2024-06-25_PERMIT FILE - C1980007A (4)

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West Elk Mine 2.05-117 Rev. 06/05- PR10, 03/06- PR10, 05/06- PR10, 11/060- TR107, 04/07- TR108, 09/07- PR12, 02/08- PR12; 11/10- MR372; 10/20- MR-452; 12/20- TR149; 12/21- TR150, 1/24-TR152 aforementioned survey was submitted to the Division with the semi-annual subsidence report. To verify the subsidence angle-of-draw in the SOD mining area, MCC completed a baseline survey of the first E-seam panel, prior to the start of longwall mining, with survey-grade GPS equipment. Based on that survey the actual E-seam angle-of-draw has been conservatively estimated at 16.3 degrees (see appendix B of the Spring 2010 Subsidence Report.) The angle of draw is measured using the greatest vertical distance between the top of the E-seam at the nearest edge of each longwall panel and the ground surface elevation equal to the point of no discernable subsidence. As such, the conservative approximate limit of the maximum predicted E-seam angle-of-draw is 19 degrees. To document subsidence features, MCC conducts visual surveys, and any necessary traditional surveys, semiannually each year and provides the information in a written subsidence report by the end of September and April each year. A summary of the visual observations and monitoring is provided in first and fourth quarter letter reports to CDRMS and to the USFS. If any mechanical response is detected during these visual inspections that is not consistent with what has been previously observed, MCC will notify CDRMS within ten working days of our observations. The Spring and Fall reports of the visual surveys will include photographs to document any subsidence features, including cracks, rockfalls, landslides, revegetation, and other relevant features. A map will also be included that identifies the location of the photographer and the aspect of the image for each photograph. An additional map will be prepared that identifies the location and extent of the observed features. MCC will attempt to revisit previously identified subsidence features to note any changes that have occurred since the previous visit. MCC will also attempt to replicate the aspect of the photographs taken previously to document the progression of subsidence and subsequent healing. The discussion of the field observations will in particular address the development and healing of the subsidence features, utilizing the photographic documentation. In addition, MCC will discuss baseline conditions observed in areas prior to undermining. The report will document how the inspection was conducted, and include such observations as weather and ground conditions. In addition to performing the visual surveys, aerial or other type photos will be taken prior to beginning mining in an area, periodically during mining, and after mining when subsidence is complete to document landslides, rockfalls, vegetation, etc. over the areas being mined. This documentation will provide a broader, more extensive view from which to associate or assess landslide and other surface activity due to mining. 1)Verification and Accuracy of Predictions In order to verify and demonstrate the accuracy of subsidence predictions, based on the results of past subsidence observations in prior mining areas, MCC will implement the following procedures to monitor Monument Dam prior to mining. The following procedures will be implemented as soon as permitting allows, in order to account for seasonal precipitation changes. 1. Conduct annual aerial photo surveys of the landslides located north and south of the reservoir, using the July 2004 photos as a baseline reference. Surveys will continue while mining is occurring within panels LWE16 and LWE17.