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~. ~. kerr coal company box 687 ~ Walden, colarado 80480 ~ 1303) 723~721~ Date: Ms. Patricia A. Nelson Colorado Department of Health Water Quality Cont.ol Division 4210 East 11th Avenue Denver, Colorado 80220 - ''-~++ ~II'I~I~Ii I~II~I II~ ~~~ ~ RE: KERB COAL COMPANY - MAAR NIINE (PERMIT N0. COG-850037), REQUEST FOR STORMWATER EXERTION Dear Ms. Nelson: Kerr Coal Company (Kerr) owns and previously operated the Marr Mine, located approximately fourteen miles east of to town of Walden, Colorado. Mining operations at the mine have ceased and the mine is curre.^.tly in an active reclamation mode. Drainage and sediment control for the mining related disturbance is provided by a number of engir_eered sedimentation ponds, collection/diversion ditches, and associated drainage structures. Discharge from the sedimentation ponds is controlled and regulated under applicable provisions of P_zmit COG-850037. Discharge for the twelve individual outfalls under this pezmit comes almost exclusively frcm snowmelt runoff, with no process water discharge and discharge from rainstorms being rare. All sedimentation ponds are designed and maintained to provide a minimum detention time of at least 24 hours for retained runoff resulting from the 10 year, 24 hour storm event. While the ponds are designed to provide adecuate detention time to allow settlement of suspended solids, due to the characteristics of the dominant soil types in this area both undisturbed and disturbed area runoff typically have relatively high levels of suspended solids. In addition, a relatively high percentage of t'~e suspended solids in the xw^.off are fine colloidal materials which do not readily settle out of suspension. During periods of high flow due to either snowmelt or rainfall runoff, the noted factors combine to limit the trapping efficiency of the existing sedimentation ponds with the result that concentrations of certain parameters in pond discharge may exceed applicable effluent limitations. The accompany monitoring report(s) indicate exceedance of effluent limitations for the following discharge point(s), effluent parameters(s), and monitoring pericd:s) for which an z~cemption is reque=_ted.