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• Underground Storage Tank and Product Piping Removal Report - Former Towo (Unocal) Service Station#5421 June 2, 1998 SITE DESCRIPTION The subject site is situated on the northwest corner of Pacific Avenue and Willora Road in Stockton, California (Figure 1) Station facilities included two 10,000-gallon double-wall glasteel gasoline USTs and one 520-gallon double-wall glasteel diesel UST, two dispenser islands, and one station building Locations of the pertinent site features are shown on Figure 2 FIELD ACTIVITIES The USTs and related product piping was removed on April 15, 1998 The hydraulic lifts and sand/water separator were removed on April 21, 1998 Equipment removal, soil sampling, and overexcavation activities were observed by Ms Letitcia Briggs and Mr Harlin Knoll (SJCPHS) The USTs, hydraulic lifts, and related product piping were found to be in good condition with no signs of holes, leaks or cracks Upon completion of excavation activities, clean imported fill material was used to backfill the excavations to the original grade The material was placed in lifts and mechanically compacted to Tosco specifications The compaction testing report is attached SOIL SAMPLING After removal of the USTs and related equipment, soil samples were collected as described in the attached Field Methods and Procedures Soil samples were collected from either an excavator or backhoe bucket, or with a hand-driven sampling device Groundwater was not encountered in the excavation or subsequent overexcavation which extended to a maximum vertical dept of 26 feet below ground surface (bgs) A total of 17 soil samples and 15 soil stockpile samples were transported to Sequoia Analytical (Sequoia), located in Redwood City (ELAP #1210), California, for chemical analytical analyses Soil samples were collected at the direction of Harlin Knoll of the SJCPHS and analyzed in accordance with their guidelines Analytical methods and results are summarized in Table 1 Sample locations are shown on Figure 2 Copies of the certified analytical reports are attached Former UST Complex S_a> Iing 3 Upon removal of the gasoline USTs, a soil sample was collected from beneath both ends and the center of the USTs at depths of approximately,15 5 to 17 feet below ground surface (bgs) Each soil sample was analyzed for TPHg, benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds, methyl t-butyl ether (MtBE), and six oxygenate compounds No petroleum hydrocarbons were detected in sample UX-1-16 The remaining samples contained petroleum hydrocarbons concentrations ranging from not detected to 25,000 ppm TPHg, not detected to 270 Rpm benzene and not detected to 170 ppm MtBE All samples were reported as not detected for oxygenate compounds Former UST Complex Overexcavation and Samplin Upon collection of the initial UST complex samples, overexcavation was initiated in the northwest corner of the excavation in the vicinity of sample UX-2-15 5 Samples UX-2-22 and UX-2-25 were 140162 02 2