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well data collected by Opal Cliffs in 1995 showed significant detections of gasoline constituents in groundwater wells upgradient of the Chevron site but south and southwest of Opal Cliffs. Water samples collected that year from the basement sump on the former Chevron site showed contaminant levels at very low to non-detect values.' In 1998, by contrast, water samples collected when the sump flooded showed concentrations of TPH-g and BTEX from 1,000 to 10,000 times greater than the values detected three years earlier.' The low concentrations of BTEX in the sump water in 1995, followed by high concentrations in 1998, without any new source at the former Chevron site, provide direct evidence that gasoline and groundwater with high concentrations of gasoline constituents have migrated from the Opal Cliffs site onto Chevron's site. The significant increase in contaminant levels from 1995 to 1998 is much more consistent with operation of the sump pump drawing in contaminants from the Opal Cliffs plume than from lingering contamination at the Chevron site, which had not operated for more than twenty-five years. The subsequent investigation conducted by Chevron from 1998 to 2000 consisted of eleven soil borings dispersed across an area of about 9,600 square feet. The data showed only highly degraded and weathered diesel-range hydrocarbons in shallow soil samples. At depths of 10 feet below ground surface (bgs) and greater,the volatile hydrocarbon content reported for soil samples reflects a relatively fresh gasoline constituent profile inconsistent with a pre-1972 release. Gasoline constituents were detected in groundwater samples obtained from each of the soil borings, including very high concentrations from three borings extending south from an upgradient Opal Cliffs monitoring well, indicating the presence of separate-phase gasoline moving with groundwater. These data suggest that a past release of petroleum hydrocarbons may have occurred at the former Chevron site but that any such release does not contribute to the need for cleanup at the site. Chevron also points to testimony of personal observations of soil conditions from persons involved with excavations at the former Chevron site. The former property owner has stated that the soil beneath the USTs was"clean" when the tanks were removed in 1973. The ' BTEX concentrations were 2.9 parts per billion(ppb),0.4 ppb,0.7 ppb and 1.2 ppb,respectively. TPH-g was non-detect,or less than 50 ppb. ' BTEX concentrations were 2,500 ppb, 1,400 ppb,670 ppb,and 2,400 ppb. TPH-g was measured at 16,000 ppb. 5.