For the last 12 years, the sewage treatment lagoons on the Seaplane Base have been filling up with materials flushed down toilets and swirled down drains in Oak Harbor homes and businesses.

The solid stuff that has accumulated at the bottom of the lagoons over that time will soon be headed to Eastern Washington, where it will likely be spread over fields of wheat.

Public Works Superintendent Cathy Rosen told the Oak Harbor City Council Tuesday that the amount of biosolids in the lagoons is starting to have a detrimental impact on the operation of the plant. In some places the biosolids are six feet deep, she said, while the total depth of the lagoon is eight feet.

Luckily for the city, Everett has a biosolids recycling program and has agreed to take up to 3,000 dry tons of the treated sludge off Oak Harbor’s hands.

It comes with a cost. Oak Harbor agreed to pay Everett about $210,000 for biosolid disposal. Plus, the city is contracting with a Maryland firm to dredge the biosolids from the lagoons, de-water the stuff and then haul it to Everett’s wastewater reclamation, at a cost of about $288,000.

But these aren’t unanticipated costs. The work will be paid for out of the wastewater division’s dedicated fund. That means the money won’t come out of the city’s general fund, but from a fund that users — city residents and businesses — pay into through the bi-monthly utility bill.

Besides the city, wastewater also flows in the lagoons from the Navy Seaplane base. The Navy actually owns the facilities, but contracts with the city for operation of the treatment plant, which the city took over a few years ago.

The city is currently looking into acquiring the Seaplane base wastewater collection and treatment systems from the Navy. The Navy is moving toward privitization of such facilities and recently sent a “request for proposal” to the city.

According to City Engineer Eric Johnston, dredging of the biosolids is just a normal part of the sewage treatment process. The treatment lagoons work sort of like big septic tanks. Wastewater is allowed to sit in the lagoons, where the solids settle to the bottom. The liquid is further treated and disinfected before being discharged into Crescent Harbor.

While smaller municipalities usually need to get lagoons dredged every five to ten years or so, Everett biosolids manager Joe Vibbert said a large city like Everett has to remove biosolids every other year.

According to Vibbert, Everett has accepted biosolids from smaller communities — Oak Harbor, Lake Stevens and Marysville — since these smaller entities can’t afford or don’t want to go through the permitting and trouble of building biosolid recycling facilities.

After Oak Harbor’s biosolids are trucked over the Everett, Vibbert said it will be mixed with ash to raise the pH level and filter out much of the odor. After a whole lot of testing, it will be hauled to Waterville in Eastern Washington, where farmers will apply it to fields.

Vibbert said the farmers “clammer” for the biosolids since they are safe, beneficial to the soil and rich fertilizers. Plus, the farmers make money by accepting the stuff. Biosolids are basically the same as any compost, though higher in beneficial elements than composted animal manure.

“People have more varied diets,” Vibbert explained.

Vibbert said there are many, many rules regulating the application of biosolids. Some of the regulations depend on the quality of the material, which governs how it can be applied — whether it’s tilled in, sprayed on, etc. For the Everett plant, Vibbert said the main thing that affects quality is the amount of metals in the material.

Vibbert said metals can come from industry, household chemicals and cleaners, copper piping and even dentist offices, which are a “big polluter” of mercury.

Everett has about a dozen permitted sites for biosolids application around the state. According to Vibbert, the biosolids are also spread on poplar plantations, forest land as well as farms. Some is taken by a top soil company and some is sold commercially.

“It’s really exceptional quality stuff,” he said.