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Ryan Pawlowski <br />0?9 Colowyo Coal Company x <br />- 5731 State Highway 13 <br />k <br />CO 8 <br />6 <br />9 201 ' <br /> 1 <br />41 <br />er, <br />Mee <br />w <br />O <br />e s„ <br />o <br />0 <br />November 8, 2010 <br /> Mr. James R. Stark <br /> Environmental Protection Specialist <br /> Colorado Division of Reclamation, Mining and Safety <br /> Department of Natural Resources <br /> 1313 Sherman Street, Room 215 <br /> Denver, CO 80203 <br /> <br />RE: Technical Revision No. 87, East Pit Sediment Control Structures and Spoil <br />Grading Map Update, Colowyo Coal Mine, Permit No. C-1981-019.- Changes <br />Pursuant to CDRMS PAR letter October 14, 2010 <br />Dear Mr. Stark, <br />Enclosed please find Colowyo's revised TR-87 application. The application is being <br />resubmitted in its entirety. The changes derive mostly from comments you provided in <br />your October 14, 2010 PAR letter as well as a minor modification that were discovered <br />separately, as described below. <br />Specifically, we are including in this re-submittal four SEDCAD analyses within Exhibit 7, <br />Item 14R "East Pit Reclamation Sequencing and Ditch Designs for Prospect Ditch, North <br />Tributary East Pit Ditch and Final East Pit Ditch." Three of these reflect a very minor <br />change from the previously submitted models for the 10 year, 24 hour storm for the <br />three distinct reclamation time frames (2010, 2012 and 2017) included in the September <br />23, 2010 submittal. We corrected an error wherein the upper reaches of the Prospect <br />Ditch had been modeled as riprap lined, when if fact they are vegetation lined. The <br />impact on calculated flows and volumes delivered to Prospect Pond in the worst case <br />scenario from a sediment control perspective were negligible, but have been <br />incorporated into the new models, tables, and text included in this submittal. That is the <br />only change to the three previously submitted SEDCAD models. <br />The fourth SEDCAD model included in this submittal is new, and was run in response to <br />Comment No. 8 to demonstrate that the Prospect Pond spillway system was capable of <br />safely discharging the 25 year storm. <br />Colowyo has finished reviewing the Division's Preliminary Adequacy Review comments <br />received by Colowyo on October 21, 2010. Colowyo's responses are as follows: <br />Colowyo Coal Company, L.P. • 5731 State Highway 13 • Meeker, CO 81641 <br />T + 1 970 824 1578 • F +1 970 824 1598 • http://prospect.riotinto.org/irj/portal