Formatted Title:

Habitat Restoration within Two Seattle Superfund Sites

Background/Objectives:

As part of the Port of Seattle’s (Port) Century Agenda, the Port has a goal to become the greenest and most energy-efficient port in North America. One of the key goals is to restore, create, and enhance 40 additional acres of habitat along the Green‑Duwamish River, which overlaps with two adjacent Superfund sites. The Port completed construction of the Duwamish River People's Park and Shoreline Habitat (DRPPSH; formerly Terminal 117) project in 2022, which is within the Lower Duwamish Waterway (LDW) Superfund site. The Port is currently designing the Terminal 25 South habitat restoration project along the East Waterway, which is within the Harbor Island Superfund site. Both projects are intended to generate credits that can be used to fulfill settlement requirements under the Natural Resources Damage Assessment (NRDA) program through upland fill removal and creation of marsh habitat. At DRPPSH, 14 acres of tidal marsh and riparian buffer habitat were restored with the goal of improving habitat for Chinook salmon (Oncorhynchus tshawytscha) and other imperiled species along 2,000 feet of the Duwamish River shoreline. Public access has also been incorporated into the project, with two observation platforms, trails, and educational signage. At Terminal 25 South, 10 acres of tidal marsh and riparian buffer habitat are planned for restoration to support similar species recovery goals. Both sites have been identified by local, state, tribal, and federal officials as high-priority habitat restoration areas that will benefit listed species for decades to come.

Approach/Activities:

The process to restore habitat in a Superfund site presents many challenges. Habitat creation in an urban area with an industrial history inevitably involves expensive solutions to address contamination prior to habitat construction. Both sites were selected as early action sites by the U.S. Environmental Protection Agency (USEPA) within their respective Superfund sites, requiring extensive investigation and evaluation of cleanup alternatives as part of an Engineering Evaluation/Cost Analysis (EE/CA). Construction for DRPPSH was conducted in two phases, with early-action cleanup completed in 2014 prior to issuance of the LDW Record of Decision (ROD) and restoration completed from 2020 to 2022. Terminal 25 South is planned to be constructed in a single phase in the next few years after issuance of the East Waterway Interim ROD, with early-action cleanup conducted prior to restoration as part of the same mobilization.

Results/Lessons Learned:

Both projects required evaluation of potential recontamination because the larger Superfund cleanups will occur after restoration and adjacent to the restoration sites. Concerns of recontamination resulted in additional construction and contingency measures when performing final cleanup adjacent to DRPPSH. Terminal 25 South oversight is complicated by cleanup levels required by USEPA that differ from cleanup levels required by NRDA Trustees, requiring more agency coordination and design evaluations. DRPPSH restoration construction included confirmatory testing during construction that required additional removal of contaminated soil to support Superfund sediment cleanup goals. DRPPSH monitoring has been extensive and complex due to overlapping regulatory oversight, including 8 years of contaminant monitoring following cleanup overseen by USEPA and 2 years of habitat monitoring required by NRDA Trustees. DRPPSH cleanup monitoring is expected to be integrated into the larger LDW Superfund monitoring program following cleanup completion in 2026.

Michelle Havey

Affiliation

Refine Results

Habitat Restoration within Two Seattle Superfund Sites