The construction of Don Sahong Dam, the second of 11 potential and controversial Mekong mainstream dams, is moving ahead without approval from Mekong River Commission members, according to a conservationist group report.

Located less than two kilometres from the Cambodian-Lao border, the dam has been slammed for its likely impact on Cambodian fisheries – as well as those of Laos, Thailand and Vietnam.

The 240MW dam is being developed by Malaysian engineering and construction company Mega First Corporation Bhd (MFCB), with most of the electricity expected to be sold to Thailand and Cambodia.

Ame Trandem, Southeast Asia program director for International Rivers, an environmental and human rights organisation, said when the group visited the site last week villagers told them they were recruited by MFCB to place markers around the area that would need to be cleared for the dam’s access roads and bridges to be constructed.

“It is clear the Don Sahong Dam is following the same trajectory that the Xayaburi Dam took, in which secrecy and illicit project implementation topples regional cooperation,” Trandem said yesterday.

The much larger, 1,285MW Xayaburi Dam – the first of the mainstream Mekong projects – was also rumoured to have been preliminarily constructed without prior consultation with other Mekong River Commission (MRC) member states.

Te Navuth, secretary-general of the Cambodia National Mekong Committee, said they have yet to be notified of any preliminary construction of the Don Sahong Dam.

“They should send a request to the four member countries [of the MRC],” Navuth said. “We did not receive any documentation for prior consultation on this project yet.”

Under the 1995 Mekong Agreement, in order to proceed with the construction of such a dam, all member countries must be consulted.

Although the Don Sahong Dam’s 2012 Environmental Impact Assessment report has not yet been released to the public, many are already conscious of the potential threat to fish migration and the vocation of fishermen who depend on the Mekong River.

“The Don Sahong Dam would be an environmental calamity,” said Pianporn Deetes, International Rivers’ Thailand campaign coordinator. “If built, the dam will inevitably and irreversibly block the only channel in the Khone Falls that fish can migrate upstream and downstream in the dry season, leading to serious impacts on fish catches, species and the livelihoods of millions in the region.”

According to the MRC’s Strategic Environmental Assessment, the excavation process, which would require explosives to clear 1.9 million cubic metres of sediment from the riverbed, would devastate the river’s ecosystem, and 60 per cent of the waterflow into the branches of the Mekong River and 10-12 million tonnes of sediment would be diverted into the dam’s head.