Frequently Asked Questions

The Vermont Agency of Transportation (VTrans) welcomes your questions and comments about the replacement of culverts on I-89 in South Burlington and Georgia. Here are some of the questions we have heard. We will continue to add to the list based on your input.

What is a culvert?

A culvert is a pipe or box structure that allows water to flow under a roadway or other obstruction in the landscape, such as railroad tracks . A culvert is used where surrounding areas are wet or intermittently wet or to allow the flow of a small stream or brook beneath the roadway. A culvert can also allow the passage of some wildlife. Culverts are very common in highway construction. There are about 46,000 culverts on state and interstate roads in Vermont!

Why do these culverts need to be replaced?

The replacement of these six culverts is planned for two reasons. First, the pipes are starting to deteriorate and need to be replaced as part of regular long-term maintenance of the highway. The State of Vermont proactively inspects culverts as part of its Asset Management Program. In addition, the size of these culverts is now insufficient to allow proper flow of water, causing water back-up. The replacement culverts will be larger to resolve this issue.

What are “smart work zone” technologies?

Smart work zone technologies use computers, sensors and various communications methods, such as variable message signs, to alert motorists in real time about traffic conditions in highway construction work zones. When informed, motorists can take alternate routes if necessary, driver frustration can be reduced and freeway congestion managed or eliminated. Smart work zones also enhance safety for both motorists and workers. Real-time information is especially helpful to motorists when there are traffic accidents, temporary closures, freezing conditions or any unexpected conditions on the freeway.

When will construction be happening?

Construction began on the Georgia project the fall of 2016 and continued through January 2018. Construction for the South Burlington project was
on-going from March through November 2017. Both projects will resume in spring 2018 and be completed by the end of May 2018.

Who is doing this project?

This is a Vermont Agency of Transportation (VTrans) project. To carry out design and construction, VTrans has selected the following team:

Why is the Georgia project using “trenchless tunneling technology”?

Unlike the South Burlington project, I-89 in the vicinity of the Georgia project is located on a relatively high embankment, meaning that the culverts are much deeper below the highway. In order to minimize highway and traffic disruption, a tunnel will be created and the replacement culverts will be slid into place in that tunnel.

What is SEM tunneling?

SEM means Sequential Excavation Method in which excavation is done mostly by hand and small equipment. The surrounding soil is stabilized by driving pieces of tubing and rebar into the soil. Then excavation takes place in small segments of 4 feet or so, followed by application of a layer of “shotcrete” (a process in which compressed air forces mortar or concrete through a hose and nozzle onto a surface at a high velocity to stabilize that surface). Once the shotcrete is sprayed, the excavation continues further into the bank beneath the highway. After the tunnel daylights on the other side the precast concrete arch can be rolled into place.