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ENERGY FUELS COAL, INC. SOUTHFIELD MINE SEMI-ANNUAL SUBSIDENCE MONITORING REPORT NOVEMBER, 1990 THROUGH APRIL, 1991 INTRODUCTION This report presents summarized subsidence monitoring data for the above period of record and a discussion of the data as compared to predictions made in tl~e approved permit application. Enclosed are three summary data tables of survey data at all monitored structures and monuments, and two cross section diagrams of the high resolution grid. Results of the field survey data are discussed below in more detail. STRUCTURE SURVEYS: RANCH STRUCTURES, CREEK POINT, AND FLORENCE WATER LINE. Subsidence survey data for the above monitored structures are shown on Table 2: Florence Water Line and Table 3: Ranch Structures and Creek Point. The data summaries indicate that no measurable subsidence is taking place at [he monitored structures with the exception of waterline monument 'E', located on the west end of the waterline. This location is the only monitored point that has been affected by retreat mining. The measured subsidence at Monumnet 'E' of 1.50 feet is well within the maximum predicted value of 2.79 feet. Since this location was undermined five years ago, further consolidation of overburden materials should cause minor additional subsidence. The remaining monitored structures are not expected to show subsidence effects until retreat mining proceeds below each of them. HIGH-RESOLUTION GRID Survey data for the grid monuments is summarized on Table 1 and presented in cross section form on Figures 1 and 2. The data indicate total subsidence values of 0.04 to 2.34 feet displacement within the area of the grid monuments. Tl~e maximum displacement continues to be less than the 5.40 feet worst case displacement predicted in the permit. Continued consolidation of the strata above the mined out area monitored by [he grid is expected to exhibit on minor additional subsidence.