Apr 13, 2017

Hitachi Zosen Receives Order for Hydraulic Gate and Penstock for Laos--First Japanese Company to Build Cofferdam in a Dam Redevelopment Project Abroad

Hitachi Zosen Corporation has received an order from Hazama Ando Corporation for the construction of a hydraulic gate and penstock in the Nam Ngum 1 Dam hydropower expansion project, in the Lao People’s Democratic Republic. Hitachi Zosen is set to be the first Japanese company to build a cofferdam in a dam redevelopment project abroad.

■Project outline
The hydropower expansion project seeks to add one power generation unit to the existing Nam Ngum 1 Dam, situated some 65 kilometers north of the Lao capital of Vientiane. The increased output capacity will meet peak demand in the Vientiane capital area. The project is funded by the Japanese government’s official development assistant (ODA) loan scheme. Hazama Ando is responsible for construction work overall, and contracted Hitachi Zosen to carry out production and on-site installation of the cofferdam, hydraulic gate, and penstock.
Hitachi Zosen plans to bore through the existing dam body and install a steel cofferdam, enabling dam operations to continue during construction work. The technology offers another significant advantage for extension work on the existing dam, namely minimal environmental and social impact on the reservoir and areas downstream of the dam. Hitachi Zosen will be the first company based in Japan to use this technology abroad.

1. Client: Hazama Ando Corporation
2. End user: Electricite du Laos
3. Location: Vientiane Province, Laos
4. Description:
(1) Cofferdam (bulkhead construction)
(2) Screening
(3) Water intake gate (W 4.5 x H 5.5 m) x 1
(4) Repair gate (W 4.5 x H 5.5 m) x 1
(5) High-pressure penstock (diameter 5.5 m–4.5 m, L 42.5 m) x 1
5. Delivery: April 2020

■Nam Ngum 1 Dam
Construction of the Nam Ngum 1 Dam and hydropower station began in the 1960s with support from the Japanese government in the form of grants and yen loans. The immense reservoir boasts an area of 7 billion square meters and a storage capacity twice as large as Lake Inawashiro, the fourth largest lake in Japan. It sends a stable supply of water year round to the hydro power station, which is expected to meet peak demand for electricity in the capital of Vientiane during the dry season. The existing dam was completed by Hazama-Gumi (currently Hazama Ando) in December 1971.

■Hitachi Zosen hydraulic gates and penstocks
Hitachi Zosen launched the hydraulic gate and penstock business in 1900, and has since delivered numerous hydropower-related structures, including movable gates, both in and outside Japan. Recent years have seen the need for construction of new dams replaced by extensions to improve the function of existing dams. Cofferdams are integral to dam redevelopment projects, as they provide a work area for the installation of water outlet and intake structures below the surface of the reservoir without reducing the water level of the dam. Hitachi Zosen has a track record in cofferdams, including the 2015 Tsuruta Dam redevelopment project in Satsuma-gun, Kagoshima, and hopes to put its expertise to use in other future projects across the globe.