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the first quarter (March) and fourth quarter (October) confirm that all three Kwikee wells were impacted at high concentrations. Concentrations were even higher in the Chevron wells, with both MW-3 and MW-4 above 60,000 ppb and MW-1 at 56,000 ppb. Gasoline was even detected in the most upgradient well (MW-5) at 240 ppb. 4.2 Northward Migration: 1996 The shape of the plume changed somewhat in 1996, and although the northwest-southeast elongation from MW-4 toward MW-1 was still evident, a secondary southwest-northeast axis from MW-1 toward MW-7 had also appeared (Figure 23). This axis extended as far north as MW-9, which was somewhat less impacted than in 1995. Because groundwater flow was northward toward MW-9 in 1996, this decline in the TPH-g concentration could not be due to cessation of plume movement to the north. A more likely explanation is that the decline is due to lateral diffusion. TPH-g concentrations also declined in both MW-3 and MW-5, which is to be expected with northward groundwater flow, but the increase from 11,000 to 15,000 ppb in MW-8 is not consistent with northward flow. The reason for the increase is not apparent from the data. 4.3 Continued Northward Expansion: 1997 Further northward elongation of the plume took place in 1997, and the TPH-g concentration in MW-9 peaked at 15,000 ppb (Figure 24). This coincided with the maximum development of northward groundwater flow, as shown in Figure '14. Rather surprisingly, none of the three wells north of MW-9 became impacted, although MW-10 and MW-11 were clearly downgradient and on trend of the plume. The concentration in MW-3 declined further, and the concentration also declined in MW-8, meaning that both of these wells recorded the expected decline under conditions of northward groundwater flow. However, the concentration increased slightly above the detection limit in MW-5, which would not be anticipated. Upgradient Environmental did not sample the Kwikee site in 1997, but samples were collected by Chevron's consultant on August 26, at the same time the Chevron site was sampled, and the results are shown in Figure 24. Elevated concentrations were still present over at least the southern half of the Kwikee site, but concentrations had declined somewhat from those in 1995 and the TPH-g contours have retreated slightly westward from their 1995 position (Figure 22). 4.4 Reversal: Southward Migration, 1998 In 1998, groundwater flow reversed and became due south (Figure 15). The gasoline plume responded to this change, and a strong, narrow, northeast-southwest elongation developed, extending all the way to MW-5 and culminating with that well reaching a much greater TPH-g peak than it had ever recorded previously (Figure 25). The concentration of 9,600 ppb stands out as a major red flag for this well, which had not experienced concentrations in excess of 1,000 ppb in more than more than four years. At the same time, concentrations declined further in MW-3 and 16