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CT"logecal recwcs 11K Page 4 George's Service Soil Excavation Report Project No 425 3 January 28, 2002 ' On October 30 and 31, 2001 Del-Tech Geotechnical Support Services (Del-Tech) and Fagundes & Son Inc personnel mobilized to the site to properly dispose of the stockpiled ' soil The soil was taken to Forward Incorporated, 9999 South Austin Road, Manteca, California, for disposal ❑ October 30, 2001 — Seventeen truckloads of soil totaling 287 39 Cubic Yards ❑ October 31, 2001 —Twelve truckloads of soil totaling 208 58 Cubic Yards ' A total of 495 97 Cubic Yards (541,064 Kg) of soil was removed from the site with an average TPH-gasoline of 4,114 mg/Kg This brings the amount of TPH-gasoline removed to approximately 4,897 pounds The weigh tags from Forward Landfill are included in Appendix C ' Mass Estimate Calculation A soil mass estimate calculation was prepared to determine the amount of soil contamination present prior to the excavation The calculations show that approximately 11,630 pounds (1,900 gallons) of gasoline was piesent in the soil ' The calculations were prepared as follows 1 The soil plume was defined by soil sample analysis from a combination of soil borings, ' hand auger borings and monitoring well borings 2 The soil plume was divided into two areas, Core & Ring 1, Figure 2 The Core encompasses the borings and excavation samples that held high concentrations of TPH- G Ring 1 encompasses the borings that held low concentrations of TPH-G 3 The Core is 660 ft in aerial extent and Ring 1 is 6,990 ft2 in aerial extent 4 The top of the soil plume in the Core was set at 3-feet bgs, based on soil analytical data and field observations The bottom of the soil plume in the Core was set at 15-feet bgs, based on analytical and field observations 5 The top of the soil plume in Ring I was set at 5-feet bgs, based on soil analytical data and field obseivations The bottom of the soil plume in Area 2 was set at 15-feet bgs, based on analytical data and field observations 1 6 The TPH-G concentrations for the soil samples taken within each area were averaged to give an overall concentration for the area Excavation sidewall sample analysis, in addition to soil boring analysis, were used in determining the contaminate load in each ' area 7 The soil type was denoted as silty, it ranges from silty sand to silty clay 4.0 CONCLUSIONS AND RECOMMENDATIONS Conclusions ' 1 A total of 595 17 tons of contaminated soil including nearly 4,900 pounds of TPH- gasoline was removed from the site 2 All of the contamination in the subsurface was not removed, as evidenced by the ' sidewall sample analysis, however total removal was not the goal of this project The goal of removing the heart of the soil plume was met 3 An estimated 42% of the total mass of contaminants was removed by this excavation ' work The balance is found in the sidewalls of the excavation and below groundwater in the bottom of the excavation