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Additional Soil and Groundwater Investigation Report Canepa's Car Wash(Park Street) ' May 8,2002 Page 6 5 0 SLMMARY/DISCUSSION OF RESULTS Condor conducted soil and groundwater investigation activities at the site from March 25, 2002 through ' March 28, 2002 The investigation activities included the installation of two CPT borings (CPTI, near the former USTs and CPT2, down-gradient of the former USTs, near MW-5) to prepare geological logs in those locations One soil boring (SBI) was installed near the former USTs to collect soil samples ranging ' in depth from 66 to 82 feet bgs The purpose of SBI was to evaluate the vertical extent of soil contamination in the vicinity of the former USTs Three hydropunch borings (HPI through HP3) were installed near CPTi to collect three groundwater samples (one per boring) from depths ranging from 79 to 123 feet bgs to correspond with permeable horizons identified in CPTI Three hydropunch borings (HP4 through HP6)were installed near CPT2 to collect three groundwater samples (one per boring) from depths ranging from 74 to 107 feet bgs to correspond with permeable horizons identified in CPT2 The purpose of HP 1 through HP6 was to investigate the vertical extent of groundwater contamination at the site and to evaluate if lithologic composition was limiting the vertical extent of groundwater contamination Twelve hydropunch borings (HP7 through HP18) were installed to collect twelve shallow groundwater samples (one per boring) for the purpose of evaluating the lateral extent of shallow groundwater contamination Three hydropunch borings (HP19 through HP21) were installed to collect three groundwater samples (one per boring) from a horizon below the shallowest groundwater bearing horizon (approximately 46 to 50 feet bgs) to begin evaluation of the vertical extent of the groundwater ' contamination down-gradient of the site The SBI soil samples were collected from saturated horizons well below the current water table The ' laboratory analytical results of the soil samples collected from SBI indicate that relatively elevated concentrations of gasoline constituents are present down to the deepest sample collected (approximately 82 feet bgs) The lowest concentrations of gasoline constituents were detected in the sample collected at ' 82 feet bgs, indicating the potential for some attenuation of concentrations beginning at that depth MTBE was not detected at or above the laboratory reported detection limit in any of the soil samples from SBI The groundwater sample collected from HPI at a similar depth as the soil samples (79 to 83 feet bgs) contained a TPH-G concentration one to two orders of magnitude lower than the concentrations present in the soil samples This indicates that the gasoline is partitioning into the groundwater phase with some difficulty, probably as a result of the relatively fine-grained soil texture ' The laboratory analytical results of the groundwater samples collected from HPI through HP6 indicate that relatively elevated concentrations of gasoline constituents are present at depths well below the water ' table in the locations of the CPTI and CPT2 (near the former USTs and down-gradient of the former USTs, respectively) The results associated with CPTI indicate an increasing trend of contaminant concentration with depth with benzene concentrations from 65 µg/L at 79 to 83 feet bgs, to 1,900 µg/L in ' the deepest sample at 119 to 123 feet bgs As opposed to CPT], the results associated with CPT2 indicate a trend of decreasing groundwater contaminant concentration with depth, with a benzene concentration of 17,000 µg/l, at 74 to 78 feet bgs and 150 µg/L at the refusal depth of 107 feet bgs The results of the ' deepest groundwater samples collected from the hydropunch borings associated with the CPT borings indicate that the vertical extent of petroleum hydrocarbon contamination has not yet been fully characterized No soil horizon was encountered during the investigation that apparently has substantially ' impeded the vertical movement of gasoline contamination The results of the groundwater samples collected from HP8, HP9, HP10 and HP11 indicate that the shallow groundwater northeast of the site is not impacted by gasoline constituents at or above the ' laboratory reported detection limits The results of the groundwater samples collected from HP12 ' CONDOR