Letters from the West

Boise now runs wastewater plant near Parma, a new idea to clean river

Nearly 100 people gathered for the official opening of the Dixie Drain Phosphorus Removal Facility.
Nearly 100 people gathered for the official opening of the Dixie Drain Phosphorus Removal Facility.

For more than a decade I have been writing about the effort in the Boise River watershed to use the power of markets to help clean up the river.

After two years, the city of Boise finally put the idea into action, opening the Dixie Drain Project. The phosphorus removal facility began operations in July and was officially commissioned Wednesday.

The Dixie Drain empties return irrigation water from thousands of acres of farmland across Ada and Canyon counties back into the Boise River.

The idea has always been relatively simple: Instead of paying millions of dollars to build new facilities to remove phosphorus from Boise water, use the money to extract even more phosphorus from ag runoff downriver.

But putting the concept to action has been a lot harder. Part of the challenge is the ability to measure how much the plant will remove and how much to count against the city’s federal phosphorus pollution limit.

EPA officials in Washington were skeptical, even though local EPA officials worked hard to find ways to resolve the outstanding issues. The Dixie Drain facility becomes a pilot plant that will prove the concept here, so that perhaps private interests can follow.

City officials say the 49-acre facility between Parma and Notus removes up to 140 pounds of phosphorus per day — about 10 tons a year. This makes the Boise River as well as the Snake River downstream cleaner.

The way it works is to divert water from the existing drain system and adds a chemical that causes phosphorus to coagulate and settle to the bottom.

Federal regulations will soon require Boise to remove 98 percent of the phosphorus from the water that leaves its treatment facilities and goes into the Boise River. High amounts of phosphorus can produce algae blooms and reduce water quality for fish and many other uses.

Boise will remove about 93 percent of the phosphorus at its existing facilities, as required by the new regulations. But instead of paying the extraordinary cost for the remaining 5 percent, the city built the Dixie Drain project.

Part of the way Boise made its case to the EPA was to show that 80 percent of water that leaves the city of Boise’s existing water treatment system gets used downstream to irrigate agricultural fields, where it picks up more phosphorus before it drains into the Snake River.

Essentially, for every pound that is not removed at a treatment facility in Boise, a pound and a half is removed downstream at Dixie Drain.

“The Dixie Drain project exemplifies how various partners can collaborate, leverage strengths and resources, and together implement innovative environmental solutions,” said Idaho Department of Environmental Quality Director John Tippets at a ceremony Wednesday.

Since the Treasure Valley’s other cities have to meet the same Clean Water Act standards the project may be the first of many built by farmers or contractors to pay for cleaning up the runoff.

“What began on the back of an envelope over lunch has blossomed into an outstanding local, state and federal team effort that will help protect the Boise and Snake rivers for all Idahoans,” EPA Region 10 Administrator Dennis McLerran said in a statement.

Rocky Barker: 208-377-6484, @RockyBarker