Drainage Conundrums Face Downtown Montauk Beach Stabilization Project
The plan to shore up downtown Montauk against storm tides has been beset by conflict from the beginning, but, with the Army Corps of Engineers work slated to begin this fall, the massive amount of stormwater runoff that makes its way down South Edison and South Edgemere streets and neighboring streets is becoming a sticky issue.
The Army Corps has asked East Hampton Town to address those drainage issues, as well as walkways over the dunes constructed of geotextile sandbags the Army Corps plans to install, in advance of work slated to begin in October.
The town’s consulting engineer, Steve Patak of Dvirka & Bartilucci, explained the issues his firm has encountered at the town’s work session at the Montauk Firehouse July 14.
Mr. Patak said that 33 acres of area drain to the end of South Edison Street, an area that would produce more than 100,000 cubic feet of water in the event of a 2 inch rainfall. In order to contain that water, he said, the town would need to install a football field-sized drainage field 5 to 6 feet deep.
He said the best the town could feasibly do to contain the water given the existing conditions in the neighborhood would be to contain .85 inches of rainfall, at a cost of $3 million.
He said the depth to groundwater in the area is part of the problem with installing drywells, which would need to be very shallow or would even be inappropriate in areas like these where you don’t dig very far before you encounter soil that is already saturated with groundwater.
“Drywells are like using a teacup when you need a bucket,” he said.
“Three million dollars will only handle less than an inch of rainfall. Where will the rest of it go?” asked Town Supervisor Larry Cantwell. “Even with this investment, we will still have an issue with some flooding. The benefit doesn’t seem to be high, and it’s costly.”
Mr. Patak said he is discussing with the Army Corps installing a floodgate into the engineered dune, which allow runoff to drain out to the ocean but would be put in place by workers during a major storm just before the storm tide began to rise. Such a floodgate hasn’t been incorporated into a geotextile tube design before, he said, though they are used in levee systems.
Councilman Peter Van Scoyoc pointed out that, in a hurricane, it’s quite possible that Montauk could see 6 to 8 inches of rain, as well as a storm surge, far worse conditions than could be engineered for.
“That’s not an unprecedented scenario,” he said.
Mr. Patak said both the Army Corps of Engineers and the state Department of Environmental Conservation are aware of the difficult engineering in the area, and are looking to find a solution, even if it’s not an ideal one.
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