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<br /> .-..-.,---.-...-..--..,.-,.- <br /> A-4 <br /> E. Hydraulic calculatio~s s~ecifying outflow volumes ane <br /> . rates for various r2inrc'11 events. <br /> .. ( (2) Adjustmen;:s \']here Parce 1 '0 =&: Is Significantly Different <br /> ..uno _ ~ <br /> From LanG Use Staneard <br /> Ilhere the unit runoff generated by a parcel differs from the <br /> assigned amount for that land use catagory by more than 20% , the <br /> P.\-J.D. may adjust the parcels stars water drainage fee in accor- <br /> dance with the following procedure: <br /> a. Calculation of unit :::-unof:: for the parcel shall be deter- <br /> mined.by the methods outlined ln the Soil Conservation <br /> Service Technical Re.lease No. 55, utilizing a 2" total <br /> rainfall amount and antecedant moisture condition II. <br /> b. If calculated unjt runoff ~s shown to differ from the <br /> assigned amount for that land use catagory by 20% or <br /> more, the number of assigned pxU's for that parcel shall <br /> be adjusted by ~ultiplying by the ratio of the calculated <br /> , . unit runoff to the standard unit runoff. <br /> , fee shall be <br /> c. A parcels storm water drainage subject to <br /> increases as well as decreases by this procedure. <br /> .. <br /> d_ Because single family and duplex fees are not based upon <br /> ,. actual parcel acreage, no adjustments for un~t runoff dif- <br /> .,. ferences will be made for those land uses. <br /> ". ( 3) Procedure for Calcualtion of Credits for .let Ponds <br /> .. ("\ A parcel may be credited for up to fifty (50%) percent of the <br /> storm water drainage fee for onsite measures which are owned ane <br /> I' maintained by the applicant which effectively reduce the outflow of <br /> l_ sediment/nutrients fror.l tne si~e_ Creait percentaae ~nall be bG.seo. <br /> On one-half of the actual t'ercentage of seaiment removal efficiency, <br /> [ as deter~inea oy the following ?roceaure, rounded to the nearest. 5%; <br /> except that no credit will be given for sediment removal efficiencie <br /> l of less than 20?, .. <br /> A. Calculation of C~edits for Net Ponds <br /> i... Determine total site acreage' and percent of site that <br /> a. <br /> has an improved or impervious surface. <br /> ! b. Calculate the annual cepth of rune f f from the followins <br /> L <br /> equation: I ).597 <br /> ! 0 r=P(.75 I +.15)-5.234 (_25-.1875 <br /> m m <br /> ~.~ ("here o = annual depth of runo::::: ~n inches. <br /> r <br /> r" I = percent qi site ~~~ious area, expressed ~ a c8cir:""al~ <br /> ! <br /> L, m <br /> - P = annu~l depth of pr2ci?itation = 29 inches. <br /> , . <br /> . c. Calculate annual volt:..r::e of runo::f in acre-feet: <br /> v = site acreage ~ oj 12 <br /> annual r <br /> c.3.?aci~y elevation in <br /> , \vher('!: <br /> - - --- <br />