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Homestake Mining Company May 10,2019 <br /> Regular(112d)Operation Reclamation Permit Application Package <br /> minor and temporary increases in suspended sediments, but these increases will be adequately <br /> controlled by the existing sediment Pond. <br /> 4.3.2.2. Water Infiltration Management and Segregation <br /> Water management strategies that can be employed to specifically address water quality at the <br /> Site include: 1) minimization of water infiltration into uranium source zones; and 2) minimization <br /> of water mixing and dilution following uranium release (i.e., water segregation), described below. <br /> Water Infiltration Minimization <br /> As described above, uranium loading to surface water occurs as a result of subsurface water <br /> passing through uranium bearing zones at depth, including minerals surrounding disturbed areas <br /> and disturbed/relocated low grade ore. Water infiltration exacerbates this uranium loading in two <br /> ways: 1)via direct contact of percolation with uranium sources, solubilizing uranium and carrying <br /> it downgradient; and 2) mixing of "clean" percolation with uranium-impacted subsurface water, <br /> which dilutes waters carrying uranium but increases discharge flow rates, presenting a greater <br /> challenge for treatment. BMPs that address water infiltration into near surface source zones <br /> include slope regrading and/or drainage management (re-routing and lining) to minimize <br /> percolation of surface water into zones that contain uranium, thereby preventing the release of <br /> uranium. Although HMC is currently investigating surface water management options, the current <br /> indications are that opportunities for achieving meaningful load reduction and/or reducing <br /> subsurface uranium load dilution via minimization of infiltration are few, given the disperse and <br /> regional nature of groundwater inputs to source zones. For example, only a small volume of water <br /> that moves through the bottoms of the rock dumps actually originates from snowmelt and <br /> precipitation from directly above; therefore, alternatives that include substantial capping/covering <br /> of rock dump surfaces to minimize infiltration would have low effectiveness as well as low <br /> practicability. In addition, this option would cause additional disturbance at the Mine, albeit <br /> temporary. <br /> Water Segregation <br /> Strategies for segregating impacted water from unimpacted water as a means of enhancing <br /> passive water treatment options are currently being investigated. For example, the rock dump toe <br /> drains installed during rock dump emplacement appear to have clogged and currently transmit a <br /> small proportion of the overall shallow groundwater flow moving through the dumps. Accordingly, <br /> impacted rock dump water does not express at the toe drains, but instead migrates through <br /> shallow alluvium downgradient of the dumps, discharging to surface water across along the length <br /> of the Indian and Tie Camp drainages. This results in mixing of clean and impacted water, <br /> increasing the volume of water that would require treatment. Maintaining segregation of these <br /> waters (e.g., by emplacement of a rock dump seepage capture system) could enhance the <br /> effectiveness and decrease the footprint of passive water treatment systems. <br /> EXHIBIT E-RULE 6 4.5(AMENDED RECLAMATION PLAN) Page 59 <br /> HOMESTAKE MINING COMPANY <br />