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Amy Borde of Battelle Marine Sciences Laboratory prepares eelgrass for transplanting underneath the new Clinton ferry dock. |
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A view of the Clinton ferry dock before the reconstruction project. The glass blocks were later installed above the area shown here. |
WSF contracted with the University of Washington (UW) School of Fisheries' Wetland Ecosystem Team (WET) laboratory to develop a quantitative understanding of how ferry docks impact eelgrass and how to minimize these impacts.
Ferries and ferry terminals impact eelgrass in a number of ways. First, eelgrass needs light to survive, so any overwater structure that reduces light is a problem. Secondly, the propeller wash from the boats themselves can erode eelgrass and kick up silt and fine-grained sediment that reduces light.
The primary goal of the research was to ensure that there would be no net loss of eelgrass on the Clinton terminal expansion project. Additionally, researchers set out to evaluate new concepts in mitigating the direct and indirect shading effects of overwater structures. The research team was awarded an Environmental Excellence Award from the Federal Highway Administration. The award was given in 1997 for Excellence in Environmental Research.
The Innovations
Based on recommendations from the scientific team, WSDOT/WSF took the following actions to minimize the impact of the new dock on the eelgrass beds beneath it:
The researchers from Battelle and the UW worked directly with WSF Terminal Design engineers on a new dock design that would avoid and minimize the impact on eelgrass. As a result of this unique partnership, the final permitted design impacted only 3,444 square feet of eelgrass habitat, a significant reduction from the 10,280 square feet contemplated in the original design.
Two views of the glass blocks in the passenger walkway at the Clinton ferry dock. The blocks let sunlight through to the eelgrass beds below the dock.
Results And Next Steps
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John Southard and Sue Blanton of Battelle Marine Sciences Laboratory harvest eelgrass for replanting underneath the new Clinton ferry dock. |
At this time, a total of 14,230 square feet of eelgrass has been successfully transplanted around the Clinton ferry dock. One of the transplanted plots lies directly underneath the glass blocks of the pedestrian walkway.
So far, the project has expanded the area of eelgrass beds around the Clinton ferry dock and increased the total number of shoots as compared with pre-dock construction. In general, the transplanted eelgrass beds appear to be healthy and are becoming indistinguishable from the surrounding eelgrass beds.
The remainder of stockpiled shoots will be transplanted when dock construction is completed and the eelgrass will be monitored quarterly.
WSF and Battelle continue to research methods of minimizing shading from overwater structures. They are experimenting with deck prisms and Solar Tubes at a dock in Port Townsend.
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A view of the Clinton dock after completion of Phase I reconstruction. |
