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Ripona Market Vertical Groundwater Investigation&November 2003 Quarterly Report Page: 10 1 consolidated nature of the fine-grained unit provided a solid foundation for the installation of the conductor casing. Shallow unconfined groundwater was present at an approximate depth of 25 feet. The basal portion of the borings below the fine-grained unit is composed of fine to medium grained moderately sorted unconsolidated sands. The sands are unstable and often flowed into the borehole under hydraulic pressure. The "heaving sands" flowing into the open augers restricted the insertion of the drill bit and sampling , tools. As noted on the logs "heaving sands" prevented the collection of soil and -- water samples at several of the planned intervals. 3.2 Soil Contamination Soils contamination was not detected in any of the soil samples collected in the boring (Table of Laboratory Soil Sample Results -- December 3, 2003) Fuel + oxygenates were previously detected in soil samples collected at depths of 25 and 30 feet in a boring in the vicinity of the former underground storage tanks. An MTBE contamination cross section is shown as figure 4. r, 3.3 Groundwater Contamination Moderate concentrations of MTBE were detected in a water sample collected from b well MW-2 located adjacent to the former underground storage tanks. Trace concentrations of MTBE were detected in a water sample collected from the deep well, MW-4. MTBE groundwater contamination is shown in map view in figure 6 and in cross section in figure 4. MTBE groundwater contamination is limited to the vicinity of well MW-2 and defined vertically at a depth of 55 to 60 feet vertically. r 4.0 CONCLUSIONS AND RECOMMENDATIONS } + The lateral and vertical extent of MTBE, the contaminant of concern has been defined laterally and vertically to be restricted to the immediate vicinity of the former underground storage tanks. A survey of potential contamination plume F.' z receptors within 2,000 feet of the point of release identified.' tergal well approximately 2000 feet from the former underground storage tanks. It appears that the release does not pose a risk to the identified water wells in the vicinity of Ripona Market. Quarterly monitoring of all wells will continue. If the preliminary results of the recent groundwater monitoring are confirmed, an evaluation of the potential long term threat of the impacted groundwater will be conducted and a corrective action plan prepared including recommendations for addition work or site closure. F ` ;