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C40togccaI uck as I" Page 5 GW Monitoring Report Ted Peters-AST Project No 701 2 April 24,2002 • Figure 4 illustrates TPH-G concentrations in groundwater in the vicinity of the former g g Y ASTs The highest level of TPH-G detected is in well MW-7 on the northwest side of the parcel It is known that an adjacent site (SE corner of the Airport Way and Yosemite Avenue intersection) has had a gasoline groundwater impact Data from that site indicate a northward component of plume migration that has caused an MTBE impact to domestic wells immediately west of the Ted Peters site MTBE has not been detected at the Ted Peters site and is not a chemical of concern Additional monitoring is necessary to determine if the detection in MW-7 represents a detached plume from the former UST ' area or if it is sourced from a different release • Figure 5 illustrates TPH-D concentrations in groundwater in the vicinity of the former ASTs Wells MW-5 and MW-6 contained diesel contamination above the laboratory reporting limits at 62000 and 190 µg/l, respectively GTI's previous GeoProbe ' investigation revealed that the diesel contamination is limited to the area of former ASTs and associated dispensers This is the second time low levels of diesel have been detected in well MW-6, which is located adjacent to the shop sump area ' • Gasoline oxygenates MTBE, TAME, ETBE, DIPE, TBA, Methanol & Ethanol were not present in any well above the laboratory detection limits + Dissolved Lead was not present in any well above the laboratory detection limits 4.0 CONCLUSIONS & RECOMMENDATIONS Conclusions 1 Groundwater flow is predominantly to the northwest for both the AST and UST sites on this property GTI believes that previous southwesterly directions noted in the AST area ' are anomalous based on the presence of free product in MW-5 and/or the spatial orientation of the wells 2 TPH-G, TPH-D or volatile organic compounds are present in four of the groundwater ' monitoring wells 3 The fact that the TPH-G concentration increases downgradient suggests that the gasoline plume is displaced from its source The only two known sources of gasoline in this area ' are the USTs onsite and the USTs used for the Union 76 Station on the corner (referred to above) Recommendations 1 GTI has prepared a work plan for additional plume definition in accordance with the directives from the RWQCB-CVR The work plan includes provisions for conducting a soil gas survey in the northwest portion of the site The RWQCB-CVR has approved the ' work plan and it is scheduled for early May 2002 2 Maintain the current quarterly groundwater monitoring event schedule The next event is scheduled for May 2002 3 Discontinue analyses for gasoline oxygenates and lead due to their non-detection in ' accordance with the MRP requirements 4 Discontinue analyses for VOCs on a quarterly basis and reduce the testing to annual in wells MW-4 through MW-7 This is a formal request for the Board to modify the MRP to reflect this request The reason for this change is that no chlorinated solvents are detected and the only VOCs found in these wells are related to the petroleum contamination, not solvents