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Section 13 <br />Geochemical Data and Analysis <br />13.2 Mine Rock Geochemistry <br />13.2.1 Assessment of Potential Acid - Forming Rock <br />The section presents an assessment of the Sunday Mines Group development rock <br />and ore regarding its potential to be acid- forming. Evaluation of the potential for acid <br />mine drainage is based on evaluation of ABA data, observational data regarding <br />mineralogy of the mine rock, and effluent pH data from MWMP column tests. ABA <br />data for development rock and stockpiled ore show an overall low sulfur content and <br />excess of neutralization potential over acid potential in all samples. ABA data are <br />compared to the empirical thresholds to evaluate the potential for the rock to generate <br />acid in the future. The first threshold is based on the NNP. The NNP of development <br />rock and ore samples collected at the Sunday Mines Group range from 32.5 to 270.7 <br />t /kt CaCO3 eq. with a median value of 56.7 t /kt CaCO3 eq. These NNP values are <br />greater than the 20 t /kt CaCO3 eq. threshold, which indicates that the development <br />rock and ore has a low potential to generate acid. ABA data are compared to the <br />second empirical threshold in Figures 13 -1 and 13 -2. This threshold is based on the <br />NP:AP ratio. All samples exceed the NP:AP ratio threshold of 4, which indicates that <br />the samples are unlikely to generate acid. <br />The ABA data support field observations that visible sulfide minerals are not present <br />and that ubiquitous calcite is present in the development rock and ore. Trace <br />concentrations of nitric acid soluble sulfur are present in several samples. These trace <br />concentrations may be a result of trace barite (BaSO4) within the samples rather than <br />sulfide minerals. <br />The effluent pH values from the MWMP analyses provide additional data to evaluate <br />the potential for the rock to be acid forming. These data range from 7.62 standard <br />units (su) to 8.98 su with a median of 8.16 su. These development rock and ore sample <br />data indicate pH values well above the pH criteria of 5.8 su set forth in HRMMR <br />§1.1(2) and support that the Sunday Mines Group development rock and ore are <br />unlikely to generate acid rock drainage and are not considered acid - forming material. <br />13.2.2 Assessment of Potential Toxic - Forming Rock <br />This section presents evaluation of the potential for development rock and ore to be <br />toxic - forming as defined by HRMMR §1.1(1). <br />This evaluation considers mining conditions related to drainage and exposure, and <br />examines: <br />• The potential for development rock and ore to contain detrimental amounts of <br />chemical constituents, which could lead to direct contact risks to humans as a <br />result of incidental ingestion or inhalation; and <br />• The potential for development rock and ore to form leachate that contains <br />detrimental amounts of chemical constituents. <br />C \ Users \cwoodwardi Desktop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 d000 <br />13 -2 <br />