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However, the lack of subsurface groundwater and the presence of compacted soils made this alterative impractical. In order to foster microbial growth and activity,water and air would have had to be injected in the affected area. Excavation was deemed to provide the highest level of effectiveness in terms of protection of the environment and public risk,while being the most implementable of the remedies considered. 2.3.2 Summary of 2005 Soil Excavation Prior to commencement of excavation activities,four groundwater monitoring wells(MW-1 through MW-4) were abandoned by over drilling between June 14 and 15, 2005. Between June and December 2005,approximately 10,400 tons of soil were excavated from the Site. The maximum depth of the excavation was 8o fbg and the diameter of the excavation was approximately 200 feet(CLS Environmental Services,Inc. 20o6). During excavation activities,a total of 52 confirmation soil samples were collected between August 3o and October 13, 2005 for analysis to assess to what extent soil should be excavated. Only one of the 39 confirmation samples collected from residual soils left in place was reported to contain elevated concentrations of TPH-g and TPH-d.Soil sample WWCSF-78, collected at the west wall floor of the excavation at a depth of 78 fbg,contained 6,000 mg/kg TPH-d and 2,800 mg/kg TPH-g. A grab groundwater sample(W-1)was collected from the excavation on July 13, 2005.This grab sample was collected from water that had percolated into the bottom of the open excavation within the immediate vicinity of impacted soils being staged for removal.TPH-d was detected in sample W-1 at a concentration 4,46o µg/L. However,the elevated concentration of TPH-g in sample W-1 was inconsistent with historical data and was likely a result of mixing with impacted soils within the excavation that were being staged for removal(CLS Environmental Services, Inc., 20o6). 3.0 SUMMARY OF AVAILABLE DATA 3.1 Hydrocarbon-Impacted Soil TPH-g,TPH-d,ethylbenzene and total xylenes have been reported in soil samples collected at the Site. A summary of soil analytical results is provided in Table 2.The distribution of hydrocarbons in deep soils and the reported concentrations are shown on Figure 6. The area of the Site which was excavated in 2005 included the vast majority of previously investigated areas. All locations sampled for soil prior to the excavation activities in 2005 (inclusive of the UST removal confirmation samples,borings B-1 through B-5 advanced in 1999, borings B-1 through B-6 advanced in 2000,wells MW-1 through MW-3 installed in 2000,well MW-4 installed in 2001,and borings B-7 through B-11 advanced in 2004)have been subsequently excavated to the total depth analyzed with the exception of B-6. Results from all soil and grab groundwater samples from boring B-6,installed in 2000,analyzed for TPH-g, TPH-d, BTEX constituents,and five oxygenates were below their respective laboratory limits. During the June 2008 additional soil and groundwater investigation,TRC completed six(6) additional borings located within the vicinity of the former diesel UST on the western side of the Site.TPH-d was detected in three of the twelve soil samples analyzed at a maximum concentration of 410 milligrams per kilogram(mg/kg)in boring B-17 collected at a depth of 50 4