2013-05-22_REVISION - M1990057

• Permit No: M1990057
• IBM Index Class Name: REVISION
• Doc Date: 5/22/2013
• Doc Name: ADEQUACY REVIEW #1
• From: DRMS
• To: OPERATOR
• Type & Sequence: TR4
• Email Name: MAC
• Email Name: TAK
• 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]
May 22, 2013
Nick Michael
Union Milling Company, LLC
P.O. Box 620490
Littleton, CO 80162
STATE OF COLORADO
COLORADO
D IV IS I ON OF
RECLAMATION
MINING
SAFETY
John W. Hickenlooper
Governor
Mike King
Executive Director
Loretta E. Pineda
Director
Re: Leadville Mill; DRMS File No. M -1990 -057; Technical Revision No. 4 — Adequacy
Review No. 1
Dear Mr. Michael,
The Division of Reclamation, Mining and Safety (Division) has completed its adequacy review
of your Technical Revision to the above referenced permit. The Technical Revision was received
and called complete for review on May 16, 2013. The decision date for this Technical Revision
is June 17, 2013. Please be advised that if you are unable to satisfactorily address any
concerns identified in this review before the decision date, it will be your responsibility to
request an extension of the review period. If there are outstanding issues that have not
been adequately addressed prior to the end of the review period, and no extension has been
requested, the Division will deny this Technical Revision.
1. The Division has reviewed the Applicant's proposed methods for addressing the perched
aquifer which was discovered under the tailings storage facility (TSF). The Division's
primary concern is with the long -term stability of the TSF and the structural integrity of the
composite liner. Two of the proposed methods of remediation temporarily eliminate the
inflow of groundwater and allow for installing the geosynthetic clay liner (GCL) without
premature hydration. However, since there is not a defined gradient to the groundwater flow,
it is not clear where the water will be routed. Saturation of the toe of the TSF could
potentially lead to failure of the impoundment.
The Division has concluded the only suitable option for addressing the perched aquifer is to
install a sub - surface drain along the seep. Please respond.
2. The Applicant has provided a detail drawing for the sub - surface drain. Specify the average
flow of groundwater which has been observed in the seep. In addition, please explain how
the dimensions of the sub - surface drain were selected.
3. The Applicant has stated the leak detection system will be tested after it has been installed.
Please describe the testing process.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines