2008-02-20_REPORT - C1980001 - Laserfiche WebLink

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wells TR-1.5, TR-3, TR-4, WR-1 and TCS-1 for the period of record. Specific conductivity and TDS values for the three alluvial wells have remained fairly constant over the majority of the period of record. While specific conductivity and TDS values at sites TR-3 and TR-4 are consistent with values obtained during the baseline studies, these parameters and several others have elevated rapidly and remained elevated at TR-1.5 since 1995. The source of the elevated values is not readily identifiable. A few factors which may have contributed to the elevated values were mentioned in the 1996 Report (i.e., inundation of the area in late spring of 1995 and the laying of telephone cable immediately upstream of the area during the summer of 1995). If the elevated values resulted from those activities, the values should have returned to more historic levels during the past decade. However, the values have remained elevated. It appears that the alluvium in this area is reflecting upstream alluvial water containing high levels of TDS, possibly from an old abandoned underground mine up the Little Trout Creek drainage. This conclusion is based partially on the similarity of the water quality between TR-1.5 and WR-1. The location of the underground mine is shown on Exhibit 3.1-1 of the permit. Specific conductivity and TDS in, Well WR-1 have progressed from an elevated state each spring to a lower state in the fall for the past several years. This phenomenon was caused by infiltration of snowmelt water leaching various minerals within the unsaturated zone of reclaimed spoil. As the enriched flow was released over the course of the summer, the conductivity values lessened to that of the stagnant saturated zone. The mounded aquifer exhibits a more diluted state each spring with a return to steady-state as the summer progresses. Specific conductivity and TDS concentrations exhibited the same trends in 2007 as found during previous years of monitoring. The lowest specific conductivity value in 2007 was recorded at monitoring well TR-3 in October with a reading of 608 umhos/cm @ 25 °C and the high was recorded at monitoring well TR-1.5 in September with a reading of 4960 umhos/cm @ 25 °C. The lowest TDS concentration in 2007 was recorded at monitoring well TR-3 in August with a value of 380 mg/I. and the high was recorded at monitoring well TR- 1.5 in June with a value of 4720 mg/L. 4.2.4 Ground Water Calcium, Magnesium and Sodium Charts 26, 27 and 28 show calcium, magnesium and sodium concentrations for monitoring wells TR-1.5, TR-3, TR-4, WR-1 and TCS-1 for the period of record. Calcium is the major cation found in all of the wells, except TCS-1 which is sodium rich, with concentrations of sodium and magnesium occurring in lesser quantities. The sodium concentration at TR-1.5 in May 2001 was 179 ppm. This value is inconsistent with the historical sodium concentrations and the levels after May 2001. Therefore, either sample contamination or laboratory error is suspected. TR-1.5 generally contained the lowest concentrations of cations with a slight increase occurring downstream at TR-3 and TR-4 for the majority of the record. However, elevated levels of these parameters at TR-1.5 began to occur in 1995 consistent with the elevated specific conductivity and TDS levels previously mentioned. Elevated levels of sodium concentration occurred at TR-4 during the 2004 and