Comptroller Tom DiNapoli today signed off on a $3.14 billion contract to build a replacement for the aging Tappan Zee Bridge.

In a letter to Thruway Authority Director Tom Madison, DiNapoli writes that the authority “must assert effective supervision of and accountability” during the construction project.

The Thruway Authority’s board last month signed off on a bridge design proposed by Tappan Zee Constructors, a joint venture of Fluor Enterprises, Inc., American Bridge Company, Granite Construction Northeast, Inc. and Traylor Bros., Inc.

“Replacing the Tappan Zee Bridge is New York state’s largest single infrastructure project and is vital to our economic prosperity,” DiNapoli said in a statement. “To protect taxpayers, my office will closely scrutinize the Thruway’s oversight of the construction of the new bridge. The Thruway Authority is responsible for proposing a financing plan and must live up to its commitment to pursue the lowest cost options and ensure that its customers are paying the lowest possible tolls. Every effort must be taken to minimize costs for this project and protect the long-term fiscal health of the Thruway system.”

Tappan Zee Bridge Contract by Nick Reisman