City working to resolve smelly problem in Edmonds neighborhood

A King County sewer line runs under Third Avenue South between the Woodway town line and Edmonds’ City Park. This line carries flows from Richmond Beach and while no Edmonds homes connect to it, noxious sewage gases often seep up through the maintenance hole covers creating a neighborhood nuisance.

There’s something in the air near Edmonds City Park – and it’s not the holiday season

It’s like rotting eggs, the malodorous vapors rising through maintenance holes along stretches of 2nd and 3rd Avenues South between the Woodway town line and Edmonds’ City Park – and it’s been going on for some time, much to the chagrin of homeowners.

For years, residents have complained of being periodically assaulted by sewer fumes, but lately the problem appears to have become more acute, prompting homeowner Stephen Hearn to write in a public comment to the Edmonds City Council Tuesday, Dec. 1 that “the sewer smell…is now consistently present when we are in our yard. So much so that we have to go inside, shut our doors and windows to keep the smell out. This is not only having a detrimental impact on our quality of life, but we are getting concerned it may have potential health/economic impacts for our family.”

Hearn and several other residents also showed up virtually to speak to the issue during Tuesday night’s Edmonds City Council meeting, prompting Edmonds Public Works and Utilities Director Phil Williams to respond via email to councilmembers Wednesday, explaining next steps.

Many of the maintenance hole covers are clearly marked as part of the King County Metro system.

According to Williams, the potential primary source of the current miasma is a King County sewer line that runs under the aforementioned stretch of 3rd Avenue South. This line channels sewage originating from Richmond Beach, and is not connected to any homes in Edmonds. Periodic testing shows higher-than-expected levels of hydrogen sulfide, which is responsible for the rotten egg smell, in this line. The solution has been to install plugs in the vent holes of the maintenance hole covers. Unfortunately, these plugs work loose and deteriorate over time, and when they do the hydrogen sulfide leaks out and the odor problem returns. Since this line belongs to King County, they conduct periodic inspections and replace plugs as needed.

The vent hole plugs deteriorate over time, and need to be replaced.

A secondary source of the odor may be coming from sewage originating from Edmonds’ Lake Ballinger neighborhood east of Highway 99. While this flow originates from within the City of Edmonds, it travels to the Edmonds wastewater treatment plant through a King County line and is pushed by a King County-owned pumping station near Lake Ballinger under the terms of a “flow-swap” agreement between Edmonds and King County.

According to Williams, this pump provides the necessary pressure to move the sewage uphill against gravity until, on its final run to the Edmonds treatment plant, gravity takes over as it hits the downhill slope on 3rd Avenue near the Woodway town line. “The problem,” he said, “is the force…coming from this pump station is over-pressurizing the air in the pipe.” When it breaks from pressure feed to gravity flow the sewer gases, still under pressure, are forced through the system “from about 3rd and Elm down to 2nd Avenue and through City Park,” Williams explained, and because Edmonds homes are connected to this line, the pressurized gases can backflow into the sewage vent systems in the homes. These residential systems are designed to discharge the pressure of these sewer gases through rooftop vents but “unfortunately the odor comes with it,” he said.

The City of Edmonds has ordered this carbon-filter, forced-air fan system designed to address the problem by alleviating excess pressure in the sewer lines. (Diagram courtesy City of Edmonds)

The City of Edmonds is working on a permanent solution, which involves installing a carbon filter fed by an air-moving fan in City Park near the intersection of 2nd Avenue and Pine Street. “The negative pressure created by this system should depressurize the airspace above the flowing wastewater and capture the foul air that may otherwise escape from a vented maintenance hole or a home’s roof vent,” said Williams, who predicts the project should be completed by mid-spring 2021.

The new odor control station will be installed inside City Park near the intersection of Pine Street and 2nd Avenue. (Map courtesy City of Edmonds)

The odor issue on 2nd Avenue South, Williams said,  “has been a sporadic problem for a long time. To put it in perspective we have historically received two to three complaints a year related to this issue.” However,  after carbon inserts were installed in most of the street’s maintenance cover lids in approximately 2013, the city had few to no complaints. “We have neighbors who have thanked us for ‘solving the problem’ but it appears we may have only moved the problem to another location,” Williams wrote. “For some unknown reason in the last few months we have received more complaints than ever before without increasing flows or changing the pumping schedule. There has been no blockage of, or increase in, flows through this line over the last year. We have no indication the line is at capacity or that there is any threat of an overflow. In fact, for a period of six months approximately two years ago, we took all the flow from Ballinger and Richmond Beach and did not receive any complaints.”

The hydrogen sulfide odor “is a very unpleasant and annoying concern that we are committed to resolving,” Williams stressed, although he said the city has “no data that suggests it is a health hazard at the levels being detected.” The city is willing to loan its odor-logging equipment to any neighbor who wants to determine the level of hydrogen sulfide at any location in the area, he added.

Meanwhile, to provide immediate relief to residents, the city has asked King County to divert all flows from the Ballinger pumping station into the King County system until the carbon filter system is installed and operational.

— Story and photos by Larry Vogel

  1. Thank you for this great reporting! Here’s wishing everything goes well with the King County diversion and filter installation!

  2. Thank you for this article bringing our long years of stinky issues to light. Hopefully the council and mayor heard our voices and will finally get this taken care of as it has gone on for much too long!

  3. How about the stretch between new perrinville townhouses as you head south towards 196th / qfc? It is awful every day

  4. Nothing was said about our own sewer plant and the owners that come from it. What are we doing about that? How does the new major work on the sewer plant come in to play in solving anything. The odor is strong when the wind is coming from the north as it blows over the Marsh area and we live next to it. happens at least once a month.

    Where do the odor is go with the new system you’re putting up the street on third and Pine in the corner of the park. Are you really trying to tell us that it comes out of that stack odor free or what. Thank you very much for tackling the sewer orders for on certain days you can’t even be outside and if you inside you have to have every window door shut. Not much fun on warm days or now that it’s cold. Wishing you well and have a happy holiday

  5. It’s great to see that someone is working on a solution to this problem. I live in a condo in 3rd at the base of Walnut and there is a sewer cover right in front of the building. There is often a stench coming from the maintenance hole cover. I hope the planned solution will solve the smell in front of my home too.

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