SECAUCUS — Engineering work can begin on the proposed Gateway train tunnel under the Hudson River — an alternative to the ARC tunnel canceled last year by Gov. Chris Christie — now that Congress has approved $15 million toward the project.

The commuter train tunnel proposed by Amtrak would link Secaucus to the south side of New York Penn Station in Midtown Manhattan.

President Obama was expected to sign the legislation today, which would allow Amtrak to start design and engineering work. The House and Senate approved the measure yesterday afternoon and last night.

"Transportation is the lifeblood of New Jersey’s economy, and the Gateway Tunnel will be a critical improvement for commuters in our state and across the region," U.S. Sen. Frank Lautenberg (D-N.J.) said in a statement last night. "The existing tunnel is more than a century old and not capable of adequately servicing our state’s growing number of commuters."

"New Jersey’s economic opportunities are being dampened by clogged Hudson River crossings," added U.S. Sen. Robert Menendez (D-N.J.). "This funding allows the Gateway project to move forward, and without a new tunnel we risk continued economic stagnation for the state."

Although Amtrak was hoping for $50 million, the $15 million is an important first step for the tunnel — an alternative to the Access to the Region’s Core tunnel terminated last October. Christie then cited concerns about cost overruns and a lack of rail connections for the $9.8 billion tunnel from Secaucus to West 34th Street in Manhattan.

Meanwhile, New York is studying an extension of its No. 7 subway train — which brings Mets fans to Citi Field in Queens — westward to Secaucus. No federal funding has been approved for that plan.

Christie has been receptive to both alternative tunnel proposals.

The Gateway Tunnel would allow another 13 NJ Transit trains during peak hours — from 20 to 33 — and eight more Amtrak trains. It was expected to cost $13.5 billion and take nine years to complete.

Related coverage:

• Congested Northeast rail corridor gets $450M to ease bottlenecks

• N.J. senators, Amtrak official to announce new commuter train tunnel project across the Hudson

• Christie is 'thrilled' with Gateway tunnel proposal, takes credit for billions saved by canceling ARC tunnel