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1 kerr coal company I ~. ~,,i boa 487 ~ waldan, Colorado 80480 ~ 13031 723•721 ~~ r Date: -3 Ms. Patricia A. Nelson Colorado Department of Health Water Quality Control Division 4210 East 11th Avenue Denver, Colorado 80220 ' AE: KERR COAL COMPANY - MARR MINE (PERMIT N0. COG-850037), REQUEST FOR STORMWATER EXII+~TION ' Dear Ms. Nelson: Kerr Coal Company (Kerr) owns and previously operated the Marr Mine, located approximately fourteen miles east of the town of Walden, Colorado. Mining operations at the mine have ceased and the mine is currently in an active reclamation mode. Drainage and ' sediment control for the mining related disturbance is provided by a number of engineered sedimentation ponds, collection/diversion ditches, and associated drainage structures. Discharge from the ' sedimentation ponds is controlled and regulated under applicable provisions of Permit 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 iO year, 24 hour storm event. While the ponds are designed to provide adequate 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 the suspended solids in the runoff 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 period(s) for which an exemption is requested.