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West Elk Mine <br />. will be submitted on a semi -annual basis, beginning when secondary, or retreat mining, begins in <br />the South of Divide Area. Aerial photos taken will be maintained at West Elk Mine. <br />1)Verircation andAccuracv oi'Predictwns <br />In order to verify and demonstrate the accuracy of subsidence predictions, based on the results of <br />past subsidence observations in the Apache Rocks and Box Canyon mining areas, MCC will <br />implement the following procedures to monitor Monument Dam prior to mining. The following <br />procedures will be implemented as soon as permitting allows, in order to account for seasonal <br />precipitation changes. <br />Conduct annual aerial photo surveys of the landslides located north and south of the <br />reservoir, using the July 2004 photos as a baseline reference. Surveys will continue while <br />mining is occurring within Panels EI through E9 <br />2. Install, and measure, survey monuments strategically located on the dam and on the <br />north, south, and east edges of the reservoir to monitor any movement prior to, during, <br />and after mining in the area. During the monument surveys, conduct visual inspections <br />along the monument transects for surface cracks. Monitoring (surveying and inspections) <br />of stations in the Minnesota Reservoir area and across the crest of the Monument Dam <br />will be initiated at least one month prior to mining of Panel E12 or E-1 and continue for <br />two to three months after mining is complete in the panel. MCC will initially survey the <br />monuments on the dam axis quarterly and then monthly when E-seam longwall mining is <br />occurring within one mile of the dam. The results of the surveys will be submitted in the <br />semi-annual subsidence reports. While mining is occurring within the one mile radius, <br />weekly inspections will be made of the dam for cracks or other potentially damaging <br />features and the inspection reports will be included with the semi-annual subsidence <br />reports. The monuments along the dam and reservoir basin will be resurveyed as soon as <br />possible if a seismic event occurs that exceeds the "threshold event" as described below. <br />If, during the inspections, cracks or other potentially damaging features are noted to be <br />occurring in the reservoir basin or dam structure, CDMG, the Minnesota Reservoir <br />Company, SEO, USFS and other appropriate agencies will be notified by MCC <br />immediately and, depending on the severity of the damage, mining may cease until a new <br />mine plan can be approved and mitigation performed. <br />In addition to the survey monuments on the dam, MCC will measure the water level in the <br />piezometers installed in the crest of the dam on monthly basis, April through October, when <br />accessible. The water level measurements will be included in the semi-annual subsidence reports. <br />3. Mining of Panel E9 will be from the south to the north. Monitoring (surveying) of <br />stations to the south of the Minnesota Reservoir and across the crest of the Monument <br />Dam will be re-initiated at least one month prior to mining of Panel E9 and continue for <br />two to three months after mining is complete in the panel. MCC will initially survey the <br />monuments on the dam axis quarterly and then monthly when E-seam longwall mining is <br />occurring within one mile of the dam. The results of the surveys will be submitted in the <br />semi-annual subsidence reports. While mining is occurring within the one mile radius, <br />• weekly inspections will be made of the dam for cracks or other potentially damaging <br />features and the inspection reports will be included with the semi-annual subsidence <br />2.05-166 Revised June 2005 PRIO, Rev. Minch 1006; May 2006 PR/0 <br />