ARCHIVED REPORTS XR0001333 - Laserfiche WebLink

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January 7, 1993 Working To Restore Nature ARCO Service Station 2168, Stockton, California We concluded further investigation of soil near the gasoline tanks was not warranted Dissolved gasoline hydrocarbons were detected in water samples collected 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 Field work was conducted by RESNA and Emcon Associates (Emcon) of Sacramento, California 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 Subjective Analysis and Water-Level Measurements On August 24, 1992, a technician from Emcon measured depths to water, performed 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-ground-water measurements, summarized in Table 1, were used to evaluate the potentiometric surface beneath the site 1 The ground-water flow direction on August 24, 1992, was to the northeast with a hydraulic gradient of 0 003 (Plate 3) The average depth to ground water increased by 179 feet since the previous monitoring event , Ground-Water Sampling and Analyses 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 1028ccar 3100" 2