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2.7.2.3 PR -7 Mine Expansion Area Overburden Geochemistry <br />The sampling and analysis requirements for the PR -7 Mine Expansion Area were discussed with the <br />Colorado Division of Reclamation, Mining and Safety (CDRMS) in a meeting held in their office on April <br />14, 2014. Trapper Mining Inc. (TMI) provided an overview of the significant amount of historical <br />overburden geochemical data that has been collected at the Trapper Mine and documented in Section <br />2.7.2, Appendix I and the Annual Reclamation Reports. Between 1972 and 1986, as reported in Section <br />2.7.2 and Appendix I - Overburden Characteristics, 27 overburden core holes were sampled and <br />analyzed for approximately 8,333 geochemical and physical overburden parameters. In addition, <br />between 1985 and 1987 269 samples of regraded spoil material were collected and analyzed for <br />approximately 7,224 physical and geochemical parameters to test suitability as a plant growth medium <br />for reclamation and groundwater quality. <br />Considering the vast amount of baseline overburden and reclamation spoil geochemistry data that <br />have been collected at the Trapper Mine over the past 42 years, Trapper Mining Inc. proposed, and the <br />CDRMS agreed, that one drill hole, drilled through the area of maximum overburden thickness, would <br />be sufficient to characterize the geochemical properties of the overburden in the PR -7 Mine Expansion <br />Area and satisfy Rule 2.04.6(2)(b)(i). Drill hole 14_6_90_33_9 was drilled in 2014 to characterize the <br />overburden of the PR -7 Mine Expansion Area. Because a small portion of the core for 14_6_90_33_9 <br />was not recovered, Trapper drilled a twin hole immediately adjacent to the first hole to recover the <br />interval of core which was lost in the first hole. The location of the boring to characterize overburden <br />geochemistry for the PR -7 area is shown on revised Map 36. <br />Samoline and Analvsis Methods <br />The sampling interval requirements and laboratory analytical methods used in this overburden <br />evaluation were discussed between TMI, ACZ Laboratories, Inc. of Steamboat Springs, Colorado, and <br />the CDRMS and ultimately approved by the CDRMS. The suggested analytical methods listed in Table 5 <br />of the Guidelines for the Collection of Baseline Water Quality and Overburden Geochemistry Data, <br />Colorado Mined Land Reclamation Division 1982 (hereinafter referred to as the 1982 Guidelines) were <br />primarily used to analyze the overburden samples for geochemical and physical parameters. A <br />summary of the laboratory analyses performed and analytical methods used is provided in Table 2.7- <br />8a, Overburden Laboratory Analyses and Methods for the PR -7 Mine Expansion Area. A lithological <br />description of each stratum, including the 10 coal seams sampled and the 76 sample intervals analyzed, <br />is provided in Table 2.7-8b, Overburden Geochemical Drill Hole Lithology and Sample Intervals for the <br />PR -7 Mine Expansion Area. The laboratory analytical results are provided in Table 2.7-8c, Overburden <br />Geochemical and Physical Laboratory Analytical Results for the PR -7 Mine Expansion Area. Figure 2.7- <br />4a graphically depicts the overburden soil textures. Figure 2.7-4b shows box and whisker plots of water <br />soluble and extractable metals in the PR -7 Mine Expansion Area overburden. <br />Evaluation Criteria <br />As agreed during the pre -consultation meeting with the CDRMS, the overburden was evaluated for its <br />potential suitability as either a plant growth medium or regraded spoil aquifer. Accepted suitability <br />criteria are provided on Table 2.7.2a, List of Spoil Parameters to be Analyzed at Trapper Mine or in <br />2-391 a %� <br />revision. 1fi <br />O � <br />Approved: Nk.\ <br />