ABSTRACT

Pre-RCRA disposal practices caused the release of chlorinated hydrocarbons (CHCs) into the shallow ground water at the Paxon facility. This impact was reported to the Louisiana Department of Environmental Quality after a due diligence survey discovered the contamination. A phased investigative approach determined that the upper three water bearing units are affected by multiple contaminants forming a DNAPL plume.

Remedial actions proposed to the Agency and implemented during 1994-95 includes soil vapor extraction and air sparging for uppermost zone and pump and treat for contaminated water removal in all three zones. During the past 2 1/2 years of operation, the system efficiency has been evaluated and continuous adjustments have been made to enhance contaminant recovery.

Of primary concern to the facility is the control of downward movement of contaminants. Efforts to optimize recovery included manipulation of recovery rates and installation of additional equipment. Data assimilated during system operation suggests the effective recovery of CHCs in the upper two zones, however, it is apparent that zone three contaminant migrations may have been exacerbated by pumping the second zone. Contaminant levels rose dramatically in zone three after the startup of recovery of zone two. Conversion of the observation well in zone three to a recovery well has shown effective removal of CHCs.

This paper will focus on system reaction to changing vadose zone conditions, efforts to improve contaminant recovery, and the problems of managing downward movement of DNAPLs.

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