Feasibility and route selection
The most valuable thing a trenchless engineer can tell you is that the crossing you have drawn should be somewhere else. It is also the cheapest thing, if you ask early enough.
The question we are answering
Not "can HDD do this?" — on paper it almost always can. The question is whether this profile, in this ground, at this length, with a pipe of this diameter and grade, can be installed at an acceptable risk of losing the bore. Those are different questions and only the second one has money attached.
What we look at
The geotechnical record
What the boreholes actually show along the profile, not at the abutments. Cobble and boulder content, the till-to-bedrock contact, running sand, organics, and artesian conditions. Where the investigation is thin, we say where another hole is worth drilling.
Length, depth and radius
Whether the alignment can hold a workable design radius at the depth the cover requires, and what that does to the entry and exit points on the ground you actually control.
What is on top
Rig-side and pipe-side working room, the pull-string layout, access for the spread, the watercourse setbacks, and whether there is anywhere to put a containment if returns come to surface.
What is already down there
Existing lines, abandoned lines, cables and structures — and, in a brownfield corridor, whether there is room to hold separation from every one of them along the whole path.
What the product will take
The pull-force envelope for the diameter, wall and grade, checked before the profile is fixed rather than after. A profile the pipe cannot survive is not a design.
What the regulator will allow
The crossing method the permit contemplates, the timing windows, the setbacks and the conditions. A technically sound crossing on the wrong side of a permit condition does not get built.
The honest outcomes
Straightforward
Drillable with a conventional spread and an ordinary fluid programme. We will tell you this even when it ends the engagement, because you do not need us for it.
Difficult, and here is why
Drillable, but with named risks that need to be engineered and priced: a marginal formation, a pull-force margin that is tighter than it looks, a shallow section where the pressure envelope closes up. This is where the design work is.
Move it
The ground will not hold the bore, or the profile cannot be flown at an acceptable risk. We say where to move it to and what that costs, and we would rather say it in week two than in month five.
Where a whole alignment is in question rather than a single crossing — that is, whether the line can be built trenchless end to end — see trenchless mainline. It is a different assessment, and it is the one we do best.
What you get
- A written feasibility opinion on the named crossing, with the assumptions and the limitations visible.
- A preliminary profile with entry and exit, design radius, depth of cover and hole size.
- The pull-force check, with the governing case identified.
- A risk register for the crossing, ranked, with what would retire each risk.
- Where relevant, the alternative alignments and what they would cost you.