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�= `�`H SERVICESUBLI� HEAL <br /> SAN JOAQUIN COUNTY a �� <br /> p: :t <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue,Third Floor • Stockton, CA 95202 <br /> 2091468-3420 <br /> PAUL SUPPLE JAN 17 2002 <br /> ATLANTIC RICHFIELD COMPANY <br /> P O BOX 6549 <br /> MORAGA CA 94570 <br /> RE: ARCO # 5469 <br /> 130 S. Wilson Way SITE CODE: 0710 <br /> Stockton CA 95205 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed the <br /> Monitoring Report Third Quarter 2001, dated November 2, 2001 submitted by Delta <br /> Environmental Consultants Inc. on your behalf for the above referenced site and has <br /> the following comments. <br /> The report details the results of the quarterly groundwater monitoring and sampling <br /> event that took place at this site on September 14, 2001 . Results of the sample <br /> analyses show methyl-tertiary butyl ether (MtBE) was detected in groundwater <br /> samples from wells MW-4 at 24,000 ug/i, MW-5 at 16,000 ug/l, MW-6 at 22,000 ug/I, <br /> MW-8 at 7,500 ug/l and MW-10 at 44 ug/I. Total Petroleum Hydrocarbons as <br /> gasoline (TPHg) at 2,000 ug/I and benzene at 980 ug/I were detected in water <br /> samples from MW-4. Di-isopropyl ether (DIPE) at 3.0 ug/l and 1,2-Dichloroethane <br /> (1,2-DCA) at 13 ug/I were detected in water samples from MW-9. <br /> According to Step 3 within the State Water Resources Control Board (SWRCB) <br /> Guidelines for Investigation and Cleanup of MtBE and other Oxygenates final draft <br /> dated 30 March 2000, sites with persistent concentrations of MtBE over 10,000 ppb <br /> should perform interim remediation to reduce the concentrations and mass before the <br /> plume can spread. MtBE has been detected in water samples from MW-5 at <br /> concentrations above 10,000 ppb since December 2000, so interim remediation <br /> should be proposed for this site. <br /> Remedial options of vapor extraction, air sparging, groundwater extraction, and <br /> ozone injection should all be evaluated for this site. A work plan to install any wells <br /> necessary to evaluate these alternatives along with a plan for performing tests for <br /> these alternatives should be submitted to EHD by March 4, 2002. In addition, the <br /> lateral and vertical extent of the soil and groundwater contamination must continue to <br /> be investigated. The work plan submitted should include installation of additional <br /> monitoring wells that will define the extent of the contamination at and emanating <br /> from this site. <br /> A Division of San Joaquin County Health Care Services <br />