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1V4.. J 33rd Ave. V�/.. Sulte 200 <br />'�� Lovell•Sauerland " '.'""'"'°°a. w°S�zo ;;,S.BO;, <br />� ■ ■ & A,Ssociat�3s. Inc. ceoo> ��s•�eea <br />Enqlnosn/Survepon/Plannen/ileralopmanl Consultm�b FAX: (206) 072•7V98 <br />7;�`i:iR� . .K � r � . a� ; ��i � � � „i„i ; y , ; � � M <br />, .. <br />The site wae origmally looked at by thia office in Decenber of 1989 and found to have rivo <br />drair.age bssic�. Etasin No.l had an erea of .62ac. and dreined to the south toward en e�cis6ng <br />detention facility conshucted for the Silver Lake Apartmenta. 'fhia deten6on facility waa <br />origuialiy sized for a developed condition of the D2B site. Basin �10. 2 6nd an area of .142 acra <br />end drained to the north towerd Silva Lake. I have included n c:opy of the originat drainege <br />calculations of the Silver Lake ApartmeMs for your use. Tho pond was to be sized for dvee <br />besins that existed on •he �.partment site. The calculadona show that Baains 1,2 end 4 were <br />detained in the pond. The total storage rnquired was 14537.94 cubic feet. The araount of volume <br />created in the pond was 33,730 cubie feet; a net surplus of 19,192 abic feet. A calculadon for <br />the storage volume on die B2B sita ia enclosed. The RoHo�wl method was used based on 10 year <br />releese, 25 year atorage equations. The atorage volume would be 1075 cubic feet additio�al, <br />based upon this method. <br />./ : 1 '�►I� , 1 . 11► <br />We have elected to use a pipe in combination with e wet pond to meet the water quality <br />requiroment. Sizine� calculadons ere enclosed for your review. The SCS procedure was used to <br />establish th 6 month 24hr flow to be used in the Camp-Hazen formula. A 2 year 24 hour storm <br />was analyud 6rst end a pealc volume calculated for the 2 year devdoped condition of the site. <br />This volume was reduced by multiplying said peek flow volume by 64% to nchieve the 6 month <br />volume. T:�e 6 month volume was then used in the Camp-Hazen formula. 1'he calwlation <br />showed that the volume of the wet vault should be 579.4 cubic fat of dead storage. Eighty-two <br />feet of 36" CMP culvert will be used for this purpose. The pond aiu was calculated by <br />mulGplying .99 times .31 acres of asphalt. The product was then halved and multiplied by 30% <br />for a total volume of 1992 cubic fat of dead storage. All calculations are enclosal . <br />^ v `) ., <br />,:i�, <br />� ��;.`; ��r;u <br />�,r ,�(1�L I � ...;�r <br />% rnfk� <br />av <br />� <br />,C1 <br />G' <br />,� <br />n � ��'l. <br />� <br />�.; rY"� ; <br />„��� �� <br />' �, �j'� <br />,:. <br />DGNFlF.B t��u5—_� <br />..::��.4:;;, .. ;�;�..... <br />