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i <br /> s <br /> Former Beacon Station No.12 474 7/25/2002 <br /> Stockton California Additional Deleniation Work Plan <br /> SITE DESCRIPTION AND BACKGROUND <br /> The site is an operating gasoline service station located on the southwestern corner of the <br /> intersection of East Main Street and Broadway Avenue in Stockton, California. Site <br /> �I <br /> facilities include a station building, two gasoline product dispenser islands located toward <br /> the northern property boundary, and three underground gasoline storage tanks (USTs) <br /> located toward the northeastern property boundary. Locations of these and other pertinent <br /> site features are shown on the Site Plan (Figure 2). Previous environmental work at the site <br /> was performed by Horizon, and others. The prey;ous work was summarized by Horizon in a <br /> PAR dated March 18, 2002. <br /> SCOPE OF WORK <br /> i <br /> The SJEHD indicated the submitted PAR was not complete since the vertical extent of <br /> hydrocarbons in groundwater is not delineated based on concentrations detected in <br /> monitoring well MW-12 screened from 84 to 89 feet below surface grade (bsg). <br /> Groundwater monitoring data and screended intervals of all wells are included in the <br /> attached Table 1. In addition, the SJEHD requested the CAP portion of the PAR be <br /> resubmitted with additional data to support remedial alternatives. The CAP will be revised <br /> after vertical delineation of hydrocarbons in groundwater. In the interim, Horizon proposes <br /> to initiate soil vapor extraction at the site for remediation of the vadose zone in an effort to <br /> begin removal of secondary source hydrocarbons prior to completion of the final CAP. It is <br /> our opinion that this secondary source of hydrocarbons is continuing to degrade the. <br /> groundwater quality beneath the.site and if interim remediation of this source is not initiated <br /> the threat to offsite receptors .and the`final cost for remediation will likely escalate. <br /> Additional groundwater delineation and interim soil remediation work phases are described <br /> below. <br /> C:\Projects\1474\13\1474-13.wp.doc <br /> 1474-13.wp 2 HORIZON ENVIRONMENTAL INC. <br />