Washington State Department of Transportation
 Washington State Ferries
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Eelgrass Protection Project
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Innovative Eelgrass Protection Project A Huge Success
Amy Borde of Battelle Marine Sciences Laboratory prepares eelgrass for transplanting underneath the new Clinton ferry dock.
A combination of innovative thinking and careful planning has resulted in a successful eelgrass restoration project at the Clinton ferry terminal. The Washington State Department of Transportation (WSDOT) / Washington State Ferries (WSF), working with scientists from the Battelle Marine Sciences Laboratory and the University of Washington initiated a project that accommodates future transportation needs while taking into account the needs of nearshore eelgrass populations. Eelgrass populations are essential for the survival of endangered salmon and a variety of other marine species.

The Situation
A view of the Clinton ferry dock before the reconstruction project. The glass blocks were later installed above the area shown here.
In 1994, WSF determined that the ferry terminal at Clinton needed to be expanded - and the entire dock reconstructed - to accommodate increasing service demands. The conventional approach to dock expansion would involve simply widening the dock to accommodate more traffic. However, the original design would have resulted in the loss of approximately 10,280 square feet of eelgrass. WSF saw this potential consequence as an opportunity to gain a comprehensive understanding of the impacts of ferries and ferry terminals on eelgrass that would help with future projects as well.

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
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.

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:

  • Glass blocks were installed in the passenger walkway. Glass blocks were installed in the pedestrian walkway to let light through to the eelgrass beds. This action reduced the impact to 2,640 square feet of eelgrass habitat.
  • The trestle was narrowed and the loading slips moved further offshore. The ferry slips were moved further offshore to minimize the impact from ferry propeller wash on the eelgrass beds. By lengthening the dock, it was narrowed considerably from the original design to minimize the shading effect on the adjacent eelgrass in the shallower water. These design modifications avoided impact to approximately 2,130 square feet of eelgrass.
  • An existing fishing pier and float were moved offshore. A private fishing pier and float were also moved offshore to eliminate shading, avoiding an additional 2,000 square feet of eelgrass habitat.
  • The underside of the dock was painted. As an experiment, WSF agreed to paint the underside of the new dock in certain areas with highly reflective white paint. The paint should reflect any light that reaches under the dock, increasing light to the eelgrass beds.
  • Native eelgrass was stockpiled. Beginning in 1997, divers removed about 6,500 eelgrass shoots from the future construction site and put them in special seawater tanks for cultivation. Within two years, the number of shoots had more than tripled.
  • Artificial rock habitat was constructed. Brown macroalgae (better known as seaweed) is used by rock fish as feeding and resting habitat. While not a significant loss, this resource was also impacted by the dock expansion project. WSF constructed a rock "mound" as an area for brown macroalgae to colonize, resulting in rock fish habitat to compensate for the loss of the existing seaweed.
    • Results And Next Steps
    John Southard and Sue Blanton of Battelle Marine Sciences Laboratory harvest eelgrass for replanting underneath the new Clinton ferry dock.
    Battelle divers just replanted 11,000 eelgrass shoots at the Clinton dock site, the third of four transplanting efforts scheduled for the project. When the planting was finished, the recently barren area had turned into row upon row of green grasses swaying in the surf. Curious surf perch and crabs inspected the new plants soon after the divers swam out of the way.

    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.

    A view of the Clinton dock after completion of Phase I reconstruction.

    Aerial Photos

    Aerial Photo During Phase I - 1999
    Clinton Terminal during Phase I construction which widened the dock.


    Aerial Photo After Phase I - 2000
    Clinton Terminal at the completion of Phase I.
    Complete build-out of the dock to be finished in 2003.