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KLEINFELDER <br /> 3 SUMMARY AND RECOMMENDATIONS <br /> Groundwater monitoring has been conducted at this facility since 1987 to evaluate <br /> groundwater quality A summary of the current site conditions and a recommendation <br /> for subsequent work are as follows <br /> • During this event, the average depth to groundwater among the wells was 43 73 <br /> feet bgs (-27 06 feet msl) The groundwater flow was generally easterly to <br /> southeasterly at a gradient of approximately 0 004 feet per linear foot <br /> ' • The total depth measurements Indicated that an appreciable amount of sediment <br /> has Infiltrated the air-sparging wells SP-1, SP-5, and SP-6 To conduct further <br /> ' sampling or remediation activities at these locations, the air-sparging wells will <br /> need to be developed <br /> ' • The benzene concentration increased in the down-gradient well PZ-1 <br /> Concentrations in the suspected source area were stable or decreased <br /> The current BTEX concentrations were evaluated against the California Drinking <br /> Water MCLs Based on the current groundwater monitoring data, the MCL for <br /> ' benzene has been exceeded in wells MW-1, MW-7, SP-1, and PZ-1 The MCL <br /> for toluene was exceeded in wells SP-1 and PZ-1 The MCL for ethylbenzene <br /> was exceeded in well SP-1 The MCL for xylenes were exceeded in wells MW-1 <br /> and SP-1 <br /> • The TPH-G concentrations increased in wells MW-1, MW-12, SP-1, SP-2, SP4, <br /> and SP-6 The remaining wells remained stable or decreased in concentration r <br /> • The oxygenate DIPE was detected in wells yg e s MW-7, MW-12, and PZ-1 <br /> • The analyte 1,2-DCA was detected in wells MW-7, MW-8, MW-12, and SP-5 <br /> 1,2-DCA was a component of gasoline during the 1980's Based on the current <br /> groundwater monitoring data, the MCL for 1 ,2-DCA has been exceeded in wells <br /> MW-7, MW-8, MW-12, and SP-5 <br /> C23-484517-BOOISAC5R609 Page 10 of 12 September 14, 2005 <br /> ' Copyright 2005 Kleinfelder, Inc <br />