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Spring 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• before longwall mining began and conformed to previously established criteria. In 2009, three <br />additional survey monuments were reset as noted in Appendix B. One original survey point <br />(S27) was apparently overlooked while another (S31) remains lost and not reset. <br />As required in 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 the E1 panel. That data will be used to quantify the amount of <br />subsidence (vertical displacement, tilt, and strain) that has occurred and the subsidence angle of <br />draw. Data obtained from the monitoring of this subsidence grid (Appendix B) will be used to <br />further calibrate the subsidence prediction model (Appendix A) so that a more refined analysis <br />can be made. Information contained in Appendix B is provided as an interim set of survey data <br />since mining under is not complete beneath the longitudinal line. <br />3.2 Monument Dam /Minnesota Reservoir Monitoring Data <br />• 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 graphically illustrated in Appendix C. <br />'In addition, the Minnesota Reservoir Robotic Total Station (RTS) surveys twelve monuments on <br />the dam (6000 series) and twenty -six monuments on the hillside south of Minnesota Creek Road <br />(7000 series). As a precaution, these monuments have been surveyed for movement every thirty <br />minutes since late 2008. A summary of this data is located as Table 1 in Appendix C. The table <br />represents a comparison of the average height and longitudinal displacement from December <br />• :2008 and June 2009 with differences noted. Those differences within one standard deviation of <br />831 - 032.791 <br />November 2009 <br />Wright Water Engineers, Inc. <br />Page 12 <br />