COEUR d'ALENE - City wastewater fees automatically increased this week in the second year of graduated rate increases that will continue to climb until 2017.

On April 1, city wastewater rates increased 8.5 percent as part of a five-year gradual rate increase that started in 2013.

According to City Wastewater Supervisor Sid Fredrickson, the increase is to pay for a state-of-the-art upgrade and expansion of the wastewater system.

The expansion, which is estimated to cost at least $34 million, is necessary to bring the plant into compliance with new federal water quality standards in the Spokane River, he said.

"That's just the projected costs, but I think they are a little low," Fredrickson said.

Fredrickson said the new upgrades will be completed in phases. The first phase is to get the tertiary treatment facility up and running for a year after the city's final discharge permit is issued.

"We don't even have the permit yet. That should be out in the next couple of months," he said. "But we are already ahead of the game."

The first phase is to get the system online to treat one million gallons of wastewater a day. Another four million gallons of capacity will be added after that, and the third phase will increase capacity again by another one million gallons.

"That may take about 10 to 12 years to get there," he said. "It is a cutting-edge facility. I know of no other community that has to treat their wastewater to these standards."

The U.S. Environmental Protection Agency has set a "Total Maximum Daily Load," or TMDL, for dissolved oxygen on the Spokane River from Lake Coeur d'Alene to Long Lake just west of Spokane.

To achieve the new standards, Fredrickson said every discharger between Coeur d'Alene and Spokane will have to upgrade their treatment facilities.

The treatment will increase the oxygen levels in that body of water, but to get there Fredrickson said he has to remove three different elements, including phosphorus, organic materials, and ammonia.

"Phosphorus is the big one. One pound of phosphorus can suck 16 pounds of oxygen out of the water," he said. "Ammonia will suck up four-and-a-half pounds of oxygen."

Fredrickson said the city is currently reviewing a draft of the final permit. Once it is issued, it will trigger a whole series of benchmarks the city will have to meet for the next eight years.

The new single family home rates will increase the monthly sewer bills from $26.40 to $28.50 this year, and will gradually increase to $35.65 in 2017.

"But we are still a lot cheaper than many of our neighbors," Fredrickson said.

Currently, residents of Spokane pay $51.34 per month, Spokane Valley residents pay $47.01, Post Falls charges $33.79 monthly, and Hayden residents pay $28.86 per month.