Underground Hydroelectric Power Plants

In recent years a number of underground hydroelectric power stations have been built, mostly in Europe, and many others are under construction. While the last war has undoubtedly had some influence in making substantial protection of generating facilities seem desirable, it is pointed out that underground stations have been built long before the war, and that under certain circumstances there may be valid technical and economical reasons for the choice of this type of construction. Advantages that result from underground locations are discussed, and special emphasis is given to the points which need attention in the design, such as access and safety features, insulation, and ventilation. Several representative underground plants are described in some detail.