The U.S. Army Corps of Engineers has issued a revised flood-control plan to defend Suffolk’s southern coast from devastating storms by elevating homes, replenishing Fire Island dunes and restoring marshes.

The $1.2 billion Fire Island to Montauk Point, or FIMP, project spanning 83 miles was funded by Congress after superstorm Sandy but is now years behind schedule. The revised timeline calls for construction to start in 2018 and finish in 2025.

Retrofitting homes to withstand floods consumes more than half the $855 million construction budget. Planning, design and other costs account for an additional $237 million, according to the plan, which also has an ample contingency budget.

Two years ago, the Army Corps unveiled a similar strategy that cost $750 million, but that was “a very rough estimate,” Army Corps spokesman James D’Ambrosio said Thursday.

The new plan calls for elevating 2,424 houses in flood-prone areas. Of those, 1,429 homes are in the Great South Bay area; 631 near Moriches Bay and 364 by Shinnecock Bay.

In addition, 1,450 homes would receive flood-proofing assistance, such as relocating basement furnaces and utilities. Another 195 houses would be rebuilt, and flood barriers would be erected around 56 others, according to the plan.

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In Suffolk County, 1,632 homes have been elevated since Sandy, according to the Governor’s Office of Storm Recovery. The previous FIMP plan recommended raising 4,400 homes in flood plains.

D’Ambrosio said communities aided by the plan include Lindenhurst, West Babylon, Babylon, Bay Shore, Islip, East Islip, Sayville, Brookhaven and Mastic Beach.

Though no dunes can be built in the Fire Island National Seashore, the barrier island’s restored sand barricades will stand about 15 feet high and stretch along one-third of its length.

Col. David Caldwell, commander of the Army Corps’ New York District, spoke about the plan Saturday at the annual meeting of the Fire Island Association in Ocean Beach.

“There is a great sense of urgency,” he said, noting that the project balances “natural processes” such as shoreline sand movement with the need to protect recreation and coastal development.

Sen. Chuck Schumer (D-N.Y.), who had pressured the Army Corps to release the report, said: “Now, we must comb the details of this plan and make our voices heard. Long Islanders still have questions and deserve straight answers.”

Under the plan, 5.9 miles of roads in Amityville, Lindenhurst and Mastic Beach would be turned into dikes, shielding more than 1,000 homes from floodwaters.

As part of the plan, the Army Corps modified the breach-closing plan in the Fire Island National Seashore by giving decision-makers 60 days to decide to fill in gaps or let them close naturally.

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The FIMP project also includes dredging the Fire Island, Moriches and Shinnecock inlets. Tiana, downtown Montauk, Smith Point and Westhampton all would gain beach fill. Groins that worsen erosion would be shortened in Ocean Beach and Westhampton.

To absorb storm surges, salt marshes would be restored in areas including Tiana, Great Gunn and Corneille Estates on Fire Island, and west of Shinnecock Inlet.

As an interim project, the Army Corps finished repairing Montauk’s beaches and dunes this year. Though work also has begun on Fire Island’s $207 million dune restoration, the work will probably not be finished until 2018, according to the revised plan.

The plan calls for the federal government to pay 65 percent of the cost of replenishing dunes and beaches over a 30-year period, with the state on the hook for the remainder.

Issuing the revised draft report allows the Army Corps to begin the environmental impact statement process. Public hearings are planned for September.

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A spokeswoman for Suffolk County Executive Steve Bellone said the county already had submitted comments to the Army Corps and was reviewing the revised draft.