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<br />kerr coal company <br />Do. a87 wa0<n, co~a.oo BOa80 ~ Un71727~721 <br />Date• b~9~s,3 <br />' Ms. Pa[ricia A. Nelson <br />Colorado Department of Health <br />Water Quality Control Division <br />' 4210 Eut 11th Avenue <br />Denver, Colorado 80220 <br />' Re: Kerr Coil Company - Mur Mine (Permit No. COG-850021), Request for Stormwater <br />Exemption <br />' Deu Ms. Nelson: <br />Kerr Coil Company (Kerr) owns and previously operated the Mur Mine, loafed approximately <br />' fourteen miles eut of the town of Walden, Colorado. Mining operations at the mine have <br />ceased and the mine is currently in an active reclamation mode. Drainage and sediment control <br />for the mining related disturbance is provided by a number of engineered sedimentation ponds, <br />t collection/diversion ditches, and associated drainage struRUres. Discharge from the <br />sedimentation ponds is controlled and regula[ed under appliable provisions of Permit COG <br />850021. Discharge for the twelve individual outfalls under this permit comes almost exclusively <br />' from snoa•mel[ runoff, with no process water discharge and discharge from rainstorms being <br />rue. <br />' All sedimentation ponds ue 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 [o provide adequate detention time to allow settlement of suspended solid; <br />due to the chuaaeristia of the dominant soil types in this uca both undisturbed and disturbed <br />' area runofftypically have relatively high levels of suspended solids. in addition, a relatively high <br />percrntage of the suspended solids in the runoff ue fine colloidil materials which do not radily <br />settle out of suspension. <br />1 During periods of high flow due to either snowmel[ or rainfill runoff, the noted factors <br />combine to limit the trapping efficiency of the existing sedimentation ponds with the result that <br />' concentra[ions of certain parameters in pond discharge may exceed appliable effluent <br />limitations. The accompanying monitoring report(s) indiate exceedance of effluent limitations <br />for the following discharge point(s), effluent puameter(s), and moni[oring period(s) for which <br />' an exemption is requested. <br />Discharge Point Parameters Exceeding Limitation Discharge Rate(cfsl Date s <br />3Oy ~.l~ G. G9 f'r~ <br />