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1 <br /> WORKPLAN ADDENDUM <br /> . ARCO Mini-Mart <br /> 4511 Pacific Avenue <br /> Stockton, CA <br /> 1. 0 BACKGROUND <br /> Seven soil borings have been drilled since October 1992 to <br /> investigate the extent of hydrocarbon contamination at this site. <br /> Three of these were completed as groundwater monitoring wells, and <br /> one was completed as a vadose-zone remediation well. Subsequently, <br /> groundwater conditions have been monitored quarterly. The results <br /> of these investigations have been reported in GeoAuditIs <br /> Preliminary Investigation and Evaluation Report (November 1992) and <br /> Quarterly Reports (April, June, and September 1993) . Following the <br /> September reporting, a meeting was held with Mrs. Diane Hinson of <br /> PH,S/EHD �o discuss future work. Among the items discussed was a <br /> vapor extraction test of the vadose-zone remedial well to gather <br /> data on soil permeability and radius of influence of remedial wells <br /> in the impacted zone. The purpose of this addendum is to briefly <br /> outline the methods and ob3ectives of the test. <br /> 2 . 0 OBJECTIVES <br /> The principal objective of this vapor extraction test is to obtain <br /> information on soil properties in the area of the contamination <br /> plume Of particular interest as the relative permeability of the <br /> soil to air and hydrocarbon vapors, so that the effective radius of <br /> remedial wells can be estimated. Because both vapor extraction and <br /> bioremediation are most effective in loose, unconsolidated, porous <br /> and permeable soil, the radius of influence of either method is <br /> greater an sandy soil than in clayey soil. <br /> The second ob)ectave of the test is to provide information about <br /> the concentrations at which hydrocarbon vapors can be extracted <br /> from the vadose zone This information is useful in estimating the <br /> time required to remove the contamination. <br /> 3. 0 PROCEDURES <br /> GeoAudat nas performed two an-situ vapor extraction pro)ects in the <br /> past three years. One of these sates as located in Stockton . and <br /> was permitted through the San Joaquin County APCD. Both projects <br /> utilized an Environmental Techniques Vaclean 1000 vapor extraction <br /> system. These projects have successfully removed the subsurface <br /> hydrocarbons with no adverse impact to local air quality. <br /> For this test, GeoAudit proposes to utilize the Vaclean 1000 <br /> system, which consists of a Ford Motors 300 cu. in. internal <br /> combustion engine and a vacuum blower (Roots model #865-105--120) . <br /> The unit will be temporarily connected to remedial well VW-1 with <br />