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HomeMy WebLinkAboutCDP 2019-0032; TELESCOPE HOUSE: BUILD NEW SFR; HYDROLOGY AND STORM WATER MANAGEMENT REPORT; 2020-05-28E, CITY OF CARLSBAD ENGINEERING DIVISION HYDROLOGY AND STORM WATER MANAGEMENT REPORT FOR LOVE RESIDENCE 4615 TELESCOPE AVENUE ENGINEER OF WORK VINCENT L. SAMPO - RCE 44173 L1 :1*I1v SAMPO ENGINEERING, INC. 171 SAXONY ROAD, SUITE 213 ENCINITAS, CA 92024 (760) 436-0660 JUL 072020 LAND DEVELOPMENT ENGINEERING Telescope Ave. Sampo Engineering, Inc. Standard Development Project 5/28/2020 S Introduction: The subject property is approximately 0. 18 gross acres and is located on the westerly side of Telescope Avenue, in the City of Carlsbad. The property is currently a vacant lot. The property currently sheet flows on the surface at an approximately eight percent slope from the rear of the property to the curb and gutter on Telescope Avenue near the northeast corner of the property. The owner proposes to construct a new single family residence with an attached garage, impermeable paver flatwork, landscaping and retaining walls and other associated improvements. The area of proposed soil disturbance is 6,192 square feet. The project proposes an increase in impervious surface areas, which will result in an increase in runoff. The increase will be mitigated as described in the storm water quality summary below. This project proposes to maintain the historical drainage pattern where runoff generated onsite flows offsite from the rear of the property to the curb and gutter on Telescope Avenue. Run-on from off-site west and north neighboring properties will be collected in a brow ditch and conveyed through vegetated swales along the side yards to Telescope Ave. Hydrology Summary: A hydrology study utilizing the Rational Method was performed for the existing and proposed conditions within the area of proposed disturbance, and the results are as follows. The existing condition is calculated to have a runoff coefficient of C=0.28 and an anticipated runoff for the 100 year storm of Q=0.28 CFS. The Proposed Drainage Basin is composed of one hydrologic basin that is limited to the area of work and produces a runoff coefficient of C0.58 and an anticipated runoff for the 100-year storm of Q0.71 CFS. The project proposes an increase in impervious surfaces of 3,647 SF. Storm Water Quality Summary: The project has been determined to be a "Standard Development Project" using the City of Carlsbad Storm Water Standards Questionnaire (E-34) and is therefore exempt from priority project and hydromodification requirements. The development proposes to reduce the discharge of pollutants offsite by utilizing Source Control and Low Impact Development (LID) BMP's to the maximum extent practical. Landscaping and ground cover will be used in yard areas to prevent erosion of the surface of the soil and slopes. Impervious hardscape have been designed to disperse runoff away from structures to landscape areas before being collected in a private storm drain system. Storm water runoff will be conveyed to a proposed rip-rap energy dissipator before entering a vegetated swale system located around the property to satisfy storm water quality standards for treatment before discharging to the westerly side of Telescope Avenue. Telescope Ave. Sampo Engineering, Inc. Standard Development Project 5/28/2020 )*SAMNo. IN CL PO DRAINAGE STUDY CALCULATOR EXISTING DRAINAGE BASIN JN: 19-110 INITIALS: IQ DATE: May 28, 2020 DESCRIPTION: Area = 7,865 SF 0.18 AC (0.90)(%Impervious) + (Cp)(1-%lmpervious) = = (0.04 %)(0.9) + (0.96 %)(0.25) = 028 Q = 104.05 (Watercourse Distance, FT) S = 7.9 (Slope, %) T1 = 1.8(1.1 - C)(D)1° 1.8(1.10.35)(104.05)A1/2 = 6.91 MIN - (S)113 (79)Al/3 E2 = 1.3 (2-Year, 6-Hour Isopluvial) Eio = 1.7 (10-Year, 6-Hour Isopluvial) f 10 = - 2.6 (100-Year, 6-Hour Isopluvial) /2 = 7.44 P2 D11°°5 = 7.44(1.3(6.91)"(-0.645) 2.78 IN/HR lie = 7.44 P, D1i 5 = 7.44(1.7) (6.91)" ('-0.645) = 3.64 IN/HR !oo = 7.44 13100 D,05 = 7.44(2.6)(6.91)A(-0.645) = 5.56 IN/HR Q2 = CIA = (0.28)(2. 78 IN/HR)(0. 18 AC) = 0.14 CFS Q 10 = C I A = (0.28)(3. 64 IN/HR)(0. 18 AC) = 0.18 CFS _Qioo = CI A = (0.28) (5.56 IN/HR)(0.I8AC) = 0.28 CFS * Per San Diego County Hydrology Manual 2003 171 Saxony Road, Suite 213- Encinitas, CA 92024- P: 760-436-0660• F: 760-436-0659 info@sampoengineering.com S SAMPO ,NINJIIHL INCL DRAINAGE STUDY CALCULATOR PROPOSED DRAINAGE BASIN JN: 19-110 INITIALS: IQ DATE: May 28, 2020 DESCRIPTION: Area = 7,865 SF 018 AC * = (0.90)(%Impervious) + (Cp)(1-%Impervious) = (0.5 %)(0.9) + (0.5 %)(0.25) = 058 Q = 56.2 (Watercourse Distance, FT) S = 18.8 (Slope, %) Li - 1.8(1.1 - C)(D)12 - 1.8(1.1-0.69)(56.2,)"1/2 = 2.08 MIN - - (S)113 (18.8"l/3 IC2 = 110.38 FT x IMIN = 0.86 MIN 2 FT/S 60 SEG 2.94 MIN TcT,tI =2.94 MIN <5 MIN USE 5.00 MIN 2 = 1.3 (2-Year, 6-Hour Isopluvial) E 10 = 1.7 (10-Year. 6-Hour Isopluvial) floo = 2.6 (100-Year, 6-Hour lsopluvial) 1 2 = -0.645 - P2 D11 - 7.44(1.3(5"(-0.645) = 3.43 IN/HR Iw = 7.44 P10 D,1°645 = 7.44(1.7)(5)A(-0.645) = 4.48 IN/HR Iwo = 7.44 P100 D1 °645 = 7.44(2.6(5'(-0.645) 6.85 IN/HR 2 = CIA = (0.58) (3.43 IN/HR)(0. 18 AC) = 0.36 CFS Q w = CIA = (0.58) (4.48 IN/HR)(0. 18 AC) = 0.46 CFS Q 100 = CI A = (0. 58)(6. 85 IN/HR) (0. 18 AC) = 0.71 CFS * Per San Diego County Hydrology Manual 2003 171 Saxony Road, Suite 213• Encinitas, CA 92024• P: 760-436-0660 F: 760-436-0659 infa©sampoengineering.com BRA INA GE MA P 4615 TELESCOPE A VENUE EXISTING CONDITION ( 2876 26720 7jF 287. / ) 2R9 I IT 292. 288, C 28875 289.15 4SIM 75- 1 LI2s892ic- =0.18 AC 1289 R TC 289 20 100019 42.8FL I F97 2 289.61 20 10 0 20 40 / = SCALE 1" 20' 289.78TC 1 JN:19-11O 528.20 L±tu1 28935 FL />289.58 AMPO / •••- ENGINEERIN6, INC. I I I 121 MANY ROM, J1E 214 ENC1/1AS C4 92024 I a: (760) 4J6-C60 FAX (760) 436-0659 / / DRAINAGEMAP 4615 TELESCOPE AVENUE PROPOSED CONDITION / U1 287.67 287 20 Ti 28713 / i } /1 - I .i_---- Jo .91862U8'y 100 00, NF /268.83 TC 17. 28. -\ J.2. 29!I n / 37 TC 289.2 rJIP. •'4: . I c:: !. . •, - II' I. H 289.61 ,- . -' • 2 f_ 289.82 ' '....•t. I-... 289.7STC I / 1 289.35 FL >28958 II 18 AC 0. 71 crs ) 29P.!4 10 0 20 40 SCALE: 1" = 20' - iN. 19-110 5.28.20 EAMPO .'...'ENG INEERING, INC. 111 SAXONY ROAD, SWE 214 ENQWITAS (4 92024 M: (760) 436-Ct$60 FAX (760) 06-0659