The Solomon Islands government has given the go-ahead for the controlled release of millions of litres of untreated waste water into a Guadalcanal river.
Recent rains have filled the tailings dam at the Gold Ridge mine to dangerous levels, prompting the emergency measures.
The water contains toxic sediment, but the mine's owner, Gold Ridge Mining Ltd, says a controlled de-watering will avoid an uncontrolled spill, which would have disastrous effects for downstream communities.
The company has spent the past several weeks undertaking an awareness campaign, and delivering 100 fresh water tanks to the communities that rely on the river.
The World Health Organisation has declared the dam's water safe for washing, fishing and gardening, but not for drinking and cooking.
The director of the environment ministry, Joe Horokou, says the water level in the dam should have reduced by a metre when the licence expires in 47 days.