The lake, which is said to contain 65,000 cubic metres (2.3m cubic ft) of water, was discovered last month during routine checks.
The engineers plan to dig a hole into the ice and pump the water away.
In 1892, water from an underground lake flooded the same valley, killing 175 people.
The valley is a popular tourist area and is home to some 3,000 people.
The hidden lake, trapped beneath the Tete-Rousse glacier, holds enough water to form a torrent with mud, rocks and trees that would flood the valley in 15 minutes, potentially affecting 900 families.