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u %.VV V fuel additives [1,2-dibromoethane (1,2 -DBA) and 1,2-dichloroethane (1,2 -DCA)] were not detected in any of the soil samples. 'Grab groundwater samples collected from the borings contained TPH-g, BTEX, DIPE, and 1,2 -DCA. TPH-g was detected at concentrations up to 8,400 micrograms per liter (µg/L) at 60 feet bgs. PSC reported the results from the investigation in the June 2004 Site Investigation Report. At the time of the 2004 subsurface investigation, groundwater samples were also collected from '-' all onsite monitoring wells and two nearby private wells. This monitoring event indicated that the lateral extent of impacted groundwater was largely contained within the Earthgrains property boundaries. Based on the findings of this investigation, PSC recommended V performing one more groundwater monitoring event, and then preparing a report which would propose either site closure or additional remedial work. SJCEHD approved the recommendations in a letter dated September 24,E 04 jV0 6 14 D do eJ 4e- Vol,,eX; ,447f.'4 /f JAS i n is✓- 971 / ze"C'� l V Groundwater Monitoring (1987 through 2006) A quarterly monitoring report prepared in October 2004 by PSC included calculations for residual mass of benzene and TPH-g in groundwater. PSC calculated the total mass of benzene '-' in groundwater to be 1.8 kilograms (kg) and calculated the total mass of TPH-g in groundwater to be 70.7 kg. V The SJCEHD approved modifications to the site monitoring program in a meeting on November 10, 2005,�and in a letter dated December 13, 2005. The modifications included sampling well MW -10 on an annual basis and discontinuing sampling of wells MW -3, MW -6, SP -3, SP -4, SP -5, and SP -6 beyond the fourth quarter 2005 event. '-� Recent data indicate that the overall groundwater flow direction is generally to the east beneath the site at a gradient of approximately 0.003 foot per foot (Figure 3). TPH-g, BTEX, some fuel oxygenates, and 1,2 -DCA have been detected in groundwater samples collected during recent monitoring events. Historical soil and groundwater data are presented in Tables 1 and 2, respectively. Analytical data for groundwater samples collected in April 2006 are presented on Figure 4. Isoconcentration contours for benzene in groundwater in April 2006 are presented on Figure 5. Isoconcentration contours for TPH-g in groundwater in April 2006 are presented on Figure 6. V- 3.0 PROPOSED SCOPE OF SERVICES The objectives of this proposed subsurface investigation are to: 1) identify the source or �. sources of residual petroleum hydrocarbon contamination and 2) further characterize the degree and extent of petroleum hydrocarbons in soil and groundwater in the vicinity of three former underground storage tank (UST) and two oil/water separator systems at the site. The results of 8 LM