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• 0 <br /> San Joaquin County <br /> 4N Environmental Health Department DIRECTOR <br /> P —�' Donna Heran, REHS <br /> 600 East Main Street PROGRAM COORDINATORS <br /> �7 Stockton, California 95202-3029 Robert McClellon,REHS <br /> Jeff Carruesco,REHS,RDI <br /> Kasey Foley,REHS <br /> Website: www.sjgov.org/ehd Linda Turkatte,REHS <br /> 9O ii -1 . Phone: (209)468-3420 <br /> Fax: (209)464-0138 <br /> May 5, 2011 <br /> Ted Moise <br /> Conoco Phillips Company <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> Subject: Former UNOCAL#6981 <br /> 4707 Pacific Avenue <br /> Stockton, CA 95207 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Quarterly Status Summary Report — First Quarter 2011 (Report), dated March 16, <br /> 2011, submitted on your behalf by Stantec Consulting Corporation (Stantec) and has <br /> the following comments. <br /> The Report documents a routine groundwater monitoring and sampling event that was <br /> conducted in January 2011. This event reports the first time well VW-2 was sampled <br /> since June 2000, following redevelopment of the well in December 2010, and removal <br /> of approximately 15 feet o4.sediment that had been occluding the screen interval. <br /> Laboratory analytical results reported significant concentrations of petroleum <br /> hy3rocarbon contamination in VW-2. <br /> In Results of Hydrogeologic Modeling dated December 18, 2009, Stantec reported the <br /> results of using the FLOWPATH II groundwater flow and transport model which <br /> estimated that the total petroleum hydrocarbon as gasoline concentrations reported at <br /> that time in well VW-7 would degrade to <100 micrograms per liter (ug/1) onsite and <br /> <50 pg/I offsite by May 2018, and will have migrated approximately 100 feet <br /> downgradient offsite, under Pacific Avenue. The contaminant concentrations recently <br /> reported in well VW-2, however, are significantly higher than those reported in VW-7. <br /> In June 2010, one confirmation soil boring and four soil vapor probes were installed at <br /> the site. Laboratory analytical results from the soil and vapor samples collected from <br /> these probes all passed the environmental screening levels established by San <br /> Francisco Bay Regional Water Quality Control Board, as reported in Stantec's <br /> Additional Assessment Report dated August 10, 2010, and Letter Addendum to <br /> Stantec's Additional Assessment Report dated September 24, 2010. Additionally, <br /> Stantec submitted Sensitive Receptor Survey dated December 14, 2009. <br /> In order to continue to work this site towards regulatory closure, please prepare a <br /> FLOWPATH II flow and transport model using data from well VW-2. If favorable results <br /> are obtained, please submit the results in a Closure Report, addressing all <br />