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3.0 WASTEWATER AND GROUNDWATER QUALITY 3.1 Wastewater Quality Historically, the two evaporation ponds, i.e., the North and South Ponds, received a mixture of process water(waste brine, wash water, and brine tank rinse water), storm water runoff from facility roadways and brining pads, and groundwater extracted from MW l. In addition, water from seasonal direct precipitation accumulated during the wet season. By the end of summer,the ponds would be dry, due to evaporative losses and seepage. Discharge to the South Pond ceased in 1994 and to the North Pond in 2004. Water quality samples retrieved from the two evaporation ponds since January 2002 are of sodium-chloride type and show high salinity due to the presence of table salt in the ` wastewater. Sodium and chloride concentrations have ranged from 3,700 to 16,000 mg/L (with a median of 8,100 mg/L) and 5,000 to 42,000 mg/L (with a median of 12,000 mg/L), respectively. The electrical conductivity and concentration of total dissolved solids (TDS) are accordingly high(LSCE, 2005a). 3.2 Groundwater Quality Due to its abundance in the waste stream generated at the SMS Briners facility and its conservative nature, chloride has served as a useful indicator for evaluating the impact of plant operations on groundwater quality. The comparison of water quality types encountered at the different groundwater monitoring points has also been useful in the analysis. The following discussion summarizes the most recent groundwater quality data as presented in the 2004 Annual Report (LSCE, 2005a). 3.2.1 Groundwater Quality - Shallow Zone The highest chloride concentrations,both historically and currently, have been measured at shallow well MW 1, located immediately west and adjacent to the North and South Ponds. Recent samples retrieved from this well had chloride concentrations ranging from 2,300 to 4,100 mg/L (2003 data). Chloride concentrations at other shallow wells ranged from 38 mg/L at Well A to 540 mg/L at MW4A in 2004. The impact of saline wastewater on water quality types is evident in the vicinity of the ponds in conjunction with elevated chloride concentrations encountered in MWl, MW3A, and MW4A. Such evidence is not seen at Well A and MW2, although chloride concentrations have, at times, exceeded the Water Quality Protection Standard(WQPS) of 89 mg/L (RWQCB, 2004; LSCE,2005a). _iJH00RFF & SCALMANINI CONSULTING ENGINEERS 4