ARCHIVED REPORTS_VAPOR INTRUSION SURVEY - SOIL GAS SAMPLING REPORT

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Former Columbo/Toscana Bakery - 2 - 15 August 2008 ' 1444 S. Lincoln St., Stockton However, two grab groundwater samples collected from CPT-M8 reported the maximum grab groundwater concentrations for all but one constituent: • (47' to 52' bgs) - TPH as gasoline, 170,000 micrograms per Liter (ug/L); benzene, 25,000 ug/L; toluene, 28,000 ug/L; ethylbenzene, 3,600 ug/L; xylenes, 16,000 ug/L; and 1,2-dichlorethane, 550 ug/L; and • (77'-82' bgs) ethylene dibromide (EDB), 2.9 ug/L. Boring CPT-M7 (northeast of USTs arra, 79'-084' bgs) reported the maximum gra12 ' groundwater concentration for methyl tert-butyl ether (MTBE), 92 ug/L. The Site Conceptual Model (SCM) Schematic Diagram (enclosed Figure 14) depicts a single release of petroleum hydrocarbons from the USTs to soil and groundwater. However, the Report states that CPT/MIP and grab groundwater data show evidence for multiple groundwater plumes at the site, including one originating from the site USTs, and from ' possible offsite sources migrating onsite from the north and northeast (Texaco), the northwest (Chevron across Lincoln St.), and the southwest (Dolly Madison). The Reportaddresses risk from the onsite release and recommends a soil vapor survey. The Reportstates that ' corrective action for soil and groundwater "...cannot be accomplished without the cooperation of the neighboring properties that have contributed to this commingled plume." The Report also identifies several data gaps (hydraulic conductivity, vapor permeability, etc.). The Report ' concludes that vertical extent of groundwater pollution has not been established for boring locations CPT-M5 through CPT-M10. The Reportdoes not make a recommendation to proceed with remediation or to conduct additional investigations, instead it states that Regional ' Board staff acknowledged PSC's discussion efforts with neighboring USTs cleanup sites to join into a commingled plume account agreement and secure funding from the State Water Resources Control Board, UST Cleanup Fund (SWRCB USTCUF) and proposes the formation of a plan to address the groundwater plumes jointly with the neighboring sites. The Report concludes that PSC will provide monthly reports on the status of the talks with those neighboring sites and the formation of their "...commingled plume plan." ' Comments: ' 1) Regional Board staff have, and will continue to encourage Sara Lee to explore the Commingled Plume Account (CPA) with Chevron Environmental Management and Equilon Enterprises LLC (dba Shell, aka Texaco) as an avenue for reimbursement for your site, and are willing to assist you with any reasonable request to facilitate your goal of establishing a CPA. However, it has been Regional Board staff experience that the process for receiving a Letter of Commitment (LOC) from SWRCB USTCUF varies from ' months to years, depending on the timing of the signing of agreements between the businesses involved and upon the completeness of the group application to the CPA. Any request to delay all further investigation and remediation until the LOC is issued is denied. 2) Also, in a phone conversation with the Dolly Madison consultant, Regional Board staff was notified that the Dolly Madison site has declined to join the CPA agreement due to