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LFR Inc. • conducting a focused membrane interface probe (MIP) investigation in the vicinity of the Bank of Stockton to assess the lateral and vertical extent of the plume area (Section 3.1) • collecting additional groundwater samples from selected A- and B-zone wells to evaluate biogeochemical conditions at the Site (Section 3.2) • evaluating the potential for cis-1,2-DCE stall (Section 3.3) • obtaining detailed information from ERD substrate vendors to perform a cost benefit analysis of different substrates (Section 3.4) 3.1 Bank of Stockton MIP Investigation In mid-2006, LFR conducted a groundwater investigation to aid in the potential design of an effective ERD system by assessing the extent of more permeable lithologic units and higher-concentration Hazardous Substances (chlorinated solvents) in the vicinity of the Bank of Stockton where relatively higher concentrations of Hazardous Substances have historically been detected in groundwater. This investigation was conducted in accordance with LFR's "Work Plan to Conduct a Focused Membrane Interface Probe Investigation, Lincoln Center, Stockton, California," dated April 27, 2006, and the corresponding approval letter from Ms. Marie T. McCrink of the RWQCB, dated May 15, 2006. The site lithology in the vicinity of the Bank of Stockton is illustrated in interpretive cross sections. The locations of these cross sections are shown on Figure 6. Cross sections A-A' and B-B' are presented on Figures 7 and 8, respectively, and were constructed (manually interpolated) primarily from cone penetration testing (CPT) data, supplemented by lithologic data obtained during this MIP investigation and at the time of monitoring well installation. The locations of the CPT borings, MIP borings, and monitoring wells used to generate the cross sections are shown on Figure 6. Site lithology in the vicinity of the Bank of Stockton is generally consistent with the findings of previous investigations, and the findings of this investigation better define the lateral and vertical extent of lower sand channel intervals. The coarse-grained sand interval encountered between approximately 82 to 100 feet bgs in the borings for monitoring wells MW-205B and MW-301C could not be verified at all locations during the MIP investigation because of refusal at shallower intervals, but was encountered in thinner sequences at several locations, verifying the site conceptual model that the deeper target interval of this investigation is an isolated channel feature. In reviewing cross section B-B', which is oriented in a north/south direction and perpendicular to the presumed east/west channel alignment, the thickest portion of the target interval is shown to be limited to the proximity of the Bank of Stockton. The sand encountered at well MW-301C from approximately 82 to 100 feet bgs pinches out to the north at boring MIP-20 and to the south at boring CPT-220. Similarly, cross section A-A', which is oriented in the cast/west direction and parallel to the presumed channel alignment, shows the thickest portion of the channel at well MW-301C and shows thinning to the west at borings CPT-122/GEW-021B and to the east at boring MIP-19. Page 8 wp-PhV IRA-Sep07-Final-06750.da:1G