Engineer: Mitchell Field pier in Harpswell 'could fail this afternoon'

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HARPSWELL — The pier at Mitchell Field has become so weather-worn that it could collapse at any time, a team of engineers told residents during a presentation at the town office on Tuesday morning.

The town is faced with a decision about how to address the problem. The only satisfying options come with hefty price tags ranging from more than $1 million to about $6 million.

“At this point, I don’t think there’s any of the pier that’s safe,” Wayne Duffett, a consulting engineer, said. “I mean, this could fail this afternoon.”

Duffett is part of an engineering team assembled by DeLuca-Hoffman Associates, a South Portland-based firm that has been assessing Mitchell Field infrastructure as it relates to a planned Marine Business District.

The pier is supported by 14-inch pipes filled with concrete; in some areas, the sea has eroded the metal and begun working on the concrete inside, leading to hourglass-shaped supports.

“I don’t think I have ever seen the pipe piles and the concrete fill in them wearing away,” Duffett said. “… I was kind of astonished.”

Ordinarily, an aging pier can be stabilized by punching new holes in the deck and installing pilings alongside the existing ones, but the level of decay is so advanced that Duffett said such a maneuver would be dangerous.

“If I were a contractor, I would have some reservation about causing vibrations,” he said. “It’s a narrow neck of unreinforced concrete. … It’s going to be hard to figure out how to approach the pier, because as soon as you touch it, it’s going to collapse.”

The concrete’s purpose is not to support weight, but to prevent corrosion in the pipe, Duffett said.

Three cells connected by bridges at the end of the pier are also in bad shape, he said. One of the cells, on the north side, collapsed on April 4, taking a connecting bridge along with it. The cells are supported by walls of sheet pile filled with 12-inch rocks. Like the pier pilings, the sheet pile has become extremely corroded.

“That sheet pile can pretty much be holed with a hammer anyplace you want,” Duffett said. ” … There’s obviously some places you don’t need the hammer.”

The cells are topped by concrete caps, which are in relatively good condition, but that’s small comfort.

“The thing underneath that concrete cap is going to continue to deteriorate and eventually split open and spill its guts,” Duffett said.

Costly resolutions

Rehabilitating the pier, if possible, would probably cost in the neighborhood of $1.7 million, Duffett estimated. Rebuilding the cells would be significantly more expensive, to the tune of an estimated $6 million.

The cost to demolish the pier and the cells would be in the neighborhood of $1 million to $2 million.

The cells could be dismantled by a barge with a crane on it, which could transport the rock and piling debris to land.

Either course of action would require the work to be done safely, and in compliance with the Department of Environmental Protection and the U.S. Army Corps of Engineers.

The DEP and Army Corps would likely require that care be taken to avoid dumping concrete into the water, which Duffett suggested could be difficult, given the fragile nature of the structures.

He didn’t recommend following a path towards reconstruction or a demolition.

“The best option right now is the do-nothing option,” Duffett said. “Fence that thing off.”

He said that a pair of small boat berths are currently safe for public use.

Many people present expressed concern that the pier has become a hangout for young people, despite the presence of fencing designed to discourage trespassers.

DeLuca-Hoffman Associates is expected to revise its recommendations and release a final draft of its report within the next week.

Matt Hongoltz-Hetling can be reached at 781-3661 ext. 123 or Follow him on Twitter: @hh_matt.

Edited on April 26 to add the fact that the north cell collapsed on April 4.