Agency headquarters approves project report, will pursue funding and design.

WASHINGTON — The U.S. Army Corps of Engineers has decided it will move forward with replacing the Bourne and Sagamore bridges, and the federal agency is now working to figure out how the replacement bridges will be designed and funded.

The New England District of the Corps, which owns and operates the 84-year-old bridges that cross the Cape Cod Canal, had recommended in October that the bridges be replaced, saying its preferred design would be two wider bridges that would be built next to the existing spans.

On Friday, the assistant secretary of the Army for civil works approved the final report on the project and agreed that replacement was the most cost-effective long-term solution.

“We look forward to continuing our strategic partnership with Massachusetts Department of Transportation as they conduct a Type, Size and Location Study for the replacement bridges,” Corps spokeswoman Beth Gosselin said in a statement. “We also look forward to participating in future discussions on alternatives and delivery methods."

The Corps had conducted a yearslong study, weighing a major rehabilitation of the bridges against replacement, and found that the continued major repairs the bridges would need would cost more than new construction.

The price tag for two new bridges is about $1 billion.

As recommended, each new bridge would have four travel lanes, two in each direction, and an auxiliary lane on both sides. There also are plans for a median, shoulders and a separate bike and pedestrian lane, which the current bridges do not have. The lanes also would be 2 feet wider than those on the existing bridges.

After the new bridges are completed, the existing spans would be demolished.

“The Bourne and Sagamore Bridges are vital parts of the Cape’s economy and way of life, and also serve as crucial evacuation routes should an emergency arise,” U.S. Sen. Edward Markey, D-Mass., said in a statement. “I have long believed that replacing both structures is the only viable long-term solution for the region. The Army Corps has listened to our call in its final report, and we can now focus our efforts on the next phase of the project.”

The Corps’ decision to replace the bridges triggers two things, U.S. Rep. William Keating, D-Mass., said

It allows the state to move forward with its preliminary plans to overhaul the roads around the bridges and gives Keating, who lives in Bourne, leverage to get funding for new bridges in coming infrastructure bills.

Corps officials have said that funding the new bridges could be a challenge, as the current project estimate takes a large portion of the agency budget.

The Corps announcement that it wanted to replace the bridges was met with almost unanimous praise from Cape Codders, but many Bourne residents have concerns about where the bridges would be located and the possible need for land-takings.

The Corps has promised it will have more public meetings on the next phases.

Keating praised the Corps' decision to move forward with replacement.

“It really was the only approach to take,” he said.

Follow Ethan Genter on Twitter: @EthanGenterCCT.