The project located at the upstream of Tachia River, mountainous area of central Taiwan. The newly-built underground construction includes underground switch yard, elongated section of tailrace tunnel and access roads. The geology of the underground construction site consists of eastward dipping metamorphic sandstone and slate with numerous folds and shearing structures which leaded to substantial difficulty. It includes slow excavation, tunnel subsidence, and collapse. Still after remarkable efforts of teamwork, all the disadvantages were conquered eventually. 