Water treatment plant improvements to help salmon-bearing North Creek in Everett
|King County document
|Three major watersheds that span from Snohomish County southward, including North Creek's watershed.
EVERETT — North Creek, a salmon-bearing stream, will have cleaner water after the City Council unanimously approved a $16.6-million plan this year to improve treatment of stormwater runoff amid future development.
The North Creek Stormwater Management Action Plan calls for retrofits of regional stormwater treatment plants on Dorn and Meridian avenues, an improved treatment facility along Third Avenue SE, and updates to the city’s tree management ordinance.
Work will begin in summer 2024 at Third Avenue, on the west side of the Target store complex near Everett Mall. It is scheduled to be finished within six years.
The treatment-plant retrofits will be completed within 20 years.
When all three projects are done, 50% of the impervious surface in the North Creek basin will have its runoff water cleaned and returned to the creek. Today, only 5 % of impervious surface is currently covered.
“We felt we got the most bang for our buck implementing these three projects,” Dana Zlateff, a city surface water compliance specialist, told the City Council.
North Creek was prioritized among the city’s 23 water basins, largely because it originates in Everett and flows south through several other cities before reaching the Sammamish River which flows into Lake Washington.
There is also substantial business and multifamily development along the creek, especially at the city’s southern end.
“We really wanted to be able to grab and treat segments of Everett Mall Way and Evergreen Way,” Zlateff said.
The work will help salmon, for one.
Unfiltered stormwater carries polluted water into the stream from the runoff of stormwater in the area. The pollution creates poor living conditions for salmon.
The state Department of Ecology lists North Creek as an “impaired stream” because of these factors, the Snohomish Conservation District notes.
Funding for the $870,000 first project, titled “3rd Avenue SE Water Quality Treatment,” comes mostly from an Ecology grant.
Work will include installing about 200 feet of piping along the road and building a new treatment facility behind the sidewalk.
The new facility, which will be located in the footprint of an existing treatment plant, will treat runoff from a much larger area — about 45 acres. It will look like a sunken landscaping bed, with plants and mulch on the surface.
“It will be similar to a rain garden, but with a highly specialized soil that makes it much more effective than a conventional rain garden,” said Kathleen Baxter, city Public Works Department spokesperson.
Water from the storm drainage system will flow onto the surface of the facility and percolate down through the special soil material. Microbes in the soil and the roots of plants will remove pollutants as the water travels through. A pipe beneath the soil collects the water and routes it back into the drainage system.
Other aspects of the action plan are still in the preliminary planning stages.
They include assessing the North Creek buffers, updating the tree management ordinance to increase shade cover, and changing stormwater billing to an impervious surface basis.
With residential households, the latter might entail one fee for similar-sized homes. With businesses it would be more of a direct measurement, according to Heather Griffin, city surface water management manager.
“We’re trying to transition from (assessing by) what you are drinking, which doesn’t make much sense, to what are you doing with your land,” Griffin said.
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