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(1.6 and 1.3 ppm). Lead was detected in both samples, at concentrations that range from background levels (14 ppm)to slightly elevated levels (44 ppm). No hydrocarbons were detected in any of the samples from CM2 above a depth of 50 feet. Gasoline was detected in the bottom sample at 590 ppm, and to uene, ethylbenzene, and xylene were present slightly above the detectiori limit. The water sample from CMI was also contaminated (Table 2). Gas line was present at a concentration of 62,000 micrograms per liter(µg/1, =parts per billio - ppb)rand various BTEX compounds were also present at elevated concentrations. The chromatogram is typical of unmodified gasoline. Tertiary butyl alcohol (TBA) was ah o detected, although MTBE and other oxygenates were not present. 5.0 DISCUSSION AND CONCLUSIONS In view of the fine-grained,relatively low-permeability sediment th underlies the site, the increase in hydrocarbon concentrations from 15 to 50 feet in'CM 1 is very surprising, as is the presence of moderately elevated concentrations as deep as 5 feet and in the groundwater. The absence of hydrocarbons in CM2 above 50 feet an I their appearance at this depth indicates that the top of the contaminant plume is nearly 5 feet deep at a distance of 25 feet from the tank excavation, and suggests that the pl ime spreads laterally with depth. The high concentrations above 80 feet are probably due to downwar leaching of gasoline through the unsaturated zone. The sharp decline in concentrations below this depth, along with the noticeably wetter conditions from 80 to 90 feet, is evidence that the watertable was between 75 and 80 feet during the time of the gasoline release. When the water table began to fall in the 1980's,hydrocarbons began to desorb from the water and adhere to soil particles, creating a slightly contaminated"smear zone"from 75 to 90 feet. Based on the evidence collected during the investigation,it is clear that both soil and groundwater are impacted at this site. It is unknown whether any of the private drinking water wells in the area are threatened, but the nearest well (on the ad acent property to the - south)has,not been impacted, according to Mr. Marty Hartzell of the Regional Water Quality Control Board, who sampled this well in the summer of 200 . The vertical limit of soil contamination is approximately 100 feet, but the lateral limit i o=ld not be determined from the data obtained in this investigation. 5