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To: Chris Nyikos <br />From: Philip B. Solseng <br />Subject: Stability Analysis Results <br />Date: 16 September 2009 <br />Project: Pond MBSE Evaluation <br />c: Jed Greenwood, Brad Lindsay <br />4. The foundation for the embankments are sub-cut to about elevation 6040 and backfilled with <br />locally available colluvium with the following criteria: <br />a. Foundation is natural ground <br />b. Fill is local material, primarily colluvium which is a clayey/cohesive material <br />c. Fill is placed in horizontal layers less than 12 inches thick and compacted to 95% of <br />standard Proctor dry density <br />d. Freeboard is a minimum 1 foot <br />e. The slope angle of the embankments on either slope are no steeper than 2H:1 V <br />5. Based upon the design drawings by Roberts & Schaefer for Pond MBSE and a field <br />investigation, the existing material at the pond location is a combination of coal waste and <br />building debris, down to about elevation 6040 to 6042. This material will be removed and the <br />bottom of the excavation for the foundations will be about elevation 6040. The excavation <br />will be sloped at about 1H:1 V. The laboratory testing from the field investigation is <br />summarized in Table 1 (see logs attached). <br />6. While much of the material at the proposed pond location is coal waste mixed with other <br />mining-related fill, a significant amount of this material is lean clay with varying amounts of <br />sand, gravel and cobbles. This material is typical of the colluvial soils found in the vicinity of <br />West Elk Mine. It is assumed that when the fill that is unsatisfactory for embankment <br />foundations is removed, it will be replaced with this colluvial type material. Furthermore, the <br />embankment and the clay liner (blanket) is assumed to be comprised of the same material, <br />though the material specification for the embankment material might be less stringent than the <br />clay liner. <br />Table 1. Results from Field Investigation and Laboratory Testing <br /> <br />Test <br />Depth Moisture <br />Content Grain <br />Size, Atterberg <br />Limits <br />Pit in. Litholo % P200 % PL LL <br />TP#1 0-16 Clayey silt with ravel and cobbles 10.8 -- 25 37 <br />TP#1 16-72 Coal waste 7.0 37.0 -- -- <br />TP#26 36-72 Gravel with sand 3.1 3.3 -- -- <br />TP#6 0-28 Clayey silt with sand and ravel -- -- 19 29 <br />TP#6 48-64 Clay with silt 22.9 64.0 9 29