2011-01-25_REVISION - C1980004 ‎(2)‎

• Permit No: C1980004
• IBM Index Class Name: REVISION
• Doc Date: 1/25/2011
• Doc Name: Review Letter Memo
• From: Kent Gorham
• To: Mike Boulay
• Type & Sequence: PR2
• Email Name: MPB
• Email Name: KAG
• Email Name: SB1
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215 COLORADO
Denver, Colorado 80203 IV IS I ON O F
Phone: (303) 86&3567 Memo RECLAMATION
FAX: [phone] Interoffice MINING
-& -
SAFETY
To: Mike Boulay
From: Kent Gorham f
CC: Sandy Brown
Date: January 25, 2011
Re: Permit Revision No. 2 (PR-02), McClane Canyon Mine, #C-1980-004
have completed my review of Rule 2.05.6(6), Subsidence Survey, Monitoring, and
Subsidence Control for Permit Revision No. 2 (PR-02) for the McClane Canyon Mine. My
review included all of the revised materials submitted, as appropriate and as related to
subsidence. I have phrased my questions directly to the applicant.
Rule 2 05 6(6) Subsidence Survey Monitoring, and Control Plan
Subsidence has the potential, especially in areas of thin overburden, steep slopes, and
cliff outcrops to cause damage to cultural resources, including rock art, rock shelters,
and pictographs. From review of the project location map in Appendix J of the revision
application, it is not clear that areas planned to be subsided were included in the
cultural resources survey. Please identify cliff faces and areas of potential rock art
within the area to be subsided (affected area), show them on a map, and submit the
appropriate resource surveys for those areas so that the Division can forward this
information to the SHPO.
2. Please expand the brief text discussion on page 2.05-71 under Rule 2.05.6(6)(b)(i)(B)
regarding the magnitude of vertical subsidence as it relates to the depth of
overburden. Reference to a map for those areas of high risk of surface cracking would
be helpful.
3. The Division believes that in areas of shallow overburden (<500 feet) and steep
slopes, the potential exists for surface cracks to develop that may be a hazard to
recreational use and grazing. Please consider a plan for periodic monitoring and
mitigation (if warranted), for these areas.
4. Regarding the potential for surface cracking, permit text narrative on page 2.05-71
uses the term "retreat line" as a reference for identifying surface cracking develop
"parallel' to this line. Please modify permit text narrative, explain the orientation of the
retreat line, and/or be more specific on the expected orientation of surface cracks.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines