2011-08-30_REVISION - C1982056 ‎(3)‎

• Permit No: C1982056
• IBM Index Class Name: REVISION
• Doc Date: 8/30/2011
• Doc Name: Adequacy Review
• From: DRMS
• To: Twentymile Coal Company
• Type & Sequence: TR77
• Email Name: JDM
• Media Type: D
• Archive: No

DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
August 30, 2011
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. 77 (TR -77), Adequacy Review
Dear Mr. Nettleton,
STATE OF COLORADO
John Hikenlooper
Governor
Mike King
Executive Director
Loretta E. Pineda
Director
The Division received Twentymile Coal Company's (TCC's) application for a technical revision (TR-
77) on August 9, 2011. The application was determined to be complete on August 19, 2011. No
concerns have been received from other agencies regarding this proposed technical revision as of the
date of this letter. 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 proposed drawing and design calculations for the 15LT rock lined diversion ditch and the
proposed access road culvert to be inserted into Exhibit49Y includes design assumptions that
are not generally used for this area. Please address and validate the following discrepancies
in the design inputs.
Office of
Mined Land Reclamation
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.
The NRCS Type I storm used in the submitted model changes the cfs design discharge
used.
b) Inputs utilized to develop a design discharge of 6.74 cfs were not included in the
designs for the trapezoidal rip rapped ditch and the proposed culvert. Please include
these data to support the use of the design discharge.
2. The following maps were not included in the TR -77 application and will require an update to
reflect the proposed activities. Please provide revised versions of the following maps to
incorporate into the PAP.
a) Map 23 — Mine Plan
b) Map 24 Sheet 3 and Sheet 4 — Surface Facilities and Freshwater Systems
c) Map 29 — Reclamation Map
COLORADO
D I V I S I O N O F
RECLAMATION
MINING
—&—
SAFETY
Office of
Denver • Grand Junction • Durango Active and Inactive Mines