ARCHIVED REPORTS XR0000220 - Laserfiche WebLink

Home Browse Search

California Department of Transportation September 6, 2001 Shop 10 Maintenance Station, Stockton, California Project No 400296001 beled, reconditioned 55-gallon drums The drums were left on-site to be maintained by Caltrans 4.3. 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 EPA method 8015 (modified), and volatile organic compound (VOCs), including MTBE, tertiary-amyl-methyl ether (TAME), isopropyl ether (DIPE), tertiary butyl alcohol (TBA), and ethyl-tertiary-butyl ether (ETBE) using EPA method 8260B Samples were also ana- lyzed for BTEX using EPA method 8021 B A summary of the past and present laboratory results for the groundwater samples is presented in Table 1 Copies of laboratory results and chain-of-custody documents are included in Appendix B • S SUMMARY AND CONCLUSIONS Ninyo & Moore measured depth-to-groundwater and sampled ten wells at the site on June 4-5, 2001 Groundwater elevation data indicates that the groundwater flow is to the northeast beneath the site with a hydraulic gradient of 0 21 feet per foot Comparatively, groundwater measure- ments recorded during the last monitoring event in March 2001 indicated groundwater movement beneath the site was to the east with a gradient of 0 006 feet per foot The groundwa- ter elevation has increased in all wells since the last sampling event Groundwater elevations have decreased in monitoring well MW-9 by 0 95 ft , MW-11 by 0 41 ft , MW-12 by 0 84 ft , MW-13 by 1 0 ft , MW-16 by 0 89 ft , MW-19 by 10 ft , MW-20 by 1 0 f1 , MW-24 by 0 95 ft , MW-25 by 2 05 ft and VM-1 by 0 95 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 VM-1, TPH-G concentration increased from 1,200 µg/l to 3,100 µg/1 Benzene increased • from 217 µg11 to 706 µg/1 Toluene concentration increased from non-detectable levels to 4 0 0296 Olrshoplo 2QOl doc L�