Spokane County’s permit to operate its 2-year-old, $173 million wastewater plant was partially invalidated by state regulators last week.

The Washington State Pollution Control Hearings Board said the methodology used by the state Department of Ecology in granting the permit was faulty.

The board last Friday ordered the Ecology Department to revise the county’s permit and strengthen control of polychlorinated biphenyl going into the Spokane River.

The decision means the county will have to continue achieving the best possible pollution control. It also means that the DOE must set deadlines for the county to reduce PCB releases into the river.

The Sierra Club and the Center for Environmental Law and Policy filed the permit challenge against the Ecology Department and Spokane County.

John Osborn, of the Sierra Club, said he expected the plant to halt operations because of the ruling and divert wastewater to the Spokane treatment plant at Riverside State Park until the permit issues are resolved.

The county took another view.

Martha Lou Wheatley-Billeter, spokeswoman for the county, said the Spokane County Water Reclamation Facility at Freya Way in east Spokane will continue treating wastewater while complying with Ecology’s permit.

“We are not being forced out of the river,” she said.

Osborn said the goal of the pollution permit appeal was to protect the river from additional pollution.

“What has been invalidated is a key provision of the permit,” he said. “It is a substantial finding.”

Ecology scientists had determined that it was not possible to establish a numeric limit on PCB discharges. There is inadequate data on PCB levels and the numerous pollution sources.

County officials said the plant is so efficient that even detecting PCBs in the treated water leaving the plant is a challenge.

So, Ecology instead required the county to submit annual reports on pollution discharges. These numbers were then used as a baseline to establish a Regional Toxics Task Force to tackle the PCB issue.

The pollution board determined those steps were not sufficient and ordered Ecology to require additional improvements for PCB removal along with deadlines.

County Commissioner Todd Mielke said the county has no plan to appeal the pollution board ruling.