SITE INFORMATION AND CORRESPONDENCE_FILE 2

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15 May 2009 AGE-NC Project No. 95-0103 Page 3 of 6 through the ground water sparging, but are not seen off-site due to the lack of added oxygen. Due to the lack of significant petroleum biodegrading microorganisms off site,natural attenuation of the petroleum hydrocarbons through biologic activities may not be occurring. • The letter states"An understanding of the hydrogeology of the site (an explanation why the dissolved contaminate mass migrates westward while the groundwater gradient is eastward". AGE reviewed available ground water elevation contour maps, generated over the history of the project. Additionally,AGE reviewed the historical UST operation on the site ( approximately 55 years) and determined that ground water monitoring has only be occurring for 15 years or 30% of the time UST were operation on the site. Reported leaks prior to the application of regulatory requirements by State were the responsibility of and monitored by the fire departments.However,the site had three apparent generations of UST removed in the 1990s.A reported tank removal occurred in 1963 by the Shell Oil Company, however, AGE has not readily found records of the tank replacement. Therefore, the cumulative ground water elevation(seasonal drought)and the ground water flow data set for the site is limited, when compared to UST operation. AGE documented the ground water flow direction south and southwest during the early portion of the site investigation 1994 to 1998 and some subsequent flow directions southeast in 2003. A significant rise in the ground water elevation level may have caused the current ground water flow direction towards the east,however,the migration of the dissolved contamination is documented south on-site under the building(well EW-1)and southwest towards well MW-5. The EHD presented additional comments on the Chapin Petition: The first paragraph of the second page points out the EHD conjecture of Chapin Petition assertion the reduction of mass of 95%at the site and the Chapin assertion that continued remediation effort would address the remaining 5%of the mass release at the site. As noted above,the site operated as a commercial fueling facility for 55 years; over which time several UST were abandoned in place and replaced or upgraded. Certainly, no piping system would have lasted 55 years and some replacement or at minimal repairs occurred.As also noted above major oil company held leases for the site and may have replaced tanks when ever needed;one report from 1973 was a loss of fuel for 60 days which may have equaled 12,000-gallons of fuel (followed by tank replacement). As noted in the EHD file,one of the 8,000-gallon UST was not in use when it was removed;based on the fact that UST no longer would hold fuel above a level of 5,000-gallons. This decommissioning was accomplished after a fuel delivery was noted to have be short by 3,000-gallons.The maximum mass load on the site is uncertain. The first paragraph of the second page points out the EHD conjecture of Chapin Petition assertion the mass of adsorbed contamination was underestimated as soil data from under the building was not utilized in the residual mass estimate.Soil sample collected in 2003 under the building at the site Advanced Geo Environmental,Inc.