Characterization and in-situ remediation of chromium-contaminated soils and sediments at the USCG Support Center, Elizabeth City, NC

Field and laboratory studies were conducted in order to characterize the extent of chromium contamination in the underlying soils and sediments of a chrome-plating shop at the USCG Support Center near Elizabeth City, NC and to evaluate the use of liquid reductants for in situ treatment of the soils at the site. Soil cores were collected from over 20 locations in 1997 and 1998, resulting in over 300 discrete samples to provide data for vertical and horizontal delineation of the chromium. Selective extractions were used to assess the chemical speciation and distribution of the chromium on the soils and its mobilization potential. Results indicate the highest concentrations of total chromium and Cr(VI) are found in the shallow soils immediately beneath that area of the shop where chromic acid tanks had been located. Laboratory Cr(VI) reduction studies were conducted using the most contaminated soils to evaluate the feasibility of using liquid reductants (sodium dithionite, I-ascorbic acid, and free hydroxylamine) at the site to treat the chromium in situ. Results showed sodium dithionite to be the most effective liquid reductant evaluated.