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CD 622 guide
A crossing under a motorway or trunk road goes through a fixed sequence of geotechnical reports before the drill turns, then the works themselves with the carriageway watched throughout, then a close-out report. This guide walks through every stage in order. What each report is for, what goes into it, where the site information goes in (the boreholes, the utility search, the topographical survey), what we need from you at each point, and what you get back. It is written for whoever has to programme and pay for the crossing.
CD 622, Managing geotechnical risk, is the Design Manual for Roads and Bridges standard National Highways use to certify anything that changes the ground under or beside their roads, and a trenchless crossing counts. It is a staged, risk-based process. A named engineer on our side, the Designer's Geotechnical Advisor (DGA), writes a sequence of reports, and a named engineer on theirs, the National Highways Geotechnical Advisor (NHGA), reviews and certifies each one before the next can proceed. Nothing on site starts until the design report is certified. The legal consent to work in the highway is a separate process that runs alongside, and both have to be in place before the crossing is built.
The reports have a fixed order and set names, and clients ask us the same things about them. What is each one actually for, where do our boreholes and our utility search end up, and what will we be asked for. So here is the sequence for a straightforward bored crossing, with the works themselves in their place between the design report and the feedback report, because that is where the surface monitoring the design planned is carried out. If you want the short version and a price, the CD 622 crossings page is the place. This is the long version.
At a glance
| Stage | What it contains | Where the site information goes | What we need from you |
|---|---|---|---|
| 0 Before the first report | DGA nominated and accepted, geotechnical category agreed, OO reference issued, legal consent started | The utility records search starts now | The road, the line, what is due to be installed and the duct or pipe requirements, who the scheme owner is, any land outside the highway |
| 1 Statement of Intent (SoI) | Scope of the works, existing information, preliminary risks, category, proposed studies, programme | Nothing new yet, it records what already exists | Sign-off on the line and what is due to be installed, your anticipated programme dates |
| 2 Preliminary Sources Study Report (PSSR) | The desk study, the site walkover, the ground conditions expected, options and an updated risk register | Utility records, existing ground investigation, existing surveys, maps and site history | Anything you hold on the site, permission for the walkover |
| 3 Ground Investigation Scope Report (GISR) | The trial pits, boreholes and tests proposed, each justified against a risk, plotted, programmed and costed | The site-specific borehole locations, levels and depths are proposed here | The decision and budget on boreholes, land access for the GI rig, TM if required for the ground investigation equipment |
| 4 Ground Investigation Report (GIR) | The investigation results, the topographical survey, the ground model, the method chosen and why | Borehole and trial pit logs, laboratory results, the topographical survey | Nothing at this stage |
| 5 Geotechnical Design Report (GDR) | The full design, settlement and heave calculations, pipe loading, the surface monitoring plan, RAMS, risk register, certificate | The utility survey, the calculations, the drawings, the surface monitoring plan | Final duct or service requirements, accepted installation positions, agreed trigger levels, the NH emergency contact (obtained from NH) |
| 6 Installation works and surface monitoring | Baseline survey, the installation, monitoring during and for the agreed period after, the as-built survey | Every monitoring reading, the site records, the as-built | The permit, site access, TM approvals, a named contact for the readings |
| 7 Geotechnical Feedback Report (GFR) | The installation as-built, the surface monitoring results versus the calculations, problems and solutions, residual risks | Everything above, closed out and on record | Nothing, you receive it for the Health and Safety File |
CD 622's own report templates are written for whole road schemes, cuttings and embankments and the like. Everything below is those templates read for a bored crossing, with the earthworks content left out. Where a stage names a clause or an appendix, that is where it comes from in the standard.
Stage 0
Three things get set up before any report is written, and the earlier they are done the less they hold up the job.
Two other things start now and run alongside. The legal consent to place apparatus in the highway. A motorway is a protected street, so that means a Section 61 permit from NH Operations, plus a Section 50 street works licence if you hold no statutory powers, and the permit is only issued once the technical submissions are certified. And any land outside the highway boundary that the pits will sit on, because National Highways will not negotiate with third-party landowners for you and their own guidance says to allow proper time for it.
One more that catches people out. National Highways expect every existing utility near the drilling location, their own drainage, communications and power as well as third parties', to be identified before any works start, and that includes the ground investigation. So the records search begins here, not when the rig arrives.
| Where the site information goes | The utility records search starts now, so it is in hand before any hole is dug. National Highways expect every existing utility near the crossing, theirs and third parties’, to be identified before any works, and that includes the ground investigation. |
|---|---|
| What we need from you | The road and the line, what is due to be installed and the duct or pipe requirements (size, material, pressure or voltage), who the scheme owner is and whether they hold statutory powers to place apparatus in the highway, any land outside the highway the pits will need, and any previous correspondence with National Highways. |
| Then | DGA accepted, category agreed, OO reference issued, consent process started. The reports begin. |
Stage 1
The SoI is the opening document. It tells the NHGA what the scheme is, what we already know, what we think the geotechnical risks are and how we intend to close them out. It is short, but it sets the terms for everything that follows.
The SoI is also where two practical things are agreed. The proposed format of each report, and, on a straightforward low-risk crossing, a proposal to combine some of the early reports into one submission (more on that further down). If the low-risk case is going to be made, it is made here.
| Where the site information goes | Nothing new yet. The SoI records what already exists and what we intend to do about the gaps. |
|---|---|
| What we need from you | Sign-off on the line and what is due to be installed, your anticipated programme dates, and any records or reports you or your consultants already hold. |
| Then | Certified by the NHGA, generally within four working weeks of submission. On to the desk study. |
Stage 2
The PSSR is the desk study. It expands the SoI with everything that can be learned about the ground and the site without putting a hole in it, sharpens the risk list, and proposes what further investigation the risks that matter actually need.
This is where the utility records search goes in. The statutory undertakers' record drawings and National Highways' own drainage, communications and power records (obtained through NH Operations) are gathered and reviewed here, and the found and suspected services go on the plan. So does any ground investigation that already exists on or near the line, and any survey you already hold. If you have a topographical survey, or your consultant has done a desk study for the wider scheme, it is used here rather than repeated.
| Where the site information goes | The utility records search, any existing ground investigation on or near the line, any survey you already hold, the maps and the site history. |
|---|---|
| What we need from you | Anything you or your consultants hold on the site (surveys, ground investigation, drawings, records), permission for the walkover, and a contact at NH Operations if you already have one. |
| Then | Certified. The PSSR says what still needs proving in the ground, which is what the next report scopes. |
Stage 3
If the desk study leaves risks that only a hole in the ground can settle, the GISR sets out the investigation to close them. It is the report that says what trial pits, boreholes and tests are proposed, where, and why each one is worth doing against a named risk. The standard asks for a GISR for any and all ground investigation proposed, and the investigation itself follows the British Standards for ground investigation and laboratory testing.
This is the stage where site-specific boreholes are decided. National Highways' own guidance says ground investigation is likely to be needed for a motorway crossing, and that the quantity can be discussed with the NHGA once the SoI is done. Where the ground is soft enough we dig trial pits ourselves. Deeper boreholes and the laboratory testing we arrange through specialist ground investigation firms, specifying the tests that matter for a bore (strength, density, grading, plasticity, groundwater) and interpreting the results for the crossing. Where the existing information is already enough, the GISR says so and the investigation is kept small.
Where a client decides not to fund boreholes we recommended, that decision goes on record in the pack and the design is run conservatively in mitigation, but the residual ground risk then sits with the party who made the call. It is worth having that conversation early, with the numbers in front of you, rather than at the design stage.
| Where the site information goes | The site-specific trial pit and borehole locations, levels and depths are proposed and justified here, one line per hole, with the tests that go with them. |
|---|---|
| What we need from you | The decision, and the budget, on site-specific boreholes. Land access for the investigation rig, and traffic management if it is required for the ground investigation equipment. |
| Then | Certified. The investigation is carried out. Allow time for the laboratory testing, because the design cannot be finished without the results. |
Stage 4
The GIR is where the ground is settled. It brings together everything now known about the ground along the line, the existing information and the new investigation, into a ground model the design will be built on, and it states which method has been chosen and why.
The boreholes, trial pits and laboratory results are reported here, logged and interpreted, and the topographical survey along the line goes in with them, because the long section and the levels the design is set to come from it. The GIR is also the report that carries the factual data in AGS format, and once it is certified a copy of the factual report and the AGS file goes to the British Geological Survey, so the holes end up on the national record. The standard does not allow company-specific disclaimers on this report.
| Where the site information goes | The borehole and trial pit logs, the laboratory results, the topographical survey along the line, and the ground model built from them. |
|---|---|
| What we need from you | Nothing at this stage. This is our report on the investigation results. |
| Then | Certified. The ground is agreed and the design is finished against it. A copy of the factual data goes to the British Geological Survey. |
Stage 5
The GDR is the design proper and the report everything else exists to support. It carries the crossing as it will be built, the calculations that show it will behave, the surface monitoring plan for the works, and the geotechnical certificate that lets site work start. Nothing covered by the GDR can begin until it is certified.
The utility survey findings go in here, the located services plotted onto the layout with the clearance to each. The settlement and heave calculations, the drawings and the RAMS all attach to it, and the previous stage's certificate usually goes in for the record. On the A19 crossing we designed and certified to CD 622, the GDR package carried the ground investigation, the settlement calculations, the drilling and general RAMS, the frac-out plan, the drawings, the existing services drawings, the earlier certificate, CVs, the environmental data search and the monitoring RAMS, every one of them listed on the certificate.
One thing the guidance is explicit about. National Highways want the installation contractor to recognise, in the pack, that the method and the monitoring thresholds in the GDR can actually be achieved on site. Because we design and install, that is a single signature.
| Where the site information goes | The utility survey results plotted onto the layout, the settlement and heave calculations, the drawings, and the RAMS with the surface monitoring plan inside them. |
|---|---|
| What we need from you | Final duct or service requirements, the accepted installation positions and the land they sit on, the agreed trigger levels, and the emergency contact for the response plan, obtained from NH Operations. |
| Then | Certified. The Section 61 permit can now be issued. Site work can start. |
Stage 6
This is the stage the reports exist for, and it sits between the GDR and the GFR. The GDR wrote the surface monitoring plan. The works carry it out. What happens on the carriageway is read, recorded and reported as the job runs, and all of it ends up in the feedback report afterwards.
The monitoring is done by us, by the employer's engineer, or by a specialist survey team where the job requires it, against the plan in the GDR either way, and it is the same monitoring whoever holds the instrument. Settlement is one thing it looks for. It also looks for heave and any other ground movement, which is why we call it surface monitoring rather than settlement monitoring.
If a trigger is breached, the scheme owner carries the liability for any damage to the carriageway or utilities, and the permit will normally refer to the agreed emergency response plan. That is the practical reason the trigger levels and the response plan are worth reading properly at the GDR stage rather than after.
| Where the site information goes | The baseline survey and every monitoring reading, the drilling records, the as-built survey and the site photographs. |
|---|---|
| What we need from you | The permit in hand, site access, the traffic management approvals, and a named contact on your side for the readings. |
| Then | Pipe in, monitoring run to the end of the agreed period, records collated. The last report closes it out. |
Stage 7
The GFR is the as-built record. It is produced by the DGA within six months of the end of construction and it tells whoever comes after exactly what was put in the ground, where, what was met on the way and how the carriageway behaved. It also feeds back anything the standard or the specification should learn from.
The GFR forms part of the project's Health and Safety File under CDM 2015. It is the document that protects the next person to dig near your crossing, and if National Highways require a Health and Safety File for the installation it includes the certified GFR.
| Where the site information goes | Everything above, closed out and on record. |
|---|---|
| What we need from you | Nothing. You receive it, and it goes into your Health and Safety File. |
| Then | The crossing is complete on National Highways’ record, and on the national record too, because the factual ground data went to the British Geological Survey after the GIR. |
The standard lists a seventh document, the SGMF. It only applies where a specialist geotechnical element (a reinforced soil wall is the standard's own example) is designed by a subcontractor, and the DGA uses it to hand that specialist the risks and the information they need. It has no place on a straightforward bored crossing and you will not usually see one.
For a straightforward, demonstrably low-risk scheme, and the standard names under-road crossings as its example, the reports may be combined and their content amended, with the NHGA's agreement recorded in the SoI. In practice National Highways commonly accept the SoI, PSSR, GISR and GIR together as one submission with one certificate on a low-risk crossing, and it is best to keep the GDR as its own submission with its own certificate. The GFR is never combined. Combining does not remove any content, every report's content still has to be covered, so plan on each stage being needed and treat a combined submission as a bonus rather than the baseline. The A19 crossing ran exactly that way, a combined SoI to GIR submission first, then a standalone GDR.
National Highways' own guidance for directional drilling under a motorway says the timescale from route determination through planning, design, construction and close-out can be around a year. Inside that, each submission generally gets a response within four working weeks, certification itself can take several weeks, and longer again if the desk study shows a detailed ground investigation is needed, because the laboratory testing has its own lead time before the design can be finished. Land agreements outside the highway and traffic management approvals for the survey kit have their own lead times too.
The things that shorten it are all at the front. Appointing the DGA and getting them accepted early, agreeing the category and the combining of the early reports at the SoI, deciding on boreholes promptly, and setting the legal consent off in parallel rather than after. The reports are certified in sequence, so a week lost early is a week lost at the end.
Questions answered
Often, yes. For a straightforward low-risk crossing, and CD 622 names under-road crossings as its own example, the reports may be combined with the NHGA's agreement, recorded in the Statement of Intent. National Highways commonly accept the SoI, PSSR, GISR and GIR together as one certified submission, with the Geotechnical Design Report kept on its own. The feedback report is never combined. Every report's content still has to be covered, so combining shortens the sequence rather than removing anything from it.
The Ground Investigation Scope Report proposes them, hole by hole with the risk each one is there to settle, and the quantity is discussed with the NHGA once the Statement of Intent is done. National Highways' own guidance says ground investigation is likely to be needed for a motorway crossing. The client funds it. Where the ground is soft enough we dig trial pits ourselves, and boreholes and laboratory testing we arrange through specialist firms and interpret for the bore. If an existing investigation on or near the line is good enough, we say so and keep it small. If we recommend boreholes and you choose not to fund them, that goes on record and the design is run conservatively in mitigation, but the residual ground risk then sits with you.
In two places. The records search, the statutory undertakers' drawings and National Highways' own drainage, communications and power records, is gathered in the desk study (the PSSR), and National Highways expect the utilities to be identified before any works, including the ground investigation. The survey on the ground, the electromagnetic and ground-penetrating radar locate along the line with covers lifted to read depths, feeds the design and goes into the GDR as the located services plotted on the layout with the clearance to each. When the crew arrive they sweep the line again before breaking ground and prove anything critical by hand.
It is carried out by us, by the employer's engineer, or by a specialist survey team where the job requires it, and in every case it is done to the plan set out in the GDR, the same baseline, grid, frequency and trigger levels. The readings are passed to you and to National Highways as the job runs, and the full set goes into the Geotechnical Feedback Report against the values the design predicted. It watches for settlement, heave and any other ground movement, which is why we call it surface monitoring rather than settlement monitoring.
The GDR sets green, amber and red trigger levels, which can differ for settlement and heave, with an action written against each, and the Monitoring Action Plan and Emergency Response Plan in the RAMS say who does what and how quickly. What each level triggers runs from more frequent readings and a review of the drilling parameters at the lower levels through to stopping the works and running the response plan at the top one, with National Highways' emergency contact informed. The scheme owner is liable for any damage to the carriageway or utilities if triggers are breached, and the permit will normally refer to the agreed response plan, so it is worth reading the trigger levels properly at the design stage.
The certified reports with their certificates (the early stages, combined or separate, and the GDR), the design drawings, the settlement and heave calculations, the RAMS with the monitoring and response plans, the baseline survey and the full set of monitoring readings, the as-built survey of the installed line and levels, and the certified Geotechnical Feedback Report for your Health and Safety File. The factual ground data also goes to the British Geological Survey, so the boreholes end up on the national record.
No. CD 622 is National Highways' standard and it applies to the strategic road network, the motorways and trunk roads they manage. A local road is the local highway authority's, with its own permit scheme and its own requirements, and it does not run the CD 622 sequence unless the authority chooses to ask for it. Where a crossing spans both networks, both authorities have to be consulted, and where Network Rail is affected their own procedures apply as well.
Related
The short version, what we do on a CD 622 crossing and the A19 we designed and certified.
Read more →The bore profiles, settlement and heave calculations and approval packs behind the GDR.
Read more →The trial pits, boreholes and testing the GISR proposes and the GIR reports.
Read more →Send us the road, the service and the line, and we will tell you which stages your crossing needs, what we already hold, and what we need from you.