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08 September 2009 AGE -NC Project No. 03-1055 Page 2 of 19 however, no records of the UST removal are available with the Tracy Fire Department, Tracy Building Department, or the San Joaquin County Environmental Health Department (EHD). On 21 October 2003, during excavation activities, one 500 -gallon UST was discovered and the excavation was halted. The 500 -gallon UST was removed under the supervision of the EHD. The UST removal was documented in the AGE -prepared Well Destruction and Excavation Sampling Report, dated 23 March 2004. Copies of the Underground Storage Tank Unauthorized Release (Leak) forms for the site are provided in Appendix C. 2.2. SITE INVESTIGATIONS The following is a brief summary of the site assessment investigations conducted at the site to date: • May 2000 - Five soil probe borings were advanced at the site under the observation of an EHD representative; procedures and results of the investigation are documented in the AGE - prepared Preliminary Site Assessment Report, dated 24 August 2000. Probe borings were advanced in the former UST excavation, the southern and northern dispenser islands, and two assumed hydrogeologic down -gradient locations. All borings were advanced to depths of 20 feet bsg. Selected soil samples and one grab ground water sample were collected and analyzed from each soil boring. Total petroleum hydrocarbons quantified as gasoline (TPH-g) were reported in soil samples from the former dispenser areas and former UST excavation area; the approximate depth limits of hydrocarbon -impacted soil were between 15 feet and 20 feet below surface grade (bsg). TPH-g were reported in all grab ground water samples at concentrations ranging from 370 micrograms per liter (µg/1) in sample BI -H2O to 55,000 µgli in sample B3 -H20. Benzene was reported in all samples, except B5 -H20, at concentrations ranging from 0.54 µg/l in sample B 1-H20 to 160 µg11 in sample B3 -H20. Toluene was reported in all five ground water samples at concentrations ranging from 11 µg/1 to 25 µg11. Ethylbenzene was reported in sample B3 -H20 at 58 µg/1 and in sample B4 -H20 at 2.5 µg/l. Xylenes were only reported in samples B2 -H20, B3 -H20, and 134 -H2O at concentrations of 230 µg/l, 120 µg/1, and 1.9 µg/l, respectively. MTBE was not reported in any of the ground water samples analyzed. October 2000 - Hydrocarbon -impacted soil at the former northern dispenser area was removed with an excavator and 2.45 cubic -yard bucket and stockpiled on the eastern edge of the site; procedures and results of the excavation are documented in the AGE -prepared Interim Soil Excavation and Quarterly Report - Fourth Quarter 2000, dated 29 January 2001. Excavated soil was field screened for the presence of volatile organic compounds using an organic vapor meter (OVM). Ground water was present within the limits of the Advanced GeoEnviromnentai, Inc.