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,: _,. <br />Peter O'Connor - 2 - June 26, 1986 <br />4. At lease one reference point must be established off of any areas <br />potentially affected by subsidence. It is recommended that this <br />monument be established at least 130 feet south of the face of the <br />south barrier pillar, and 150 feet west of the western most extent of <br />the old mine workings. <br />5. Monitoring of the subsidence monument network must take place at least <br />once prior to any underground development work, in order to establish <br />baseline data. <br />6. Blue Flame has committed to monitoring the subsidence monument network <br />quarterly during the first year of activity at the site. Blue Flame <br />must commit to semi-annual monitoring following the first year. In <br />addition, quarterly monitoring will be required when Blue Flame begins <br />to rob pillars in the mine. <br />7. For purposes of reporting subsidence monitoring data, the following <br />information will be required on an annual basis: <br />a. Survey data, which has been tabulated and reduced, shall be <br />submitted. <br />b. Five (5) subsidence profiles shall be submitted. These <br />profiles, which will be adequately detailed and be certified by <br />a registered professional engineer, should extend between <br />points 1 and 2; 1 and 3; 2 and 3; 2 and 4; 3 and 4. Each point <br />is numbered as per comment (3) above. <br />SR/ddt <br />cc: Michael S. Savage <br />Jim Pendleton <br />1747E <br />