2022-09-29_PERMIT FILE - C1980007A (3)

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West Elk Mine monuments on the dam axis quarterly and then monthly when E-seam longwall mining is occurring within one mile of the dam. The results of the surveys will be submitted in the semi-annual subsidence reports. While mining is occurring within the one mile radius, weekly inspections will be made of the dam for cracks or other potentially damaging features and the inspection reports will be included with the semi-annual subsidence reports. The monuments along the dam and reservoir basin will be resurveyed as soon as possible if a seismic event occurs that exceeds the "threshold event" as described below. If, during the inspections, cracks or other potentially damaging features are noted to be occurring in the reservoir basin or dam structure, CDRMS, the Minnesota Reservoir Company, SEO, USFS and other appropriate agencies will be notified by MCC immediately and, depending on the severity of the damage, mining may cease until a new mine plan can be approved and mitigation performed. In addition to the survey monuments on the dam, in cooperation with Minnesota Canal & Reservoir Company, MCC will measure the water level in the piezometers installed in the crest of the dam on monthly basis, April through October, when accessible. The water level measurements will be included in the semi-annual subsidence reports. 3. Mining of panels LWE16 and LWE17 will be from the south to the north. Monitoring (surveying) of stations to the south of the Minnesota Reservoir and across the crest of the Monument Dam will be re -initiated at least one month prior to mining of panels LWE16 and LWE17 and continue for two to three months after mining is complete in the panels. MCC will initially survey the monuments on the dam axis quarterly and then monthly when E-seam longwall mining is occurring within one mile of the dam. The results of the surveys will be submitted in the semi-annual subsidence reports. While mining is occurring within the one mile radius, weekly inspections will be made of the dam for cracks or other potentially damaging features and the inspection reports will be included with the semi-annual subsidence reports. The monuments along the dam and reservoir basin will be resurveyed as soon as possible if a seismic event occurs that exceeds the "threshold event" as described below. If, during the inspections, cracks or other potentially damaging features are noted to be occurring in the reservoir basin or dam structure, CDRMS, the Minnesota Reservoir Company, SEO, USFS and other appropriate agencies will be notified by MCC immediately and, depending on the severity of the damage, mining may cease until a new mine plan can be approved and mitigation performed. 4. The landslide feature that is located on and is part of the left (south) abutment will be monitored for movement when mining is within the angle of draw. MCC will install survey monuments within the landslide on the hill to the south of the dam and within the toe of the landslide. These monuments will be surveyed monthly, when accessible, during the months of February through July (if accessible) when movement due to high soil moisture content would be expected. The monuments will be surveyed once every three months in the period of August to January (if accessible) when soil moisture content is expected to be lower. If a seismic event equal to or greater than the threshold event for the Monument Dam as described below occurs, the monuments will be inspected for movement. The results of the survey will be submitted to CDRMS in the semi-annual subsidence report. If movement along the landslide appears to potentially damage the 2.05-118 Rev, 06/05- PRIO, 03106- PR10, 05/06- PR10, 111060- TR107, 04/07- TR108, 09/07- PR12, 02,108- PR127 11/10- MR372; 10i20- MR-452; 12120- TRI49772/21- TR150