Ceremony Marks Start of Impoundment at Nam Ngiep 1 Hydropower Project in Laos

Civil Engineering

Work continues on dam and power station on Nam Ngiep River in Laos. Located about 150 km northeast of the capital Vientiane, operation will begin in 2019.

An impoundment ceremony of The Nam Ngiep 1 Hydropower Project in Laos was held on May 25. Obayashi Corporation is a construction partner in the project. Officials from Laotian national and local governments and members of Kansai Electric Power Co., Inc. and construction companies attended. In all, some 400 persons participated. Aside from celebrating the impoundment, they renewed their determination to finish the project.

The project is constructing a main dam, re-regulation dam,*1 and power stations on the Nam Ngiep River. The river is a tributary of the Mekong. Impoundment began behind the main dam, which will have a reservoir surface area of 66.9 km². Impoundment behind the re-regulation dam was completed in May 2017.

The company behind the project is the Nam Ngiep 1 Power Company, a special-purpose company. It is headed by Kansai Electric Power. Electric power generated by the main dam power station (output 272 MW) will sell to the Electricity Generating Authority of Thailand. That from the re-regulation dam power station (18 MW) will sell to Électricité du Laos. In each case, sales will continue for 27 years.

Yoshiharu Nakamura, General Manager, Overseas Business Division, gives his greetings at the ceremony. Obayashi Corporation is responsible for the civil engineering work in general, including dams and power stations.
The dam body was constructed using the roller-compacted concrete (RCC) method. The RCC method carries zero-slump concrete by conveyor or other means to its position. There, it is spread and roller-compacted by bulldozer and vibrating roller.

The body of the main dam was built with roller-compacted concrete (RCC), which makes fast construction possible. Placement of the body's concrete took only three and a half years after work began in earnest in October 2014. The project is already 95% complete overall. The partners are continuing the remaining work with the aim of starting operation.

Obayashi will continue building dams and other infrastructure for the international community. The international community will benefit by tapping the abundant resources available in each part of the world.

The main dam (167.0 meters high, volume of dam body approximately 2.36 million m3), as seen from upstream. In the distance is the re-regulation dam (20.6 meters high, volume of dam body approximately 60,000 m3). Both are concrete gravity dams.
  • *1 Re-regulation dam
    A dam that temporarily stores power station outflow from the main dam in a regulating pond. It is used to adjust outflow discharge and stabilize water levels downstream