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(71San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> bonna Heron, REHS <br /> �--� y 600 East Main St eet <br /> u¢j; .,.-`i PROGRAM COORDINATORS <br /> Stockton, California 9!202-3029 <br /> Robert McClellon, REHS <br /> Jeff Carruesco,REHS, RDI <br /> cq • - �a�P Website: www.sjgov.O glehd Kasey Foley, REHS <br /> �rFaIR <br /> Phone: (209)468-3-120 <br /> Fax: (209)464-01 8 <br /> April 12, 2010 <br /> Mr. Denis L. Brown Mr. Ali Awnallah <br /> Shell Oil Products US 211 East Century Boulevard <br /> HSE — Environmental Services Lodi, California 95240 <br /> 20945 South Wilmington Avenue <br /> Carson, California 90810-1039 <br /> Subject: Former Shell Service Station <br /> 1313 East Charter Way <br /> Stockton, California 95205 <br /> Dear Mr. Brown: <br /> The San Joaquin County Environmental Health Dep rtment (EHD) has reviewed the analytical <br /> results for groundwater samples collected from mon toring well MW-1 following the termination <br /> of the interim groundwater extraction system in July 2009. During the third and fourth quarters <br /> 2009, concentrations of total petroleum hydrocarbons quantified as gasoline (TPH-g), and <br /> benzene, toluene, ethylbenzene, and total xylen s (BTEX) have decreased significantly. <br /> Concentrations of 1,2-dichloroethane (1,2-DCA) detected in groundwater collected from MW-6 <br /> have increased slightly from less than 0.50 micrograms per liter (Ng/L) to 8.4 pg/L (well below <br /> the high concentration of 50 pg/L reported in Janua 2005). Based on these two quarters of <br /> groundwater data, the EHD believes the petroleum hydrocarbon plume appears to be stable <br /> and declining; therefore, by email dated February 17, 2010, the EHD notified your consultant, <br /> Conestoga-Rovers and Associates (CRA), to submit a comprehensive site closure summary <br /> that includes an evaluation of the post remediation data, and addresses the vapor intrusion <br /> potential from the high concentrations of THP-g detected in soil samples collected from soil <br /> boring SB-1 [7,600 milligrams per kilogram (mg/kg) at approximately 21.5 feet below surface <br /> grade (bsg), and 6,400 mglkg at approximately 30.5 feet bsg]. <br /> Please contact Vicki McCartney at (209) 468-9852 r by email at vmccartneyCa?sicehd.com if <br /> you have any questions concerning this letter. <br /> Sincerely, <br /> Victoria L. McCartney, REHS Nuel C. Henderson, Jr., PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> c: Mr. Joseph W. Neely, PG, Conestoga-Rovers & Associates, 19449 Riverside Drive, Suite <br /> 230, Sonoma, California 95476 <br /> Mr. James L.L. Barton, PG, California Regional Water Quality Control Board Central <br /> Valley Region, 11020 Sun Center Drive, Suite 200, Rancho Cordova, California 95670 <br />