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Summary Table Historic High Groundwater Concentrations, <br /> And Current(as of August 10,2009) Concentrations <br /> Contaminant B-1 B-2 B-3 MW-1 MW-2 MW-3 MW-1 MW-2 MW-3 <br /> Date Sampled 03/05/03 03/05/03 03/05/03 12/19/08 12/19/08 12/19/08 8/10/09 08/10/09 08/10/09 <br /> U A u /I U A U A U A U A U A U A U A <br /> TPHG <50 450 34,000 <50 <50 <50 <50 <50 <50 <br /> TPHD <50 8,100 750,000 <50 1,300 <50 <50 <50 <50 <br /> Benzene <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <br /> Toluene <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <br /> Eth (benzene <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <br /> Xylenes <0.5 10 1,600 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <br /> MTBE <0.5 1 <0.5 1 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 1 <0.5 <br /> Note: Ug/1-Micrograms per liter. * -Data from third quarter 2009. See Historic Data Table for compiled <br /> results for all wells. ND-None detected. TPHG-Total Petroleum Hydrocarbons, Gasoline, TPHD-Total <br /> Petroleum Hydrocarbons,Diesel. MTBE-Methyl-tert-Butyl-Ether. <br /> The soil contaminants have declined roughly 75% in six years as shown on the historic <br /> table. The change in dissolved groundwater contaminant mass concentration reduction <br /> is estimated at nearly 100% (see also Section 2.15 estimates below). The latest <br /> monitoring data shows that the interpreted area of the dissolved contaminants from the <br /> August 2009 data indicates that TPHG and Benzene are not present in groundwater. <br /> 2.12 Isoconcentration Maps Estimate of"zero line"of Dissolved Plume <br /> Groundwater flow is consistently northerly on the site, flowing from upgradient MW-1 <br /> toward downgradient wells MW-2 and 3 at the Delta property line. Isoconcentration <br /> maps for Total Petroleum Hydrocarbons as Gasoline and Diesel (TPHG, TPHD), <br /> Benzene, Methyl-tert-butyl-ether (MTBE) and 1,2-DCA have been prepared and <br /> submitted to the EHD in quarterly groundwater monitoring reports (see also Appendix B <br /> for Wright third quarter 2009 maps). The historic dissolved plume has been located <br /> between MW-3 and MW-2. The upgradient "zero line" of the plume has been interpreted <br /> at MW-1. The most recent monitoring data shows contaminants were not detected in any <br /> well. <br /> Contaminants historically observed in MW-2 and MW-3 were not present in the August <br /> 2009 sampling. TPHG and TPHD contaminants historically observed from borings and <br /> wells have declined from the levels observed in 2003. Benzene and MTBE have not been <br /> detected in any boring or well. <br /> / 2.13 Summary of Remedial Methods for Soil and Groundwater <br /> The source (two fuel underground tanks) was removed in 1985 by the City contractor. <br /> No other "active" remediation has been performed at this site. The decline in both soil <br /> and groundwater contaminants is attributed to natural petroleum degradation processes. <br /> Page 7 of 17 <br />