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�-= 21 September 2000 AGE-NC Project No. 97-0360 Page 7 of 8 5.0. SUMMARY AND CONCLUSIONS Based upon data collected on 13 July 2000, AGE concludes the following: .,., 0 Soil is impacted from at least 10 feet bsg to 25 feet bsg in the area of the former UST and south of the former UST area by TPH-d. • First encountered ground water is at approximately 10 feet bsg. • Ground water is impacted on the site by TPH-d. �. • Laboratory and field data suggest that TPH-d-impacted ground water is present in the area enclosed by P1 through P8, and extends laterally past the borings. • TPH-g was detected in one soil sample collected from P4 and ground water samples collected from P 1, P2, and P4, however according to the laboratory report,"strongly aged" gasoline or diesel range compounds are significant. r.. • The State of California drinking water standards, adopted under the Safe Drinking Water Act, have established maximum contaminant levels (MCLS) for benzene, toluene, ethyibenzene and xylenes at 1 µg/l, 150 pLg/l, 700 µg/1 and 1,750 µg/1, respectively. Concentrations of dissolved benzene detected in the grab ground water samples collected from P1 and P4 were above selected MCLs. �. • The State of California Department of Health Services has adopted aconcentration of 13 µg/1 as an action level(ALs)for MTBE in March 1999,and has adopted a concentration of 5 µg/1 as a secondary maximum contaminant level (MCL)in January 1999. The Concentration of ,r dissolved MTBE detected in the grab ground water sample collected from P4 was above the secondary MCL. • The vertical extent of petroleum hydrocarbon-impacted soil has been defined. The vertical extent of petroleum hydrocarbon-impacted soil does not extend past 20 feet bsg east,west, north and south of the former UST area, and does not extend past 25 feet bsg in the former UST area. Very low concentrations of TPH-d are present in the 20-foot and 25-foot soil samples collected from PI and P4, respectively. It is the opinion of AGE that the concentrations are low enough to assume vertical definition. The horizontal extent of petroleum hydrocarbon-impacted soil has been defined east, north, and west of the former UST area. The horizontal extent has not been defined south of the former UST area. • The horizontal and vertical extent of petroleum hydrocarbon-impacted ground water has not been delineated in any direction. Advanced GeoEnvironmental,Inc. it