Laserfiche WebLink
?.�ter tt:e desica �r�, grour.d slope and g.- •nd .cover have <br />beea dete�ined foz :i1e site, t::e allowable ..at:lov rate in <br />c�s per acre can be dete-�ined by inte�olation f=oa tahles 2 <br />t.�rouah 5. If a site contains t�o types uf grounZ cove:, fo: <br />exa�ple, then a se�azate interrolation is aade for eac:� c:ccnd <br />eover t.r�e ar.d t'�e results added to dete�ine t`:e total <br />allocrable out�locr rate in c:s pe= acre. <br />?,fter t.he alloc:able out=lo�t rate in c�s/ac=e is calcslated, <br />t.he requ=_red detention i:i c.ibic Eeet per ac=e is dete�ined by <br />inte^olation froa table 6 or 7. Again if t�o c:ound cover <br />types are pronosed after develoncsent, a senarzte i:te Yo?ation <br />is �ade for ezch cround cover type ar.d the res•�lt adc'ed to <br />cete yiae the total detention recuirenent in cubic :eet ne: <br />ac.e. The deteaLion reauire�ent is thea dete�iae.�. by <br />aultiplying by the site area in ac:es. <br />For residential subdivisions t':e actual extent o: g:ound cover <br />t•�es �till not be ]cioW-n duriag �lan revier�t. Bzsed u�on a <br />sur�ey of exis:i.^.g ho�es in the EVerett area, �'�e ave= ge <br />aacwz� o: iape^�ious s•,L �ace pe= s;nqle �a�ily let _s 2s0o <br />sct:a=e Peet. The anolicant should, t':ere�ora, Wu'-t'-�'-Y �god <br />�v t.4e . uane: of lots and then zcd t:e restt? � tc we area of <br />iane=rious su:=ac� containe3 �:i�.4ia any necr road c�ns�=1c`ec <br />for the s•sbaiv_sicrr to est;xate `�e arez of ��e= rious s•.L=aca <br />t'�a� ai11 ulti�ztely be contaiaed wi:h'-a the o1a�.. •. <br />LX2.TJ��: . <br />Give.^.: a 3.0 acr= garcel located w;t`�i. :ior'�.� C_e=�c <br />Drainage Basin. The slope,of overland floc� is 3.5k. T1:e <br />existing ground cnver cor.sists of 2.o acres of forestad <br />lar.d and 1.o acre o£ lignt grass and s�arsa `.==es. The <br />progosed land use is co�aercial �ti�.h 5� lar.cscapinq and <br />95� impe*_vious grcund cover condi�ions. <br />Solution: Frca table l, t`�e desicn st�rs c=ite='=a is a 5 yezr <br />pre-fievelopmeat stor� and 25 year post develccaeat stora. <br />Froa tz�le 2 the allo<.ra�1e release rate Por t�e :ores�e3 <br />portion o� t:�e site is by in�e�olaticn .085 c�s/zc. The <br />allocrable r=lease rate �or tae crass zrea is .z30 c�s per <br />acre. The total allocrzble release rzte is th===For' <br />(2)(.085) =(1)(.230j or 0.50 c�s. T:�is is .133 c�s ne: <br />ac=e. From table 7, t:�e cetentiun recuir=�ent for t`�e <br />landscaning area and i�oe=�ious area is HSS c�/ac�e and <br />4009 c`_/acre, respectively. T7e +�ota1 det�ntion <br />reauire�aent is (.95) (3) (4009) -�- (•Qs) (3) (sas-) 'ar- i.i,ssa <br />ci. <br />