2009-03-02_PERMIT FILE - C1980004A (9)

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Table N-1 • PHC East Salt (2003-2007) Creek SW-1 Conductivity Irrigation Season Increase Decrease 2003 -5.1 2004 -18.4% 2005 0.24% 2006 -7.09% 2007 -9.24% 5-Year mass balance -8.2% The comibed discharge generally improves the conductivity of East Salt Creek surface waters. However, in 2005 there was a slight increase, but the 0.2% increase is nearly • negligible as the increase was only 4 micromhos/cm. The mass balance for the irrigation season is calculated by multiplying the flow by the conductivity and dividing by the sum of flow. See Tables N-3 through N-7 for yearly mass-balances. (Mass balance is for the irrigation season only). The East Salt Creek Alluvium is recognized as an alluvial valley floor. Data gathered over the last several water years for GW-3 demonstrates the combined discharge has not had a negative impact on the alluvial groundwater. As shown below, nearly all conductivity data recorded falls between the GW-3 baseline and the combined water average conductivity reference line. Since nearly all the data points fall below the baseline for GW-3, it is not likely the combined discharge has increased the conductivity of the alluvial groundwater. The combined discharge could only lower the conductivity of the alluvial groundwater since the conductivity of the combined discharge is less than the conductivity of GW-3. The situation is the same at all of the groundwater monitoring wells. The baseline conductivity of all of the GW wells exceeds the average conductivity of the water discharged from the mine and gob pile. Therefore, the conductivity of the alluvial groundwater can only be improved by the combined discharge. The most recent data gathered for GW-9 located immediately down gradient of the gob pile, is shown below. As concluded with GW-3, it is likely the comk~ined water discharge will only improve the conductivity of the alluvial groundwater. Appendix N - TR-16 - 4 - 10/08