2010-03-11_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 3/11/2010
• Doc Name: Preliminary Adequacy Letter
• From: DRMS
• To: Colowyo Coal Company
• Type & Sequence: TR81
• Email Name: JRS
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
11 March 2010
Ms. Jennifer Sekulski-Barton
Colowyo Coal Company, LP
5731 State Highway 13
Meeker, CO 81641
Re: Colowyo Mine C-1981-019
Preliminary Adequacy Letter - Technical Revision 81
Dear Ms. Sekulski-Barton:
COLORADO
D I V I S ION O F
RECLAMATION
MINING
SAFETY
Bill Ritter, Jr.
Governor
James B. Martin
Executive Director
The Colorado Division of Reclamation, Mining and Safety (Division) has received the Colowyo
Coal Company, LP's (Colowyo) responses to the Division's 14 September 2010 Incompleteness
Letter for Technical Revision 81 - South Taylor Fill and PMT Changes. The Division deemed
the revision complete on 28 December 2009. The Division has reviewed the materials submitted
and has the following adequacy questions.
Rule 2.05.3(6) - Overburden
Section 2.05.3(6)(c) lists the requirements for the geotechnical investigation of a
proposed disposal site. Bedrock characteristics; adverse geological conditions; locations
of springs and seeps; and rock drain material characteristics have been successfully
addressed in previous Shannon and Wilson studies for the South Taylor area. With
respect to (iii), potential effects of subsidence, Shannon and Wilson issued an opinion in
Addendum No. 2 (November 2008) that highwall mining will not significantly affect spoil
foundation conditions and should not reduce the global stability of the spoil fill. With
TR-81, the dimensions (lateral and vertical) of the temporary and excess spoil fills have
been enlarged. The issue of potential subsidence has not been addressed in the October
2009 Shannon and Wilson study. Please address the potential effects of subsidence of
the subsurface strata due to highwall mining activities, considering the proposed
redesigned configurations of permanent and temporary excess spoil fills.
2. In the Division's incompleteness question 1, the Division questioned the change in the
swell factor, on Page ST/LW-Rule 4, Page 20, from 20% to 15%. Colowyo's response
was that the decrease in swell was due to the fact that the materials in the permanent spoil
piles are being moved by the truck/shovel operation rather than the dragline (which is the
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