Nậm Phak Hydropower Project (Paksong District, Champasak Province, Lao PDR) is a group of diversion-type hydropower plants with very high heads. The VCE–Artelia (France) joint venture is responsible for civil works design, with SD5 as the EPC contractor. The source article forecast generation commencing in late 2025.
The project comprises 03 main asphalt-core rockfill dams; 02 water transfer systems, comprising 08 small dams in the northern system and 06 small dams in the southern system; and 02 power plants: Nậm Pha, 8 MW, and Nậm Phak, 160 MW.
Nậm Pha–Nậm Phak complex (upper stage): Both dams are asphalt-core rockfill structures. Nậm Pha Dam has a maximum height of 76.6 m and a crest length of 1.4 km. Nậm Phak Dam has a maximum height of 25 m and a crest length of 480 m. The Nậm Pha and Nậm Phak reservoirs are linked by an interconnecting channel. Their combined total storage at normal retention water level (MNDBT) is approximately 119.5 million m³. A shared spillway tunnel for the 2 reservoirs is located on the right side of Nậm Phak Dam. It has a horseshoe cross-section with D = 7.1 m and a length of 160 m, a Piano-type inlet and stilling-basin energy dissipation.
The water conveyance system on the left side of Nậm Pha Dam comprises an intake structure and a headrace tunnel with D = 4.2 m and a length of 800 m.
Nậm Pha Powerhouse contains 01 horizontal-shaft Francis turbine unit, with an installed capacity of 8 MW and average annual generation of 41 million kWh. Maximum generating head: Hmax = 81.1 m; maximum design discharge through the generating units: Qmax = 11 m³/s.
Phou Pong Dam and Nậm Phak Powerhouse (lower stage): Phou Pong Dam is an asphalt-core rockfill structure, with a maximum height of 60.5 m and a crest length of 400 m. Phou Pong Reservoir has a total storage capacity at normal retention water level (MNDBT) of approximately 1.45 million m³. Water discharged from the upstream Nậm Pha Powerhouse flows directly into Phou Pong Reservoir. A shaft spillway is located on the left side of Phou Pong Dam. Its tunnel has a horseshoe cross-section with D = 6.2 m and a length of 377.5 m. The shaft inlet has D = 18.1 m, with ski-jump energy dissipation.
The water conveyance system at the upstream end of Phou Pong Reservoir comprises an intake structure; a headrace tunnel with D = 3 m and a length of 2905 m; and a very-high-head penstock with D = 3 m and a length of approximately 1.9 km.
Nậm Phak Powerhouse contains 02 vertical-shaft Pelton turbine units, with a total installed capacity of 160 MW and average annual generation of approximately 700 million kWh. Maximum generating head: Hmax = 696 m; maximum design discharge through the generating units: Qmax = 28.4 m³/s.
Contracting entity: Chaleun SeKong Energy (CSE)
EPC contractor: Công ty CP Sông Đà 5
Design consultancy joint venture: VCE and Artelia (France)
Contract No.: 2405/SD5-ART&VCE
Scope of work: In joint venture with Artelia (France), preparation of basic design and technical design for works under Package 1B, comprising 03 main dams; 03 intake structures; the Nậm Phak penstock, powerhouse, tailrace channel and switchyard (TPP); and construction diversion works for the main dams. Preparation of a dam-break analysis report and an emergency response plan.
During the design phase, Artelia and VCE engineers regularly visited the Nậm Phak construction site together to inspect and resolve site issues and meet with the project owner, project management consultant and main contractor.
