Group advocating restoration of Arboretum Creek

FOAC wants to reconnect Alder, Alley Creek to support watershed, improve sewer system capacity

Group advocating restoration of Arboretum Creek

Group advocating restoration of Arboretum Creek

The Friends of Arboretum Creek group is seeking support for a grant request to fund preliminary designs for revitalizing Arboretum Creek, strengthening natural areas around Lake Washington and easing demand on the local sewer system.

Proponents seek to undo the impacts of logging and development on Arboretum Creek, rerouting two streams uphill from the Seattle Japanese Garden from a combined sewer overflow system back into Arboretum Creek, which is expected to improve wildlife habitat in the area. FOAC believes this will divert 40,000 gallons of water from the sewer system and reduce pollution in Montlake Cut. There is also a seep along 28th Avenue East that could be added into the system.

FOAC member Larry Hubbell has been thinking about restoring Arboretum Creek for nearly a decade. A master birder with the Seattle Audubon Society, he said he wanted to know why the eagle population was so low around Union Bay, and began looking into the Arboretum Creek watershed and its impact on the local ecosystem.

He decided to take action after bringing up the need to reestablish the environment to his friend Dave Galvin during a day trip with master birders in 2017.

“And he looked at me and said, ‘Let’s do it,’” Hubbell said. “And that’s the first time anybody ever replied like that to my idea for the creek.”

Galvin has been working with Hubbell in pushing this project forward and has a strong background in water testing.

Friends of Arboretum Creek looks at logging around Arboretum Creek in the 19th century, followed by the creation of Madison Street, cutting through the creek and damming off water collection as far south as Garfield High School, as culprits in the watershed’s decline.

As the neighborhoods around the watershed grew, remaining stream water was diverted into underground pipes and combined with the sewer system. During storm surges, Hubbell said, the overflow goes untreated into Montlake Cut.

The King County Wastewater Treatment Division is allowed only one event at each of its controlled combined-sewer overflow (CSO) locations on a 20-year average under its National Pollution Discharge Elimination System permit for the West Point Treatment Plant. 

King County has put in controls for roughly half of its combined-sewer overflow locations, and is required under a 2013 consent decree with the U.S. Department of Justice to complete its CSO control plan by 2030. Controls provide relief for the system, such as through storage tanks and green stormwater infrastructure. Overflows have trended downward over the last 20 years despite increases in average annual rainfall, according to King County’s 2018 CSO Control Program Update report.

“Our goal is really to reduce CSOs [combined sewer overflows] across our system in order to meet our permitting requirements,” said Michael Galvan, water quality planner and program manager for the King County Wastewater Treatment Division.

And FOAC’s proposal aims to do that by taking surface water around Arboretum Creek out of the combined-sewer system.

“We do have an interest in this project, and we have done some planning-level investigations on the benefits to our wastewater system,” Galvan said.

He confirmed that removing Alder Creek and other surface waters near Arboretum Creek from the combined-sewer system connected to the West Point Wastewater Treatment Plant in Magnolia would free up capacity. It also would keep clean water from being mixed with sewer water unnecessarily.

FOAC received a grant from King County in 2017 to conduct water-quality testing in Alder Creek and Alley Creek, which is what the group calls the stream that flows between East Aloha and Ward streets at 26th Avenue East.

“It’s reasonably good water. It’s relatively uncontaminated. Really, there’s no reason to divert clean water into our sewer system,” Galvan said, later adding, “We’re treating all that water, and if it’s clean water, we’re incurring that cost.”

FOAC is now applying for a $100,000 grant through the King County Wastewater Treatment Division to come up with a 30-percent design for reuniting the streams with Arboretum Creek. Hubbell said FOAC hopes residents will send letters of support for the grant to the King County Council, which will make a decision later this year. If approved, funds could become available in early 2020.

“Things are going to get better,” Hubbell said. “It’s just a question of how much.”

He said FOAC’s long-term goal is to be able to provide people with tours of Arboretum Creek once it is restored and the watershed habitat improves.

Getting to that point requires support from a number of agencies and organizations, including the Arboretum Foundation, Seattle Parks and Recreation, the University of Washington Botanic Gardens, Seattle Public Utilities, the Seattle Department of Transportation and Seattle Parks Foundation, which is FOAC’s fiscal sponsor.

Galvan said the King County Wastewater Treatment Division has been working with planners from multiple agencies on a number of CSO control projects.

“Really, that’s kind of the clear partnership that we’re really interested in, working with these local community groups and other agency groups to maximize these benefits,” he said.

Hubbell said he’d like to see the project coincide with plans to remove an underground pipe on the lower portion of Arboretum Creek, below Lake Washington Boulevard, once State Route 520 bridge replacement work is completed.

Look for more information on FOAC’s website being built out at