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Ff <br />' i"'~ <br />,v •M <br />:K-: <br />kerr coal company ~ ; ~j <br />r <br />' Eo•.97 warden, COlaraao 80480 i7J317273721 <br />' Data: <br />' Ms. Patricia A. Ne_son <br />Colorado Department of Health <br />' Water Quality Conc_ol Division <br />42_0 East 11th Ave-_e <br />Dever, Colorado 8C220 <br />' RE: RER~ COAL COMPANY - t*ARR *SINE (PERMIT N0. <br /> COG-350037), REQUEST FOR STORMWATER EXEMD'_':ON <br />' Dear MS. Nelson: <br /> Kerr Coa_ Company (Kerr) owns and previously cpera_ed the <br /> u~rr Mine, located approximately fourteen miles east of the :.own of <br />' waiden, Colorado. ~Sining operations at the mine have ceased and <br /> c':e mine is curre~t.y in an active rec'_amation mode. Dra_~aae and <br /> sediment control for the mining related disturbance is provided by <br />' a number of engineered sedimentation ponds, collection/diversion <br /> ditches, and associated drainage structures. Discharge from the <br /> sedimentat_on ponds is controlled and regulated under applicable <br />' provisions of Per-:~it COG-850037. Discharge for the twelve <br /> ::dividual outfal:s under this permit comes almost exclusively from <br /> sr.owmelt runoff, w'_.h no process water discharge and disc'~arge from <br /> =ainstorms being =are. <br />All sed_::entation ponds are designed and aaintaiaed to <br />crovide a minimum ~e*_ention time of at least 24 hours for retained <br />:Shoff resulting `_rom the 10 year, 24 hour storm eve__^.t. Rrrile the <br />ponds are desigre= to provide adecuate detention tis^.e co allow <br />settlement of suspended solids, due to the characteristics of the <br />dominant soil types in this area both undisturbed and d'_sturbed <br />area runoff typically have relatively high levels of suspended <br />solids. In addit_c:., a relatively high percentage of t::^.e suspended <br />solids in the r~.off are fine colloidal materials whic'~ do not <br />readily settle oLt of suspension. <br />During ~=_riods of high flow due to either s~owm=_lt or <br />rainfall runoff, the noted factors combine to limit tie trapping <br />efficiency of the ax_sting sedimentation ponds with the res;:lt that <br />concentrations o' pertain parameters in pond discharge say exceed <br />applicable effl•= -t limitations. The accompany ~o,'_CCring <br />=eport(s) indicate exceedance of effluent limitations 'or the <br />`ollowing dischar== point (s> , eff'_::ent parameters (s) , a.-.d <br />^onitoring neric~ s) for which an exemption is requested. <br />