An Oak Harbor official is inviting members of the public to take a whiff of the sewage treatment plant.

Residents continue to grumble about odor from the Clean Water Facility nearly four years after it went online. Several people, including residents of a nearby condominium, have complained to city council members, city staff and the newspaper about the ongoing stink this summer.

Public Works Director Steve Schuller said city staff assume that the odor is associated with the processed biosolids, which are dried to a crunchy texture in the last step of the treatment process. The odor seems to be the worst on Monday morning when the facility has to be shut down and restarted and a truck is loaded with biosolids to haul to a nursery.

Schuller said the stinkiness seems to be especially bad when the weather is hot.

“It creates a perfect storm,” he said.

Yet Schuller said the sewage treatment employees want to be sure they are addressing the odor that residents find offensive. Different stages of treatment create different types of odor.

As a result, Schuller invites people with odor concerns to tour the facility and sniff out where they think the problem lies. In addition, he said touring the state-of-the-art, $150 million facility is both interesting and educational.

Those interested can email Schuller at sschuller@oakharbor.org.

The Northwest Clean Air Agency reported receiving only one odor complaint about the facility so far this year. It has received 45 since 2019.

A spokesperson said the agency is working with the city officials “as they continue to try to find ways to deal with the odor issue.” The agency has not taken any formal action against the city over the reekiness of the plant.

City council members promised that the plant would be smell-free when the decision was made to build it partly into the waterfront Windjammer Park. The council chose to spend $1.5 million on a high-tech odor control system, which includes activated carbon filtration and a fan system that pushes tainted air skyward. A complex of high-powered fans circulates air from the headworks and the dryer buildings through odor-eliminating structures.

The council also decided to spend $14.5 million on the dryer facility, which means the dried biosolids can be used locally as compost or a mild fertilizer.