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Pollutants
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%.
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