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3. Proposal for Further Characterization of Site Geology and Hydrogeology a. Borehole Logging/Litho logic Description All boreholes will be logged by an experienced California Professional Geologist or Professional Engineer (Civil) according to the Unified Soil Classification System(USCS). Drilling is discussed in Section III.B. Figure 5 is a borehole log compiled by PEI's geologist (PG/CEG, CHG/PGp) for one of the borings drilled at the site in August 2012. (This log was typical of all of the boreholes drilled to groundwater and beneath the permeable unit to the total depth of the borehole.) b. Aquifer Characterization At the adjoining H&H site, it appears that there were two water-bearing zones, both discontinuous laterally. From the earlier investigation at the subject site, the water-bearing zone at 26 to 28 ft bgs appears to be continuous across the site—as observed in four temporary groundwater monitoring wells. In the proposed investigation, eight (8) permanent wells are planned to intercept this zone. From the borehole log information, geologic cross sections will be plotted together with first-encountered and static groundwater levels, and noting contaminant concentrations in soil and groundwater samples. A potentiometric surface map will be constructed to calculate groundwater gradient (magnitude and direction). Initially, hydraulic conductivities of the subsurface materials will be estimated from their soil classifications; and seasonal naturally and artificially induced variations in groundwater flow will be researched from available well and other data from the vicinity of the site. No laboratory or well tests for aquifer characterization are proposed at this time. It is prudent to verify the magnitude of the contaminant concentrations in subsurface media and potential health risks before embarking on a long-term and costly investigative program. This work plan is, therefore, designed to obtain sufficient soil samples to assess impact to shallow (0 to 26 ft bgs) soils, and to obtain reliable—and reproducible—groundwater samples to assess the impact to the shallow groundwater beneath the site. C. Contaminant Flow Path Identification The currently proposed investigation will focus on the contaminant flow path in the 2-ft-thick water-bearing zone previously identified at the site; consequently, the horizontal component of flow will assume primary focus.