Underground power station

An underground power station is a type of hydroelectric power station constructed by excavating the major components (e.g. machine hall, penstocks, and tailrace) from rock, rather than the more common surface-based construction methods.

One or more conditions impact whether a power station is constructed underground. The terrain or geology around a dam is taken into consideration as gorges or steep valleys may not accommodate a surface power station. A power station within bedrock may be more inexpensive to construct than a surface power station on loose soil. Avalanche-prone valleys often make a surface station unfeasible as well. After World War II, large hydroelectric power stations were placed underground more often in order to protect them from airstrikes.