The Port of Tacoma has begun dredging contaminated sediments in Blair Waterway in preparation to expand Pier 4, which is located within the major South Puget Sound waterway of Commencement Bay.
The work became necessary after the port detected a marine biocide, called tributyltin, while completing a dredging inspection for the site evaluation to expand Pier 4 for larger ships. The Port of Tacoma has agreed to complete the cleanup of the sediments, which the US Environmental Protection Agency will oversee.
The dredging work began September 15th.
The port plans to dredge an additional 500,000 cubic yards of clean sediment to make the base of the pier deeper as part of the pier expansion.
“In an effort to contain costs and remain competitive, shipping lines are increasing the size of the container ships, providing economies of scale. The planned upgrades to Pier 4 will allow Husky Terminal to handle two of the world’s largest ships simultaneously,” Port of Tacoma Commission President Don Johnson said. “An estimated 1,500 jobs in Washington State are connected to the movement of cargo through Husky Terminal. These berth improvements will add capacity, creating the demand for additional family-wage jobs in the region.”
A 2013 investigation performed by the Port of Tacoma showed that the fill material used to create the bulkhead under Pier 4 was contaminated with TBT.
Developed to be toxic to aquatic life, TBT is a marine biocide, commonly added to ship paint to prevent mollusks from sticking onto vessels and other objects that contain the chemical. EPA canceled all TBT antifouling paint product registrations in December of 2005.
The port removed the Pier 4 deck and pilings between May and August and plans to dredge about 40,000 cubic yards of contaminated sediments. The contaminated sediments are to be dewatered and trucked to a waste disposal facility. The Superfund phase of the work is expected to be finished by April of 2016 at an overall cost of $19.3 million.
Once the contamination extraction is complete, the Port of Tacoma begins the second phase of the Blair Waterway extraction and reconstruction, which includes additional piling removal, deck demolition, dredging and reconfiguration of the existing pier.