2016-04-19_REPORT - C1980007 (6)

Home Browse Search

Fall 2015 Subsidence and Geologic Field Observations South of Divide and Dry Fork Mininq Areas network during 2007 and 2008. Beginning in spring 2010, the Minnesota Canal and Reservoir Company took over the monitoring and reporting responsibilities for the piezometers and inclinometers on Monument Dam per their agreement with MCC and the Colorado State Engineer's Office (SEO). MCC retained monitoring and reporting responsibilities for the land survey stations. Data collected from various monitoring locations on the Monument Dam (including Dam Inspection Forms) are provided in Appendix B. As discussed in previous reports, the Minnesota Reservoir Robotic Total Station (RTS) became completely inoperable in 2011 and could not be repaired after numerous attempts. In lieu of the RTS, quarterly land surveys of the monuments (increased to monthly when mining is within one mile of the dam) are completed. A summary of both average height and longitudinal displacement data obtained from spring 2015 to fall 2015 is provided in Table 1 of Appendix B. 4.2 Monument Dam/Minnesota Reservoir Aerial Photograph Comparison Each year, MCC performs an aerial photographic survey of the landslides located north and south of Minnesota Reservoir. Annual comparisons are performed using July 2004 photographs as a baseline reference. Appendix C of this report includes the July 2004 baseline photograph (Map C-1), as well as a photograph of the same area taken June 2014 (C-8) and in June 2015 (Map C- 9). For brevity, Maps C-2 (September 2008), C-3 (June 2009), C-4 (May 2010), C-5 (May 2011), C-6 (June 2012), and C-7 (May 2013) are not included herein but can be found in the previous fall reports. Maps C-1, C-8 and C-9 are provided in this report for comparative purposes. A comparison of the most recent image with one flown in June 2014 finds no discernable change. A comparison to the image from the July 2004 flight reveals a continued scar from where a french drain was installed south of the Monument Dam south abutment in early fall 2009 to remove water from the upper end of the existing slide complex. At the time of the 2015 aerial photograph (June), E -seam longwall mining was complete on Panels E1, E2, E3, and E4 and more than 80 percent complete on Panel E5 with mining progressing from southeast to northwest. 831-032.797 Wright Water Engineers, Inc. Page 24 March 2016