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• b-A. TDS and sulfate concentrations increase as one progresses downstream and with time. <br />Well 31-A2 is downstream of the discharge of the Wadge Impoundment. It is similarly a <br />CaNg-S04 type water. TDS values at this well also fluctuate from year to year, implying <br />that those changes ere due to annual changes in precipitation. <br />The one well sampled in the Grassy Creek alluvium, 33-A, has a CaNg-504 type water. TDS <br />values at this well have gradually increased from 1988 to 1991, possibly due to a <br />combination of aquifer recharge with water from the Wadge Impoundment and the <br />precipitation noted in prior years. The TDS average for 1992, however, has lowered in <br />comparison with prior yearly averages. <br />In the Cow Camp Creek (tributary of Fish Creek) alluvium, water quality is measured et two <br />wells. Well 46-A has a MgCaNe-504 type water. This well exhibited a high TDS <br />concentration prior to mining in the vicinity (2,068 mg/L in November 1982). High TDS <br />values are also exhibited in the alluvium upstream of this well at Spring Mb (14,200 mg/l <br />in September, 1985). Apparently, water quality throughout the alluvium is affected by a <br />high concentration of naturally occurring salts that are further concentrated by <br />• evapotranspiration. TDS values et Well 46-A increased gradually up [o October 17, 1986 <br />(with a TDS of 3,498 mg/l), after which TDS values have steadily decreased with a 1992 <br />average TDS value of 2,339 mg/l. This is in spite of the fact that iDS values upstream at <br />the 004 pond have increased steadily since 1982 (with a TDS of 3,464 mg/l on September 8, <br />1992). <br />The second well in the Cow Cemp Creek alluvium, Well 69-A, was completed in the summer of <br />7988. It is located approximately one and one-half miles downstream of Yell 46-A. The <br />water samples et this well have displayed a CaNg-S04 type water since monitoring began, <br />The average annual TDS values fluctuated very little from 1989 through 1992. The average <br />TDS values for this well in 1992 were 49 percent higher than Well 46-A. This is most <br />likely a result of the high amount of salts in the soils of Twentymile Park (see later <br />discussion of the Twentymi le Park end Fish Creek surface water systems). <br />Yell 68-A, completed in the Bond Creek alluvium, was also completed in the summer of 1988. <br />It is located approximately two miles downstream of the 008 pond. The water samples at <br />this well have displayed a CaM gNa-SO type water since the onset of monitoring. TDS values <br />4 <br />• (4,836 mg/l average, 1992) were significantly higher during 1992 than measured at NPDES <br />008 (1,745 mg/l average, 1992), but the average TDS measured during 1992 was lower than <br />the 1990 and 1991 averages at this well. <br />7 <br />