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^ 1149 <br /> San Joaquin County DIRECTOR <br /> Donna Heran,REHS <br /> OPQ'U�N:C Environmental Health Department ASSISTANT DIRECTOR <br /> Laurie Cotulla,REHS <br /> r.' z 600 East Main Street <br /> < Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> ` Carl Borgman,REHS <br /> Mike Huggins,REHS,RDI <br /> iFoaa•v Website: www.Sjgov.Org/ehd Margaret Lagorio,REHS <br /> Phone: (209)468-3420 Robert McClelion,REHS <br /> Fax: (209)464-0138 Jeff Carruesco,REHS,RDI <br /> 09 April 2008 Kasey Foley,REHS <br /> Messrs. Robert Trommer, CHG, and Kirk Larson, PG <br /> State Water Resources Control Board <br /> Division of Financial Assistance <br /> 1001 1 Street <br /> Sacramento CA 95814 <br /> Subject: Preliminary Five-Year Review for Claim Number 2612 <br /> 110 Filbert Street N <br /> Stockton, California <br /> San Joaquin County Environmental Health Department (EHD) has received and reviewed <br /> Preliminary 5-Year Review Summary Report for Claim Number 2612; Site Address. 110 Filbert <br /> Street N, Stockton, CA (5-yr review) dated 24 March 2008, in which you recommend site <br /> closure consideration. Among the criteria cited to justify the site closure recommendation was <br /> the following conclusion: <br /> • The plume size is stable and sufficiently delineated in lateral and vertical extent and <br /> contaminant concentrations detected in groundwater show a decreasing trend with time <br /> Review of the contaminant concentration trends appears to show that the site is approaching <br /> site closure criteria, however the EHD has concerns regarding several aspects of the site <br /> characterization and has issued directives to address these particular issues, to wit. <br /> • There Is no current estimate of the residual sorbed contaminant mass in either the <br /> vadose zone or the saturated zone, <br /> • Groundwater elevation had risen approximately 10 feet between the first groundwater <br /> monitoring event (September 1991) and initiation of the first soil vapor extraction (SVE) <br /> and insitu air sparging (IAS) system, which operated from February 1995 to November <br /> 1995), removing approximately 10 vertical feet of presumably impacted soil from the <br /> direct influence of the SVE system during its operation; <br /> • Groundwater elevation rose an additional 13 feet between cessation of the first SVE/IAS <br /> system (November 1995) and initiation of the second SVE/IAS operation (May 2003), <br /> removing 13 more vertical feet of soil from the direct influence of the SVE system, <br /> • Groundwater elevation has risen approximately 30 feet since monitoring began in 1991, <br /> rising above the initial monitoring wells screen intervals in March 1995 when the first <br /> SVE/IAS system went into operation, and has been above the screen intervals ever <br /> since, obfuscating whether the reduction of dissolved contaminant concentrations was <br /> primarily due to either SVE operation or water rising significantly above the well <br /> screens, <br /> • Groundwater is currently 15 to 20 feet above the tops of the screens of the shallowest <br /> monitoring wells, therefore 'first' groundwater is not monitored or characterized, <br /> Site 51 Preliminary Five-Year Review Continent Letter 0408.doc <br />