Big Walnut Sanitary Trunk Sewer Extension Part 6, Phase 1

Completed in 2011 by Mole Constructors, the Big Walnut Sanitary Trunk Sewer Extension Part 6F1, Part 1 project involved the excavation of 15,000 linear feet of tunnel through shale for a sanitary sewer system. The tunneling work was performed using a 105-inch shielded Tunnel Boring Machine (TBM). Special ground modifications were required for the low-cover creek crossing to ensure stability and proper excavation.
In addition to the main tunnel, six shafts were excavated, with depths ranging from 40 to 180 vertical feet. Portions of these shafts were excavated using a Vertical Boring Machine (VBM) to reach the necessary depths. Due to the project’s classification as potentially gassy, enhanced safety protocols were implemented to mitigate any risks associated with underground gas exposure.
The tunnel was lined with 72-inch Reinforced Concrete Pipe (RCP), coated with WPVC T-lock material, which provided additional protection and durability for the sanitary sewer system. This lining ensured long-term performance and resistance to corrosion in a challenging underground environment.