Publication Summary

Settling particulate matter (SPM) was collected with moored sediment traps in the vicinity of Piers 62/63 along the Seattle Waterfront to evaluate whether piling replacement activities were redistributing contaminated bottom sediments onto an adjacent sediment cap.

Settling particulate matter (SPM) was collected with moored sediment traps in the vicinity of Piers 62/63 along the Seattle Waterfront to evaluate whether piling replacement activities were redistributing contaminated bottom sediments onto an adjacent sediment cap.

The data collected seem to indicate that contaminated bottom sediments were being resuspended in a localized area immediately adjacent to the Pier 62/63 construction site. There were some indications (primarily sediment standard exceedances for low molecular weight polynuclear aromatic hydrocarbons LPAH)) that a portion of this material was reaching a sediment cap located to the north. However, given the magnitude of the sediment standard exceedances on the sediment cap and the short-term duration of the piling replacement project, it does not appear that long-term recontamination of the cap would be expected to occur. A relatively rapid reduction in LPAH levels is also expected due to weathering processes.

The data collected suggest that the use of piling jetting is an acceptable technique for replacement or repair of in-water pilings provided the size and duration of the project is appropriate for the surrounding conditions. Some pre-existing information on the contaminants of concern in the construction area is also desirable.