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Fourth Quarter 2000 Ground Water Monitoring Report ort Cleanup and Abatement Order No. 5-00-707 'EAI Pro'ect No. 1232 4.5 Investigation and Cleanup Activities Assessment t A quarterly report summarizing the effectiveness of the air sparge/vapor extraction activities at the Wards site was previously submitted to the RWQCB on October 10, 2000 (see Section F1.1.4). F A Work Plan outlining areas of the site that require additional investigation to assess the vertical and lateral extent of hydrocarbon impacted soil and ground water was presented to the RWQCB on December 27, 2000. Several additional wells were proposed in the Work Plan. Unocal and EAI are in the process of obtaining permits to install the wells. Upon approval of the Work Plan by the RWQCB and receipt of permits to install the wells, EAI will initiate the proposed work. Data obtained from this phase of work will then be used to prepare a Remediation Plan for the Unocal site. F4.6 Analytical Testing Results No MTBE, TBA, D1PE, ETBE, TAME, EDB, ethanol or methanol, above laboratory reporting limits, were detected in any of the ground water samples. Methylene chloride was detected in well MW-13 at 25 gg/L. It is EAT's opinion that this compound may have originated from the laboratory since this compound is a common FJ1 laboratory contaminant. Therefore, it was not included in Table 1. f"71 Chloroform was detected in several wells. Since chloroform is not typically identified in ground water at these sites, in EAI's opinion this compound is derived from the tap water used to decontaminate the pump and hose system. Hydrocarbon concentrations in ground water are generally similar to the prior quarter testing results with two exceptions (MW-3 and MW-4). During recent sampling events, MW-3 had TPH-G and benzene concentrations at approximately 500 µg/Land 30 µg, respectively. During this sampling event, both TPH-G (19,400 µg/L) and benzene (1,$00 µg/L) showed an increase F in concentration to numbers similar to those observed prior to initiation of remediation activities (see Table 1). Well MW-4 had a significant decrease in hydrocarbon concentration to below the laboratory detection limit. FJData continue to indicate that the air sparging/vapor extractions stem is effectively ely removing hydrocarbons from beneath the Wards site as a significant reduction in hydrocarbon 0, concentrations in ground water has been observed since operation of the remediation system was initiated. F4.7 Future Activities The next quarterly ground water monitoring for the site is scheduled for March 2001. A report documenting results of the ground water monitoring will be submitted to the RWQCB by April 1 S, 2001. F; BUN:1272RO092 S ENVIRONMENTAL AUDIT, INC. ,