Characterization of Contaminated Sediments for Remediation Projects in Hamilton Harbour

Abstract

Hamilton Harbour is located on the western end of Lake Ontario and has an area of approximately 31 square kilometers. The harbour has been designated by the International Joint Commission (IJC) as one of the 42 Areas of Concern (AOCs) within the Great Lakes. Most fine-grained sediments in the harbour exceed sediment quality guidelines at the severe effect level due to contamination by both metals and organic compounds such as PAHs and PCBs. Current investigations are concentrated on two areas of the harbour called Randle Reef and Windermere Arm. The Randle Reef “hot spot” contains the most highly contaminated sediment for PAH concentrations in the harbour. Extensive information on sediment physical and chemical properties was collected by coring and offs hore boreholes. Bioassays were carried out to determine sediment toxicity. A range of remediation alternatives has been considered, including removal and ex situ treatment. The current preferred alternative is an enginee red containment facility (ECF), which will contain in situ contaminated sediments within the footprint of the structure. In addition, dredged sediment from other contaminated sites in the harbour will be placed in the ECF. Windermere Arm is a 50-ha narrow channel situated in the southeast portion of the harbour. Contamination in Windermere Arm is not as severe as that found in Randle Reef. Recent sediment surveys in the area, however, yielded higher PCB values in surficial sediments than previously reported. Sediments in Windermere Arm are also subject to considerable physical disturbance due to extensive ship traffic. For this reason, historical sediment contamination occurring in deeper sediments also has to be considered as a potential risk to the aquatic environment.