2011-08-30_REVISION - C1982056 ‎(2)‎

• 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: TR78
• 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. 78 (TR -78), Adequacy Review
Dear Mr. Nettleton,
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 16LT proposed access road culvert to be
inserted into Exhibit 49Z includes design assumptions that are not generally used for this area.
Please address and validate the following discrepancies in the design inputs.
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.
Office of
Mined Land Reclamation
STATE OF COLORADO
John Hickenlooper
Governor
Mike King
Executive Director
Loretta E. Pineda
Director
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) The TR -78 Application proposes 6 culverts to be installed along the 16LT access road.
Designs and drawings for only two culverts were included with the application package.
Please provide design details for all structures associated with drainage and sediment
control.
c) Structure detail was included for a trapezoidal erodible channel; however there was no
network structure included that involved the erodible channel. Please describe the use
of the channel and at what point the channel is utilized in the modeling network.
d) It is noted that diversion ditches are to be utilized for sediment and drainage control at
the 16LT pad. Please provide designs or drawings to confirm that these diversions are
adequate per Rule 4.05.3(7).
COLORADO
DIVISION OF
RECLAMATION
MINING
— &—
SAFETY
Office of
Denver • Grand Junction • Durango Active and Inactive Nunes