Stormwater is the biggest source of toxic pollution to Puget Sound. Studies by the Washington Department of Ecology show that 75% of the toxic chemicals entering Puget Sound are carried by stormwater runoff flowing off hard, developed surfaces and into our waterways. This pollution impacts our environment, economy, and health. To protect our region’s salmon, orcas, and communities, we must stop stormwater pollution now. 

How Does Stormwater Cause Problems?

Stormwater itself is not a problem—our pollution and development is. When rain falls on forests, grass, and mountains, the soil soaks it up. Plant roots hold the soil in place, and the rainwater slowly filters into streams, creeks, and rivers. For over a century, we’ve developed land in a way that interrupts the natural water cycle. At the same time, we discharge pollution into the environment from many sources, including our lawns, vehicles, farms, and trash, which can accumulate on these hard surfaces.

Paved surfaces and hard rooftops give rainwater nowhere to go. Stormwater runoff in developed areas carries pollution it picks up along the way, rushing downhill or pooling in depressions instead of filtering slowly through the earth. This type of development causes impacts like flooding in denser communities, sewage overflows, and salmon die-offs in poisoned urban creeks. 

The problem is not unique to Washington: polluted stormwater runoff is one of the biggest water pollution threats in the Northwest and across the nation. Stormwater sweeps across pavement, collecting contaminants: motor oil, pesticides, pet and livestock waste, trash, and more. Then it travels through pipes and storm drains, dumping this polluted soup straight into lakes, rivers, and other waterways. 

Denser communities are particularly affected, despite a network of drainage systems. During heavy rains, flooding can close roads and damage property, or incapacitate public utilities. Pollution from combined stormwater and sewage overflows can cause swimming beach closures and make it unsafe to catch and eat local fish and shellfish.

Effects On Our Communities

Pollution disproportionately impacts communities of color, low-income communities, and Indigenous communities. Research shows that here in Washington, these communities bear the burdens of increased disease, shorter lifespans, and poorer life outcomes as a result of systemic injustices including disproportionate exposure to pollution.

Polluted stormwater also endangers the other creatures that call this place home. Toxic pollution can detrimentally affect the entire food web, from tiny benthic macroinvertebrates to Southern Resident Orcas. Salmon, an emblematic Northwest species, suffer horrifically when encountering polluted stormwater. Seattle residents can witness salmon gasping and struggling in urban streams when they should be spawning.   

Coho salmon are particularly sensitive, and polluted stormwater runoff from a major arterial road can kill adult coho salmon in as little as three hours. Contamination from chemicals in car tires washes into creeks and streams with stormwater, posing a unique threat to urban creeks and the returning salmon. The tire chemical, 6PPD-quinone, can kill Coho salmon before they have a chance to reproduce. Other Persistent Organic Pollutants that enter stormwater can bioaccumulate in the fatty tissue of salmon and other creatures and biomagnify in the creatures that consume them: increasing in concentration up the food chain. (Read more about salmon and stormwater.

Species of salmon and other aquatic life that do not immediately die due to exposure to toxic stormwater can be harmed, as they can suffer from sub-lethal effects, becoming sick or weak. Salmon are an integral part of the lifeways and cultures of the Pacific Northwest. The ongoing harm to these species caused by pollution is an environmental injustice to the many tribal, Indigenous, and other peoples that fish and eat salmon as part of their culture. Yet we know that filtering polluted stormwater using biofiltration can remove toxic pollutants, including 6PPD-quinone, and save Coho. 

Incorporating green solutions into urban infrastructure to prevent pollution, protect and restore ecosystems, and prevent urban flooding is essential.