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HomeMy WebLinkAboutTSM20-0004 Drainage Report© Copyright 2020 by California Engineering Company, Inc. No part of this document may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of California Engineering Company, Inc. ORCHARDCREST ESTATES DRAINAGE REPORT CALIFORNIA ENGINEERING COMPANY INC ESTD 1996 Prepared For: Orchardcrest Estates Subdivision Phase II Project Location: Orchardcrest Drive Oroville, CA 95965 CEC Job #: 20-207 April, 2023 ORCHARDCREST ESTATES DRAINAGE REPORT Project No.: 20-207 Page 1 of 3 Project Overview/Description The Orchardcrest Estates Project has been in existence since the mid 1990’s. Phase I was recorded and constructed around 1996. The project is located in the unincorporated area of Butte County, but is adjacent and within the City of Oroville Sphere of Limits. The property is located approximately 0.15 miles west of the Feather River, and approximately 0.12 miles north of Oro Dam Blvd. The project site currently consists of approximately 21 acres of undeveloped land which is planned to be developed into a 92-lot subdivision. The subdivision will include domestic water, sanitary sewer, storm drainage, and public streets. The area is located within two CSA’s according to the County of Butte Web Site information. CSA 026 which is designated as the Thermolito Sewer, and CSA 148 for which there has been no defined information identified from research to date. The Thermolito Master Drainage Plan was utilized as the basis for research and understanding a regional approach and guidance for this “preliminary” drainage study. A more refined study will be utilized for the final civil engineering design documents. For purposes of this this preliminary study we have chosen to utilize the Rational Method for predicting both predevelopment and post development flows. Drainage Study Existing Conditions The site is approximately 21 acres of undeveloped land with small amounts of grass. It appears that the site used to contain an orchard, but it has since been removed. The site is barren and uncultivated. The site was previously part of Phase II of the existing subdivisions, and as such there are water, sewer and storm drainage facilities stubbed to this phase. According to the Thermolito Drainage Master Plan the site lies within the Middlehoff Basin (A-10). This drainage area is in the southeast corner of Thermolito, north of Oro Dam Boulevard, and bounded by Middlehoff Lane to the east. This basin straddles the southern portion of Middlehoff Lane north of Oro Dam Boulevard. Runoff from this 97-acre area collects to a creek at the bottom of a weedy ravine, then enters a gravel tailings area south of Oro Dam Boulevard. The existing ground has a hydrologic soil group C with slopes ranging from 0 to 2 percent and has a very high runoff class. Most of the site currently drains to an existing culvert just North of the project and lies within a subbasin according to the Master Plan. A small portion of the site drains to the previously developed Orchardcrest Drive and Middlehoff Lane, the street directly to the East. Proposed Conditions The post development conditions will consist of 30% impervious pavement, 67% residential area, and about 3% of open space. These conditions will increase the peak flow and the total volume runoff while reducing the time of concentration for peak flow. According to the Thermolito Drainage Master Plan, detention basins are emphasized and are more feasible than channel improvements considering regulatory constraints. Since both sub-basins drain to a common area within the Middlehoff Basin, we are recommending to route stormwater through an onsite detention ORCHARDCREST ESTATES DRAINAGE REPORT Project No.: 20-207 Page 2 of 3 basin and then meter flows via a smaller pipeline to the existing 33” pipe stub previously installed with Phase I. All storm water will be collected using drop inlets and directed to a proposed detention basin located strategically at the northwest corner of the site. We chose this location because it’s slightly lower than other land on the project site, and because of the proximity to a potential secondary outlet should the outlet pipe from the basin become inadvertently plugged allowing the basin to overtop. Should this happen the overtopping storm water will flow north into an existing drainage, without threat to flooding any homes. Drainage Calculation Methods The Rational Method was used to determine the peak flow rate for the 100 yr, condition using the 24-hour 2-year storm. The 100 yr storm will be used in sizing of the detention basin for purposes of this tentative map, while later during the civil design process the 10 yr flows will be used in the hydrologic modeling of the Hydraulic Grade Line to ensure that the 10 yr storm flows do not exit any drainage inlets on the project site. The peak flow for the pre-development and post- development conditions are calculated as follows: Q100 Pre = 7.77 CFS Q100 Post = 23.5 CFS Using the City of Oroville Rain data, coupled with a tabular hydrograph that models inflow and outflow to the detention basin, we estimate that a basin will need to hold at least 46,000 cu-ft of storm water. In addition, we suggest at least 1.5 feet of freeboard be designed into the basin to allow for anomalies and waves. This results in an estimated detention basin as shown on the tentative map which is 4.5 feet deep which has an overall capacity of 54,000 cu-ft of storage. Recommendations Detention Basin The introduction of a detention basin will be needed for this project to store the excess runoff volume as well as manage the peak flow rate during a storm. It is recommended that the detention basin be sized as 435 feet in length, 70 feet in width, and 4.5 feet deep with a side slope of 3:1. This detention basin will hold approximately 54,000 CF. The piping leaving the detention basin should be limited to 15 inches in diameter, so the runoff is restricted to approximately 7 CFS, which will be less than the pre-development conditions. Onsite Piping and Inlets Onsite inlets and piping will be needed to collect all stormwater and direct it to the detention basin. We recommend using drop inlets connected with 15-24” HDPE piping as shown in the Tentative Parcel Map. ORCHARDCREST ESTATES DRAINAGE REPORT Project No.: 20-207 Page 3 of 3 APPENDIX SUPPORTING DOCUMENTATION C.E.C.CALIFORNIA ENGINEERING COMPANY, Inc.ENGINEERING~PLANNING~SURVEYING~COMMUNITY DEVELOPMENTProject: Orchardcrest Tentative MapClient: Bill JaegerCalc. By: DLSDate: 01/06/23Analysis uses Rational Method, Q=CiACity of Chico Intensity Duration Frequency Curves UsedPre-Development FlowPost DevelopmentLocation C Tc, min Area, acres I 100 in/hr Q 100, cfs Location C Tc, min Area, acres I 100 in/hr Q 100, cfsAPN 030-170-080 0.25 47.9 21 1.487.77South hwy 162APN 030-170-080 0.65 36.1211.7223.5APN 030-170-081 0.00 0.0 0 0.000.00North7.77Proposed Pipe from Detention Basin to 33" Pipe Stub In Unit ICulvertPipe Diameter, in Area, ft2Hydraulic RadiusManning's "n"Upstream Invert Elevation, ftDownstream Invert Elevation, ft Length, ft Slope (ft/ft)Coefficient of Discharge, CdUpstream Water Elevation, ftDownstream Water Elevation, ftQ (ft3/sec) - CapacityVelocity, ft/sHDPE151.2 0.310.013 180.00 172.00 11750.00680.51 184 173.55.74.67Proposed Detention Basin Sizing (CHECK ONLY)V= K(CA)1.74QP0.74K C A, acresQP, cfsV, acre-ft Volume, ft3Volume, cyTime to empty, hours0.036 0.6521 5.700.9440848 15131.991.67 72592 2689 2' freeboard1.9215%Detention Basin Sizing, 100-Year Return Period 1110 CIVIC CENTER BOULEVARD, SUITE 404YUBA CITY, CALIFORNIA 95993Page 1 of 8TEL: (530) 751-0952 FAX: (530) 751-0953 y = 8.7036x-0.55R² = 0.9866y = 12.234x-0.549R² = 0.98730.001.002.003.004.0010 25 40 55Intensity, in/hrTime, minOroville Rainfall IntensityIntensity(10-Year), in/hrIntensity(100-Year), in/hrPower (Intensity(10-Year), in/hr)Power (Intensity(100-Year), in/hr) City of Oroville Rainfall Intensity Data Time of Concentration, min.Intensity(10-Year), in/hr Intensity(100-Year), in/hr 10 2.22 3.12 11 2.16 3.04 12 2.10 2.96 13 2.04 2.88 14 1.98 2.80 15 1.92 2.72 16 1.88 2.66 17 1.84 2.61 18 1.80 2.55 19 1.77 2.50 20 1.73 2.44 21 1.69 2.38 22 1.65 2.33 23 1.61 2.27 24 1.57 2.22 25 1.53 2.16 26 1.49 2.10 27 1.46 2.05 28 1.42 1.99 29 1.38 1.94 30 1.34 1.88 31 1.32 1.86 32 1.31 1.84 33 1.29 1.81 34 1.28 1.79 35 1.26 1.77 36 1.24 1.75 37 1.23 1.73 38 1.21 1.70 39 1.20 1.68 40 1.18 1.66 41 1.16 1.64 42 1.15 1.62 43 1.13 1.59 44 1.12 1.57 45 1.10 1.55 46 1.08 1.53 47 1.07 1.51 48 1.05 1.48 49 1.04 1.46 50 1.02 1.44 51 1.00 1.42 52 0.99 1.40 53 0.97 1.37 54 0.96 1.35 55 0.94 1.33 56 0.92 1.31 57 0.91 1.29 58 0.88 1.26 59 0.86 1.24 60 0.84 1.22 120 0.59 0.83 180 0.47 0.67 720 0.22 0.31 1440 0.17 0.24 01234560 12 24 36 48flow, cfs; volume, ac-fttime, hours100-Year Inflow, Outflow, and StoragePeak Inflow (post-development), cfsPeak Outflow (pre-development), cfsDetention Capacity Required, acre-ft C.E.C. CALIFORNIA ENGINEERING COMPANY, Inc. ENGINEERING~PLANNING~SURVEYING~COMMUNITY DEVELOPMENT Duration, hr Duration, min Intensity (100 yr), in/hr Peak Inflow (post- development), cfs Peak Outflow (pre- development), cfs Rate of Flow Detained, cfs Detention Capacity Required, cubic feet Detention Capacity Required, acre-ft 0.08 5 5.06 69.0 5.70 63.3 19,002 0.44 0.17 10 3.46 47.2 5.70 41.5 24,897 0.57 0.25 15 2.77 37.8 5.70 32.1 28,872 0.66 0.33 20 2.36 32.3 5.70 26.6 31,875 0.73 0.42 25 2.09 28.5 5.70 22.8 34,266 0.79 0.50 30 1.89 25.8 5.70 20.1 36,227 0.83 0.58 35 1.74 23.7 5.70 18.0 37,865 0.87 0.67 40 1.62 22.1 5.70 16.4 39,250 0.90 0.75 45 1.51 20.7 5.70 15.0 40,429 0.93 0.83 50 1.43 19.5 5.70 13.8 41,437 0.95 0.92 55 1.36 18.5 5.70 12.8 42,299 0.97 1.00 60 1.29 17.7 5.70 12.0 43,036 0.99 1.08 65 1.24 16.9 5.70 11.2 43,663 1.00 1.17 70 1.19 16.2 5.70 10.5 44,193 1.01 1.25 75 1.14 15.6 5.70 9.9 44,638 1.02 1.33 80 1.10 15.1 5.70 9.4 45,005 1.03 1.42 85 1.07 14.6 5.70 8.9 45,301 1.04 1.50 90 1.04 14.1 5.70 8.4 45,534 1.05 1.58 95 1.01 13.7 5.70 8.0 45,709 1.05 1.67 100 0.98 13.3 5.70 7.6 45,830 1.05 1.75 105 0.95 13.0 5.70 7.3 45,901 1.05 1.83 110 0.93 12.7 5.70 7.0 45,927 1.05 1.92 115 0.91 12.4 5.70 6.7 45,909 1.05 2.00 120 0.88 12.1 5.70 6.4 45,852 1.05 2.08 125 0.86 11.8 5.70 6.1 45,757 1.05 2.17 130 0.85 11.5 5.70 5.8 45,627 1.05 2.25 135 0.83 11.3 5.70 5.6 45,464 1.04 2.33 140 0.81 11.1 5.70 5.4 45,271 1.04 2.42 145 0.80 10.9 5.70 5.2 45,047 1.03 2.50 150 0.78 10.7 5.70 5.0 44,796 1.03 2.58 155 0.77 10.5 5.70 4.8 44,518 1.02 2.67 160 0.76 10.3 5.70 4.6 44,215 1.02 2.75 165 0.74 10.1 5.70 4.4 43,889 1.01 2.83 170 0.73 10.0 5.70 4.3 43,539 1.00 2.92 175 0.72 9.8 5.70 4.1 43,168 0.99 3.00 180 0.71 9.7 5.70 4.0 42,775 0.98 3.08 185 0.70 9.5 5.70 3.8 42,363 0.97 3.17 190 0.69 9.4 5.70 3.7 41,932 0.96 3.25 195 0.68 9.2 5.70 3.5 41,482 0.95 3.33 200 0.67 9.1 5.70 3.4 41,015 0.94 3.42 205 0.66 9.0 5.70 3.3 40,531 0.93 3.50 210 0.65 8.9 5.70 3.2 40,030 0.92 3.58 215 0.64 8.8 5.70 3.1 39,514 0.91 3.67 220 0.63 8.7 5.70 3.0 38,983 0.89 3.75 225 0.63 8.5 5.70 2.8 38,437 0.88 3.83 230 0.62 8.4 5.70 2.7 37,877 0.87 3.92 235 0.61 8.3 5.70 2.6 37,303 0.86 4.00 240 0.60 8.2 5.70 2.5 36,717 0.84 4.08 245 0.60 8.2 5.70 2.5 36,117 0.83 4.17 250 0.59 8.1 5.70 2.4 35,505 0.82 4.25 255 0.58 8.0 5.70 2.3 34,881 0.80 4.33 260 0.58 7.9 5.70 2.2 34,245 0.79 4.42 265 0.57 7.8 5.70 2.1 33,598 0.77 4.50 270 0.57 7.7 5.70 2.0 32,941 0.76 4.58 275 0.56 7.7 5.70 2.0 32,272 0.74 4.67 280 0.56 7.6 5.70 1.9 31,593 0.73 4.75 285 0.55 7.5 5.70 1.8 30,904 0.71 4.83 290 0.54 7.4 5.70 1.7 30,206 0.69 4.92 295 0.54 7.4 5.70 1.7 29,498 0.68 5.00 300 0.53 7.3 5.70 1.6 28,780 0.66 5.08 305 0.53 7.2 5.70 1.5 28,054 0.64 5.17 310 0.53 7.2 5.70 1.5 27,318 0.63 5.25 315 0.52 7.1 5.70 1.4 26,574 0.61 5.33 320 0.52 7.0 5.70 1.3 25,822 0.59 5.42 325 0.51 7.0 5.70 1.3 25,062 0.58 5.50 330 0.51 6.9 5.70 1.2 24,293 0.56 5.58 335 0.50 6.9 5.70 1.2 23,517 0.54 5.67 340 0.50 6.8 5.70 1.1 22,733 0.52 5.75 345 0.50 6.8 5.70 1.1 21,942 0.50 5.83 350 0.49 6.7 5.70 1.0 21,143 0.49 5.92 355 0.49 6.7 5.70 1.0 20,338 0.47 6.00 360 0.48 6.6 5.70 0.9 19,525 0.45 6.08 365 0.48 6.6 5.70 0.9 18,705 0.43 6.17 370 0.48 6.5 5.70 0.8 17,879 0.41 6.25 375 0.47 6.5 5.70 0.8 17,047 0.39 6.33 380 0.47 6.4 5.70 0.7 16,207 0.37 6.42 385 0.47 6.4 5.70 0.7 15,362 0.35 6.50 390 0.46 6.3 5.70 0.6 14,511 0.33 6.58 395 0.46 6.3 5.70 0.6 13,653 0.31 6.67 400 0.46 6.2 5.70 0.5 12,790 0.29 6.75 405 0.45 6.2 5.70 0.5 11,921 0.27 6.83 410 0.45 6.1 5.70 0.4 11,046 0.25 6.92 415 0.45 6.1 5.70 0.4 10,165 0.23 7.00 420 0.44 6.1 5.70 0.4 9,279 0.21 7.08 425 0.44 6.0 5.70 0.3 8,388 0.19 7.17 430 0.44 6.0 5.70 0.3 7,492 0.17 7.25 435 0.44 6.0 5.70 0.3 6,590 0.15 7.33 440 0.43 5.9 5.70 0.2 5,683 0.13 7.42 445 0.43 5.9 5.70 0.2 4,771 0.11 7.50 450 0.43 5.8 5.70 0.1 3,855 0.09 7.58 455 0.43 5.8 5.70 0.1 2,933 0.07 7.67 460 0.42 5.8 5.70 0.1 2,007 0.05 7.75 465 0.42 5.7 5.70 0.0 1,076 0.02 7.83 470 0.42 5.7 5.70 0.0 140 0.00 7.92 475 0.42 5.7 5.70 0.0 -800 -0.02 8.00 480 0.41 5.6 5.70 -0.1 -1,744 -0.04 Detention Basin Calculations per Gupta, Hydrology & Hydraulic Systems, 1995, Page 638-639 1110 CIVIC CENTER BOULEVARD, SUITE 404 YUBA CITY, CALIFORNIA 95993 Page 5 of 8 TEL: (530) 751-0952 FAX: (530) 751-0953 C.E.C. CALIFORNIA ENGINEERING COMPANY, Inc. ENGINEERING~PLANNING~SURVEYING~COMMUNITY DEVELOPMENT Duration, hr Duration, min Intensity (100 yr), in/hr Peak Inflow (post- development), cfs Peak Outflow (pre- development), cfs Rate of Flow Detained, cfs Detention Capacity Required, cubic feet Detention Capacity Required, acre-ft 8.17 490 0.41 5.6 5.70 -0.1 -3,646 -0.08 8.33 500 0.40 5.5 5.70 -0.2 -5,565 -0.13 8.50 510 0.40 5.5 5.70 -0.2 -7,500 -0.17 8.67 520 0.40 5.4 5.70 -0.3 -9,451 -0.22 8.83 530 0.39 5.3 5.70 -0.4 -11,418 -0.26 9.00 540 0.39 5.3 5.70 -0.4 -13,399 -0.31 9.17 550 0.38 5.2 5.70 -0.5 -15,395 -0.35 9.33 560 0.38 5.2 5.70 -0.5 -17,406 -0.40 9.50 570 0.38 5.1 5.70 -0.6 -19,429 -0.45 9.67 580 0.37 5.1 5.70 -0.6 -21,467 -0.49 9.83 590 0.37 5.0 5.70 -0.7 -23,517 -0.54 10.00 600 0.37 5.0 5.70 -0.7 -25,580 -0.59 10.17 610 0.36 4.9 5.70 -0.8 -27,656 -0.63 10.33 620 0.36 4.9 5.70 -0.8 -29,743 -0.68 10.50 630 0.36 4.9 5.70 -0.8 -31,842 -0.73 10.67 640 0.35 4.8 5.70 -0.9 -33,953 -0.78 10.83 650 0.35 4.8 5.70 -0.9 -36,075 -0.83 11.00 660 0.35 4.7 5.70 -1.0 -38,207 -0.88 11.17 670 0.34 4.7 5.70 -1.0 -40,351 -0.93 11.33 680 0.34 4.7 5.70 -1.0 -42,505 -0.98 11.50 690 0.34 4.6 5.70 -1.1 -44,668 -1.03 11.67 700 0.34 4.6 5.70 -1.1 -46,842 -1.08 11.83 710 0.33 4.5 5.70 -1.2 -49,026 -1.13 12.00 720 0.33 4.5 5.70 -1.2 -51,219 -1.18 12.17 730 0.33 4.5 5.70 -1.2 -53,422 -1.23 12.33 740 0.33 4.4 5.70 -1.3 -55,633 -1.28 12.50 750 0.32 4.4 5.70 -1.3 -57,854 -1.33 12.67 760 0.32 4.4 5.70 -1.3 -60,083 -1.38 12.83 770 0.32 4.4 5.70 -1.3 -62,321 -1.43 13.00 780 0.32 4.3 5.70 -1.4 -64,567 -1.48 13.17 790 0.31 4.3 5.70 -1.4 -66,822 -1.53 13.33 800 0.31 4.3 5.70 -1.4 -69,084 -1.59 13.50 810 0.31 4.2 5.70 -1.5 -71,355 -1.64 13.67 820 0.31 4.2 5.70 -1.5 -73,633 -1.69 13.83 830 0.31 4.2 5.70 -1.5 -75,919 -1.74 14.00 840 0.30 4.1 5.70 -1.6 -78,212 -1.80 14.17 850 0.30 4.1 5.70 -1.6 -80,513 -1.85 14.33 860 0.30 4.1 5.70 -1.6 -82,821 -1.90 14.50 870 0.30 4.1 5.70 -1.6 -85,136 -1.95 14.67 880 0.30 4.0 5.70 -1.7 -87,458 -2.01 14.83 890 0.29 4.0 5.70 -1.7 -89,786 -2.06 15.00 900 0.29 4.0 5.70 -1.7 -92,122 -2.11 15.17 910 0.29 4.0 5.70 -1.7 -94,464 -2.17 15.33 920 0.29 3.9 5.70 -1.8 -96,812 -2.22 15.50 930 0.29 3.9 5.70 -1.8 -99,167 -2.28 15.67 940 0.29 3.9 5.70 -1.8 -101,528 -2.33 15.83 950 0.28 3.9 5.70 -1.8 -103,895 -2.39 16.00 960 0.28 3.9 5.70 -1.8 -106,269 -2.44 16.33 980 0.28 3.8 5.70 -1.9 -111,033 -2.55 16.67 1000 0.28 3.8 5.70 -1.9 -115,821 -2.66 17.00 1020 0.27 3.7 5.70 -2.0 -120,631 -2.77 17.33 1040 0.27 3.7 5.70 -2.0 -125,463 -2.88 17.67 1060 0.27 3.7 5.70 -2.0 -130,316 -2.99 18.00 1080 0.26 3.6 5.70 -2.1 -135,189 -3.10 18.33 1100 0.26 3.6 5.70 -2.1 -140,082 -3.22 18.67 1120 0.26 3.5 5.70 -2.2 -144,995 -3.33 19.00 1140 0.26 3.5 5.70 -2.2 -149,926 -3.44 19.33 1160 0.25 3.5 5.70 -2.2 -154,876 -3.56 19.67 1180 0.25 3.4 5.70 -2.3 -159,843 -3.67 20.00 1200 0.25 3.4 5.70 -2.3 -164,828 -3.78 20.33 1220 0.25 3.4 5.70 -2.3 -169,830 -3.90 20.67 1240 0.25 3.3 5.70 -2.4 -174,848 -4.01 21.00 1260 0.24 3.3 5.70 -2.4 -179,882 -4.13 21.33 1280 0.24 3.3 5.70 -2.4 -184,932 -4.25 21.67 1300 0.24 3.3 5.70 -2.4 -189,997 -4.36 22.00 1320 0.24 3.2 5.70 -2.5 -195,077 -4.48 22.33 1340 0.24 3.2 5.70 -2.5 -200,172 -4.60 22.67 1360 0.23 3.2 5.70 -2.5 -205,281 -4.71 23.00 1380 0.23 3.2 5.70 -2.5 -210,403 -4.83 23.33 1400 0.23 3.1 5.70 -2.6 -215,540 -4.95 23.67 1420 0.23 3.1 5.70 -2.6 -220,689 -5.07 24.00 1440 0.23 3.1 5.70 -2.6 -225,852 -5.18 25.00 1500 0.22 3.0 5.70 -2.7 -241,416 -5.54 26.00 1560 0.22 3.0 5.70 -2.7 -257,087 -5.90 27.00 1620 0.21 2.9 5.70 -2.8 -272,859 -6.26 28.00 1680 0.21 2.8 5.70 -2.9 -288,727 -6.63 29.00 1740 0.20 2.8 5.70 -2.9 -304,686 -6.99 30.00 1800 0.20 2.7 5.70 -3.0 -320,729 -7.36 31.00 1860 0.20 2.7 5.70 -3.0 -336,855 -7.73 32.00 1920 0.19 2.6 5.70 -3.1 -353,057 -8.11 33.00 1980 0.19 2.6 5.70 -3.1 -369,332 -8.48 34.00 2040 0.19 2.5 5.70 -3.2 -385,678 -8.85 35.00 2100 0.18 2.5 5.70 -3.2 -402,090 -9.23 36.00 2160 0.18 2.5 5.70 -3.2 -418,567 -9.61 37.00 2220 0.18 2.4 5.70 -3.3 -435,104 -9.99 38.00 2280 0.18 2.4 5.70 -3.3 -451,701 -10.37 39.00 2340 0.17 2.4 5.70 -3.3 -468,353 -10.75 40.00 2400 0.17 2.3 5.70 -3.4 -485,060 -11.14 41.00 2460 0.17 2.3 5.70 -3.4 -501,818 -11.52 42.00 2520 0.17 2.3 5.70 -3.4 -518,627 -11.91 43.00 2580 0.16 2.2 5.70 -3.5 -535,483 -12.29 44.00 2640 0.16 2.2 5.70 -3.5 -552,386 -12.68 45.00 2700 0.16 2.2 5.70 -3.5 -569,334 -13.07 46.00 2760 0.16 2.2 5.70 -3.5 -586,326 -13.46 47.00 2820 0.16 2.1 5.70 -3.6 -603,359 -13.85 48.00 2880 0.15 2.1 5.70 -3.6 -620,433 -14.24 1110 CIVIC CENTER BOULEVARD, SUITE 404 YUBA CITY, CALIFORNIA 95993 Page 6 of 8 TEL: (530) 751-0952 FAX: (530) 751-0953 C.E.C. CALIFORNIA ENGINEERING COMPANY, Inc. ENGINEERING~PLANNING~SURVEYING~COMMUNITY DEVELOPMENT Duration, hr Duration, min Intensity (10 yr), in/hr Peak Inflow (post- development), cfs Peak Outflow (pre- development), cfs Rate of Flow Detained, cfs Detention Capacity Required, cubic feet Detention Capacity Required, acre-ft 0.08 5 3.59 49.0 5.70 43.3 12,997 0.30 0.17 10 2.45 33.5 5.70 27.8 16,670 0.38 0.25 15 1.96 26.8 5.70 21.1 18,981 0.44 0.33 20 1.68 22.9 5.70 17.2 20,604 0.47 0.42 25 1.48 20.2 5.70 14.5 21,793 0.50 0.50 30 1.34 18.3 5.70 12.6 22,677 0.52 0.58 35 1.23 16.8 5.70 11.1 23,333 0.54 0.67 40 1.14 15.6 5.70 9.9 23,810 0.55 0.75 45 1.07 14.6 5.70 8.9 24,140 0.55 0.83 50 1.01 13.8 5.70 8.1 24,350 0.56 0.92 55 0.96 13.1 5.70 7.4 24,456 0.56 1.00 60 0.92 12.5 5.70 6.8 24,474 0.56 1.08 65 0.88 12.0 5.70 6.3 24,414 0.56 1.17 70 0.84 11.5 5.70 5.8 24,286 0.56 1.25 75 0.81 11.1 5.70 5.4 24,096 0.55 1.33 80 0.78 10.7 5.70 5.0 23,852 0.55 1.42 85 0.76 10.3 5.70 4.6 23,559 0.54 1.50 90 0.73 10.0 5.70 4.3 23,220 0.53 1.58 95 0.71 9.7 5.70 4.0 22,840 0.52 1.67 100 0.69 9.4 5.70 3.7 22,422 0.51 1.75 105 0.67 9.2 5.70 3.5 21,969 0.50 1.83 110 0.66 9.0 5.70 3.3 21,483 0.49 1.92 115 0.64 8.7 5.70 3.0 20,967 0.48 2.00 120 0.63 8.5 5.70 2.8 20,423 0.47 2.08 125 0.61 8.3 5.70 2.6 19,853 0.46 2.17 130 0.60 8.2 5.70 2.5 19,257 0.44 2.25 135 0.59 8.0 5.70 2.3 18,639 0.43 2.33 140 0.57 7.8 5.70 2.1 17,998 0.41 2.42 145 0.56 7.7 5.70 2.0 17,337 0.40 2.50 150 0.55 7.6 5.70 1.9 16,655 0.38 2.58 155 0.54 7.4 5.70 1.7 15,956 0.37 2.67 160 0.53 7.3 5.70 1.6 15,238 0.35 2.75 165 0.52 7.2 5.70 1.5 14,503 0.33 2.83 170 0.52 7.0 5.70 1.3 13,753 0.32 2.92 175 0.51 6.9 5.70 1.2 12,987 0.30 3.00 180 0.50 6.8 5.70 1.1 12,206 0.28 3.08 185 0.49 6.7 5.70 1.0 11,411 0.26 3.17 190 0.49 6.6 5.70 0.9 10,603 0.24 3.25 195 0.48 6.5 5.70 0.8 9,781 0.22 3.33 200 0.47 6.4 5.70 0.7 8,948 0.21 3.42 205 0.47 6.4 5.70 0.7 8,102 0.19 3.50 210 0.46 6.3 5.70 0.6 7,244 0.17 3.58 215 0.45 6.2 5.70 0.5 6,376 0.15 3.67 220 0.45 6.1 5.70 0.4 5,497 0.13 3.75 225 0.44 6.0 5.70 0.3 4,608 0.11 3.83 230 0.44 6.0 5.70 0.3 3,708 0.09 3.92 235 0.43 5.9 5.70 0.2 2,799 0.06 4.00 240 0.43 5.8 5.70 0.1 1,881 0.04 4.08 245 0.42 5.8 5.70 0.1 954 0.02 4.17 250 0.42 5.7 5.70 0.0 18 0.00 4.25 255 0.41 5.6 5.70 -0.1 -927 -0.02 4.33 260 0.41 5.6 5.70 -0.1 -1,880 -0.04 4.42 265 0.40 5.5 5.70 -0.2 -2,840 -0.07 4.50 270 0.40 5.5 5.70 -0.2 -3,809 -0.09 4.58 275 0.40 5.4 5.70 -0.3 -4,785 -0.11 4.67 280 0.39 5.4 5.70 -0.3 -5,768 -0.13 4.75 285 0.39 5.3 5.70 -0.4 -6,758 -0.16 4.83 290 0.38 5.3 5.70 -0.4 -7,756 -0.18 4.92 295 0.38 5.2 5.70 -0.5 -8,760 -0.20 5.00 300 0.38 5.2 5.70 -0.5 -9,770 -0.22 5.08 305 0.37 5.1 5.70 -0.6 -10,787 -0.25 5.17 310 0.37 5.1 5.70 -0.6 -11,810 -0.27 5.25 315 0.37 5.0 5.70 -0.7 -12,840 -0.29 5.33 320 0.36 5.0 5.70 -0.7 -13,875 -0.32 5.42 325 0.36 4.9 5.70 -0.8 -14,916 -0.34 5.50 330 0.36 4.9 5.70 -0.8 -15,962 -0.37 5.58 335 0.36 4.9 5.70 -0.8 -17,014 -0.39 5.67 340 0.35 4.8 5.70 -0.9 -18,072 -0.41 5.75 345 0.35 4.8 5.70 -0.9 -19,134 -0.44 5.83 350 0.35 4.7 5.70 -1.0 -20,202 -0.46 5.92 355 0.34 4.7 5.70 -1.0 -21,275 -0.49 6.00 360 0.34 4.7 5.70 -1.0 -22,353 -0.51 6.08 365 0.34 4.6 5.70 -1.1 -23,435 -0.54 6.17 370 0.34 4.6 5.70 -1.1 -24,523 -0.56 6.25 375 0.33 4.6 5.70 -1.1 -25,615 -0.59 6.33 380 0.33 4.5 5.70 -1.2 -26,711 -0.61 6.42 385 0.33 4.5 5.70 -1.2 -27,812 -0.64 6.50 390 0.33 4.5 5.70 -1.2 -28,917 -0.66 6.58 395 0.32 4.4 5.70 -1.3 -30,027 -0.69 6.67 400 0.32 4.4 5.70 -1.3 -31,140 -0.71 6.75 405 0.32 4.4 5.70 -1.3 -32,258 -0.74 6.83 410 0.32 4.3 5.70 -1.4 -33,380 -0.77 6.92 415 0.32 4.3 5.70 -1.4 -34,505 -0.79 7.00 420 0.31 4.3 5.70 -1.4 -35,635 -0.82 7.08 425 0.31 4.3 5.70 -1.4 -36,768 -0.84 Detention Basin Calculations per Gupta, Hydrology & Hydraulic Systems, 1995, Page 638-639 1110 CIVIC CENTER BOULEVARD, SUITE 404 YUBA CITY, CALIFORNIA 95993 Page 7 of 8 TEL: (530) 751-0952 FAX: (530) 751-0953 C.E.C. CALIFORNIA ENGINEERING COMPANY, Inc. ENGINEERING~PLANNING~SURVEYING~COMMUNITY DEVELOPMENT Duration, hr Duration, min Intensity (10 yr), in/hr Peak Inflow (post- development), cfs Peak Outflow (pre- development), cfs Rate of Flow Detained, cfs Detention Capacity Required, cubic feet Detention Capacity Required, acre-ft 7.17 430 0.31 4.2 5.70 -1.5 -37,905 -0.87 7.25 435 0.31 4.2 5.70 -1.5 -39,046 -0.90 7.33 440 0.31 4.2 5.70 -1.5 -40,190 -0.92 7.42 445 0.30 4.2 5.70 -1.5 -41,338 -0.95 7.50 450 0.30 4.1 5.70 -1.6 -42,489 -0.98 7.58 455 0.30 4.1 5.70 -1.6 -43,644 -1.00 7.67 460 0.30 4.1 5.70 -1.6 -44,802 -1.03 7.75 465 0.30 4.1 5.70 -1.6 -45,963 -1.06 7.83 470 0.30 4.0 5.70 -1.7 -47,127 -1.08 7.92 475 0.29 4.0 5.70 -1.7 -48,295 -1.11 8.00 480 0.29 4.0 5.70 -1.7 -49,466 -1.14 8.17 490 0.29 3.9 5.70 -1.8 -51,817 -1.19 8.33 500 0.29 3.9 5.70 -1.8 -54,179 -1.24 8.50 510 0.28 3.9 5.70 -1.8 -56,554 -1.30 8.67 520 0.28 3.8 5.70 -1.9 -58,939 -1.35 8.83 530 0.28 3.8 5.70 -1.9 -61,336 -1.41 9.00 540 0.27 3.7 5.70 -2.0 -63,743 -1.46 9.17 550 0.27 3.7 5.70 -2.0 -66,160 -1.52 9.33 560 0.27 3.7 5.70 -2.0 -68,587 -1.57 9.50 570 0.27 3.6 5.70 -2.1 -71,024 -1.63 9.67 580 0.26 3.6 5.70 -2.1 -73,471 -1.69 9.83 590 0.26 3.6 5.70 -2.1 -75,926 -1.74 10.00 600 0.26 3.5 5.70 -2.2 -78,391 -1.80 10.17 610 0.26 3.5 5.70 -2.2 -80,864 -1.86 10.33 620 0.25 3.5 5.70 -2.2 -83,346 -1.91 10.50 630 0.25 3.4 5.70 -2.3 -85,836 -1.97 10.67 640 0.25 3.4 5.70 -2.3 -88,334 -2.03 10.83 650 0.25 3.4 5.70 -2.3 -90,840 -2.09 11.00 660 0.24 3.3 5.70 -2.4 -93,354 -2.14 11.17 670 0.24 3.3 5.70 -2.4 -95,875 -2.20 11.33 680 0.24 3.3 5.70 -2.4 -98,403 -2.26 11.50 690 0.24 3.3 5.70 -2.4 -100,939 -2.32 11.67 700 0.24 3.2 5.70 -2.5 -103,482 -2.38 11.83 710 0.24 3.2 5.70 -2.5 -106,032 -2.43 12.00 720 0.23 3.2 5.70 -2.5 -108,588 -2.49 12.17 730 0.23 3.2 5.70 -2.5 -111,151 -2.55 12.33 740 0.23 3.1 5.70 -2.6 -113,720 -2.61 12.50 750 0.23 3.1 5.70 -2.6 -116,296 -2.67 12.67 760 0.23 3.1 5.70 -2.6 -118,878 -2.73 12.83 770 0.22 3.1 5.70 -2.6 -121,466 -2.79 13.00 780 0.22 3.0 5.70 -2.7 -124,060 -2.85 13.17 790 0.22 3.0 5.70 -2.7 -126,659 -2.91 13.33 800 0.22 3.0 5.70 -2.7 -129,264 -2.97 13.50 810 0.22 3.0 5.70 -2.7 -131,875 -3.03 13.67 820 0.22 3.0 5.70 -2.7 -134,492 -3.09 13.83 830 0.22 2.9 5.70 -2.8 -137,113 -3.15 14.00 840 0.21 2.9 5.70 -2.8 -139,740 -3.21 14.17 850 0.21 2.9 5.70 -2.8 -142,373 -3.27 14.33 860 0.21 2.9 5.70 -2.8 -145,010 -3.33 14.50 870 0.21 2.9 5.70 -2.8 -147,652 -3.39 14.67 880 0.21 2.9 5.70 -2.8 -150,299 -3.45 14.83 890 0.21 2.8 5.70 -2.9 -152,951 -3.51 15.00 900 0.21 2.8 5.70 -2.9 -155,608 -3.57 15.17 910 0.21 2.8 5.70 -2.9 -158,269 -3.63 15.33 920 0.20 2.8 5.70 -2.9 -160,935 -3.69 15.50 930 0.20 2.8 5.70 -2.9 -163,606 -3.76 15.67 940 0.20 2.8 5.70 -2.9 -166,280 -3.82 15.83 950 0.20 2.7 5.70 -3.0 -168,960 -3.88 16.00 960 0.20 2.7 5.70 -3.0 -171,643 -3.94 16.33 980 0.20 2.7 5.70 -3.0 -177,023 -4.06 16.67 1000 0.19 2.7 5.70 -3.0 -182,418 -4.19 17.00 1020 0.19 2.6 5.70 -3.1 -187,830 -4.31 17.33 1040 0.19 2.6 5.70 -3.1 -193,257 -4.44 17.67 1060 0.19 2.6 5.70 -3.1 -198,699 -4.56 18.00 1080 0.19 2.5 5.70 -3.2 -204,155 -4.69 18.33 1100 0.18 2.5 5.70 -3.2 -209,625 -4.81 18.67 1120 0.18 2.5 5.70 -3.2 -215,109 -4.94 19.00 1140 0.18 2.5 5.70 -3.2 -220,606 -5.06 19.33 1160 0.18 2.5 5.70 -3.2 -226,116 -5.19 19.67 1180 0.18 2.4 5.70 -3.3 -231,639 -5.32 20.00 1200 0.18 2.4 5.70 -3.3 -237,173 -5.44 20.33 1220 0.17 2.4 5.70 -3.3 -242,720 -5.57 20.67 1240 0.17 2.4 5.70 -3.3 -248,278 -5.70 21.00 1260 0.17 2.3 5.70 -3.4 -253,848 -5.83 21.33 1280 0.17 2.3 5.70 -3.4 -259,429 -5.96 21.67 1300 0.17 2.3 5.70 -3.4 -265,020 -6.08 22.00 1320 0.17 2.3 5.70 -3.4 -270,622 -6.21 22.33 1340 0.17 2.3 5.70 -3.4 -276,234 -6.34 22.67 1360 0.16 2.2 5.70 -3.5 -281,857 -6.47 23.00 1380 0.16 2.2 5.70 -3.5 -287,489 -6.60 23.33 1400 0.16 2.2 5.70 -3.5 -293,131 -6.73 23.67 1420 0.16 2.2 5.70 -3.5 -298,782 -6.86 24.00 1440 0.16 2.2 5.70 -3.5 -304,442 -6.99 25.00 1500 0.16 2.1 5.70 -3.6 -321,476 -7.38 1110 CIVIC CENTER BOULEVARD, SUITE 404 YUBA CITY, CALIFORNIA 95993 Page 8 of 8 TEL: (530) 751-0952 FAX: (530) 751-0953