2014-02-26_REVISION - C1996083 (2)

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Page 9of10 • Feb -2007 Section 6.0 "It is critical that gob materials are not placed wet of the optimum moisture content." • Mar -2007 Section 6.0 "Gob must be placed at, or slightly below its optimum moisture content. Gob placed significantly above the optimum moisture content likely will not achieve adequate compaction or undrained shear strength. Placement techniques that allow for drying gob may be required at times," and "On -going moisture /density testing and strength testing of gob are recommended... We also recommend implementation of a moisture content specification allowing moisture contents no greater than 4% above the optimum moisture content as determined by the standard Proctor." • Sep -2008 Section 6.0 and May -2009 Section 6.0 "Proper management of coal waste moisture content during placement will reduce the pore pressures within the fill and enhance stability. As practical, waste materials in excess of the optimum moisture content should be allowed to dry prior to placement. Blending wet material with drier material may also prove to be an effective moisture content management strategy." Quarterly reports indicate that the moisture content of the coal mine waste is consistently well above OMC. In 2012, the moisture content of the coal mine waste was an average of 3.5% above optimum; two of every five tests showed that the moisture content was exceeded by more than 4 %. Significant improvements were made in 2013, with the average moisture content being reduced to only 2.2 percent above optimum. However, moisture contents continued to exceed optimum by more than 4% one out of every five tests. MATERIAL PROPERTIES Native soils were sampled and tested in 2006 for TR -44 (Gob Pile #4) and TR -45 (Gob Pile #3). This level of testing is likely sufficient for the future. Coal Mine Waste was sampled from Gob Pile #2 for TR -42 (in 2005) and TR -44 (in 2006). Other than the ongoing compaction testing, no new tests, specifically triaxial compression tests, have been performed on the coal mine waste. Native Soil Gob Pile #2 • (TR -42) used Lambert (2003) results Gob Pile #4 • (TR -44) Gradation & Atterberg Limits (5 sets) from 2 foundation holes bored in 2006; • (TR -64) Revised Effective Strength Parameters to 4' =34.0 deg, c' =100 psf Gob Pile #3 • (TR -45) Gradation & Atterberg Limits (8 sets) from 7 foundation holes drilled in Dec -2006 • (TR -45) Unconsolidated- Undrained (UU) Shear Strength (3 sets) based on various confining pressures