2010-05-03_REPORT - C1980007 (9)

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Fall 2009 Subsidence and Geologic Field Observations Box Canyon, Apache Rocks, and South of Divide Mining Areas • discussed in Section 3.1 of this subsidence monitoring report with specific survey data summarized in Appendix B and shown on Map B-1. MCC has been collecting data from numerous monitoring locations in and around Minnesota Reservoir and Monument Dam for the last several years. A general discussion of the data collected to date is provided in Section 3.2 with the specific data provided in Appendix C and D. 3.1 E1 Panel Subsidence Monitoring Grid The West Elk Mine has historically extracted coal mainly from the B-seam of the Mesaverde Formation. In 2009, extraction of coal from the E-seam (i.e., a unit approximately 300 feet above the B-seam) began in the SOD mining area. As part of the ongoing data collection and monitoring programs required under its permit, an E-seam subsidence monitoring grid was proposed, developed and constructed. This grid is located above Longwall Panel E1 and is comprised of 120 points in one longitudinal and two transverse monument lines relative to the panel orientation (see Map 2 and also Map B-1 of Appendix B). The two transverse lines extend • beyond the gate road of Longwall Panel E1 both to the north and south. The southern end of these traverses extends to approximately the middle of Longwall Panel E2 (at least 700 feet outside the edge of the panel). Appendix B of this report includes a tabular summary of the E-seam survey descriptor, northing coordinate, easting coordinate, and elevation at each of the 120 observation points and compares the various survey data. This tabular comparison includes a column which represents the relative elevation difference between the November 2009 survey and the most recent pre-mining survey data. Please note that 2008 construction activities along the access roads over Longwall Panel E1 resulted in the destruction of twelve survey monuments. All but two of these monuments have been subsequently reset and resurveyed as represented in Appendix B. As expected, the baseline elevations for these reset monuments have changed. Both of the baseline surveys (i.e., 2007 and 2008) were conducted before longwall mining began and conformed to previously established criteria. In 2009, three additional survey monuments were reset as noted in Appendix B. One 831-032.791 Wright Water Engineers, Inc. Page 11 April 2010