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Gary Isaac <br />CAM-Colorado, LLC <br />August 29, 2008 <br />Page 20 <br />concurs that most of the proposed sediment pond embankments would not be a Class B <br />or C dam and failure will not cause serious property damage or loss of life. However, a <br />stability analysis is still required for all of these impoundment embankments. <br />Please provide a stability analysis that demonstrates compliance with 4.05.9(8) (b) for all <br />proposed new impoundments not meeting the size or other criteria of 30 CFR 77.216(a), <br />and located where failure would not be expected to cause loss of life or serious property <br />damage. In the case of two ponds the embankments appear to be completely incised, and <br />a stability analysis may not be applicable. <br />52. It appears that two of the proposed sediment ponds lie within "Area of Rapid or <br />Accelerated Erosion" or "Potentially Unstable Slopes" as defined on Map 05 Surficial <br />Geology & Geologic Hazards. Please update the PAP with a mitigation plan to ensure <br />the stability of these sediment pond structures that are located within areas of known <br />geologic hazards. <br />Rule 2.05.3(5) Topsoil and Subsoil Salvage <br />Plans associated with salvage and replacement of topsoil and coal waste pile cover soil are fairly <br />complex, but our understanding is as follows: <br />Narrative on page 2.05.3-36 of Volume 1 indicates that "all suitable topsoil horizons will be <br />salvaged together" and that "additionally, subsoil will be salvaged and placed in stockpile and <br />later used for cover material for the coal mine waste disposal area". The narrative references the <br />soils report in Exhibit 7 and notes that Table 1 of the report lists recommended topsoil and <br />subsoil depths that can be salvaged. Narrative and table on page 2.05.3-37 address the topsoil <br />thicknesses and volumes that can be salvaged from soil map units in the 129.4 acre Facilities <br />Area, to be placed in Topsoil Stockpile #2. Tables on page 2.05-38 address topsoil thicknesses <br />and volumes to be salvaged from the footprint of the 65.2 acre coal mine waste pile and stored in <br />Topsoil Stockpile No. 1, and subsoil thicknesses and volumes from the same area, to be stored in <br />the coverfill stockpile, for replacement on the flat top of the completed waste pile. A table on <br />page 2.05.3-39 shows that additional cover material would be salvaged from the 51 acre Map <br />Unit E, within the waste pile area foot print, and also stockpiled in the Coverfill Stockpile. <br />Narrative in Section 2.05.4(2)(c) explains that Topsoil Stockpile No. 1 would be used up to <br />replace a 3.7" layer of topsoil over the entire graded, cover soiled waste pile. A portion of <br />material from the Coverfill Stockpile (marginal quality subsoil salvaged from Map Unit E) <br />would be used to replace a layer approximately 22" thick directly over the graded coal waste on <br />the flat top of the pile, and another 22" thick layer of comparatively good quality subsoil <br />(originally salvaged from Map Unit A, and also stored in the Coverfill Stockpile), would be <br />spread over the first sub-layer, to provide a 48" thickness (including 3.7" of topsoil) over the coal <br />waste on the flat top of the pile. Cover material for the slopes and benches of the waste pile