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kern coal company <br />00. X87 w~iae~, coio.~do BW80 17071717J7]f <br />' Date: s~~SS <br />' Ms. Patricia A. Nelson <br />Colorado Department of Health <br />Water Quality Control Division <br />' 4210 Eut 11th Avenue <br />Denver, Colorado 80220 <br />1 <br /> <br />1 <br />~] <br /> <br /> <br /> <br />1 <br /> <br /> <br />1 <br />1 <br /> <br />Re: Rerr Coal Company - Mur Mine (Permit No. COG850021), Request (or Stormwater <br />Exemption <br />Deu Ms. Nelson: <br />Kerr Coal Company (Kerr) owns and previously operated the Marr lfine, located approximately <br />founeen miles eu[ of the [own of Walden, Colorado. Mining operations at [he mine have <br />ceued and the mine is currently in an uZive reclamation mode. Drainage and sediment control <br />for the mining related disturbance is provided by a number of engineered sedimentation ponds, <br />collection diversion ditches, and usocia[ed drainage structures. Discharge from the <br />sedimentation ponds is controlled and regulated under applicable provisions of Permit COG <br />850021. Discharge for the twelve individual outfalls under this permit comes almost exclusively <br />from snowmelt runoff, with no process water discharge and discharge from rainstorms being <br />rue. <br />All sedimentation ponds are designed and maintained to provide a minimum detention time of <br />at lent 24 hours for retained runoff resulting from the 10 year, 24 hour storm event. While the <br />ponds ue designed to provide adequate detention time to allow settlement of suspended solids, <br />due to the charaaeristia of the dominant soil types in this un both undisturbed and disturbed <br />area runoff [ypially have rela[ively high levels of suspended solids. In addition, a relatively high <br />percentage of the suspended solids in the runoff ue fine colloidal materials which do not radily <br />settle out of suspension. <br />During periods of high (low due to either snowmelt or rainfall runoff, the noted favors <br />combine to limit the trapping efficienry of the existing sedimentation ponds with the result that <br />concentrations of certain puame[ers in pond discharge may exceed applicable effluent <br />limitations. The accompanying monitoring repon(s) indiate exceedance of effluent limitations <br />for the following dischuge poin[(s), effluent puameter(s), and monitoring period(s) for which <br />an exemption is reques[ed. <br />Discharge Point Parameter(s) Exceeding Limitation Discharge Rate(cfsl Date s <br />9Gy %SS / /mot O. iC Yrs <br />1 <br />