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' k" K L E I N F E L D E R <br /> 6 CONCLUSTIONS AND RECOMMENDATIONS <br /> i <br />' 6.1 CONCLUSIONS <br /> Groundwater elevations ranged from a maximum of 3 46 feet above mean sea level (msl) at <br />' MW-4 to 2 20 feet above ms] at MW-2 Depth to water was measured approximately 37 feet bgs <br /> Groundwater flow was towards the southwest with an approximate gradient of 0 004 ft/ft <br />' No product or sheen was observed from groundwater from monitoring wells MW-2, MW-3, and <br /> MW-4 A sheen and slight petroleum-like odor was noted in the groundwater from monitoring <br /> well MW-1 <br />' TPH-D TPH-G and ethylbenzene were detected in groundwater samples collected from MW-1 <br />' located approximately 10 feet down-gradient of the UST area TPH-D was detected at <br /> concentrations of 27 mg/1 and TPH-G at 1 7 mg/1 Ethylbenzene was detected from groundwater <br /> samples collected from MWA at concentrations of 16 µg/1 TPH-D was the only requested <br />' analyte detected in the groundwater collected from MW-2 at a trace concentration of 0 076 mg/l <br /> No petroleum constituents were detected from the groundwater samples collected from the <br /> down-gradient monitoring well MW-3 or upgradient well MW-4 <br /> The concentration of ethylbenzene found in MW-1 (1 6 µg11) was found to be well below the <br /> State and Federal Maximum Contaminant Levels (MCLs) for ethylbenzene which is 700 pg/l <br /> Based on the information obtained, it is Kleinfelder's opinion that the groundwater contaminant <br /> plume is located the vicinity of MW-1 and the existing UST Although TPH-D was detected for <br /> the first time at a trace concentration in downgradient well MW-2, it appears the contamination <br /> plume is mostly contained within perimeter monitoring wells MW-2, MW-3 and MW-4 <br />' Additional sampling events should be conducted to evaluate if the trace concentration of TPH-D <br /> found in MW-2 is actually representative of groundwater conditions or possibly due to an error <br /> or is an anomaly <br /> 1 <br /> 6.2 RECOMMENDATIONS <br /> rBased on the data obtained during this assessment, Kleinfelder makes the following <br /> recommendations <br /> 1 Continue quarterly monitoring of the existing monitoring wells (MW-1, MW-2, MW-3, and <br /> MW-4) <br /> 2 Kleinfelder recommends that a copy of this report should be submitted to San Joaquin <br /> County Public Health Services Department, Environmental Health Division (PHS/EHD) and <br /> 18748 T02/ST02R420 Page 9 of 11 <br /> cD 2002 Kleinfelder,Inc August 29, 2002 <br /> r <br />