Channel Needs Emergency Dredging


Extreme silting and clogging in the channel beneath the Little Bridge in Oak Bluffs have prompted an emergency dredging project to protect the ecosystem in Sengekontacket Pond.

"It is very important for the life of the pond to flush," said county manager E. Winn Davis. "That is to say every time the tide changes it's brining in new nutrients and taking out nutrients."

The channel is now clogged with more than 5,000 cubic yards of sand, in part due to a winter and spring when the Island was pounded with repeated strong storms from the northeast.

This week the county announced it would begin an emergency dredging project.

While the problem was first noticed in the early fall, officials were not able to secure permits for the dredging until last Thursday. The pond began to fill in a little during the summer, and after the first fall storm plans were set for an early spring dredging. But when the bidding process began this winter, the county discovered its maintenance dredging permit, which is good for 10 years, had expired in 2003.

"Someone dropped the ball in terms of renewing the permit. I don't know who," said Bill Wilcox, water resources planner for the Martha's Vineyard Commission.


As steps were taken to secure emergency permits over the past several months, the Island was hit with one heavy storm after another, exacerbating the problem. Now biologists say the pond has become a health and safety hazard to marine and human life.

Oak Bluffs shellfish constable David Grunden said the problem has become so severe that it is not only threatening the shellfish that live in the pond, but is also preventing navigation and putting boaters at risk.

"That's what qualifies as an emergency," Mr. Grunden said. "It's obvious now there's a problem, but it wasn't so obvious in March."

The channel under the Little Bridge, which is now so filled that it allows only a trickle of water passage, provides for 40 per cent of the pond's water flow, Mr. Wilcox said. The pond was last dredged in December of 2002, when a large sandbar developed and the county dredged about 5,000 cubic yards of sand to reopen the waterway. According to Mr. Grunden this is the first time the pond has faced an emergency dredging.

"It's truly been a cooperative project between the town and county and the state in getting this done," Mr. Grunden said. "It's really been a good experience and everybody did respond and recognize that it was an emergency, though it was a trying time for a while."

Sengekontacket pond is not actually a pond, but is considered a coastal inlet because of the two waterways that enter the pond from the ocean. Because of the fragile state of these waterways, storms that blow from the northeast often push sand into the inlets, according to Brian Howes, a marine scientist at the University of Massachusetts at Dartmouth.

"You could say it's natural and you could leave it," Mr. Howes said. "But people are maintaining it in a more productive state both relative to the marine habitat and human use."

Mr. Howes, who has been sampling and studying Sengekontacket Pond through the Massachusetts Estuaries Program, said the pond is already in a state of decline. An influx of nutrients from groundwater and septic systems has caused a loss of shellfish and eelgrass, he said. Black, muddy sediment has been found where there was once sand. "Those are occurring now although the system has a very high quality of life for shellfish and animals," Mr. Howes said. "Then what happens when you start cutting off the exchange of nutrients without changing any of the nutrient input is that you see deterioration. If you reduce the flushing by 10 per cent it has the same impact as if you increased the input of nutrients by 10 per cent."

Mr. Howes said the choice is simple.

"If it's a minor scratch it heals quickly but if it's a broken leg it takes longer to heal," he said. "It usually does take time and the window to fix the problem is relatively small," he added.