The Dry Creek Canal crosses Dry Creek just south of West Dry Creek Road in Gallatin County, Montana. During the irrigation season, a headgate on Dry Creek is closed and intercepts Dry Creek into the canal. AESI was hired by Gillilan Associates, Inc., to perform a feasibility study of different alternatives to accomplish the project goals which included allowing Dry Creek to flow freely past the Dry Creek Canal, reducing fish entrainment in Dry Creek Canal, improving fish passage across this reach of Dry Creek, and improving the operation and maintenance of the irrigation structure at this location. AESI’s original feasibility study evaluated two options for the canal crossing the creek – a flume above the creek or a siphon under the creek. This feasibility study involved site reconnaissance, topographic survey, hydrologic and hydraulic analysis, permitting considerations, conceptual design, and conceptual construction cost estimating.
Upon review of the feasibility study by stakeholders, a third option of a fish bypass channel was selected for the project. AESI performed a preliminary feasibility evaluation for this option, developed construction plans and specifications, completed permitting, and performed construction administration. Listed from upstream to downstream, the following components comprise fish bypass channel:
- New headgate on Dry Creek to direct stream flow to the bypass channel and prevent irrigation water in the canal from entering the bypass channel;
- New headgate on the bypass channel;
- A pool-and-weir fishway downstream of the bypass headgate;
- A concrete box culvert crossing under the Dry Creek Canal; and
- A fishway channel downstream of the culvert which connects to Dry Creek.