Hayden residents are being asked to pony up an additional $7 every two months to cover the costs of a lawsuit brought by the North Idaho Building Contractors Association.

The city mailed postcards this week to its 5,100 sewer system users to apprise them of the proposed fee increases and of an Aug. 13 public hearing at Hayden City Hall to discuss the proposal.

The lawsuit, which began in 2012, was mediated recently. A district court judge must still sign off on the agreement. The city has spent almost $1.5 million defending the suit.

City Administrator Brett Boyer said the $7, which is scheduled to be phased out in 2024, is just part of a fee increase that is pushed primarily by sewer discharge standards.

The proposed increase to a base bimonthly rate of $45.50 from the $38.42 that sewer-district patrons now pay, will also be used to install a membrane system at the Hayden Area Regional Sewer Board treatment plant on North Atlas Road.

The facility is in its second phase of upgrades, which are required to meet phosphorus and dissolved oxygen standards, Boyer said.

“The new requirements mean we need to have new technology that this plant doesn’t have,” Boyer said. “Those are mandatory requirements ... we have to meet them.”

The upgrade includes installing a membrane system to catch phosphorus particles before they are discharged into the Spokane River. When added to a natural system, phosphorus consumes oxygen. The resulting oxygen depletion causes plants and animals to die.

The city’s share of the upgrade cost is $9.5 million, while the remainder of the $18.7 million will be split between HARSB, the city of Hayden Lake and the Kootenai County Airport, which share the facility on the airport’s southwestern perimeter.

Ken Windram of Hayden Area Regional Sewer Board said Hayden is among the last cities that discharge treated wastewater into the Spokane River to upgrade its facility.

“All the other plants on the Spokane River have done the same thing,” Windram said.

Coeur d’Alene added a membrane system recently. Post Falls is in the process of upgrading, and the communities downriver have upgraded to meet new phosphorus standards or are in the process.

During the nongrowing season, the plant’s treated wastewater is piped to the Spokane River. In the spring, summer and autumn, wastewater from the plant in Hayden is sprayed on the aspen and alfalfa farm that abuts Boekel Road.

“It grows trees,” Windram said.

The particulate collected at the plant is used as fertilizer and bought by farmers in Ritzville, Wash., he said.

Upgrades at the Hayden plant are in the planning stage and are scheduled to be completed in 2022.