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V <br /> David Chavier <br /> Bank of Stockton <br /> Page 2 <br /> In order to investigate the groundwater contamination evidenced during the <br /> excavation of contaminated soil, two monitoring wells(MW)were installed, MW2 and <br /> MW3. These wells were drilled to a total depth of 20 feet and were screened <br /> between 20 and 5 feet. The well which was installed by Union Ice and located on <br /> site was used as the third well to determine gradient and was designated a MW1. <br /> Soil contamination was evidenced during the installation of both MW2 and MW3 at <br /> 15 and 20 feet bgs. Contamination up to 33 ppb benzene was detected during the <br /> installation of MW2 and up to 1.9 ppb TPH-diesel during the installation of MW3. <br /> Groundwater contamination was evidenced in samples collected June/July 1992 and <br /> September 1992. Groundwater contamination has not been detected in samples <br /> collected December 1992 or March 1993. <br /> 1149 West Weber <br /> PHS/EHD indicated in correspondence dated August 27, 1992, January 23, June 24, <br /> and September 28, 1993 that residual contamination remaining at the conclusion of <br /> the re-excavation attempt, will require additional remediation, and that groundwater <br /> monitoring be continued. <br /> PHS/EHD discussed the following options that are available to the Bank of Stockton. <br /> Option 1 <br /> Long term quarterly groundwater monitoring, three years; monitoring 12 quarters. <br /> If no contaminants were detected, PHS/EHD indicated that a request for Central <br /> Valley Quality Control Board (CVRWQCB) concurrence for closure would be made. <br /> Option 2 <br /> No addition action. <br /> A request for closure would be made directly to the CVRWQCB without PHS/EHD <br /> recommendation for closure. PHS/EHD would forward a chronology to the <br /> CVRWQCB review. <br /> Option 3 <br /> Additional soil assessment in order to evaluate the necessity for additional soil <br /> remediation. A minimum of two additional soil borings sampled at 12.5, 15, 17.5, and <br /> 20 feet to define the extent of residual contamination. Additional groundwater <br /> monitoring to complete four (4) consecutive quarters of no detectible groundwater <br /> analyses will be necessary as was previously indicated by PHS/EHD. <br />