Laserfiche WebLink
West Elk Mine <br /> <br />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; <br /> 12/20- TR149; 12/21- TR150, 1/24-TR152, 2/25-MR486 <br />Based on that survey the actual E-seam angle-of-draw has been conservatively estimated at 16.3 <br />degrees (see appendix B of the Spring 2010 Subsidence Report.) The angle of draw is measured <br />using the greatest vertical distance between the top of the E-seam at the nearest edge of each <br />longwall panel and the ground surface elevation equal to the point of no discernable subsidence. <br />As such, the conservative approximate limit of the maximum predicted E-seam angle-of-draw is <br />19 degrees. <br />To document subsidence features, MCC conducts visual surveys, and any necessary traditional <br />surveys, semiannually each year and provides the information in a written subsidence report by <br />the end of September and April each year. A summary of the visual observations and monitoring <br />is provided in first and fourth quarter letter reports to CDRMS and to the USFS. If any mechanical <br />response is detected during these visual inspections that is not consistent with what has been <br />previously observed, MCC will notify CDRMS within ten working days of our observations. <br />The Spring and Fall reports of the visual surveys will include photographs to document any <br />subsidence features, including cracks, rockfalls, landslides, revegetation, and other relevant <br />features. A map will also be included that identifies the location of the photographer and the aspect <br />of the image for each photograph. An additional map will be prepared that identifies the location <br />and extent of the observed features. MCC will attempt to revisit previously identified subsidence <br />features to note any changes that have occurred since the previous visit. MCC will also attempt to <br />replicate the aspect of the photographs taken previously to document the progression of subsidence <br />and subsequent healing. The discussion of the field observations will in particular address the <br />development and healing of the subsidence features, utilizing the photographic documentation. In <br />addition, MCC will discuss baseline conditions observed in areas prior to undermining. The report <br />will document how the inspection was conducted, and include such observations as weather and <br />ground conditions. <br />In addition to performing the visual surveys, aerial or other type photos will be taken prior to <br />beginning mining in an area, periodically during mining, and after mining when subsidence is <br />complete to document landslides, rockfalls, vegetation, etc. over the areas being mined. This <br />documentation will provide a broader, more extensive view from which to associate or assess <br />landslide and other surface activity due to mining. <br />1)Verification and Accuracy of Predictions <br />In order to verify and demonstrate the accuracy of subsidence predictions, based on the results of <br />past subsidence observations in prior mining areas, MCC will implement the following procedures <br />to monitor Monument Dam prior to mining. The following procedures will be implemented as <br />soon as permitting allows, in order to account for seasonal precipitation changes. <br />1. 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 LWE16 and LWE17. <br />2. Install, and measure, survey monuments strategically located on the dam and on the north, <br />south, and east edges of the reservoir to monitor any movement prior to, during, and after <br />mining in the area. During the monument surveys, conduct visual inspections along the <br />monument transects for surface cracks. Monitoring (surveying and inspections) of stations