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1 � <br /> California Department of Transportation August 17, 1999 <br /> Stockton Maintenance Station, Stockton, California Project No 103872-02 <br />' 43 Laboratory Analysis <br /> The groundwater samples were submitted for analysis to AL, a State of California-certified <br /> hazardous waste analytical laboratory Samples were analyzed for TPH-G and TPH-D, using <br />' method EPA 8015 (modified) Samples were analyzed foi BTEX meth)I tertiary-butyl ether <br /> (MTBE), tertiary-amyl-methyl ether (TAME), isopropyl ether (D1PE) tertiary butyl (TBA), <br /> 1 ethyl-tertiary-butyl ether (ETBE), and volatile organic compounds (VOCs) using method <br /> EPA 8260B A summary of the past and present laboratory results for the gioundwatei sam- <br /> ples is presented in Table 1 Copies of laboratory results and chain-of-custody documents ale <br /> included in Appendix B <br /> I <br /> S SUMMARY AND CONCLUSIONS <br />' Ninyo & Moore measured depth-to-gioundwatei and sampled fourteen wells at the site on June <br /> 24, 1999 Groundwater elevation data indicates that the groundwater flows to the south beneath <br /> Mthe site with a hydraulic gradient of 0 002 feet per foot Comparatively, groundwater levels taken <br /> during the last monitoring event in Api it 1999 indicate groundwater movement beneath the site <br />' towards the southwest under a hydraulic gradient of 0 009 feet per foot The depth to groundwa- <br /> ter has increased in all but one of the on-site wells since the last monitoring event At MW-3, the <br /> tdepth to groundwater has decreased since the last monitoring event Depth to groundwater level <br /> increases are as follows MW-1, 0 39 ft , MW-2, 0 29 ft , MW-4, 0 30 fl , MW-5, 0 37 ft , WM- <br />' 6, 0 22 ft , MW-7, 0 3 ft , MW-8, 0 40 ft , MW-9, 0 41 ft , MW-10, 0 23 ft , MW-11, 0 39 ft , <br /> MW-12, 0 45 ft , VW-1, 0 29 ft , and VW-2, 0 23 ft At MW-3, the depth to groundwater de- <br /> creased by 0 37 ft <br /> Laboratory data has indicated changes in many of the compounds analyzed for in samples taken <br /> from various wells on site since the April 1999 monitoring event Highlights of the analytical <br />' data follows <br /> According to laboratory data well MW-1 showed increased benzene concentrations from non <br /> detect to 2 26 microgram per liter (ug/1) since April 1999 Total xylenes concentration increased <br /> from non-detect to 16 ug/1 <br />' s.Lwn doc 4 <br />