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Former Beacon station No. 12474 December l7,2003 <br /> Stockton California Quarterly Groundwater Monitoring Report <br /> total petroleum hydrocarbons as gasoline (TPHg), the volatile aromatic compounds benzene, <br /> toluene, ethylbenzene and total xylenes (BTEX), and the fuel oxygenate methyl-t-butyl ether <br /> (MTBE) by Environmental Protection Agency (EPA) Method 826013. <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 southward to <br /> southeastward under an average gradient of less than 0.001. <br /> Groundwater analytical results are summarized in Table 1. Analytical reports and chain-of- <br /> custody document are contained in Attachment C. Historical groundwater level and <br /> analytical data collected prior to 1998 are summarized in Tables 1 and 2 in Attachment D. <br /> GeoTracker Electronic Data Deliverables <br /> The analytical electronic data deliverable (EDD) is uploaded by Kiff. 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 draft <br /> report of the investigation, including recommendations for siting additional monitoring <br /> wells, is in Ultramar review. Installation of an interim groundwater remediation system was <br /> initiated in September. Ultramar is in the process of securing electrical and natural gas <br /> utilities from PG&E for operation of the remediation system. <br /> �1 <br /> 474gmrQ403.doc <br /> Project No. 1474.46 2 HORIZON ENVIRONMENTAL INC. <br />