Experts plot the course to restore Farm Pond in Oak Bluffs

The area shown in yellow illustrates the high water mark at Farm Pond in a 16-year storm event. The purple line shows the estimated increase in flooding if a larger culvert is installed. — Courtesy Department of Ecologica

Farm Pond in Oak Bluffs is one of a string of salt ponds that ring Martha’s Vineyard. The 33-acre water body, separated from Nantucket Sound by Sea View Avenue and refreshed through a narrow culvert that flows under the roadway, was once a rich source of shellfish. Lack of water flow and surrounding development, with associated nitrogen loading, have impacted water quality and led to a general degradation of the pond.

At a recent meeting in the office of Oak Bluffs town administrator Robert Whritenour, shellfish constable David Grunden, along with a group of experts in ecological restoration, brought town officials up to date on the campaign to bring Farm Pond back to health.

A brief history

Farm Pond, known to many as the pond where the sea serpent metal sculpture “Vanessa” mysteriously appears every summer, has been in decline for a long time. It’s been closed to shellfishing for 30 years. The eel grass, the pond’s canary in the cole mine, is dying off rapidly, according to a report from the Massachusetts Estuaries Project. The sulfurous smell and the fluorescent green algae become more noticeable each summer.

Longtime locals remember when 40-foot sailboats went through the channel between Farm Pond and Hart Haven harbor, then out to Nantucket Sound. They remember abundant populations of herring, alewife, crabs, and shellfish. They remember when Farm Pond was also called Oyster Pond.

But in the late 1970s the tide turned as development in the area increased and sediment built up in the channel, restricting the tidal flushing, a crucial component in the pond’s health. In 1984, a Nor’easter storm almost completely choked off the flow to Nantucket Sound. The lack of flushing, the growing number of inadequate septic systems, cesspools and storm runoff in the 463-acre watershed, and a growing non-migratory geese population made water quality so bad that Farm Pond was declared a disaster by the Oak Bluffs Conservation Committee in 1985.

A large culvert, big enough, locals remember, to paddle through in a canoe, was closed in 1992 to save the town maintenance costs, leaving only a 47-inch culvert to flush the pond. Ironically, the EPA stymied many efforts in the 90s to re-open the pond. In October 2009, after two years of wrangling permits, and with a big assist from The Friends of Farm Pond, the larger culvert was reopened, then a major storm blew through and it was clogged within a week.

Mr. Grunden has been working for the restoration of Farm Pond for over a decade, doing battle with increasing nitrogen and bacteria levels, and mountains of red tape from myriad government agencies. He has spearheaded fundraising efforts that have brought in more than $200,000 in grants from Massachusetts Environmental Trust, the Town of Oak Bluffs Community Preservation Act, and Restore America’s Estuaries-National Oceanic and Atmospheric Administration fund. To date, the town has invested very little money in Farm Pond’s recovery, according to Mr. Grunden.

The confab in Mr. Whritenour’s office was essentially ten years in the making. Construction of the new culvert, and the potential for increased flooding were the main topics of the meeting, which was also attended by engineers from Fuss & O’Neill, highway supervisor Richie Combra, conservation commission agent Liz Durkee and chairman of the selectmen Walter Vail.

New culvert construction

Recapping a presentation he made at the Oak Bluffs selectmen’s meeting on October 29, Mr. Grunden said years of research has determined the best fix is replacing the current culvert, which is four feet in diameter, with a larger culvert, that will allow water from Nantucket Sound to again flush the pond.

“Computer models have determined a culvert with a diameter of 16 feet gives the ideal tidal flow to flush the pond and restore and maintain water quality,” said Mr. Grunden. “With a larger culvert, we should be able to bring the pond well below the acceptable nitrogen threshold. Farm Pond will be in compliance with the U.S. Clean water act. It’ll be one of the few in the state to meet that criteria.”

“We’ve decided to do two double-barrel 8-foot culverts to provide flexibility,” said Franz Ingelfinger, ecologist with the Department of Ecological Restoration (DER), a division of state fish and game department, who’s been working with Mr. Grunden for the past three and a half years.

Mr. Grunden said the funding is in place to complete the design and permit process for the new culvert. The next big challenge is getting the funds to build it.

“We’re looking at at least $1 million, probably closer to $1.5 million in construction costs,” said Mr. Grunden. “But in the big scheme of things, it’s a cheap fix, especially when you start to look at other options, like sewering the area. And we should get results very quickly.”

Mr. Grunden and Mr. Ingelfinger are hopeful that Farm Pond will qualify for the needed construction funds under the National Fish and Wildlife Foundation’s Hurricane Sandy Coastal Resiliency Competitive Grant, which they will submit an application by the end of the month. The Hurricane Sandy Coastal Grants Program (HSCGP) will award more than $100 million in grants, from $100,000 to $5 million, throughout the region affected by Hurricane Sandy, to restore wetlands and beaches.

“The Sandy funding would definitely push us towards the more accelerated schedule,” said Mr. Ingelfinger. With HSCGP funds, he estimates culvert construction could be done in the fall of 2015 — although the fall of 2016 is probably more realistic.

Incremental flooding

A larger culvert brings the risk of increased flooding during a storm. Using computer modeled overlay on aerial photographs of Farm Pond, Mr. Ingelfinger showed that the new culvert would have minimal impact on potential flooding. “In a 16-year event, you’re looking at rise of only .4 feet.” he said.

A 16-year storm event is a storm that happens. on average, once every 16 years. Sandy was a 700-year storm, according to the Goddard Institute at NASA.

Mr. Ingelfinger also said that once the water breeches Sea View Avenue, as it did with Sandy, the size of the culvert is irrelevant. “Our models have shown it’s not the size of the culvert, it’s the duration of the storm that matters. With a Nor’easter that lasts for three days, it doesn’t matter if your culvert is thimble sized or the Grand Canyon. Once the water comes over Sea View Avenue, all bets are off.”

Tide gate

A tide gate to control the flow of water in and out of the pond was another option discussed. The gate would be installed on the Nantucket Sound side of the culvert and could close down the pond during storm surges, then open to drain the pond when the water recedes. A tide gate made of weir boards is the solution favored by the Massachusetts Department of Transportation. Engineers Nils Wiberg and Dean Audet from the firm Fuss & O’Neill presented several tide gate options — all had considerable drawbacks. A gate would require the town to spend additional money in operation and maintenance costs. It would be susceptible to damage and vandalism and it would be a visual eyesore, extending 10 feet above Sea View Avenue when not in use.

Mr. Whritenour, recalling his experience with weir board tide gates in Mashpee, was against the idea. “When you’re in a populated area, it’s a management nightmare. People are non-stop wanting you to raise the gate, lower the gate, it’s a mess. With weir boards, people disagree on how many and have even come in with chainsaws and cut them.”

“Enclosing the gate to protect it from elements and vandalism creates a bigger gate and more visual impact. It also adds to the cost.” said Fuss and O’Neill project manager Dean Audet.

Raising the roads

Another flood control option is simply raising the low lying areas on South Circuit Ave and Cannonicus Ave. to match the elevation of Sea View Ave., essentially building a dike that could confine a 16-year storm event. Sea View Ave. is only 4.3 feet above sea level — the lowest points on the boundary roads would need to be built up 18 inches.

Unlike a tide gate, raised roads would have no visual impact and would also require minimal maintenance. There are also other long term benefits. “We know the sea level is rising period,” said Mr. Whritenour. “Properties are prone to flooding. So this effort to raise the roads would protect them in the long run. Barring some enormous capital expense with raising the roads, this seems like a no brainer.”

In an email to the Times, Mr. Combra said “”I would only be guessing but I would guess [raising the roads] would cost upwards of $750,000 maybe more.” Mr. Combra also favored keeping the dirt section of South Circuit Ave. unpaved, to minimize expense and to reduce possible permitting complications.

“Either of these approaches, road or the gate, would have had no impact on the severity of the flooding that you experienced during Sandy,” Mr. Ingelfinger reiterated.

Noting the minimal increase in flood risk, Mr. Vail also suggested that they consider building the new culvert and not address the incremental flood change for the time being.

“I think chasing some of the capital money for the culvert construction is the best use of our time right now,” said Mr. Whritenour, who also offered to contact Congressman Keating and State Senator Wolfe, saying they could be especially helpful with the mercurial Mass DOT, who still have approvals to give.

There was also a consensus in the room that a consensus needs to be built with the local residents about the proposed remedies to restore Farm Pond.

“The quicker we move, the better,” Mr. Ingelfinger said.