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several years with the exception of well P-8. The TDS in well P-8 decreased significantly • <br />in both 1991 and 1992 but has steadily increased since the last half of 1995 to a value of <br />approximately 3500 mg/l. The increase in well P-8 is above the levels expected for the 3rd <br />White Sandstone but may be natural based on natural concentrations observed in 2nd <br />White Sandstone well P-5. Figure B-8 presents TDS values for 2nd White Sandstone well <br />P-5 and shows that the concentration has been in the 2500 to 3000 mg/I range prior to <br />mining in this area. Natural water-quality concentrations in the 1st, 2nd and 3rd White <br />Sandstones are expected to vary over a similar range. Additional monitoring with time of <br />well P-8 is needed to help define whether the significant increase in 1996 and 1997 is due <br />to mining or to natural variations. Figure B-8 also presents 3rd and 2nd White Sandstone <br />wells GE-3 and 1st White Sandstone well GLUX-1 which consists of low TDS water. <br />Figure B-9 presents the TDS concentrations versus time for alluvial wells GC-3, • <br />P-1, J-1 and Coy. Lewis Shale well P-3 is also included in this plot due to its response to <br />the Pyeatt alluvial system. The TDS in well P-3 increased from 1986 through 1988 but has <br />had an overall decreasing trend since 1989. TDS concentrations in Pyeatt alluvial well P-1 <br />have varied with time as expected for a shallow ground-water system. The present <br />concentrations seem to be gradually declining with time. These variations in water quality <br />in well P-1 are within expected natural fluctuations for this ground-water system. <br />The alluvial ground water in Johnson Gulch has shown TDS variations with time <br />with a generally lower TDS in 1988, 1989 and 1990 and a higher value in 1992 through <br />1997. The 1996 and 1997 TDS values are generally lower in well J-1, which may be due <br />to the decrease in TDS in the backfill aquifer upgradient. <br />3-4 <br />• <br />