Green blacktop fights polluted water runoff

WSU environmental toxicologist John Stark stands on the rebuilt parking lot that, in essence, drinks polluted rain runoff. The wetland is behind him.

By Linda Weiford, WSU News

PUYALLUP, Wash. – To save paradise, John Stark paved a parking lot. Next he hopes to do it to a highway.

An environmental toxicologist who oversees Washington State University’s Puyallup Research and Extension Center, Stark studies ways to make blacktop green.

Stormwater runoff – or polluted rainwater, as he likes to call it – is a sinister byproduct of our urban life. Whether in the Pacific Northwest or the Eastern Seaboard, rain that beats down onto conventional roads and parking lots picks up contaminants as it is channeled into creeks, rivers, lakes and oceans. Roughly 85 percent of the water pollution in the United States is caused by this kind of runoff, according to the U.S. Environmental Protection Agency.

A parking lot located at the WSU research center south of Seattle once produced this toxic brew. Whenever it rained, water would slide off the pavement, picking up oil, road grime and heavy metals as it flowed downhill into a nearby wetland.

Under the long shadow of Mount Rainier along timbered knolls and tall grasses, it was not a pretty picture.

“The wetland would flood and the overflow would go into a nearby creek that feeds into the Puyallup River. From there, the runoff would spill into Puget Sound,” recalled Stark. “Here we were, publicizing the importance of managing stormwater runoff and we were contributing to the very problem.”

A concrete solution

So Stark and his colleagues went to work. Using grant money issued by the Washington Department of Ecology to the City of Puyallup, in 2010 they installed a new parking lot that, in essence, drinks water. Made of permeable concrete and asphalt, the sponge-like surface prevents rainwater from dispersing and picking up pollutants as it goes.

“The water trickles through the pavement to a gravel base below. Over time, the water seeps into the ground where many of the impurities are filtered out,” Stark explained. “We’ve been closely monitoring the data. It’s 100 percent effective at filtrating water and stopping runoff.”

If a parking lot can be paved with good intentions, it’s this one. Besides providing a space for people to leave their vehicles and corralling polluted runoff, it also serves as a full-scale laboratory for collecting data to help cities and counties nationwide.

“There’s a big demand for ‘green’ solutions for stormwater runoff, but there are also big gaps in research on what works and what doesn’t,” said Stark. “We’re trying to fill those gaps so science-based decisions can be made.”

Fortified by jet wings

Though permeable paving is effective in parking lots and side roads, it’s generally not strong enough for heavily-traveled highways. So Stark is collaborating with Boeing and engineers from WSU’s Composite Materials and Engineering Center to see if adding the same material found in the wings’ outer surface of the 787 Dreamliner will make the grade.

Carbon fibers appear as singular black strands inside the asphalt. (Photos by Linda Weiford, WSU News)

Light-weight carbon fibers reduce the airplane’s weight while adding durability. By incorporating these black strand-like fibers into porous asphalt and concrete, WSU scientists are seeing if permeable pavement can be made more durable. They’re also validating that the composite material doesn’t leach contaminants.

Boeing donates scrap carbon fibers for the research and provided a $212,000 grant to get it started. Though still in the experimental phase, “preliminary results look promising in terms of increasing the strength of the pavement and reducing the toxicity of pollutants,” said Stark.

Working with WSU engineering, his next phase of research will evaluate the durability of the modified pavements on experimental stretches of asphalt exposed to vehicle traffic. Researchers will examine whether the addition of carbon fibers increases pollution filtering and how long the filtering process lasts with wear and tear on the asphalt.


John Stark, WSU Puyallup Research and Extension Center, 253-445-4568,
Linda Weiford, WSU News, 509-335-7209,