Thompson Dam in Western Montana

The plant consists of a main dam and a dry-channel dam with an island in between. Both dams are used to regulate the reservoir, which has a storage capacity of 8,300 acre-feet, and control flow during high spring runoff. The main dam is 913 ft long and 32 ft high.

Thompson Falls is classified as a "run-of-river" project because it can generate electricity using the water that flows down the river, without the need to store additional water supplies.

The Clark Fork River at Thompson Falls, Montana was originally a natural waterfall. After the dam was built, west slope cutthroat trout (a species of special concern), the threatened bull trout and other fish species instinctively jumped on the rocks to get upstream. PPL Montana has installed a mechanism to help fish reach the river on the upstream side of the dam. This temporary 43-foot-long, 2-foot-wide ladder is attached to a trap. Fish captured in the trap can be trucked above the dam and released to assist in their passage to upstream locations.

In 2005, PPL Montana began using surgically implanted radio transmitters to track the fish during their migration and their approach to the dam. The process is helping PPL Montana and state fish biologists to develop a recommendation for a permanent passage for the trout.

The island at Thompson Falls, Montana contains a public park with hiking trails, picnic tables, and many scenic overlooks. The site is a wonderful place to explore, and is conveniently located just a minute or two from Main Street.