PLUM ISLAND — Newbury officials were hoping the artificial dune built to protect Plum Island Center could withstand pounding surf and an astronomical high tide that was due to peak late last night, but emergency personnel were watching the situation closely.

The 500-foot-long dune, composed of five layers of giant sandbags sewn together, took a beating Sunday and yesterday from wind and waves.

"Until the storm passes, there's really nothing we can do," said police Chief Michael Reilly, who is also the town's Emergency Management director.

The sandbags were put in place in March to reinforce the severely eroded dune in front of the Beach Center parking lot to protect beachfront homes, Northern Boulevard, and the water and sewer systems from a breach by the ocean.

Sand and dune grass that had been covering the sandbags as recently as late Saturday afternoon were completely washed away, exposing the bags themselves yesterday morning.

The south end of the artificial dune next to the groin at Plum Island Center appeared to have shifted, leaving a gap between the top layer of sandbags and the natural escarpment face behind it.

The town's emergency command post trailer was deployed in the parking lot at the center. Reilly, Emergency Management deputy director Tim Leonard, conservation agent Doug Packer and building inspector Sam Joslin were all keeping a wary eye on the surf during morning's high tide.

Last night's high tide was expected around 11:30, Reilly said, and would be unusually high because of the new moon. According to a tide chart published by the Massachusetts Marine Trades Association, last night's tide would occur at 11:26 p.m. and would have a height of 10.1 feet.

Tides at 10 feet or higher are also predicted for tomorrow, Thursday and Friday. Normal high tides run from about 7.5 to 8.8 feet.

Newbury Selectman Geof Walker, who was also observing Plum Island Center yesterday, said he was particularly concerned that debris in the water, such as pieces of wood, could be propelled by the surf and tear the bags, which are made of coconut fiber.

Leonard said debris brought in by the tide has also been going out with it. He said if any pieces were left on the beach after last night's high tide that members of the town's Department of Public Works would remove them at low tide early this morning.

Meanwhile, the thousands of smaller sandbags that were filled by 300 volunteers last December for use in plugging a breach in the dune have been emptied and removed. The bags had been stored on pallets on Olga Way, near the sewer system substation over the winter. Leonard said the bags deteriorated over the winter and by spring were ripped and leaking.

"You could put your finger right through them," Leonard said.

In late May, he said, DPW workers slit the bags and removed them, leaving the large pile of sand that had been there before the bagging operation.