2013-12-03_INSPECTION - M1986015

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PERMIT #: M- 1986 -015 INSPECTOR'S INITIALS: TC1 INSPECTION DATE: November 15, 2013 features to try to determine the subsurface size and geometry to develop alternative mitigation techniques. TMOP committed to complete the backfill in the northwest corner of the northeast Phase 2 area. Regarding the Phase 2 overburden/topsoil stockpile west of the Cooper property, TMOP indicated they will begin removing the material in the January - February 2014 time frame and have the material removed by May 30, 2014. TMOP stated they would have the stormwater ditch intended to drain the south end of the Winters property that floods completed by April 1, 2014. Current Stipulations: There are currently no stipulations. Records: • The latest formal inspection was conducted 4/12/2007. No problems were cited. This inspector also performed an informal pre - operational inspection related to Amendment 4, phase 7 eastern expansion on 10/28/2011. No problems were cited. • The permit anniversary date is November 12. Annual fees and reports are current through 2013. • The permitted area is 466.16 acres with a maximum allowed disturbed area of 268 acres. • The DRMS has copies of the "As- Constructed" drawings for the slurry wall. These drawings are dated 3/12/2009. • The approved reclamation permit states the operator will continue to monitor groundwater levels in wells within 600 feet of the permit boundary. No groundwater monitoring data has been filed with the DRMS. This is cited as a problem on page 1 of this report. Bond: The current financial warranty is a $2,288,004 corporate surety. The bond was reviewed as part of Amendment 4, approved in December 2011 and determined to be adequate. Review: Based on review of the CGS collapsible soils report and conversations with current and former CGS personnel, the DRMS believes the soils in the area are susceptible to dispersion and piping that could result in the observed collapsed soils in the vicinity of 25th Lane. Figures 2 through 5 (Attachment A) indicate water levels in nearby wells reaching a low in 2009. The 25th Lane wells (Figure 5) and MW -105 appear to have rebounded in 2011 and remained relatively stable, with the exception of a 10 -foot elevation increase measured in MW -105 in May of 2011 (Figure 4). This is about the same time (summer of 2011) that Ms. Winters confirmed cracks began occurring on the Cooper property. This correlation may or may not be significant, and the DRMS has no information indicating this sudden increase was or was not related to mine activity. Anecdotal evidence stated by the complainants of ponded water in the northeast portion of Phase 2 in 2011 may have created a condition that contributed to potential piping of fine grained soils at that time. Figure 3 indicates there is a difference in the subsoils between the Cooper well and the Winters well. The Winters well bore log indicates a 15 -foot thick yellow clay layer that does not appear to be present in the Cooper well bore log. This may explain the difference in the observed cracks and holes on the Cooper and Winters properties. While the available data suggests a possible cause and effect relationship between the mine's activities Page 4 of 13