2013-07-25_REVISION - M1990057

• Permit No: M1990057
• IBM Index Class Name: REVISION
• Doc Date: 7/25/2013
• Doc Name: TR-04 ADEQUACY REVIEW NO. 2
• From: DRMS
• To: OPERATOR
• Type & Sequence: TR4
• Email Name: MAC
• 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]
July 25, 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. Plneda
Director
Re: Leadville Mill; DRMS File No. M -1990 -057; Technical Revision No. 4 — Adequacy
Review No. 2
Dear Mr. Michael,
The Division has identified several other comments and questions that must be addressed prior to
the Division's decision due date. 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 application.
1. The Division has reviewed the Applicant's proposal to install a geonet over the seeps in the
tailings storage facility (TSF) in order to control the flow of water and prevent the premature
hydration of the geosynthetic clay liner. The Applicant has estimated that the inflow of water
from the identified seeps is approximately 8 gpm, which is a decreased flow from what was
observed during the last construction season in 2012. The rate of inflow is largely dependent
on the amount of snow received during the winter and the subsequent melting of the snow
pack. The Leadville area has experienced below average snow pack over the past several
years. The observed inflow from the seeps could substantially increase during a year where
snowpack is average or above average. Furthermore, if inflows are increased the extent
(height and width) of the seeps could also be increased. Finally, the geotechnical
investigation conducted by CTL Thompson stated that the area encompassed by the TSF is
over lower permeability clays.
The Division requires the submittal of the following information in order to adequately
analyze this proposal:
a) Provide documentation which demonstrates that the transmissivity of the geonet is
adequate to handle up to 3 times (24 gpm) the amount of inflow which has been
observed.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines