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Pre-Design Investigation Workplan Former Manufactured Gas Plant—Lodi, California 2.5.4 Water Supply Well Destruction Activities (2009) In June 2009, the two former water supply wells were investigated, cleaned out, and abandoned under permit with the San Joaquin County Environmental Health Department. This work was conducted by Stantec. The wells were cleaned out using a low-pressure air rotary system, and found to be an estimated depth of approximately 65 and 76 feet, respectively based on a change in the encountered resistance of the drilling equipment. The wells were subsequently video logged, which confirmed the estimated total depth and the poor condition of the well casings. Water was not encountered in either well. The wells were abandoned in-place by grouting with neat cement from the bottom of each well to the ground surface in accordance with San Joaquin County requirements. The well casing for each well was cut below the surface at a depth of 2.5 feet. A detailed description of well abandonment activities is summarized in the Well Destruction bort prepared by Stantec,dated August 13,2009. 2.5.5 Remedial Investigation (2008 — 2010) Intermittently during the period 2008 through 2010, Stantec conducted RI activities at the Site. These activities consisted of a geophysical investigation, the collection of soil samples from 72 soil borings (SB-1 through SB-69 and AK-1 though AK-3), 11 test pits (IP-1 through TP-11) and one surface soil sample location (SS-10), passive and active soil gas sampling at six locations (SG-1 through SG-6), and the collection of four grab groundwater samples from soil borings GW-1, GW- 2,SB-18,and SB-20. Soil and groundwater samples were analyzed for one for more of the following analytical tests: BTEX,TPHg,TPHd,TPHmo,PAHs, CAM17 Metals,and cyanide. Additionally,it is noted that the grab groundwater samples were analyzed for dissolved metals. The analytical results associated with RI activities are included in Appendix A, and a summary of the results is presented below as documented in the Draft Final RAW (Stantec,2011b): • PAHs, petroleum hydrocarbons, and lead impacts in soil were widespread throughout the Site between the ground surface and approximately 5 feet bgs. Localized areas of deeper impacted soil extending between 7 and 21 feet bgs were encountered in several areas of the Site in the vicinity of former MGP features. • A localized area of benzene-impacted soil with concentrations ranging from 0.140 to 3,700 mg/kg was identified between the ground surface and approximately 12.5 feet bgs within the footprint of the former oil tank at boring SB-6. • MGP impacted soil (lampblack) was observed in the footprint of the former oil tank, beneath and in the immediate vicinity of the lampblack separators, and beneath the former gas holder#3. • PAH-, TPH-, naphthalene-, lead- and benzene-impacted soils occur in fill material within the footprint of the former oil tank and beneath the tank and surrounding area to a depth of approximately 21 feet bgs. ERRA PACIFIC GROUP Page 6 April 4, 2012