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Memo to Candace Thompson <br /> Coal Basin Mines <br /> Subsidence Monitoring Suspension <br /> page 2 <br /> I recommend that we approve the suspension of subsidence monitoring above the <br /> single-pass longwall and room & pillar activities at the Coal Basin Mines with <br /> the following conditions. <br /> (1 ) If any unanticipated surface disturbance (Cracking, cratering or <br /> landsliding) manifests itself within the area potentially affected <br /> by subsidence (angle of draw = 20.5 degrees) , the operator will be <br /> required to immediately reinstitute the subsidence monitoring <br /> program. <br /> (2) All existing monuments must be left in place and maintained. <br /> (3) All existing monuments must be resurveyed at the conclusion of the <br /> current five year permit period, to determine whether additional <br /> subsidence manifests itself. <br /> (4) A subsidence monitoring program will be required above any <br /> double-pass longwall operations, in order to determine the <br /> ultimate subsidence factor above that relatively untested <br /> extraction technique. <br /> cc: Mike Long <br />