Tonight the Harpswell Select Board will consider multiple change orders to the Mitchell Field pier demolition project which will add several thousand dollars in unforeseen costs to the contract.

Harpswell voters approved the demolition of the pier in March after years of debate on what to do with the derelict structure. A $3.2 million contract was awarded to Reed & Reed, a Woolwich-based contractor, to demolish the structure.

The change orders stem from the discovery of a previously forgotten drainage system that was installed by the Navy decades ago. A system of drains and manholes, previously buried out of sight, have begun to cause water issues that could pose problems for trucks hauling demolition debris.

“The site has been heavily reworked by the Navy, and we’re actually digging up things, some stuff that we thought had been removed, and some things we didn’t know were there,” said Barney Baker of Baker Design Consultants.

Mitchell Field was originally the site of a U.S. Navy fuel depot, closed in 1992 and then remediated. Fuel contamination in the soil, caused by the large storage tanks, was corrected by removing tons of material, treating it, and replacing it.

That remediation process left uncertainty about what the Navy left behind. When large amounts of water was discovered coming out of the ground, investigations by Reed & Reed revealed a forgotten manhole.

“It turns out the site had a pretty extensive drainage system in it,” said Baker. Parts of the system are functioning well, but pipe blockages further downhill have caused water to bubble up and saturate the soil.

That’s a problem for the demolition process, as the manhole just happens to be located near an access road for construction vehicles. Wednesday’s unseasonably warm weather highlighted the issues water would cause as the ground thawed out. “I think that we’re going to wind up getting trucks stuck,” said Bob Walton of Ray Labbe & Sons, which is also involved with the project.

The solution would be to determine whether pipes further downstream could be unblocked to allow the system to function normally once more.

The newly discovered manhole wasn’t the only drainage issue faced by the project. Another new road, also built for vehicle access, has been collecting water that could also pose problems come Spring. Old foundations and other issues are causing water to pool and saturate the road, something Walton said could be dangerous for workers. “Trucks could punch right through the road.”

Despite the unforeseen costs, the Mitchell Field project has already had cost cuts totaling $125,000. Even with the roughly $20,000 that could be added due to the drainage issues, the project is still under budget.

“The initial contract with Reed & Reed has been adjusted through a series of change orders reflecting changes in the way the work will be performed and additional work needed,” said Mark Eyerman, Harpswell Town Planner. “At this point if the board of selectmen approves the three change orders that were discussed last night the total contract amount will still be about $100,000 less than the original amount.”

The good news, said Baker, is that they’re unlikely to encounter any more problems. “Two weeks ago I wouldn’t have been able to answer it with quite the same confidence,” he said. “The contractor has finished this entire road, we’re not going to hit anything else.”

The Select Board meeting starts at 6:30 p.m. tonight at the Harpswell Town Office.