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kn KLEINFELDER EXECUTIVE SUMMARY Foothill Sanitary Landfill is located in eastern San Joaquin County on Waverly Road, approximately 1/2 mile south of Sheldon Road. Geologically, the landfill is located on the eastern edge of the Great Valley Province and is underlain by partially consolidated rocks of the Mehrten Formation. The Mehrten Formation is dominated by sandy andesitic sediments that were deposited by streams flowing from the Sierra Nevadas. Regionally, the Mehrten Formation on the eastern side of the Great Valley dips 1 to 2 degrees to the southwest. Locally, it appears that the Mehrten dips 2 to 3 degrees east in outcrops in and around Foothill Landfill. Falling-head permeabilities measured in samples collected within the Mehrten Formation during this investigation are consistent with those expected in silts and silty sands, ranging from approximately 10"6 to 10-3 cm/sec. Few ground water wells existed in the vicinity of Foothill Landfill at the time of this study. Based on Department of Water Resources (DWR) records and a drive-by reconnaissance survey, approximately eight wells exist within one mile of the landfill. These wells are generally domestic or cattle supply wells. Little information exists on regional ground water gradients and quality in this area, but it appears that ground water is relatively deep _ (150 to 250 feet below ground) flows generally south and west in the area, and water quality is good. The general regional water type is calcium/bicarbonate and it appears that total dissolved solids (TDS) in the water are generally less than 500 mg/1. Disposal operations at the landfill began in 1965. It is estimated that approximately 4 million cubic yards (in-place) of waste have been disposed at the landfill since that time. The waste is largely municipal solid waste. Some biomedical waste and asbestos were also accepted at the landfill. The landfill is currently active. Preliminary design plans estimate that the area that currently contains waste will be completed around the year 2015. During the solid waste assessment test investigation, soil samples were collected from the soil/waste interface at the bottom of the landfill and from the soil at the east toe of the landfill to assess the nature of leachate in these areas. Soil samples were also collected from 10 to 20 feet below waste in two areas under the landfill to assess vadose zone pore fluid chemistry. Ground water samples were collected from wells upgradient of, adjacent to, and downgradient of the landfill to assess ground water gradient and quality. Surface water samples were collected from creeks and a reservoir near the landfill, and from FOOTHILL 1