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HomeMy WebLinkAboutCDP 2020-0017; SAREM RESIDENCE; HYDROLOGY STUDY; 2021-05-26 HYDROLOGY STUDY SAREM RESIDENCE 4005 Skyline Road, Carlsbad, CA City of Carlsbad Project No.: CDP 2020-0017 GR 2021-0016 / DWG 531-1A Prepared for: Mr. & Mrs. Scott Sarem 6684 Lemon Leaf Drive Carlsbad, CA 92011 Tel: (760) 533-2470 Prepared by: Toal Engineering, Inc. 139 Avenida Navarro San Clemente, CA 92672 Tel: (949) 492-8586 Fax: (949) 498-8625 May 26, 2021 ……………………………………………………… Caleb O. Rios R.C.E. 57587 JN 20036 1.0 PURPOSE This report has been prepared to accompany the Grading Plan for the proposed construction of a new single-family residence at 4005 Skyline Road (Por. Lot 24, Map 2647 / Carlsbad Heights) (City of Carlsbad Project No.: CDP 2020-0017). 2.0 DESCRIPTION OF SITE The subject lot is a partially-developed, rectangular-shaped 0.572-acre (24,904 sq. ft.) residential property. The building and appurtenant features associated with the existing residential development are primarily located on the easterly half of the property, with the westerly half consisting of a brush covered slope. The existing on-site impervious area measures 5,000 sq. ft. (or ~20% of the project site). The property is bounded on the North, South, and West by similar residential development, and to the East by Skyline Road (public street). 3.0 EXISTING DRAINAGE All site runoff, and an ~10’ wide section of the Skyline Road right-of-way (~1,000 sq. ft. total; 55% impervious), flows across the surface of the project property in a westerly direction and onto the neighboring properties to the west; total existing project drainage area to Sunnyhill Drive = 25,904 sq. ft. (0.595 ac), with 5,550 impervious (21%). The remaining portion of Skyline Road flows in a southerly direction along both sides of the asphalt roadway. Site runoff draining onto the adjacent westerly properties ultimately reaches Sunnyhill Drive, then flows northerly (from the street high point at the south corner of 4020 Sunnyhill Drive) before entering the City storm drain system via curb inlet catch basin near the intersection of Sunnyhill Drive and Alder Avenue. 4.0 PROPOSED DEVELOPMENT The developer proposes to construct a 4,800-sq. ft. residence with ~9,700 sq. ft. of additional impervious surfaces (driveway, walkways, stairs, etc.) across the entire project. The impervious surface area within the parcel is 14,100 sq. ft. (57% of parcel area). The proposed improvements are shown on the construction plans for the project, including the Grading Plan referenced above. 5.0 PROPOSED DRAINAGE A ridge will be created at the Skyline Road right-of-way, intended to keep all off-site storm water in the street. All runoff from the subject property will be collected, treated (see separate SWQMP report), then outlet onto ground level (via perforated underdrain pipe with pop-up emitters) at the rear of the lot, and ultimately discharged to Sunnyhill Drive via surface flow across 4020 Sunnyhill Drive (existing drainage pattern). Drainage improvements are designed to limit the post-project discharge rate to match the existing condition, thereby eliminating any impact to downstream City storm drain improvements. The proposed drainage system is designed to address the 100-yr storm. 6.0 METHODOLOGY The purpose of the calculations presented herein is to analyze the pre- and post-project drainage characteristics for 4005 Skyline Road. For both conditions, we performed a rational method hydrologic analysis based on the San Diego County Hydrology Manual. Post-project peak runoff quantities at the westerly edge of the project property were compared to the pre-project values. See Appendix A for tables and charts from the Hydrology Manual. The Drainage Map in Appendix B graphically depicts the project watershed and data relevant to the runoff calculations. 7.0 RESULTS AND ANALYSIS Our hydrologic and hydraulic analysis of 4005 Skyline Road yielded the following results: Table 1. Peak Runoff. Condition Frequency Imp % C Tc (min.) I (in./hr) A (acres) Q100 (cfs) Pre-project 100-yr 21 0.38 6.8 5.8 0.595 1.31 Post-project 100-yr 57 0.62 5.0 7.1 0.572 2.52 Table 2. Peak Volume. Condition Q100 (cfs) ∆Q100 Tc (min.) Volume (ft3) Peak Pre-Project 1.31 Peak Post-Project 2.52 +1.21 5.0 363 Post-Project Peak – 1Tc 0.72 -0.59 N/A N/A The values for ‘C’ in Table 1 are representative of the impervious surface areas within the drainage boundary for each location (see Table 3-1 and Hydrology Calculations). The ‘Tc’ information in Table 1 is based upon initial times of concentration per Table 3-2, and the Tc equation on Figure 3.4 (existing condition only); as the developed condition Tc is less than the minimum allowable Tc of 5 minutes, the post-project Tc shall be set at 5.0 minutes. The values for ‘I’ in Table 1 are from Figure 3-1, and are based upon times of concentration ‘Tc’. See Appendix A for all calculations, tables, and figures. As shown in Table 2, only the peak of the post-project storm exceeds the flowrate of the existing 100-yr storm event (Post-project peak – 1Tc calculated per Section 6 of the San Diego County Hydrology Manual). To match the peak pre-project flowrate of 1.31 cubic feet per second (cfs), the project drainage system must employ flow control measures and provide 363 cu. ft. of water storage (minimum) during the 100-yr peak; see stage storage analysis in Appendix A. 8.0 CONCLUSIONS Toal Engineering, Inc. proposes the use of volume control to limit off-site discharge to 1.31 cfs, by implementing off-line storage on the project site to detain the peak volume of 363 cu. ft. that exceeds the controlled discharge rate of 1.31 cfs. I I I I I I I 1--------1 --t--- APPENDIX A Calculations HYDROLOGY CALCULATIONS 4005 Skyline Road, Carlsbad, CA Pre-project Condition: Project Information: Total drainage area = 25,904 sq. ft. (0.595 ac; incl. 1,000 sq. ft. of Skyline Road right-of-way) Impervious area = 5,500 sq. ft. (21%) Land Use = Low Density Residential (LDR) – 2.0 DU/A or less Soil Type = NRCS Type B Runoff Coefficient (C) = 0.38 – Table 3-1 of San Diego County Hydrology Manual (SDCHM) Surface slope across first 100 feet = ~10% Initial Time of Concentration (Ti) = 5.8 minutes – per Table 3-2 of SDCHM 6-Hour Precipitation (P6) = 2.7 inches – per 100-yr, 6-Hour Isopluvial in SDCHM Appendix B Calculations: Runoff Travel Time (Tt) = [11.9 * (195 ft. * 1 mi./5,280 ft.)3 / 25 ft.]0.385 * 60 min./hr. = 1 min. Per Equation on Figure 3-4 of SDCHM Tc = Ti + Tt = 5.8 minutes + 1 minute = 6.8 minutes I = 7.44 * 2.7 inches * (6.8 minutes)-0.645 = 5.8 in./hr. - per Equation on Figure 3-1 of SDCHM Q100 = C * I * A = 0.38 * 5.8 in./hr. * 0.595 ac = 1.31 cfs Post-Project Condition: Parcel Information: Total drainage area = 24,904 sq. ft. (0.572 ac; no Skyline Road right-of-way) Impervious area = 14,100 sq. ft. (57%) Land Use = between Medium Density Residential (MDR) and High Density Residential (HDR) Soil Type = NRCS Type B Runoff Coefficient (C) = 0.62 – per C Calculation on Page 3-5 of SDCHM (calculation below) (CP) = 0.25 – Natural Open Space (0% Impervious) per Table 3-1 of SDCHM Surface slope across first 100 feet = ~10% Initial Time of Concentration (Ti) = 3.9 minutes – per Table 3-2 of SDCHM (calculation below) 6-Hour Precipitation (P6) = 2.7 inches – per 100-yr, 6-Hour Isopluvial in SDCHM Appendix B Calculations: C = 0.90 * %Impervious + CP * (1 - %Impervious) = 0.90 * 0.57 + 0.25 * 0.43 = 0.62 Ti = Avg of MDR 14.5 and HDR 24 = (4.3 min. + 3.5 min.) / 2 = 3.9 minutes Runoff Travel Time (Tc) = 5 min. (minimum per SDCHM; used due to initial Tc < 5 minutes). I = 7.44 * 2.7 inches * 5.0 minutes)-0.645 = 7.1 in./hr. - per Equation on Figure 3-1 of SDCHM Q100 = C * I * A = 0.62 * 7.1 in./hr. * 0.572 ac = 2.52 cfs Verify that Q100 only exceeds the pre-project condition at the hydrograph peak by checking the unit immediately preceding the peak (Q100 – 1Tc) per Section 6 of the SDCHM: PT1 = 0.124 * 2.7 inches * (1 * 5 minutes)0.355 = 0.59 inches PT2 = 0.124 * 2.7 inches * (2 * 5 minutes)0.355 = 0.76 inches P2 = PT2 - PT1 = 0.76 inches - 0.59 inches = 0.17 inches I2 = 60 * (P2 / Tc) = 60 * (0.17 inches / 5 min.) = 1.98 in./hr. Q2 = C * A * I2 = 0.62 * 0.572 ac * 1.98 in./hr = 0.70 cfs …… < 1.31 cfs….OK Calculate storage volume required to maintain peak discharge at 1.31 cfs (Q100 Pre) V = (Q100 Post – Q100 Pre) * Tc = (2.52 cfs – 1.31 cfs) * 5 min. * (60 sec./1 min.) = 363 cu. ft. 100-YEAR POST-PROJECT HYDROLOGIC ANALYSIS - SITE ONLY SAN DIEGO COUNTY HYDROLOGY MANUAL RATIONAL METHOD HYDROGRAPH DEVELOPMENT Q = C * I * A C = 0.62 Area (A; acres) = 0.572 I = 7.44 * P6 * D^‐0.645 Per SDCHM (where D = duration in minutes) Tc (min.) = 5 (minimum per SDCHM) P6 (in.) = 2.7 PART 2. HYDROGRAPH DEVELOPMENT Peak Design Design Design Cumulative Rainfall Net Discharge Storm Storm Storm Discharge Runoff Runoff Unit Time Rainfall Intensity Q Time Time Time Q Volume Volume Number (Minutes)(Inches)(In/hr)(cfs) (Minutes)(Minutes)(Hours)(cfs) (cf) (cf) 1 5 0.59 7.11 2.52 240 0 0.000 0.06 0.0 0.0 2 10 0.76 1.98 0.70 235 5 0.083 0.06 17.3 17.3 3 15 0.88 1.41 0.50 230 10 0.167 0.06 17.6 34.9 4 20 0.97 1.13 0.40 245 15 0.250 0.06 17.8 52.6 5 25 1.05 0.96 0.34 225 20 0.333 0.06 18.1 70.7 6 30 1.12 0.84 0.30 220 25 0.417 0.06 18.3 89.0 7 35 1.18 0.76 0.27 250 30 0.500 0.06 18.7 107.7 8 40 1.24 0.69 0.24 215 35 0.583 0.06 18.9 126.5 9 45 1.29 0.64 0.23 210 40 0.667 0.06 19.3 145.8 10 50 1.34 0.59 0.21 255 45 0.750 0.06 19.5 165.2 11 55 1.39 0.55 0.20 205 50 0.833 0.07 19.9 185.2 12 60 1.43 0.52 0.19 200 55 0.917 0.07 20.1 205.3 13 65 1.47 0.50 0.18 260 60 1.000 0.07 20.6 225.9 14 70 1.51 0.47 0.17 195 65 1.083 0.07 20.9 246.8 15 75 1.55 0.45 0.16 190 70 1.167 0.07 21.4 268.2 16 80 1.59 0.43 0.15 265 75 1.250 0.07 21.7 289.9 17 85 1.62 0.41 0.15 185 80 1.333 0.07 22.3 312.2 18 90 1.65 0.40 0.14 180 85 1.417 0.08 22.6 334.8 19 95 1.69 0.38 0.14 270 90 1.500 0.08 23.2 358.0 20 100 1.72 0.37 0.13 175 95 1.583 0.08 23.6 381.6 21 105 1.75 0.36 0.13 170 100 1.667 0.08 24.3 405.9 22 110 1.78 0.35 0.12 275 105 1.750 0.08 24.7 430.6 23 115 1.80 0.34 0.12 165 110 1.833 0.09 25.5 456.1 24 120 1.83 0.33 0.12 160 115 1.917 0.09 25.9 482.0 25 125 1.86 0.32 0.11 280 120 2.000 0.09 26.9 508.9 26 130 1.88 0.31 0.11 155 125 2.083 0.09 27.4 536.3 27 135 1.91 0.31 0.11 150 130 2.167 0.09 28.5 564.7 28 140 1.93 0.30 0.11 285 135 2.250 0.10 29.0 593.7 29 145 1.96 0.29 0.10 145 140 2.333 0.10 30.3 624.0 30 150 1.98 0.28 0.10 140 145 2.417 0.10 31.0 655.0 31 155 2.01 0.28 0.10 290 150 2.500 0.11 32.5 687.4 32 160 2.03 0.27 0.10 135 155 2.583 0.11 33.3 720.7 33 165 2.05 0.27 0.09 130 160 2.667 0.12 35.1 755.8 20036‐detention 1 of 2 5/26/2021 Peak Design Design Design Cumulative Rainfall Net Discharge Storm Storm Storm Discharge Runoff Runoff Unit Time Rainfall Intensity Q Time Time Time Q Volume Volume Number (Minutes)(Inches)(In/hr)(cfs) (Minutes)(Minutes)(Hours)(cfs) (cf) (cf) 34 170 2.07 0.26 0.09 295 165 2.750 0.12 36.1 791.8 35 175 2.09 0.26 0.09 125 170 2.833 0.13 38.3 830.1 36 180 2.12 0.25 0.09 120 175 2.917 0.13 39.6 869.7 37 185 2.14 0.25 0.09 300 180 3.000 0.14 42.4 912.1 38 190 2.16 0.24 0.09 115 185 3.083 0.15 44.1 956.2 39 195 2.18 0.24 0.09 110 190 3.167 0.16 47.9 1004.1 40 200 2.20 0.24 0.08 305 195 3.250 0.17 50.2 1054.2 41 205 2.22 0.23 0.08 105 200 3.333 0.19 55.6 1109.8 42 210 2.23 0.23 0.08 100 205 3.417 0.20 59.0 1168.8 43 215 2.25 0.22 0.08 310 210 3.500 0.23 67.6 1236.4 44 220 2.27 0.22 0.08 95 215 3.583 0.24 73.3 1309.7 45 225 2.29 0.22 0.08 90 220 3.667 0.30 89.6 1399.4 46 230 2.31 0.22 0.08 315 225 3.750 0.34 102.1 1501.4 47 235 2.33 0.21 0.08 85 230 3.833 0.50 149.9 1651.3 48 240 2.34 0.21 0.07 80 235 3.917 0.70 211.2 1862.4 49 245 2.36 0.21 0.07 320 240 4.000 2.52 756.9 2619.3 50 250 2.38 0.20 0.07 75 245 4.083 0.40 120.2 2739.5 51 255 2.39 0.20 0.07 70 250 4.167 0.27 80.4 2819.9 52 260 2.41 0.20 0.07 325 255 4.250 0.21 62.9 2882.8 53 265 2.43 0.20 0.07 65 260 4.333 0.18 52.7 2935.5 54 270 2.44 0.19 0.07 60 265 4.417 0.15 45.9 2981.4 55 275 2.46 0.19 0.07 330 270 4.500 0.14 40.9 3022.3 56 280 2.47 0.19 0.07 55 275 4.583 0.12 37.1 3059.5 57 285 2.49 0.19 0.07 50 280 4.667 0.11 34.1 3093.6 58 290 2.51 0.19 0.07 335 285 4.750 0.11 31.7 3125.3 59 295 2.52 0.18 0.06 45 290 4.833 0.10 29.6 3154.9 60 300 2.54 0.18 0.06 40 295 4.917 0.09 27.9 3182.8 61 305 2.55 0.18 0.06 340 300 5.000 0.09 26.4 3209.2 62 310 2.57 0.18 0.06 35 305 5.083 0.08 25.1 3234.3 63 315 2.58 0.18 0.06 30 310 5.167 0.08 23.9 3258.2 64 320 2.59 0.17 0.06 345 315 5.250 0.08 22.9 3281.1 65 325 2.61 0.17 0.06 25 320 5.333 0.07 22.0 3303.1 66 330 2.62 0.17 0.06 20 325 5.417 0.07 21.1 3324.3 67 335 2.64 0.17 0.06 350 330 5.500 0.07 20.4 3344.6 68 340 2.65 0.17 0.06 15 335 5.583 0.07 19.7 3364.3 69 345 2.67 0.17 0.06 10 340 5.667 0.06 19.1 3383.4 70 350 2.68 0.16 0.06 355 345 5.750 0.06 18.5 3401.9 71 355 2.69 0.16 0.06 5 350 5.833 0.06 17.9 3419.8 72 360 2.71 0.16 0.06 0 355 5.917 0.06 17.4 3437.2 20036‐detention 2 of 2 5/26/2021 HORIZONTAL PIPE DETENTION BASIN CALCULATOR Qp‐post 2.52 Tc 5 orifice dia, (ft)0.47 Korifice 3.78 Vault W, ft 4.0 Vault H, ft 3.0 Vault L, ft 30.5 Vault Afull, ft2 12.0 Max storage vol, cf 366 Design Vol Vol Storm Inflow Runoff Vol in based based actual actual remain HHQ Time Q Volume basin outflow vol out outflow vol out vol in ft orifice (Hours) (cfs) (cf) (cf) (cfs) (cf) (cfs) (cf) (cf) 0 0.00 0.00 3.50 0.225 68 68 1.173 352 0.23 68 0 1 0.08 0.24 3.58 0.244 73 73 1.197 359 0.24 73 0 2 0.17 0.34 3.67 0.299 90 90 1.267 380 0.30 90 0 3 0.25 0.41 3.75 0.340 102 102 1.311 393 0.34 102 0 4 0.33 0.48 3.83 0.500 150 150 1.311 393 0.50 150 0 5 0.42 0.54 3.92 0.704 211 211 1.311 393 0.70 211 0 6 0.50 0.59 4.00 2.523 757 757 1.311 393 1.31 393 363 7 0.58 0.63 4.08 0.401 120 484 1.311 393 1.31 393 90 8 0.67 0.68 4.17 0.268 80 171 1.311 393 0.57 171 0 9 0.75 0.72 4.25 0.210 63 63 1.148 344 0.21 63 0 10 0.83 0.76 4.33 0.176 53 53 1.123 337 0.18 53 0 11 0.92 0.79 4.42 0.153 46 46 1.071 321 0.15 46 0 12 1.00 0.83 4.50 0.136 41 41 1.044 313 0.14 41 0 13 1.08 0.86 14 1.17 0.90 15 1.25 0.93 16 1.33 0.96 17 1.42 0.99 18 1.50 1.02 19 1.58 1.04 20 1.67 1.07 21 1.75 1.10 22 1.83 1.12 23 1.92 1.15 24 2.00 1.17 25 2.08 1.20 26 2.17 1.22 27 2.25 1.24 28 2.33 1.27 29 2.42 1.29 30 2.50 1.31 PREC = 0.90 * %Impervious + CP * (1 - %Impervious) = 0.90 * 0.57 + 0.25 * 0.43 = 0.62(per Page 3-5 of SDCHM)CPSan Diego County Hydrology Manual Date: June 2003 Table 3-1 Section: Page: RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use I Runoff Coefficient '·C'' Soil T}'.ee NRCS Elements Coun Elements % IMPER. A B Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 I 0.2s I Low Density Residential (LOR) Residential, l.O DU/A or less 10 0,27 0.32 Low Density Residential (LOR) Residential, 2.0 DU/A or less 20 0.34 I o.38 I Low Density Residential (LOR) Residential, 2.9 DU/A or less 25 0.38 0.4 I Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 Medium Density Residential (MOR) Residential, 7.3 DU/A or less 40 0.48 0.51 Medium Density Residential (MOR) Residential, I 0.9 DU/A or less 45 0.52 0.54 Medium Density Residential (MOR) Residential. 14.5 DU/A or less 50 0.55 0.58 High Density Residential (HOR) Residential, 24.0 DU/A or less 65 0.66 0.67 High Density Residential (HOR) Residential, 43.0 DU/A or less 80 0.76 0.77 Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80 Commercial/Industrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 Commercial/Industrial (Limited L) Limited Industrial 90 0.83 0.84 Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 C 0.30 0.36 0.42 0.45 0.48 0.54 0.57 0.60 0.69 0.78 0.78 0.81 0.84 0.84 0.87 3 6 of26 D 0.35 0.41 0.46 0.49 0.52 0.57 0.60 0.63 Q.71 0.79 0.79 0.82 0.85 0.85 0.87 *The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1 f (representing the pervious runoff coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will tmain natural forever (e.g .. the area is located in Cleveland National Forest). DU/A= dwelling units per acre NRCS = National Resources Conservation Service 3-6 3.9 AVG San Diego County Hydrology Manual Date : June 2003 Section: Page: 3 12 of26 Note that the Initial Time of Concentration should be reflective of th general land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres. Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in hydrology studies. Initial Ti values based on average C values fo r the Land Use Element are also included. These values can be used in planning and design applications as described below. ~xceptions may be approved by the 'Regulating Agency" when submitLed wi th a detailed study, Table 3-2 MAXIMUM OVERLAND FLOW LENGTH (LM) & INITIAL TIME OF CONCENTRATION (Ti) Element* DU/ .5% 1% 2% 3% 5% 10% Acre LM Ti LM Ti LM Ti LM Ti LM Ti LM T1 Natmal 50 13.2 70 12.5 85 10.9 100 10.3 100 8,7 100 6.9 LOR l 50 12.2 70 11.5 85 10 .0 100 9.5 100 8.0 100 6.4 LOR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8 LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6 MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 LOO 5.3 MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 so 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5 MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3 HOR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5 HOR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 100 2,7 N.Com so 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 G.Com. 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Com 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 General I. 50 3 .7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9 * See Table 3-1 fat more detailed description 3-12 10.0 9.1 8.1 7.1 l N ........... "h... ""ll-J. : '-I "-.!" 'i-. 11' )N. "'-!.."r--...~N.'r-. i' l'!-J ... 7'r-J ~r-6.1 s., 4.' ... I {J 'r--.. J'~ I J'r-. 1 , I " "r-,.1 r-. I K ,~ "' I ... , ~ 3.0 I " I'---., I ... .... ~ , r-..., I , 'r-,..1 I -.. . 1-l I I I I I I ! ""r-I I " "' 1' ' 1-...:... ~ I I I I ,. ~ i... I I•~ 1' I .. rt-l i-l I "' 11 ~ ~ I I'-• ..... ' I r-. -!.. ~ "'' ,, ' ~ J . i I I , II Ir-1t ... I I 'rt I ~ ... l I I I I I 11 I I I I I I I I 1 11 I I I I I l I I I I I l EQUATION l I = 7.44 P5 D-0.645 I I ~ I I I =-Intensity (in/hr) Ii P5 = 6-Hour Precipitation (in) t '~ D = Duration (min) I I ~r-l ' ~ 1 I I '· 1-. ,, !~ i;. I r-;..',I I I } { I l i-, tf ~ I l ~ i:. l ~I'-. It "! ,; I ,, ,, 2.0 I 'k I r ... Jl .. t I I ' ! ... I • l 11'-.I" ,r-.' I 'r---... '', ;;;) 0 £ ,n a, .c -~ 1.0 ~0.9 ·~o.s a, co.1 0.6 i i 0.5 OA . 0.3 i I -·-- I I I i I r l l -· ·--' ' _;.:p· ·r- 0.2 ' I ,, : I -·----,__ _j I ---77-0,1 I I I I I ---I - I I I -r- -~-- 5 6 7 8 9 10 --~~ ... "'., { ~rl-l 'r-- ... II ~ ' ... , • I ,LI I I II • I I 11 I I I I l I I I I I I -1 -----r I ---'r .t I I _J_ --' ------~ -.. -7--. T 15 20 3·0 Minutes I 1' ' I I I ,;. ..... ~ ' ', 1-... ... '· . 'N. ~ ' ' "' "i... ' p•, I l I i-.., I, 'ITT • I I I '1 I ,· ' "", ... I 1, i-.., ,, . I '•~ ~ t~ I I ' ""i-. I ~ I ~ i", i " ' i' "'~ I I I .. , I .... , I i-I I l I I' 7 ~ '1' I t I I ,1 I I \ I I '.J ...... I • .. I I , ~ I , ~ I l I I" I' ...... ...~ t I ' ... I • ~ 'I l I ,, , .... ~ -. I I I I I r .... I • j I ]' ' ..... , ll j .. , I I f I ~ ---- I ---=----~---. -t 1- _, !·· -f I --. t I I If I I r -+-I -.. ---I I -----.. j' ·----- ------- ---I I I ------1 4'0 50 2 3 4 S 6 Hours Duration Cl :r: 0 !:; "O ii, Q , 6.0 'E. 5.5 §I 5.0 g· 4.5 S" n 4.0 i5' 3,5 .e 3.0 2.5 2.0 1.5 , .0 Intensity-Duration Design Chart -Template Directions for Application: (1) From precipitation maps determine 6 hr and 24 hr amounts for the selected frequency. These maps are included 1n the County Hydrology Manual (10. 50. and 100 yr maps Included in the Design and Procedure Manual). (2) Adjust 6 hr precipitation (if necessary) so that it Is within the range of 45% to 65% of the 24 hr precipitation (not applicaple to Desert). (3) Plot 6 hr precipitation on the right side of the chart. (4) Draw a line through the point parallel to the plotted lines. (5) This line is the intensity-duration curve for the location being analyzed. Application Form: (a) Selected frequency ___ year (b) P6 = ___ in., P24 = ___ ,;6 = ___ %(2) 24 (c) Adjusted P6(2> = ___ in. (d) Ix = ___ min. (e) I = ___ in./hr. Note: This chart replaces the Intensity-Duration-Frequency curves used since 1965. P6 , 1 .s 2 2.5 3 3.5 4 4,5 5 5.5 6 Duration I I I I I I I I I I I 5 2,63 3.95 5.27 6.59 7.90 9.22 10.5•1 .11.86 13.17 14.49 15.8 1 10.60 11.66 12,72 7 2.12 3.18 4.24 5.30 6.36 7.42 8.48 9.54 10 1.68 2.53' 3.37 4,21 . 5,05 5.90 6.74 7.58 8.42 9.27 10 11 15 1.30 1.95-2.59 3.24 -3.89-•L54 5.19 5.84 6A9 7.13 7.78 20 1.08 1.62°2 15 2.69 323:3.77 4.31 4.85 5.39 5.93 6.46 25 0.93 1.40 1 87 2.33 2,80 -3.27 3.73 .,.2·0 4.67 5.13 5.60 30 0.83 1.24 I 66 2,07 2.49 2.90 3.32 3.73 4.15 4.56 4.98 40 0.69 1.03 1.38 1. 72 2 07 2.4 1 2.76 3.10 3.45 3.79 4,13 50 0.60 0.90 1.19 1.49 1.79 209 2.39 2.69 2.98 3.28 3.58 60 0.53 0.80 1.06 1,33 1 .59. 1 86 2 12 2.39 2.65 2.92 3,18 90 0.41 0.61 0.82 1.02 1.23 1.43 1 63 1.84 2.04 2.25 2,45 120 -0 3.1 0.51 0.68 0.85 1.02 1 19 1.36 1,53 1.70 1 87 2,().1 150 0,29 0,44 0.59 0, 73 0.88 1.03 1.18 1.32 1..17 1.62 1.76 180 0,26 0.39 0,52 0.65 0.78 0.91 1 04 1.18 I 1.31 1.4·1 1 57 240 0.22 0.33 0.43 0.54 0,65 o. 76 0 87 0 98 1,08 1.19 1.30 300 0.19 '02e·o.3e 0.47 o.56 o.66 o.75 0,85 I 0.94 1.03 1 13 360 0.17 0.25, 0.33 0.42 0.50 0,58 0.67 0.75 0.64 0.92 1.00 FI GURE ~ Feet 5000 4000 Tc Tc L .6.E = = = = EQUATION (1~~3)°,385 Time of concentration (hours) Watercourse Distance (miles) Change in elevation along effective slope line (See Figlffe 3-5) (feet) .6 E 3000 2000 400 300 200 100 50 40 30 20 10 5 SOURCE: California Division of Highways (1941) and Kirpich (1940) L MIies Feet ' 3000 0.5 '\ 2000 1800 1600 1400 1200 1000 900 800 700 600 500 400 300 200 L ' Nomograph for Determination of ' ' Tc Hours Minutes 4 3 2 ' ' ' Tc 50 40 30 20 18 16 14 12 10 9 8 7 6 5 4 3 Time of Concentration (Tc) or Travel Time (Tt) for Natural Watersheds FIGliRll; 3-4 Project Site + b C") 0 ,.._ 'C ..... "'O ()} 0 .,.,. .. """"' ip ..... 0 "" ..--~ b 0 ..... = ,.... -. ..;..f.._.: ....... _ ... .. _ .,._ .......... , ----- ~ 0 C") o. 0 (0 co .... =--.... .... .. to ,.... 0 co =-- -+- ---1 . ' ' ' 33"30' 33•00· ------1---=.,.,.=..o~· ----=:-:--:-:-:-:-::-:--::EW;F,¥-'-f=-=-1.-'=,}.-¾--Jr4-~~~L.;z. _ _j'=<..:.:::=-----!-:---i-__;__-~(}-~~--4---~,-------------+-~-Z· ·--~--s3•00· :s_,p,: c~_UN,Y.,: ,_• -32°45' --32°30' b M 0 ,.._ .... .... to ,.... 0 ..... ,.... .= e a 0 ..... ,-.... ro '<I" 0 t0 ,-,- : •• t,.., .· ." \,, ' ' ' . ' ' . . • < • 1 I I .. ,._. '\ \ ~ "Q · ......... -"' '\ \ ... ·' .... \ '._.< . M e X I ' . . . . -.. . ... -·····: .... _ .. . ' ' ... .... t .... , ......... •. 'l,·r-',,.·:-., (.\) . ... , ............ ·, .. , .. " -~ .... .. .. .. "-1"' "to ............... , ·._ • .. ~.~-. "',\ \ ' I • I 1 .. ' -• I I I I ; I g Q __ co ,... ,- . ' it) ..... 0 (0 -= ..- .~,•t- .--•'l::f'&·· 3 -0 (D -, ~ 32°30' County of San Diego Hydrology Manual Rainfall Isopluvials 100 Year Rainfall Event -6 Hours ls.opluvial {inches) DPW ~GIS ,O~i!'nfof P.:1h.i;-W.:ri.'.i ~ /11fcim<1/J:,rrS71,<ttPS s1fGIS We Ha.vs'.: San Di .. -g,, Cnvcrcd.! nus MAP 1S PROVIDED WITHOUT WARRANTY OF ANY KINO. ErTHER EXPRESS OR IMPUED, IOICWOI NO, Bl/T NOT LIMITED 'TO. THE IMPLIED WARRANTIES OF MERCHANTABILITY AND• FITNESS FOR APARTfCULAR PURPOSE. Cowlohl SonGIS. All Right, Rs'"""'d. 1NI producu may contain lnrormBtlon frcm the SANDAG Reg,on~ lnfonnatlon Sydsm whleh t:annOI be ~ 'wilnOlrt tno -.,itl:en pemil&slm of SANDAG. Thia p,oduel may """'8/n Jnlonnellon which hos been "'1)/Udue«I ,.;u, po,mlss/on gn1n1Gd byThomas Bnlll1ffl Mops. Miles !"^$ !"_$ Aù %&s( !"a$!"^$ !"^$ A© %&s( ?z Aª A¨ Aª Aª AÀ A¨ A¨ A© A© !"a$ !"_$ !"_$ !"_$ A© AÀ %&s(?j ?jA×AÀ ?h ?h AÀ AÀ AÛ !"_$ ?z !"_$?z !"a$ A¨ !"a$ !"^$ VISTA POWAY SANTEE LA MESA DEL MAR CORONADO EL CAJON CARLSBAD OCEANSIDE ENCINITAS SAN DIEGO ESCONDIDOSAN MARCOS CHULA VISTA LEMON GROVE SOLANA BEACH NATIONAL CITY IMPERIAL BEACH 116°15'0"W 116°15'0"W 116°30'0"W 116°30'0"W 116°45'0"W 116°45'0"W 117°0'0"W 117°0'0"W 117°15'0"W 117°15'0"W 117°30'0"W 117°30'0"W 33°30'0"N33°30'0"N33°15'0"N33°15'0"N33°0'0"N33°0'0"N32°45'0"N32°45'0"NCounty of San Diego Hydrology Manual Soil Hydrologic Group Legend Major Roads Incorporated City Bdy HYDROLOGIC SOIL GROUP Hydrologic Group Undefined Hydrologic Group A Hydrologic Group B Hydrologic Group C Hydrologic Group D No Soil Data THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND,EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITEDTO, THE IMPLIED WARRANTIES OF MERCHANTABILITY ANDFITNESS FOR A PARTICULAR PURPOSE.Copyright SanGIS. All Rights Reserved. This product may contain information 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 with permission granted by Thomas Brothers Maps. Note: Soil Data Source USDA/NRCS SSURGO Soils 2007 ±3031.5 Miles Riverside County Pacific OceanImperial CountyMexico Orange County Project Site - - D DPW ~GIS r~.,..~"'!~'"....,.1-.",,._, ..... .,.. ....................... ~.-- APPENDIX B Drainage Map XXXXXXXXX X X X XXXXXXXXXXXXXXXXXXXXX27527528028028528529029029529530030530530030'LEGEND\ \ \ 0 0 20 40 SCALE: 1 "= 20' CD 0.253 AC ap=0.444 ~ ... SUBAREA DESIGNATION AREA IN ACRES PERVIOUS AREA FRACTION RUNOFF FLOW DIRECTION 1 -1 SUBAREA BOUNDARY L_ _ _J I ( I I I \ EXIST\~IDGE I \ SKYLINE\ ROAD . W ~ r I ··: .. ·. -~ ··: I, .·• ~ . . ~ : ... ~~-. · .. • 7-. ,:. .. ...... ·. ..... ~ ~ FIGURE ~ PRE-PROJECT HYDROLOGY MAP A. 1 o :: JOB NO.: 20036 MAIN LEVELT/SLAB=298.32PAD=297.652-CARGARAGE1-CARGARAGEGYMT/SLAB=299.82PAD=299.15POOLBY OTHERS30'DETAILDETENTION / FLOW CONTROL SYSTEMLEGEND• ~ I I ,\ ( I \ ~,l ( \ I \ I ~' \ \ \ \ BIOFILTRATION BMP TERNAL WITHIN D LID BMP F UNDERGROUND STORM WATER DETENTION (363 CU. FT. MIN.) I I I (!1f I I e• a.EANOUT DRAINAGE BOUNDARY AND PROPERlY LINE NODE 10 ELEV. = 297.7' Tc = 4.5 min. 0 0.57 ap= PROPOSED RESIDENCE 8° WllE CHNIE. \_' W/ 2" HIGH WEIi -8" OUT (10 DRIIINAGE ~"'.1"'1""{!~~~~~~~~"""°3~~~ SPRE'ADER); PIPE :;...-:::;4 1.D.-5.82" AT OPENNG __:r -,,--.\J~ .,.,-(OR ENGINEER APPRl1t'ED EQI.W.; ROl'AlED FOR CIMllY)-~ CD 0.253 AC ap=0.444 r---, L.. -...J NODE 10 ELEV.=310.0 \ ~ \ --•• •4 L .. .· .. ··: 1r---0 2f--O -------j40 ·: ·.:· .. ·1 I ~ I · .. '. \ if-\ SCALE: 1 "= 20' SUBAREA DESIGNATION AREA IN ACRES PERVIOUS AREA FRACTION RUNOFF FLOW DIRECTION SUBAREA BOUNDARY POST-PROJECT HYDROLOGY MAP l I I I ' FIGURE 8.10 JOB NO.: 20036 C, • ~ 0 I e ~ .c I U) I"') 0 0 N e;i 0 e I Ill 1:'. 0 C. Cl) a:: U) I"') 0 0 N )( )( 0 0 N :z :::I! a.. IO I"') i,.i N i,.i csi 0 N U) N IO