The project, which is being constructed specifically to provide over-dam passage for bull trout, was developed as a collaborative effort through an inter-agency, multi-disciplinary team composed of PPL Montana; the US Fish and Wildlife Service; Montana Fish, Wildlife and Parks; Montana Department of Environmental Quality; the Federal Energy Regulatory Commission; the Confederated Salish and Kootenai Tribes; GEI Consultants, and others.

GEI provided technical assistance to the team by performing fish behaviour studies in the tailrace and assessing the feasibility of a range of alternatives. Study results were presented to the inter-agency team for a consensus decision on a preferred alternative. GEI provided further support to the owner and inter-agency team by designing the facility and assisting with construction oversight.

The construction of the Thompson Falls Upstream Fish Passage project will allow migratory fish to swim upstream of a dam on the Clark Fork River in Thompson Falls, Montana for the first time in nearly one hundred years. The bull trout, which has been identified as a threatened species by the US Fish and Wildlife Service since 1998, was once common throughout the Pacific Northwest, but is now found in small numbers in their native range including the Clark Fork River in western Montana. Because of their dependence on a high quality habitat, the existence of bull trout is seen as an indicator of stream health. A “threatened” species is defined as one that is likely to become endangered in the foreseeable future.

The new fish ladder facilities will allow bull trout to ascend 48ft over the existing dam structure through 48 individual concrete step pools. The facilities will also have a fish lock, which is an elevator-like structure that can lift fish up to a sampling platform where biologists have the ability to physically track the success of the project and obtain valuable scientific data. The project will allow fish access to hundreds of miles of free-flowing rivers and spawning tributaries in the Clark Fork River. Data generated at the project will be used by the inter-agency team to enhance bull trout restoration efforts in the Clark Fork River basin.

Construction of the fish passage project began in July 2009 and is anticipated to be complete during the summer of 2010.