If you live in an area that gets a lot of rain, you’ve probably heard that stormwater is not good for water quality. The Washington State Department of Ecology tags stormwater, or the chemical soup of pollutants that we’re all responsible for creating, as the leading contributor to poor water quality in urban regions. But just how toxic is the stuff?

The work of Jennifer McIntyre, a post-doc researcher at Washington State University, helps put the toxicity of stormwater into perspective. McIntyre and a team of researchers from NOAA and U.S. Fish and Wildlife Service recently conducted a simple experiment that revealed stormwater’s frightening toxicity. The team exposed healthy adult coho spawners to undiluted road runoff. All of the fish exposed to this runoff died, and they died quickly. As the study, recently published in The Journal of Applied Ecology, notes, “All of the exposed fish were either symptomatic or dead within 4 hours.” Those that didn’t die initially were dead within 24 hours.

McIntyre’s work also points the way toward a profoundly simple solution. As part of the same experiment, her team exposed another set of salmon to stormwater filtered through soil columns. These fish all survived and showed no behavioral symptoms of effects at either four hours or 24 hours. On the surface, such results may seem predictable. Stormwater kills fish. Filtered stormwater, removed of its pollutants, doesn’t. So what?

Though research has yet to pinpoint the chemicals in stormwater responsible for fish die-offs, knowing the lethal effect that stormwater has on a sentinel and symbolic fish like salmon adds urgency to the need for a fix. If we want to live in a world with coho then we need to figure out better ways to merge our habitats. Encouragingly, the above study suggests that filtration solutions can be structurally simple and inexpensive. Dirt alone can do the trick.

As the study states: “Our results are the first direct evidence that: 1) Toxic runoff is killing adult coho salmon in urban watersheds, and 2) Inexpensive mitigation measures can improve water quality and promote salmon survival.”

Solving the stormwater problem is daunting because of the scale of the problem. In the Puget Sound, for example, one acre of pavement can generate a million gallons of stormwater each year.

Greener municipal development laws and programs promoting raingarden installations are good starts to re-greening our concrete environments. But how much soil, or how many raingardens, will it take to properly filter the runoff from just one ribbon of highway running round or through a city? How can we begin to prevent or filter pollutants at a scale that actually gives fish a chance?


-Cyrus Philbrick


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