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<br />keys coal company <br />• eo,+a7 ~ ...a.n.rn~o..ao eo~eo ~ ~.iW17n.4721 <br />Dace: O 9 <br />M9. Patricia A. Ne_s:a <br />Colorado Departure=: t: Health <br />Water Quality Cont_c? Division <br />410 East lath Avet_e <br />Denver, Colorado "e ;;220 <br />~~ <br />RE : ~~t OJAL COMPANY - MARK MIDiE ( PERMIT NO . <br />COG-a°J037), REQIIEST e0R STORI~IATER EXEMPTION <br />Dear Ms. Nelson: <br />Kerr Cca_ Company (Kerr) awns and previously operated the <br />M3rr Mine, located a~roximacely fourteen miles east of cs town cf <br />Walden, Colorado. )lining aperacions at the mine have ceased and <br />t.*.e :nine is cur_~~__v in an active rec.amation mode. Drainage and <br />sediment control fc= the mining related disturbance is provided by <br />• a number of engi=eered sedimentation ponds, collection/diversion <br />ditches, and asscc:aced drainage stractures. Discharge from the <br />sedimentation ponds is controlled and regulated under a=plicabie <br />provisions of Psrit COG-850037. Discharge for the twelve <br />individual autfal_s Bader this permit canes almost exclusively fresn <br />s;.owmelt runoff, w:~ no process water discharge and discharge from <br />rainstorms being ra_-e. <br />All se~'~-,*_tation ponds are 3esigaed and maintained co <br />provide a tnina.m~am is=ention time of at least 24 hours for retained <br />ivnaff resultin? _..:a[ the i0 year, 24 'your stozm event. While the <br />ponds are desicrs-_ to provide adequate detention time co alloy <br />settlement of susa~ced solids, due .o the characteristics of tha <br />dominant soil t~~es in this area bath undisturbed and disturbed <br />area runoff typic~''_y have relatively high levels of suspended <br />solids. In addi::~», a relatively higi: percentage of t*e suspended <br />solids in the r_-___ are fine colloidal materials which do not <br />readily settle oc: of suspension. <br />Durinc ce:iods of high flow due to either saawmelt or <br />rainfall runof :a noted factors combine to limit the trapping <br />ef.iciency of c:e _Y:sting sedimentation ponds with the result that <br />concentrations o~ ~=stain parameters in pond discharge may exceed <br />• applicable ef:i;:e.-: limitations. The accompany monitoring <br />=eport(s) indica=: exceedance of ef`_luenc limitations for the <br />oilowinc disc::a;_:a coint(s), ef:lue~- parameters(s), and <br />.-czitoring per:cd _. °or which an a:c_.^.:ption is request. <br />