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October 2004 water quality data obtained from the shallow zone at five locations via the CPT/Hydropunch method were used to refine the estimated areal extent of the release from r the unit(Figure 3-1). The results support the previously estimated areal extent of saline water migration as documented in previous annual reports (LSCE, 2004a and 2003a). The combined data provide an increased degree of confidence in the estimated extent of the salt plume to the north, east, and south of the ponds. Precipitation resulted in adverse site conditions in late October 2004, which resulted in the temporary halt of the evaluation- monitoring program. The completion of the evaluation-monitoring program is a part of this report. 3.2.2 Groundwater Quality - Deep Zone The highest chloride concentrations, both historically and currently,have been measured at deep well MW3B, located immediately south of the South Pond. Most recent samples retrieved from this well had chloride concentrations ranging from 90 to 96 mg/L (2004 data). Chloride concentrations at other deep wells ranged from 7.9 mg/L at Well E to 25 mg/L at MW4B in 2004. Most recent chloride concentrations at P5 and P4 were 45 mg/L (March 2002) and 7.3 mg/L(October 2003). The WQPS is 27 mg/L for the deep zone. Previous comparisons of water quality types using Schoeller plots (LSCE, 2004a) and the apparent elevated chloride concentrations encountered in MW3B reflect the effect of saline wastewater on deep groundwater in the immediate vicinity of the ponds. Evidence of saline wastewater impacts on deep zone water quality has not been observed at wells MW4B, P4, B, D, and E. Specifically, groundwater quality monitoring results for several of these deep wells show that chloride concentrations have been low and stable for the past ten or more years. October 2004 water quality data collected as part of the evaluation monitoring program from three deep zone locations via the CPT/Hydropunch method were used to refine the estimated .. areal extent of the release from the unit (Figure 3-2). The results support the previously estimated and very local extent of saline water migration in the deep zone(LSCE, 2004a and 2003a). The additional data also confirmed the rapidly declining salinity to the east of the ponds and indicated that the affected zone to the south of the ponds is smaller than previously estimated. The extent of historical saline water migration away from the ponds has been minimal because the horizontal hydraulic gradient at the site is generally small and frequently changes direction in response to seasonal influences, including pumping. r © LUHDORFF & SCALMANINI CONSULTING ENGINEERS 5 r