ARCHIVED REPORTS XR0001332 - Laserfiche WebLink

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March 12, 1993 Working To Restore Nature ARCO Service Station 2168, Stockton, California Dissolved gasoline hydrocarbons were detected in water sampleyollected from the three wells Purgeable halocarbons were not detected, except for 1,2-dichloroethane which was detected in monitoring well MW-2 Fecal and total coliform bacteria were not detected in the sample collected from well MW-3 On April 28, 1992, while clearing underground utilities, a product line was accidently fractured and subsequently leaked approximately 2 to 5 gallons into adjacent soil To evaluate the effects of the leak, RESNA collected soil samples above and below the product line Results of laboratory analyses indicated TPHg was detected in these samples at 45 and 4,100 ppm GROUND-WATER MONITORING AND ANALYSES 1 Field work was conducted by RESNA and Emcon Associates (Emcon) of Sacramento, Califorrua Emcon was contracted by ARCO, Emcon subsequently forwarded their field notes and the laboratory reports to RESNA Data obtained from Emcon is presented in the Appendix to this report 11.. On December 17 1992, a technician from Emco n measured depths to water, performed VA subjective analyses of ground water, and collected ground-water samples from the wells for laboratory analyses The technician noted no floating product or sheen in the three wells (Table 1) The wellhead elevations of the monitoring wells at the site were previously surveyed by Tom O Morrow, Inc of West Sacramento California, a licensed land surveyor (California Land Surveyors No 3275) The surveyed elevations and the depth-to-groundwater measurements, summarized in Table 1, were used to evaluate the potentiometric surface beneath the site The ground-water flow direction on December 17, 1992, was to the northeast with a hydraulic gradient of 0 002 (Plate 3) The average depth to ground water increased by 0 77 feet since the previous monitoring event Ground-water samples were analyzed for TPHg and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using Environmental Protection Agency (EPA) Methods 5030 and 8020 and standard methods prescribed by the State of California Samples were also analyzed for halogenated volatile organic compounds using EPA Methods 5030/601, and the sample from well MW-2 was analyzed for TOG using EPA Method 5520B These samples were analyzed at Columbia Analytical Services, Inc in San ,Tose, California (Hazardous Waste Testing Laboratory Certificate No 1426) The sample from well MW-3 was also submitted to Sequoia Analytical in Sacramento, California, for analysis of total and fecal , 0175ccar 31009-6 2