Projects & Programs
Dock Design to Facilitate the Restoration of Eelgrass in Port Townsend Bay, Washington
The derelict Thomas Oil Dock on state tidelands in Port Townsend, Washington was redesigned for the Northwest Maritime Center by a committee including marine scientists, architects, engineers, educators, regulators and user groups. The committee's objectives were to create a "demonstration dock" using the best-available technologies and design features to restore nearshore habitat functions, particularly for threatened fisheries resources, while accommodating the unique requirements of the educational facility to house vessels ranging from historic tall ships to sea kayaks. A key nearshore habitat restoration goal was to reduce fragmentation of eelgrass where shade from the existing dock inhibited growth, by improving conditions with a new dock design and transplanting eelgrass to connect existing patches. Ecological conditions were evaluated through diver surveys; mapping existing eelgrass, macroalgae, and substrates; and review of controlling factors. Data on the attenuation and diffusion of photosynthetically active radiation (PAR) were collected and evaluated relative to eelgrass light requirements. Potential shade impacts of existing and alternative dock designs and materials were modeled.
Key design features to improve habitat functions included the following:
- Installation of reflective material under the dock to increase the incidence of PAR at the substrate level
- Reduction in the number of piles and associated shade impacts through the use of steel piles instead of wood
- Increase in the length of the trestle to 286 feet to move the greatest area of overwater structure beyond the depth range of eelgrass
- Reorientation of a platform to minimize shading
- Use of grating in strategic locations to reduce the potential of a light/dark barrier to fish passage.
In May 2004, 5,000 eelgrass plants were planted underneath and alongside the dock; they are currently being monitored by research scientists and local high school students to test the effectiveness of the design.
This project was performed by Sequim Marine Research Operations at Pacific Northwest National Laboratory, Sequim, Washington; NOAA National Marine Fisheries Service, Damage Assessment and Restoration Center, Seattle, Washington; Miller/Hull, Seattle, Washington; Peratrovich, Nottingham & Drage, Inc., Seattle, Washington; and Northwest Maritime Center, Port Townsend, Washington.
This project has received the Technology Merit Award from the Environmental Business Journal and the Waterfront Center's Environmental Protection and Enhancement Award.