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October 5, 2006

Park work restores link to the lake

  • After a century, former industrial site will regain a natural shoreline
    Shannon & Wilson



    It is a vibrant time in South Lake Union these days with condos coming online, the promise of the streetcar and, in the center of all this, the development of South Lake Union Park.

    One look at the site today and it is clear there is work to be done: invasive blackberry bushes snarl the shoreline, the aging bulkhead is in need of replacement, and weathered pilings jut out to create both a visual and physical barrier between the land and the water.

    These old pilings hint at the history. Here is where the old Western Mill churned out sawdust that was used to fill the lake and where coal was hauled before being shipped to California. This former industrial site will now be central to the revitalization of the neighborhood.

    There have been many hopes and dreams for this land over the last 100 years, and so it is not surprising there are many stakeholders who have a vested interest in how the land is developed. Early stakeholder involvement was paramount to moving this project forward.

    A regional park

    Photo courtesy of Shannon & Wilson
    Shoreline restoration work at South Lake Union Park will include removal of 200 wood pilings, which give cover to fish that feed on endangered salmon.

    South Lake Union Park will be a regional venue that supports large civic events and community celebrations.

    The development of the park pays homage to the history enacted within its confines. The armory building, for example, will remain part of the park, offering a potential site for the Museum of History and Industry. The maritime tradition will be represented by the Center for Wooden Boats, a model boat pond, a boat carving shed and a beach for launching small watercraft.

    This will give people improved access to the lake. Even the new bulkhead will provide a place for people to moor small crafts. Walking paths will provide beautiful views, and the new shoreline improvements will reconnect the lake to the land.

    Replacing the bulkhead

    Plans for the park include a variety of elements designed to improve the structural integrity of existing facilities. Foremost among these plans is replacing the bulkhead in order to ensure the integrity of the existing terrestrial area.

    The bulkhead will be replaced about 6 feet landward of its current alignment and constructed of steel sheet piles. By moving the bulkhead landward, it will return approximately 2,800 square feet of aquatic habitat to the south shore of Lake Union.

    Protecting species

    A key component in designing the park has been finding the right balance between restoring it to a natural setting and creating a functional space to support public events.

    Because of the historical industrial use, when the park is finished it will be the first time in over a century that there is a natural shoreline planted with native species at South Lake Union. This is good news not only for park users but also for the endangered and sensitive species.

    The shoreline along South Lake Union is a segment of the migration corridor for endangered salmon as they move from the ocean to Lake Washington towards freshwater streams. Juvenile salmon, in particular, hug the shoreline for safety as they travel.

    The current dilapidated conditions along the shoreline at South Lake Union Park — porous riprap and broken-down dock sections — create perfect cover for largemouth bass, salmon’s most dangerous predator. The bass hide in the nooks and shadows of the old pilings and ambush the salmon as they pass.

    Approximately 200 wood piles, some of which are treated with creosote, will be removed along with other deleterious material.

    The aquatic portions of the shoreline located below high water will be covered with fish mix, a blend of sand and gravel designed to prevent spawning of bass and other freshwater predators. This will eliminate predator hiding places and provide substantial protection to the salmon as they migrate through the park, and significantly improve the existing near-shore habitat.

    Improving water quality

    Currently, stormwater runoff from all of the surfaces in the park flow into the lake without being filtered or treated, increasing pollution levels in the lake.

    Improvements as part of the park plan will result in a net decrease of 80,000 square feet of pollution-generating impervious surface. Impervious area for the site will be reduced from 2.84 acres of untreated impervious surface to 2.61 acres of treated impervious surface.

    The reduction of pollutants to the lake is one step toward helping the salmon survive in a harsh urban environment.

    Restoring the shoreline

    The existing shoreline is generally a steep embankment consisting of concrete and riprap that is dominated by invasive nonnative plants such as blackberries.

    During the construction of the park, invasive plants will be removed and the western shoreline will be regraded to have a more gradual slope.

    These improvements have numerous benefits. The enhancement of the vegetative diversity along the shoreline will provide greater structural diversity, native plant richness and high-quality habitat for birds, small mammals and amphibians utilizing the area. Overhanging vegetation will also provide shade to the shallower waters of the lake, helping to cool the water for migrating fish.

    Looking ahead

    The proposed park and associated restoration of the shoreline will reconnect the residents with the water, enhance a beautiful view and provide better opportunities for community activities. Equally important, it will increase the habitat suitability for native species.

    It is anticipated that improving the quality of the habitat will promote the recruitment and retention of native fish and wildlife species. The project will provide a gain in natural shoreline where none existed, and effectively remove the barriers that have separated the land from the lake.

    Katie Walter is the natural resource manager and Ryan Irwin is a marketing coordinator at Shannon & Wilson.

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