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HomeMy WebLinkAboutCDP 14-13; Hirschkoff Residence; Coastal Development Permit (CDP) (3)GITY OF CARLSBAD ENGINEERING DIVISION PRELIMINARY STORM WATER REPORT FOR HIRSCHKOFF RESIDENCE Jefferson Street ENGINEER OFWORK VINCENT L. SAMPO - RCE 44173 PREPARED BY: SAMPO ENGINEERING, INC. 171 SAXONY ROAD, SUITE 213 ENCINITAS, CA 92024 760-436-0660 Hirschkoff Residence CDP 13-XX Standard Development Project Sampo Engineering, Inc. 5/1/2014 1.0 Project Setting The subject property is located on the westerly side of Jefferson Street, approximately 600 feet north of the intersection with Las Flores Drive, in Carlsbad, Califomia. The property has an area of 0.28 acres and is legally described as a portion of Tract No. 2 of Laguna Mesa Tracts, according to Map No. 1719 (APN: 155-180-28). The property is bounded on the north by Carlsbad Road which is undeveloped but has not been vacated, bounded on the east by Interstate 5, bounded on the west by a single-family residence and bounded on the south by Jefferson Street. The subject property is currently vacant. The property currently descends from the right- of-way of Jefferson Street in a northerly direction to the rear slope of the property at an average grade of 8.3%. From the top of the rear slope the property continues to descend at a 1 Vi-.l gradient to the northerly property line. The northerly slope of the property is considered environmentally sensitive and no disturbance of this area is proposed. The owner proposes to develop the property with a new single-family residence, two attached garages, permeable paver driveway, patios, planters and landscaping. The subject property will share an existing driveway cut with the neighbor to the west where there is an existing access easement in-place. Per the County of San Diego Hydrology Manual's Soil Hydrologic Group Map the project appears to have soil group B present. In preparation of this report, Sampo Engineering, Inc. (SEI) reviewed the existing on-site and off-site topography prepared by the owner's surveyor, additional off-site topography obtained from the city web-site and the soil report prepared by Engineering Design Group. SEI conducted a site visit and field reconnaissance on Tues April 8, 2014 to verify existing drainage pattems and potential sources of pollution. Photos were taken of the undeveloped project area, Jefferson Street and vegetation that currently exists. SEI has prepared a preliminary Hydrology Study of the existing and proposed conditions, the calculations and drainage maps, of which, are contained in this report. No evidence of erosion was observed in the upper flatter portion ofthe property during SEI's site visit of April 8, 2014. There was some localized erosion that was visible in the steeper northerly portion of the site that is to be left undisturbed. Very little trash or debris was observed on the property. 1.1 Site Development Opportunities and Constraints Common with any proposed development, the proposed project has its own unique characteristics that present opportunities and constraints for storm water control and treatment. Some constraints that are anticipated for the proposed development ofthe Hirschkoff Residence Sampo Engineering, Inc. CDP 13-XX 4/30/2014 Standard Development Project 2 project are based on the existing topography and underlying soil conditions. Due to the environmentally sensitive and steep slope near the north and downstream end ofthe property and soil engineering concems about disturbing and replacing the slope, the owner has decided not to pursue conveying storm water via a pipe or some other storm drain system from the top of the slope to the bottom of slope near the northerly property line. For this reason storm water will be treated on-site near the bottom of the building pad and then pumped to Jefferson Street where it will be discharged into the Jefferson Street gutter, where it will flow on the surface to an existing curb inlet at the northeast comer intersection of Las Flores and Jefferson Street. The storm water is then conveyed in an existing 18 inch diameter storm drain pipe to the west to the Buena Vista Lagoon. Per the preliminary geotechnical report for the project infiltration is not recommended since the proposed residence will sit atop an existing steep slope, and therefore for the subject property. For this reason bio-retention basins and flow through planters will be lined with impermeable membranes to prevent infiltration into the adjacent soils. 1.2 Nearby Water Bodies, Existing Storm Drain Systems No existing public or private storm drain systems are located on or adjacent to the subject property. Storm water draining from the property currently travels overland westerly to the Buena Vista Lagoon before reaching the Pacific Ocean. None of the subject property currently drains to Jefferson Street. There are two curb inlets located at the intersection of Las Flores and Jefferson Street approximately 600 feet south of the subject property. It is these two inlets that collect all storm water in Jefferson Street and the surrounding neighborhood as shown in one of the attached drainage maps. The collected storm water is then conveyed westerly to the shore of the Buena Vista Lagoon via an 18" diameter ACP public storm drain. 2.0 Applicable Storm Water Standards The project has been determined to be classified as a Standard Development Project. Although the property is located within 200 feet of an Environmentally Sensitive Area (ESA) the project proposes less than 2500 square feet of impervious surfaces (the entire driveway surface is proposed as permeable pavers or some other permeable pavement). Priority Project requirements do not apply to this project therefore Hydromodification requirements also do not apply. Regardless, the project proposes LID and numerically sized treatment control facilities for two bio-retention basins and two flow through planters as shown on the grading plan and as supported by calculations herein. Please see attached Storm Water Standards Questionaire (E-34) Hirschkoff Residence Sampo Engineering, Inc. CDP 13-XX 4/30/2014 Standard Development Project 3 3.0 Identify Pollutants of Concern The project proposes to redevelop the property by constmcting a new single-family residence, two attached garages, permeable paver driveway, planters and landscaping. Pollutants anticipated for this type of land use are sediment, nutrients, trash & debris, oxygen demanding substances, oil & grease, bacteria & virases, and pesticides. The project lies within the Carlsbad Watershed in the Buena Vista Creek Hydrologic Area (904.2). Storm water from the site drains to the Buena Vista Lagoon before reaching the Pacific Ocean. The Buena Vista Creek is listed as an impaired water body per 303d listing for indicator bacteria, nutrients, and sedimentation/siltation. The Buena Vista Lagoon has many beneficial uses including public trails surrounding the lagoon, and fishing. Indicator bacteria, nutrients, and sediment are primary pollutants-of-concem for the proposed project and shall be mitigated with bio-retention basin and flow through planter BMP's. Hirschkoff Residence Sampo Engineering, Inc. CDP 13-XX 4/30/2014 Standard Development Project 4 LEGEND PROPERTY BOmARY ROOF/HARDSCAPE (lUPERMEABlE) PERHtEABLE PAVERS LANDSCAPING SYMBOL AREA IMPERVIOUS AREA TAKE OFF T T =f T- lh -I- -I- -I- 2,401 SF 2.590 SF THIS PROJECT PROPOSES Z476 SF OF IMPERVIOUS AREA, THEREFORE IT IS CLASSIFIFED AS A 'STANDARD'PROJECI BUENA VISTA LAGUNA X o OMR: JOEL HIRSCHKOFF 1483 CORAL m SAN MARCOS. CA 92078 aw ADDRESS: VACANT PROPERTY ON JEFFERSON STREET, CARLSBAD CA. ASSESSOR'S PARCEL NO.: 155-180-28 o o z DC LU UJ C5 a Z p LU O CL < CO NJ^ CITY OF CARLSBAD STORM WATER STANDARDS QUESTIONNAIRE E-34 Development Services Land Development Engineering 1635 Faraday Avenue 760-602-2750 www.carlsbadca.gov INSTRUCTIONS: To address post-development pollutants that may be generated from development projects, the City requires that new development and significant redevelopment priority projects incorporate Permanent Storm Water Best Management Practices (BMP's) into the project design per the City's Standard Urban Stormwater Management Plan (SUSMP). To view the SUSMP, refer to the Engineering Standards (Volume 4, Chapter 2) at www.carlsbadca.Qov/standards. Initially this questionnaire must be completed by the applicant in advance of submitting for a development application (subdivision, discretionary permits and/or construction permits). The results of the questionnaire determine the level of storm water standards that must be applied to a proposed development or redevelopment project. Depending on the outcome, your project will either be subject to 'Standard Stormwater Requirements' or be subject to additional criteria called 'Priority Development Project Requirements'. Many aspects of project site design are dependent upon the storm water standards applied to a project. Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts. City staff has responsilDility for mailing the final assessment after submission of the development application. If staff determines ttiat 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 separate completed and signed questionnaire must be submitted for each new development application submission. Only one completed and signed questionnaire is required when multiple development applications forthe same project are submitted concurrently. In addition to this questionnaire, you must also complete, sign and submit a Project Threat Assessment Form with construction permits for the project. Please start by completing Step 1 and follow the instructions. When completed, sign the form at the end and submit this with your application to the city. STEPl TO BE COMPLETED FOR ALL PROJECTS To determine if your project is a priority development project, please answer the following questions: YES NO 1. Is your project LIMITED TO constructing new or retrofitting paved sidewalks, bicycle lanes or trails that meet the following criteria: (1) Designed and constructed to direct storm water runoff to adjacent vegetated areas, or other non-erodible permeable areas; OR (2) designed and constructed to be hydraulically disconnected from paved streets or roads; OR (3) designed and constructed with permeable pavements or surfaces in accordance with USEPA Green Streets guidance? X 2. Is your project LIMITED TO retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in accordance with the USEPA Green Streets guidance? X If you answered "yes" to one or more of the above questions, then your project is NOT a priority development project and therefore is NOT subject to the storm water criteria required for priority development projects. Go to step 4, mark the last box stating "my project does not meet PDP requirements" and complete applicant Information. If you answered "no" to both questions, then go to Step 2. E-34 Page 1 of 3 Effective 6/27/13 STORM WATER Development Services Land Development Engineering STANDARDS Development Services Land Development Engineering CITY OF CARLSBAD QUESTIONNAIRE E-34 1635 Faraday Avenue 760-602-2750 www.carlsbadca.gov ;.: STEP 2 .::::;:!:::: TO BE COMPLETED FOR ALL NEW OR REDEVELOPIWENT PROJECTS To determine if your project is a priority development project, please answer the following questions: ygs NO 1. Is your project a new development that creates 10,000 square feet or more of impervious surfaces collectively over the entire project site? This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land. X 2. Is your project creating or replacing 5,000 square feet or more of impen/ious surface collectively over the entire project site on an existing site of 10,000 square feet or more of impervious surface? This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land. X 3. 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 restaurant? A restaurant is a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption. X 4. Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a hillside development project? A hillside development project includes development on any natural slope that is twenty-five percent or greater X 5. 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 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. X 6. 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 street, road, highway freeway or driveway? A street, road, tiighway, freeway or driveway is any paved impervious surface used for the transportation of automobiles, trucks, motorcycles, and other vehicles. X 7. Is your project a new or redevelopment project that creates or replaces 2,500 square feet or more of impervious surface collectively over the entire site, and discharges directly to an Environmentally Sensitive Area (ESA)? "Discharging Directly to" includes flow that is conveyed overland a distance of 200 feet or less from the project to the ESA, or conveyed in a pipe or open channel any distance as an isolated flow from the project to the ESA (i.e. not commingles with flows from adjacent lands).* X 8. Is your project a new development that supports an automotive repair shop? An automotive repair shop is a facility that is categorized in any one of the following Standard Industrial Classification (SIC) codes: 5013, 5014, 5541, 7532-7534, or 7536-7539. X 9. Is your project a new development that supports a retail gasoline outlet (RGO)? This category includes RGO's that meet the following criteria: (a) 5,000 square feet or more or (b) a project Average Daily Traffic (ADT) of 100 or more vehicles per day. X 10. Is your project a new or redevelopment project that results in the disturbance of one or more acres of land and are expected to generate pollutants post construction? X 11.1s 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%? X If you answered "yes" to one or more of the above questions, you ARE a priority development project and are therefore subject to implementing structural Best Management Practices (BMP's) in addition to implementing Standard Storm Water Requirements such as source control and low impact development BMP's. A Storm Water Management Plan (SWMP) must be submitted with your application(s) for development. Go to step 3 for redevelopment projects. For new projects, go to step 4 at the end of this questionnaire, check the "my project meets PDP requirements" box and complete applicant Information. If you answered "no" to all of the above questions, you ARE NOT a priority development project and are therefore subject to implementing only Standard Storm Water Requirements such as source control and low impact development BMP's required for all development projects. A Storm Water Management Plan (SWMP) is not required with your appllcation(s) for development. Go to step 4 at the end of this questionnaire, check the "my project does not meet PDP requirements" box and complete applicant Information. E-34 Page 2 of 3 Effective 6/27/13 CITY OF CARLSBAD STORM WATER STANDARDS QUESTIONNAIRE E-34 Development Services Land Development Engineering 1635 Faraday Avenue 760-602-2750 www.carlsbadca.gov STEP 3 TO BE COMPLETED FOR REDEVELOPMENT PROJECTS THAT ARE PRIORITY DEVELOPEMENT PROJECTS ONLY Complete the questions below regarding your redevelopment project: YES NO Does the redevelopment project result in the creation or replacement of impervious surface in an amount of less than 50% of the surface area of the previously existing development? If you answered "yes," the structural BMP's required for Priority Development Projects apply only to the creation or replacement of impervious surface and not the entire development. Go to step 4, check the "my project meets PDP requirements" box and complete applicant Information. If you answered "no," the structural BMP's required for Priority Development Projects apply to the entire development. Go to step 4, check the "my project meets PDP requirements" box and complete applicant information. STEP 4 , CHECK THE APPROPRIATE BOX AND COMPLETE APPLICANT INFORMATION • My project meets PRIORITY DEVELOPMENT PROJECT (PDP) requirements and must comply with additional stormwater criteria per the SUSMP and I understand I must prepare a Storm Water Management Plan for submittal at time of application. I understand flow control (hydromodification) requirements may apply to my project. Refer to SUSMP for details. My project does not meet PDP requirements and must only comply with STANDARD STORMWATER REQUIREMENTS per the SUSMP. As part of these requirements, I will incorporate low impact development strategies throughout my project. Applicant Information and Signature Box Address: ^e^Vft\f ^ . Accessor's Parcel Number(s): 155-180-28 Applicant Name: i / / _ I n ^ Applicant Signatur^y Applicant Title: Date: This Box for City Use Only City Concurrence: YES NO City Concurrence: By: Date: Project ID: * Environmentally Sensitive Areas include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); water bodies designated with the F?ARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); areas designated as preserves or their quivalent 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 Copermittees. E-34 Page 3 of 3 Effective 6/27/13 4.0 Documentation of Storm Water Design To satisfy storm water quality standards for treatment control the project proposes the use of Integrated Management Practices (IMP's). The IMP's are sized for treatment only since Hydromodification is not required. The project site has been divided into four Drainage Management Areas (DMA's) and each DMA drains to one IMP area for storm water treatment and flow control (see attached DMA Site Plan). The following tables show the calculations and sizing factors used to calculate the IMP's. IMP SIZING CALCULATOR DMA Code: 1 Total Basin Area: 1,282 sf DMA Description: Southwesterly portion of property tributary to the southwesterly biorentetion basin. Soil Type: IMP type DMA DMA area Post Project Area Runoff x runoff Surface Type (sf) factor factor B bioretention basin Roof/Hardscape 341 1.0 341 IMP Sizing factor (WQ Minimum Proposed only) Area Area Permeable Pavers 744 0.1 74 IMP Sizing factor (WQ Minimum Proposed only) Area Area Landscaping 177 0.1 18 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP area 23 0 0 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP Sizing factor (WQ Minimum Proposed only) Area Area Total 433 0.04 17 23 DMA Code: . 2 Total Basin Area: 2,916 sf DMA Description: Southeast portion of property tributary to the southeastedy bioretention basin. Soil Type: IMP type DMA DMA area Post Project Area Runoff x runoff Surface Type (sf) factor factor B bioretention basin Roof/Hardscape 427 1.0 427 IMP Sizing factor (WQ Minimum Proposed only) Area Area Permeable Pavers 1829 0.1 183 IMP Sizing factor (WQ Minimum Proposed only) Area Area Landscaping 660 0.1 66 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP area 30 0 0 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP Sizing factor (WQ Minimum Proposed only) Area Area Totai 676 0.04 27 30 Hirschkoff Residence CDP 13-XX Standard Development Project Sampo Engineering, Inc. 4/30/2014 DMA Code: 3 Total Basin Area: 1,191 sf DMA Description: Northeastedy portion of property tributary to north easterly flow through planter. Soil Type: IMP type DMA DMA area Post Project Area Runoff x runoff Surface Type (sf) factor factor B flow through planter Roof/Hardscape 846 1.0 846 IMP Sizing factor (WQ Minimum Proposed only) Area Area Permeable Pavers 119 0.1 12 IMP Sizing factor (WQ Minimum Proposed only) Area Area Landscaping 226 0.1 23 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP area 35 0 0 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP Sizing factor (WQ Minimum Proposed only) Area Area Total 881 0.04 35 35 DMA Code: 4 Total Basin Area: 1,331 sf DMA Description: Northwesterly portion of property tributary to northwestedy flow through planter. Soil Type: IMP type DMA DMA area Post Project Area Runoff x runoff Surface Type (sf) factor factor B flow through planter Roof/Hardscape 852 1.0 852 IMP Sizing factor (WQ Minimum Proposed only) Area Area Permeable Pavers 18 0.1 2 IMP Sizing factor (WQ Minimum Proposed only) Area Area Landscaping 461 0.1 46 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP area 37 0 0 IMP Sizing factor (WQ Minimum Proposed only) Area Area IMP Sizing factor (WQ Minimum Proposed only) Area Area Totai 900 0.04 36 37 Hirschkoff Residence CDP 13-XX Standard Development Project Sampo Engineering, Inc. 4/30/2014 LEGEND DMA 1 DMA 2 DMA J DMA 4 SYMBOL St 3 .8 BUENA VISTA LAGUNA r=2o' DMA 2 TRIBUTARY AREA= 2,916 SF IMPERVIOUS AREA= 427 SE PERVIOUS= 2489 SE VICINITY MAP DMA J TRIBUTARY AREA= 1,191 SE IMPERVIOUS AREA^ 846 SE PERVIOUS= 345 SE DMA 1 TRIBUTARY AREA= 1,262 SE IMPERVIOUS AREA= 541 SE PERVIOUS^ 921 SE DMA 4 TRIBUTARY AREA= 1,331 SE IMPERVIOUS AREA= 852 SE PERVIOUS= 479 SE CITY OF CARSLBAD DRAINAGE MANAGEMENT AREAS FOR HIRSCHKOFF RESIDENCE VACANT PROPERTY ON JEFFERSON ST O o z cc LU LLI z o z LU O IN ill DRAINAGE STUDY CALCULATOR EXISTING BASIN # 1 JN: 14-107 Hirschkoff DATE: April 30, 2014 DESCRIPTION: Northeasteriy portion of subject property from Jefferson Street to the rear top of slope AREA = 9,420 SF= 0.216 AC. C = (8570 sfMO.35^ + (850 sfVO.95^ 9420 sf Tol = 1.8(1.1-.35)(220r(1/2' (7.7r(1/3) 20.02 1.97 0.4 10.16 MIN Il0 150 Iioo = 7.44(1.6)(10.16)'^(-.645) 7.44(2.1 )(10.16)^(-.645) 7.44(2.5)(10.16)'^(-.645) 2.67 IN/HR 3.50 IN/HR 4.17 IN/HR QlO = (0.40)(2.67 IN/HR)(0.216 AC) Qso = (0.40)(3.50 IN/HR)(0.216 AC) QlOO = (0.40)(4.17 IN/HR)(0.216 AC) 0.23 CFS 0.30 CFS 0.36 CFS EXISTING BASIN # 2 DESCRIPTION: Southwesterly portion of the subject property from top of slope to the rear property line AREA = 4,710 SF = 0.108 AC. c = 0.35 Tc1 = 1.8(1.1-.35)(53)^(1/2) (66)'^(1/3) 9.83 4.04 2.43 MINUTES < 5.0 USE 5.00 MINUTES I10 = 7.44(1.6)(5.00)'^(-.645) l50 = 7.44(2.1)(5.00)'^(-.645) Iioo = 7.44(2.5)(5.00)'^(-.645; 4.22 IN/HR 5.53 IN/HR 6.59 IN/HR QlO = (0.35)(4.22 IN/HR)(0.108 AC) Qso = (0.35)(5.53IN/HR)(0.108 AC) QlOO = (0.35)(6.59 IN/HR)(0.108 AC) 0.16 CFS 0.21 CFS 0.25 CFS EXISTING BASIN #3 (OFF SITE) DESCRIPTION: Portion of Jefferson St, the hillside to the east and a small portion west of Jefferson St. tributary to the gutter north of the curb inlet at the northeast corner of Jefferson and Las Flores Intersection AREA = 78,410 SF = 1.800 AC. c = 0.55 Tc1 = 1.8(1.1-.55)(100)^(1/2' (2.0)^^(1/3) 9.90 1.26 7.86 MINUTES Tc2 = 1.8(1.1-.35)(40)^(1/2) (25)'^(1/3) 8.54 2.92 2.92 MINUTES 10.78 MINUTES TOTAL Iio Isc Iioo = 7.44(1.6)(10.78)'^(-.645) = 7.44(2.1 )(10.78)'^(-.645) 7.44(2.5)(10.78)'^(-.645) = 2.57 IN/HR 3.37 IN/HR 4.01 IN/HR QlO = (0.55)(2.57 IN/HR)(1.80 AC) Qso = (0.55)(3.37 IN/HR)(1.80 AC) Ql00 = (0.55)(4.01 IN/HR)(1.80 AC) 2.54 CFS 3.34 CFS 3.97 CFS =ZHC 7 "=60' EXISTING HYDROLOGY FOR HIRSCHKOFF RESIDENCE VACANT PROPERTY ON JEEEERSON ST 0 30 60 120 o z cs z tr LLI UJ z o z LU O Q. < CO life EXISTING BASIN #4 (OFF SITE) DESCRIPTION: Offsite area tributary to the two curb inlets at the intersection of Jefferson Street and Las Flor AREA = C = Overland Flow Tc1 = Tc2 = Gutter Fiow Tc3 = 3.77 acres 0.55 lio - Iso - lioo = 1.8(1.1-.55V50)^(1/2) (1.0)^^(1/3) 1.8(1.1-.35)(30W1/2) (23)'^(1/3) 350 ft 3.8 ft/s X 1/60 7.44(1.6)(11.1 )'^(-.645) 7.44(2.1)(11.1)'^(-.645) 7.44(2.5)(11.1)'^(-.645) 7.00 1.00 7.39 2.84 2.52 IN/HR 3.31 IN/HR 3.94 IN/HR 7.00 2.6 1.5 MINUTES MINUTES MINUTES 11.1 MINUTES TOTAL Q10 = (0.55)(2.52 IN/HR)(3.77 AC) Qso = (0.55)(3.31 IN/HR)(3.77 AC) Q100 = (0.55)(3.94 IN/HR)(3.77 AC) 5.22 CFS 6.86 CFS 8.17 CFS 7 "=60' 720 HIRSCHKOFF RESIDENCE VACANT PROPERTY ON JEFFERSON ST LU o < CO t PROPOSED BASIN #1 DESCRIPTION: Northeasterly portion of subject property from Jefferson Street to the rear top of slope AREA = c = C = Tc1 = 9,420 SF = 0.216 AC. (850 sf)(0.95) + (2476 sf)(0.95) + (3102 sf)(0.35) + (2992 sf)(0.45^ 9420 sf 0.59 1.8(1.1-.35)(120r(1/2' (4.2)'^(1/3) 14.79 1.61 9.19 MINUTES lio Iso |100 = 7.44(1.6)(9.19)'^(-.645) = 7.44(2.1)(9.19)'^(-.645) 7.44(2.5)(9.19)'^(-.645) = 2.85 IN/HR 3.74 IN/HR 4.45 IN/HR QlO = (0.59)(2.85 IN/HR)(0.216 AC) Q50= (0.59)(3.74 IN/HR)(0.216 AC) QlOO = (0.59)(4.45 IN/HR)(0.216 AC) 0.36 CFS 0.48 CFS 0.57 CFS Determine gutter depth of flow on east side of Jefferson Street: Qioo = 3.97 CFS (Existing Basin #3) + 0.57 CFS (Proposed Basin #1) = 4.54 CFS From County of San Diego Gutter and Roadway Discharge-Velocity Chart For gutter slope = 0.5% and 0=4.54 CFS, Depth = 0.40 ft From survey data of street cross sectons at 0.4 feet gutter depth the street wili flood approximately 5 to 8 feet west of the easterly curb line, which will allow for two lanes of traffic in the flooded condition and will not rise to the crown elevation of the street in a 100 yr event (See attached chart). BUENA VISTA LAGUNA ^26 CITY OF CARSLBAD PROPOSED HYDROLOGY FOR HIRSCHKOFF RESIDENCE VACANT PROPERTY ON JEFFERSON ST CC LU m z C3 z LU O CL < CO t Sis STORM DRAIN HYDRAULIC CALCULATION DESCRIPTION: MAXIMUM STORM DRAIN CAPACITY & HEIGHT CALCULATIONS FOR 18" ACP PUBLIC STORM DRAIN AT THE INTERSECTION OF JEFFERSON STREET AND LAS FLORES. THE PIPE DISCHARGES DIRECTLY TO BUENA VISTA LAGOON. Check Exisitng Basin 4 Calculations for Qioo = 8.17(0100 Ex. Basin 4) + 0.57 (QIOO Proposed) = 8.74 CFS Maximum Storm Drain Slope = 3.6% (see attached As-Buiits) Maximum Capacitv for 18" SD (@ 3.6% Qmax= 0.498 (1.5)^^(8/3) (0.036)'^(1/3) = 21.4 CFS 0.013 Qioo < Qmax OKAY Maximum Water Height In SDMH Q = CAV2g(Hw-d/2 + Va/2g)''1/2 8.74 = (0.62)(1.77)V 2(32.2)(Hw - 0.75) 7.96= V2(32.2)(Hw-0.75) 0.98 = Hw-0.75 Hw= 1.73 fL ^ /^g!g^ TO 3E Oa%^£ C0A>sr.9t/C-r/OM tf**»'/rK /ttf-'^^M^^^/^M'^SMl— AeajMcT' ss MOnKOKn ay 7st«r oanCL- k c Sir^t £)./W£d^Ps MUV/CJI^^ eM%n4e£es, 6.0 % e. 2.0 13 1.0 (2) hrpr^pi^^ 0) Ptpte hr|)f8«^3rtaiipli op the^r^t&idftof*® chart. .(i|) Qrawa Ine thtopgH tbe pcjtatpaiattBl to thepfatfad lines. (a) S&tec*ac! fequepcy „P,,«i_i..,P,,-ji5_,^"i5_%<^ (c) AdiustedPe^ = I (e)t = /^'^/rfevJhr. S fiftjte^ Tlie GhsHt replace Gtirvesijsecl:since t965i. PS tsz MS W7 a75 Mi tJBt 4.91 F f C tT ft &• Intensity-Duration Design Chart - Template ( -1.5'- 2% Concrete Gutter RESIDENTIAL STREET ONE SIDE ONLY 7 8 9 10 Discharge (C.F.S.) 40 50 EXAMPLE: Given: Q = 10 S = 2.5% Chart gives: Depth = 0.4, Velocity - 4.4 f.p.s. 'URGE; San Diego County Department of Special District Services Design Manual F I G U R L Gutter and Roadway Discharge - Velocity Chart County of San Diego Hydrology Manual o CO 6 t^ O i o ; o in Oi CO o PO Q CP If) o CO • 33° 15' SS'OO' 32°45' 32°30' County of San Diego Hydrology Manual Ik Rainfall Isopluvials 100 Year Rainfall Event - 6 Hours DPW GIS .1 GIS \.K-'c Hav-i: San TJicgn Covered! N THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND. EITHER EXPRESS OR IMPLIED. INCLUDING, BUT NOT LIMITED TO. THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Copyright SanGIS. All Rights Reserved. This products may contain Infomiation from the SANDAG Regional Information System which cannot be reproduced without the written permission of SANDAG. This product may contain information which has been reproduced vvith permission granted by Thomas Brokers Maps. 3 Miles 33°30^ 33°30' 33° 15' 33°00 32°45 32°30' County of San Diego Hydrology Manual Rainfall Isopluvials 100 Year Rainfall Event - 24 Hours DPW GIS Departmsnr sf Public Works GIS Wc Ha.vc San Dicijcj Coveted'. N THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO. THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICUUR PURPOSE. Copyright SanGIS. All Rights Resen/ed. This products may contain information from the SANDAG Regional P* Information System which cannot be reproduced without the written pemiission of SANDAG. This product may contain information which has been reproduced with permission granted by Thomas Brothers Maps. 3 Miles