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--------o=> t}—CLEARWATER <br /> • G R O U P, I N C <br /> Environmental Services <br /> GROUNDWATER MONITORING REPORT <br /> THIRD QUARTER 1998 <br /> Ruiz Grocery, <br /> 4491 West Durham Ferry Road,Tracy,CA <br /> September 17, 1998 <br /> BACKGROUND <br /> Two gasoline USTs and dispensers were removed from the site in 1988 Seven monitoring wells (MW-i through <br /> MW-7), one groundwater recovery well(RW-1),four soil vapor extraction wells(VW-1 through VW-4),and two air <br /> sparge wells (SW-1 and SW-2) have been installed at the site A domestic well (DW), screened in a deeper water <br /> bearing zone, has also been installed at the site The extent of soil and water contamination has been delineated <br /> Pilot testing has been completed and a remedial action plan prepared based on results <br /> The work presented here was conducted as part of scheduled quarterly groundwater monitoring as requested by the San <br /> Joaquin County Public Health Services/Environmental Health Division (SJCPHS/EHD) All work was conducted <br /> in accordance with Clearwater's Field Procedures attached <br /> GROUNDWATER MONITORING FIELD ACTIVITIES <br /> Date of field activities 8/20/98 <br /> Wells gauged/sampled MW-1, MW- 3 through MW-6 <br /> Analytes tested TPHg,BTEX,Fuel Oxygenates <br /> . Analytical methods EPA Methods 8015 (modified), 8020,and 8240 <br /> Laboratory Entech Analytical Labs, Inc , of Sunnyvale, CA <br /> Remarks All wells were resurveyed after some casings were altered due to system <br /> installation MW-7 was not sampled due to hardpacked gravel cover concealing <br /> the well <br /> GROUNDWATER MONITORING RESULTS <br /> Depth to water 11 68 feet(MW-3)to 13 28 feet(MW-4)below ground surface (bgs) <br /> Flow direction/gradient Southwest, at 0 0026 ft/ft <br /> SPH - wells/thicknesses Not detected for any well <br /> TPHg concentration range <50 µg/L (DW, MW-3, 4, 5, and 6 ) to 69,000 gg/L (MW-1) <br /> Benzene concentration range <0 5 gg/L (DW, MW-3, 4, 5, and 6) to 210 gg/L (MW-1) <br /> MTBE concentration range <5 0 �tg/ (DW, MW-3, 4, and 6)to 11 lig/L (MW-5) <br /> Fuel Oxygenates <5 0 µg/L / <20 gg/L (MW-1, MW-3 through MW-6) <br /> Remarks Hydrocarbon contamination was not detected in the domestic <br /> well <br /> PROJECT STATUS <br /> On behalf of Ruiz Grocery,Clearwater has received cost pre-approval (dated January 21, 1998)from the Underground <br /> Storage Tank Clean-up Fund for tasks associated with installation, start-up, operation and maintenance of the air <br /> sparging / vapor extraction remediation system, and for four quarters of quarterly groundwater monitoring and <br /> reporting Remediation system installation is currently being implemented and the system is expected to be <br /> operational by the end of September 1998 Groundwater analytical data over the past two monitoring events indicate <br /> that MTBE is the only oxygenate of concern at the site Accordingly, Clearwater reccomends reverting the <br /> groundwater sample analytical suite to only TPHg, BTEX, and MTBE by EPA methods 8015/8020 (modified), for <br /> future monitoring events <br /> 520 Third Street,Suite 104 o Oakland,Califomia 94607 o Telephone 510-893-5160 o Fax 510-893-5947 <br />