Laserfiche WebLink
Section 3 <br /> <br />Assessment of Potential Acid-Forming Rock <br />The section presents an assessment of the Denison Sunday Mines Group development rock and <br />ore regarding its potential to be acid- forming as defined by the HRMMR. The HRMMR §1.1(2) <br />defines acid mine drainage as: <br />"Acid Mine Drainage" means contamination of water by low p1l or heavy metals that <br />occurs from mined or disturbed materials as a result of the chemical and biological <br />oxidation of reactive sulfide minerals when exposed to air and water. The possibility of <br />generating "Acid Mine Drainage" exists where the pH of any exposed or potentially <br />exposed overburden, waste rock, mill tailings, waste water treatment sludge, or other <br />mined, placed, disposed or stockpiled material has the potential to develop a pH of 5.8 or <br />less..." <br />Evaluation of the potential for acid mine drainage is based on evaluation of ABA data, <br />observational data regarding mineralogy of the mine rock, and effluent pH data from MWMP <br />column tests. <br />ABA data for development rock and ore stockpile samples are shown in Table 3-1. These data <br />show an overall low sulfur content and excess of neutralization potential over acid potential in <br />all samples. ABA data are compared to the empirical thresholds described in Section 2 to <br />evaluate the potential for the rock to generate acid in the future. <br />The first threshold is based on the NNP. The NNP of development rock and ore samples <br />collected at the Sunday Mines Group range from 32.5 to 270.7 t/ki: CaC03 eq. with a :median <br />value of 56.7 t/kt eq. These NNP values are greater than the 20 t/kt CaC03 eq. threshold, which <br />indicates that the development rock and ore has a low potential to generate acid. ABA data are <br />compared to the second empirical threshold in Figures 3-1 and 3-2. This threshold is based on <br />the NP:AP ratio. All samples exceed the NP:AP ratio threshold of 4, which indicates that the <br />samples are unlikely to generate acid. <br />The ABA data support field observations that visible sulfide minerals are not present and that a <br />ubiquitous amount of calcite is present in the development rock aj id ore. Trace concentrations <br />of nitric acid soluble sulfur are present in several samples. These trace concentrations may be a <br />result of trace barite (BaSO4) within the samples rather than sulfide minerals. <br />The effluent pH values from the MWMP analyses provide additional data to evaluate the <br />potential for the rock to be acid forming. These data range from 7.62 standard units (su) to 8.98 <br />su with a median of 8.16 su. These development rock and ore sample data indicate pH values <br />well above the pH criteria of 5.8 su set forth in HRMMR §1.1(2) and support that the Sunday <br />Mines Group development rock and ore are unlikely to generate acid rock drainage and are not <br />considered acid-forming material. <br /> <br />Cm 3-1 <br />TA64986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.12 - Soil, Ore, Rock Data Assessment Reporl\Sunday Rock Rt port\final repornReporrTinal Sunday Mines Group Sell Ore Rock <br />Data Assessment Reporl_051509.doc