Diversion design and construction of Longtan Hydropower Station

The construction diversion of Longtan Hydropower Station is large in diversion tunnel scale, complicated in operation conditions, and high in cofferdam Its diversion tunnel is the largest section pressured tunnel in the built and under build projects at home at present, with the highest water head during its blockage period The maximum height of the cofferdam is 82 7 m The tunnel diversion is divided into three periods of first stage diversion, provisional flood retaining during construction period and initial power generation When the river is closed, the diversion design flood standard is 20 year flood and the cofferdam water retaining standard is 10 year flood The diversion tunnel is excavated by three layers with the height of about 8～10 meters each The right and left diversion tunnels were checked and accepted The river closure can be carried out on schedule