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FFITASCA" <br /> Denver, Inc. <br /> Figure 3-4 provides a comparison of the NAG values with the "ABA NAG," meaning NNP values <br /> from ABA testing converted to units of kg H2SO4/t. As shown in Figure 3-4, the NAG values are <br /> lower than the ABA NAG values. The difference between ABA NAG and NAG is greatest at ABA <br /> NAG values greater than approximately 60 kg H2SO4/t. <br /> The samples with NAG pH values less than 4.5 each had an NNP value less than zero, indicating <br /> good agreement between the two testing methods. Samples AP7, B8, PP2, and PP4 were non- <br /> PAG based on their NAG pH and PAG based on their NNP. However, samples PP2 and PP4 had <br /> NNP values of -0.3 and -6.2 kg CaCO3/t, respectively, indicating that their potential for acid <br /> generation is uncertain. Each of these samples' acid-generating character is further evaluated <br /> based on the mineralogy and HCT results in the following sections of this report. <br /> 3.3 MINERALOGICAL TESTING <br /> X-ray diffraction analyses were performed on sample splits of each of the 29 Phase I samples to <br /> quantify the mineralogical compositions of the samples. <br /> 3.3.1 Methods <br /> The mineralogy of each of the Phase I WRCS samples was evaluated using XRD.The XRD analyses <br /> utilized quantitative phase analysis by Rietveld refinement to not only identify the minerals <br /> present but also quantify their relative abundances. The original laboratory report is provided in <br /> Appendix B. The XRD analyses have an effective detection limit on the order of approximately <br /> one weight percent (the specific detection limit can vary based on the matrix, the mineral in <br /> question, and details regarding the sample preparation); minerals present at concentrations less <br /> than approximately one weight percent may not be detectable by this method but could still have <br /> notable effects on water quality. <br /> 19 <br />