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Subsidence Field Observations West Elk Mine August 28 and 29, 2001 • The topography indicates the presence of unstable slopes on either side of the reservoir and the dam. • Movement has locally occurred in the toe area of the slide over the last four years, and also over many decades and perhaps centuries (see video and page 9 of October 7, 1999 report to MCC). 1 • No recent landslide features (cracks, steps or bulges) were observed on this foot traverse, except as recorded at Location 1 1. • There has been no mining within the area limits defined by the most conservative angle of the draw of the reservoir. The southern boundary of longwall panel 13-A is 1,000 feet or more north of the northern shoreline of the reservoir. • The minimum draw angle (or limit angle, tom a vertical reference), which defines the limit of subsidence at the surface in relation to a given mining panel depth, is calculated to be 55 degrees (Draw Angle =Arc Tangent of 1,000/700 = 55 degrees). • The draw angles measured in the Somerset mining area range from 8 to 21 degrees. The most conservative draw angle used in the West Elk Mining area that has been used during the permitting stage is 25 degrees (see pages K-16-17 of the Final Environmental Impact Statement or the Iron Point and Elk Creek Coal Lease Tracts dated February 2000). 1 3.2.11 Location 11 Location l 1 is at Location 12 of the 1999 subsidence evaluation report. It is located on the toe of a landslide that was re-activated in the last four years. • The cracks that were as much as 1'h feet wide and fresh looking in 1999 are now filled and are only locally discernible (compare 1999 and 2001 videos). • Steps, representing differential vertical displacement during downhill movement, are still locally discernable, but subdued. 1 831-032.560 Wright Water Engineers, Inc. Page 14 September 2001