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Trenchmark Underground Co.Trenchless Contractor
Bundled conduit curving out of red clay at the edge of an open bore pit.

Capabilities › MTBM

Microtunneling

Remote-operated tunnelling for deep, wet and unforgiving ground.

How it works

The short version

A closed-face machine is driven from a shaft with nobody in the tunnel, balancing the ground pressure at the face as it goes. It is the method for a deep interceptor below the water table, or for ground that would run into an open bore and take the street above with it.

Where it fits

  • Deep gravity interceptors and outfalls
  • Crossings below the water table
  • Ground too loose or wet for an open bore
  • Long runs where a shaft is cheaper than a street

What you get from us

  • Shaft design, dewatering and settlement monitoring
  • Face pressure and steering logged for the whole drive
  • Settlement survey before, during and after
  • Full as-built alignment on completion
Our range for MTBM
Finished diameter30 – 96 in
Maximum drive length1,000 ft between shafts
Working depthTo 65 ft below grade
Ground conditionsBelow water table, mixed face
GuidanceLaser with active steering

On the edge of that range?

Those are the numbers we will put our name to on a bid. If your crossing is longer, deeper or wider than what is listed, say so - sometimes the answer is a different method, and sometimes it is a straight no. Both are more useful than a number we cannot hit.

Ask about your crossing

References

MTBM jobs we have finished

Owner, diameter and length - the detail an engineer actually checks.

  • Microtunneling at Coastal interceptor below the water table, Charleston County, SC

    Coastal interceptor below the water table

    Owner
    Regional sewer district
    Location
    Charleston County, SC
    Size
    54 in RCP
    Length
    820 ft between shafts

    A closed-face drive through saturated sand 44 ft down, with settlement monitored on the surface the whole way and no measurable movement at the street.

The other three methods

  • Horizontal Directional DrillingHDD

    Steerable bores that go under the obstacle and come back up on the far side.

    • Maximum pipe diameter: 36 in
    • Maximum single shot: 2,200 ft

  • Auger BoringAuger

    Jacked steel casing on grade, the standard for rail and highway crossings.

    • Casing diameter: 12 – 72 in
    • Maximum single drive: 600 ft

  • Pilot Tube Guided BorePilot tube

    Line-and-grade accuracy for small gravity sewer in tight quarters.

    • Product pipe diameter: 8 – 30 in
    • Maximum drive length: 400 ft