Washington State University

Creating Cleaner Water Source Vital to WSU Puyallup Researchers

LID testing in Puyallup
WSU Puyallup researchers inspect the sprinkler system used to simulate rain events on the asphalt test plot.
(Left to right, Curtis Hinman, Low Impact Development Extension Specialist; Jen McIntyre, Postdoctoral Researcher Stormwater Program; and Richard Bembenek, Agriculture Research Technician, Low Impact Development)

Creating Cleaner Water Source Vital to WSU Puyallup Researchers

Bioretention Method Utilized in Innovative Project

By Betsy Fradd, WSU Extension

Finding a solution to toxic highway runoff is critical to a group of Washington State University researchers and the environment. Using a method known as “soil bioretention” scientists at WSU Puyallup Research and Extension Center are testing collected runoff to measure the effects on fish and other aquatic life.

“Vehicle exhaust often contains dangerous levels of polycyclic aromatic hydrocarbons (PAHs), which are known to cause heart and cardiovascular defects in animals,” said Jen McIntyre, lead WSU Puyallup Stormwater researcher. “We want to eliminate or lower the PAHs to create a healthier environment for aquatic life and the general population.”

Simulated brief rain storms are created using sprinklers on a 27’ x 44’ test pavement. The plot, treated with coal tar sealcoat (CTSC) commonly used throughout much of the country, contains many of the same PAHs as urban highway runoff. Traffic counters record the number of vehicles passing over the site during the test period since abrasion is a major source of contamination to runoff from seal coated surfaces.

“After the runoff is collected it will be transported to the greenhouse with large bioretention soil columns,” said McIntyre. “Half of the water will be kept as untreated runoff. The rest will be passed through the soil columns - a kind of biological filter - that mimics what happens when runoff is infiltrated into the ground.”

During the six week study fish and aquatic invertebrates will then be exposed to raw runoff and that which has been run through the bioretention system to see if the toxicity is eliminated.

Findings from the study, funded in part by EPA Region 10 and NOAA Coastal Storms Program, will be published in a peer-reviewed scientific journal and presented at local and regional conferences to raise awareness of stormwater contamination, better understand the role of PAHs in runoff toxicity and the benefits of bioretention to clean up urban runoff.


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