Upper Salmon Falls B-Plant Forebay, also known as Upper Powerhouse Forebay Dam, is a private hydroelectric structure located in Twin Falls, Idaho along the Snake River. Built in 1947 by EBASCO, this concrete gravity dam stands at a height of 70 feet and has a storage capacity of 90 acre-feet. With a low hazard potential, the dam features a controlled spillway with a width of 45 feet and two slide (sluice gate) outlet gates.

Operated by the Federal Energy Regulatory Commission, Upper Salmon Falls B-Plant Forebay plays a crucial role in generating hydroelectric power in the region. Its maximum discharge capacity reaches 6500 cubic feet per second, serving as a key component in the local water resource and climate control infrastructure. Although its condition assessment is not currently available, the dam's risk assessment indicates a very high level of risk, highlighting the importance of ongoing monitoring and management measures to ensure its continued safety and functionality.