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San Joaquin County Record Center - 2 - 6 May 2022 630 North California Street Stockton, San Joaquin County observed immediately south of the west doorway to the warehouse along the exterior wall. At approximately 3.4 feet below ground surface (ft bgs) a metal object was confirmed measuring approximately four feet in diameter, based on magnetic response. Four continuous core borings, GP-1 — GP-4, were advanced in the vicinity of the identified UST to 30 ft bgs. Gasoline constituents were detected in soil samples submitted for laboratory analysis. Petroleum hydrocarbons were detected at maximum concentrations of 8,100 milligrams per kilogram (mg/kg) total petroleum hydrocarbons as gasoline (TPH-G), 48 mg/kg toluene, 190 mg/kg ethylbenzene, and 780 mg/kg total xylenes. On 29 March 2012, Condor excavated and exposed one single-walled steel UST and associated product piping. The UST was partially excavated to depths of approximately three to six ft bgs to confirm its location and estimate its dimensions. The top of the UST was observed at approximately 2.5 ft bgs, the bottom of the UST appeared to be at 6.5 ft bgs. The UST was measured to be four feet in length with a diameter of approximately 4 feet and a 375-gallon capacity. Visual observations indicated that the UST appeared to be in good condition with no visible holes or cracks, with obvious rust corrosion but was sound when struck with a hammer. The presence of sand inside of the UST suggested that the UST has been previously abandoned in place by filling with sand. No petroleum hydrocarbon staining of soil was observed in the sidewalls of the excavation. Due to the proximity of an active natural gas line, electrical line and the warehouse wall foundation, removal of the UST was not recommended. Soil samples were collected at the direction of SJCEHD staff. Petroleum hydrocarbons were not detected in soil samples submitted for laboratory analysis. The UST was filled with cement and abandoned in place, and the excavation was backfilled. In November 2013, one groundwater monitoring well, MW-1, was installed. Petroleum hydrocarbons were detected in the initial groundwater sample from MW-1 at 29,000 micrograms per liter (ug/L) TPH-G, 220 ug/L benzene, 5,600 ug/L toluene, 760 ug/L. In December 2018, Condor advanced two on-Site shallow soil borings, HA-2 and HA-3, and one off-Site boring, GP-5. Shallow soil samples from borings HA-2 and HA-3, and a grab groundwater sample from GP-5 were submitted for laboratory analytical analysis. TPH as diesel (TPH-D) was detected at 790 mg/kg in HA-3 at 5 ft bgs, no other petroleum hydrocarbons were detected in soil samples. Toluene was detected in the grab groundwater sample from GP-5 at 0.34 ug/L. CONSTITUENT DATA Soil - The maximum petroleum hydrocarbon concentrations detected in soil beneath the Site are shown in the following Table 1.