2018-09-04_PERMIT FILE - C1980007A (40)

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West Elk Mine • longitudinal axis. The points on these two transverse lines will be placed on approximately 100 foot spacing within the panel (see figure 21A and Map 68) then at approximately 50 foot intervals within approximately 100 feet of the inside edge and for at least 700 feet past the outside edge of the panel. If the survey is initiated at the beginning of mining of a longwall panel, the first segment of the longitudinal axis survey will be conducted using the monument spacing prescribed for the transverse line surveys. In essence, the initial survey monument will be located at least 700 feet outside the edge of the panel on the longitudinal axis followed by monuments being placed on the axis at approximately 50 foot intervals to a point located at least 100 feet inside the end of the panel. The next monument within the panel will then be placed approximately 300 feet further into the panel along the longitudinal axis. A discussion on how the verification will be made is discussed under the heading Verification and Accuracy of Predictions below. In addition to the GPS surveys, MCC will conduct visual surveys, and any necessary traditional surveys, semiannually each year and provide the information in a written report by the end of September and April each year. A summary of the visual observations and monitoring will be provided in a quarterly letter report to CDMG 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 CDMG within ten working days of our observations. The 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. For the original F Seam and B Seam monitoring program, conventional ground surveying techniques were applied for surveying the former monument _rid, as sho vii on Map 29. The surveys were designed to achieve horizontal accuracy's complying with ti-_ i i.S. Deoartment of Commerce's '`Second order-, Class Il" surveving standards, and vertical accuracy's no less thail 0.2 feet. Grids were surveyed twice prior to the initiation of subsidence. A IIlinimuill of six trian,aulation benchmark monuments outside the area of anticipated subsidence effects were selected and established. Monitoring of the grid was discontinued in 1999. Subsidence monitoring reports will be submitted on a semi -annual basis, beginning when secondary, or retreat mining, begins in the South of Divide Area. Aerial photos taken will be maintained at West Elk Mine. 2.05-164 Revised June 2005 PRIG, Rev. Alm -ch 2006; Alai, 2006 PRIO, A'ov. 2006TR107,Apri12007TR108; Sep. 1007 PR7 2; Feb. 2008 PR -12