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Report-Groundwater Inve„..gation First Student Bus Facility(Former A.W. Hayes Facility) 2005 Navy Drive—Stockton, CA 1.0 INTRODUCTION This Report describes activities conducted and information developed during a groundwater investigation conducted at the First Student Bus Facility (Former A.W. Hayes Facility) located at 2005 Navy Drive in Stockton California (hereafter Site) (see Figure 1 —Site Location Map). 2.0 BACKGROUND In 1987, one (1) 1,000-gallon waste oil underground storage tank (UST) and one (1) 12,000 gallon diesel UST were removed from the Site. The former locations of the two (2) USTs are illustrated on Figure 2 — Site Plan. Laboratory analytical results of soil samples collected from beneath the two (2) former USTs indicated that volatile aromatic compounds (BTEX) were detected in soil from beneath the south end of the diesel tank, and that low-level polychlorinated biphenyls were reported in the soil sample from beneath the waste-oil tank. An assessment of the extent of the petroleum contamination at the Site began in October 1999 by Ramcon Engineering and Environmental Contracting (hereafter Ramcon). Six (6) on-site locations were selected, and soil and groundwater samples were collected for analysis. Groundwater was encountered at a depth of approximately 15 feet below ground surface (bgs). Soil sample results collected during this investigation revealed that a trace amount of oil was detected in only one (1) of the soil samples. Groundwater sample results collected during this investigation revealed that total petroleum hydrocarbons as gasoline (TPH-g), total petroleum hydrocarbons as diesel (TPH-d), and some halogenated organic compounds (chlorinated solvents) were detected. According to the San Joaquin County Environmental Health Department (hereafter (EHD), an additional groundwater assessment was warranted, and in December 2003, three (3) shallow monitoring wells (MWs) and one (1) deeper MW were installed on-site. The wells were installed by Ramcon. Monitoring wells MW-1, MW-2 and MW-3 are screened from 12 to 25 feet bgs where groundwater was first encountered, and MW-4 was screened from 45 to 50 feet bgs. There were no detections of TPH-g or TPH-d in any of the soil samples collected and analyzed, but some chlorinated solvents were detected in all the soil samples collected and analyzed, and in the groundwater samples collected and analyzed from MW-1, MW-2 and MW-4. No chlorinated solvents were detected in the groundwater sample collected from MW-3. Low concentrations of gasoline and diesel constituents (benzene and xylene) were detected in the groundwater samples collected from MW-2 and MW-4. The groundwater samples collected from MW-1 and MW-3 had no detections of the gasoline and diesel constituents. The December 2003 soil and groundwater investigation conducted by Ramcon is summarized in their June 22, 2004 report entitled "Summary Report, Additional Soil and Groundwater Investigation, Former Underground Fuel Tank Site, 2005 Navy Drive, Stockton, California. ” 1