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Home My WebLink AboutCT 05-16; La Costa Oaks North 3.4 & 3.5; Amendment No. 1 to Storm Water Management Plan; 2010-11-03Amendment No. 1 to Storm Water Management Plan For La Costa Oaks Neighborhood 3.4 & 3.5, PUD 05-13(A) November 02, 2010 Introduction: This Storm Water Management Plan Amendment has been prepared for Pulte Homes to accompany application for Precise Grading Plans allowing construction of 83 homes on existing single family lots La Costa Oaks North, Neighborhood 3.4 & 3.5 "the project". The application has been filed and assigned Planned Development Permit Amendment No. PUD 05-13(A) and will cover lots previously subdivided by Carlsbad Tract CT 05-16. 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 429-7, 429-7A, 446-6, and 446-6A respectively. All post-construction Treatment Control BMP's for this Neighborhood are currently in place and operational per the City Dwg. No. 429-7 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 file at the City. Integrated Low Impact Development (LID): *^^ Per City of Carlsbad SUSMP, Section 4, LID Design Guide, there are four conceptual LID Strategies for managing ^ runoff. f "1 1. Optimize the Site Layout * f>&Tmm 2. Use of Pervious Surfaces 3. Dispersion of Runoff 4. Integrated Management Practices Combinations of these strategies are recommended to provide multiple, complementary benefits to a project. t f*» Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 1 DB:kc K:\282i\2oio\A27.doc* W,o. ZS21-7 11/3/2010 11:36 AM Use of Pervious Surfaces has been analyzed and is a proposed strategy for every lot within this project. Such surfaces include the construction of front and rear yard turf areas in conjunction with landscape areas. Typical locations of proposed pervious areas for each building type can be seen in Appendix B. Dispersion of Runoff \s 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 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 IMF'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 Improvement Plan, Dwg. 446-4, for La Costa Oaks North Neighborhood 3.1, Approved 6/02/2008 Rough Grading Plan, Dwg. 446-4A, for La Costa Oaks North Neighborhood 3.1, Approved 6/02/2008 Improvement Plan, Dwg. 446-6, for La Costa Oaks North Neighborhood 3.1, Approved 7/12/2007 Rough Grading Plan, Dwg. 446-6A, 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 La Costa Oaks North Neigh. 3 Page 2 omkc K:\2S2i\2oio\A27.noci w.o. 2821-7 11/3/2010 11:36 AM 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: RAYMOND L MARTIN HUNSAKER & ASSOCIATES SAN DIEGO, INC. 9707 WAPLES STREET, SAN DIEGO, CA 92121 RCE NO.: 48670 DATE: EXPIRES: 06/30/2012 Addendum to SWMP for La Costa Oaks North Neigh. 3 Page3 DB:kc K:\2821\2010\A27.doc* ',0.2821-7 11/3/20X0 11:36 AM Appendix A %'•/ ARLSBAD STORM WATER STANDARDS QUESTIONNAIRE E-34 l.nnct Development Engineering 1G3!i l-'.irfiday Avenue 760-602-2750 www.carUbadca.gov SECTION 1 NEW DEVELOPMENT PRIORITY PROJECT TYPE [DOOS you pro joe t moot ones or more of tho following criteria: ^ _._-_,, ' /joiys/tiij^subdivisions of.J/O or ./ngre_.(tweljjng^imits. liixarnples: single family homes, multi-family homes. condorninium and apartment _ Commoicnl cjioit^i thin I f< rr Any development nlhoi Ihnn heavy industry or residential, Examples1 hospitals; Iriburatortes and oilier medical facilities: educational institutions, recreational facilities, municipal facilities, cornmoicial nurseries; multi-apartment buildings: car wash facilities; mini-malls and other business complexes, shopping mails, hotels, office buildings: public vvajehouses^auloiriotiy^clealfirships. airfields, andI other light induRlrmlfaciljtiBs Heavy <Vid(;sjntj/_/ Indtistiy giciterjhari 7,acre, Examples, manufacluring plants food processing plants, metal /oiking facilities, piinting plants, and fleet sloiatje areas (bus, truck, Etc.). / Autoniot±vt_reirtii^tiQ[)_ A Ui ihty rrfte liOlfl. !i54l. 7B32-753'!. and 7536-7539 i any one of Standard Industrial Classification (SIC) codes fiOUv fiesfaijro/Jfs. 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 foel shall meet all SUSMP requirements except foi structural trealmenl RMP and numeric sizing criteria requirements and hydromodification requirements. G- /W/s/rfe_t/oyo/opfne/iL Any development that creates 5.000 square feet of impervious surface and is located in am area with known erosive soil conditions, where the development will grade on any natural slope that is twenty-five jiercenl (25%) or greater _ _ _ 7 £i!!di;ontn£(^ All development located within or directly adjacent7 to or discharging directly' to an F.SA {where discharges from the development or redevelopment will enter receiving waters within the EISA), which either creates 2.500 square feet of impervious surface on a proposed project site or increases the area oJJi^^ryjoLJsnesij_of_a_j3ropos@d l2I9J?_9.Lsjte to 10% 01 more of its naturally occurring condil]gn_ 8 ESLhidfLlQi Area °f 5.000 square feet or more, or with 15 or more parking spaces, and potentially exposed to urban runoff 9- S?t,3ofgL^Qg[{Is,._../i/fj/jwaystwjinctfrQ(wa i/s Any paved surface that is 5.000 square feet or grealer used for the; transportation of automobiles, trucks, motorcycles, and other vehicles ftefn/7 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 fee! of the Pacific Ocean and (1) creates more than 2500 square feel oT impermeable surface or (2) increases impermeable surface on property by more than 10%. Mgf.gJ|iafi_jAacfg_p_f_f//gfurJ3aggg±. Project results in the disturbance of more than 1-acre of more of land and is considered a Pollutant-generating Development Project'''. ilrockice new Ian i Environmentally" SBiisilive Areas include t>u( arc nol limited to all Clean Water Act Section 303(dj impaired water bodies, areas desirjnaler.1 35 Areas of Special Biological Significance lay ll>o Slate 'Miter Resources Control Board (Water Quality Control Plan (or His Sari Diego Basin 119941 and amendments), water bodies designated with the RARE beneficial use by Ilia Stale Water Resources Control Board (Water Quality Control Plan for the Son Diego Basin ilOOfl) and amendments): areas designated as preserves or Iheir equivalent under the Mulli Species Conservalion Program within the Cilies and County of San Diego, and any other equivalent environmentally sensitive areas which liave been identified by the Copermillees ? Directly adjacenl' means situated within 200 feet ol Hie Environmenlally Sensilive Araa. nol commingled wilh (low from ailjacenl lands A Poilulani-genernling Development Projecis are thoss projects thai generaie pollutants at levels rjrealfsr llian background levels. In general mcse include all rirojecls thsl conlnhule lo an exceerlance lo an impaired water body or which create now impervious surfaces grealer than GOOD square feet areas Ihni require roulme use ol fertilizers and peslicideB In most cases linear pathway projects lhal aie for infrequent vohicte uso ai access, or (or pedfislrian or bicycle use. are nol considered Poliulanl-gBneraling Oeveloiimenl Projecis il Ihey are built wilh perviou siirrounctiiig_per\'KiiiS__siir(aces. ___ _____ „ . „ ._ . ___.__.„ _ If you answered YliiS to ANY o( the questions al)0ve your project is suhjftrl lo Priority Dovolopmont Project requirBinenls. Pteiise chuck the 'meets PRIORITY DEVELOPMENT PROJECT requirements" Ijox in .Section 3. A Storm Water Management Plan. |)r«parftfl in a ceo ret a nee wilh Oily Storm Water Standards, must he submitted at time of application. II you answered NO lo ALU of the questions afonvn. then your projecl is subject to Standard Stormwater Requirements. PleasR check the 'does not meet POP requirements" box in Section 3. ^^ _„_ _____ Page 2 of 3 Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 4 DB:kc K:\2B21\2010\A27.docx (.0.2821-7 11/3/201011:38 AM Appendix A STORM WATER STANDARDS QUESTIONNAIRE E-34 De\if!lopn-t<-[nt Service Land Development Engineering 163.r) Faraday Aveniit? 760-602-7.750 SECTION 2 SIGNIFICANT REDEVELOPMENT .. . — -. __ „ , --... — .~-. j r.~T»roJBCt refills in"ihe"disturbance of more than i-acrc or more of (and and is considered d Pollutant-generating | i _ Development^Project (see definition in Section \)_. _ | . T If you answered NO, please proceed In question 2. \ If yuu answered YES, then you ARE a significant redevelopment and you ARE subject to PRIORITY DEVELOPMENT PROJECT [ requirements, Please chock the "meets PRIORITY DEVELOPMENT PROJECT requirements" box in Section 3 below. j 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 find your projecl is subject to STANDARD STORMWATER \ REQUIREMENTS. Please check the "does not meet POP requirements" box in Section 3 below. _____ ! 3 Is the project solely limited to just one of the following: j a Trenching and resurfacing associated with utility work? ; 1) Resurfacing and reconfiguring existing surftir.fi parking lots? I t; New sidewalk tonslriKlion pedestrian ramps or bike lane on public and/or private existing roads? j j d Replacement of existing damaged pavement? j , j If you answered MO to ALL. of the questions, then proceed to question 1, I If you nnsw,prrd Yf S to ANY of the questions then you ARE NOT a significant redevelopment and your project is subject to Standard I Stormwatni KiHjuiiemsnta. Please check the ''does not meet POP I'equiremunts" box ini Sectioni__3 be-low ___ _ 1 Will your rodevRlopment (iroject create, replace, or add at least 5.000 square feel oi impervious surfaces on an existing I j development or, be located within 200 fee! of the Pacific Ocean and (1)creale more than 2500 square feet of j | impefnieable suiface or (2) Micre^se^jnigermeablejurfac_e onjhe pi;of)e_rty; by..niore lhan 10%? _____ _ |_ !. If you answered YES. you ARE a sTgfiificanTrecTevelopment. and you ARE subject to PRIORITY DEVELOPMENT PROJECT requirentonts Please clieck the niaets PRIORITY DEVELOPMENT PROJECT requirements' 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 Please check the 'does not meet PDP requirements' box in Section 3 below SECTION 3 1 QiiBj>Ugi|nairtj Results.; My projecl meets PRIORITY DEVELOPMENT PROJECT (PDP) requirements and must comply with additional stormwater criteria per the SUSMP and must prepare a Storm Water Management Plan lor submillal at lime of application. My project rloos not meet PDP requirements and must only comply with STANDARD STORMWATER REQUIREMENTS per the SUSMP. __ Applicant Infoimation and Signature Box Address: 27Q'| Peurta Real, Suile 300 Mission Viejo, Ca 92691 Applicant Name: David Hutchins Applicant Signature-' Assessor's Parcel Numbers) 223-851-01-27 & 223-841-01-17 Applicant Title: :E R-3<1 Page 3 of 3 Addendum to SWMP for La Costa Oaks North Neigh. 3 PageS DB:kc K:\2821\2010\A27.docx w.0.2821-7 11/3/2010 U:37 AM LEGEND Appendix B TYPICAL PLAN 1 PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS IMPERVIOUS ROOF SURFACES IMPERVIOUS HARDSCAPE SURFACES Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 6 DBikc K:\2821\2010\A27.docx '.0.2821-7 11/3/2010 11:36 AM Appendix B TYPICAL PLAN 2 V. £ V V 'S7' V VVVV^VVVVV 7VVVVVVVV 7VVVVVVVVV LEGEND PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS IMPERVIOUS ROOF SURFACES IMPERVIOUS HARDSCAPE SURFACES Addendum to SWMP for La Costa Oaks North Neigh. 3 Page?DB:kc K:\2821\2010\A27.docx w.o. 2821-7 11/3/201011:36 AM Appendix B LEGEND TYPICAL PLAN 3 PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS IMPERVIOUS ROOF SURFACES IMPERVIOUS HARDSCAPE SURFACES EZS Addendum to SWMP for La Costa Oaks North Neigh. 3 PageS DB:hc K:\2821\2010\A27.doc* v-Q. 2821-7 ll/3/201011:36AM Appendix B TYPICAL PLAN 4 LEGEND PERVIOUS SURFACES - PROPOSED LAWN AND LANDSCAPE AREAS IMPERVIOUS ROOF SURFACES IMPERVIOUS HARDSCAPE SURFACES Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 9 DB:kc K:\2821\2010\A27.docx w.o. 2821-7 11/3/2010 11:36 AM Appendix C GEOCON I N C O H I' O U A T I:: 11 C- I O T f C M N I C A I * e M V I P O N M f: N 1 A I f* M ^ T ^ R 1 A Project No. 06105-52-27 Novembers. 2010 Pulle Homes 27101 PuertaReal. Suite 300 Mission Viejo. Califomia 92619 Attention: Mr. David Hutch ins Subject: VILLAGES OF LA COSTA - THE OAKS NORTH NEIGHBORHOODS 3.4 AND 3.5 LOTS 1 THROUGH 83 CARLSBAD. CALIFORNIA STORM WATER MANAGEMENT CONSULTATION Reference: Update Geotechnical report, Villages of Ln Costa The Oaks North, Neighborhood 3.4 and 3.5 Lots I through S3, Carlsbad, California, prepared by Geocon Incorporated, dated Jamiary 5. 2010 (Project No. 06105-52-27). Dear Mr. Hutchins: In accordance with your request, we prepared this letter to discuss storm water management on the subject silc from a geolechnical engineering standpoint. 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 the City of Carlsbad. These systems usually include permeable pavement/pavers, grass lined swales, and retention areas. These devices arc 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 Addendum to SWMP for La Costa Oaks North Neigh. 3 Page 10 On:kc K:\2a2ivoio\A27.docx w.0.2821-7 11/3/201011:36 AM Cor distress depends on llic nniounl of \\aler 10 be retained, ils rclcnlioii time, soil permeability, and other factors. We have not performed a hydrogcology study at the site. I I'von lune any questions regarding this letter, or if ue may be of further service, please contact the undersigned at \onr convenience. Ven truly yours. GEOCON INCORPORATED A(i Sad i CEG I77H (2) Addressee (e-mail) Hunsakcr & Associates Attention: Mr Oaud Blalock I'nijix-tNo ll(i|lli-!i:-27 Addendum to SWMP for la Costa Oaks North Neigh. 3 Page 11 DB:kc K:\2821\2010\A27.docx w.o. Z821-7 11/3/201011:36 AM