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KLEINFELDER Individual outcrops are labelled on Plate 4-1. A geologic section was compiled using elevations from the local topography map (see Plate 1-8) for the mapped outcrops. The section is presented on Plate 4-2. Bedding attitudes measured in outcrop indicate that the Mehrten strikes N20E, dipping 2 to 3 degrees east. This is not consistent with the overall structural information for the Mehten Formation but it is possible that local variation exists due to tectonic activity. Changes in elevation as a result of bedding attitude have been accounted for in the section. Subsurface information exists for the Foothill Landfill site in the form of boring and monitoring well logs from field activities performed in the summer of 1989. In addition five soil borings were drilled at the facility by Kleinfelder in 1985 9. A fence diagram was prepared from the monitoring well and soil boring logs as shown on Plate 4-3. The fence diagram indicates that interlayered silts/siltstones, clay/claystones and sands/sandstone of the Mehrten formation occur to a depth of at least 200 feet. The sediments have been broadly broken into four Groups I, II, III, and IV. Group I has been distinguished from Group II on the basis that Group I appears to be richer in finer grained sediments, such as clays and silts. Group III also appears to be richer than Group II finer materials. A common reddish claystone is used as the distinguishing layer for this group in the logs from _ MW-1 and MW-2. Group IV is distinguished because of the contact of finer sediments with coarse gravel and ground water. This material is still probably Mehrten formation. The material encountered in the borings has undergone varying amounts of cementation, so both sediment and rock terms are used to describe the lithology. A clay and claystone may, in fact, be the same material. 4.2 VADOSE ZONE 4.2.1 Permeability Table 4-1 presents the hydraulic conductivity of nine soil samples collected from B-3 and B- 4, based on falling-head permeability tests performed in the laboratory. The measured hydraulic conductivities of these soil samples range from 0.26 to 550*10-5 cm/s and have a mean of 186 * 10-5 cm/s. This range of measured hydraulic conductivity is consistent with the expected range for.silt and silty sand (Table 1-2). This range is also consisted with hydraulic conductivities measured on soil samples collected by Meinfelder in 1985. In the FOOTHILL 23