MIDDLEBURY — An engineering firm within the next few weeks will recommend a “preferred” method of dealing with Middlebury’s two deteriorating downtown railroad overpasses, a project that will be selected from a list of six options ranging from doing nothing to replacing the spans with a concrete tunnel at a cost of around $17.4 million.
Representatives of Vanasse Hangen Brustlin Inc. (VHB) are working with the town of Middlebury on potential fixes for the railroad overpasses on Main Street and Merchants Row. The two aging spans are showing alarming signs of wear and tear and don’t provide the 23 feet of vertical clearance prescribed under the new national standard for double-stack rail cars. The two Middlebury overpasses currently provide 17 feet, 10 inches of vertical clearance. Mark Colgan, the VHB engineer who on Tuesday led a public meeting on possible bridge projects, said the town could argue for a reduction to 20 feet, 9 inches of clearance.
“The goal is to run double-stack cars from Rutland to Burlington,” Colgan said of future rail traffic influencing the project. “The current vertical clearance will not allow that.”
Colgan described various challenges for a project that is itself on a fast track, with construction tentatively slated to begin next spring. Those challenges, in no particular order, will include:
• Gradually deepening the rail bed in a manner that will produce at least another three to four feet of clearance beneath the overpasses. This has to be done gradually, Colgan explained, in order to not dramatically increase the grade of the tracks for trains. Officials anticipate realigning the track slightly in some locations, allowing it to achieve a speed-bearing capacity of up to 30 miles per hour, though Colgan does not anticipate trains will be going that fast.
• Dealing with drainage issues. Colgan presented photos at Tuesday’s meeting showing water pooling on the tracks at their current depth, never mind what might occur when the rail bed is excavated. This could set up the need for a pumping system to keep water off the tracks and discharge it safely somewhere else, though engineers will try to use gravity to their advantage. It should be noted that the track runs very close to the Otter Creek.
• Preserving, to the greatest extent possible, the historic stone retaining walls that border the bridges. The preferred project might require removing portions of the walls, which Colgan said could be re-purposed within the construction.
• Removing some of the dense stone and ledge that is suspected to be in the project area.
• Doing construction in a way that will provide minimal disruption to neighbors, local businesses, commuters and train traffic. Colgan acknowledged the work would at least temporarily remove some parking spaces in downtown Middlebury, as well as require the relocation of the Addison County Transit Resources bus stop on Merchants Row. He said the contractor will conduct work in a manner that will allow Vermont Rail to maintain its two daily train trips through Middlebury.
THE SIX OPTIONS
Colgan and his colleagues have spent the past few months analyzing the project area and using public feedback to prepare a list of options for dealing with the two bridges. He released the six options on Tuesday, along with their potential price tags, as well as their pros and cons:
1. Doing nothing. This option will be quickly eliminated because it does not satisfy local, state and federal requirements for the bridges.
2. Repairing the bridges, at a cost of around $2 million. VHB officials see no advantages to this scenario, which they don’t believe could meet state and federal standards.
3. Replacing the two spans with a concrete tunnel, providing a vertical clearance of 20 feet, 9 inches (requiring special permission), at a cost of around $14.6 million. The tunnel, Colgan said, would give the downtown some extra surface area by filling in the space between Triangle Park and the town green. The disadvantage is that it would not provide the full 23 feet of vertical clearance requested by federal authorities.
4. Replacing the two bridges with new spans, at a cost of around $13.1 million in a manner that would provide 20 feet, 9 inches of vertical clearance. This would accommodate double-stack rail cars, but not meet the 23-foot clearance threshold.
5. Replacing the bridges with a tunnel, at a cost of $17.4 million, which would meet the 23-foot vertical clearance mandate. But this is a project that Colgan said would require a water (drainage) pumping system and could require some modifications to the Elm Street railroad overpass located up the track.
6. Replacing both bridges in a manner that would allow 23 feet of vertical clearance, at a cost of approximately $15.9 million. This project, too, would require a pumping system and possibly some Elm Street overpass modifications, according to Colgan.
Whatever project is picked and approved will receive 100 percent state and federal funding.
It’s already becoming clear that the selected project — whether tunnel or new bridges — will involve a lot of concrete.
Colgan outlined a construction method that will involve dropping 6-foot-long, pre-fabricated concrete sections into the project corridor. If it’s a tunnel, they would be concrete boxes; if it’s a bridge, they would be U-shaped sections. Colgan said the concrete would be reinforced and 2 feet thick.
Tuesday’s meeting drew more than 60 people, many of whom weighed in on the project options through an electronic survey. Those results indicated majority support for a tunnel solution. Most respondents said they were especially concerned about how construction might temporarily impede access to downtown businesses.
Residents listened with interest to the VHB presentation and voiced some trepidations, including whether a tunnel might provide an hangout for drug users, whether the heavy construction work might damage nearby St. Stephen’s Episcopal Church, and whether the tunnel surface would be strong enough to withstand an earthquake and/or a permanent stop for the ACTR bus.
Colgan acknowledged the potential for a tunnel to provide cover for illegal activities, something the town would have to police. He said he was confident a tunnel would stand up to truck traffic, buses and Mother Nature.
He laid out a schedule calling for selection of a preferred project option by the end of this month, which will be the subject of another public meeting next month. If endorsed by town officials, the project would move on to design while the necessary permits are secured for work to begin next April.
Reporter John Flowers is at email@example.com.