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Memo to Candace Thompson <br /> Re: Coal Basin Mines - Subsidence <br /> page 5 <br /> potentially be affected by ground subsidence. This inspection <br /> shall encompass all areas bounded by projecting the boundaries of <br /> underground extraction upward from the mined seam to the ground <br /> surface along an angle of draw of 20.5 degrees from vertical . The <br /> company shall submit a report summarizing the results of the <br /> annual subsidence inspection, prior to December 31st of each year. <br /> (2 ) Prior to the commencement of double-pass longwall extraction or <br /> considera-tion by the Division of any future requests for amendment <br /> of the Coal Basin mine plan which involve expansion of the <br /> potentially subsided area, Mid-Continent Resources shall revise <br /> the subsidence report prepared by Dr. Bruce Collins and submitted <br /> in December of 1985. This report shall be revised to reflect the <br /> subsidence data obtained during the 1988 subsidence resurvey and <br /> any subsequent resurveys and shall be submitted to the Division <br /> for review. <br /> (3) In the event that double-pass longwall extraction is initiated at <br /> Coal Basin Mines, the Division will require Mid-Continent <br /> Resources to resume an appropriate monument surveying subsidence <br /> monitoring program, in order to determine the subsidence factor <br /> and angle of draw above the relatively untested double-pass <br /> extraction technique. <br /> cc: Jim Stevens <br /> r# <br />