Muncey joined Gleeson in 1997 as deputy managing director of the southern division from regional contractor Llewellyn. He described the post as his "dream job". "I took the decision that this was the company I wanted to be chief executive of. I would have been disappointed if I hadn't got it."
Dermot Gleeson, chairman of the group, said Muncey's appointment reflected his success in increasing the turnover and profitability of the southern division.
"His appointment is all the more meritorious for being achieved in competition with both internal and external candidates," he said.
The consortium, called Stirling Water, will split £1.8bn of work with United Utilities, which is working with contractor Galliford Try. The contract will start in April and last four years.
Work on the framework deals will include upkeep of all water and sewage treatment plants, coastal outflows and mains renewals.