PERMFILE66120

• Permit No: C1981028A
• IBM Index Class Name: Permit File
• Doc Date: 12/10/2003
• Section_Exhibit Name: Appendix R Disposal/Reclamation Activities
• Media Type: D
• Archive: Yes

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Tetra Tech EM Inc.
1099 18th Street, Suite 1960 ~ Denver, CO 80202 ~ (303) 295- I I OI ~ FAX [phone]
August 19, 2002
Mr. Donald MacDonald
Manager, Energy Services
Coors Energy Company
P.O. Box 467
Golden, Colorado 80402
Re: Evaluation of Remaining and Required Reclamation Overburden Volumes
Proposed Revision to Approximate Original Contour
Coors Energy Company-Keenesburg Mine Facility
Weld County, Colorado
Tetra Tech EMI Project Number P2197.100
Dear Mr. MacDonald:
Coors Energy Company (CEC) has contracted Tetra Tech EM Inc. (Tetra Tech) to provide engineering
consulting services for the Keenesburg Mine Facility located in Weld County, Colorado (facility). This
letter report proposes a revision to the approximate original contour (AOC) in the long-term spoil pile
(LTSP). This proposal is based on an evaluation of remaining and required reclamation overburden
(spoil} volumes previously conducted by another CEC consultant (BE&K/ferranext). Using AutoC~ID
Land Development Desktop (CAD) software and triangulated irregular network (TIN) surfaces to
represent various reclamation surfaces, the evaluation indicated that the LTSP currently contains
approximately 77,000 bank cubic yards (bey) of overburden that in excess of what will be needed for
reclamation activities. The remaining and required LTSP overburden volumes are summarized below:
Remainine Overburden Volume (527,000 bcy): The remaining LTSP overburden volume was
evaluated using the following surfaces: 1) 2001 topography "tp01" and 2) LTSP bottom of topsand
"fin-2". The bottom of topsand, or top of final overbwden surface, is fifteen (1 S) inches below the
approximate original contour (AOC) as defined in the facility permit (Permit No. C-81-028). The
LTSP contains approximately 527,000 bank cubic yards (bey) of overburden available for
reclamation activities.
Required Overburden Volume (450,000 bcv): The required LTSP overburden volume was evaluated
based on the B-Pit final and periodic cover volumes. The required overburden volume for the final
B-Pit cover (6-feet thick) was evaluated using the following surfaces: 1). B-Pit top of ash swface
"ash-a" and 2) B-Pit bottom of topsand surface "tps l." The B-Pit final cover overburden volume is
approximately 360,000 bey. Approximately 9,000 bey of overbwden is used annually as periodic
cover in B-Pit. It is currently anticipated that ash disposal operations will continue for another ten
(10) years resulting in a required overburden volume of 90,000 bey for periodic cover. Therefore, the
total required overbwden volume was estimated to be approximately 450,000 bey.
In order to balance the remaining and required LTSP overburden volumes, Tetra Tech proposes vertically
raising the AOC by approximately 2.75 feet in the LTSP area. This approach reduces the remaining
overburden volume to approximately 450,700 bey, thereby balancing the remaining and required
overburden volumes. In addition, this approach appears to be consistent with the facility Reclamation
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