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<br />Geotechnical Adequacy Comments <br />Mt. Gunnison No. 1 Mine Proposed Revision <br />• <br />(1) hlap 3.4.4.A - "NO. 1 Mine Plan" <br />Panel sizes depicted on the amended map have varied from those depicted <br />in the remaining unmodified areas on this life-of-mine map. If so, the <br />entire map should be amended appropriately to demonstrate the projected <br />actual panel sizes throughout the entire mapped area. <br />(2) 1~1ap 3.4.4.8 - "No. 1 Mine Plan - Sequence of Mining" <br />The proposed amended map shdws no mining sequence within the amended <br />5-year permit area.' The scheduling designations must be completed by <br />reindicating the appropriate timing symbols, as is still apparent in the <br />unamended portions of the life-of-mine plan. <br />(3) Exhibit 3.4.8.A - "Subsidence Evaluation for Mt. Gunni~ <br />,.,e <br />The proposed amendment of the mine plan eliminates the specific panel <br />designated for initial high-resolution subsidence monitoring. This is in <br />an extremely critical portion of the originally approved mining plan for <br />the Mt. Gunnison No. 1 Mine's initial 5-year mine permit. The applicant <br />must extensively amend Exhibit 3.4.8.A appropriately, in order to select <br />and justify a new monitoring panel. The original plan, still in effect, <br />designated a panel to be monitored as the first panel to undergo retreat <br />extraction of coal within the mine. Further, the applicant will have to <br />amend the ground water monitoring plans to be installed in conjunction <br />with the test panel, in order to observe potential ground water impacts <br />during retreat mining. The applicant should be reminded that no panel <br />extraction within any panel in the mine is allowed until the subsidence <br />monitoring system's mechanical and hydrologic monitoring appliances are <br />in place. <br />(4) Exhibit 3.5.2.E2 - "14ine P1 an with Proposed Locations of Sea15" <br />The mine plan proposed change necessitates a relocation of the "main <br />portal seal". A generic relocation to an analogous location near the <br />portal entrances is not sufficient, in light of the existing information <br />regarding roof fracturing due to channel sandstone deposits. The <br />applicant should amend the discussions within the text and Exhibit <br />3.5.2.E2 to revise the portal sealing plans appropriately. In addition, <br />a proposed portal seal for the Sylvester vent portals will have to be <br />added to the original plan. <br />(5) Plans for the Future paste Pile <br />• The relocation of the mains may impact the e•aentual, as yet unapproved, <br />future uoper waste pile. The applicant should amend the appropriate <br />portia~.s of the occurrent wniCh address *_he future waste pile. <br />/mt <br />