Effort to Open Pathway to Sea Hindered by Windy Weather, Surf and Tide
By JOSHUA SABATINI
Shellfish constable Paul Bagnall oversaw the opening of Oyster Pond and Edgartown Great Pond to the sea on Wednesday, but Thursday's unfavorable wind and surf conspired to close both openings.
Mr. Bagnall said he may try to make the cuts sometime in January if he is presented with a good opportunity; otherwise, he will wait until March. "Now I will take a good look at it," said Mr. Bagnall, "and keep an eye on the weather."
Mr. Bagnall said one factor in timing this project is the strength of the tides as the full moon approaches. With a high tide on the outside of the cut, the pond water will not have the desired outward flow.
Normally, Mr. Bagnall would have cut the opening around Thanksgiving time. But it was the weather again that influenced the timing of the project.
The past fall was one of the driest on record, said Mr. Bagnall. Without the rain, the pond level remained less than two feet above sea level. The ideal level of the pond for the time of the cut comes at around three feet above sea level. When the cut was made Wednesday, it was just two feet higher than the ocean.
Armed with a loader and an excavator, contractors worked from Wednesday morning into the afternoon, pushing and scooping sand until a channel connected sea and pond.
At 1 p.m., Terry Boyd was in the warmth of the excavator cabin, protected from the cold wind and rain mixed with the occasional snowflake. For more than an hour, he guided the five-toothed metal shovel time and again into the Edgartown Great Pond cut, casting the full scoops of sand off to the side. As he worked on the pond side, after opening the ocean mouth of the cut, one final scoop caused the pond water to burst through and mix with the sea water. The pond water pushed against the sea water, brushing against the sandy banks, frothing and forming whirlpools. The work seemed to have gone well. But 24 hours later, the opening to the ocean was sealed shut by sand.
William Wilcox of the Martha's Vineyard Commission has studied Edgartown Great Pond for years. Mr. Wilcox was involved in a dredging project that made last spring's cut through the barrier beach more effective. The project removed tons of sand from the channel leading to the spot where the cut is traditionally made. This created one of the most effective cuts in history: Edgartown Great Pond remained open to the ocean for 11 weeks. Over the years, cuts have remained open from seven days to about two months.
Mr. Wilcox said the tradition of opening Edgartown Great Pond extends back more than a century, and he said there are archived pictures of Islanders opening the beach using horses pulling shovels.
Mr. Wilcox said the opening is best done when the pond is filled enough to create a channel that will effectively run into the sea. If the pond level is not high enough, the channel is sluggish and the prime exchange does not occur. Another factor is the wind. If there is a northwest wind, then the pond water is blown out favorably. On Thursday, the wind began from the northwest, but then shifted to a southwesterly breeze that in part caused the closure.
The cut is an example of man's management of an ecosystem. Years ago, Islanders reaped the benefit of the cut when it invited the herring in. During fishing season, Island anglers take advantage of the cut to hook fish feeding on the herring.
The cut also favors the growth of shellfish in the pond. Mr. Wilcox said over the last 10 to 15 years the softshell clams in the pond had trouble with disease. Previously, the shellfish in the pond were thriving. The saltwater exchange brings to the pond a salinity that aids the growth of the clams. The oysters can survive at a lower salinity level for a while. Also, without the cut, there would be no herring run and ospreys would not be attracted to the area.
Mr. Bagnall said the salinity in the pond has been as high as 38 parts per 1,000 since the spring opening. Today the pond is at 15 parts. The salinity level can drop to around eight parts before it can seriously harm the reproduction of the clams. If Mr. Bagnall waits until March to make the cut, he said, the salinity would probably drop to around 10 parts, but he would like to prevent the level from dropping that low.
Mr. Wilcox said that effective cuts coupled with the dredging have the potential to create an environment for shellfish to thrive in Edgartown Great Pond.