Idaho cities must reduce river discharges of phosphorus

Idaho cities will be required to cut their discharge of phosphorus into the Spokane River by more than 90 percent over the next decade to protect water quality.

The new limits are included in wastewater permits for the cities of Coeur d’Alene and Post Falls and the Hayden Area Regional Sewer Board issued last week by the U.S. Environmental Protect Agency.

“I’m still digesting it,” Sid Frederickson, Coeur d’Alene’s wastewater superintendent, said of the 50-page permit. “But as near as I can glean, there were no surprises.”

The new permits come after years of effort to reduce algae blooms and boost dissolved oxygen levels in the river. Washington has been operating under similar limits since 2011.

The permits require some of the nation’s lowest phosphorus emissions in treated sewage. By December 2024, the city of Coeur d’Alene’s treatment plant will be limited to just over 3 pounds of phosphorus in daily wastewater discharges.

The phosphorus ratio is 50 parts per billion, said Brian Nickel, an EPA permit writer. That’s equivalent to a single drop of water in an Olympic-size swimming pool.

Coeur d’Alene, Post Falls and the Hayden sewer board are already working on improving their systems and installing new technology to achieve the new limits.

Coeur d’Alene is anticipating $33.5 million in improvements to its wastewater treatment plant during the next decade. The Hayden sewer board broke ground this summer on the first phase of a $31 million project to reduce phosphorus in its wastewater. Post Falls expects to spend roughly $60 million on its treatment facility over the next two decades, said John Beacham, Post Falls’ environmental manager. That work includes improving the plant’s efficiency, better phosphorus removal and other upgrades to keep the plant in compliance with operating permits, he said.