Auckland's water provider Watercare has signed a 10-year infrastructure contract with Fletcher Construction and Fulton Hogan.
Auckland's water provider said the $2.4b contract would give longer-term security of work for the construction companies and result in cost savings for the council agency.
In the past Watercare has contracted jobs on a case-by-case basis.
Construction sector firms have been concerned about a lack of large infrastructure projects in the pipeline.
Signing the agreement in Auckland this morning, the three parties said the decade-long contract was a win-win, with cost-savings and greater business security.
They have committed to Watercare's goals of a 40 percent carbon reduction and a 20 percent cost cut, both by 2024.