WASHINGTON -- Recently enacted legislation setting transportation policy for five years will make it easier to build the new rail tunnels under the Hudson River, Amtrak President Joseph Boardman said Tuesday.

Boardman told the Senate Commerce Committee's surface transportation subcommittee that the Gateway project is Amtrak's "top priority among a long list of major priorities."

The legislation sets aside $305 billion for roads, bridges, transit and railroads over five years, and makes changes to federal railroad loan programs that will enable Amtrak to get more funding for the tunnel and the replacement of the Portal Bridge over the Hackensack River.

Construction of the new tunnels will enable Amtrak to close and repair the existing Hudson River tunnels that were damaged by Hurricane Sandy.

Boardman said the new tunnel's environmental impact study is planned to begin in April, and a Gateway Development Corporation has been formed to build the project. Even so, Boardman said, "major federal funding is needed to advance the program."

He said the transportation bill "will allow us to create a pathway to financing it."

The federal government has agreed to pay half the cost of the project.

"We have begun to take on the challenge of bringing the Northeast Corridor toward a state of good repair," said U.S. Sen. Cory Booker (D-N.J.), the top Democrat on the subcommittee.

The measure earmarks $8 billion for Amtrak over the next five years and requires the railroad to spend profits earned along the Northeast Corridor to improve service between Washington and Boston rather than use them to subsidize money-losing routes elsewhere.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant. Find NJ.com Politics on Facebook.