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ENVIRONMENTAL HEALTH %EPARTMENT <br /> OPO.NIN O <br /> SAN JOAQUIN COUNTY <br /> a' 'ZA Donna K. Heran, R.E.H.S. Program Coordinators <br /> Director 304 East Weber Avenue,Third Floor Carl Bergman,R.E.H.S. <br /> Laurie A. Cotulla, R.E.H.S. Stockton,California 95202-2708 Mike Huggins,R.E.H.S.,R.D.I. <br /> c'9CfF`oad�P Assistant Director Telephone: (209)468-3420 Margaret Lagorio, R.E.H.S. <br /> Robert McClellon,R.E.H.S. <br /> Fax: (209)464-0138 Jeff Carruesco, R.E.H.S. <br /> Website:www.sjgov.org/ehd/ Kasey Foley,R.E.H.S. <br /> DARIN ROUSE <br /> CHEVRON ENVIRONMENTAL MANAGEMENT COMPANY <br /> 6001 BOLLINGER CANYON RD ROOM X2260 NOV n 9 2()06 <br /> SAN RAMON CA 94583 <br /> RE: Former Unocal #0187 <br /> 437 E. Miner Street <br /> Stockton, CA <br /> San Joaquin County Environmental Health Department (EHD) has reviewed the "Quarterly <br /> Groundwater Monitoring Report—Second Quarter 2006" dated July 17, 2006, prepared by <br /> ENSR for the above referenced site and provides the following comments on the <br /> recommendations in the report as well as current site investigative work. <br /> ENSR recommended in the quarterly report that the ozone sparge system be decommissioned. <br /> EHD is aware that there have been problems with operation of the ozone system. The <br /> concentrations of contaminants in the groundwater samples from monitoring well U3 indicate <br /> that the groundwater in that area at the interval being monitored by U3 (screened 30-55 feet) <br /> requires remediation. EHD recommends that evaluation of the installation of ozone injection <br /> points in that area and interval be evaluated to focus the active remediation on the remaining <br /> contaminant plume. The sparge wells located closest to U3 may not be appropriately placed. <br /> The current investigation of soil gas vapors may address the concerns for vapor intrusion into <br /> future buildings at the site as well as buildings adjacent to the site but an evaluation of the <br /> remaining soil contamination leaching into the groundwater still must be performed. <br /> If you have any questions contact me at (209) 468-3449. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> � <br /> --K A V <br /> Margaret Lagorio, REHS <br /> Program Coordinator Unit IV <br /> c: Jim Barton —CVRWQCB <br /> David Irey— SJCADA <br /> Nicole Pagano- ENSR <br />