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HomeMy WebLinkAboutSTORMWATER CALCULATIONS 2 - 12-00155 - 273 S 5th W - Campus Courtyard - Site PlanPROJECT NAME: PROJECT #: CLIENT: DATE: ASPEN ENGINEERING.INC. 10727 N YELLOWSTONE HWY. IDAHO FALLS,IDAHO 83401 208-542-1911 Campus Courtyard -Full Buildout -6 buildings 2012.002 Jared Sommer 4/23/2012 Input Result STORMWATER CALCULATIONS -100 year storm PRE DEVELOP SITE AREA = C VALUE = COMPOSITE C Tc =(minutes) i(10)*= i(100)*= Qp10 =C*i10*A Qp100 =Ci*100*A POST DEVELOP C CHANGES COMPOSITE C 171246 Square Feet 7623 Sq.Ft.-Hard Surface 8486 Building 10920 Landscaping 144217 Unimproved 44.35 tc=c(Lnsl\-.5)1\0.467 2.18 in/hour 3.51 in/hour 2.99 CFS 4.82 CFS 77720 Sq.Ft.Hard Surface 32460 Building 61066 Landscaping 171246 3.93 Acres C VALUE WEIGHTED C 0.90 6860.7 0.95 8061.7 0.15 1638 0.30 43265.1 0.35 L (length)=280 feet S (slope)= c =0.83 feet,1.44 meters n=0.02 smooth pavements 0.30 Poor grass/bare sod 0.40 Average grass 0.80 Dense grass C VALUE WEIGHTED C 0.90 69948 0.95 30837 0.15 9159.9 0.64 o feeUfeet Tc =(minutes) Qp10 =C*i10*A Qp100 =Ci*100*A 3.11 tc=0.0078(L 1\0.77/S0.385)length =120 feet slope = 5.50 CFS 8.86 CFS (EQUALS PEAK RUNOFF =REQUIRED F.D.CAPACITY) 0.02 feeUfeet FRENCH DRAIN City of Rexburg "Standard Infiltrator French Drain" #of drains 4 each ~~~~3 ~ Barrel diam.4 feet Chamber Volume 183.6 Cubic.Feet Gravel Volume 120.35 Cubic.Feet Btm soil perm.0.020 ft/min. FRENCH DRAIN STORAGE CAPACITY -SITE TOTAL Total 1366.60 4/drain Storm Tech 740 Chambers Coarse sand and Gravel+ cf WEIGHTED DEPTH OF PRECIPITATION OVER ENTIRE SITE 0.15 inches (Volume of runoff wlo percolation) In other words,it can rain 0.15 inches and the french drains will hold the entire runoff volume without any percolation DISSIPATION CAPACITY (soil perm.X btm.area) 12.16 cf/min Greater than Required -OK *From IDF Curve generated from NOAA Atlas 2 data and NOAA Spreadsheet +Table 4.1 "Typical Values of Permeability Coefficients"-Braja M.Das, Principles of Geotechnical EnQineerinQ,2nd Ed. UNWEIGHTED DEPTH OF PRECIP OVER ENTIRE SITE 0.10 inches Intensity-Duration-Frequency -Rexburg,Idaho Intensity (inches per hour)Duration 25102550100 '====================================================================5 1.311.842.182.66 3.063.51 10 1.021.431.692.06 2.382.72 15 0.861.211.431.742.01 2.30 30 0.590.840.99 1.211.391.59 1 0.380.530.630.760.88 1.01 2 0.230.310.370.450.520.58 3 0.180.230.280.34 0.390.43 6 0.120.150.180.22 0.250.27 12 0.080.100.110.14 0.160.18 24 0.050.060.070.08 0.100.11 -•...c-III Q).c ()c ~- 'iij c Q)-c 0.50 0.00 5 10 15 30 1 2 3 6 -~- -x- --0-- 12 24 Duration in minutes and hours