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<br />Geotechnical Adequacy Comments <br />Rules 2.05.3(6)(a) and 4.08: Blasting Plans <br />Staff inspections have determined that blasting techniques, such as <br />.stemming and sequency of detonation, have been modified at the operations ~.; <br />currently permitted under permit number 79-177, which is referenced as <br />proof of conformance within this application. The appropriate amendments <br />to the existing permit number 79-177 must be accomplished prior to <br />approval of this revision application. <br />Rules 2.05.3(9) and 4.09: Underground Development Waste <br />The applicant proposes to place underground development waste within the <br />existing pit remaining from the final cut of the Energy No. 1 surface <br />mine, immediately to the west of the portal development area. The <br />applicant observes that stability of these materials is not a concern, <br />because they will eventually be covered with backfilled spoil and will <br />exist below final grade. However, the applicant must demonstrate that <br />no hazard will exist in regard~to the adjoining portals and that the <br />water quality of the affected area will not be jeopardized. <br />e 2.05.6(3)(b): Protection of the Hvdroloaic Balance. Subsidence Rela <br />On pages 2.05-50 and 2.05-51 of the application, the applicant presents <br />a discussion of the subsidence-related aspects of protection of the <br />hydrologic balance. This presentation is inadequate as it exists, requiring <br />more detail and justification for some of the conclusions presented. The <br />applicant projects limits for overburden caving and fracturing above the <br />extracted coal seam which are significantly less than observations contained <br />within the current tedhnical literature. Further, the applicant concludes <br />that no adverse impacts of subsidence upon the hydrologic balance or water <br />rights are anticipated from the planned underground mining activities. <br />The applicant will have to further justify the assumptions concerning <br />extent of caving, fracturing and hydrologic impact. In addition, the <br />applicant should develop a means of verifying projected affects upon the <br />hydrologic balance. In specific, potential hydrologic effects upon the <br />"overburden aquifer" and the Twentymile Sandstone aquifer will have to be <br />monitored. <br />