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Pre-Design Investigation Workplan Former Manufactured Gas Plant—Lodi, California • PAH-, TPH-, naphthalene- and lead-impacted soils occur adjacent to the former four-inch oil conveyance pipeline from the surface to 12 feet bgs. However, soils directly below the pipeline,situated one feet bgs,do not appear to be impacted. • Impacted soils were not encountered below the two historical gas distribution lines that extend 15-feet into South Sacramento Street from the former general shop and storeroom building(meter house) located in the northwest corner of the Site. • PAH-, TPH- and lead-impacted soils extend off-site from the west property limit into South Sacramento Street from the surface to 7n feet bgs. • PAH-, TPH-, naphthalene, and lead-impacted soils, primarily, extend off-site from the south property limit into the Lodi Iron Works property from the surface to 3 feet bgs. • Benzene in soil gas was detected at concentrations ranging from 1.3 to 7.5 micrograms per cubic meter (ug/m) with the highest concentrations occurring in the shallow and deep samples collected from location SG-4 located in the center of the Site in the vicinity of the former generator and boiler building. Naphthalene was detected in soil gas in the shallow and deep samples collected from location SG-3 situated along the west property limit at concentrations of 23 and 15 ug/m3, respectively. Naphthalene may also occur in soil gas at other locations at the Site based on raised laboratory reporting limits that range from 44 to 220 ug/m3 at locations SG-2,SG-4,and SG-6. • Low concentrations of gasoline- and diesel-range petroleum hydrocarbons, BTEX , two PAH compounds (naphthalene and acenapthene) and select metals occurred in one or both grab groundwater samples collected at locations GW-1 and GW-2 situated along the southern property limit. With the exception of a detection of naphthalene of 0.40 micrograms per liter (ug/L) in the grab groundwater sample collected from boring SB-18, constituents were not detected in the groundwater samples collected from the vicinity of the former water supply wells. 2.5.6 Soil Vapor Extraction Pilot Testing (2010) A soil vapor extraction (SVE) pilot test was conducted at the Site by Stantec in September and October 2010. The objective of the SVE test was to evaluate the feasibility of using SVE to reduce concentrations of VOCs in soil within the footprint of the former oil tank prior to excavating soils within and surrounding this area of the Site. The pilot test consisted of installing one 6-inch- diameter polyvinyl chloride (PVC) SVE test well within the former oil tank (at the approximate location of SB-6) and six 3/4-inch-diameter PVC observation wells at locations surrounding the former oil tank. Additional details associated with this study are included in the report entitled Results of Soil Vapor Extraction Pilot Testing, prepared by Stantec, dated October 29, 2010 (Stantec, 2010b). Subsequent to the pilot test it was concluded that the use of SVE in advance of remedial TERRA PACIFIC GROUP Page 7 April 4, 2012