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■VZ1 INC 9 Zone of Influence Calculated and Assumptions Used for the Subsurface Remediation System and the Zone of Capture Attained tned for the Soil and Groundwater Remediation System The zone of influence and assumptions for the groundwater remediation system were presented in McLaren (1989b) and WaterWork (1990) 10 Reports/information missing from regulatory agency files No reports or information are known to not have been submitted or missing from any of the regulatory agency files to our knowledge 11 Best Available Technology (BAT) Used or an Explanation for Not Using BAT The BAT utilized for the groundwater remediation effort was a pump and treat system with a carbon activated filter No soil remediation effort was attempted because 1) the shallow nature of the total thickness of the vadose zone (less than 15 to 20 feet below ground surface), 2) the predominant lithoiogy of the site is fine grained material (silt and clay) which would not be viable for either soil aeration or vapor extraction system remediation, 3) the relative low-concentrations of both total petroleum hydrocarbon as gasoline and benzene concentrations in the soil do not pose a significant public health threat, and 4) dissolved oxygen content in the groundwater suggests an active naturally occurring biodegradation is currently underway that will ultimately destroy all hydrocarbon components 12 Reasons Why Background Was Unattainable Using BAT Background concentrations of hydrocarbon components in the groundwater were not attainable using the pump and treat system This is a result of the fluctuating levels of the groundwater table constantly reexposing hydrocarbon-contaminated soil in the vadose zone and within the capillary fringe of the watertable to release hydrocarbon components into the underlying water table This results in a continuing release of very low-level concentrations 19150011 005 40