REP35860

• Permit No: C1980007
• IBM Index Class Name: Report
• Doc Date: 8/18/1988
• Doc Name: MT GUNNISON 1 MINE SUBSIDENCE MONITORING DATE SUBMITTAL 4/88 PERMIT C-80-007
• From: MLRD
• To: SUSAN MOWRY
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

III IIIIIIIIIIIIIIII STATE OF COLORADO
Roy Romer, Gove
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Director
DATE: August 18, 1988
T0: Susan Mowry
FROM: Jim Pendleton ~"`U
RE: Mt. Gunn' n No. 1 e'Subsidence Monitoring Data Submittal - 4/88
(Permit i1C-80-007)
I have finally reviewed the letter report submitted by West Elk Coal Company
last April. This letter report presents the reduced survey data from the
subsidence monitoring monuments installed above panels 1W1S and 1W2S at the
Mt. Gunnison No. 1 underground coal mine. The subsidence monitoring is
important to West Elk Coal Company, because future mining permissions are
conditioned upon the results of this survey monitoring program. The operator
proposes to mine beneath potentially critical renewable resource lands, and it
is imperative that they demonstrate that their impacts can be controlled
through a subsidence control plan. They have proposed to utilize limited
extraction techniques,
To date the monitoring results appear to verify their original predictions
contained within the permit documents. Maximum subsidence as of September,
1987, a minimum of one year after retreat mining in the two subject panels was
1.9 feet in the middle of panel 1W1S and 2.2 feet in the middle of panel
1W2S. These magnitudes of vertical subsidence are less than the values
projected within the original permit subsidence prediction. Final results mdy
warrant the revision of the original projection subsidence factors for
purposes of future mine planning.
With the exception of one apparently errant point, Monument No. 15, the
monuments located above the South Main Intakes appear to show insignificant
vertical movement, less than the error limits of the survey techniques
employed. Monument No. 15 appears to have dropped 0.68 feet, which appears
unlikely. Monuments on either side of No. 15 show negligible movement. It is
possible that the survey was in error or that some non-subsidence related
factor is responsible for the apparent movement, such as frost heave, local
slope movement, monument wildlife interference, etc. I recommend that you
relate this apparent anomaly to Dennis Conn, West Elk's environmental
coordinator along with a suggestion that they investigate the possible causes
of anomalous movement of Monument No. 15.
The data presented appears to have been properly collected. The data
presentation is concise and understandable. After the two 1988 surveys are
completed, the operator should be able to draw same credible conclusions
regarding the character of ground subsidence above the Mt. Gunnison No. 1
underground workings.
215 Centennial Building, 1313 Sherman Street Denver, Colorado 802032273 Tel. [phone]