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. We have developed land in a way that interrupts the natural water cycle for well over a century.

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. 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. 

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. 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.

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.

An aerial image of West Seattle, Harbor Island, the Duwamish River, and the Georgetown neighborhood of Seattle. The Duwamish River has two Superfund Sites due to legacy pollution from heavy industry and development along its banks. The river is home to wildlife, is culturally important to Indigenous people including the Duwamish Tribe, and provides recreation and sustenance to surroundings communities. Image via Google.

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, 6PPD-quinone and its source, and Soundkeeper’s work documenting coho mortality on Longfellow Creek in Seattle.) 

A coho salmon dying from URMS
A coho salmon in West Seattle’s Longfellow Creek can be seen dying from Urban Runoff Mortality Syndrome (URMS). Salmon die after contact with toxic stormwater, specifically the chemical 6PPD-quinone, and are unable to spawn.

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 like sickness or weakness. Salmon are an integral part of the lifeways and cultures of the Pacific Northwest. Ongoing harm to salmon due to polluted stormwater is an environmental injustice to the many tribal, Indigenous, and other peoples that fish and eat salmon as part of their culture. We know that filtering polluted stormwater using biofiltration can remove toxic pollutants, including 6PPD-quinone, and save coho salmon. 

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