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kern coal company ~ ~ ~~ <br />r <br />' bo* ,97 ~ waiCen, caoraaa e0d80 ~_0~) 7274721 <br />' Date: 9 <br />' Ms. Patricia A. Ne_son <br />Colorado Detartet:t of Health <br />Water Quality Co~troi Division <br />' 4210 East 11th Ave,ue <br />Denver, Colorado 80220 <br />R°: K'ai~~ COAL COMPANY - ~.LR MINE (=='~MIT N0. <br />CGL-95D037) , REQUEST ?OR STO&~TATER EX_"'M~TION <br />' Dear MS . Neacr.: <br />Kerr Cca_ Company (Kerr) owr._= and prev'_ously cperated the <br />' Marr Mine, =ocate3 approximately fount=_en miles =_ast of t::e town of <br />Walden, Coicradc. Mining operatics at the m'^e have ceased and <br />the mine is turn=_-t_y in an active re.'amatior..;:ode. Drainage and <br />' sediment control for the mining related disturbance is prcvided by <br />a number of enc:-eered sedimentat_c:^ ponds, collection/diversion. <br />ditches, and associated drainage str•~ctures. Discharge from the <br />' sedimentation por.3s is controlled a.^3 regulated under applicable <br />provisions of ?e^mit COG-850037. Discharge for the twelve <br />individual outfal:s under this permit comes almcst exclusively from <br />snowmelt r.:.:of'_, w'_th no process water 3ischarge and discharge from <br />rainstorms bei-a rare. <br />All sedi,•nentation ponds ar=_ designed and aaintained to <br />provide a min'_^^~m detention time of at least 24 hours for retained <br />runoff result:..*.c from the ZO year, .4 hour stcr-i eve..^.t. While the <br />ponds are de_'_c::e3 to provide ade•~~ate det=_rtion t ~e to allow <br />settlement of s::s~ended solids, due to the characteristics of the <br />dominant sail tomes in this area bcth undist::rbed a_*d disturbed <br />area runoff tvp_cally have relative_y high levels of suspended <br />solids. I:, add_t:o:., a relatively ^_gr. percentage of tie suspended <br />solids in the r•,:.-off are fine col_oidal mat=_vials wr_ich do not <br />readily se*_tle cat of suspension. <br />Dur.^~ p=_riods of high f=aw due to either snowmelt or <br />rainfall -uno_", the noted factors combine to limit the trapping <br />efficiency of tie eeisting sedimentation ponds with the result that <br />concentrat:o^.s cf certain parameters in pond 3ischarge may exceed <br />applicable eff:~e-t limitations. The accompany monitoring <br />report(s) i.^.d:cats exceedance of effluent limitations for the <br />following 3iscar=e point(s), ef'_:•_ert para.^=_t:rs(s1, and <br />:monitoring oer:c3 sl for which ar. a=rtmcion .s requested. <br />14~< <br />_~'~ <br />