2011-08-19_REPORT - C1980007 ‎(3)‎

• Permit No: C1980007
• IBM Index Class Name: REPORT
• Doc Date: 8/19/2011
• Doc Name: Fall 2010 Subsidence Report DRMS Review Memo
• From: DRMS
• To: File
• Permit Index Doc Type: Subsidence Report
• Email Name: TAK
• Media Type: D
• Archive: No

vegetation, etc.
2.05.6(6I(i))(F)
Yes
The traverses in the Fall 2010 study included observations of new and previously identified
subsidence features. The report describes changes to the previously existing features that have
occurred since previous visual inspections.
Monument Dam:
2.05.6(6)(d)(i)
Yes
The Fall 2010 report describes recent surface subsidence activity, including: a) lessening of
rockfall and slabbing in the West Flatiron area, b) no new subsidence features in the Box
Canyon area, c) rockfall has largely ceased on the east side of Sylvester Gulch since the Fall
2008 report, d) mining induced cracks in soft material at methane drainage wells pads (some
features have been regraded), e) complete or partial healing of some of the subsidence cracks
found during previous reporting periods. These impacts are consistent with the subsidence
prediction in the permit application.
Photographed landslides to north and south of dam
either by air or other method, annually.
2.05.6(6)(d)(i)
Yes
Surveyed monuments on dam and on north, south,
and east edges of reservoir, premining through
postmining. Frequency: Dam axis either quarterly
E -1 or E -12 longwall mining was not within one mile of Monument Dam
or annually (conflicting text in permit), then monthly
during part of the report period; therefore, monthly monitoring and weekly
when E -seam longwall mining is within 1 mile
(frequency on reservoir edges is unspecified).
- visual inspections were not required (permit page 2.05 -156).
Seismic monitoring reports have been submitted for the 3rd and 4 quarters
Visually inspected monument transects (dam and
reservoir edges) for cracks, 1 month through 2 to 3
months after mining in E -1 or E -12. (Frequency not
Yes
of 2010 and DRMS previously reviewed those reports.
Appendix D of the Spring 2010 report contains the required annual photos
specified in permit.)
of the landslides to the north and south of the dam.
Measured water levels in dam crest piezometers,
monthly Apr — Oct, when accessible.
Visually inspected dam structure for cracks, weekly
while longwall mining is within 1 mile.
Resurveyed monuments on dam and reservoir edges
ASAP when seismic event has PGA >0.15 g.
Conducted sufficient post-
mining monitoring to
verify subsidence
prediction
2.05.6(6I(i))(F)
Yes
The traverses in the Fall 2010 study included observations of new and previously identified
subsidence features. The report describes changes to the previously existing features that have
occurred since previous visual inspections.
Accurately predicted
subsidence.
2.05.6(6)(d)(i)
Yes
The Fall 2010 report describes recent surface subsidence activity, including: a) lessening of
rockfall and slabbing in the West Flatiron area, b) no new subsidence features in the Box
Canyon area, c) rockfall has largely ceased on the east side of Sylvester Gulch since the Fall
2008 report, d) mining induced cracks in soft material at methane drainage wells pads (some
features have been regraded), e) complete or partial healing of some of the subsidence cracks
found during previous reporting periods. These impacts are consistent with the subsidence
prediction in the permit application.
Prevented imminent or
actual material damage or
diminution of use of
renewable resource lands
2.05.6(6)(d)(i)
Yes
2