Cobb County, GA Installation of approximately 1,700 linear feet of gravity sewer ranging from 8-inch to 24-inch DIP, 600 linear feet of 84-inch tunnel via hand-mining methods, 310 linear feet of 48-inch jack-and-bore crossings, 14 standard precast and polymer manhole installations, and one 35-foot diameter shaft excavated to 40 vertical feet depth.
The project presented numerous complex challenges including open-cut work on active roadways and steep hillsides, varying ground conditions from dirt to rock, mixed face conditions for both jack-and-bore and tunnel operations, crossings under active walking trails and roadways, tunneling beneath a major interstate, and close coordination with adjacent hotels and major businesses to minimize operational impacts.
Originally designed for Tunnel Boring Machine (TBM) construction based on preliminary geotechnical information, the methodology was adapted to hand-mining after varying ground conditions were encountered during tunnel commencement. This adaptive approach successfully navigated the mixed face conditions while maintaining project schedule and safety standards, demonstrating flexibility and expertise in challenging underground construction environments.
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