Massachusetts moved a step closer to replacing a pair of 1930s-era bridges connecting Cape Cod and the mainland with two new spans under a deal inked with the U.S. Army Corps of Engineers.

The Massachusetts Dept. of Transportation will build a pair of new, modern bridges over the Cape Cod Canal, with the federal government on the hook to pick up the tab, under a memorandum of understanding (MOU) between the state and the Corps.

Demolishing and replacing the two 85-year-old bridges will cost anywhere from $1.45 billion to $1.6 billion, according to the Corps, which for decades has controlled the canal and the bridges over it.

Once the construction of the two new bridge is complete, MassDOT will take over ownership and management of the two spans under the agreement, or MOU, signed Wednesday.

The project, in turn, has united the state’s Republican governor and its all-Democratic Congressional delegation, who are vowing to work together to get the project funded and built. “The bridges over the Cape Cod Canal are among the most important transportation structures in the entire Commonwealth,” said Gov. Charlie Baker (R), noting the agreement “puts us on a path to replace both.”

The Corps and the Public Works Administration built the two bridges at the height of the Great Depression, part of a massive surge of infrastructure spending under the New Deal.

But the bridges, the only highway connection between Cape Cod and its 215,000 residents and the mainland since they opened in 1935, have been overtaxed and outmoded for decades, the choke points for miles-long traffic jams during summer tourism season.

Still, many details remain to be hammered out.

There is no final design yet for the two bridges, just the Corps’ recommendation, released last fall, that two new bridges be built.

The Corps concluded that renovating the two existing bridges would cost $1.5 billion, as much or more than building anew.

The study called for the two bridges to have four lanes each, but wider than they are now, as well as two auxiliary entrance and exit lanes. In addition, the bridges should also have extra space for bicyclists and pedestrians, the Corps suggested.

While the agreement between state and Corps officials calls for federal funding of the project, there is no specific funding attached to the proposal.

Members of Massachusetts’ Congressional delegation, at the rollout event for the new agreement, vowed to pursue federal money for the bridges, possibly as part of long-discussed, $1.5 trillion national infrastructure bill.

“By fulfilling and building on this federal-state-local partnership, we will deliver two new bridges for the Cape & Islands’ economy and residents,” Sen. Edward Markey (D) said in a press statement. “As Congress debates an infrastructure package in the weeks ahead, I will fight to secure the federal funding we need to complete this essential project.”