- Company: Bradshaw Construction Corporation
- Industry: Water/Wastewater
- Location: Leeds, Alabama
- Expected Completion Date: November 1, 2014
- Project Website
Bradshaw Construction Corporation completed a microtunnel drive crossing under an interstate and state highway in Birmingham, Alabama. The project consisted of 1,174 feet of 59 inch jacked steel casing for a 36 inch ductile iron water main. Ground cover under the highways ranged from 10 to 100 feet while shafts were an average of 22 feet deep. Mining conditions began with a mixed face of sticky clay and very soft shale all below the water table. The tunnel transitioned to a full face of sandstone with unconfined compressive strength (UCS) up to 19,470 psi. The biggest challenges of this project included microtunneling a long drive with small diameter casing through mixed-face and mixed-reach ground conditions.
What impact does this project have on America?
The waterline was installed by trenchless methods allowing six lanes of interstate highway and 4 lanes of local highway to remain open to traffic. The waterline served to provide water to a rapidly growing commercial and residential area.
What interesting obstacles or unusual circumstances did you overcome to complete the project?
The microtunnel was installed through mixed-face (rock and soft ground at the same time) and mixed-reach (full face of rock, full face of soft ground at different times) ground conditions. The tunnel was also of significant length providing challenges in guidance.
What dangers and risks did you encounter, and describe any extraordinary methods used to keep workers safe?
The tunneling shaft was located under powerlines requiring spotters, voltage detectors, and crane boom lock outs.