This project consists of replacement of the following culverts under I-89:

These two existing drainage culverts pass under Interstate 89 between Exits 17 and 18.

View of original culvert

The project has been designed to minimize disruption to the traveling public. In order to continuously maintain traffic flow on I-89 during construction, trenchless technology was used to mine two tunnels through the roadway embankments. This relatively innovative technology allows the new culverts to be put in place without disrupting the highway. A precast concrete arch will be created for the new culvert. To create the tunnel under the highway so that this arch can be installed, the excavation was done by SEM method (selected to minimize disruption to I-89 traffic). 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”. Shotcrete refers to 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 arch can be rolled into place.

Temporary construction access roadways have been constructed connecting to I-89 northbound and southbound, allowing construction access to tunnel portals west of I-89 southbound and within the highway median. “Smart work zone” technologies are being used to help monitor traffic operations in the work zone and also to aid in rapid response to incidents in the work zone, should any occur.

Specific traffic restrictions on I-89 will be limited to temporary lane and/or shoulder closures. These travel restrictions will occur only at non-peak travel times. During peak travel hours I-89 will maintain two 12-foot travel lanes and two-foot shoulders.

The tunnel portal east of I-89 northbound will be accessed by a temporary roadway from Old Stage Road. Old Stage Road is a local, two-lane roadway maintained by the Town of Georgia. The southbound lane of Old Stage Road will be closed temporarily when the access road to the east side tunnel portal is first constructed and when it is later removed. Traffic will be maintained during those periods by alternating one-way traffic with flaggers.

Construction on this project began in the spring of 2017. Construction of the culverts was completed in January 2018. Final grading, landscaping and paving will be done in spring 2018. The project is expected to be complete by the end of May 2018. See Schedule and Calendar for more information.

BELOW: Culvert area before and during construction of tunnel for new culvert.