Idaho officials break ground on $20M dam project on Boise River
Clark Corbin
(Idaho Capital Sun) Idaho Gov. Brad Little and officials broke ground Tuesday on a two-year, $20 million project to upgrade and modernize a nearly 100-year-old diversion dam located on the Boise River.
Officials with the Nampa and Meridian Irrigation District are replacing and upgrading the Ridenbaugh Diversion Dam, which is located just east of Barber Park – a popular destination where thousands of people begin their float of the Boise River each summer.
Little called the dam “a powerhouse in the Treasure Valley” and said the dam project will ensure farmers will continue to receive irrigation water they depend on.
“This project in particular will be a modernization into the 21st century, but it also has a safety and a fish aspect to it,” Little said. “So this is not just a pure irrigation project. It really checks all the boxes for what’s important in Idaho.”
Some of the funding for the $20 million dam project comes from $30 million that Little and the Idaho Legislature set aside during the 2025 legislative session for water infrastructure projects.
To help pay for the project, the Nampa and Meridian Irrigation District received approximately $10.7 million in funding from the Idaho Water Resource Board, which was part of the $30 million for water infrastructure projects. The Nampa and Meridian Irrigation District also received an approximately $4.7 million Bureau of Reclamation Watersmart Grant for the Ridenbaugh Diversion Dam project.
Dam project aims to distribute irrigation water throughout the Treasure Valley
The purpose of the Ridenbaugh Diversion Dam is to raise the water level, allowing water to be diverted from the Boise River into the Ridenbaugh Canal, where it is delivered to farms and lawns across the Treasure Valley for irrigation.
The existing Ridenbaugh Diversion Dam, which dates to the 1930s, has reached the end of its life, officials said.
“We’re hopeful that our new facility will enable us to distribute irrigation water through the valley for another 100 years,” Donald Barksdale, president of the Nampa and Meridian Irrigation District, said at the groundbreaking ceremony.
Operating the existing dam and raising the water level requires a crew of three people to install and remove a series of 20-foot long boards by hand, even in stormy weather or when the dam’s walkway is iced over.
Crews will replace that dam structure with a new automated system that includes gates and an 80-foot weir that will extend from the crest gate to the north river bank.
Crews will also install a screen to prevent adult fish from entering the Ridenbaugh Canal, officials said.
During a press conference Tuesday, Greg Curtis, water superintendent for the Nampa and Meridian Irrigation District, said the cost of the project will not exceed $20.7 million and crews hope to finish it by spring of 2027.
Construction work will be performed in the winter months to avoid the busy summer river floating season at Barber Park, Curtis said. Work begins on one side of the river immediately, and will continue until March or April, when work will stop before the floating season and the old boards will be put back in the dam.
Construction work will then resume on the other side of the river next October, after river floating ends, and continue until completion, which is expected before the summer of 2027.