Sediment Dredging: Unplugging Ikawa Dam's Bottom Outlets

摘要

When sediment threatened to dog the bottom outlets at the 62-MW Ikawa Dam project in Japan, Chubu Electric Power Co. undertook a massive, first-of-its-kind dredging operation. Utility engineers overcame challenges such as mapping the area, precisely controlling the dredger, protecting downstream water quality, and disposing of the sediment. During the 40 years after the 1957 completion of the 62-MW Ikawa Dam hydroelectric project in central Japan, the effective capacity of the reservoir decreased by about 20 percent (22 million cubic meters), owing to sediment inflow. Most of the sediment accumulated at the base of the dam.