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<br />Aug-2S-9S ll:l6A Love & Assoc#6739796 <br /> <br />P.Ol <br /> <br />RECEIVED <br />AUG 2 8 1998 <br /> <br />t=.~.. ~~im~"I~e <br /> <br />641 fl'.Hlt Slreet <br />~,,~ul~v'lle. ::~lk~I(J(jn Suo:?? In':'1 <br />F'hon'tl (:;0;:) 0/3 91('5 f/IX (JlJ'.,) ",i:~ 'il''"" <br />E mOil: I('Neo~,ocia1c:;!'.((.,I&:;5~' er:!n-l <br /> <br />Colorado Water <br />Conservation Board <br /> <br />Memorandum <br /> <br />To: <br /> <br />Vince Auriemma, City of Black Hawk <br /> <br /> <br />Roger Pelerson, Love & Associates, Inc'l( <br /> <br />August 28, 1998 ' <br /> <br />From: <br /> <br />Date: <br /> <br />RE: <br /> <br />9505A24 - Design Discharge Recommendation, 300 Main Street Offsile Flows <br /> <br />On July 30, 1998, a storm over Unnamed Draw (Draw) in Black Hawk, Colorado resulted in flood- <br />induced property damage to the Golden Gate Casino. The Colorado Waler Conservalion Board estimated <br />a peak discharge of sediment and water equal 10 300 cfs in the Draw from Ihis slorm event. The Colorado <br />Waler Conservation Board indicates approximately 30 per cent of the 300 cfs is sediment, meaning the <br />clear water flood peak discharge equals approximately 210 cfs. The 100-year storm peak for clear water <br />in the Draw using City of Black Hawk drainage design criteria is 190 cfs, reasonably close to the 100- <br />year flood peak the Draw which occurred during the storm. <br /> <br />The 300 Main Slreet Casino is required to pass the 100-year peak discharge from both Unnamed Draw <br />plus an approximately 14 acre basin area to the east below Main Street. Construction of the Casino <br />cannot proceed until construction plans for the passage of these offsile flows have been approved. The <br />Casino representatives have expressed a desire to proceed with their project without delay. <br /> <br />Although 300 Main Street Casino plans sediment capture devices for Unnamed Draw, the volume of <br />sediment captured by these proposed devices has not been quantified by the consultant. It is assumed the <br />volume provided for sediment capture should be approximately equal to the volume of sediment <br />transported by Ihe Draw during the recent storm. Although the contractor who removed Ihe sediment <br />deposited by the Draw has been asked to provide an estimate of the volume of sedimenl removed, this <br />information has not been received, and the time required to evaluate the infonnation is unknown. If 300 <br />Main Street Casino wishes 10 proceed with their project immediately, we recommend a design discharge <br />of 340 cfs be used for the diversion. This estimate includes 300 cfs estimated by the Colorado Waler <br />Conservation Board plus a contribution of 40 cfs from the 14 acre offsite area. <br /> <br />cc: Steve Ferris <br />A.J. Zabbia <br />Rich Segro <br />Larry Dezman <br />Larry Lang <br />