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Fall 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• original survey point (S27) was apparently overlooked while another (S31) remains lost and was <br />not reset. <br />According to the permit, the subsidence grid is to be resurveyed at least three months, but no <br />more than nine months, after the longwall face has moved past the western end of the <br />longitudinal survey line of Longwall Panel E1. Mining beneath the subsidence grid was <br />completed in late August 2009. In November 2009, the requisite post-mining subsidence survey <br />was completed. However, analysis of that data is not expected to be completed until sometime <br />later in 2010. When analyzed, that data will be used to quantify the amount of subsidence <br />(vertical displacement, tilt, and strain) that has occurred and the subsidence angle of draw. Data <br />obtained from the monitoring of this subsidence grid (Appendix B) will be used to further <br />calibrate the subsidence prediction model (Appendix A) so that a more refined analysis can be <br />made. <br />3.2 Monument Dam/Minnesota Reservoir Monitoring Data <br />MV Beginning in 2006, numerous monitoring stations were established on Monument Dam and at <br />strategic locations around Minnesota Reservoir as a means to collect baseline information about <br />water levels and potential surface/subsurface movement. Monitoring locations include three <br />historic standpipe piezometers, four boring locations each with three nested piezometers, two <br />inclinometer locations (one on the dam and one in the landslide area south of the dam), and <br />numerous survey mirrors for evaluation of surface movement on and near the dam. Many of <br />these locations have been monitored monthly from July 2006, while others were added to the <br />monitoring network during 2007 and 2008. Information collected from each of these monitoring <br />locations is recorded in Appendix C. <br />The Minnesota Reservoir Robotic Total Station (RTS) surveys twelve monuments on the dam <br />(6000 series) and twenty-six monuments on the hillside south of Minnesota Creek Road (7000 <br />series). As a precaution, these monuments have been surveyed at least once per day since late <br />2008. A summary of this data is recorded in Table 1 of Appendix C. The table represents a <br />comparison of the average height and longitudinal displacement from December 2008 to October <br />831-032.791 Wright Water Engineers, Inc. Page 12 <br />April 2010