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-58- <br /> XXI. Sealinq Grilled Holes and Underground Openings - Rules <br /> Z.05.ut�) l9) and 4.07 <br /> Hid-Continent Resources, Inc. proposes Co seal mine portal openings in <br /> accordance with 1`1SHA regulations (3(1 CFR 75. 1711 -1 ) and to seal all bore <br /> holes and wells .lith concrete plugs or welded locked steel caps, in the <br /> case of monitoring facilities. The Division finds that these proposed <br /> techniques are in compliance with the requirements of Rules 2.05.4(2) (g) <br /> and 4.07. <br /> XXII. Subsidence - Rules 2.05.6(6) and 4.20 <br /> t� The applicant determined that "the only structures above underground <br /> workings, or within areas of possible surfac <br /> e c,. subsidence, are those <br /> b4 /related to the mining operations such as exploration and light use roads <br /> and ventilation fans" (page IV-E-23) . Potentially affected renewable <br /> resource lands include only limited grazing lands, since the rnaior local <br /> .� uife lie beneath the coal seams being mined. In addition <br /> �W Mid-Continent Resources, Inc. presents a thorough discussion or worst <br /> possible consequences due to subsidence, including predictions of <br /> projected subsidence magnitude. The company predicts a maximum vertical <br /> subsidence of 13.2 feet in areas overlying the extraction of 24 feet of <br /> coal (9 feet to be extracted from one seam and 16 feet to be extracted <br /> from the other) . Based upon limited observed data within the western <br /> United States, the applicant also projects an angle of draw of 150. <br /> The Division, as discussed within its Preliminary Adequacy Review letter, <br /> does not consider this angle of draw average projection to be adequately <br /> justified. Observations of angle of draw at the nearby Somerset feline <br /> suggests that an angle of draw of 20.50 would be more appropriate, in <br /> the opinion of the Division. <br /> Finally, the company has installed an extensive system of subsidence <br /> monitoring monuments with which it proposes to verify its projections of <br /> subsidence occurrence. The program is designed to provide the following <br /> data: <br /> - ,Maximum subsidence resulting from mining <br /> - Horizontal movement of the ground surface resulting from mining <br /> - Subsidence development profiles <br /> - Subsidence profiles resulting from mining <br /> - Strain profiles resulting from mining <br /> - Deter-nination of the angle of draw <br /> - The effects of depth and mining geometry on subsidence. <br /> The Division concurs with this opinion and 4itn the company' s observation <br /> that: "The proposed monitoring p-rogram ,4ill result in the development of <br /> site-specific subsidence projection models for the Coal 3asin area" (page <br /> IV -3a) <br /> The applicant requested permission to monitor the subsidence �;ionument <br /> net:rorK three times each summer. Quart-e-1,/ ionitoring, as required <br /> nCrndl ',y oy 'uie is Gal �as'n by rugged <br /> i <br /> J <br />