Shoreline moves in on Plum Islanders

At least 34 houses are threatened by accelerated erosion, with as many as eight in imminent danger. The erosion is caused in part by recent storms and high northeast winds, but residents and some town and state officials say a deteriorating jetty might also be to blame.

In the past two weeks, as two strong storms passed through the area, as much as 25 feet of dune has been lost in front of several houses along Southern Boulevard, where waves are crashing just feet from residences.

“Trying to stop the Atlantic Ocean is a challenge,’’ said Eric Woorall, deputy regional director of the Department of Environmental Protection.

Some residents have stockpiled sand next to their beachfront properties for emergency replenishment. Along the start of Northern Boulevard, about 500 feet of car-size sandbags, put in place 16 months ago to fight expected erosion in the winter of 2008-09, rest perilously atop a thinning dune that yesterday was repeatedly pummeled by 10-foot-high waves. On the other side of that dune are five houses.

“We had 95 feet of dune in front of us when we bought the house three years ago, and now we have only about 20 feet,’’ said Donita Rardin. “Most of it was taken during the storm on Patriots Day in 2007, as we were purchasing the house. The erosion here has been really unexpected and exceptional,’’ said Rardin, who recently took down fencing in front of her house because of the erosion.

The emergency stockpiles of sand are the last option until a major project due to start this fall. The US Army Corps of Engineers plans to dredge the Merrimack River and transfer the sand to the eroded areas.

The dredging would deposit roughly 160,000 cubic yards of sand from the river, at a cost of approximately $3 million. About 120,000 cubic yards will go to rebuild dunes on Plum Island Beach, which extends south of the river channel, and about 40,000 cubic yards will be deposited on Salisbury Beach, just north of it. After the sand is placed, grass will be planted next fall to protect the area from erosion.

The funding will come from the US Army Corps of Engineers and the state Department of Conservation and Recreation. The bidding will start March 15, and the project is expected to start Sept. 1 and last about two months, said Tim Dugan, spokesman for the corps of engineers. A report by the corps released in January 2009 estimates that 13.3 feet of beach on Plum Island is vanishing each year.

Woorall said the beach renourishment, adding sand and then planting grass, can help stave off the erosion for years, but it will not last. “There needs to be a comprehensive focus on what is causing this.’’

Bob Connors, director of the Plum Island Foundation, a nonprofit made up of residents who oversee coastal issues on the island, said a jetty extending 3,000 feet from the mouth of the Merrimack River to the ocean has compromised the shoreline, casting sand from the river far out to sea. “We’re talking about up to 150,000 cubic yards of sand that the jetty pushes out. If no jetty were there, the sediment settles at the mouth of the river and works up the coast.’’