Crossing Solutions
Water mains, sewers, outfalls and culverts drilled in and pulled through in one length, under roads, rivers and whatever else is in the way. Up to 900mm, and often far cheaper than a deep open cut, a pipe jack or a tunnel.
A large pipe is where trenchless pays off most. The bigger and deeper the pipe, the more an open cut costs and the more ground it disturbs, and the alternative people usually reach for is a pipe jack or a tunnel, with deep shafts at each end. Directional drilling puts the same pipe in from a pit on each side, in one length, with nothing dug in between.
Most of our large-diameter work is water. Trunk and distribution mains under rivers and roads, sewers and rising mains, outfalls, and culverts. A pressure main does not mind a gentle curve in the bore, so it suits drilling well. A gravity sewer or outfall has to hold its fall the whole way, and we drill those to grade as well, the way we did the 900mm outfall at Hopton. The step-by-step for a drain is on our trenchless drainage page.
Plenty of large pipes that get priced as a pipe jack or a tunnel can be drilled instead. Drilling suits pressure mains, outfalls and drains to falls up to 900mm, and it usually costs a lot less because there are no deep shafts and no jacking pipe to buy. On the Hopton outfall, drilling instead of tunnelling saved the client about £1 million.
Jacking still earns its place. On bigger, man-entry sizes, and on long gravity sewers that need very tight line and level below the water table, pipe jacking or micro tunnelling is the right tool, and we will say so. Send us the job and we will tell you which side of the line it falls.
What we install
| Diameter | Up to 900mm |
|---|---|
| What goes in | Water and trunk mains, sewers and rising mains, outfalls, culverts and drainage |
| Pipe | HDPE / PE100, butt-fused on site into one string. Steel where the job needs it |
| Welding | Our own butt-fusion welders, with de-beading where a clear bore is needed |
| Rigs | Our own drilling fleet, with access to larger rigs when a crossing calls for one |
| Ground | Clay, sand, gravel and rock. The Hopton 900mm outfall went through strong rock |
We set the bore size, length and pipe for each crossing in the design.
How it goes in
Two things matter more on a big pipe than a small one. The first is the pull. For drilling, the wall thickness is often set by the force of pulling the pipe in rather than by the working pressure, so we check the pull for each crossing and pick the pipe to suit. The second is that a large empty pipe wants to float in the drilling fluid, which adds to the pull and loads the pipe against the top of the bore. We plan for both in the design, before anything goes on site.
Selected projects
A few examples of the water mains, outfalls and culverts we have drilled in.
900mm · drilled to falls through rock · reamed to 1175mm
A 900mm gravity outfall drilled to falls through strong rock on a curved bore, reamed out to 1175mm and pulled in as one string. Drilling it instead of tunnelling saved the client about £1 million.
Read the case study →710mm · 7 crossings · ~100-120m each
Seven river crossings of 710mm trunk main, welded into single strings on the bank and pulled through under the watercourse, delivered over about two months. We worked for Murphy as principal contractor, with Thames Water the client.
710mm & 630mm culverts · 6,000,000-litre lake
A collapsed culvert had dammed a valley into a lake holding six million litres of water. After a 180mm drain to drop the level, we installed 710mm and 630mm replacement culverts, draining the lake and taking away the flood risk.
252m · 355mm · under a tidal river
One of our longer drills. A 252m water main pulled in under the tidal River Parrett near Bridgwater, around 5m below the bed, to restore the supply to a grazing marsh.
Read the case study →Cost
Large-diameter pipe over a long distance is the top end of drilling work, and on the biggest jobs it can run into the hundreds of thousands. The comparison that matters is with the alternative. Against a deep open cut, a pipe jack or a tunnel, drilling is very often the cheaper way to put the same pipe in. What moves the price, and real budget ranges, are in our cost guide.
Questions answered
We install pipe up to 900mm by directional drilling, where the ground and the crossing suit it. Send us the pipe size, the length and the ground and we will tell you straight away whether it can be drilled.
Yes, and it is one of the most common large-diameter jobs we do. The main is butt-fused into one continuous string of PE pipe on site, then pulled back through the drilled bore in a single length, so there are no joints in the crossing itself. We have pulled trunk mains under rivers this way, including seven 710mm river crossings on the Angelinos trunk main for Thames Water.
It depends on the size and the job. Directional drilling suits pressure mains, outfalls and drains to falls up to 900mm, and it is usually much cheaper because there are no deep shafts and no jacking pipe. Pipe jacking or micro tunnelling earns its cost on bigger, man-entry sizes, and on long gravity sewers that need very tight line and level below the water table. We will tell you honestly which it is, and on our 900mm Hopton outfall drilling instead of tunnelling saved the client about £1 million.
It depends on the pipe size, the ground and the space to lay out the pipe string, so we set it for each crossing in the design. Our Pawlett Hams water main, at 252m under a tidal river, is one example of a longer drill, and we can go further where a job needs it. A long large-diameter pull also needs room on one side to weld up and lay out the whole pipe string before it goes in.
Mostly HDPE (PE100), which we weld into one string on site with our own butt-fusion welders. For drilling, the wall thickness is often set by the pull rather than the working pressure, so the pipe is commonly a thicker SDR than an open-cut lay would need, and a crack-resistant PE100-RC grade suits the rougher ride through a bore. We install steel where the job calls for it.
Related services
Gravity drains, outfalls and sewers drilled to falls, step by step.
View service →Where jacking is the right tool for a large pipe, and where drilling does it for less.
View service →What moves the price of a crossing, with real budget ranges.
View service →Send us the pipe size, the length, the route and anything you know about the ground. We'll tell you whether it can be drilled, how we'd do it, and give you a budget price.