A $511 million loan approved by a New York environmental agency to help fund the construction of a new $4 billion Tappan Zee Bridge was rejected almost entirely by the U.S. Environmental Protection Agency.

The loan was intended to drive down borrowing costs for the replacement span being built across the Hudson River, with half of it being provided at zero interest. The agency, the Environmental Facilities Corp., approved the borrowing in June, saying it could use the funds from a program that targets clean-water projects.

The EPA said today in a letter to state officials that building a new bridge doesn’t fit the intention of the program, which is backed by federal dollars. The agency, citing the U.S. Clean Water Act, said only $29.1 million could be allowed.