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f <br />SUBSIDENCE MONITORING REPORT <br />The information presented in this report is based on survey data obtained <br />in June, 1984. A trigonometric survey method was used to compile the raw data. <br />A systematic error of plus or minus 0.15 feet can be anticipated, for survey <br />points on rows A through E. <br />Surface subsidence (maximum three (3) feet) has occurred on Row C since <br />the last semi-annual report. The maximum subsidence for each row is as follows: <br />Row Subsidence (ttaximum) Predicted Subsidence <br />A 3.0 ft. 2.2 ft. <br />B 4.8 3.6 <br />C 3.2 4.D <br />D 4.4 4.0 <br />The maximum subsidence measured is slightly greater than the predicted sub- <br />sidence using the Abel and Lee equations. <br />The cross-sections for the above rows are presented on drawing EEC-83016-C. <br />The elevation differentials determined for rows E and F can be attributed to the <br />systematic error involved when making a trigonometric survey. <br />The angle of draw for each row was determined to be: <br />Row Angle of Draw (from the vertical <br />A 16.5 <br />B 4.8 <br />C 18.5 <br />D 24.1 <br /> Avg. 16.0 <br />As can be seen, the average angle of draw is significan~:ly below the predic- <br />ted angle stated in the Operation and P.eclamation Plan. <br />Minimal change in subsidence was detected for Rows A, B, and D, since the <br />last semi-annual report. The change surveyed is the result of residual subsi- <br />dence and/or systematic surveying error. <br />