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i - <br /> San Joaquin County <br /> "' . Environmental Health Department DIRECTOR <br /> Donna Heran, REHS <br /> r ` 600 East Main Street <br /> Stockton , California 95202 -3029 PROGRAM COORDINATORS <br /> � :. Robert McClelion, RENS <br /> Jeff Carruesco, REHS, RDI <br /> • �q • .�== ° Website: wwwsjgov. org/ehd KaseyFoley, REHs <br /> FOR <br /> Phone: (209) 468-3420 <br /> Fax: (209) 464-0138 <br /> February 8, 2010 <br /> Ms . Stephanie McKenna Mr, Mark Springs <br /> Chevron Environmental Management Company 3535 Windham Circle <br /> 6111 Bollinger Canyon Road, Room 3652 Stockton , CA 95209 <br /> San Ramon , CA 94583 <br /> Subject: Chevron #9-4054 LOP Case#: 1780 <br /> 2103 Country Club Blvd . AP#: 123-080-29 <br /> Stockton , CA 95204 Global ID#: T0607700063 <br /> The San Joaquin County Environmental Health Department (EHD ) has reviewed First Semiannual <br /> 2009 Groundwater Monitoring Report (GMR), dated December 17, 2009 , submitted by your <br /> consultant Arcadis . The GMR covers the groundwater sampling event conducted at the site on <br /> May 11 , 2009 . Discussions included in the report stated that the current well array delineates the <br /> plume and the current remedial activity is monitored natural attenuation . <br /> The EHD has reviewed the groundwater data for the site and does not concur with the statement <br /> that the current well array delineates the groundwater contamination plume . Although data from <br /> offsite monitoring wells MW-9C, MW-9D and MW- 12C and MW- 12D show a downward trend in <br /> dissolved petroleum hydrocarbon concentrations over time, monitoring well MW-9B is trending <br /> upwards . Groundwater data from monitoring well MW-12B appears to be stabilizing after three <br /> sampling events at just above 2, 000 ug/1 for total petroleum hydrocarbons as gasoline (TPHg). <br /> Monitoring well MW-12B is the most down gradient well for this site and the EHD does not consider <br /> the groundwater plume in the B zone as laterally defined . Additional offsite lateral B zone <br /> groundwater plume delineation is required . <br /> Elevate concen ra Ions of als osos vve p� euro hydrocarbons are still present in the groundwater <br /> samples collected from onsite monitoring wells . The EHD has concluded that monitored natural <br /> attenuation is not effectively reducing the mass of contamination that is apparently continuing to <br /> degrade the groundwater. Chevron must take steps to actively clean up the site. Since the <br /> contaminant plume is not completely defined , the EHD can only approve interim remedial actions at <br /> the site . Please provide a proposal for interim remedial action that is based on a comparative <br /> evaluation of multiple remedial alternatives for feasibility and cost-effectiveness. This proposal and <br /> a work plan for the continued B zone investigation are due on Geotracker by March 19, 2010. <br /> If you h e any questio p ase contact Michael Infurna at (209) 468-3454 . <br /> Michael J . Infurna Jr., EHS Nuel C . Henderson Jr. , PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> c: James L. L. Barton , CVRWQCB, Underground Storage Tank Unit, 11020 Sun Center Drive <br /> #200, Rancho Cordova, CA 95670-6114 <br /> Mark Owens, SWRCB, Division of Clean Water Programs , Underground Storage Tank <br /> Program , PO Box 944212, Sacramento, CA 94244-2120 <br /> David Evans, Arcadis, 950 Glenn Drive #125, Folsom , CA 95630 <br /> l <br />