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cc,., roi raa lc U, a 1 ca Stockton Maintenance Station, Stockton, California Project No 400296-01 ferred into labeled, reconditioned 55-gallon drums The drums were left on-site to be maintained by Caltrans 43 Laboratory Analysis The groundwater samples were submitted for analysis to AL, a State of California-certified hazardous waste analytical laboratory Samples were analyzed for TPH-G and TPH-D, using method EPA 8015 (modified) Samples were analyzed for BTEX, methyl tertiary-butyl ether (MTBE), tertiary-amyl-methyl ether (TAME), isopropyl ether (DIPE), tertiary butyl (TBA), ethyl-tertiary-butyl ether (ETBE), and volatile organic compounds (VOCs) using method EPA 8260B A summary of the past and present laboratory results for the groundwater sam- ples is presented in Table 1 Copies of laboratory results and chain-of-custody documents are included in Appendix B 5 SUMMARY AND CONCLUSIONS Ninyo & Moore measured depth-to-groundwater and sampled fourteen wells at the site on Sep- tember 13, 2000 Groundwater elevation data indicates that the groundwater flows to the east beneath the site with a hydraulic gradient of 0 002 feet per foot Comparatively, groundwater levels taken during the last monitoring event in June 2000 indicate flow direction east beneath the site with a hydraulic gradient of 0 004 feet per foot Groundwater elevation has decreased in all of the on-site wells since the last monitoring event Groundwater elevations have decreased in monitoring well MW-1 by 2 94 ft , MW-2 by 2 93 ft , MW-3 by 2 92 fl , MNV-4 by 2 92 ft , MW- 5 by 2 94 ft, MW-6 by 2 88 ft , MW-7 by 2 93 ft , MW-8 by 2 91 ft , MW-9 by 2 92 ft , MW-10 by 2 94 ft , MW-11 by 2 93 ft , MW-12 by 2 90 ft , VW-1 by 2 90 ft and VW-2 by 3 23 ft , re- spectively Laboratory analytical data has indicated changes in many of the compounds analyzed in samples taken from ,,arious wells on site since the June 2000 monitoring event In well MW-2 Benzene concentrations increased from non-detectable levels to 6 8 µg/1 0290 01 r SW,ktan Fail IQ 000 doc 4 �b ro 0,®u I