2018-07-02_PERMIT FILE - C2010089 (16)

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HYDROLOGIC RECLAMATION PLAN INTRODUCTION The hydrologic reclamation plan for the NHN permit area is presented in two parts. The first part focuses on specific practices which are conducted to minimize the impact of mining on the hydrologic balance within and adjacent to the permit boundary. The second part addresses those impacts that may occur regardless of these practices. The emphasis of the second part is on the monitoring of the extent and magnitude of mining impacts. Where possible, reference has been made to those sections which contain details regarding certain practices. PRACTICES EMPLOYED TO MINIMIZE THE IMPACTS OF MINING ON THE HYDROLOGIC SYSTEM Ground Water Ouality The mining practices that involve replacement of spoil material into mine pits are detailed in Section 2.05.4(2)(c) Backfilling and Grading. Topsoil and overburden handling plans are detailed in Section 2.05.4(2)(d) Overburden and Topsoil Handling. An extensive analysis of the spoil water quality and quantity was done for the bond release of New Horizon #1 area in the year 2000. Based on years of monitor hole data and spoil spring data, it was shown that although pyrite oxidation would slightly increase the Total Dissolved Solids (TDS) of the water emanating from the spoil, the levels of increased TDS and pH were low enough that when mixed with Tuttle Draw and the San Miguel River, the increases were negligible. It was found that the increases were expected for a considerably long period of time, probably from 400 to 1500 years. After this amount of time, the pyrite will be fully oxidized and the ground water quality will be back to background levels, which is still high in TDS. Because of the findings on negligible impacts to water quality, no special handling of materials is anticipated for mining operations conducted. The method of mining by removing the weathered, oxidized, free dig material separately from the unweathered bedrock and then covering the unweathered overburden with the weathered oxidized free dig material is done routinely to aid the mining operation and is not considered "special handling". The practices of dilution of any unsuitable overburden and burial have worked to date at the adjacent New Horizon Mine. Selective handling would only be used if some unforeseen overburden zone is much worse than any encountered to date. In this case, it would be buried deeper in the backfill spoil than what would occur in the normal overburden mixing. Each exploration hole, other drill or borehole, well, or other exposed underground opening except those used solely for surface blasting will be plugged or sealed to prevent acid or toxic drainage from entering the ground water, minimize disturbance to the prevailing hydrologic balance, and ensure safety. Any holes, wells or other exposed underground opening that will be temporarily inactive but eventually used for mining related purposes will be temporarily sealed at the surface and secured and protected for safety by surface structures or barricades. Section 2.05.6(3)(b)(v) Page 1 March 2018 (TR -16)