Paper D-39, in: E.A. Foote and A.K. Bullard (Conference Chairs), Remediation of Contaminated Sediments—2011. Sixth International Conference on Remediation of Contaminated Sediments (New Orleans, LA; February 7–10, 2011). ISBN 978-0-9819730-3-6, Battelle Memorial Institute, Columbus, OH. www.battelle.org/sedimentscon Piers 24 & 25 Marine Sediment Remediation Challenges and Solutions, Tacoma, Washington Richard F. Moore (
[email protected]) and Gary E. Horvitz (Hart Crowser, Seattle, Washington, USA) William D. Evans (
[email protected]) (Port of Tacoma, Tacoma, Washington) ABSTRACT: The Port of Tacoma completed a multiphase marine construction project between October 2007 and February 2008 to remediate approximately 3 acres (1.21 hectares) of contaminated intertidal and subtidal sediments along rocky marine shoreline areas. The sediments were near the mouth of the Hylebos Waterway and in a portion of Com- mencement Bay in Tacoma, Washington. The work was completed as a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) lead project. Sediments were contaminated with metals, polychlorinated biphenyls (PCBs), and poly- cyclic aromatic hydrocarbons (PAHs) associated with historical shipyard operation, vessel repair, and related marine activities. Remediation included removal of fused metallic debris piles from intertidal and subtidal embankment slopes, followed by difficult under- pier capping, subtidal dredging, and embankment excavation. Construction was compli- cated by limited access to under-pier work areas, winter tidal conditions, and embank- ment stability concerns. Construction also required coordination with concurrent pier repair and piling replacement work during much of the project. Adaptive engineering and construction approaches succeeded in overcoming these challenges, leading to the achievement of project regulatory and design goals.