The dried brown stuff produced by Oak Harbor’s treatment facility will make a temporary layover behind the public works building on the north end of town.

Public Works Director Cathy Rosen explained to city council members at a workshop last week that a structure will need to be built to house the biosolids the new treatment plant will produce beginning this fall.

The winning bid for the fabric-covered shed is $32,000, but city staff will have to pour the slab, install sewer and erect the structure, Rosen said.

The City Council is set to finalize the purchase of the poop shed during its Tuesday, Sept. 4, council meeting.

The plant is designed to produce a dried product that is considered Class A biosolids, which can be used as fertilizer for residential or commercial uses. Rosen explained that the state Department of Ecology will first categorize the stuff that is produced by the plant as Class B until the city can show it consistently makes Class A biosolids.

Class B can be used as a fertilizer on fields that are planted with wheat, alfalfa and other agricultural products, according to a Washington State University report.

During the start-up period, the biosolids will be hauled to the shed and then to the Boulder Park Project in Eastern Washington, where it will be spread on agricultural land. A total of 35 sewage treatment plants participate in the service jointly operated and managed by King County and Boulder Park, Inc.; the biosolids are spread over 90,000 acres in Douglas County, according to a May 2018 report on the project by the state and King County.

Eventually, Oak Harbor’s treatment plant will produce Class A biosolids, which will also be stored in the new shed; it will be able to hold 100 to 200 yards of the stuff. Brett Arvidson, project manager for the plant, said the product can be sold to the public in small amounts or to nurseries and other businesses as a soil amendment and fertilizer.

“If we do it right, we’re going to have a customer mix,” he said.