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State of Califomia Caltfomla Environmental Protection Agency Department of RXIC Substances Control 530 mg/kg, mercury at 0.21 mg/kg, and 1.5 mg/kg. In February 2006, nine additional surface samples were collected across the site. Results from the sampling indicated the presence of PAHs, metals, and TPH in site soils. No detectable concentrations of BTEX,VOC's, organochlorides, PCBs or herbicides were reported In.these samples. The results of the 2006 sampling were as follows: • PAH concentrations ranged from 0.43 mg/kg to 340 mg/kg. • Metals were detected above reporting limits in all samples,with lead reported at up to 24,800 mg/kg. • TPH (diesel)was detected at concentrations ranging from 16 mg/kg to 4,900 mg/kg. • TPH(motor oil)was detected at concentrations ranging from 19 mg/kg to 7,700 mg/kg. Remedial investigation Work Plan . An August 7,2008 Remedial Investigation Work Plan was prepared for the site to identify methods used to identify and delineate areas of the site that may have elevated chemical concentrations. The Work Plan proposed to implement Geoprobe sampling at 16 locations and passive gas sampling at 17 locations, followed by active soil gas sampling at the areas with the highest volatile chemical concentrations. Groundwater sampling was proposed for two site locations. The Work Plan indicates that groundwater near the site is approximately 60 feet below ground surface and flows to the south. Remedial Investigation Completion Report DTSC received a June 8, 2010 Remedial Investigation Completion Report(Report)detailing the findings of the Remedial Investigation Work Plan. This Report indicates that the chemical impacts from manufactured gas plant operations are typically confined to the upper 3-5 feet of soils. Surface soils at the site are contaminated with petroleum hydrocarbons, lead, and PAHs. Soils beneath a former oil storage tank were found to be impacted with total petroleum hydrocarbons to a depth of 70 feet below ground surface, and soils beneath an associated oil-conveyance pipeline have been impacted 5 to 12 feet below ground surface. Four soil borings were advanced to first encountered groundwater. The results of the groundwater sampling indicated that two of the four borings had low concentrations of petroleum hydrocarbons and related constituents. The Report concludes that based on site conditions and geology, the constituents detected in the groundwater samples do not appear to be related to site operations. Groundwater sampling in the vicinity of the former site water supply wells confirms that the wells did not act as pathways for migration of contaminants to groundwater. Soil Vapor Extraction Pilot Testing DTSC received the results of a Soil Vapor Extraction Pilot Testing Report on October 29,2010. The soil vapor pilot testing was performed in the area of the former oil tank at the site. The conclusions of the soil vapor extraction pilot test were that the soils in the area of the former tank were capable of maintaining a vacuum and yielding vapor to the extraction well. The primary compounds detected in the extracted vapor were benzene and naphthalene. Approximately 0.10 pound per day of volatiles was removed. Engineering controls, . including stringent air monitoring,will be used in the removal action at the redwood tank area. The redwood tank is part of the proposed project scope and will be addressed when remedial activities begin. Sources of Contamination:The source(s)of contamination are the result of a former manufactured gas plant that operated from 1913 to 1928. Site contaminants include PAHs, petroleum hydrocarbons and lead. Depth to Groundwater and Impact: Groundwater at the site is encountered at approximately 60 feet below ground surface and flows in a southerly direction. Low concentrations of petroleum hydrocarbons associated with a weathered fuel product were detected in groundwater beneath the site. The detections appear to be unrelated to former MGP operations due to the vertical separation between impacted soils and first encountered groundwater and the low migration potential of MGP related constituents. Groundwater- 4 DTSC 1332 VCP NOE June 21,2012 Office of Planning&Environmental Analysis