Pöyry, (formerly Electrowatt), has been awarded an US$11.4M hydropower contract in Laos.

Works are just getting underway on the remote site of the Nam Ngum II hydropower scheme roughly 100km north of the capital city, Vientiane. Although in Laos, the project is being built to produce 600MW of energy for the Thai electricity grid as all the output will be sold to the Electricity Generating Authority of Thailand, (EGAT).

Pöyry’s Energy business division has been commissioned by Thailand’s SouthEast Asia Energy Ltd. to serve as independent engineer during the project execution. It has been involved in the development of the project since 1994 and has completed several technical studies on the scheme.

The project comprises a river diversion, power waterway system and access tunnels in sandstone and siltstone. T&TI was told by Pöyry that the river diversion consisted of two tunnels, both 11.7m in diameter, 1.1km and 1.2km long. A 600m long, 10.7m diameter concrete lined tunnel, together with three steel lined, 5.35m diameter inclined shafts, all 290m long make up the power waterway system.

Main contractor for the works is Ch. Karnchang (Lao) Co. Ltd., with Right Tunnelling Co. Ltd. as subcontractor. Drill and blast excavation will be followed by installation of rockbolts, mesh and shotcrete as temporary ground support. For the diversion tunnels, the permanent lining will consist of partially reinforced concrete. The power tunnels will be lined with reinforced concrete and a steel lining.

Construction started in December last year, with the tunnels due to be complete by November 2008. T&TI was told that currently works are focused on the heading excavation for the access tunnels. At the outlet end, the heading of one tunnel has advanced 250m, with benching about to get underway. A second tunnel heading has advanced 50m. For the inlet end of the works, a portal is just being completed and for another tunnel the heading has just started and had advanced 15m in mid-June.

The nature of the location means several logistical challenges, with some equipment brought to site by ferry across Nam Ngum lake. In addition, the project has built several bridges to ease logistics.

The engineer, procure and construct contract has been financed by the owner with assistance from Thai banks.