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Rs ona Market � Ea Subsurface Soil and Groundwater Investigation III Report Page 8 consolidated low plasticity, clays, silts, and poorly sorted silty sands The r consolidated nature of the fine-grained unit limited the penetration of the Geoprobe direct push sampler Unconfined groundwater was present in the interbedded fine- grained unit 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 borings (Table of Laboratory Soil Sample Results - November 2002 & January 2003) 3.3 Groundwater Contamination Trace concentrations of gasoline petroleum hydrocarbons, toluene, and MTBE were . detected in a grab water sample from boring B-4 at 45 feet Trace concentrations of toluene were detected in water samples from boring B-3 at 38 feet and boring B-2 at 60 feet The detection in boring B-2 at 60 feet may be cross contamination since contamination was not detected in the 45-foot sample Ethanol was detected in all but one of the similprobe samples, as discussed above, and is attributed to the spray lubricant used by the driller on the drilling and sampling tools Detected groundwater contamination is shown in map view in figure 5 and in cross section in figure 6 4.0 CONCLUSIONS AND RECOMMENDATIONS Contaminants of concern have been identified as gasoline range petroleum hydrocarbons, benzene, toluene, ethyl benzene, xylenes, and MTBE probably sourced from the former underground storage tanks and related piping Soil contamination is limited to the immediate vicinity of the former fuel tanks Trace concentrations of fuel contaminates were detected in the shallow aquifer in boring B-4 located to the west of the tank pit and boring B-3 located to the east of the tank pit Fuel contamination was not detected in samples collected from the same intervals in boring B-6, located approximately 15 feet from boring B-3 The lateral and vertical extent of the release at water quality objectives has been defined by the investigation Quarterly monitoring of the site should continue to confirm the stability of the plume and to evaluate possible risk to the previously identified receptors