Officials for Tri-State Dredging of Philadelphia and the state Department of Environmental Protection will begin a 60-day project to reinforce the dwindling dune line from Leeward to Nelson avenues. Several severe storms since last fall have eroded the beach off the streets and jeopardized oceanfront homes. The project will use Geotubes, massive textile sacks filled with sand, to bolster dunes to 10 feet in height. The same method has successfully protected dunes in Sea Isle City, Upper Township and Atlantic City, DEP officials said.