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• VI22. MOFFAT STABILITY MONITORING WELLS <br />Six wells were installed in the Moffat area to monitor ground water levels. A <br />complete discussion of the purpose of the wells is provided in Section 4.6.9 of the <br />permit document. Elevations of the water in the Moffat wells are shown in Figure 36 <br />with the data provided in Appendix D. The 215 and 216 series wells have generally <br />been dry since 1990 while the 892 well series have been dry since their <br />installation. The stratigraphy into which these wells were completed is believed to <br />have been intersected during the construction of the Moffat sediment pond during the <br />fall of 1989. Consequently, these formations have been able to drain fairly freely. <br />Due to the draining nature of the formations, it is not anticipated that significant <br />potentiometric surfaces will develop in the future. <br />During 1998, all of these wells marginally responded to the wet spring <br />conditions. A review of the data appears to confirm the continued integrity of the <br />aquiclude between the Wadge seam and Lower Wadge unit and the lack of pore water <br />pressure development in the lower unit. <br />• IX. MOFFAT STABILITY MONODffii'P8 <br />A system of three control points and six monuments were established in <br />the final Moffat pit area during the fourth quarter of 1997. The purpose of the <br />monuments are to monitor the hillslope for long-term stability. The three control <br />points were placed to form a large triangle. The reference control point was <br />established along the top of the hillside in undisturbed ground above the final <br />Moffat pit. The two additional control points (back-sites) were established in <br />undisturbed ground northwest and south of the reference point. The back-sites were <br />established to verify the location of the reference point. The monuments were <br />installed in pairs with the first pair, SM-1 and SM-2, established in the lower <br />third of the final pit area. SM-1 was placed approximately 130 feet south of the <br />final pit highwall and SM-2 was placed approximately 340 feet south of the final pit <br />highwall. The second pair, SM-3 and SM-4, were installed approximately mid-way <br />along the pit. SM-3 was placed approximately 110 feet south of the highwall and SM- <br />4 was placed approximately 325 feet south of the highwall. The last pair, SM-5 and <br />SM-6 were installed in the upper third of final pit area. SM-5 was placed <br />• <br />49 <br />