Persistent contaminants in Puget Sound: Overcoming a toxic legacy

The Lower Duwamish Waterway in Puget Sound was designated a Superfund cleanup site in 2001. Its legacy of contamination predates World War II and the waterway continues to pollute Puget Sound through stormwater runoff.

Lower Duwamish Waterway dredging on Superfund site. Photo: Gary Dean Austin (CC BY-SA 2.0)
Lower Duwamish Waterway dredging on Superfund site. Photo: Gary Dean Austin (CC BY-SA 2.0)

In 1945, as World War II was winding down, Richard Foster, an inspector with the Washington Pollution Control Commission, was sent to do a survey of the Duwamish-Green River drainage. He started at the mouth of the Duwamish River, which empties into Elliott Bay. From there he worked his way to the Upper Green River watershed, past the city of Auburn. His aim was to document all the pollution—from source to type to amount—that was making its way into the Duwamish River Basin.  

Foster didn’t have to go far to uncover the lion’s share of the mess. “The Duwamish Waterways within the City Limits of Seattle receives a larger volume and greater variety of polluting substances than all of the remaining watershed combined,” he would write near the beginning of the report he submitted at the end of the year. 

In all, Foster found 38 sources of pollution along the Lower Duwamish Waterway. These ranged from the Boeing Company’s two manufacturing plants, to various shipyards, to concrete companies, to Isaacson Iron Works, to a number of slaughterhouses. Similarly diverse were the things they dumped into the river: oil, chromic acid waste, raw sewage, offal, more than 1,400 lbs. per day of acetylene generator waste from some shipyards, and on and on. (“While it is recognized that, during the existing war emergency, speed in the repair of ships is vital, the extensive and continued spilling of oil into the West Waterway and Elliott Bay does not seem justified,” Foster observed.)

It was in part due to this toxic legacy that the Environmental Protection Agency (EPA) designated the Lower Duwamish Waterway a Superfund site in 2001. In November 2014, after more than 13 years, the agency released its Record of Decision—the final plan that outlined exactly how federal and state managers will oversee the cleansing of the river. The work is expected to take at least 17 years and will cost more than $340 million. 

One of the principal challenges facing the Duwamish cleanup has been, and will be, stormwater. Every year, millions of gallons of rain washes into the Duwamish from its surrounding neighborhoods, bearing with it loads of metals, petroleum products, fertilizers, and other toxins. At a session of the Salish Sea Ecosystem Conference in May 2014, Beth Schmoyer, from Seattle Public Utilities, talked about how difficult it is to trace the origins of this pollution, to say nothing of stopping it. “It’s really hard to control the source once you find it, and it’s really hard to find it,” she said. She pointed out that there are 237 sewage outfalls along the waterway, and 198 storm drains, and only a fraction of them are monitored. On top of that, over 100,000 metric tons of sediment enters the river every year from Auburn and Renton. That load is also rife with everything from motor oil to dog feces, but none of it is under the purview of Superfund legislation.

Still, even as Puget Sound residents have become its leading source of contemporary toxins, the chemical history from Seattle’s period of commercial growth remains a formidable obstacle. Since Foster’s work, government inspectors have detected more than 40 chemicals in the Lower Duwamish Waterway. The most harmful include dioxins and furans, arsenic, and polycyclic aromatic hydrocarbons (PAHs), all of which are byproducts of various industrial activities. But the most abundant pollutants by far are polychlorinated biphenyls, or PCBs. 

Inflammable, chemically stable and insulating, PCBs were considered a miracle compound for their wide range of commercial applications when they were developed in the 1880s. They were used to make caulking and grout and paint, they were in carbon paper, they were in floor finishes, tapes and other adhesives, cable insulation. At the time, no one thought anything was wrong with PCBs. (They are not mentioned at all in Foster’s report.) Now, of course, people know differently. Later research would reveal that PCBs cause cancer and birth defects. They suppress the immune system. Children with sustained exposure to them can develop learning disabilities or behavioral problems. Wildlife are also affected, especially those animals that are top-level consumers, such as seabirds or marine mammals. 

Congress would eventually ban PCB manufacture in 1979. But all the things that made them so useful for industry mean they are now extremely hard to remove from the environment. This is especially true on the Duwamish River. Around 2,300 buildings along the Duwamish corridor contain PCBs in one form or another. They are so widely integrated into the landscape that researchers can detect them in the droppings of Canada geese. 

Although to-date federal and state regulators have overseen extensive dredging and capping operations that have reduced the PCB load in sediments by 50%, in a sense, this was the easy work, concentrated as it was around five known hotspots. Now, dredges will have to get as much of the rest as possible, little of which is so conveniently centralized. Of the 412 acres within the boundaries of the waterway, the EPA will work to clean 177 of them. The rest—235 acres—will be left to what the EPA calls Monitored Natural Recovery. This means that EPA and state officials will watch and wait as the river goes about its daily business. They will trust the reduced flow of its deepened channel to carry the most dangerous sediments out to Elliott Bay, where the toxins will pose less of a risk; or bury them under a natural cap of fresher muds borne from the Green River, which itself is not much cleaner than the Duwamish. If all goes as intended, the level of PCBs in the river will drop by 90%.


About the Author: 
Eric Wagner is a freelance writer based in Seattle and co-author of the 2016 book "Once and Future River:Reclaiming the Duwamish," published by University of Washington Press.