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~Se$/v'i/tg Our Clients Since 1980 <br />YY <br />• ~~ Engineering <br />A DIVISION OF WESTERN WATER CONSULTANTS. INC. <br />Civil Environmental Mining Water F,esources <br />61 I Skyline Roud Laramie. Wyoming 83070 (307) 7d~-003I FAX 1307) 721 ?913 E-mail: infolar@wwcengineering.com <br />July 30, 2002 <br />Mr. Crellin Scott <br />Colowyo Coal Company L.P. <br />5751 State Highway 13 <br />Meeker. CO 81641 <br />RE: Colowyo Impoundment Evaluation, Taylor Pump Holding Pond <br />Dear Mr. Scott: <br />WWC Engineering (WWC) has performed an evaluation of the Taylor Pump Holding <br />Pond at the request of Colowyo Coal Company. The information provided by Colowyo Coal <br />Company indicates that the Taylor Pump Holding Pond is nor. a sediment control structure. <br />Water is either diverted into the pond or pumped into the pond from the Wilson Reservoir. The <br />pond capacity is approximately two acre-feet. The Taylor Pump Holding Pond is bermed as <br />required by MSHA, which prevents precipitation that does not fall directly over the pond from <br />entering the pond. The Taylor Pump Holding Pond will remain after mining is completed. <br />Therefore, WWC performed a TR-60 Emergency Spillway Evaluation and TR-60 Emergency <br />Spillway Freeboard Evaluation. <br />This submittal includes the following attachments. <br />I. Sedimentation Pond Redesign Taylor Pump Holding Pond. This drawing depicts <br />the post-mining topography and the SEDCAD 4 watershed dissection. <br />2. SEDCAD 4, Taylor Pump Holding Pond TR-60 Emergency Spilhcay Evaluation. <br />The Taylor Pump Holding Pond was assumed to be a Class B pond for a TR-60 <br />Emergency Spillway Evaluation. The rainfall amount used for this model was the <br />] 00-year. 6-hour amount plus O.12 times the difference behveen the probable <br />maximum 6-hour amount and the 100-year. 6-hour amount. The model shows the <br />spill\\ay is adequate to meet the TR-60 criteria for a Class B structure. The probable <br />maximum precipitation vcas determined from H(vIR 49. <br />U7 t f Elr 1-(>C-I %'l U--~ S <br />18-197tna Al your lu%Ia.I Frta Slrccl 'U1 \ndrr Drier. Suin•',: <br />ShrriJan. \1'comin~ 8-'8111 Gflloua. Ri'oining 3_? 10 Ciqur. \\-coming 8'6U1 <br />Phone i311716T_-11761 Phunc 1307168_'-IStill Phunc 11117117&_'7117 <br />Fas 13071671-1_'6? Pas 131171 68'_-__'i7 Fax I IU71 '_37-118'_8 <br />E-mail: inlb>hrClewcenginecrinn.amr E-moil: inlil,~l1 C~ lrmrcngineering.mm G-mail. intbc~p@\e xecnginttring.ttmr <br />Po11a Block BuilJinf <br />7 \Yca b'" Al roue. Suite -lE <br />Hclenn. \lomm~a >96(11 <br />Phony IJ061 x-17-396 <br />Fa~11061117-1?ii <br />E-moil: in&1hW @wwccnginrrrin _.com <br />