Description: This project included approximately 8,080 lineal feet of 6’ diameter sanitary sewer installed using tunneling methods in soft ground, sandstone, and mixed-face ground conditions; three large diameter shafts for the entry and exit of the tunnel boring machine as well as 6’ diameter shafts for personnel entry.
Construction of the sanitary sewer and shafts consisted of the following:
- Construction of a 54’ diameter x 100’ in depth steel rib and timber lagging shaft to be used as a wet well lift station.
- Design-built cement/bentonite jet grout columns for soil stabilization utilized during shaft installation process.
- Construction of a 38’ diameter x 80’ in depth steel rib and timber lagging mining shaft.
- Construction of a 34’ diameter x 80’ in depth steel rib and timber lagging exit shaft.
- 8,080 lineal feet of 96” steal rib and timber lagging in a mixed face sand/sandstone tunnel with numerous cobbles and boulders.
- Design-built soil stabilization/chemical grout (Sodium Silicate) program implemented in tunnel face to aid in boulder removal and maintenance of tunnel boring machine cutter head.
- 8,080 lineal feet of 72” Hobas pipe installed with pipe carrier/locomotive
- 8,080 lineal feet of annulus grouting with cement/bentonite grout.
- Drilled 6 – 120” CMP shafts lined for the installation of 6’ manholes to a depth of 100’.