1995-12-07_HYDROLOGY - M1984049 - Laserfiche WebLink

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Groundwater wells should be sampled initially for the following: pH TDS Al Fe Se Bill Conductivity SO4 As Pb Ag Major cations Chloride Ba Mn Na Major anions Nitrate Bo Hg Zn Alkalinity Nitrite Cd Mo Hardness Ammonia Cr Ni WAD CN Detection levels should be low enough to detect whatever amount would be regulated for surface water at a low hardness Of local surface water hardness is not known, I would recommend assuming an equivalent hardness of 100 mg/L as CaCO3.) Detection levels for most of the metals will be sufficient if analyzed by ICP. However, other methods will need to be employed for Cd, Cu, Pb, Hg and Ag. A chart of the standards was furnished to you earlier. Monitoring: surface water. Surface waters should be collected on the same frequencies, and analyzed for the same parameters. Collection points should include at least two points in the diversion ditch (to assure that the road or other sources have not contaminated the ditch), the station above the mill tailings and above the diversion ditch (Station 31), and the station below the tails (preferably Station 24). It is not evident in the data that groundwater from the site gets collected at Station 22, so I might recommend that it not be sampled. If a low-flow station is needed downstream, you should collect below station 24. Reclamation. As the above report indicates, this operation appears not to be minimizing impacts to the hydrologic balance, either to surface water or groundwater. Part of the metal and acid load is certainly coming from pre-law tailings, but part also appears to be coming from the new tailings as well. As time goes on, it is likely that the rate of oxidation (weathering) will increase, and the new tailings will become more of a problem. Given this situation, the recommendations for reclamation deal more with an overall reclamation scheme than the scheme that is currently provided in the permit. Ideal reclamation of the tailings would require sealing the tails from water and oxygen in order to minimize the rate of weathering. If most of the tails are to be reclaimed in place, the best that could be done would be to stack as much of the tailings as possible into a single pile, cap the pile, and provide an upland diversion. Also, the rate of groundwater flow into and out of the base of that pile should be reduced by some means. Before more tails are added to this operation, the tailings ponds should be properly lined and protected from erosion and deterioration. 5