2008-04-24_REPORT - C1981010 (2)

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The 2008 TSS values were small and similar to the low range of previously observed values. As expected, a general increase in TSS for an increase in flow is seen at the plots for the historical data from the sampled sites, with the 2008 data supporting the historical relationship between flow and TSS. The TDS of the surface water from the mine area is similar to the TDS from the non-mined area and; therefore, an increase has not been defined, except for an increase in TDS during low flow conditions at NPDES sites 001 and 011. Field pH values for all sites were similar to previous data collected. 2. PHC: Trapper does not anticipate recharge to the shallow aquifer systems to be adversely affected by mining operations in the Third White Sandstone. Short term localized disruptions may occur with respect to the Third White Sandstone. Trapper predicts the post-mining recharge to this unit will equal or exceed the pre-mining rate due to the enhanced permeability associated with backfill materials (PAP page 4/237). Wells GC-2, P-8, and GP-9 are used to monitor the Third White Sandstone. Wells GC-2 and GP-9 showed a water-level rise in 2008, showing good recharge with above average precipitation over the last few years. Overall the water levels in P-8 were higher in 2008. Variations in natural recharge to the 2nd White Sandstone affect the aquifer greatly. Mining effects on the system have not been detected. 3. PHC: Groundwater quality constituent concentrations for some parameters are expected to be higher than pre-mining concentrations for an extended period of time after mining (PAP page 4-238b). Estimates indicate that higher sulfate and TDS concentrations from some of the backfilled aquifers at Trapper Mine may, in the absence of any ameliorating factors, last for several hundred years under a worse case scenario in which the entire mass of pyrite available in the spoil body is oxidized (PAP page 4-438b). Elevated TDS concentrations can develop as spoil aquifers are re-saturated following mining (PAP page 4-438d). The TDS of water in backfilled wells GD-3 and GF-5 (QR Aquifer) are some what higher but similar to those of native aquifers in these areas. TDS values for backfilled wells GF-7 and GF-11 are much higher than the naturally observed concentrations and are declining from peaks observed in the 1990's. The water in HI aquifer well GP-3, which is in the proximity of reclaimed A pit, has not been influenced by mining. The 3?d White Sandstone wells are down gradient of mining starting in 2000 and changes in water quality in these wells in 2008 are similar to previous natural changes. Sulfate concentrations in wells GD-3 have been fairly steady with a slight decrease in 2008. Concentrations in GF-4 were fairly steady in 2008 and have been fairly steady the last few years. Sulfate concentrations in P-8 increased in 2007 and 2008 after six years of declining values. Sulfate in wells GD-3, GF-7, GMP-1, GF-11 and P-8 have likely been affected by mining while the remainder of the increases could be from natural variations, mining or a combination of both. At the completion of mining, Trapper's surface water will be utilized in the former mine permit area for watering livestock and wildlife. Based on Trapper's 2008 AHR, the current surface water quality is