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William A. Bear <br />Page 2 of 7 <br />November 13, 2014 <br />currently approved permit application package, and that an additional 6,500 cubic <br />yards of cover material was generated during the quarter. <br />Compaction Testing <br />3. During this quarter, coal mine waste placement and compaction activities alternated <br />between Gob Pile #2 and Gob Pile #3. All compaction testing was performed by <br />Huddleston -Berry Engineering & Testing, LLC (HBET), at a frequency of <br />approximately once per week. <br />A total of 100 compaction tests were performed, including one re -test for a site that <br />initially failed to obtain the required 90% of Maximum Dry Density (MDD). Moisture <br />contents of the emplaced coal mine waste were noticeably lower than results <br />reported in previous quarters. This favorable condition was achieved even without <br />BRL's needing to incorporate as much coverfill material as they have in the past. <br />HBET's detailed report of materials testing for the 3rd quarter included a series of <br />Moisture - Density Relationship Curves that were developed in the laboratory and are <br />used to evaluate the relative compaction of coal mine waste. The eight curves are <br />summarized in Attachment 1 to this memo. <br />In Table 1 of Attachment 1, the curves are arranged by "Sample No. ". Gradation, <br />Atterberg Limits, and Description fields are filled in where this information was <br />provided with the curve(s) by HBET. At the far right, columns have been added to <br />show how many times each curve was used as a reference during the 2nd and 3rd <br />quarters of this year. In Table 2, the same curves have been re- arranged in order of <br />decreasing "MDD ". <br />As shown in Table 1, the curve being used with the greatest frequency is Sample No. <br />14 -0195. Aside from the source being identified as "Gob #3 Borrow Blend ", no other <br />properties are provided (Gradation, Atterberg Limits, or Classification). The Division <br />has reviewed the 2nd and 3rd quarter compaction results where this curve was used. <br />That data is compiled in Attachment 2, which shows the % Compaction achieved, <br />among other results. As highlighted in yellow, the compaction fell slightly below <br />90.0% with some regularity (although all tests would be at least 90 if rounding is <br />employed). <br />Referring back to Attachment 1, the second table shows there exists a large gap <br />between the MDD for Sample Nos. 14 -0195 (104.0 pcf) and 14 -0553 (93.5 pcf). As <br />noted in the Division's review of the 2nd Quarter 2014 CMW report, the average <br />MDD reported by Buckhorn Geotech from Jan -2012 to Mar -2014 was 100.0 pcf. We <br />believe that Curve 14 -0195 may present an unreasonably high MDD to which some <br />of the compacted material is being compared, and that this, rather than marginal <br />compactive effort, may be contributing results for % compaction that are borderline. <br />Please consider the development of an additional Moisture - Density curve(s) that <br />