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The Secrets of Stormwater

aerial map view of Seattle with waterways
Impervious surfaces cover the land and increases runoff and pollution. Google Maps.

There’s a dirty little secret about the Salish Sea that everyone should know – it’s not as clean as it looks. An invisible toxic mix of chemicals, oil, fertilizers, pesticides, bacteria, heavy metals, and more, are delivered directly to the sea from our stormwater runoff. These toxins pollute the water, close beaches and shellfish beds, and can enter the food web, accumulating in fish, seals, and whales.

What exactly is stormwater? Stormwater is simply rain or snow melt that flows across land to a ditch, stream, or stormwater conveyance (such as a pipe or a catchbasin) and into a surface water body such as the Puget Sound.

Large metal pipe with water discharging.
Polluted runoff gets to the water from through pipes like this one.

When the land is covered with impervious surfaces such as roads, parking lots, and buildings,  instead of soaking into the ground, the stormwater runs off the surface. Stormwater picks up everything in its path including oil and other fluids from leaky cars, PAH’s (polycyclic aromatic hydrocarbons) from car exhaust, copper from car brake linings, zinc from tires and some roofing material, PCBs (polychlorinated biphenyls) a banned chemical, bacteria (from pet waste, wild and farm animals, birds, and even humans), not to mention  heavy metals, fertilizers, pesticides, litter and anything else in the water’s path.

Urban areas with a lot of rain and a lot of impervious surfaces will have more stormwater running off the land which can overwhelm conveyance systems and result in flooding. Flooding can destroy stream habitat by eroding banks and stream beds and add sediment to the water. Water running off heated pavement may increase the surface water temperature, making it uninhabitable for fish, their eggs, and the aquatic food sources that fish need to survive.

Due to the cost, most stormwater is not treated to remove pollutants; it simply flows into a ditch or storm drain and is conveyed directly to our streams, lakes, and marine waters. This runoff poses a serious threat to the Salish Sea. Municipalities typically have a series of catch basins, pipes, ditches, and drains that convey stormwater to help prevent flooding, however many of those systems do not eliminate the pollution entering our waters. Municipal and commercial stormwater conveyance is regulated by the Clean Water Act and state and local statutes. In Washington State, the Department of Ecology issues the permits and monitors compliance with requirements.

In rural areas, runoff from small farms, livestock operations, residences, pet waste, and failing septic systems can be conveyed in ditches and cause water pollution.

5 juvenile fish in a jar
Juvenile coho like these are impacted by polluted stormwater.

Scientists have confirmed that the pollutants in stormwater are harmful to organisms that encounter it. For example, dissolved copper can disrupt a salmon’s sense of smell. Without the ability to smell, a fish may not be able to imprint on their home stream for future spawning, navigate effectively, or even detect a predator. When fertilizer accidentally ends up on the sidewalk it can be washed by stormwater to the sea, where it promotes algae growth. The algae consume oxygen as it dies, starving other marine organisms of oxygen, creating a dead zone.

Research and experiments have shown that stormwater collected from highways, especially after the first big rainstorm of the season, can impair or even be lethal to some fish. However, fish survived after that same stormwater was filtered through a special rain garden soil mix.

This type of important research is being conducted by researchers from the University of Washington and Washington State University at the Washington Stormwater Center. The Center also provides training and technical assistance on a variety of stormwater issues; including helping municipalities and businesses navigate and comply with Department of Ecology regulations and permitting.

aerial view of parking lot with cars
Cars have a big impact on stormwater pollution. Consider driving less. Google Maps.

While stormwater management is done by most cities and towns at a large scale, we can all do our part in lessening the risks of polluted stormwater. By preventing pollution at the source, it’s easier and far less expensive than trying to remove it once it’s in the water. Imagine stirring sugar into a glass of water – now, how do you get it out?

Here are some practical, everyday tips to reduce polluted runoff:

  • Maintain your car and drive it less. Make sure all fluid leaks are fixed.
  • Wash your car at a commercial carwash where water is collected and treated.
  • Dispose of fluids properly. Never dump fluids into a storm drain. Remember – Only Rain Down the Drain!
  • Reduce fertilizer and pesticide usage. Sweep up any spilled product.
  • Maintain your septic system if you have one.
  • Pick up pet waste, bag it, and dispose of it in the trash.
  • Keep animals and livestock out of streams.
  • Reduce rooftop runoff. Direct your downspouts to a place where water can soak into the ground, and not onto a driveway or into the storm drain on your street.
  • Install home-based, Low Impact Development (LID) techniques such as rain gardens, permeable pavement, rainwater catchment. Learn more at WSU Extension’s Rain Garden website.

Please visit the Washington Stormwater Center website, where you can learn even more secrets of stormwater.

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