July 12, 2001

Mitigation banks balance habitat, development

Hart Crowser

Union Slough
Photo courtesy of Pentec
The triangular portion to the left of Union Slough, shown before the project, was turned into 12 acres of marsh and mudflat habitat.

Imagine that you are a port planner, responsible for broadening and strengthening the area’s economic base. Now imagine that you are a member of an environmental group or a concerned citizen who wants to protect habitat for endangered species. How is it possible to link these seemingly disparate agendas?

Economic development and habitat protection seem to be mutually exclusive. But are they? The Union Slough project illustrates how mitigation banking has allowed development, yet has also increased and improved local habitat.


Using this approach, the Port of Everett will apply 12 acres of newly created marsh and mudflat habitat in the Snohomish estuary as mitigation for the loss of 9.4 acres of industrially disturbed shallow water habitat in Everett Harbor. The remaining acreage in the 19-acre site will be jointly administered as a mitigation bank by the port and the Washington State Department of Ecology.

“This strategy is a win-win-win for the fish, the port, and the regulatory agencies involved,” said Graham Anderson, environmental planner for the Port of Everett.

“Mitigation banking allows us to take a more comprehensive look at the impacts of planned and future projects and to plan accordingly,” Anderson said. “Then we can build one large mitigation project, which is much more cost-effective for us than mitigating project-by-project. The fish get large contiguous areas added to the estuarine habitat, providing them good habitat to use before there’s a loss of habitat elsewhere. And it is easier for regulators because it is coordinated with the regional plan.”

In recent years, changing regional needs have pushed the Port of Everett to expand. Before the 1980s, logs were the port’s primary cargo. The port had 10 berths, with no long-term leases, which meant sufficient access for shippers. Then the Navy bought five of the port’s berthing spaces. By the 1990s, logging had slowed down, and the port had committed to long-term leases at its remaining berths. In addition, none of these berths could accommodate the large ships with specialized shipping containers used by the Boeing Co. to ship 747 parts to its Everett plant. Instead, the parts needed to be offloaded in Seattle or Tacoma and barged to Everett.

No doubt, the port needed to expand. At the same time, it needed to dredge existing berths and dispose of the sediment. A part of this sediment was contaminated, and disposal on land would have cost about $100 a cubic yard. For much less, about $30 a cubic yard, the port could use the sediments as a nearshore fill, which it could then use for development of a container terminal.

So where does the benefit to the environment come in?

The area proposed for the terminal had been used for industrial purposes for the last 90 years and was formerly a log pond. The port asked its environmental consultant, Pentec Environmental (the natural resources division of Hart Crowser) to evaluate the area, and monitoring showed that it had marginal value as habitat. The first environmental benefit from the project was the voluntary cleanup of 10 acres of contaminated bottom area in the harbor. In addition, mitigation banking allowed conversion of the contaminated sediment disposal area to productive economic use, while creating a larger replacement habitat in another area that would serve as a better habitat, with much higher value to fish wildlife.

Large areas near Union Slough, a major distributary channel of the Snohomish River, had been diked early in the 20th century for use as farmland. Subsequently, more than 2,000 acres of this farmland have been abandoned and have naturally returned to their original state as marshland. Studies have shown these areas support high use by wildlife and anadromous fish. The port reasoned that reclaiming similar land would not only be easier, but more likely to be successful than other mitigation options.

The port identified a 32-acre parcel near Union Slough that was formerly farmland, but zoned for industrial use. It was owned by a developer that had received permitting approval to fill in the land for development. The port bought the property in 1991 for about $1 million.

Working with Pentec Environmental and Reid Middleton, the port developed a 19-acre salt marsh on the property. A number of channels were first dug in the property to maximize the benefits and feeding opportunities the site would provide for salmon. To ensure that the habitat would support salmon, it was important to plant appropriate vegetation along the banks of the dike. To accomplish this, Pentec staff members donated their time, and the Port of Everett donated plants and staff time. Weyerhaeuser also donated 150 fir trees, which a girls’ soccer team (the Shooting Stars) and their families planted all in one day.

“We learned a lot about creating wetlands,” said Jack Olson, director of engineering at the port. “Two factors—a very resourceful contractor, Grade Inc., and a dry winter—were critical to the process. Tracked dump trucks were used to move the unstable material, and a track hoe with a 70-foot boom was necessary for the dike breach operation. We are pleased with the results.”

Ironically, although permits for this project had been issued several years ago, final approval for construction was held up for a year because of backlog from the listing of salmon species under the Endangered Species Act. Because the port’s intention was to create a mitigation site concurrent with construction of the container terminal, they negotiated to restrict intertidal log raft storage on Jetty Island as an interim mitigation action. Removing log rafts was expected to immediately enhance habitat for eelgrass, birds, crab and fish so that there would be no interim loss of habitat function while the Union Slough project was being restored.

By Feb. 6, preparation of the Union Slough site was complete. The next step was to breach the dike, which would allow the tide to ebb and flow in the new wetland for the first time in nearly a century. Two months later, proof of the project’s initial success came in the form of hundreds of juvenile salmon feeding in the area on their way to the ocean. Use by waterfowl and shorebirds has also been documented already, and marsh plants are beginning to colonize the newly created habitat.

As noted above, 12 acres of the newly created habitat has been applied toward the loss of habitat from construction of the new container terminal. The remaining 7 acres will be applied toward future projects under Washington state’s new mitigation banking guidelines. Pentec Environmental will conduct a long-term monitoring program to quantify the benefits of the Union Slough habitat for salmon, shore birds, waterfowl and crab.

Susan Kemp is a senior marketing specialist with Hart Crowser.

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