Environmentalists and NGOs are threatening to sue developers of a controversial hydropower dam, claiming the project would cause irreversible damage to the Mekong River.

The Don Sahong dam, a 260-megawatt project proposed on a site less than two kilometres north of the Cambodian-Lao border, is expected to begin construction this month.

Members of Save the Mekong Coalition gathered yesterday at a conference urging a moratorium on the dam until further studies could be conducted.

“There’s a huge population that relies on this river. If they really build it without conducting proper impact studies it will be irresponsible to the 60 million people who live along the river,” said Pen Somany, executive director of the Cambodian Volunteers for Society.

Last month, the Mekong River Commission made public an environmental impact assessment report prepared by a private company for Malaysian developer Mega First Corporation Berhad.

Contrary to the outcry from environmental groups, the report says there will be no significant negative impacts.

“What they say in their report is just what the dam builders want to hear,” said Meach Mean, a coordinator at the 3S Rivers Protection Network.

The coalition is instead calling on the governments that will be affected by the project – Cambodia, Thailand, Vietnam and Laos – to each conduct independent assessments and then weigh the benefits against the repercussions.

“We want a very detailed study focused on how the dam will impact the life cycles of the fish and how it will change the natural complexity of the river system,” said Chhith Sam Ath, executive director of the NGO Forum on Cambodia.

On Friday, the coalition sent a letter to the governments of Laos, Cambodia, Vietnam and Thailand seeking intervention and cancellation of the project.

They haven’t received a reply, and say they are considering legal action as a next step.

“We are advocating for this, so that we can know the effects before it ends up impacting people’s food security and economic livelihood for generations,” said Youk Senglong, program manager of Fisheries Action Coalition Team.