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AEI Project No. 319400 • • May 22, 2013 Page 2 of 5 groundwater on the property, the potential exists that the hydraulic fluid within the lift systems contained toxic polychlorinated biphenyls (PCBs). According to TBD plans dated from 1985, one lube bay (southernmost) was to be converted into a carwash and one hoist was to be removed. There was no mention or appearance of the second historical hoist which appeared on the 1967 plans. The 1985 plans show this area as a storage area. No documentation was available to indicate whether any hoists were removed or that soil and/or groundwater samples were collected and analyzed for PCBs. In addition, due to the relatively shallow depth of groundwater in the area of the property, expected between 5 and 19-feet below ground surface (bgs), the potential exits that groundwater could be impacted by such a release. Additionally, a document titled Case Closure Summary-3725 Tracy Boulevard, Tracy (CRA, April 26, 2007) concerning previous subsurface investigation and remediation activities was also reviewed for the Phase I ESA. According to the report, four soil borings were drilled in the vicinity of the USTs by Kleinfielder in 1985. Petroleum hydrocarbons were detected in three (3) of the borings at 10 feet below ground surface (bgs). The source of the hydrocarbons was not identified. In November 1985, three (3) steel-walled USTs were removed and replaced with three 10,000-gallon double-walled fiberglass USTs in the same location. Soil and groundwater samples were collected by Canonie Engineers from the excavation, and reported Total Petroleum Hydrocarbons (TPH). Investigation and remediation activities related to releases on the subject property were performed between 1989 and 2008 by Delta Environmental and Cambria Environmental. Three (3) monitoring wells were installed in 1989 and destroyed in 2008. Contaminated soil was excavated and removed from the property, or utilized as backfill. Groundwater monitoring activities continued from September 1989 until January 2007. TPH-g, BTEX and fuel oxygenates have been low to non-detect in all soil samples collected since 1990. Residual impacted soil was left onsite, with the caveat that should the property be redeveloped, all UST systems and piping and impacted soil must be removed to the extent feasible. According to a No Further Action Letter reviewed, case closure was granted by the Regional Water Quality Control Board (RWQCB) and SJCEHD in May 2008. The subject property is currently equipped with three (3) 12,000-gallon double-walled fiberglass USTs and one (1) 12,000-gallon diesel UST. According to information reviewed at the SJCEHD, the USTs were installed in 1990. Review of reasonable ascertainable information pertinent to the status and operation of the fuel storage tank system did not reveal any reported discharged or gross compliance deficiencies. However, environmental monitoring, consisting of soil and/or groundwater sampling, is the only effective method for identifying an undetected release. Based on the age of the on-site USTs, AEI was unable to rule out the potential that a release has occurred. As such, AEI was retained to perform a baseline Phase II subsurface investigation in the areas of the current UST tank system and the former hydraulic lifts, to evaluate if the property has been adversely impacted by historical and current gasoline service station operations. 3.0 Geology and Hydrogeology Based on a review of the United States Department of Agriculture (USDA) Soil Survey for the area of the subject property and CRA's Case Closure Summary – 3725 Tracy Blvd, Tracy (April 2007), soils underlying the property are characterized as fine grained soils (silt and clay). The report noted a layer of coarse sand which was encountered at approximately 15 feet bgs