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831 - 032.794 <br />April 2013 <br />Fall 2012 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />4.1 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 originally <br />included three historic standpipe piezometers (P -1 on the dam crest, P -2 on the dam crest, and <br />PZ -3a south of the spillway and west of the nested piezometers), four boring locations each with <br />three nested piezometers (PZ -06 -01 through PZ- 06 -12). two inclinometer locations (one on the <br />dam INC -4, and one in the landslide area south of the dam which was damaged and is no longer <br />there noted below, INC -5), and numerous survey mirrors for evaluation of surface movement on <br />and near the dam. <br />Many of these locations have been monitored monthly from July 2006, while others were added <br />to the monitoring network during 2007 and 2008. Beginning in spring 2010, monitoring and <br />reporting responsibilities for the piezometers and inclinometers on Monument Dam were turned <br />over to the Minnesota Canal and Reservoir Company per their agreement with MCC and the <br />Colorado Division of Water Resources. Nonetheless, Monument Dam piezometer and <br />inclinometer data through fall 2012 is included in this report as Appendix B. Note that INC -5 <br />(Inclinometer 5) was sheared off at 7 feet in May 2009 with no subsequent information collected. <br />This location also included PZ -08 -13 (a vibrating wire piezometer located in the same borehole). <br />Inclinometer 4 (INC -4) is the only other inclinometer associated with the dam at this time. MCC <br />retained monitoring and reporting responsibilities for the land survey stations. Information <br />collected from each of these monitoring locations is also provided in Appendix B. <br />The Minnesota Reservoir survey includes 12 monuments on the dam and 26 monuments on the <br />hillside (Borrow Area) south of Minnesota Creek Road. A summary of the survey data is <br />recorded in Table 1 of Appendix B. The table represents a comparison of the Easting, Northing <br />and Elevation displacement from spring 2012 through fall 2012. The differences in Easting, <br />Northing and Elevation displacement (if any) through this time period were calculated. <br />Monuments with a displacement greater than 0.5 feet were considered to have incurred <br />"significant' movement. <br />Wright Water Engineers, Inc. Page 29 <br />