SITE INFORMATION AND CORRESPONDENCE FILE 1

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• • Geo(agicaC7ecknics Inc. Page 2 Georges Service#425.2 September 13, 1999 1998. This information will be used in the performance of the Fate and Transport modeling. The data for this testing was reported in the November 30, 1998 Soil and Groundwater Investigation Report. • An issue that is of concern at this point is that we do not know the direction of flow in the deeper aquifer, since MW-105 (-34 ft deep) encountered different geology then MW- 102 & 107 (-50 ft deep). So there are not three wells in the sandy interval at 50 feet. • Contaminant mass estimate calculations will be made to determine the volume of contamination that is present in the soil and groundwater at the site. Domestic Well Survey • GTI acknowledges that the domestic well survey report prepared on August 25, 1997 is incomplete in regards to showing the locations of all the wells within a 2,000-foot radius of the site. The purpose of the report was to show the locations of wells that GTI was able to obtain construction logs for. • To plot the location of every well within 2,000-feet of the site is not feasible or necessary for the following reasons: ➢ A surveyor would need to be contracted to come to the site to survey and create a base map and then survey in the locations of all of the domestic wells. There are approximatelyseveral dozen to be covred is wells ld 'h om l f a square e. Early cost estimates for this work re $8,000 to $10,000. ➢ The scale of the map would be such that it would be difficult to identify the domestic wells as many would plot on top of each other. ➢ There is no indication that the plume has migrated off site. The downgradient, off site wells, MW-6, MW-7, MW 107 and domestic well . Th Hwy is and domestic well 1697 Durham Ferry Rd has always been non-detect. These wells range from 70 to 175 feet from the former tank pit. )0, The site has a fairly flat has the highest potential for ndwate gradient dng distances. iedoenot contain MTBE, which • GTI recommends that all of the wells within a smaller radius (250 feet) be plotted on a map. One person could easily perform this work in one day. The map would clearly show the locations of the domestic wells in relation to the former tank site. Feasibility Studies • Upon the completion of the fate and transport work, a feasibility study will be performed in order to determine the best remediation alternatives. • Of the possible alternatives, GTI will consider the following: ➢ Source Removal ➢ Oxygen Releasing Compounds C➢ Air Sparging ➢ Vapor Extraction ➢ Pump and Treat Of these options, Vapor Extraction and Pump and Treat do not look promising due to the groundwater being high (7 to 10 feet) and the vadose zone soils being predominantly tight silts and clays. Source removal may be effective because the bulk of contamination is primarily limited to the upper 10 to 15 feet of soil. However all of these alternatives will be reviewed for cost and time efficiency, effectiveness of removing the majority of contamination and how invasive they will be to neighbors.