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KLEINFELDER Public Works Department. Surface water samples were collected from South Paddy Creek to assess the potential impact from landfill runoff during rain storms. No evidence that hazardous waste is leaking from the landfill areas into the vadose zone, ground water, or surface water was found in this investigation. Standing leachate was not observed at the refuse/waste interface. Slightly acidic conditions may exist at some places under the landfill at the refuse/soil boundary and may have mobilized some metals in the soil. Metals appear to be slightly diluted at the boundary and slightly concentrated a few feet below the interface. The low concentrations that this observed trend is based on also may be attributed to natural variability in soils. Locally, the ground water gradient under the site is generally to the south-southwest with an average gradient of 0.25 percent. Water quality in the upgradient well (MW-1) is comparable to water quality observed in -2, a cross-gradient well, and MW-3, a downgradient well. Ground water quality in the other downgradient well, MW-4 appears to be different than water quality in the other wells. Most major ions, including chloride and sulfate, and total dissolved solids ( S) are elevated in -4 compared to the other wells. -4 is downgradient of the northern part of the secondary site, the northwest part of the primary site, and downgradient of waste water ponds operated by the San Joaquin County Housing Authority facility that is located north of the well. Chemical analyses:from these ponds are not available for comparison. -4 also is located adjacent to an irrigation ditch from which water may infiltrate to ground water. At this time the cause of the difference in ground water quality at MW-4 is unknown. Ground water in the wells does not appear to be impacted by metals or volatile organic compounds. Low concentrations of barium were reported in MW-4, and may be related to the source of higher TDS and ion concentrations in MW-4. This executive summary is subject to the limitations discussed in Section 13 of this report. F19-91-33 Page 2 of 30 Copyright 1991 KLeinfelder, Inc.