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AMERICAN <br />ENVIRONMENTAL <br />AECCONSULTING, LLC <br />April 7, 2009 <br />Mr. Donald MacDonald <br />Manager, Energy Services <br />Coors Energy Company <br />P.O. Box 467 <br />Golden, Colorado 80402 <br />Re: Evaluation of Remaining and Required Reclamation Overburden Volumes <br />Proposed Technical Revision to Approximate Original Contour <br />Coors Energy Company-Keenesburg Mine Facility, Permit No. C-1981-028 <br />Dear Mr. MacDonald: <br />Coors Energy Company (CEC) has contracted American Environmental Consulting, LLC (AEC) <br />to provide engineering consulting services for the Keenesburg Mine Facility located in Weld <br />County, Colorado (facility). This letter report proposes a revision to the approved contours in <br />the long-term spoil area (LTSA). The approximate original contours (AOC) were modified by <br />Technical Revision 34, dated November 22, 2002 from CEC to the Division of Minerals and <br />Geology. Since that time, further refinements of the topographic measurements and volume <br />calculations has shown there to be a need to prepare a technical revision to these contours to <br />result in additional overburden material for use in reclamation of the B-Pit and for drainage <br />design purposes. The remaining and required LTSA overburden volumes are summarized <br />below: <br />Current Calculated Remaining Overburden Volume (265 372 bcy): The current remaining LTSA <br />overburden volume was evaluated using the following surfaces: 1) 2008 surface topography of <br />the LTSA, and 2) LTSA bottom of topsand. The bottom of topsand, or top of final overburden <br />surface, is fifteen inches below the approximate original contour (AOC) as defined in the facility <br />permit (Permit No. C-1981-028). The LTSA contains approximately 265,372 bank cubic yards <br />(bcy) of overburden available for reclamation activities. <br />Current Required LTSA Soil Volume (323,470 bey): The required LTSA overburden volume <br />was evaluated based on the B-Pit final and periodic cover volumes. The required overburden <br />volume for the final B-Pit cover (6-feet thick) was evaluated using the following surfaces: 1) 13- <br />Pit top of ash surface and 2) B-Pit bottom of topsand surface. The B-Pit final cover overburden <br />volume is approximately 217,648 bcy. Approximately 9,688 bcy of overburden is used annually <br />as periodic cover in B-Pit based on an average of the recent cover volume usage. It is currently <br />anticipated that ash disposal operations will continue for another 11.8 years resulting in a <br />required overburden volume of 105,822 bcy for periodic cover. Therefore, the total required <br />LTSA soil volume is estimated to be approximately 323,470 bcy. <br />There is a resulting shortfall of approximately 58,098 bcy in the volume of soil available versus <br />the volume of soil required using the contours approved as per Technical Revision 34. In order <br />to balance the remaining and required LTSA overburden volumes, AEC proposes slightly <br />modifying the AOC in the LTSA area as shown on the attached contour map. On average, we <br />propose an additional 0.88 foot excavation over the LTSA area although the actual excavation <br />6885 South Marshall St., Suite 3, Littleton, CO 80128 phone 303-948-7733 fax 303-948-7739 <br />pr(jecls/coons eneno;1200511ethnical revision/technical revision AEC leper rev 4 2009