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• ~ • DRAB <br />The applicant proposes a subsidence control plan to prevent material damage due <br />to subsidence of the undermined area. Extraction is to be limited to a <br />maximum of 55~ of the in-place coal. Further, within "safety zones", beneath <br />the structures delineated within the area of potential influence, extraction <br />is to be limited to SOe of the in-place coal. Two methods of pillar stability <br />analysis are presented to demonstrate the adequacy of the designed pillar sizes <br />to bear existing overburden loads. Safety factors are demonstrated to be <br />sufficient in all cases. "Safety zones" are delineated on Map 2.05.6(6)(f)(il)(C)-1 <br />for workings within the "E" seam, and the applicant commits to forwarding <br />analogous "safety zone" delineations for the "D" seam prior to mining commencement <br />within the Red Canyon No. Z mine. In addition, a South African analytical <br />technique is utilized to demonstrate that the mine design should preclude <br />interaction between extraction within the "E" and "D" seams. <br />Finally, the amended application includes the proposal of a monitoring program <br />to verify both mechanical and geohydrological projections. Monitoring wells are <br />in place to observe variations in both alluvial and bedrock aquifer water tables. <br />Map 2.05.6(6)(f)(ii)(C)-1, Sheet 1 of 2, delineates subsidence monuments <br />installed in the field above the underground workings. Atypical monument <br />installation is depicted on Map 2.05.6 (6)(f)(ii)C)-1, Sheet 2 of 2, as well as <br />the surveyed locations, orientations, and elevations of the I2 delineated <br />structures. In addition to the required monitoring of structures, survey monu- <br />ments and water table elevations, Grand Mesa Coal Company commits to the completion <br />of a photographic record of all potentially affected structures. Finally, the <br />applicant commits to the rehabilitation or reconstruction of any affected <br />structure. The Division finds the subsidence aspects of the amended Red Canyon <br />No. 1 and No. 2 mine application to be in compliance with the requirements of <br />the regulations. <br /> <br />