Water Quality Improvement Project
Commencement Bay Area:


Commencement Bay is part of Puget Sound, located within the city of Tacoma, Washington. The bay got its name from Lieutenant Charles Wilkes of the United States Exploring Expedition in 1841. Wilkes chose the name because it was the place from which he “commenced” a scientific exploration of southern Puget Sound. Commencement Bay’s development took off in the 1880s when the Northern Pacific Railway made the site the western terminus of the first trans-continental rail line in the northern United States. With both a seaport and railroad, Commencement Bay and Tacoma became a hub of industry and transportation for the Pacific Northwest. The Puyallup River, Ruston Creek, Mason Creek, Asarco Creek, Puget Creek, Hylebos Creek, and Wapato Creek drain into Commencement Bay. Of these freshwater waterbodies, the Puyallup River is the largest.

Water quality issues

In June 1989, the Washington State Department of Ecology (Ecology) found the Simpson-Tacoma pulp mill was discharging dioxin into inner Commencement Bay.

Why this matters

Dioxins are common by-products of a number of human and natural activities. These activities include combustion and incineration, forest fires, chlorine bleaching of pulp and paper, certain types of chemical manufacturing and processing, and other industrial processes. Dioxins are a concern because they are toxic contaminants that last a long time in the environment and can build-up in aquatic organisms, becoming more concentrated as they move through the food chain.

Status of the project

Ecology submitted a total maximum daily load (TMDL) to EPA for approval. EPA approved the TMDL on June 18, 1992. The TMDL set a wasteload allocation (WLA) for the amount of dioxin that the Simpson Mill at Tacoma could discharge. The WLA was incorporated into the pulp mill's NPDES permit, issued June 1991. As part of implementing the TMDL, Simpson mill was required to monitor how much dioxin continued to be found in several kinds of fish and shellfish in the area.

Technical information

Commencement Bay (Inner) Total Maximum Daily Load (Ecology publication)

Related information

Urban Waters Initiative: Commencement Bay (Ecology web site)

Washington's Urban Waters Initiative: A Focus on Commencement Bay (Ecology publication)

Focus Sheet: Hazards of Dioxins (Ecology publication)

Dioxins and their effect on human health (World Health Organization fact sheet)

WRIA 10: Puyallup-White Watershed Information (Water web site)


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Last updated November 2015
  Map for water resource inventory area (WRIA) 10, Washington State.


WRIA: #10 (Puyallup-White)
County: Pierce

Water-body Name:
Commencement Bay


# of TMDLs: 1

Approved by EPA

Contact Info:
Donovan Gray
Phone: 360-407-6407
Email: Donovan.Gray@ecy.wa.gov

Southwest Region
Department of Ecology
P.O. Box 47775
Olympia, WA 98504-7775