2010-11-10_REVISION - C1982056

• Permit No: C1982056
• IBM Index Class Name: REVISION
• Doc Date: 11/10/2010
• Doc Name: Adequacy Review
• From: DRMS
• To: Twentymile Coal Company
• Type & Sequence: TR76
• Email Name: JDM
• 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]
November 10, 2010
Mr. Jerry Nettleton
Twentymile Coal Company, LLC
29515 Routt County Road #27
Oak Creek, CO 80467
RE: Foidel Creek Mine (Permit No. C-82-056)
Technical Revision No. 76 (TR-76), Adequacy Review
Dear Mr. Nettleton,
COLORADO
D I V IS I ON OF
RECLAMATION
MINING
SAFETY
Bill Ritter, Jr.
Governor
Mike King
Executive Director
Loretta E. Pineda
Director
The Division received Twentymile Coal Company's (TCC's) application for a technical revision (TR-
73) on October 18, 2010. The application was determined to be complete on October 25, 2010. No
concerns have been received from other agencies regarding this proposed technical revision. The
Colorado Division of Reclamation, Mining and Safety has completed its adequacy review of the
proposed technical revision. Please respond to the following comments or concerns as necessary:
1. The additional drawing and design calculations for Ditch G-6 extension to be inserted into
Exhibit 8J includes design assumptions that do not correspond with the approved design criteria
for Pond G. Please address the following discrepancies in the design inputs.
a) Although the NRCS Storm Type Distributions are considered very conservative, the
common Storm Type for the area of the Foidel Creek Mine would be a NRCS Type II.
This Storm Type is noted on the currently approved Pond G design.
b) According to the approved Pond G design, the Immediate Contributing Area for Pond G
is 467.1 acres with a Peak Discharge at the inlet of the Pond to be 52.39 cfs and 2.21 cfs
at the outlet. However, in the design submittal of the addition of the proposed ditch G-6
extension, the Immediate Contributing Area for Pond G is 9.2 acres with a Peak
Discharge at the inlet of 6.69 cfs and .98cfs at the outlet.
c) The spillway for Pond G is designed as a Perforated Riser with a Riser Diameter of 24",
a Riser Height of 8.8', Barrel Length of 112', and an n value of 0.0250. These inputs
are in contrast to the inputs in the proposed design of a Drop Inlet spillway with a Riser
Diameter of 18', a Riser Height of 15', Barrel Length of 30' and an n value of 0.015.
2. The Division as compiled the attached reclamation cost estimate for the tasks associated with
the reclamation of the Ditch G-6 Extension. This estimate is sufficient to reclaim all areas
associated with the proposed activities under TR76. TCC submitted a reclamation cost
estimate in the amount of $510.00.The Division's total reclamation costs associated with these
activities are estimated to be $703.00. Please acknowledge if TCC concurs with the
Division's estimate.
Office of Office of
Mined Land Reclamation Denver • Grand )unction • Durango Active and Inactive Mines