Little Falls Dam Fish Passage: Section 1135 Integrated Project Modification Report and Environmental Assessment




canal, environmental assessment, fish passage, labyrinth weirs, Little Falls Dam, Potomac River, upstream, vertical slot, water supply, weir


None supplied. From executive summary: Little Falls Dam, also referred to as the Brookmont Dam, is located on the Potomac River in Montgomery County, Maryland, approximately 1 mile upstream from the border between Maryland and the District of Columbia and approximately 75 feet upstream of the Chesapeake and Ohio Canal Dam. The Little Falls Dam provides a water supply storage pool on the Potomac River for the Washington Aqueduct for distribution to the Washington, D.C., metropolitan area. The existing vertical slot fishway, which was constructed at the same time as the dam, was never successful. The plan that maximizes the qualitative and quantitative environmental outputs and that efficiently and successfully meets the environmental and technical criteria for this project site is the labyrinth weir notch. The notch structure with three labyrinth weirs is the most justifiable solution to the fish passage problem at the dam. After extensive hydraulic and biological analyses and coordination with the Little Falls Task Force, it was determined that the proposed solution was the preferred alternative. The local sponsor and numerous resource agencies agreed that this solution will result in the highest environmental returns, the longest project life, and the least amount of maintenance.

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