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Stockton Meat Plant - Case Closure Page 12 March, 1996 be contributing to not only the coliform detection, but also the reported diesel fuel reported in the sampling events? There is a strong correlation for this ' argument, since coliform can be tracer of wastewater leaks and wastewater can convey petroleum hydrocarbons. ' SUMMARY AND CONCLUSIONS Releases of hydrocarbons from underground tanks and piping have been ' investigated, remediated, and monitored over an eight year time frame With the removal of the underground tanks, piping, and affected soils, the sources of the hydrocarbons have been eliminated from the remediated tank site Low levels of residual hydrocarbons remain in the soil and trace to low concentrations of hydrocarbons detected in the ground water do not appear to be impacting the beneficial uses of the site Groundwater data collected over the last three years (eight sampling events) suggest that the reported release of diesel fuel from the tank site has impacted local soils and ground water only Diesel concentrations have varied within the monitoring wells, but all reported concentrations have been less than 1 mg/l as diesel. There appears to be a slight correlation between a rise in ground water and an increase in hydrocarbon concentration The low concentrations of hydrocarbons as diesel and the absence of volatile hydrocarbons in the ground water samples coupled with the reported Cal Water Services decision to eliminate pumping of groundwater in 1978 from a service well (No 72) located less than a 1/4 mile down gradient of the site because of degraded groundwater (high TDS and methane gas) suggest that the beneficial uses of ground water in the uppermost water-bearing zone have not been affected by the tank site Additionally, a Tier II risk assessment (Attachment H), concludes that the residual concentrations of hydrocarbons in soil and groundwater remaining within the property (both the tank site and the overall Safeway Meat Processing Plant area), are below those levels which pose unacceptable risks to workers and unacceptable impacts to groundwater quality The soil and water concentrations used in the risk assessment were taken from previous investigation and reports prepared by others for Safeway RECOMMENDATION We recommend that this case be closed The soil and ground water quality data indicate diesel is present in the soil and ground water at levels that do not impact beneficial uses nor pose a health risk to workers or ground water quality Further remediation is not warranted nor required by the project, additional water quality benefits would not be derived by additional soil . removal or remediation The conclusion of the risk assessment is the residual hydrocarbon compounds reported at the site (PNAs, trace volatile