Est. 2005 · UK-wide trenchless installations07920 553 578·enquiries@swdirectionaldrilling.co.uk
Crossing Solutions
A crossing under a motorway or trunk road is a geotechnical certification job as much as a drilling one. We design the crossing to National Highways CD 622 and see the certification through, so the drill can start on time.
When a pipe, duct or cable is installed by a trenchless method under a motorway or trunk road, National Highways require the crossing to be certified to CD 622, Managing geotechnical risk, before any site work starts. It is a staged, risk-based process with named engineers on both sides, and it runs alongside the separate legal consent to work in the highway. We carry the CD 622 side end to end, so what reaches the approving engineer is a complete, buildable, certifiable crossing.
The point of the standard is the ground, not the paperwork. A crossing under a live carriageway has to create a stable bore and keep the surface still, because settlement or heave at road level is what puts traffic at risk. So the design proves the crossing sits at the right depth for its diameter, controls settlement and heave inside agreed limits, and is watched before, during and after the works against a baseline. Each bore is assessed on its own cover, diameter and ground rather than to a single generic figure.
CD 622 works through a set of geotechnical reports, each certified in turn before the next can proceed, from the opening statement of intent to the as-built record after the works.
We produce that whole set, and provide the Designer's Geotechnical Advisor, the engineer CD 622 requires the promoter to nominate and National Highways to accept. National Highways accept a DGA who holds real, demonstrable trenchless experience for the works, which is the basis our submissions have been accepted on.
Each stage is signed off with its own geotechnical certificate. On a straightforward, low-risk scheme National Highways will sometimes accept some of the early reports combined into a single submission, covered by one certificate, which keeps the programme tight, with the design report kept on its own. Whether a combined report is accepted is National Highways' call, and every report's content still has to be covered either way, so it is safest to plan on each one being needed in its own right rather than assume they will be combined.
National Highways are clear that certification can take several weeks, and longer if a detailed ground investigation is needed. Because the reports are certified in sequence, the earlier we are brought in the less the approvals sit on the critical path. The legal consent to work in the highway runs in parallel and is needed before work starts too, so both are worth setting off together.
What we handle
| Standard | National Highways CD 622 Managing geotechnical risk (V2.0.0), the DMRB standard for trenchless crossings under the strategic road network |
|---|---|
| What we handle | The full geotechnical certification, from Statement of Intent through to the Geotechnical Design Report and certificate |
| Design basis | Eurocode design of the crossing, with settlement and heave kept inside the agreed limits |
| Monitoring | Carriageway surface monitored before, during and after the works against a pre-works baseline and trigger levels |
| Geotechnical advisor | We provide the Designer’s Geotechnical Advisor (DGA), accepted by the National Highways advisor on our trenchless track record |
| Track record | A multi-bore HDD crossing under the A19 designed and certified to CD 622, accepted by National Highways |
Each bore is assessed on its own cover, diameter and ground, not to a single generic figure.
A crossing we got certified
On the A19 at Easington to Peterlee we designed and certified a multi-bore HDD crossing under the live carriageway to CD 622, and the submission was accepted by National Highways. The Designer's Geotechnical Advisor role was fulfilled on the basis of our trenchless experience, the design ran the settlement for the conservative ground case where the investigation was limited, and the pack carried the full staged set, the combined early-stage report first, then the design report with its certificate. It is a working example of a real National Highways crossing taken from a line on a plan through to a certified, buildable design.
If you have a crossing in mind under a road National Highways manage, send us the road and the service and we will show you how it would be drilled, what the certification needs, and what it is likely to cost.
Questions answered
Yes. Any service installed by a trenchless method under the strategic road network, motorways and trunk roads managed by National Highways, needs geotechnical certification under CD 622 before site work can start. It runs alongside the separate legal consent to place apparatus in the highway. Both have to be in place before the crossing is built, so they are worth starting early. We handle the CD 622 side for you and dovetail it with the street-works consents.
Yes. CD 622 needs a Designer’s Geotechnical Advisor (DGA) nominated by the promoter and accepted by the National Highways Geotechnical Advisor. The DGA does not have to be a large consultancy. National Highways accept a DGA who holds significant, demonstrable trenchless-installation experience for the works in hand, which is the basis on which our submissions have been accepted, including the A19 crossing. On the larger or higher-category schemes we also bring in an independent checking consultant where the standard calls for one.
Allow for it in the programme. National Highways are clear that certification can take several weeks, and longer again if the desk study shows a detailed ground investigation is needed. The reports are certified in sequence, each one signed off before the next, so the earlier we are engaged the less it holds up the job. We often combine the early-stage reports into a single submission where National Highways agree the scheme is low risk, which shortens the run.
A staged set of geotechnical reports, each certified before the next: a Statement of Intent, a desk study, the ground-investigation scope and report, and then the Geotechnical Design Report that carries the full design. The design proves the crossing creates a stable bore and keeps settlement and heave at carriageway level inside the agreed limits, with the cover, diameter and ground assessed for each individual bore. The process ends with a signed geotechnical certificate. We produce the whole set and see it through to certification.
Yes. CD 622 requires the carriageway surface over the crossing to be monitored before, during and after the works, against a baseline survey taken before drilling starts. We set up the baseline and the grid of monitoring points, then read them through the job against the agreed trigger levels, so the ground movement that actually happens is checked against the settlement the design predicted.
Related services
The bore profiles, settlement calculations and approval packs behind a certified crossing.
View service →The ground data the CD 622 design and its risk register are built on.
View service →Our motorway and trunk-road crossings, and the jobs behind them.
View service →Tell us the road, the service and the line you want, and we'll come back on the crossing, the CD 622 certification and a budget price.