W11 PM Advances in Biorestoration Strategies for Contaminated Sediments
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 343-344

(ROC-1118-276452) Hydraulic Separation during Dredging Facilitates Cleanup of Contaminated Sediments.

Zhao, X¹, Drumm, L¹, Rockne, K¹, ¹ Department of Civil Engineering, University of Illinois, Chicago, Chicago, IL, USA

ABSTRACT- Past research in our laboratory has demonstrated that cleanup of the entire sediment may not be necessary due to sequestration of the vast majority of hydrophobic pollutants like PAHs into a hydraulically-separable low density fraction. In 2001, PAH-contaminated sediments from the Indiana Harbor and Canal were hydraulically dredged by the USACE to evaluate the Eddy dredge system and characterize water treatment needs in the entrained water separated in a settling basin. This project provided an opportunity to test our hypothesis that a fortuitous segregation of sediments would occur via hydraulic settling processes in the settling basin. Following decommission of the basin, sediment cores were collected to depths of approximately 20 cm from ten locations in the basin immediately after dewatering. Samples were separated into low and high density fractions. The separated fractions were characterized for the contents of organic matter (OM), organic carbon (OC), soot carbon (SC), and PAH concentration. As expected, sediments collected along a transect of the basin showed a large decrease in bulk density with increasing distance from the dredge outfall. PAHs were highly correlated with the fraction of low density material in the sediment and concentrations were highest (above 1000 ppm) in sediments further from the outfall. In contrast, the sediment close to the outfall had almost no low density material and had PAH concentrations well below sediment quality criteria. These results provide support for the concept that hydraulic dredging can result in a fortuitous separation of contaminated sediment with high amounts of low density material and high PAH concentrations from sediment meeting sediment quality standards.

Key words: dredging, contaminated sediments