ARCHIVED REPORTS XR0010525 - Laserfiche WebLink

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EXECUTIVE SUMMARY • Groundwater monitoring was performed at 8125 S El Dorado Street (J&L Market) on January 2, 2003 After the depth to the static water level was measured, the standing water was purged and water samples were collected from the three monitoring wells and the out-of-service domestic well The samples were analyzed for Total Petroleum Hydrocarbons in the gasoline range, volatile aromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylene), gasoline oxygenates (methyl tertiary butyl ether, etc ), and lead scavengers (1,2-dichloroethane) The domestic well was also analyzed for Total Petroleum Hydrocarbons in the diesel range Gasoline was detected in the water samples from the same two wells as in previous quarters (JLM-3 and JLM-5) Concentrations of 56 and 1100 parts per billion were reported, representing a decline of 45%to 95% since June 2002 Concentrations of some other hydrocarbons also declined, particularly benzene in JLM-3 and xylene in JLM-5 Other analytes, especially 1,2-DCA, have remained constant In the third well (JLM-4), most analytes remain near or below the detection limit Benzene, toluene, ethylbenzene, and 1,2-DCA were detected in the domestic well at concentrations ranging up to about 1 part per billion The pump has now been removed from this well and it is due to be abandoned in accordance with the requirements of San Joaquin County in the near future • The depth to groundwater on January 2 was between 25 and 25 5 feet, which is one foot less than it was in June and 3 5 feet less than in September Using the three-point method, a groundwater elevation map was constructed and a hydraulic gradient of 0 0022 ft/ft was calculated Groundwater continues to flow to the southeast, from the dispenser and former UST cavity toward JLM-3 Because concentrations have decreased rather than increased in this well, it is likely that no hydrocarbon source exists northwest of JLM-3 The decline in concentrations may be due to downgradient dispersion (dilution), and concentrations may continue to attenuate naturally by this process i 1