The Cord leader claimed the project began in 2014 and has been classified by the World Bank as a Category A project, which means the sensitive and devastating effects are irreversible.
He said former Environment minister John Michuki (now late) had raised objections to the project.
He further claimed that the Murang’a County Assembly had also raised concerns about the project and mandated its water, energy, forestry, environment and natural resources committee to investigate it.
Mr Odinga opposes the project though he unveiled a plan for it on September 18, 2012 when he was prime minister.
The project involved a first phase of sinking wells in Kiunyu and Ruiru to increase water supply by 64,800 cubic metres per day.
In phase two, a tunnel was to be constructed to divert the Irati, Gikigie and Maragua rivers, while the third phase involved building the Maragua and Ndarugu dams.