Highgate STP SCRP (12)
Project Statistics
Location: Highgate Center, Vermont
Date Completed: August 2017
Highlights
- The project was delivered ahead of schedule and under budget
- Used pipe ramming, a trenchless technology, to complete the project
- Replaced culvert without disturbing traffic on Route 78
Challenging Site Conditions
- Steep 30% grade access roads
- Inability to close Route 78
- Limited construction easements
About the Project
Casella Construction, Inc was contracted by the Vermont Agency of Transportation (VTRANS) to replace a 4’x4’ concrete box culvert under Route 78 in Highgate, Vermont with a 131 lf, 6’ diameter 3/4” spirally welded pipe with precast concrete headwalls. CCI utilized trenchless technologies, pipe ramming, to install a new 6’ diameter steel pipe located 30 feet under the road bed.
The site posed numerous challenges, one of which was access. Limited construction easements, steep 30% grade access roads and the inability to close Route 78 required CCI to develop a lifting plan that revolved around two tracked excavators, lifting beams, snatch blocks, and a series of setting pads to move the 30,000 lb concrete headwalls into position.
The new headwalls required deep excavation and unsuitable soil replacement in the already unstable slope below the roadway. CCI used a combination of driven sheet piles, horizontal directional drilling, steel walers, and steel tie rods to brace the excavation. Utilizing the opposing soil forces, directional drills were completed from the east embankment to the west embankment under the roadbed and threaded rods were pulled back. The rods were then needled through the sheeting and fastened to walers. This allowed CCI to excavate for the headwalls safely and limited any settlement of the active roadway above.
