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CITY OF EVERETT DRAINAGE CALCULATIONS (less tiian 5 acres) 09-Jan-92 <br /> DICK JOHNSON 19TH AVENUE PROPERTY, LSA No. 2697 02:32 PM <br /> ________________________________________________________�______________ <br /> Total area, acres = 0.980 <br /> Area to remain undeveloped = 0.412 <br /> Net area for detention calculation, acres = 0.568 <br /> Design Storm Criteria, from Evarett Basin Map <br /> ====sa��=��___________�__=___________________ <br /> Basin: SILVER LAKE Pre-3t�alopment = 10 yr <br /> Post-development = 25 yr <br /> Type of cover: ground peak runoff area, total <br /> (exiating) slope: rate, cfs/ac: acres: runoff: <br /> -------------------------------------- -------- ----------------- <br /> woods/forest 4.00� 0.190 x cfs <br /> lawn/landscapinq 3.00� 0.343 x 0.465 0.16 cfs <br /> earth/gravel 4.00� 0.813 x 0.046 0.04 cfs <br /> imperv. roofs, USE: 20.00$ 1.500 x _ 0 057_ _ 0 a9 cfs <br /> Peak rate of runoff = 0.568 0.28 cfs <br /> For flowe less than 0.130 cfs, use 0.130 cfs. The rate used here <br /> is the equivalent of 0.283 cfs / 0.568 acres = 0.498 cfs/acre <br /> PBAK RATB OF RU90FP <br /> ---- z.�-=---------------------•-__-____________�.='__:________ <br /> ----a:�:=:..::...::::..: --------------------- <br /> aound siope <br /> Table 2 Pceq, yr 2.00t 4.001 5.00t HA 10.00t NA 20•OOt <br /> -----------------------�-------......----------------------------------�------ <br /> 2 0.002 0.003 0.003 MA 0.004 NA 0.005 <br /> vo0d6/focest 5 0.070 0.090 0.100 NA 0.125 NA 0.150 <br /> 10 0.150 0.190 0.210 9A 0.265 NA 0.320 <br /> ---.------------------------------------------------------------------------------�---- <br /> Table 3 FYeq, yr 2.002 3.00t 5.00t HA 30.00t Na 20.00t <br /> --------------------------------------------------------------------------------�------ <br /> 2 0.010 0.080 0.100 BA 0.120 Na 0.150 <br /> lavaB/landscape 5 0.210 0.223 0.250 BA 0.310 NA 0.390 <br /> 10 0.310 0.343 0.410 NA 0.510 AA 0.630 <br /> ------------------�------- <br /> ------------------------------------�---�--�----------------- <br /> Table 4 Preq, yr 2.00t 4.00! S.00t lA 10.00t NA 20.00! <br /> ---------------�--------�-------------------------------------------------------------- <br /> 2 O.J40 0.433 0.4b0 NA 0.570 AA 0.650 <br /> earth/gravel 5 0.560 0.653 0.100 NA O.b00 NA O.A70 <br /> 10 0.1Z0 0.813 0.660 AA 0.960 NA 1.040 <br /> -------------------------- <br /> ------=---�------------------------------------------------�- <br /> 2able 5 Freq, yr 2.00t HA S.ODt HA 10.00t HA ZO.00t <br /> ----------------------------�---------�-------...--------------------------�----------� <br /> 2 0.910 NA 0.910 NA 1.010 NA 1.040 <br /> lnperrlous 5 1.140 NA 1,210 NA 1.150 NA 0.150 <br /> 10 1.720 MA 1.900 NA 1•450 1A 1•500 <br /> -:_�:__�____=_::_�________________:__=_____:__:____:___�________:____:_:_--=___-= <br />