Virginia has received $729 million in federal money that advances a plan to boost train capacity over the Potomac River and grow passenger rail operations within the decade, members of the state’s congressional delegation announced Thursday.

The grant will support construction of a new Long Bridge, which is projected to cost nearly $2.3 billion, according to the Virginia Passenger Rail Authority. The federal aid is critical for filling a funding gap that officials had warned could put the project at risk for delays.