Laos dam construction and collapse

Thursday, July 26, 2018

A dam under construction in Laos as part of a hydropower scheme has collapsed, causing flooding and damage.

At issue is the Xe-Pian Xe-Namnoy project, a 410-megawatt hydroelectric power project under development for Xe-Pian Xe-Namnoy Power Company (PNPC). PNPC is a joint venture among the government of Laos and construction and power companies from South Korea and Thailand. The project, whose construction costs are estimated at about $1 billion, involves the construction of three primary dams to form reservoirs. Construction of the system was reportedly 90% complete, with commercial operation projected for 2019, and an agreement in place agreement to export 90% of project power to Thailand. The project has been touted for the degree of international investment involved, although some have criticized the project for insufficient local benefits.

From an engineering perspective, the project's primary dams impound water in a large reservoir. The project also includes three auxiliary "saddle dams" near several heads of the reservoir, essentially to prevent the reservoir from spilling down the impoundment's back side as it fills.
A map of the project, found at
Project maps posted online by PNPC show saddle dams on three of the main reservoir's western branches.
Another project map found at

One of these smaller saddle dams reportedly failed on July 23, 2018, allegedly due to severe rains. Saddle Dam D -- a facility 8 meters wide, 770 meters long and 16 meters high -- was built to support water diversion around the project's reservoir. But the structure reportedly fractured, causing water to spill downstream to the Xe Pian river outside of the project's intended path of water flow. According to the prime minister of Laos, at least 26 people have died and 131 are missing from the resulting flooding, and several villages .

Response and recovery actions are ongoing. The dam collapse highlights the importance of safety in dam construction and reservoir operations, as did the February 2017 failure of the Oroville Dam's spillway in California.

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