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San Joaquin County DIRECTOR <br /> PQ i N Donna Heran,REHS <br /> ,o Environmental Health Department ASSISTANT DIRECTOR <br /> 600 East Main Street Laurie Cotulla,REHS <br /> a: 1, , -� <br /> �. Stockton, California 95202-3029 <br /> PROGRAM COORDINATORS <br /> •'•' • Carl Borgman,REHS <br /> - Website: www.s OV.or /ehd Mike Huggins,REHS, RDI <br /> cgCjFOR�`P Ig 9 Margaret Lagorio,REHS <br /> Phone: (209)468-3420 Robert McClellon,REHS <br /> Fax: (209)464-0138 Jeff Carruesco,REHS,RDI <br /> TERRENCE FOX Kasey Fol REHS <br /> CALTRANS DISTRICT 6 AUG 16 200) <br /> 2015 E SHIELDS AVE STE 100 <br /> FRESNO CA 93726 <br /> RE: Stockton Yard Maintenance Station SITE CODE: 10193 <br /> 1604 B Street <br /> Stockton CA 95201 <br /> San Joaquin County Environmental Health Department(SJC/EHD) has reviewed Groundwater <br /> Monitoring Report—Second Quarter 2007(Report)dated July 31, 2007 submitted on your behalf <br /> by Geocon Consultants, Inc. (Geocon)and has the following comments. <br /> The Report documents routine quarterly groundwater monitoring and sampling activities that were <br /> performed at this site in May 2007. Cal Trans has requested comment regarding requirements <br /> for closure of this site. The site can expect case closure after the petroleum hydrocarbon <br /> contamination resulting from the unauthorized release from underground storage tanks has been <br /> remediated. The site has been undergoing investigation and monitoring of the contamination <br /> since approximately 1992. The core of the plume is located near the former underground storage <br /> tanks and dispenser island areas. Over the history of the site the groundwater elevation has <br /> fluctuated; currently only two wells onsite are screened across the top of the water table, VW-1 <br /> and VW-2. These two wells continue to show the highest concentrations of contamination. <br /> It is the understanding of SJC/EHD that an air sparge/soil vapor extraction (AS/SVE)system <br /> designed by Brown &Caldwell in 2003 was going to be installed and remediation by AS/SVE <br /> would be initiated at this site. The equipment to do this is currently in operation at Cal Trans <br /> Shop 10, located at 1603 B Street, Stockton. When the remediation is complete at Shop 10, the <br /> remediation equipment will be transferred to the Maintenance Station for utilization there. <br /> While the plume at this site may appear stable, the concentrations of contaminants are still too <br /> high for it to be considered for regulatory closure. As noted before, all monitoring well screens <br /> are currently submerged, which means that the wells are not providing information on the <br /> contaminant concentrations in the shallow plume. Additionally, routine monitoring and sampling <br /> of this site has been intermittent, despite regulatory directives to provide quarterly data. Routine <br /> quarterly groundwater monitoring and sampling must continue at this site until directed otherwise <br /> by this agency, and must include analysis for ethylene dibromide and 1,2-dichloroethane. <br /> If you have any questions please call Lori Duncan at(209)468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> 0�-- <br /> Lori Duncan, Senior REHS Nuel C. Henderson, Jr., PG <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc: James Barton, PG, CVRWQCB <br /> Rebecca Silva, Geocon <br />