For about a century, Last Chance Canal Company relied on a timber crib dam near Grace, Idaho, to divert water from the river into its canal system. After years of service, the aging structure needed to be replaced with something the company could operate safely and reliably. Franson Civil designed a roller-compacted concrete dam with two large radial gates capable of passing 1,000 cubic feet per second. A smaller side gate allows the company to continue leaving the required flows in the river while directing water to canal users.

Getting the new dam built took more than a sound design. Our team worked alongside the Canal Company through a challenging Federal Energy Regulatory Commission permitting process and helped secure the required approval. Once construction began, harsh winter weather and changing river conditions tested the schedule. We stayed in close contact with the contractor to spot problems early and coordinated with PacifiCorp, which operates dams and hydropower facilities upstream, to adjust water releases when needed. Those efforts gave the contractor workable conditions and kept construction moving.

For the people who depend on the system, the new dam provides a more reliable way to deliver irrigation water while maintaining flows in the river. Farmers and other canal users have a structure that is easier to control and less vulnerable to the problems that come with a century-old timber dam. The project also supports the broader Grace community by protecting an important part of the area’s water infrastructure and balancing the needs of canal users with the health and use of the river.