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1 L~ 1 I~ 1 kern coal company boa a87 ~ wsltl~n, cOlaWO 80980 I7p71 723721 Date• ~3 Ms. Patricia A. Nelson Colorado Department of Health Water Quality Control Division 4210 East 11th Avenue Denver, Colorado 80220 .~ ~Ja~ ~' RE: RERR COAL COMPANY - MARR MINE (PERMIT N0. COG-850037), REQUEST FOR STORMWATER fi70afi'D?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.miae have ceased and the mine is currently in an active reclamation made. Drainage and sediment control for the mining related disturbance is provided by a number of engineered sedimentatioa ponds, collection/diversion ditches, and associated drainage structures. Discharge from the sedimentation ponds is controlled and regulated under applicable provisions of. P°_-mit COG-850037. Discharge for the twelve individual outfalls under this permit comes almost exclusively frcm snowmelt runoff, with no process water discharge and discharge from rainstorms being rare. All sedimentation ponds are desigaed and maintained to provide a minimum detention time of at least 24 hours far retained runoff resulting from the 10 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 ceriods of high flow due to either saawmelt 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 periods) for which an exemption is requested.