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} t 28 December 2004 AGE-NC Project No. 04-1238 Page 2 of 5 • On 08 and 09 July 1993, eight USTs were removed from the subject property: two 10,000-gallon gasoline USTs and one S,OOOgallon gasoline UST, all located in a common excavation (common UST pit); five additional USTs of undocumented size and unknown petroleum product content were discovered east of the initial excavation and removed. Significant petroleum hydrocarbon contamination was encountered during the UST removals and the excavations were expanded to remove excess contaminated soil. Soil samples collected from the excavations detected total petroleum hydrocarbons quantified as gasoline (TPH-g) in soil at the northern portion of the common UST pit, at a concentration of 460 milligrams per kilogram (mg/kg). Based on information available at EHD (Cambria- prepared Site Summary and Closure Path Recommendations, dated 01 November 1996) it appears this soil contamination was never abated. • During excavation activities on 09 July 1993,two grab ground water samples(water 41 and water#2)were collected from the excavation. TPH-g, benzene, toluene, ethylbenzene and xylenes(BTEX)were detected in the ground water samples at maximum concentrations of 34,000 micrograms per liter (µg/1), 3,200 µg/1, 1,600 µg/1, 840 µg/1 and 4,300 µg/1, respectively (American Consulting Remediation and Construction hic.-prepared Tank Removal-Soil Sampling Report, dated 10 August 1993). Based on the information available at EHD, it does not appear that the hydrocarbon impact to ground water was addressed adequately in this area. • On 03 November 1992,monitoring wells MW-1 through MW-3 were installed on-site and a quarterly ground water monitoring program was initiated. On 20 March 1995, two additional ground water monitoring wells were installed off-site to determine the lateral migration of petroleum hydrocarbon impacted ground water. • Quarterly ground water monitoring occurred from December 1992 until June 1996. TPH-g, benzene and methyl-tertiary butyl ether (MTBE) were detected in ground water samples collected during monitoring events at maximum concentrations of 2,400 µg/1, 11 µg/1 and 51 µg/1,respectively(Cambria-prepared Site Summary and Closure Path Recommendations dated 01 November 1996). DRILLING On 13 December 2004, four soil borings (B-1 through B-4)were advanced at the former Chevron site utilizing a van-mounted Geoprobe 5400 direct-push probing unit equipped with 1.25-inch probing rods: • Boring B-1 was advanced to a depth of approximately 20 feet below surface grade (bsg) down gradient from the former UST areas; Advanced GeoEnvironmental,Inc.