Seattle Takes Greener Approach to Sewer Overflows

A greener approach in Seattle, Wash., aims to prevent untreated sewage and polluted runoff from flowing into Puget Sound by installing dozens of landscaped drainage systems in front of people’s homes.

County officials and others say they’re a cost-effective, environmentally friendly way to prevent heavy rains from overwhelming sewer pipes and storm drains.

But in southwest Seattle, where the county is planning to install them across 31 neighborhood blocks, some residents see them as a potential safety hazard, an eyesore and just plain inconvenient. A petition is seeking to stop the project.

“I totally understand what they’re trying to accomplish. I get what the problem is. I’m not anti-green,” said Tracey Parker, who lives in one of two neighborhoods slated for the project. But she’s worried about the loss of parking spaces on her block, access to the street from her home, and other issues.

The U.S. Environmental Protection Agency is promoting the environmental tools known as green infrastructure, and cities such as Portland, Ore., Kansas City, Mo., and Philadelphia have embraced the greener solutions to prevent sewage overflows that foul swimming beaches and local waterways. New York City and Philadelphia are spending millions on such methods. A green infrastructure initiative in Portland, Ore., has helped that city reduce its sewer overflows, officials said.

The idea behind the technique is to use vegetation, soils and tools such as porous pavement or green roofs to slow, filter and absorb rainfall so it won’t overwhelm the region’s pipes, which carry both wastewater and stormwater, and backs up when there’s too much rain.

“We chose the best solution for the dollar,” said King County’s project manager Mary Wohleb, who adds the project has environmental benefits by curbing polluted runoff, one of the biggest problems facing Puget Sound. “We’re able to take the polluted stormwater out of the system, filter it and keep it from going into the local waterway. We’re reducing the pressure on our system.”

King County, which runs the sewer system for Seattle, is planning to build about 185 bioswales in the city-owned property parking strips, the piece of land located between the sidewalk in front of people’s homes and the street curbs. Bioswales are natural depressions designed to allow rain to seep into the soil, where a pipe would then drain that water deeper under ground. Trees, shrubs and other plants would be planted above ground.

But a fiasco with rain gardens in another Seattle neighborhood has made some residents jittery about this project.

In 2010, Seattle officials rushed a project to put rain gardens into the Ballard neighborhood. The rain gardens ponded and didn’t properly drain, and the city had to spend $500,000 to fix it.

“Unfortunately, they (Seattle) put in a system that didn’t work,” said Pamela Elardo, who directs the wastewater division for King County, adding that officials are working hard to avoid some of those problems. “Hopefully, over time that Ballard scar will fade into the books. People are generally very excited about it. The potential and benefits are so huge that it’s worth sticking it out. Case by case, we’re responding to individuals.”

The current project won’t rely solely on the soil to absorb water as rain gardens do; an underground pipe will be installed to drain water down past hard pan and into permeable soils about 20 feet below the surface.

Some, like Sabrina Urquhart, are still skeptical. She and others worry that water won’t drain fast enough, leading to pools that could create mosquito and other safety problems. They’re also worried the county won’t maintain the bioswales once they’re in place. The county says the swales are designed to filter about a foot of water every 24 hours, and they will maintain them.

“I think most homeowners thought they’d be getting some nice landscaping,” said Urquhart, a communications director who said she was initially excited when she first learned about the project until she learned more about it. “We’re worried that in fixing one problem, they’ll be creating new ones.”

“These are the most cost-effective ways to deal with stormwater pollution,” said Chris Wilke, executive director of the Puget Soundkeeper Alliance, which works to clean up and protect the Puget Sound. “They actually reduce flooding risk, and they treat stormwater on site.”

Like many cities with older sewer systems, Seattle has many pipes that carry both wastewater and stormwater. During heavy rain events, the system overflows, causing polluted runoff and diluted sewage run into Puget Sound; without the overflows, sewers would back up into homes, businesses and onto streets.

The area overflows about four times a year – three more than allowed by state regulators. The county’s goal is have no more than one overflow.

Project engineers have been drilling sites and testing soils for months to determine where best to place them. The county’s Wohleb says they’re responding to public comments and are reviewing the potential sites.

“I think they need to see a successful project,” Wohleb said. “I have total confidence that this is going to be very successful. No question.”