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"E" Seam Technical Revision Adequacy Comments <br />• Geotechnical-Subsidence <br />The applicant proposes an overall extraction ratio of approximately 43% within <br />the E Seam workings. Pillars will exceed 30 feet by 50 feet under a maximum <br />of 275 feet of overburden. The subsidence projections contained within the <br />original approved permit project permanent stability for pillars as small as <br />29 feet by 29 feet under 275 feet of overburden. Empire energy proposes to <br />prevent subsidence by "leaving of adequate pillars to prevent massive pillar <br />failures and to provide long term stability of the mined area". Monitoring of <br />subsidence conducted at the Eagle No. 5 Mine has proven the projections <br />contained within the original approved permit. Therefore, the proposed <br />protection scheme is acceptable, and and it is prudent to assume that no <br />material damage will occur to structures or renewable resource lands. <br />Empire Energy states, within the technical revision application cover letter; <br />"Empire Energy Corporation recognizes that the approval of this <br />technical revision in no way obligates the Colorado Mined Land <br />Reclamation Division (CMLRD) to approve any future production activity <br />in the E Seam. Any production activity planned in the E Seam will be <br />submitted to the CMLRD (and OSM if applicable) as a new permit <br />application or permit revision to the presently approved permit <br />document. Production activities within the E Seam will not be <br />• conducted prior to the approval of such activities." <br />Production activity will undoubtedly anticipate higher recovery ratios, with <br />the extraction of pillars and subsidence manifestation. Any application for <br />approval of subsidence within the E Seam workings will have to address <br />subsidence impacts as required by Rule 2.05.6(6). I am seriously concerned <br />that subsidence of the E Seam workings, superimposed upon subsidence of the F <br />Seam workings, may cause material damage to the Twentymile Sandstone Aquifer <br />which is appropriated for domestic, agricultural and commercial uses within <br />the potentially impacted area. Hydrologic monitoring has discerned that <br />previous mining within the F Seam has significantly impacted the piezometric <br />surface within the Middle Sandstone Aquifer, which is unappropriated within <br />the impacted area. However, mitigation of material damage within the locally <br />artesian Twentymile Sandstone will probably be extremely difficult and <br />costly. Approval of any mine plan which includes potential impacts upon that <br />aquifer will require an acceptable analysis, mitigation and replacement <br />plans. It is conceivable that the applicant may not be able to acceptably <br />mitigate projected impacts to the Twentymile Sandstone Aquifer, which could <br />preclude approval of their revision request for production activity within the <br />E Seam. <br />Hydrology <br />1. Cover letter, paragraph 5, <br />development work only then <br />• 6-10 year mine plans. The <br />and examined individually, <br />a separate narrative. <br />sentence 3: If the inflow estimates are for <br />why are these referenced to the 1-5 year and <br />development phase should be separated out <br />then compared to the later mining phases in <br />