AWRA Water Blog

Only Rain Down the Drain

by Katrina Mendrey

This is my favorite time of year for dog walking.  The rains have subsided, flowers are in bloom and everyday there is something new to take note of.  My dog is as serious marker so there is plenty of time to notice the changing scenery of my neighbors yard.

“The Puget Sound Starts Here: Only Rain Down the Drain.”

Recently though, I’ve noticed a new addition to my daily walk that seems rather permanent.  Adorning every storm drain in my neighborhood are friendly reminders that what enters the drain will also enter Puget Sound.  Signs glued firmly to the road near every storm drain read “The Puget Sound Starts Here: Only Rain Down the Drain.”  Serving as a friendly reminder to pick up that poo and not to dump that pesticide or fertilizer on the lawn, the signs are just one of many innovative ways Washington State is seeking to reduce non-point source pollution in our stormwater.

The EPA estimates that 30% of water pollution is now caused by non-point sources of pollution, otherwise known as the junk on urban surfaces washed away by stormwater.  Here in Washington State, outreach programs such as Puget Sound Starts Here and Only Rain Down the Drain educate residents in Western and Eastern Washington about where exactly those storm drains lead.  In addition to the storm drain signs, advertisements on buses and websites provide tips for residents on how they can help reduce water pollution from surface runoff.  They also serve as a reminder that even your little contribution to pollution can make a big difference when everyone else’s is also accounted for.

But while, public education is a cornerstone to reducing pollution in stormwater not all pollutants can be directly diverted through such tactics.  Other innovative techniques are necessary to reduce the pollution that enters our waterways.

Two such approaches have been highlighted on the Washington Stormwater Center’s Website.  Under the Washington State industrial general stormwater permit, facilities are required to reduce copper in their runoff to 14 ppb and zinc to 117 ppb.  Copper even at very low levels can inhibit the ability of fish to smell and sense danger while zinc can suffocate fish by collecting on gills.   These metals come from various sources including break pads, tires, motor oil and galvanized roofing.

When the Port of Seattle discovered stormwater from their facility was elevated in copper they looked for a creative approach that would fit their facilities needs.  The copper they discovered was mostly coming from a nearby overpass, with runoff concentrations tested at 300 ppb.  The Port was already using oyster shells, a locally available product, in bioswales at Sea-Tac International Airport to adsorb copper and to some degree zinc.  Rather than build bioswales with oyster shells, the Port devised a way to adsorb copper with the shells directly in the storm drain.  Copper removal was reported to be 50-70% based on this method.

At the Port of Vancouver further south, runoff from roofs and gutters was found to be elevated in zinc.  Again building permanent bioswales was not the best option for the facility.  Two employees devised a portable low-cost bioswale system using 250 gallon plastic bins that could be placed under various downspouts and moved as needed.  The bins filled with a bioswale soil mix of sand and compost layered with gravel allows for adsorption of metals by the soil and efficient water infiltration.

Videos describing how to build both systems are available at

While I won’t be adding oyster shells to my neighborhood storm drains anytime soon, the drain signs I walk by everyday are an important reminder that we all have a role in reducing non-point source pollution.  So pick up that dog poo, take your car to the car wash and don’t let those insects trouble you, they’ll be gone as soon as it rains again.

Katrina Mendrey is a student at the University of Washington studying soils, particularly the organic component of soils and is especially interested in biosolids.

If you have questions or comments for Katrina, please leave them in the comment area below.

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