VTrans describes Colchester Exit 17 rebuild; uses foamed glass aggregate behind bridge abutment

Vermont Agency of Transportation project staff briefed the group on the Colchester NH 028‑1 (Exit 17) reconstruction project, a multi‑season contract that includes new interstate on/off ramps and a new US‑Route 2 bridge over I‑89.

The contractor is using foamed glass aggregate (FGA), a lightweight engineered aggregate, in the backfill for a mechanically stabilized earth abutment at the new bridge. A highway division presenter said FGA is being used because it exerts less lateral pressure on soft, clayey soils beneath the abutment and helps maintain long‑term stability.

The project was planned as a three‑season construction contract covering work through 2025; the presenter described it as large and complex compared with typical single‑season VTrans contracts. Work includes ramp construction, a bridge replacement and geotechnical solutions for soft soils.

Why it matters: the use of lightweight backfill is a design choice intended to reduce settlement risk where soils are compressible; the project’s multi‑year schedule and new materials are intended to deliver durable infrastructure while managing subsurface constraints.

Project delivery and oversight The highway division noted that design teams handed construction plans to construction oversight staff once the prime contractor was awarded the contract; the district construction group will supervise work against the contract plans. The presenter said the project includes substantial geotechnical and materials oversight due to the soil conditions and innovative material use.

Ending: VTrans characterized the Colchester Exit 17 work as a long‑running, high‑complexity project with novel material choices intended to mitigate soft‑soil risks and produce a stable interchange and new bridge structure.