SITE INFORMATION AND CORRESPONDENCE

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• � Tfi� _ Union Ice Company, ber Street Phase III Site Assesstnent - Repoil of Findings ' & Phase IV Additional Rernediation Proposal Page 3 _ local, rare coarser-grained sediments. It is a typical overbank to back swamp deposit of a large river system. I Clay B is underlain by Sand 2, which is a blue-gray, fine to miedium-grained micaceous sand. The full thickness of this sandl is not known since it was .not penetrated by any of the drilling. However, this Hype of sand is believed to be a typical river channel deposit, which was deposited in sc�1ur fills and in the lower flow regime portions of a large river system. Sa1nd L i las encountered i{i only two 2 wells on the ropert but is robabl ron�tinuotis over the entire site. Ago 3.3 Site Hydrology i The groundwater gradient, at the Weber Street site, is to the southeast. During the April, 1992, sampling event at. the monitoring wells or, ;he site, the piezometric surface sloped to the souffieast at 0.0038 feet'foot. In the vicinity of the tank excavation, .in MW-4S and Iv1W-8, the I at-er -able lies at between 10 and 11 feet below the .surface. This level appears to be somewhat depressed , fro its historic high as indicated by the change from oxidized to reducing sediment in the borings, which occurs.at from 7 to 10 fleet. During the April, 1990, sampling event, groundwater �llevels were measured in the wells over a-24 hour. period and a slight tidal influence was discovered to affect the elevation of the groundwater in the we11i's, ranging from a 0.06 to 0.26 foot fluctuation in the groundwater table. II 4.0 DISCUSSION OF PRASE III ASSESSMENT The borings, during this phase, demonstrated that a plume of gasoline coninininated soil extends to the southeast of theprevious excavation!, High levels of cortarninants were detected in borings BX-1 and BX=3, but only low levels were present in BX-2 and BX-4, which suggest that they are near the zero line of� contamination. However, the plume of highest contamination appears to be about five feet ids'} thick and covers an area 20 feet wide by 40 feet long (Figure 2.). This cbre is i surrounded by _: broad envelope of soils with low levels of BTX&E, which extends to the south and east of the previous remedial excavation site (Figure 3). It does not appear that groundwater has been impacted by the contamination, even though the standing water level (10-11 feet below surface) is higher than some of the I I'