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ENERGY FUELS COAL, INC. SOUTHFIELD MINE SEMI-ANNUAL SUBSIDENCE MONITORING REPORT (MAY, 1967 THROUGH OCTOBER, 1987) Introduction This report has been prepared to summarize subsidence monitoring survey data for the period of May, 1987 through October, 1987, and to discuss subsidence predictions based upon the present monitoring program. quarterly survey monitoring data is summa- rized on three enclosed tables, and is also depicted in cross- sectional form for the high-resolution monument grid. South Subsidence Grid All data collected at the high-resolution monument grid (South Grid) for the period of record are presented on Table 1, Subsi- dence Monitoring Data Summary. Total subsidence, to the date of the most recent survey, is depicted in cross-sectional form on Figure 1 and Figure 2. No mining operations have occurred in the grid area that could impact the subsidence. The data presented on Table 1 indicates that only minor subsi- dence, ranging from 9.01 to 0.04 feet, has occurred during this monitoring period. This minor rate of subsidence is comparable to the previous semi-annual monitoring period. It is anticipated that only minor additional subsidence will continue at the South Grid Monuments. The highest values of total subsidence continue to be measured along the West and North legs of the South Grid. The maximum subsidence to date, 1.99 feet, is measured at Monument 15. Sub- sidence at this station is potentially influenced by three re- treat mining panels, completed in March, 1986. The calculated worst cast subsidence for this scenario is approximately 5.0 feet, however, the South Grid monument was not designed to detect the maximum subsidence due to the impact of three adjacent re- treat panels. Examination of the data portrayed in cross-sectional form on Figure 1 indicates an apparent angle of draw between 20 and 29 degrees, similar to that shown in the previous semi-annual re- ports. The angle of draw is generally consistent with the range of 20 to 25 degrees predicted in the permit application. City of Florence Watec Line Monuments All data for the period of record pertaining to the Water Line Monuments are shown on Table 2, Subsidence Monitoring Data Sum- mary. No mining operations were conducted under the Water Line Monuments during this semi-annual period.