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~. <br />Page 2 <br />Jim Herron <br />December 17, 1980 <br />the north of the area now in question. I have indicated that I believe <br />it would be in their best interest to take advantage of this opportunity <br />to make as thorough a set of subsidence observations as possible. The <br />monitoring system and frequency proposed will probably not allow the <br />collection of data with which to determine mechanics of the overburden <br />materials. Such a system would require additional monitoring points <br />surveyed on a daily or weekly basis for at least several months following <br />passage of the development face beneath the monitoring system. As I <br />have mentioned in previous memos, I also recommend that the operator's <br />professional staff document the ground response during the advance of <br />the development face, including such parameters as fracture frequency <br />and condition, rock fall and ceiling conditions and pillar and face <br />response. These should provide additional empirical data for future <br />subsidence analysis and prediction. <br />Other Topics <br />Roy Cox and Jerry Zimpfer should be able to assist you in determining <br />the adequacy of the applicant's proposal concerning ground water and <br />surface water topics. <br />/k <br />