ARCHIVED REPORTS_XR0007392 CASE 1

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�� KLEtNFELDER 6 CONCLUSIONS AND RECOMMENDATIONS 1 ' 6.1 CONCLUSIONS ' Groundwater elevations ranged from a maximum of 0 84 feet above mean sea level (msl) at MW-4 to —0 61 feet above msl at MW-2 Depth to water was measured at approximately 39 26 to 40 28 feet bgs Groundwater flow was towards the southwest with an approximate gradient of 0 005 ft/ft No product or sheen was observed from groundwater from perimeter monitoring wells MW-2, ' MW-3, and MW-4 An approximate three quarter inch of floating product and a strong petroleum-like odor was noted in the groundwater from monitoring well MW-1 TPH-D, TPH-G, and ethylbenzene were detected in groundwater samples collected from MW-1, located approximately 10 feet down-gradient of the UST area TPH-D was detected at ' concentrations of 32 mg/l and TPH-G at 1 9 mg/l Ethylbenzene was detected in groundwater samples collected from MW-1 at a concentration of 0 57 µg/1 No other BTEX constituents were detected 1n MW-1, including total xylenes, which have been detected in 5 of the 7 previous sampling events TPH-D was detected at a trace concentration of 0 14 mg/l from the groundwater sample collected from MW-2 None of the requested analytes were otherwise detected in the groundwater samples collected from the down-gradient monitoring wells, MW-2 ' and MW-3, nor from the upgradient well MW-4 The concentration of ethylbenzene detected in MW-1 (0 57 µg/1) was found to be well below the State Primary Maximum Contaminant Levels (MCLs) for ethylbenzene which is 300 µg/1 Based on the information obtained, It is Klemfelder's opimon that the groundwater contaminant ' plume is located In the vicinity of MW-1 and the existing UST, and is apparently contained within perimeter monitoring wells MW-2, MW-3 and MW-4 A petroleum product layer has been detected on the surface of groundwater in momtonng wells MW-1 over the past five ' quarterly sampling events at thicknesses ranging from a film (<0 01 feet) to approximately 33 feet (4 inches) During this third quarter 2003 sampling event, product was detected in MW-1 at ' an approximate thickness of 0 06-feet (approximately 3/4 inch) Floating product was not detected in the initial five groundwater sampling events beginning in June 2000 through June 2002 rThe appearance of floating product in MW-1 has been observed since September of 2002 Kleinfelder has noted a general decrease in water levels over time, which may be a contributing factor of product occurring in mon><tonng well MW-1 Groundwater elevations from MW-1 in the initial four groundwater sampling events ranged from 4 55 to 6 92 feet The groundwater elevation of the fifth sampling event was 3 18 feet Over the past five sampling events ' groundwater elevations In MW-1 have ranged from —0 11 to 2 94 feet, with this third quarter 28209 T03/ST03R181 I Page 9 of 1 l ' D 2003 Kleinfelder, Inc December 29,2003