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08 September 2009 AGE -NC Project No. 03-1055 Page 18 of 19 impacted boring SB2; 2) the borings are located in an upgradient location to the Tracy Diner former UST areas; and 3) the non -detection of constituents in boring MW14-15, located between the former Tracy Diner UST areas and borings B 13 through B15. Based on the estimated lateral and vertical extent of residual adsorbed TPH-g which currently impacts soil and a review of analytical results, AGE estimates approximately 104 pounds, equivalent to 17 gallons, of TPH-g remain present at the site. Based on grab ground water investigations coupled with ground water monitoring well data, it appears a large mass of impacted ground water emanating from the former Chevron site extends easterly and northeasterly from the former Chevron off-site onto the western sidewalk of Adams Street (MW -11, B9, B 10 and B 11), the center of Adams Street (B 12 through B 15), the eastern sidewalk of Adams Street, north of the former Tracy Diner Site (138), and possibly on the former Tracy Diner site (B5). • Impacted ground water emanating from the former Tracy Diner site appears to be concentrated near the former 500 -gallon UST area (MW -2; TPH-g were reported at or below detection limits in the July 2009 monitoring event, however this well is typically impacted with TPH-g), and upgradient in well MW -6. • It appears there is considerable commingling of the former Chevron and Tracy Diner ground water plumes in Adams Street in the vicinity of borings B 12 and B 13; however, the former Chevron commingling appears more aggressive in Adams Street. • The vertical extent of impacted ground water at the former Tracy Diner site appears to be limited to the water table as evidenced by the generally non -detect, deep screened (between 30 feet and 35 feet bsg) ground water monitoring wells MW -13 and MW -14. • Based on the extensive commingling of the former Chevron and Tracy Diner plumes, determination of the remaining dissolved TPH-g mass is not feasible without including former Chevron contamination. • Based on trend analyses of analytical data verses time and linear regressions, the estimated compliance date for wells MW -6 and MW -8 is projected to be in April 2011. • Between 2000 and 2003, a cumulative 730 cubic yards of hydrocarbon -impacted soil was removed from the site through soil excavation. Based on the average hydrocarbon concentrations of TPH-g in excavation soil samples, UST removal soil samples and soil boring samples, an estimated cumulative 84 gallons or 268 kg of gasoline were removed from the site between 2000 and 2003. • Soil vapor intrusion does not appear to be a concern at the site due to the following: 1) hydrocarbon -impacted shallow soil (between surface grade and 12 to 15 feet bsg) was removed during the 2000 and 2003 over -excavations of the former UST and dispenser areas (Figures 7 through 9); 2) remaining hydrocarbon -impacted soil appears to be at depths of r Advanced GeoEnvironmentai, Inc-