Microtunneling Through the Unexpected in Tampa, Florida

The Florida Department of Transportation’s Downtown Tampa Interchange Improvements represent one of the largest transportation infrastructure investments in the state.

Approximately 2,773 lf of 62.5-in. outside diameter welded steel casing was installed using slurry microtunneling. The work was part of the drainage improvements associated with the I-4/I-275 interchange reconstruction. Work was beneath one of Tampa’s busiest transportation corridors.

Because the alignment crossed heavily developed urban infrastructure, conventional open-cut installation was not feasible. Surface traffic, existing utilities, environmental constraints, and limited workspace made trenchless construction the preferred solution.

Huxted Trenchless was selected to complete the installation through six separate microtunnel drives ranging from approximately 247 ft to 763 ft in length.

The project utilized sheet pile launch and reception shafts with reinforced concrete thrust blocks. An ISEKI Unclemole TCC1350 slurry microtunneling boring machine (MTBM) advanced the welded steel casing while maintaining continuous face support under groundwater conditions.

Although extensive planning, geotechnical investigations, and utility coordination were completed before construction, the project would ultimately become defined not by the expected ground conditions but by repeated encounters with unforeseen buried debris.

Planning for Success

Preconstruction planning focused heavily on reducing installation risks.

The project team established production rates were cut nearly in half, recognizing that every casing joint was required to be welded.

Launch shafts were designed to resist jacking forces approaching 400 to 600 tons, while bentonite lubrication systems were incorporated behind the MTBM and through lubrication ports installed within the casing to minimize skin friction.

---

Latest Posts