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California Department of Transportation June 19, 2001 p p Shop 10 Maintenance Station, Stockton, California Project No 400296001 i ma via United Parcel Service (UPS) Purged and decontamination water generated during sampling activities were transferred 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 ten wells at the site on Decem- berl2 and 13, 2000 Groundwater elevation data indicates that the groundwater flow is to the east beneath the site with a hydraulic gradient of 0 004 feet per foot Comparatively, groundwater measurements recorded during the last monitoring event in September 2000 indicated ground- water movement beneath the site was to the east with a gradient of 0 005 feet per foot The groundwater elevation has increased to all wells since the last sampling event Groundwater ele- vations have increased in monitoring well MW-9 by 0 61 ft , MW-11 by 0 64 ft , MW-12 by 0 52 ft , MW-13 by 0 57 ft , MW-16 by 0 62 ft , MW-19 by 0 54 ft , MW-20 by 0 72 ft , MW-24 by ' 0 49 ft , MW-25 by 0 55 ft and VM-1 by 0 54 ft Laboratory data indicates changes in concentrations in many of the compounds analyzed in sam- ples taken from various wells on site since the last monitoring event ' In well MW-13, TPH-G concentration increased from 200 µg/1 to 250 µg11 029"1c shop ID F\L 4Q2000 doc 4