SITE INFORMATION AND CORRESPONDENCE

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California Fuel Station � Page 2 of 3 The TPH-g and BTEX concentrations are often very similar in the three zones and generally show the same fluctuation through time; for instance the fourth quarter 2006 analytical results for TPH-g at MW-13A, MW-13B, and MW-13C were 260 µg/1, 290 µg/1, and 220 µg/l, respectively. This seems unusual as the upper and lower well intervals have 45 feet of vertical separation and fine-grained units occur between the wells. This suggests that there may be communication in between the depth intervals. Since there are no other data points in the deeper zone, the vertical and lateral extent of impacted groundwater cannot be considered to be defined, and therefore the EHD does not consider this site ready for closure. • Proposed tracer test. In the QR, AGE recommends that a tracer test utilizing fluorescent dye and/or food grade coloring dye be performed to evaluate the integrity of MW43A, MW-13B, and MW-13C. EHD directs that a workplan be submitted to accomplish this by November 16, 2007. Once the integrity of this well has been evaluated, the implications regarding the vertical extent of your plume should be evaluated. Central Valley Regional Water Quality Control Board (CVRWQCB) must give approval before any substances can be injected into groundwater. • Proposed CPT„borings. Based on the deep groundwater impact at MW-13A, MW-13B, and MW-I3C, AGE recommends utilization of three cone penetration test (CPT) soil borings to depths as great as 150 feet bsg to characterize of soil and collect grab ground water samples on-site in the vicinity of MW43, in the city right-of-way near MW-4, and in the apartment complex located towards the northeast. At this time the EHD can not concur with this recommendation, however, if the results of the tracer test show that the integrity of MW-13A, MW-1313, and MW-13C is sound and the deeper aquifer zones are impacted, the proposed investigation well be justified. • Proposed soil vapor samples. As noted in the QR, the CVRWQCB is requiring evaluation of Environmental Screening Levels (ESLs), California Human Health Screening Levels (CHHSLs) and the potential for vapor intrusion into buildings prior to closure consideration. AGE stated that a vapor intrusion evaluation is warranted at this site and a workplan should be prepared to collect at least two to three 5-ft soil vapor samples as noted in Figure 2 in the QR. Submit a workplan to collect the soil vapor samples and a technical justification for the selected sampling points to the EHD by November 16, 2007. • Proposed_installation of a new SVE well. In the QR, AGE recommended installation of at least one additional SVE well north of AW-2 (shown in Figure 2 in the QR) to ensure recovery of air-sparged contaminants. Before approving installation of additional SVE wells or reinitiating the SVE/IAS system operation, the EHD believes additional monitoring data should be obtained and evaluated to justify such actions. The EHD would approve advancement of a confirmation soil boring in the proposed SVE well location to evaluate the effectiveness of the recent SVE/IAS operation; if significant soil contamination is encountered, the boring could be converted to an