SITE INFORMATION AND CORRESPONDENCE

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Silgan Containers Corporation 1815 Navy Drive, Stockton - 2 - 29 November 2001 unauthorized release of petroleum hydrocarbons and solvents at your site has degraded the groundwater, and you are required to clean up the groundwater to the extent technically and economically feasible. In the 13 March 1990 Phase II Site Characterization-P.A.R. submitted by Thorne Environmental (Thorne), four remedial options (excavation and disposal, excavation and on-site biotreatment, vapor extraction of volatile hydrocarbons, and no action) were proposed for site cleanup. Thorne recommended vapor extraction as the most viable alternative; however, steps to remediate the site have not been implemented to date. Due to the regional increase in the water table, and the unknown extent of groundwater contamination, the recommended soil vapor extraction would not be adequate to address soil and groundwater contamination today. Therefore, you are directed to define the extent of groundwater contamination, and submit an updated Problem Assessment Report (PAR). The PAR must include isoconcentration maps to show the extent of contamination, and a feasibility study to evaluate at least three cleanup alternatives addressing residual hydrocarbon and solvent contamination remaining in soil and groundwater at this site. A well receptor survey was included in the 8 January 1988 Soil and Ground Water Investigation submitted by California Geological, Incorporated, and this survey must also be updated as part of the PAR. All work must be performed according to the Tri-Regional Recommendations for Preliminary Investigation and Evaluation of Underground Storage Tank Sites, and permits required by State and Local agencies. You are also directed to continue quarterly monitoring and reporting until this site is closed and you receive a no further action required letter from Board staff. Wells GW-1, GW-2, and MW-1 must be sampled quarterly, and all six wells must be sampled annually. All wells must be sampled and analyzed for total petroleum hydrocarbons by EPA Method 8015, and for volatile organic compounds by EPA Method 8260B. Fuel oxygenates have been non-detect for the last two sampling events, and as such the reporting for fuel oxygenates may be discontinued. All wells must be purged a minimum of three casing volumes prior to sample collection, and groundwater parameters including temperature, pH, electrical conductivity, turbidity, color, and odor must be recorded in purge data sheets. The purge data sheets must be submitted with all future quarterly monitoring reports. To allow a simple review of the data,please include groundwater data for all six monitoring wells and report all detected constituents in a table. Please group the data by the well sampled instead of the date sampled. Reporting for petroleum hydrocarbon constituents (TPHmo and BTEX) should be grouped separately and not inter-mixed with the volatile organic compounds (TCE, DCE, and vinyl chloride). As previously discussed with Caporale, GW-1 should be properly destroyed and replaced due to the deteriorating well screen identified during the last two sampling events. I suggest that the replacement well be placed outside the former tank pit excavation and completed to monitor first water(e.g. a 15-foot screen interval placed with five feet above, and ten feet below the water table).