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.~ <br />'4'"" <br />kerr coal company `L~ <br />' poa =87 waiaen, coiorac~ c0aB0 ~ f3031 713~7Z1 <br />rr <br />Dat=_: <br />' Ms. ?atricia A. Nelson <br />Colorado Decartment of Health <br />Water Quali=_r Control Division <br />4210 East 1:ch Avenue <br />Denver, Corrado 80220 <br />' ecE: RERR COAL COMPANY - .ERR MINE (P?c'c?"="' \0 <br />COG-850037) , REQUES': FOR STOR7~1ATE3 EX=•'tiLDTION <br />' Dear M5. Nelson: <br />;err Coal Company (Kerr) owns and prev_cus_y oc=_rated tae <br />' Marr Mine, :coated aaproximatsly fourteen miles east of tae town of <br />Walden, Co'_o=ado. Mining operatio-s at the :nine nave ceased and <br />the mine is currently in an active reclamation mode. Drainage and <br />sediment co^.trol for the mining related disturaa.^.ce is provided by <br />a number of engineered sedimentation ponds, co~lec~ion/diversion <br />ditches, a:.3 associated drainage structures. Discharge from the <br />' sedimentat_on ponds is controlled and regulated under applicable <br />provisions of Permit COG-850037. Discharge :or the twelve <br />individual outfalls under this permit comes almost exclusively from <br />s:.owmelt r•,::.off, with no process water discharge and discharge from <br />rainstorms being rare. <br />all sedimentation Donds are designed a^.3ra=ntained to <br />provide a .-.i:.imum detention time of at least 24 ;,curs for retained <br />runoff resulting from the 10 year, 24 hour storm event. While the <br />ponds are 3esigned to provide adecuate det=_^tion t:^e to allow <br />settlement of suspended solids, due co the charac=er_stics of the <br />dominant soil types in this area both undisturbed and disturbed <br />area runoff typically have relac_vely high levels of suspended <br />solids. _: addit_or., a relat_vely Nigh percencace of tae suspended <br />solids in the runoff are f_ne colloidal materials which do not <br />readily settle out of suspension. <br />During periods of high fow due to Biter snowmelt or <br />rainfall ^.:noff, tae noted factors combine to li.-~it the trapaing <br />officienc•: of the existing sedimentation ponds wife ~::e result that <br />concentra..oas of certain parameters in pond disc^arge may exceed <br />aAD1lCable effluent limitations. The accc:;.pany monitoring <br />reoort(s! indicate exceeda-ce of effluent li^~itat_ons for the <br />_`ollowinc discharce point(s;, effluent para.:.eterscsl, and <br />:nonitorir_ periodis) fOr WY._ca an exemption .S r°_~.:25ted. <br />