Published in the Newburyport Daily NewsReport: PI losing 13 feet per yearBy Victor Tine February 06, 2009 12:15 am PLUM ISLAND — Without remedial action, more than two dozen beachfront homes near Plum Island Center will be washed away by 2019, according to a preliminary assessment by the Army Corps of Engineers.
An Initial Appraisal Report, issued last month by the Army Corps but not distributed to the public, indicates that the central section of Plum Island has been losing an average of 13.3 feet of shoreline annually between 2000 and 2007.
"If protective measures are not implemented, it is anticipated that long-term erosion will continue at the current rate and eventually threaten the shorefront structures along Northern Boulevard and the sewer and water system under the road," the report says.
The study looks only at the half-mile stretch of beach extending northward from the Beach Center, where the worst of the erosion has been occurring. In somewhat muted terms, it estimates that 26 beachfront buildings to the north of the Center will "experience storm damage" in the next decade. But an overlay map included in the document gives those words starker meaning — it shows that in 2019 the dunes where those homes sit are entirely gone, and large sections of Northern Boulevard are wiped out as well. The homes along the west side of Northern Boulevard will be sitting on the edge of the dune, overlooking the beach.
The report was issued as part of an Army Corps study to determine whether it is financially feasible to take sand that will be dredged from the Merrimack River channel and deposit it directly onto the island beach.
An estimated 160,000 cubic yards of material is expected to be dredged from the channel, according to the report, enough to widen the beach by 60 feet along a 2,500-foot-long stretch of shoreline from the Center northward to 29th Street.
The report also estimated where the dune line would be if the beach is replenished and the rate of erosion remains at 13.3 feet per year. In that case, by 2019 the dune will have eroded to within about 2 to 20 yards of Northern Boulevard, with the worst erosion occurring closest to the Center. The first dozen or so beachfront homes north the Center will be entirely lost, and the rest will be literally on the edge of the dune.
The Army Corps' standard operating procedure is to dump dredged material off shore or near shore, the least expensive method of disposal. The corps is currently studying whether the benefits of on shore deposit outweigh the extra costs that would be incurred.
The report indicates there is enough evidence of benefit that the corps should pursue a more detailed study of the situation.
An estimate in the report of the dredging and near-shore deposit is $1.96 million.
Cost calculations for dredging and two different methods of on-shore deposit are also included. Using a barge-mounted apparatus to pump out the dredging vessel and place it on the beach would cost about $4.95 million. The price tag for pumping sand directly from the dredge to the shore would be about $3.7 million.
So on-shore placement would cost between $1.75 million and $2.99 million more than the traditional near-shore method.
But the report also estimates that the replacement value of 26 buildings between the Center and 29th Street would be $7.71 million. That amount does not include the cost of replacing the newly installed sewer and water infrastructure, nor does it estimate other erosion-associated costs, such as emergency evacuations.
The report also recommends that if the state, Newburyport, Newbury and Salisbury agree, a more comprehensive study of the Merrimack River and the region around the mouth of the river should be studied "to determine if a wider range and longer-term solution exists to address the beach erosion and storm protection needs" of the area. It suggests the study could also include communities farther south in Ipswich Bay.
The Army Corps official who has been working on the Plum Island beach erosion problem for the past year, Navigation Section Chief Edward O'Donnell, could not be reached for comment yesterday.
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