Allendale Canal and Fish Screen

The Problem

Flint Creek serves agricultural water users around the Drummond area and supports populations of fish including brown and bull trout.

When water levels are low in Flint Creek, whatever water doesn’t go to Allendale Canal, goes into one of the three ditches located about 1,000 feet downstream. A 2016 report from NRDP and Montana Department of Fish, Wildlife & Parks (FWP), showed that in the fall, when the brown and bull trout are migrating upstream to spawn, the existing rock and tarp diversion block upstream movement and fish are unable to reach their destination. The study also determined that a significant amount fish were being diverted into the irrigation ditches and over 450 were found in the first 2,000 feet the Allendale Canal. This project was complex due to the concentration of earthwork, concrete, in-stream diversion, rock placement, and structural, mechanical and electrical design requirements. Adding to the difficulty were some tight tolerances on some of the mechanical pieces, and there was nowhere to divert the creek away from the project site during construction. Contractors were constantly battling flowing water through the site during the construction. In addition, two significant flood events also passed through the site during construction.

The Solution

The completed project prevents fish entrainment, allows upstream fish passage on Flint Creek, and improves the surrounding water delivery infrastructure.

Morrison-Maierle, in partnership with OneFish Engineering and Quadrant Consulting, designed a vertical flat-plate fish screen that now safely excludes fish from Allendale Canal and returns them to Flint Creek through a bypass return pipe.