Dixie Drain Phosphorus Removal Facility – Parma, ID

Project Overview

The Boise River is a vital natural and cultural resource for the City of Boise and the surrounding Treasure Valley, offering significant economic, aesthetic, recreational, and ecological benefits. Ensuring high water quality in the Boise River is critical for the region’s sustainability and livability.

The Problem

Phosphorus, a naturally occurring nutrient, is essential to river health at normal levels but becomes harmful in excess. Elevated phosphorus levels contribute to algae blooms, degrade water quality, and disrupt river ecosystems. Regulations mandated a 98% reduction in phosphorus leaving the City’s water renewal facilities into the lower Boise River. While the City’s existing facilities could remove 93% of phosphorus, achieving further reductions would have required costly upgrades and left some phosphorus sources untreated.

The Solution

To address this challenge, the City of Boise partnered with Brown and Caldwell (BC) to create the Dixie Drain Phosphorus Removal Facility, an innovative and cost-effective solution using conventional treatment technologies in a new way. Located near the confluence of the Boise River and Dixie Drain—an agricultural and groundwater drain discharging into the Boise River—the facility captures and treats ground and surface water before it enters the river.

This pioneering facility removes an additional 50 percent of phosphorus per day, totaling 140 pounds per day, resulting in:

• A more cost-effective solution compared to upgrading existing facilities

• A significantly greater environmental benefit for the Boise and Snake Rivers

• A model for other regions facing similar nutrient reduction and funding challenges

Project Impact

Operational since July 2016, the facility treats up to 130 million gallons per day from the Dixie Drain. For the same cost as upgrading the City’s water renewal facilities, it removes more phosphorus overall, with 1.5 pounds removed at Dixie Drain for every pound not treated at city facilities.

This project not only enhances water aesthetics but also improves habitat conditions for aquatic life by reducing sediment and nutrient levels. It serves as a precedent-setting model for other communities globally, demonstrating an effective and affordable approach to meeting stringent environmental regulations.