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PUBLI1 HEALTH SERVICES pQNiN <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION ai <br /> Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer <br /> .Ciq �P <br /> 445 N. San Joaquin Street • P. 0. Box 388 • Stockton, CA 95201-0388 �rFeR' <br /> 209/468-3420 <br /> PENNY SILZER COPY <br /> UNOCAL <br /> 2000 CROW CANYON PLACE #400 ' BGG` <br /> SAN RAMON CA 94583-1367 <br /> Re: Unocal Bulk #0788 SITE CODE: 1597 <br /> 8203 West Eleventh Street <br /> Tracy CA 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has <br /> completed review of the "Addendum to the Remedial Action Plan" dated December 30, 1994 and <br /> prepared by Pacific Environmental Group. PHS/EHD has the following comments for your <br /> consideration. <br /> The Addendum evaluated the remedial alternatives to address soil and groundwater contamination. <br /> These alternatives included the use of an intensive soil vapor extraction(SVE) program followed <br /> by air sparging; the use of a less intensive SVE program followed by air sparging; and the <br /> excavation of impacted soil. The selected alternative included an intensive SVE program <br /> followed by air sparging. <br /> The Addendum indicated that remediation monitoring would continue to evaluate progress. The <br /> Addendum also stated that institutional controls would be employed. One aspect of institutional <br /> control would be to restrict access to the contaminated groundwater by prohibiting the installation <br /> of drinking water wells at, or near, the site. PHS/EHD certainly agrees that Unocal would have <br /> authority to restrict the installation of wells on the property, but would not have authority to <br /> restrict installation on nearby properties. Please provide further information regarding the <br /> implementation of this institutional control as well as deed, zoning, or lease restrictions and the <br /> preparation of a migration control contingency plan. <br /> Also, the Addendum proposed that the SVE system and air sparging would be terminated when <br /> a "trendless data subset is identified for a time period of 3 months". While the statistical <br /> evaluation method is useful to estimate when asymptotic levels are achieved, prior to <br /> discontinuation of the operation of remediation systems, confirmation sampling will be required. <br /> PHS/EHD agrees that soil cleanup levels are site specific; however, please be informed that due <br /> to the shallow depth to groundwater, initial cleanup goals should be to background levels. In <br /> regards to groundwater cleanup goals, please note that the State Water Resources Control Board . <br /> adopted Resolution No. 68-16 which established an antidegradation policy for the protection of <br /> water quality in California which specifies that background levels should be maintained. <br /> .> Division of San Joaquin County Health Care Services <br />