Sediment Cleanup in the Lower Duwamish Waterway

Farallon coordinates non-time-critical removal action at an early action area in the Lower Duwamish Waterway Superfund site

Farallon negotiated with EPA and developed scopes of work for conducting an Engineering Evaluation/Cost Analysis (EE/CA), Removal Design, and Removal Action for cleaning up nearshore sediments and the shoreline bank in an Early Action Area of the Lower Duwamish Waterway (LDW) Superfund site.  The work was conducted on behalf of former property owner Earle M. Jorgensen Company under an Administrative Order on Consent with EPA.  An EE/CA was performed to evaluate possible alternatives for cleanup of sediment and associated bank soil adjacent to the LDW.  The cleanup alternative selected by EPA was complete removal of the lateral and vertical extents of sediments and associated shoreline bank soils containing polychlorinated biphenyls and metals. 

The cleanup action was performed as a Non-Time-Critical Removal Action (NTCRA).  Construction was completed in July through September 2014 and included removal of contaminated sediments and associated shoreline bank soils, followed by placement of clean backfill and shoreline containment.  Measures to protect the environment during the NTCRA included water quality monitoring, installation of a coffer dam, use of a silt curtain, and operation of a water treatment system for barge return water.  Farallon conducted extensive coordination with EPA, Native American tribes, and other stakeholders and the public during the project.  Sediments, stormwater, and groundwater monitoring is currently being performed for 10 years to assess concentration trends in surface sediments and potential sources of recontamination, both in-water and upland.