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05 September 2002 AGE-NC Project No 99-0605 Page 2 of 6 — 3.0. UNDERGROUND STORAGE TANK REMOVAL AND OVER-EXCAVATION On 30 December 1998, three USTs were removed from the site by Stockton Service Station Equipment Company, Inc. (SSSE). On 19 February 1999, SSSE excavated hydrocarbon-impacted soil from the former UST and dispenser area; AGE personnel were on site to collect and field-screen soil samples and to direct the excavation operation. Approximately 90 cubic yards of soil were removed from the floor and side walls of the excavation area and stockpiled adjacent to the excavation. A total of six soil samples were collected from the floor and sidewalls of the excavation and six soil samples were collected frons the soil stockpile (Figure 2). After completion of the interim remediation, the excavation was backfilled with clean fill material and the twelve soil samples were submitted for laboratory analysis. Results of the laboratory analysis indicated that: • TPH-g was not detected above the reporting limit of 1.0 milligrams per kilogram(mg/kg) in any of the soil samples collected from the floor of the excavation. TPI1-d was detected at a concentration o f62 mg/kg in one sample(S 1-8);the other samples had TPl i-d concentrations below the reporting limit. BTEX compounds were not detected at concentrations at or above the method reporting limit. MTBE was detected in four soil samples at a maximum concentration of 14 mg/kg (S4-18). TBA, DIPE, ETBE, and TAME were not detected at concentrations above the reported limits. • TPH-g was detected in four- stockpile samples at a maximum concentration of 210 mg/kg (SP-3-2). TPH-d was detected in all samples at concentrations ranging from 5.9 to 220 mg/kg. Toluene was detected in one sample(SP-3--3) at a concentration of 04 mglkg. Two samples (SP-3-2 and SP-3-3) contained concentrations of MTBE at 0.32 and 0.13 mg/kg. Additionally, two samples (SP-3-2 and SP-3-3) contained TBA at concentrations of 7.8 and 1.5 mg/kg, respectively. Analytical results of soil samples are summarized in Table 1 and 2. Based upon the detection of MTBE at concentrations as great as 14 mg/kg in soil and at depths as great as 18 feet below surface grade (bsg), .AGE recommended further subsurface investigation at the site to assess the MTBE impact to soil and ground water. On 27 August 2001, the stockpiled soil was disposed of at Forward Landfill. .9dvuncErd Gcolrnvironmenial,Inr.