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Section 2 <br />Potential for Adverse Impacts <br />The potential for the development rock to generate toxic leachate was evaluated using <br />MWMP testing and evaluation of the volume of percolation that would be expected <br />from the piles. The MWMP testing indicates that the rock could release dissolved <br />constituents into pore water within the pile if sufficient water were present at the <br />mines. However, the mines are located within an arid area and detailed analyses of <br />percolation from the piles using water balance estimates and unsaturated flow <br />modeling indicates that generation of significant quantities of leachate from the piles <br />is unlikely. These analyses show that water infiltrating into the piles would be <br />expected to be removed by evaporation in the arid environment at the Sunday Mines <br />Group; this is validated by the absence of visual drainage from development rock <br />stockpiles that have been in place for decades. <br />Based on the evaluations of potential direct contact risks and risks related to <br />development of leachate from the piles summarized above, neither the development <br />rock nor the ore are considered Acid or Toxic Producing Materials. Additional detail <br />on the evaluation of acid and toxic producing materials is included in Attachment B — <br />Environmental Geochemistry Investigation of Rock and Soil Material Sunday Group Mines <br />and Section 13 — Geochemical Data Analysis. <br />2.2.3 Acid Mine Drainage <br />As defined in the HRMMR § 1.1 (2): <br />"Acid Mine Drainage" means contamination of water by low pH or heavy <br />metals that occurs from mined or disturbed materials as a result of the <br />chemical and biological oxidation of reactive sulphide minerals when exposed <br />to air and water. The possibility of generating Acid Mine Drainage exists <br />where the pH of any exposed or potentially exposed overburden, waste rock, <br />mill tailings, waste water treatment sludge or other mined, placed, disposed or <br />stockpiled material has the potential to develop a pH of 5.8 or less..." <br />As previously stated, development rock and ore are unlikely to generate acid mine <br />drainage. <br />Based on these conclusions, no designated chemicals or acid- or toxic - forming <br />materials are present at the Sunday Mines Group. Additional details on these <br />evaluations are included in Attachment B — Environmental Geochemistry Investigation of <br />Rock and Soil Material Sunday Group Mines and Section 13 — Geochemical Data <br />Analysis. <br />C \Users\cwocdward■DesMop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />2 -5 <br />