Tisbury pushing new Five Corners plan

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As early as this fall, physical labor may be underway to significantly reduce the amount of flooding at Vineyard Haven’s Five Corners intersection.

A new plan outlined in front of town officials Wednesday would combine three outfall pipes at Beach Street Extension into one structure that engineers say would be more effective at keeping back rising seas. The plan also calls for adding an emergency outlet that would distribute more-extreme flooding waters away from Five Corners. 

The town’s select board voted to move forward with a plan from the University of New Hampshire.

Town administrator Jay Grande says that the installations will cost no more than $400,000 to complete.

The select board’s decision comes after a trio of winter storms caused substantial flooding at Five Corners, leading to damage inside surrounding businesses. Business owners and town officials in the last couple months have also expressed frustration with a lack of progress from the state Department of Transportation, which has been working to reduce flooding at the intersection.

On Wednesday, Jamie Houle, a research professor from the University of New Hampshire’s Stormwater Center, presented plans at a Tisbury select board meeting. The center has been working with Tisbury for several years, with funding from the federal Environmental Protection agency.

Houle, who called the intersection’s existing outfall system “dilapidated,” explained the planned improvements.

“What we’re proposing to do is intercept these three outfall pipes and combine them into one structure that would be maintainable … [as well as] providing a backflow preventer that would prevent water from coming from the Atlantic and pushing back on the existing drainage elevations coming down Beach Street Extension and Beach Road and everything uphill,” Houle said. He added that two years of monitoring Five Corners shows a 95 percent chance of flooding after more 1.3 inches of rain, or over 0.9 inches of rain within an hour.

This backflow preventer is a proprietary neoprene Tideflex fitting that would go over the outfall pipe. It allows water to push out of a pipe, but won’t allow sediment or seawater to be pushed through the pipe.

“We feel that we can greatly reduce the recovery time for these floodings,” Kirk Metell, director of Tisbury’s department of public works (DPW), said of the plan at Wednesday’s meeting.

The center’s plan, says Houle, addresses a key cause of flooding at Five Corners. Currently, the three outfall pipes at Beach Street Extension release water at the shoreline. But since these pipes are located where the tide rises, they frequently become obstructed. 

“What that means is that [the pipes] often get overburdened with sediment that reduces their hydraulic capacity, and this results in additional flooding,” Houle said.

He says that the emergency outlet would provide further support. “Instead of pushing everything to Five Corners, it flows toward the sea through this secondary emergency outlet,” Houle explained.

These outfall installations will be located underground, except for a two-foot reveal where the outfall system ends at the shoreline.

The current outfall system also requires vigilance and frequent maintenance. “Our current outfall pipe gets covered with harbor spoils at the changing of every tide. That requires the DPW to go down and remove those spoils before every rain event,” Metell said.

Grande said that he does not have a precise cost estimate for the project, but that he predicts a maximum cost of $400,000. He also said that the town can afford this. 

“We do have the funding in place to carry out the project, and to move the engineering and design forward,” he said at the meeting. Grande added that he understands that the joint transportation committee of the Martha’s Vineyard Commission will work to support the plan and pursue outside funding.

“We’re hoping, fingers crossed, if everything goes well, we can shoot for a fall build,” Metell said at the meeting.

“I don’t think we can afford to miss another season and go through what people have gone through in the last year,” Grande said.

The select board unanimously voted at the meeting to move forward with the center’s plan, and with the plan’s engineering and implementation.

The next steps for the plan, said Houle, are to develop a biddable outfall plan and confirm that the project will require no significant state permitting. An ownership agreement will also have to be reached with the Massachusetts Department of Transportation (MassDOT), stating which parties will conduct long-term operation, drainage and maintenance at Five Corners.

Metell added that the outfall plan will take place at the same time as a project to run new water lines on Beach Road Extension. This will involve digging up and repaving the road.

Houle did emphasize that the outfall plan will not eliminate all flooding at the intersection. “I’m not going to mince words here. There is no perfect situation,” he said. “If we were going to design this to current standards — we just don’t have the elevations here.”

Grande also stated at the meeting that MassDOT’s plans for Five Corners have not met town officials’ expectations. “We’ve waited four years for this other planning process to unfold,” said Grande of MassDOT’s efforts. “And I know that many in our committees were quite disappointed with the design that was put forward.”

Houle said that his work on Five Corners originally involved close collaboration with MassDOT, but that the state agency’s plans involved further work in the harbor, which would have involved a different approach than the center’s plan. He added that MassDOT does not plan to implement a solution at Five Corners this year, and that it might take seven years before they can do so.

“Certainly, they work in seven year increments, so that would be my best guess. If they decided today they were going to take this on, it would possibly occur in seven years,” Houle said.