Projects>SH Dam Removal
Confluence researched and prepared a Conceptual Design and Planning Report for the removal of SH Dam on the Tongue River in Custer County, Montana. Confluence conducted a topographic survey of the dam, river bed profile, and cross-sections upstream and downstream of the dam. The survey data was used to estimate the quantity of sediment that had accumulated in the impoundment created by the dam. We also collected sediment samples for sieve analysis to estimate the potential mobility of stored sediment once the dam was removed. Confluence’s analysis also included examining potential impacts on downstream reaches by transport and deposition of sediment following dam removal. Removal alternatives were assessed for potential impacts to channel stability, fish and wildlife resources, and wetlands. Hydrologic records were analyzed to determine the most appropriate time to remove the dam and ensure adequate transport and distribution of stored sediment downstream to minimize adverse impacts to aquatic resources and water users. The feasibility report Confluence prepared was used to solicit Montana legislative funding for final design and removal of the dam.