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C,eol 4uI Teckoaa&c. City of Escalon Page 8 Project No.: 750.2 Y May 16,2005 • Soil removed during the installation of 641 feet of monitoring and extraction well casing 0 Soil removed during the advancement of 650 feet of soil borings Elevated MtBE levels were detected in the shallow lithology near MW-1 and HP-1 during the 1999 boring and well installation activities. MtBE concentrations from these two sample points attenuated rapidly with depth. The October 2003 soil boring in the same area showed no MtBE remaining in the area. Very low levels of MtBE were detected in the vicinity of HP-5 during the 1999 soil and groundwater investigative activities. The October 2003 soil boring in the same area showed no MtBE remaining in the area. r 3.7 Remedial Technologies An Internal Combustion (IC) system was in operation between February 2002 and January 2003. The IC ran for approximately 290 days and removed about 707 gallons of TPH-G from ..r the vadose zone(Table 9). A Soil Vapor Extraction and Granulated Activated Carbon (SVE/GAC) system was installed r during September 2004 and operated for approximately 183 days during which time about 306 gallons of TPH-G were removed (Table 10). .�--� Approximately 270 cubic yards of soil was removed during tank excavation activities. Approximately 30 cubic yards of soil have been removed as drill cuttings during the installation of monitoring wells, vapor extraction wells, soil borings and GeoProbe boreholes. Additional soil has been removed or aerated during trenching and remedial equipment installation activities. Approximately 500 gallons of contaminated groundwater per year are removed from the site during the development, purging and sampling of groundwater monitoring wells. This volume of soil cuttings and groundwater removed during investigation activities as well as soil aeration during trenching activates were not used to reduce the mass estimate of contaminants remaining at COE. However, this is additional evidence of the over-cautious nature of the mass estimate calculations. 3.8 BAT Since the tank and the primary soil contamination source have been removed, eventually background conditions will be achieved in the soil and groundwater at the site. Excavation of the soil surrounding the former USTs and removal of soil boring cuttings were technologies employed to remediate the contamination detected at COE. Soil vapor extraction methods were employed at the site for approximately 473 days and resulted in the removal of approximately 1,013 gallons of TPH-G from the vadose zone.