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Spring 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• December's data set for each monument are considered negligible and a difference of zero was <br />input into the table. Monuments with a displacement between December and June greater than <br />0.5 feet, and not within one standard deviation, were considered to have incurred "significant <br />movement" and were field verified. Those differences greater than one standard deviation but <br />less than 0.5 feet were considered "insignificant movement" of a "minor change ". <br />There was no significant movement measured on the dam from December 2008 to June 2009. <br />There were two survey monuments that indicated significant movement on the landslide area <br />south of the dam. These were survey points 7003 and 7021. A visual inspection verified that <br />some movement had taken place, but did not appear to be to the degree indicated in the <br />longitudinal measurements recorded. These monuments are located in a pre- existing, active slide <br />area and have likely experienced some additional settling after the initial slump occurred in 2008. <br />Since the remaining monuments showed no signs of movement, it can be assumed that this <br />displacement was an isolated activity likely contained within the landslide body. <br />• It should be noted that MCC's obligation to conduct aerial photographic surveys of the landslides <br />located north and south of Minnesota Reservoir using July 2004 photographs as a baseline <br />reference is required on an annual basis and will be reported in the fall 2009 subsidence report. <br />To date, photographic comparisons have shown there to be no observable difference in the <br />subject slide areas with the obvious exception of the earthwork conducted on the south side of <br />Monument Dam where considerable materials were removed to buttress the downstream portion <br />of the dam and readjust /rebalance the toe load of the landslide. <br />3.3 B -Seam Survey Information of Panel 25 <br />Also included in this report is a comparison of survey data from select locations in Sylvester <br />Gulch overlying B -seam longwall Panel 25. Survey data included in Appendix D is from seven <br />survey locations in December 2008 and May 2009 (i.e., during the late stages of mining and <br />approximately five months after mining was completed, respectively). An elevation comparison <br />!between these two data sets show that there was relative little movement with the greatest <br />• representing a drop of approximately 3 inches (0.325 feet). <br />831- 032.791 Wright Water Engineers, Inc. Page 13 <br />November 2009 <br />