Nam Theun 2 Hydroelectric Project, Laos

Aurecon to undertake tender for hydropower project

  • Water diversion for power generation
  • Aurecon's role: tender, preliminary and detailed design and documentation
  • Client: ITD-NCC Joint Venture

Nam Theun 2 is a 1 086 MW hydropower project located in Khammouane Province, PDR Lao. The project was a trans-basin scheme, diverting water from the Nam Theun River catchment into the Xe Bang FaI River system, producing 348 m of net head to drive the generating units.

Aurecon was engaged to undertake tender, preliminary and detailed design and documentation of the downstream channel works for the Nam Theun II Hydropower Project. 

Services included:

  • Assessment of the hydraulic performance of the channel using Manning’s equation and HEC-RAS models
  • Design of riprap and gabion mattress channel linings to prevent scour in high gradient/velocity sections of the channel
  • Assessment and design of protection works required to prevent scouring at two junctions where natural streams merge with the artificial channel
  • Design of control weir structures to regulate velocities in the open channel to acceptable levels, thus preventing scour along the channel
  • Assessment and design of an aeration weir intended to aerate water discharged from the regulating dam, thereby maintaining water quality
  • Tunnel analysis and design of the associated energy dissipation structure, including a weir and hydraulic jump dissipation basin
  • Design of a diversion waterway, including stepped cascade and culvert structures, to divert a natural waterway beneath the regulating dam discharge channel
  • Design of an inverted siphon to convey flow in the channel underneath a natural river
  • Design of local drainage and irrigation infrastructure, including side drains, culverts, inverted siphons, and irrigation water outlets.

Detailed design for the CW3 Civil Works Package included civil, structural, hydraulic modelling, mechanical and electrical design of:

  • Regulating Pond
  • Regulating Dam (130 m Concrete and 400 m Earth Fill)
  • Downstream Channel (27.3 km long trapezoidal channel – Base width varies from 20 m to 83 m)
  • Hydraulic Structures along Downstream Channel, including:
    • Ban Itak Crossing – 3 level grade separation structure (Creek – Downstream Channel – Road)
    • Nam Gnom Siphon (siphon under existing river for Downstream Channel)
    • Aeration Weir
    • Tunnel (640 m)
    • Roads and Agricultural bridges
    • Confluences with existing rivers

Aurecon applied a programme of numerical modelling (1-dimensional, 2-dimensional and computation fluid dynamics), and physical model testing to facilitate the hydraulic design of the channel, rock protection, hydraulic structures and river confluences. The modelling was also used to investigate air entrainment and ensure that water quality criteria would be satisfied.

Aurecon’s integrated team of hydraulic specialists, structural and civil designers, geotechnical engineers, and geologists worked with geomorphologists and international dam experts to deliver an innovative, effective design for the project.

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