Highgate STP SCRP (12)

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.

Pipe Ramming in Progress
Pipe Ramming in Progress
Completed Slope with Headwall at Base
Completed Slope with Headwall at Base

Glen Dam Trash Rack Replacement Project

Glen Dam Trash Rack Replacement Project

Project Statistics

Location: Rutland Town, Vermont
Date Complete:
September 2017

Highlights

  • Three week project schedule
  • 80 cy lf cofferdam installed and removed
  • 14 foot deep excavation
  • 525 cy of sediment removed

About the Project

Casella Construction, Inc. (CCI) was contracted to perform the earthwork and support services as part of the trash rack replacement at the Glen Dam in Rutland Town, Vermont. The purpose of the project was to replace the trash racks and head-gate operator at the intake to the Glen Dam Penstock.

CCI began work by installing a coffer dam designed to support the excavation of 14 feet of sediment from the interior and exterior of the penstock intake structure. CCI utilized a clam shell on an 80-ton lattice boom crane to excavate the sediment from within the coffer dam and place it within an onsite stockpile to dewater. A mini excavator was lowered into the excavation to remove sediment from within the intake structure. CCI supported the general contractor with the removal of the existing trash racks, installation the head-gate operator, and placement of new trash racks.

In total, 80 lf of cofferdam was installed and removed and 525 cy of sediment was excavated and hauled off site for disposal. The project was completed within the three week schedule.

Intake Excavation
Intake Excavation
Cofferdam Excavation
Cofferdam Excavation