Lost Horse Creek Siphon

The Ward Canal of the Ward Irrigation District intersects Lost Horse Creek about six miles south of Darby, Montana. Like many irrigation canal and stream interfaces in Montana, irrigation water was dropped from Ward Canal on one side of Lost Horse Creek and then pulled off the other side of the creek into the canal resulting in a mixing of creek and irrigation water. During low flows in the summer, irrigators were not able to hydraulically deliver water across the creek without damming it, which blocked most of the natural flow that served the irrigation district. To solve this problem, Morrison-Maierle engineers came up with a solution that involved the installation of a buried inverted siphon under the creek to convey irrigation water without interruption to Lost Horse Creek. The site was complicated by grade limitations and a nearby train trestle.

Irrigators and the agricultural community were not the only ones to benefit from this project. A 2007 study identified Ward Canal as the largest source of fish entrainment in the Lost Horse Creek watershed. This siphon project not only solved a big problem for the Ward Irrigation District, but it also helped migratory fish, especially westslope cutthroat trout and bull trout, a species listed as threatened under the Endangered Species Act.

To add to the complexity, Morrison-Maierle not only orchestrated the engineering design and concept, but worked with a significant number of permitting agencies to obtain numerous grants from several funding sources and maintained compliance with the conservation easement at the project site.

This project brought a piece of Montana back to Montanans—for the first time in decades, Lost Horse Creek now flows freely into the Bitterroot River.

Winner: 2016 ACEC Montana Engineering Excellence Award