The Nam Pha Gnai hydropower plant in Laos, which was designed by Entura, is fully operational following completion of construction last year.
Located in the Nam Ngum river basin at the convergence of the Nam Ngum, Nam Pha Noi and Nam Pha Gnai rivers, the 19.2MW run-of-river hydropower project comprises a 70m-high concrete gravity dam, 1.2m-long headrace tunnel, 5.1km-long channel, forebay, 280m-long surface penstock and three Francis turbines (2 x 7.4 MW + 1 x 4.4 MW) housed in a surface powerhouse.
Construction of the project began in October 2014 with an investment of about US$68 million by the DSK Group. Entura was awarded a contract for Owner’s Engineer services in 2014.
“Entura’s technical expertise and excellent performance in the preliminary stages led to its subsequent engagement for the detailed engineering contract,” said Mr Sayasith Sanakeo, Managing Director, DSK Group. “Entura’s expertise was a key factor in the smooth progress of construction and the optimisation of many elements of the project, resulting in significant savings on excavation and concrete.”
To reduce excavation and concrete, Entura used an arch profile for the dam, sloped the foundation level upstream, provided a cantilever crest upstream, and used an unconventional gate structure and arrangement.
Entura also significantly reduced excavation by revising the proposed layout of the approach road and canal, ensuring slope stability in the headworks area through phase 2 software analysis, and relocating the powerhouse to decrease rock excavation and the length of the tailrace.
In addition, costs were reduced by using concrete pipes (cast in situ) rather than concrete-pier-supported bridges to enable canals to cross streams.
“We are pleased to support Laos in developing its hydropower sector,” said Entura’s Director International Business, Ajay Sharma. “In our work on this project, we made very high priorities of protecting the natural environment, avoiding adverse social impacts, and ensuring sustainability into the future.”
A commissioning ceremony took place in November 2019 in Pha Noi village, attended by government officials, local authorities and business operators, as well as Entura representatives.
Entura has also supported a number of significant hydropower projects in Laos with feasibility studies and owner’s engineer services including Nam Long 2, Nam Long 3, Nam Ngum 2 and Nam Ngum 3 hydropower projects. As well, Entura has played a key role in drafting new dam safety guidelines to form part of the Laos Electrical Power Technical Standards.