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~. <br />To: <erica.crosby@state.co.us> <br />Cc: <br />Bcc: <br />From: "William R Hotchkiss, Supervisor~+ Hydrologist, Denver, CO "<ho <br />Subject: Re: Research on Peak Flow Reduction <br />Date: Thursday, December 5, 1996 9:52:55 MST <br />Attach: <br />Certify: N <br />Forwarded by: <br />Dear Erica, <br />I am passing your request and information on to Ken wahl, the <br />Central Region Surface Water Specialist. He is presently out <br />of town, but should return at the end of the week. I will see <br />that he sees your note as soon as he returns. <br />I am sure that we can provide some help and guidance. <br />---hotch--- <br />On Thu, 5 Dec 96 8:55:06 MST <br />erica.crosby@state.co.us said: <br />> Dear Mr. Hotchkiss, <br />> I spoke with you briefly at the CMC meeting last night regarding possible <br />> research done on peak flow reduction due to detention basins. I work with <br />> the Department of Natural Resources; Division of Minerals and Geology. In my <br />> program we regulate coal mining in the state. There is a reclaimed coal mine <br />> located north of the town of Meeker (Meeker Area Mines). The operator of the <br />> mine has submitted a revision to reconstruct Curtis Creek (they previously <br />> diverted the drainage around a series of sediment ponds). The reconstructed <br />> channel will pass through the sediment ponds. Our rules require that the <br />> emergency spillway can safey pass the 25-year, 24-hour storm event. The peak <br />> flow for the 25-year event is roughly 600 cfs. The 100-year event is over <br />> 2000 cfs. <br />> The problem that we face is that there are rougly 50 detention basins in the <br />> 9 square mile water shed. The 600 cfs number did not take these ponds into <br />> consideration due to the time it would take to model each pond. I am looking <br />> for any research that has been done that documents effects of small <br />> structures on peak flow. I did find some research done in Texas which <br />> concludes that if a pond has an emergency spillway, the peak discharge is <br />> reducted by appx. 50$ due to the effects of spillway storage in the pool. <br />> When there is no spillway flow, the reduction in peak discharge is about 98$. <br />> I appreciate your help in this matter. If you have any questions, I can be <br />> reached at 866-3567. <br />> Sincerely, <br />> Erica S. Crosby <br />> Environmental Protection Specialist <br />