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STATE OF COLORADO <br />D?vi?on? o? ??ci?M?a??a?v, M?>v??? ??D ???r?r <br />Department o? Natural Resources , <br />13 i 3 SE?erman StF, Room 2? 5 <br /> <br />Denver, Colorado $0203 C O L O R A D O <br /> <br />Phone; (30?? s??-???? <br />INTER??+ ?X?+ N?E?RAI1IDUlVI D i v I S I 0 N O F <br />R??LA.hr?.ATI?N <br />i=A?: (?O?a 832#8? o? I N I N <br /> &? <br /> SAS ETA' <br />DATE: June ? ? <br />???? Bi[1 Ritter, fir. <br /> ? Governor <br /> <br />T?: <br />,Iim stark <br />dandy Brown <br />and Marcia Talvitie Harris D. Sherman <br /> , <br />, ?xecut?ve Director <br /> Ronald w. Cattar?y <br />??++ l111? <br />?`?lJl!'1'. ? d <br />Ike Boulay ?IVi51on Director <br /> Natural Resource Yrustee <br /> Oolowya 1Vline ?Ferit Na. -S 1-a 19} <br /> Technical Revision ?a. 7? QTR-??} <br />I have reviewed the EDOAD design submitted far the South Taylor Haul Raad Ditch, I <br />also reviewed 1VIap ?5 showing the location, longitudinaX profile and crass-section of <br />the haul raad..Tust a single ditch design was provided for the ditch to be located in ? cut <br />slope clang the western edge ofthe haul rand. There are no culverts proposed because of <br />the configuration of the road with na other significant drainage or road crossings. <br />The ditch design is adequate anal I found no major flaws. The ditch is to be constructed <br />in competent rock and the design is conservative with ? feet of freeboard. Mare than 7a <br />percent ofthe contributing area to the ditch will be from the undisturbed slope above the <br />ditch. A low curve number was used far the undisturbed drainage to the ditch resulting <br />in very little runoff from this sub watershed, which is deemed appropriate. The sub- <br />watersheds far the ditch design are not delineated on reap but this is not a significant <br />concern because there i no flow going to a sediment panel. <br />The road is assumed to have a slight crown over the centerline resulting in half of the <br />road surface shedding water westward to the auth Taylor Haul Road Ditch, and the <br />ditch ?s adequately designed to handle this flow. One concen? that I have is that due to <br />the crown half of the running surface will shed water eastward aver the fill slope. This <br />may result in the embankment becoming saturated over tirrie and could result in <br />embankment failure or slide damage below the road fill. This is the sarrie situation that <br />happened at the Yoast Mine at Haul Rand D contributing to significant slope failure <br />above Fond ? 1 ?. one of the mitigation measures employed at the Panel ? ? 2 slide was to <br />entirely cant the rand surface back to the ditch so that runoff could no longer saturate the <br />road filllembanknment, I think t11iS should be periodically field checked at the South <br />Taylor Haul Rand embankment to ensure that there is not significant e?osian or saturation <br />of the road fill occurring. <br />?olowya has inet all of our design criteria far the road ditch and Z have no comments to <br />be forwarded to the operator. Please let me know if you have questions, <br />Denver File <br />Office of Office of <br />Mined land Reclamation Deaver i Grand ]unctl?r? • Durango Active and Inactive Mines