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Home My WebLink Aboutscan-5TOTAL UNCONTROLLED IMPERVIOUS AREA: 0.266 Acres i TOTAL CONTROLLED IMPERVIOUS AREA: 0.474 Acres y\\yy / 01 25' - 50, 100, SCALE: = 50' CONTROLLED AREA: 2.575 Acres UNCONTROLLED AREA: 0.946 Acres Stormwater Detention Design -Irving Square Addition (Controlled) Site Area length Wide (controlled) Impervious length Wide #16-147 2.58 (Acres) Area 0.47 (Acres) Pervious length Wide Proposed Coef. = 0.4200 Area (Acres) Time of Concentration = 23.70 Highest Lowest length Intensity - 3.54 Slope = 1 875,51 868.81 448 j 1.50% Existing Coef. of Runoff Intensity Area(acres) 0.3 3.54 2.58 = Duration Intensities Proposed Total Area Runoff Runoff Coef. C.F.S. Existing (minutes) 2 yr. C A Q2 C.F.S. 5 5.46 0.4200 2.58 5.90 2.73 10 4.21 0.4200 2.58 4.55 2.73 15 3.54 0.4200 2.58 3.83 2.73 20 3.07 0.4200 2.58 3.32 2.73 30 2.46 0.4200 2.58 2.66 2.73 40 1.97 0.4200 2.58 2.13 2.73 50 1.72 0.4200 2.58 1.86 2.73 60 1.54 0.4200 2.58 1.67 2.73 90 1.23 0.4200 2.58 1.33 2.73 120 0.9 0.4200 2.58 0.97 2.73 Duration Intensities (minutes) 10 yr. 5 7.81 0.4200 2.58 8.45 2.73 10 6.02 0.4200 2.58 6.51 2.73 15 5.07 0.4200 2.58 5.48 2.73 20 4.40 0.4200 2.58 4.76 2.73 30 3.52 0.4200 2.58 3.81 2.73 40 2.82 0.4200 2.58 3.05 2.73 50 2.46 0.4200 2.58 2.66 2.73 60 - 2.22 0.4200 2.58 2.40 2.73 90 1.76 0.4200 2.58 1.90 2.73 120 1.31 0.4200 2.58 1.42 2.73 Duration Intensities (minutes) 100 yr. 5 11.10 0.4200 2.58 12.00 2.73 10 8.55 0.4200 2.58 9.25 2.73 15 7.20 0.4200 2.58 7.79 2.73 20 6.25 0.4200 2.58 6.76 2.73 30 5.00 0.4200 2.58 5.41 2.73 40 4.00 0.4200 2.58 4.33 2.73 50 3.50 0.4200 2.58 3.79 2.73 60 3.15 0.4200 2.58 3.41 2.73 90 2.50 0.4200 2.58 2.70 2.73 120 1.85 0.4200 2.58 2.00 2.73 2.73 Q2 C.F.S. Storage Storage Runoff Volume C.F.S. Feet2 3.17 951.10 1.82 1091.08 1.09 984A7 0.59 702.67 -0.07 -133.49 -0.60 -1449.83 -0.87 -2623.41 -1.07 -3848.90 -1.40 -7583.79 -1.76 -12681.36 5.71 1713.56 3.78 2265.59 2.75 2473.70 2.02 2428.74 1.07 1930.01 0.32 756.43 -0.07 -222A8 -0.33 -1201.39 -0.83 -4488.53 -1.32 -9488.77 9.27 2781.00 6.51 3907.31 5.05 4546,94 4.02 4829.67 2.67 4811.13 1.59 3819.24 1.05 3151.80 0.67 2419.47 -0.03 -166.86 -0.73 -5283.90 (1) OVERLAND CONDITION cone. W AID^". Boo 700 `�x':J RL31p tTiAL soo 600 = -ROCKT 8ARt SOIL _________ X �.:_ ..e__.. Is - - - - Zoo - -- - - TIMBER TM CRASS .,. Zoo 3Y4.;jAS#tlAc- 3 TALL 4 A$.S$ iQ r i5O . Ioo EX_A_rTLE: Bare, Rocky Soil on 1.5% Slope. - Lnd PROCEDURE: Connect Overland Condition (1) Time of Concentration for Overall with Slope (2). Where Line Crosses Length of 1000 feet, the Pivot Line (3), Extend a. Line from the Length (4) through the Pivot Line 3) to the Time of Con. Centration '.5). Stormwater Detention Design -Irving Square Addition (Uncontrolled) Site Area length Wide controlled Impervious (controlled) len 0.95 (Acres) Area th Wide #16-147 0.27 (Acres) Pervious length Wide Proposed Coef. = 0.4800 Pervious 0.68 (Acres) Time of Concentration = 23.70 Highest Lowest length Intensity = 3.54 Slope = 87551 868 8 448 1 50° /o Existing Coef. of Runoff Intensity Area(acres) 0.3 3.54 0.95 = Duration Intensities Proposed Total Area Runoff Runoff Coef. C.F.S. Existing (minutes) 2 yr. C A Q2 C.F.S. 5 5.46 0A800 0.95 2.48 0.00 10 4.21 0.4800 0.95 1.91 0.00 15 3.54 0.4800 0.95 1.61 0.00 20 3.07 0.4800 0.95 1.39 0.00 30 2.46 0.4800 0.95 1.12 0.00 40 1.97 0.4800 0.95 0.89 0.00 50 1.72 0.4800 0.95 0.78 0.00 60 1.54 0.4800 0.95 0.70 0.00 90 1.23 0.4800 0.95 0.56 0.00 120 0.9 0.4800 0.95 0.41 0.00 Duration Intensities minutes) 10 yr. 5 7.81 0.4800 0.95 3.55 0.00 10 6.02 0.4800 0.95 2.73 0.00 15 5.07 0.4800 0.95 2.30 0.00 20 4.40 0.4800 0.95 2.00 0.00 30 3.52 0.4800 0.95 1.60 0.00 40 2.82 0.4800 0.95 1.28 0.00 50 2.46 0.4800 0.95 1.12 0.00 60 2.22 0.4800 0.95 1.01 0.00 90 1.76 0.4800 0.95 0.80 0.00 120 1.31 0.4800 0.95 0.59 0.00 Duration Intensities minutes) 100 yr. 5 11.10 0.4800 0.95 5.04 0.00 10 8.55 0.4800 0.95 3.88 0.00 15 7.20 0.4800 0.95 3.27 0.00 20 6.25 0.4800 0.95 2.84 0.00 30 5.00 0.4800 0.95 2.27 0.00 40 4.00 0.4800 0.95 1.82 0.00 50 3.50 0.4800 0.95 1.59 0.00 60 3.15 0.4800 0.95 1.43 0.00 90 2.50 0.4800 0.95 1.14 0.00 120 1.85 0.4800 0.95 0.84 0.00 1.00 Q2 C.F.S. Storage Storage Runoff Volume C.F.S. Feet2 2.48 743.78 1.91 1147.01 1.61 1446.70 1.39 1672.83 1.12 2010.67 0.89 2146.89 0.78 2343.05 0.70 2517.42 0.56 3016.00 0.41 2942.44 3.55 1063.91 2.73 1640.14 2.30 2071.97 2.00 2397.54 1.60 2877.05 1.28 3073.21 1.12 3351.11 1.01 3629.01 0.80 4315.58 0.59 4282.88 5.04 1512.09 3.88 2329.43 3.27 2942.44 2.84 3405.60 2.27 4086.72 1.82 4359.17 1.59 4767.84 1.43 5149.27 1.14 6130.08 0.84 6048.35 Stormwater Calculations -"Irving Square Addition" PROPOSED COEFFICIENT (CONTROLLED) c = ((0.3)(Pervious Area)+(0.95)(Impervious Area))/(Total Area) c =((0.3)(2.101)+(0.95)(0.474))/(2.575) = 0.42 PROPOSED COEFFICIENT (UNCONTROLLED) c = ((0.3)(Pervious Area)+(0.95)(Im pervious Area))/(Total Area) c =((0.3)(0.68)+(0.95)(0.266))/(0.946) = 0.48 1 00year STORM Controlled + Uncontrolled = 4830 (see spreadsheet) + 6130 (see spreadsheet) = 10960 cu. ft. 1'/a" RAINFALL V = (1.25/12)(2.575)(43560) V = 11684 cu. ft. (greater than 100 year storm) Q = Release rate = up to 1'/4" rainfall released over 24 hours Q = 11684 / ((24)(60)(60)) Q=0.14cfs DETENTION POND VOLUME Area of Contour 871.00 = 10202 ft.2 Area of Contour 870.00 = 07764 ft.2 Volume between Contour 871.00 and 870.00 = (10202 + 7764)/2 = 8983 cu. ft. Volume of pyramid between drain and Contour 870.00 = (870.00 - 868.90)(7764)(1/3) = 2847 cu. ft. Total Volume of Pond = 8983 + 2587 = 11830 cu. ft. PIPE SIZING 100 year STORM Qmax = Q - Q(uncontrolled) = 2.73 - 1.00 = 1.73 Qmax = C x AREA x, (2)(gravity)(depth) AREA= Qmax / (0.6 x (2)(gravity)(depth) ) AREA= 1.73 / (0.6 x (2)(32.2)(871.00-868.90) ) AREA= 0.25 sq. ft. 0.25 = ¶(R)2 R = 0.28'0 = 0.56' PIPE SIZING 1'/4" RAINFALL Qmax = C x AREA x (2)(gravity)(depth) AREA= Qmax / (0.6 x (2)(gravity)(depth) ) AREA= 0.14 / (0.6 x (2)(32.2)(871.00-868.90) ) AREA= 0.020 sq. ft. = 2.88 sq. in. (No need for restrictor plate, 3" O PVC pipe @ 2.10% maximum flow is 0.14 cfs) The Storm Water Detention Pond will overflow at the berms (871.30) between Lots 4 & 5, Lots 5 & 6, Lots 6 & 7 if a storm event exceeds the Detention Pond's capacity HELLAND ENGINEERING & SURVEYING, LTD. STORM WATER CALCULATIONS "IRVING SQUARE ADDITION" SHEET NO. C.2