartment buildings; car wash facilities; mini-malls and other business complexes; shopping malls;
hotels; office buildings; public warehouses; automotive dealerships; airfields; and other light industrial facilities.
Heavy Industrial / Industry greater than 1 acre. Examples: manufacturing plants, food processing plants, metal
working facilities, printing plants, and fleet storage areas (bus, truck, etc.).
Automotive repair shop. A facility categorized in any one of Standard Industrial Classification (SIC) codes 5013,
5014,5541,7532-7534, and 7536-7539
Restaurants. Any facility that sells prepared foods and drinks for consumption, including stationary lunch counters
and refreshment stands selling prepared foods and drinks for immediate consumption (SIC code 5812), where the
land area for development is greater than 5,000 square feet Restaurants where land development is less than 5,000
square feet shall meet all SUSMP requirements except for structural treatment BMP and numeric sizing criteria
requirements and hydromodificatton requirements.
Hillside development Any development that creates 5,000 square feet of impervious surface and is located in an
area with known erosive soil conditions, where the development will grade on any natural slope that is twenty-five
percent (25%) or greater.
7. Environmentally Sensitive Area fESA)' All development located within or directly adjacent3 to or discharging
directly1 to an ESA (where discharges from the development or redevelopment will enter receiving waters within the
ESA), which either creates 2,500 square feet of impervious surface on a proposed project site or increases the area
of imperviousness of a proposed project site to 10% or more of its naturally occurring condition.
8.Parking lot Area of 5,000 square feet or more, or with 15 or more parking spaces, and potentially exposed to urban
runoff
Streets, roads, highways, and freeways. Any paved surface that is 5,000 square feet or greater used for the
transportation of automobiles, trucks, motorcycles, and other vehicles
10. Retail Gasoline Outlets. Serving more than 100 vehicles per day and greater than 5,000 square feet
11.Coastal Development Zone. Any project located within 200 feet of the Pacific Ocean and (1) creates more than
2500 square feet of impermeable surface or (2) increases impermeable surface on property by more than 10%.
12. More than 1-aen of disturbance Project results in the disturbance of more than 1-acre or more of land and is
considered a Pollutant-generating Development Project*.
1 Environmentally Sensitive Areas include but are not limited to ill Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special
Biological Significance by the State Water Resources Control Board (Water Quality Control Plan tor the San Diego Basin (1994) and amendments); water bodies
designated with the RARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Bash (1994) and amendments);
areas designated as preserves or their equivalent under the Multi Species Conservation Program within the Cities and County of San Diego; and any other equivalent
environmentally sensitive areas which have been identified by the Copermjttees.
2 "Directly adjacent" means situated within 200 feet of the Environmentally Sensitive Area.
3 "Discharging directly to' means outflow from a drainage conveyance system that is composed entirely of flows from the subject development or redevelopment site, and
not commingled with flow from adjacent lands.
4 Pollutant-generating Development Projects are those projects that generate pollutants at levels greater than background levels. In general, these include aR projects
that contribute to an exceedance to an impaired water body or which create new impervious surfaces greater than 5000 square feet and/or introduce new landscaping
areas that require routine use of fertilizers and pesticides. In most cases linear pathway projects that are for infrequent vehicle use. such as emergency or maintenance
access, or tor pedestrian or bicycle use, are not considered PoRutant-generating Development Projects if they are built with pervious surfaces or if they sheet flow to
surrounding pervious surfaces.
Section 1 Results:
.If you answered YES to ANY of the questions above your project is subject to Priority Development Project requirements. Please check the
"meets PRIORITY DEVELOPMENT PROJECT requirements" box in Section 3. A Storm Water Management Plan, prepared in accordance with City
Storm Water Standards, must be submitted at time of application.
If you answered NO to ALL of the questions above, then your project is subject to Standard Storrnwater Requirements. Please check the "does
not meet POP requirements' box in Section 3.
E-34 Page 2 of 3 REV 4/30/10
Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 4
Appendix A
CITY OF
CARLSBAD
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
Development Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.ca rlsbadca .gov
SECTION 2 SIGNIFICANT REDEVELOPMENT
Complete the questions below regarding your redevelopment project:
1 . Project results in the disturbance of more than 1 -acre or more of land and is considered a Pollutant-generating
Development Project (see definition in Section 1 ).
YES NO
If you answered NO, please proceed to question 2.
If you answered YES. then you ARE a significant redevelopment and you ARE subject to PRIORITY DEVELOPMENT PROJECT
raqurafnmti. Pl*a»» ctwck th* "meets PRIORITY DEVELOPMENT PROJECT requirement*' box in Section 3 below.
2. Is the project redeveloping an existing priority project type? (Priority projects are defined in Section 1 }
If you answered YES, please proceed to question 3.
If you answered NO, then you ARE NOT a significant redevelopment and your project is subject to STANDARD STORMWATER
REQUIREMENTS. Plus* check the "does not mact POP requirements" box in Section 3 below.
3. Is the project solely limited to just one of the following:
a. Trenching and resurfacing associated with utility work?
b. Resurfacing and reconfiguring existing surface parking lots?
c. New sidewalk construction, pedestrian ramps, or bike lane on public and/or private existing roads?
d. Replacement of existing damaged pavement?
tf you answered NO to ALL of the questions, then proceed to question 4,
If you answered YES to ANY of the questions then you ARE NOT a significant redevelopment and your project is subject to Standard
Stormwater Requirements. Pins* check th* 'dots not meet POP nqutwnents" box in Section 3 below.
4. Will your redevelopment project create, replace, or add at least 5,000 square feet of impervious surfaces on an existing
development or, be located within 200 feet of the Pacific Ocean and (1)create more than 2500 square feet of
impermeable surface or (2) increases impermeable surface on the property by more than 10%?
If you answered YES, you ARE a significant redevelopment, and you ARE subject to PRIORITY DEVELOPMENT PROJECT requirements.
Pleti* chx* th* 'meets PRIORITY DEVELOPMENT PROJECT requirement*" box in Section 3 below.
If you answered NO, then you ARE NOT a significant redevelopment and your project is subject to STANDARD STORMWATER
REQUIREMENTS. Ptoue check th* "doe* not m**t POP requirements' box in Section 3 below.
SECTION 3
Questionnaire Results:
K) My project meets PRIORITY DEVELOPMENT PROJECT (PDP) requirements and must comply with additional Stormwater criteria
per the SUSMP and must prepare a Storm Water Management Plan for submittal at time of application.
Q My project does not meet PDP requirements and must only comply with STANDARD STORMWATER REQUIREMENTS per the
SUSMP.
Applicant Information and Signature Box Tnis Box la CHy Use Only
San Elijo Rd & Rancho Santa Fe Raod
Atuscor's Parcel Numbers):
223-830-01to41, 223-831 -01 to39
Applicant Name:
Peter Hemphill
Appl
City Concurrence:
E-34 Page 3 of 3
Addendum to SWMP for La Costa Oaks North Neigh. 3 PageS
Appendix B
TYPICAL PLAN 1
'VVVVVVVVVV
vvvvvvvvvv
' V V V V VV V V V V
V V _^yV V V V V V V
V
LEGEND
PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS
IMPERVIOUS ROOF SURFACES
IMPERVIOUS HARDSCAPE SURFACES
Appendix B
TYPICAL PLAN 2
LEGEND
PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS
IMPERVIOUS ROOF SURFACES
IMPERVIOUS HARDS CAPE SURFACES
Appendix B
TYPICAL PLAN 3
' sK M/ -4' ^ \y
LEGEND
PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS
IMPERVIOUS ROOF SURFACES
IMPERVIOUS HARDSCAPE SURFACES
Appendix B
TYPICAL PLAN 4
£
•*—?-
7 V
V V
7 V V
V V V V V
7 V V
V V V V V
,!• u
V f V fel-7</• ^I
V V V V
v g. v v '
V V V V V V ^
7 V X V V V \i^7 V V
V V V V VVh'
LEGEND
PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS
IMPERVIOUS ROOF SURFACES
IMPERVIOUS HARDSCAPE SURFACES
Appendix C
GEOCON
WEST, INC.
GEOTECHNICAl • ENVIRONMENTAL • MATERIALS
Project No. 06105-52-28A
August 24, 2010
Standard Pacific Homes
26 Technology Drive
Irvine, California 92618
Attention: Mr. Peter Hemphill
Subject: VILLAGES OF LA COSTA - THE OAKS NORTH
NEIGHBORHOOD 3.1
CARLSBAD, CALIFORNIA
STORM WATER MANAGEMENT CONSULTATION
Reference: Update Geotechnical report. Villages of La Costa- The Oaks North, Neighborhood
3.1, Lots I through 80, Carlsbad, California, prepared by Geocon Incorporated,
dated January 20, 2010 (Project No. 06105-52-28).
Dear Mr. Hemphill:
In accordance with your request, we prepared this letter to discuss storm water management on the
subject site from a geotechnical engineering standpoint. We understand the regulatory agency is
requesting storm water management on the subject project Based on the referenced report, the
subject lots are underlain by compacted fill over the Santiago Peak Metavolcanic and granitic rocks.
The fill materials within the planned development possess a "very low" to "low" expansion potential
(expansion index of 50 or less).
A review of the grading plan and discussions with the design team indicate that storm water
management systems have been requested by me City of Carlsbad. These systems usually include
permeable pavement/pavers, grass lined swales, and retention areas. These devices are outlined in the
County of San Diego Standard Urban Stormwater Mitigation Plan (SUSMP) or Low Impact
Development (LID) Handbook.
Some devices are designed to promote water infiltration; however, the existing soil conditions are not
conducive to water infiltration. We recommend against water infiltration adjacent to structures,
improvements, compacted fill, and slopes. In this regard, distress and possible failure within the
existing and planned improvements will likely occur if infiltration were allowed. The distress could
include saturation and loss of soil support of foundations and pavements, settlement, and expansion.
Down-gradient properties may be subjected to seeps, springs, slope instability, movement of
foundations and slabs, or other impacts as a result of water infiltration. In addition, water may enter
underground utility pipe zones and impact improvements down gradient from the site. The potential
for distress depends on the amount of water to be retained, its retention time, soil permeability, and
other factors. We have not performed a hydrogeology study at the site.
3303 N. San Femondo Blvd., Suite 100 • Burbonk, California 91504-2531 • Telephone 818.841.8388 « fox 818.841.1704
Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 10
If you have any questions regarding this letter, or if we may be of farther service, please contact die
undersigned at your convenience.
Very truly yours,
GEOCONINCORPOi
AliSadr
CEG1778
(2) Addressee
(e-mail) Hunsaker & Associates
Attention: Mr: David Blalock
Project No. 06105-52-28A August 24,2010