MANTOLOKING, N.J. - Work on a $40 million, four-mile-long steel seawall that will extend through this Ocean County town and into the beachfront areas of neighboring Brick Township trounced by Hurricane Sandy could begin early next year, officials said.

Unlike seawalls in some beach towns that stand as tall stone or brick edifices, this massive structure will be driven 32 feet below sea level and will rise 16 feet above ground. It will be virtually unseen, buried beneath sand dunes that will complete the project.

"The most important thing is: Is it going to protect us?" asked Doug Popaca, a spokesman for the Borough of Mantoloking's Office of Emergency Management.

Popaca, a resident of this Shore community where each of the 521 houses in town was damaged or destroyed by Sandy, saw the devastation firsthand. But he was one of the lucky ones: after making repairs to his house, he and his wife were able to move back in in March. The storm washed out to sea about 60 houses in Mantoloking, and 140 were so damaged they had to be torn down.

"Our dunes are still in pitiful shape, and our beaches need renourishment," Popaca said. "This seawall will serve as our best defense until the dunes and the beaches can be put back in order and then be something that can protect us against any future storms like Sandy."

Popaca said the project would be 80 percent paid for with money from the federal Highway Administration and 20 percent from the state. The state Department of Environmental Protection will oversee the construction process, and bidding to find a contractor will begin this month. Construction could begin in January or February and be completed by early summer, officials said. The only cost borne by the municipalities will be to ensure the wall stays covered with sand.

Contractors for the state Department of Transportation began removing vertical steel slats last week from a temporary seawall constructed two weeks after Sandy to shore up the beach where Route 35 runs parallel. Some of the temporary structure ran through private property. The road was heavily damaged when the storm's ravaging tides came ashore and literally cut in half the barrier island on which Mantoloking sits, carving a new inlet between the Atlantic Ocean and Barnegat Bay.

The temporary wall is being dismantled at the request of beachfront property owners who want access to their land so they can begin rebuilding. An underground portion of that barrier will remain to help stabilize the beach until the permanent wall and dunes can be built, officials said.

"I'm just happy to see progress being made," said Marjorie Ingles, whose family has owned property in Mantoloking since the early 1900s. Their family home was among those Sandy washed away. "What happened here was a really terrible thing . . . devastating for so many," Ingles said.

Though some of her neighbors have expressed concern about whether the new seawall would protect the town from the kind of catastrophic damage Sandy wrought, Ingles said she was still undecided.

"Some people say that the seawall could actually cause more damage, scour out the beach over time. I'm not a scientist, so I don't know. I just know that we need something done for this beach," said Ingles, 86, who is temporarily living with her daughter in Toms River, but who returns almost daily to walk the narrow strand.

Many experts contend that done right, a seawall like the one to be built here is an effective tool against flooding and storm damage, said Jon K. Miller, a research professor in the Coastal Engineering Laboratory at the Stevens Institute of Technology in Hoboken.

Miller said seawalls work similarly to bulkheads and should be considered a last line of defense against rising tides, standing behind well-nourished beaches and dune systems like the one planned to work in conjunction with the project. Seawalls break wave action, helping prevent the storm surges that cause massive flooding and property damage.

Seawalls like the one built in Galveston, Texas, immediately after the Galveston Hurricane of 1900 are considered among the great coastal engineering feats of the 20th century. The 10-mile-long wall - along with measures to raise part of the town and keep a beachfront fattened with plenty of sand to buffer wave action - has been credited with saving the city from widespread damage in the ensuing decades, Miller said.

Similarly, Bay Head, which neighbors Mantoloking to the north, suffered some serious flooding and damage during Sandy, but fared much better than Mantoloking. Some have credited the town's packed boulder seawall built in 1882 and hidden by sand dunes until the Oct. 29, 2012, hurricane denuded the beachfront.

The National Science Foundation, which conducted a study of the Bay Head seawall's impact during the massive storm, concluded it had made a difference. In Mantoloking, the entire dune system "nearly vanished" and "water washed over a barrier split and opened three breaches . . . where the land was swept away," the report noted. But in Bay Head, the only portion of the dune that eroded was where a "section of the dune behind the seawall received only minor local scouring."

"It's amazing that a seawall built 150 years ago then naturally hidden under beach sands and forgotten would have a major effect under the conditions in which it was originally designed to perform," wrote H. Richard Lane, program director at the National Science Foundation's Division of Earth Sciences.