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<br />kerr coal company <br />00.487 wa~een, coio~~eo 80480 Im1177]J721 <br />t Da[e• 8~~3 <br />' Ms. Patricia A. Nelson <br />Colorado Depanment of Halth <br />Water Quality Control Division <br />4210 East 11th Avenue <br />Denver, Colorado 80220 <br />' Re: Rerr Coal Company • Mur Mine (Permit No. COG850021), Request for Stormwater <br />Exemption <br />' Dear Ms. Nelson: <br />Kerr Coal Company (Kerr) owns and previously operated the Marr Mine, )oared approximately <br />fourteen miles eut of the town of Walden, Colorado. Mining operations at the mine have <br />ceued and the mine is currently in an active reclamation mode. Drainage and sediment con[rol <br />for [he mining related disturbance is provided by a number of engineered sedimentation ponds, <br />' collection diversion ditches, and usociated drainage structures. Discharge from the <br />sedimentation ponds is controlled and regulated under appliable 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 ue designed and maintained to provide a minimum detention time of <br />at least 24 hours for retained runoff resulting from the 10 year, 24 hour storm event. While the <br />ponds are designed to provide adequate detention time [o allow settlement of suspended solids, <br />due to the characteristia of the dominant soil types in [his ua both undisturbed and disturbed <br />t area runoff typically have relatively 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 no[ readily <br />settle out of suspension. <br />' During periods of high flow due to either snowmelt or rainfall runoff, the noted factors <br />combine to limit the trapping efficiency of the existing sedimentation ponds with the result that <br />' concentrations 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 pazameter(s), and monitoring period(s) for which <br />' an exemption is requested. <br />Discharge Point Parameter(s) Exceeding Limitation Discharge Ratefcfsl Date s <br />' .TO% ~ ~ ~ G. aG ~ <br />1 <br />