Laserfiche WebLink
Fall 2011 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />period were calculated. Monuments with a displacement greater than 0.5 feet were considered to <br />have incurred "significant" movement. <br />As reported in the Spring 2011 Report, from January to June 2011, there was no significant <br />movement measured on the dam. For the July to December 2011 time period, all of the changes <br />in the Easting direction (+ 0.05 -0.77 inches), Northing direction (± 0 -0.55 inches) and in <br />elevation (± 0.01 -0.09 inches) for all monuments on the dam and Borrow Area were insignificant <br />(approximately <0.5 feet). Based on visual observations, little to no change has been observed <br />on Monument Dam and Borrow Area (see Monument Dam Inspection Reports included in <br />Appendix B). <br />4.2 Monument Dam /Minnesota Reservoir Aerial Photograph Comparison <br />Each year, MCC performs an aerial photographic survey of the landslides located north and south <br />of Minnesota Reservoir. Annual comparisons are performed using July 2004 photographs as a <br />baseline reference. Appendix C of this report includes the July 2004 baseline photograph (Map <br />C -1), as well as a photograph of the same area taken in September 2008 (Map C -2), June 2009 <br />(Map C -3), May 2010 (Map C -4), and June 2011 (Map C -5). The June 2011 (Map C -5) clearly <br />shows the area where a french drain was installed in early fall 2009 to remove water from the <br />upper end of the existing slide complex. A comparison of the photographs show there to be <br />relatively little change between June 2009 and June 2011, except in the area south of the south <br />abutment of Monument Dam. <br />As of the time of the 2011 aerial photograph (June), mining of E -seam Panel El was complete <br />and E -seam Panel E2 was nearing completion with mining progressing from southeast to <br />northwest. <br />4.3 U.S. Forest Service Water Resources Survey <br />MCC is required, as part of their permit, to monitor USFS water resources (i.e., reservoirs and <br />stock ponds). Appendix D of this report is the 2011 Water Resources Project Survey Report <br />generated for this purpose. <br />831 - 032.793 <br />May 2012 <br />Wright Water Engineers, Inc. Page 27 <br />