BRATTLEBORO—Two tree trunks support part of the 200-foot-long Green Street retaining wall, and the road above has cracked wide enough for Director of Public Works Steve Barrett to fit his boot in it.
At its March 17 meeting, Barrett described to the Selectboard the urgent need to fix it before it collapses.
The town had included funds in the fiscal year 2015 budget for an engineering evaluation, said Barrett, and the board approved the infrastructure repairs for the wall.
“The tallest middle section of the stone wall is leaning out by several feet and continues to move,” wrote Barrett in a memo. “It is, in our opinion, close to failure.”
Or, to quote the engineers at Stevens & Associates, “Material friction is preventing collapse.”
So, in other words, force of habit is holding the stones together.
Wall begins to move faster
Staff have monitored and measured movement in the wall for more than 20 years, said Barrett, who noted that the wall’s shifting and outward lean “accelerated” last year.
Green Street cuts diagonally from Western Avenue, passes Green Street School, skirts Church Street, and becomes one-way. It then snakes above the Harmony Parking Lot, dropping quickly between the Brattleboro Shrine Club’s concrete wall and the Midtown Mall building, where it ends at High Street.
The DPW closed the one-way portion of Green Street, known as Green Street Extension, last September because the retaining wall had started to lean.
Barrett recommended replacing the almost 200-year-old dry-laid stone wall with a concrete process called Redi-Rock.
The DPW used Redi-Rock to repair the Washington Street retaining wall in 2013.
In addition to the infrastructure repairs, the board approved a plan to apply for two grants: a $57,000 Structures Grant through the Agency of Transportation and a $300,000 Urgent Needs Grant through the Community Development Block Grant program.
If approved, the grants would provide $457,000.
“Almost 200 years” is a rough estimate of the wall’s age. Town maps from 1854 show Green Street in use. Below the stone wall with its concerning voids and precarious outward lean, the ground slopes to a flat concrete wall, brightly adorned with a mural.
This concrete wall, said Barrett, is the former foundation for a structure built sometime around the 1940s, located in the Harmony Lot.
Barrett said the former building foundation acts as a second retaining wall. So far, the old foundation is stable as long as the upper wall stays in place.
The wall’s lean, called a batter, should be around 1:12, meaning a 1-inch setback or slant back toward the road for every 12 inches in height, said Barrett.
Instead, age and gravity has taken its toll. The wall has developed a “negative batter,” leaning outwards toward Harmony Lot by more than 2 feet.
In addition to closing Green Street Extension, the DPW removed trees so they wouldn’t fall into the Harmony Lot.
DPW also installed a valve on the eight-inch Lower Green Street water main, so that if the wall collapses, it won’t release a waterfall under 150 pounds of pressure per square inch.
Options for repair — or abandonment
The engineering firm Stevens & Associates investigated the wall and provided the town with a report outlining potential routes for repair or abandonment.
The six alternatives, said Barrett, ranged in price from $774,000 to replace the wall with a new dry-laid stone wall to $183,000 to abandon the road.
Barrett said his department recommended replacing the wall for $550,000 with a prefabricated retaining wall manufactured by Redi-Rock, a company in Michigan.
Redi-Rock creates precast concrete blocks with the geotextile fabric behind the concrete to provide additional stabilization.
The Redi-Rock wall will have an average lifespan of 75 to 100 years, Barrett said.
Bidding should be competitive because many contractors in the area have worked with Redi-Rock, he continued. Within a one-hour drive of Brattleboro, 14 projects have used the product, he said.
Contractors can paint the concrete “stones” to mimic natural stone, he said.
Choosing how to repair the wall was hard for Barrett.
A dry-laid stone wall, he admitted, would be his preferred option. Stone walls, when done well and correctly, can last 1,000 years, he said.
But good stone walls done well are expensive, he added.
Abandoning Greet Street Extension at an initial estimate of $183,000 looked attractive at first, he said. This scenario would have included removing the road and wall, sloping the ground to the Harmony Lot, and creating a turn-around.
When the DPW staff investigated the option, however, the dollar signs accumulated.
The initial cost estimate did not meet the town’s standards for creating a public turn-around space rather than dead-ending the road. Obtaining rights-of-way and other legal expenses would also have tacked on costs. Changes to the water main would also have been required.
Closing the road hampered snow removal this winter, said Barrett. It also dumped more traffic onto nearby Retting Place, which was not built to handle heavy trucks.
Barrett also worried that closing the street might restrict future commerce in the area. The Midtown Mall, on 22 High St., is home to the Backside Cafe and Brattleboro School of Dance, and the building has a loading dock on Green Street Extension.
Selectboard member David Schoales said that Brattleboro had enough financial pressures.
“We can get along without it,” he said. “Let’s let this one go.”
Town Manager Peter Elwell said he felt the same way — at first.
However, in a broader context, Elwell said abandoning the road wouldn’t help the town’s bottom line.
State aid, he said, is calculated based on the number of miles of roads the town has and whether the roads conform to state standards. The option could cost the town grant monies for other infrastructure projects, Elwell warned.
Selectboard Chair David Gartenstein wanted to keep Green Street Extension.
Downtown’s roads are “very interdependent,” said Gartenstein, who endorsed the Redi-Rock recommendation. Green Street is a through road, he noted.
All told, Elwell wrote in a March 19 memo that repairing the failing wall will cost an estimated $585,000.
The board has authorized $30,000 to retain Stevens & Associates’ engineering services.
Additional municipal matching funds required by the grants will total $92,500, with in-kind matching at $5,000.