ACADIA NATIONAL PARK, Maine — Sometimes a retaining wall does more than just keep soil and rocks in place.
Along Duck Brook Road in Maine’s only national park, where part of a man-made embankment gave way last week, it also helps to support the road. The section of road where the collapse occurred, between the bridge that connects the road to Acadia’s carriage trail system and West Street Extension, has been closed indefinitely to motorized vehicles while park officials figure out how to proceed.
The collapse was not catastrophic — none of the paved portion of the road fell away — but part of what concerns park and Bar Harbor officials is what lies underneath the road. A water main that provides downtown Bar Harbor with fresh water, connecting the village with the town’s pump station on Duck Brook Road, runs along the road in the same embankment.
Keith Johnston, the park’s maintenance chief, said Wednesday that the main is “pretty old” but was not affected by the collapse, which involves a 10-by-20-foot section of the supporting embankment. But the park is proceeding slowly, he said, so it can consult with town officials to see what kind of repairs should be done and whether upgrades on the water main might be included.
“We have to take apart a large portion of the existing retaining wall [to fix it],” Johnston said.
Johnston said neither he nor Alan Farnsworth, head of Acadia’s road division, knows how old Duck Brook Road is, but he said it was not built to the same standards as other roads in the park. Repeated freezing and thawing of water in the embankment over a period of decades is the likely cause of the collapse, he said.
Fortunately, the section of road that is closed is not heavily traveled and is not essential for accessing area facilities. Duck Brook Bridge, the carriage trails around Witch Hole Pond, and the town’s pump station all can be accessed by car via the southern section of Duck Brook Road, which connects to Route 233 and remains open.
Park work crews have filled in the section of collapsed embankment with large rocks, Johnston said, and pedestrians and bicyclists are allowed on the closed section of road. Preliminary estimates suggest it would cost $52,000 to replace and strengthen the embankment where the collapse occurred, he added.
But the park does not have an emergency road repair account, according to the maintenance chief, and fixing the road is not a high priority. Acadia officials can seek funds for repairing the road from private or federal sources, he said, but they’re not likely to do so until they know specifically what kind of work the project entails.
“I think that’s something we could do in a year or so, depending on how things shake out,” he said.
In the meantime, the park plans to focus on other, higher-priority road and maintenance projects, according to Johnston. One of those involves constructing and improving Island Explorer bus stops at nine locations in the park on Mount Desert Island, which is being funded in part by a $1.3 million grant from the Federal Transit Administration. That project is expected to get under way later this week and to be completed by spring of 2013.
Follow BDN reporter Bill Trotter on Twitter at @billtrotter.