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Mr. James Barton November 2, 2004 Page 5 Well Surveying Groundwater monitoring well MW-31 and MW-32 will be surveyed by a California licensed land surveyor in accordance with State of California Assembly Bill AB2886 prior to the first quarter 2005 monitoring and sampling event. The top-of-casing (TOC) elevation of the monitoring well and ground surface elevation will be surveyed relative to mean sea level within 0.01 foot. Permitting and Scheduling ENSR will submit soil boring/well installation permit applications to the SJCEHD. Following approval of well installation permits the proposed scope of work will be implemented. Anticipated submittal date for the soil boring permits is November 3, 2004. Conclusions/Recommendations Groundwater analytical results from the July 2004 monitoring and sampling event appear to show recent plume movement as evidenced by concentrations of petroleum hydrocarbons in wells MW-14 and MW-18D screened in Unit B to the north and east of the former Unocal site. Groundwater samples collected from wells MW-14 and MW-18D contained concentrations of petroleum hydrocarbons, including TPHg and benzene above laboratory reporting limits. Concentrations of TPHg and benzene in groundwater were reported at 80 pg/L and 6.0 pg/L, respectively in samples collected from MW-14. Concentrations of TPHg and benzene in groundwater were reported at 120 pg/L and 0.96 pg/L, respectively in samples collected from MW-18D. In order to decrease the risk of moving the plume in Unit B, we set the flow rate for AS-26 at approximately 30 percent of maximum when we restarted the AS system in June 2004. After evaluating the groundwater results from samples collected on July 13, 2004, we reduced the flow rate for AS-26 to approximately 15 percent of maximum capacity. We believe that this setting will allow us to: 1. Meet the CAO requirement for sparging in all aquifer units. 2. Limit the potential for moving the plume in Unit B. Between September 2002 and August 2003, low level to non detectable concentrations of TPHg and benzene were reported in wells MW-14 and MW-18D. During this same period, the AS/SVE system was operated continuously. Sparging activities may have increased the concentrations of dissolved TPHg and benzene in the vicinity of wells MW-14 and MW-18D. In order to monitor the plume movement in Unit B more effectively in the future, ENSR recommends adding wells MW-14 and MW-18D to our monthly sampling program. Samples from wells MW-14 and MW-18D will be analyzed for TPHg and benzene. J:1Projects10694015098-2931Final\ReportslWork Plans15098 Work Plan-SVE AS System.doc