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Former Beacon Station No. 12474 <br /> Stockton.California October 8,2003 <br /> carter! Groundwater Monitorin Re art <br /> California Department of Health Services-certified analytical laboratory (ELAP No. 2236) <br /> located in Davis, California. The samples were analyzed for total petroleum hydrocarbons <br /> as gasoline (TPHg), the volatile aromatic compounds benzene, toluene, ethylbenzene and <br /> total xylenes (BTEX). and the fuel oxygenate methyl-t-butyl ether (MTBE) by <br /> Environmental Protection Agency (EPA) Method 8260B. <br /> Groundwater Monitoring Results <br /> Depth-to-groundwater measurements were subtracted from the surveyed TOC elevations to <br /> calculate groundwater elevations. Groundwater elevation data, as summarized in Table 1, <br /> were used to construct the groundwater elevation contour map shown on Figure 2. The <br /> groundwater flow direction from the dispenser island area varied from northeastward to <br /> eastward and southward under an average gradient of approximately 0.002 . <br /> Groundwater analytical results are summarized in Table 1. Benzene concentration data from <br /> this sampling event were used to construct the benzene isoconcentration map shown on <br /> Figure 3. Analytical reports and chain-of-custody documents are contained in Attachment <br /> C. Historical groundwater Ievel and analytical data collected prior to 1998 are summarized <br /> in Tables 1 and 2 in Attachment D. <br /> GeoTracker Electronic Data Deliverables <br /> The analytical electronic data deliverable (EDD) is uploaded by Kif£ The groundwater well <br /> measurement file EDD (GEO_WELL) for this quarterly monitoring event was uploaded by <br /> Horizon. The GEO_WELL upload confirmation sheet for this quarter is contained in <br /> Attachment E. <br /> Recommendations <br /> Horizon has implemented the quarterly monitoring modifications proposed in the fourth <br /> quarter 2002 quarterly monitoring report. On August 27 and 28, 2003, Horizon conducted <br /> an additional groundwater investigation for the purpose of evaluating hydrogeologic <br /> conditions, and the placement and construction of additional monitoring wells. The report <br /> of the investigation, including recommendations for siting additional monitoring wells, is in <br /> preparation. Installation of an interim groundwater remediation system was initiated in <br /> September. <br /> Report Distribution <br /> We recommend a copy of this report be forwarded to: <br /> Mr. Gordon Boggs Mr. Franey Naderzad <br /> CRWQCB - Central Valley Region 748 Pollard Road <br /> 3443 Routier Road, Suite A Los Gatos, California 95032 <br /> Sacramento, California 95827-3098 <br /> 474gmrQ303.doc <br /> Project No. 1474.46 2 HORIZON ENVIRONMENTAL INC. <br />