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GEOMATRIX Upgradient Area Analysis of groundwater samples collected from upgradient shallow zone monitoring well MW-16 ' indicates that background shallow-zone groundwater is of fair quality, with chloride concentrations ranging between 34 and 55 mg/C, nitrate concentrations ranging between 3.1 and 27 mg/C, and total ' dissolved solids (TDS) concentrations ranging between 410 and 620 mg/C. Analysis of groundwater samples collected from upgradient intermediate-zone monitoring well MW-17 indicates that back- ground intermediate-zone groundwater is of poor quality, with chloride concentrations ranging between 420 and 720 mg/C, nitrate concentrations ranging between non-detected (less than 0.5 mg/C) and 0.33 mg/C, and total dissolved solids (TDS) concentrations ranging between 820 and 1,400 cng/C. A ' discrete-depth groundwater sample collected from the deeper zone (approximately 100 feet bgs) had a chloride concentration of 740 mg/C. These water quality results are consistent with regional groundwater quality trends. Upgradient groundwater is generally of poor quality with elevated concentrations of chloride resulting from intrusion of saline water. The concentration of chloride increases with increasing depth. This poor quality groundwater is overlain by a thin veneer of fair quality (shallow zone) groundwater resulting ' from the infiltration of rainwater, river water,and/or irrigation water. ' Facility Area Analysis of groundwater samples collected from 10 shallow-zone monitoring wells located at the Facility indicate detectable concentrations of several organic constituents, including: ' • the halogenated volatile organic compounds (VOCs) chlorobenzene, chloroform, and 1,2- dichloropropane(1,2-DCP); 1 • the triazine pesticide atrazine; • the chlorinated herbicide dinoseb; and the fumigant 1,2-dibromo-3-chloropropane(DBCP). In addition, groundwater samples collected from several shallow zone monitoring wells contained the inorganic constituents ammonia, chloride, and nitrate at elevated concentrations compared to the up- ' gradient shallow zone well (MW-16). Historically, concentrations of ammonia have ranged from non- detected (ND) to 580 mg/f, concentrations of chloride have ranged from 93 to 890 mg/C, and concentrations of nitrate have ranged from ND to 460 mg/Z. ' Groundwater samples collected from the four intermediate zone monitoring wells at the Facility are ' generally of poor quality. Groundwater samples from two of four intermediate zone monitoring wells at the Facility currently or previously contained detectable concentrations of organic constituents. Groundwater samples from intermediate zone well MW-18 typically contained low concentrations (less ' than 1.2 micrograms per liter [µg/C]) of chlorobenzene, tetrachloroethane, and/or 1,1,2-trichloroethane. i�naomrnae�woaumemnse�»ia� 7