Army soldiers and local villagers have finished digging through rocks and boulders to drain a glacial lake just south of Mount Everest, bringing the water to a safe level and possibly preventing an outburst that could have flooded several villages, officials said Tuesday.

Lt. Col. Bharat Lal Shrestha, who led the team of soldiers during the six-month project, said they were able to lower Imja Lake’s water level by 3.4 meters (11 feet), averting the immediate risk of an outburst.

Imja, at an altitude of 5,000 meters (16,400 feet), is considered one of the most likely glacial lakes to burst its banks because it keeps rising every year from melting snow and ice from the Himalayan mountains.

Forty soldiers working with around 100 villagers dug through boulders and rocks to build an outlet to drain out as much as 4 million cubic meters (141 million cubic feet) of water from the lake.

The soldiers, who camped out in tents and worked through the rainy season, battled high-altitude sickness, freezing temperatures, snow and strong winds.

“It was physically tiring working in an area where there is about half the oxygen available, but we were able to complete the task and ensure the villagers and visitors are safe,” Shrestha said.

The team was sent after years of warning from environment groups that the glacial lake, which is up to 150 meters (500 feet) deep, could burst anytime, causing flash floods that could sweep many villages.

A devastating earthquake that struck Nepal in April 2015 is believed to have made the lake even more unstable.

Shrestha said at least five villages right beneath the lake with a total of about 8,000 people would have been in danger of being flooded if the lake had burst its banks.

Thousands of Western and Nepalese tourists visit the area during the autumn and spring to trek the trails to the Mount Everest base camp.