Kazunogawa Hydroelectric Power Plant, Japan

The Kazunogawa Power Plant is a 1600MW underground pumped storage plant constructed by the Tokyo Electric & Power Company (TEPCO) in Japan’s Yamnashi Prefecture. The project was ordered to meet peak demand, which was reaching record levels when the project was first planned in 1995. It was also needed for the utility company to cope with the rapidly increasing differences being experienced between daytime and nighttime differences in power demand.

The project included a range of construction work, with the 160MW being generated by the world’s then largest reversible pump turbines (four 400,000kW units). The first unit was commissioned in December 1999. The second began operations in June 2000, and the fourth in July 2000. When completed, the plant was the largest hydro plant in Japan, although not long after completion TEPCO finished a much bigger 2,700MW pumped storage plant in Kannagawa.


The plant has upstream and downstream dams, with main / temporary networks connecting them to the station. The discharge capacity is 280m³/s. The dams are roughly in a straight line, and are 5km upstream and 3km downstream from the power station. The cavern for the underground power station is approx. halfway between the upper and lower dams and is 500m below the surface. It is 210m long by 54m high and 34m wide, with an excavation volume of 250,000m³ (big enough to hold three jumbo jets).

The site is located at the eastern part of the Shimanto strata, and was formed about 65 million years ago. There were initial ground stresses and problematic rock joints. To detect potential problems, 1,300 sensors stretched through the surrounding bedrock. Careful rock analysis and monitoring was required before and during construction because of the difficult geology and size of the excavation project. Before work on the main gallery began, a 1/5 scaled-down model was excavated for detailed analysis and also to be used later as a temporary storage for spoil.

A 714m head is provided between an upper reservoir with an 87m rock fill dam and a lower reservoir with a 105m concrete gravity dam. The upper reservoir is connected to an underground power station by a headrace tunnel and penstocks, and a tailrace tunnel links the power station with the lower reservoir. The downstream dam has a volume of 620,000m³.

A consortium of Hitachi and Mitsubishi Heavy Industries won the Kazunogawa equipment order. This marked another victory for the Japanese hydro industry, which has been much less reliant on foreign partners than the nuclear and gas-fired segments. Similarly, the lead Kannagawa contract went to a consortium of Hitachi, Mitsubishi Heavy Industries and Toshiba.

Efforts were made towards co-existing with the local community, and minimizing the effect on the environment. The construction site was for example opened to the media and information disclosed to them.


The power generating industry in Japan is dominated by ten vertically integrated general electric utilities. Revision of the Electricity Utilities Industry Law in December 1995 made it possible for Independent Power Producers (IPP) to operate more effectively in the power generation market and to act as electricity wholesalers.

Japanese demand for electricity is only expected to grow at 2.1% per annum and international pressure on Japan to reduce greenhouse gas emissions is prompting the authorities to promote energy saving and an alternative lower target for power consumption. However, the new competitive situation in the power generation industry provides potential new market opportunities.

Pumped storage schemes account for about 8% of all power plant currently planned or under construction in Japan.