Laserfiche WebLink
DRAINAGE CALCULATIONS (City of Everett) :i D <br />14-Mar-89 MAR 1 C 1989 <br />---------------- <br />OF . <br />FOREST PARK SDA SCHOOL LSAN 2019 CITYWW E"VE" ""...•RETT <br />••• <br />Total area, acres = 4.660Uac��e5akS Dept. <br />Area to remain undeveloped = 3.366 acres <br />Net area for detention calculation, acres = 1.294 acres <br />Design Storm Criteria, from Everett Basin Map <br />Pre -development = 10,y,, "- <br />Post -development = 23 yr. <br />Type of cover: ground peak runoff area, total <br />(existing) slope: rate, cfs/ac: acres: runoff: <br />--------------------------------------- -------- ---------------- <br />N oods/forest 12.20% 0.277 x 1.294 0.359 cfs <br />lawn/landscaping 12.20% 0.000 x 0.000 0.000 cis <br />earth/gravel 12.20% 0.000 x 0.000 0.000 cfs <br />impervious 12.20% 0.000 x 0.000 0.000 cfs <br />---------------- <br />Peak rate of runoff = 1.29 0.359 cfs <br />For flows less than 0.130 cfs, use 0.130 cfs. The rate used here is <br />the equivalent of 0.359 cfs / 1.294 acres 0.277 cfs/acre <br />PEAK RATE OF RUNOFF (Table below from City of Everett published tables) <br />-------------------------Ground Slope ----------------- <br />Table 2 Freq, yrs: 2.00% NA 5.00%. NA 10.00% 12.20% 20.002 <br />---------------------------------------------------- <br />2 0.002 NA 0.003 NA 0.004 0.004 0.005 <br />woods/forest 5 0.070 NA 0.100 NA 0.125 0.131 0.150 <br />10 0.150 NA 0.210 NA 0.265 0.277 0.320 <br />---------------------------------------------------------------------------------------- <br />Table 3 Freq, yrs: 2.00X NA 5.00% NA 10.00% 12.20% 20.00% <br />---- ---- -------------------------- <br />2 0.070 NA 0.100 NA 0.120 0.127 0.150 <br />lawns/landscape 5 0.210 NA 0.250 NA 0.310 0.328 0.390 <br />10 0.310 NA 0.410 NA 0.510 0.536 0.630 <br />---- ----------------------------------------------------------- <br />Table 4-------------Freq, yrs: 2.00% NA 5.00% NA 10.00% 12.20% 20.00% <br />------ ------------------------------------------------------------------ <br />2 0.340 NA 0.400 NA 0.570 0.5BB 0.650 <br />earth/gravel 5 0.560 NA 0.700 NA O.B00 0.815 0.870 <br />10 0.720 NA 0.860 NA 0.960 0.978 1.040 <br />---------------------------------------------------------------------------------------- <br />Table 5 Freq, yrs: 2.00% NA 5,00% NA 10.00% 12.20% 20.00% <br />---------------------------------------------------------------------------------------- <br />2 0.910 NA 0.970 NA 1.010 1.017 1.040 <br />imperviLIUs 5 1.140 NA 1.210 NA 1.250 1.000 0.150 <br />10 1.320 NA 1.400 NA 1.450 1.461 1.500 <br />i< 'Clio <br />. r. <br />