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E Site Background Information: Quick N Save # 1 Page 2 of 5 UNDERGROUND STORAGE TANK REMOVAL On 21 October 1999, three USTs and associated piping and dispenser islands were removed from the site by Stockton Service Station Equipment Company (SSSEC) of Stockton, California. Approximately 150 cubic yards of hydrocarbon-impacted soil were removed and stockpiled during excavation of the USTs. Nine samples were collected beneath the USTs, six samples were collected beneath the dispenser area and two laboratory-composited soil samples were collected from the excavated stockpiled soil. Methyl tertiarybutyl ether (MTBE), tertiarybutanol (TBA), tertiary-amylmethyl ether (TAME) were detected in each of the soil samples collected from the site. Totalpetroleum hydrocarbons quantified as gasoline (TPH-g) were detected at concentrations as high as 3, 849 mg/kg beneath the western end of the center UST location. Volatile aromatics including benzene, toluene, ethylbenzene and xylenes (BTEX) were detected at concentrations as high as 29 mg/kg from the same sample location. SOIL EXCAVATION On 20 April 2000, approximately 175 cubic yards of petroleum hydrocarbon-impacted soil were excavated from the former UST area. Excavation was performed by SSSEC. The highest concentrations ofpetroleum hydrocarbons, TPH-g and fuel additives were detected near the eastern end of the center UST (sample EN46'). Fuel oxygenating compounds, including MTBE, TBA and TAME, were detected in each of the soil samples collected from the site at concentrations as high as 11 ,000 mg/kg. TPH-g was detected at concentrations up to 12,000 mg/kg beneath the western end of the center UST location. BTEX was detected at concentrations up to 1 ,800 mg/kg (total xylenes). PREVIOUS SITE ASSESSMENT On 05 and 06 August 2003, four soil probe borings (Bl through B4) were advanced to a total depth of 50 feet bsg utilizing a van-mounted Geoprobe 5400 direct-push probing unit equipped with 1 .25- inch diameter probing rods. Two borings were advanced east and west, respectively, of the former UST excavation. The third boring was advanced north of the former UST excavation while the fourth boring was advanced east of the dispenser islands . TPH-g, MTBE, andBTEX compounds were detected in soil samples analyzed from all fourborings. TPH-g was detected in soil samples at maximum concentrations of 21 ,000 mg/kg in boring B1 at 35 feet bsg. MTBE was detected in soil samples at maximum concentrations of 5 .6mg/kg (134-35') . BTEX compounds were detected at maximum concentrations of 27mg/kg, 600mg&g, 270mg/kg, Advwiced GeoEnvironmental, Inc.