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5.0 CONCLUSIONS AND RECOMMENDATIONS In the Site Conceptual Model and Fourth Quarter 2002 Report, we recommended continuing to monitor wells KF-1, KF-3, and KF-5 through the end of 2003 and sampling them semi-annually to confirm that hydrocarbon concentrations continue to decline. San Joaquin County EHD subsequently requested quarterly sampling of these three wells, plus KF-2. All four wells were sampled in the first and second quarters of 2003, and the results are generally as expected. In the same report, we presented additional evidence to support our interpretation that groundwater contamination beneath the Kwikee Foods site is the result of eastward migration of a contaminant plume that originated at the former Chevron site. Since then, SECOR, Inc. has presented an alternate interpretation that separate plumes originated beneath both sites but have since commingled. We have reviewed SECOR's Conceptual Site Model report, but find no compelling data in that report to support that interpretation. Further, we note that the computer-generated maps presented in that report neither support that interpretation nor match the actual laboratory data that have been obtained over a period of several years. The report offered little discussion or explanation for this discrepancy. According to the SECOR interpretation, separate plumes of contaminated groundwater were present beneath the Chevron and Kwikee sites at some time in the past. We illustrate this concept in Figure 6, which is a hypothetical plot of gasoline concentrations in groundwater along an east-west transect from the western edge of the Chevron site to the eastern edge of the Kwikee site for an unspecified date prior to commingling of the two plumes. Both plumes are evident, but the plot • assumes that the release at the Chevron site was greater than that at the Kwikee site. This assumption is based on comparison of actual concentrations measured at the two sites. The plot also assumes that hydrocarbons were migrating away from the UST facilities toward MW-6, and that this well was near the margin of one or both plumes. Hence, early on, concentrations should have been lower in this well than in either MW-1 or KF-3. Figure 7 is a plot of the oldest concurrent data that are available from both sites. November and December of 1994, and October and November of 1995. In the 1994 data, only one plume is clearly evident, and the concentration peak at MW-1 implies that the center of this plume is near the Chevron UST facility. Chevron well MW-6 is located east of the plume's center, and the lower concentration (by 2,000 ppb) in KF-3 suggests that the latter well is only slightly farther from the center. The 1995 data suggest that a second plume may be present west of MW-1, in the vicinity of MW-4, and that these two plumes may have commingled in the vicinity of MW-3. However, no peak comparable to the hypothetical plume in Figure 6 is evident in either curve in the vicinity of KF-3 or KF-2. Thus, the commingled plume model is merely conjecture; there are no analytical data to support the_existence of a second plume beneath the Kwikee site. On page 1 I of their report, SECOR, Inc. (2003) also suggested that Kwikee Foods is the source of MTBE in groundwater at both the Chevron site and at the Boulevard Auto site (west of the Chevron site). SECOR based this suggestion on the fact that "(Kwikee Foods) is the only site that has had 6