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Wendy Cohen - 2 - 23 October 2007 Volpi Farm Property, Stockton the waste oil handling area, and trench T4 was near the eastern edge of the dispenser for the 7,500-gallon diesel AGT (see Attachment 1). Soil samples collected from Trench T1 showed petroleum contamination in the area of the 1,000-gallon AGT. The soil sample collected from the west wall had total petroleum hydrocarbons as gasoline (TPHg), TPH as diesel (TPHd), TPH as motor oil (TPHmo), and benzene at 19,000 milligrams per kilogram (mg/kg), 10,000 mg/kg, 7,800 mg/kg, and 180 mg/kg, respectively. The grab groundwater sample from Trench T1 contained TPHg, benzene, and methyl tert butyl ether (MTBE) at 16,000 micrograms per liter (pg/L), 690 pg/L, and 4,900 pg/L, respectively. Soil and groundwater results are presented in Attachments 2 and 3, respectively. Later in July 1998, Volpi excavated five additional trenches around the 1,000-gallon gasoline AGT to determine the lateral extent of soil contamination. Soil samples were collected from trenches T5, T6, and T7 and grab groundwater samples from T7, T8, and T9. Soil and groundwater contained minor concentrations of petroleum hydrocarbons. The soil and groundwater results are summarized in Attachments 2 and 3, respectively. In December 1999, Volpi excavated about 300 cubic yards of contaminated soil from the area of the 1,000-gallon AGT to a maximum depth of 11 feet bgs. Excavated soil was sent offsite for disposal. Soil results are presented in Attachment 2. The contaminants remaining.in soil after the excavations and trenching are summarized below. Volpi collected soil samples from the floors of each of the excavations and the results are shown on Attachment 2. Sample location T1-E was removed during the July 1998 excavation. Contaminants remaining in soil (mg/kg) TPHg TPHd TPHmo Benzene MTBE 2 ft 15 -4,900 3,600 —5,900 81 -330 0.19 -52 0.65 - <130 6 ft <1.0 - 220 <1.0 - 450 <5.0 - 770 <0.005 - 26 <0.05 - 30 8 ft <1 — 4.3 <1 — 4.1 <5 — 13 <0.005 — 0.02 <0.05 — 0.18 10- 11 ft <1.0 <1.0 <5 — 5.9 <0.005 - <5.0 <0.05 GROUNDWATER INVESTIGATION ACTIVITIES In July 1998, Volpi collected grab groundwater samples from the irrigation ditch and the domestic well at the Site. The ditch sample contained maximum TPHd and TPHmo at 6,800 pg/L and 62,000 pg/L, respectively. The domestic well sample do not contain petroleum hydrocarbons above reporting limits. Attachment 3 presents the grab groundwater results. On 31 May 2000, Volpi installed six monitoring wells (MW-1 through MW-6) to determine the lateral extent of groundwater pollution. All six wells were screened from five to 15 feet bgs. Soil samples collected during drilling of borings MW-1 through MW-4 and MW-6 contained petroleum hydrocarbons. On 6 September 2002, Volpi installed an additional monitoring well (MW-7) at the Site. Soil samples collected from this boring did not contain petroleum hydrocarbons. Soil sample results from the well installations are shown on Attachment 2. Monitoring wells were sampled sporadically from 2000 to 2005. Groundwater flow direction is south-southeast to south-southwest with an average depth to groundwater of five feet bgs.