Choosing a method
The method is usually chosen by whoever is available to do the work, which means it is chosen by what they own. It should be chosen by the ground and the profile.
| Method | Where it fits | Where it does not |
|---|---|---|
| Horizontal directional drilling | Long crossings, large diameters, deep arcs, thousands of feet under an obstacle. Steerable, surveyed, works in most ground with the right assembly. | Short runs, where mobilisation swamps the job; primary soils of cobble and boulder; anywhere the surface cannot take the spread. |
| Horizontal bore | Smaller scope, shallow arc, modest radius, a road or a short obstacle. Faster and much cheaper to mobilise. | Long reaches, deep profiles, large diameters, or anywhere real steering accuracy is needed. |
| Compaction reaming | Mainline installation in displaceable ground, segment after segment, shallow and conforming to grade. The economic trenchless method over distance. | Cobble or gravel as the primary soil — nothing to displace; rock; and deep arcs, which are not what it is for. |
| Pipe ramming | Steel casing through adverse soil in any direction, including where a bore will not hold. Tolerant of obstructions that stop other methods. | Long lengths; anywhere accurate steering matters — it goes where it is pointed. |
| Open cut | Short deflections, tie-in points, and ground where trenching is genuinely cheaper and the surface impact is acceptable. | Watercourses, sensitive and high-value ground, congested corridors, and anywhere reinstatement is the dominant cost. |
The selection logic
Read the ground first
The geotechnical record along the profile, not at the abutments. Displaceable soils, competent rock and cobble-dominated ground lead to three different answers and there is no judgement call in it.
Then the profile
Depth driven by the feature, length driven by the crossing, radius driven by the pipe. If the geometry does not close, the method changes or the alignment does.
Then the pipe
Check the installation load against the product's allowable. A method that installs the pipe by destroying it is not a method.
Then the surface
Working room, access, containment, permit conditions and timing windows. This is where technically sound answers get eliminated.
Then, last, the market
What can actually be resourced in your region, in your window, at a price. Real, but it belongs at the end — not, as usually happens, at the beginning.
We are a trenchless practice and we will still tell you to trench it when trenching is right. A short deflection across a farmed field with a willing landowner does not need a drill rig. Reflexive trenchless is the same error as reflexive open cut, just more expensive.