BRATTLEBORO — Thousands of retaining walls, fashioned from steel, wood, fieldstone, and granite blocks - to name a few - line Brattleboro's roads. The walls hold earth, gardens, and roads in place.
The Brattleboro Department of Public Works recently received a state grant to repair a 150-foot dry-laid fieldstone wall on Washington Street.
The dry-laid stone wall supports Washington Street where it meets Canal Street. It failed more dramatically this season. The sidewalk has sloped and the roadway has cracked.
“It's not safe,” said Public Works Director Steve Barrett.
The DPW has kept the Washington Street retaining wall on its radar for about five years. The project remained unfunded in the town's capital projects budget.
“[Repairing the wall is] an expected unexpected expense,” said Barrett.
Luckily, the Vermont Agency of Transportation awarded the department a $164,700 grant last week. The funds will cover 90 percent of the repairs.
Barrett said the wall has shifted outward, creating a void between stone wall and earth. As dirt falls into the void, the roadway loses support and cracks. Water seeps through the cracked asphalt and into the empty space below, washing away more soil. As the void grows, the roadway and sidewalk above collapse.
On a positive note, a young tree that grew up next to the wall has kept the fieldstone structure from completely collapsing.
The Washington Street retaining wall poses challenges. The 15-foot-high wall sits below the roadway and along a parcel of property lower than the road. A private garage stands about a foot from the wall.
Sometimes the department will stabilize a retaining wall rather than replace the whole structure, Barrett said. In the case of Washington Street, the last time the town paved the road, it banked the asphalt slightly so water would flow away from the wall.
Barrett said the department considered another stabilization effort when the wall failed recently. The department asked Renaud Brothers, Inc., of Vernon to assess patching up the wall.
The company said the temporary fix would only save the town about half of a full replacement.
DPW will act as the general contractor during construction and will bid out specialty work. This approach saves money, Barrett said. The tradeoff is that the crew will have less time for its regular summer maintenance routine.
Workers will stabilize the existing wall before removing the sidewalk and asphalt. Then the crew will disassemble - “dissect” - the stone wall, saving the stones for other projects. Next a series of pre-cast concrete blocks, with a look similar to a block pattern, will fit into place. The roadway, sidewalk, and guardrail will then be replaced.
Barrett said that for the Washington Street retaining wall, dry-laid stones are not an appropriate material. Instead, he said, the town will reuse the stones for another retaining wall.
Which materials best suit a retaining wall depends on many factors such as layout, slope, how much weight the wall will bear, and wall height. Most stone walls aren't strong above five feet, Barrett said.
Towns like Brattleboro that formed along hillsides “are all walls,” said Barrett.
When people look around town, “[Retaining walls] are literally everywhere,” he said.
Whetstone Brook, which once fed a mill located on the site of what's now the Brattleboro Food Co-op, is lined by one long retaining wall.
Railroad companies constructed many of the town's early retaining walls in the late 1800s to early 1900s, Barrett said.
One railroad-built wall, nearly 70-feet tall, follows Vernon Street.
“It's actually a piece of art,” Barrett said.
One of the challenges with retaining walls, said Barrett, is determining ownership. Some sit on town land and some on private property.
“Usually somebody owns the wall until the wall fails,” Barrett said with a smile.
Often the town conducts surveys to determine on which side of a property line a wall sits.
Barrett said the Washington Street property owner is cooperating with DPW.
He hopes the town will allow DPW to close Washington Street so the crew can work faster and finish before the autumn.
Some of Brattleboro's retaining walls are more than 100 years old, said Barrett.
Originally built for roads that carried horses and carriages, the weight and vibrations from modern vehicles take a toll on older walls, he added.
Water, he said, poses more of a challenge than the freeze-thaw cycle of New England weather. As water flows through a wall, it can carry away or erode the materials in the structure. Modern walls are often constructed with drains, Barrett said.
Work on the Strand Avenue retaining walls is planned to wrap up this summer. The steep road has two retaining walls: one above the road holding back the hill and one below the road.
The upper retaining wall is fieldstone, and has started to collapse. Its replacement will consist of a concrete form made to resemble stone blocks.