ABSTRACT

A site assessment was conducted to determine the distribution of chlorinated compounds in soil and groundwater at a chemical plant in Geismar, Louisiana. The assessment first included an investigation of the source(s) of the contaminants using historic aerial photographs, employee interviews and plant records. Next, the stratigraphic framework of the site was defined with a hydrogeological investigation using historic boring logs and cone penetrometer testing (CPT). Finally, a plume investigation was performed to determine the horizontal and vertical extent of the contamination using direct-push methods for the sampling of soil and groundwater.

It was determined that chlorinated compounds originated from leaking drums and cleaning operations prior to 1975. Downward migration of these compounds may have been promoted by the installation of uncased 15-meter wooden pilings. The contamination is limited, both vertically and horizontally, to three hydrogeologic zones: (1) the first water-bearing silt zone; (2) an intermediate zone consisting of interlayered silt and clay; and (3) the second water-bearing silt zone. The concentrations of chlorinated compounds are greatest in the intermediate zone. There is some evidence of natural degradation of the chlorinated compounds, particularly in the first water-bearing zone.