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<br />kerr coal company <br />box 487 ~ Walden, Colorado 80480 ~ 13031 723-4721 <br />H <br />Date: <br />Ms. Anne Iltlenfeldt <br />cc: Randall P. Price III IIIIIIIIII~IIIII <br />sss <br />~~ <br />~.. <br />RE.CEIVEQ <br />MAY 0 6 1993 <br />Colorado Department of Health Div+swta a! Mu+e+a+s ~ GeUlugy <br />Water Quality Control Division <br />4210 East 11th Avenue <br />Denver, Colorado 80210 <br />Re: Rerr Coal Company - Mazr Mine (Permit No. COG850021), Request for Stormwater <br />Exemption <br />Dear Ms. Ihlenfeldt: <br />Kerr Coal Company (Kerr) operates the Marr Mine, located approximately fourteen miles east <br />of the town of Walden, Colorado. Drainage and sediment control for the mining related <br />disturbance is provided by a number of engineered sedimentation ponds, collection diversion <br />ditches, and associated drainage srrutxures. Disrltazge from the sedimentation ponds is <br />controlled and regulated under applicable provisions of Permi[ COG850021. Dischazge for the <br />twelve individual outfalls under this permit comes exclusively from either precipitation or <br />snowmelt runoff, with no process water discharge. <br />All sedimentation ponds are designed and maintained to provide a minimum detention time of <br />at least 24 hours for retained runoff resulting from the 10 yeaz, 24 hour storm event. While the <br />ponds are designed [o provide adequate detention time to allow settlement of suspended solids, <br />due to the characteristia of the dominant soil types in this area both undisturbed and disturb:d <br />area runoff typically have relatively high levels of suspended solids. In addition, a relatively high <br />percentage of the suspended solids in stormwater runoff are fine colloidal ma[erials which do <br />not readily settle out of suspension. <br />During periods of high flow due to either snowmelt or precipitation runoff, the noted factors <br />combine to limit the trapping efficienry of the existing sedimentation ponds with the result that <br />Total Suspended Solids (TSS) and Settleable Solids concentrations in pond dischazge may exceed <br />applica le effluent limitations. The accompanying monitoring report(s) for pond(s).~~9t' <br />indicate exceedance of TSS and/or Settleable Solids limitations for the corresponding <br />monitoring period. Exceedance of applicable permit effluent limitations resulted from: <br />^ Discharge from rainfall runoff occurring within 48 hours after measurable <br />precipitation has stopped <br />Discharge from snowmelt runoff occurring within 48 hours after runoff inflows <br />to the pond(s) have stopped <br />Documentation of precipitation and snowmelt occurrence and snowmelt inflows to the ponds <br />is retained at [he minesite and is available for inspection by au[horized agency representatives. <br />