TOMS RIVER, N.J. — Slowed by lawsuits from beachfront property owners trying to block it, a plan to build protective sand dunes along New Jersey’s entire 127-mile coastline will begin soon in a part of the coast that was hardest-hit by Superstorm Sandy.

But it will be more than four years after the storm smashed northern Ocean County before the dunes will go up.

And some of the staunchest foes of the plan vow to keep fighting it.

Bob Martin, New Jersey’s environmental protection commissioner, said Thursday that his agency solicited bids for the work on Monday, adding the work should begin by spring.

The 14-mile project spans from Point Pleasant Beach to Island Beach State Park and includes the northern Ocean County coast that was pummeled by Sandy. Mantoloking, which was cut in half by the storm and saw virtually every one of its 521 buildings damaged or destroyed, and the Ortley Beach section of Toms River, which is still struggling to recover nearly four years later, are among the towns that will get protective dunes.

The state got voluntary easements from 350 property owners to let the project begin and is suing 149 others, mostly in Bay Head and Point Pleasant Beach.

Thom Ammirato, a spokesman for a group of Bay Head homeowners fighting the plan in court, said the dunes won’t be finished until after Gov. Chris Christie’s administration leaves office in 2018. He questioned the commitment of the federal government to keep paying to replace sand as beaches erode during the next 50 years.