PPL Montana Thompson Falls Upstream Fish Passage

In 2010, the country built its first full height 48-step-pool ladder, designed specifically for bull trout, and commenced operations at the Thompson Falls Dam. During the first operating season, over 1,800 fish ascended the ladder, including two bull trout.

From the initial stages, Steigers Corporation’s fisheries biologists and scientists participated in the development of studies, data analysis, biological monitoring, report preparation, and regulatory compliance efforts. In addition, we contributed to preparation and technical review of the Biological Evaluation (BE). The BE required extensive coordination with federal, state, tribal, and local entities and consultation with U.S. Fish and Wildlife Service (USFWS).

Prior to construction, our scientists and managers coordinated with agencies, engineers, and the owner to identify regulatory compliance requirements and prepared the necessary permit applications for submittal to the U.S. Army Corps of Engineers, Montana Department of Environmental Quality, Sanders County Flood Plain Administrator, and Green Mountain Conservation District. Construction commenced on schedule in spring 2009 and was completed in fall 2010.

Steigers Corporation also developed a 10-year plan evaluating the upstream fish passage efficiency, including short-term and long-term studies to assess optimum operations such as attractant flow and weir mode (v-notch versus orifice mode). In addition, we provided statistical analysis and prepared an annual report for submittal to FERC and other agencies that summarized annual fish passage numbers, species, timing of ladder ascent, recaptures, and estimate of fish that fallback via spill or turbines.