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DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866 -3567 <br />FAX: (303) 832 -8106 <br />Mined Land Reclamation <br />MEMO <br />From: Tom Kaldenbach <br />To: File <br />West Elk Mine (C- 1980 -007) <br />Report <br />Seismic Monitoring Reports for 1 2nd, 3 rd, and 4 quarters 2010 and <br />1 quarter 2011 <br />Date: August 19, 2011 <br />Re: Summary of DRMS Review <br />STATE OF COLORADO <br />Loretta E. Pineda <br />Director <br />MCC's Subsidence Monitoring Plan requires monitoring of seismicity for identifying the <br />magnitude of seismic events at Monument Dam (Sections 2.05.6(6(b)(ii), (6)(c(ii), and <br />(6)(e)(iii) of the permit application). MCC began longwall mining in the E seam in the <br />4 quarter of 2008. MCC is required to make field measurements of monuments on the <br />dam within two days of any mining- caused seismic event that exceeds peak ground <br />acceleration of 0.15 g at the dam (permit application page 2.05 -168). An accelerometer <br />at the dam continuously monitors seismic activity. Data from the Monument Dam <br />accelerometer and nine other accelerometers installed at the West Elk Mine and Bowie II <br />Mine enable determination of the geographic location and depth of each seismic event. <br />The above - referenced reports indicate the peak ground accelerations at the dam during <br />the quarters cited did not exceed the 0.15 g threshold. <br />cc: Kathy Welt, DRMS <br />COLORADO <br />D I V I S I O N O F <br />RECLAMATION <br />MINING <br />— &— <br />SAFETY <br />John W. Hickenlooper <br />Governor <br />Mike King <br />Executive Director <br />Office of Office of <br />Denver • Grand junction • Durango Active and Inactive Mines <br />