CDM 2015 Regulation 11(6) compliance for buried services

Who Regulation 11(6) applies to, and what it actually says

Regulation 11 of CDM 2015 sets out the duties of the principal designer during the pre-construction phase. Subsection (6) is the part that bites for buried-services risk. The text, taken from the regulations as made, is:

“The principal designer must—(a) assist the client in the provision of the pre-construction information required by regulation 4(4); and (b) so far as it is within the principal designer’s control, provide pre-construction information, promptly and in a convenient form, to every designer and contractor appointed, or being considered for appointment, to the project.”

CDM 2015, Regulation 11(6) — Construction (Design and Management) Regulations 2015 (SI 2015/51).

The duty applies on any project with a principal designer, which under CDM 2015 means any project involving more than one contractor. It runs alongside the wider duties in Regulation 11(1) to plan, manage and monitor the pre-construction phase, and Regulation 11(3) to identify, eliminate and control foreseeable risks so far as is reasonably practicable. Buried services are one of the most common categories of foreseeable risk that those duties capture.

The “so far as is reasonably practicable” standard

“Reasonably practicable” (often written SFAIRP) is the standard the HSE and the courts apply when judging whether a duty has been met. It is not a best-endeavours test and it is not an absolute test. The accepted formulation, drawn from Edwards v National Coal Board [1949] 1 All ER 743, is that a duty holder must take steps to reduce risk unless the cost of doing so is grossly disproportionate to the risk reduction achieved.

For buried services this gives a workable test. If a recorded utility runs through the works footprint, a QL-D records search alone is rarely SFAIRP for a deep excavation project. Commissioning a PAS 128 QL-B detection survey of the works footprint is, in most cases, a proportionate next step — and at high-consequence crossings, QL-A verification by vacuum excavation. The investigation continues until the residual risk is as low as the proportionality test will reach. The reasoning behind each stopping point is what the principal designer records in the pre-construction information.

The companion guide on PAS 128 quality levels walks through how each QL contributes to that proportionality argument.

What good pre-construction information looks like

The HSE’s Approved Code of Practice for CDM 2015 (L153) describes pre-construction information as “the information about the project that is already in the client’s possession or which is reasonably obtainable” and which is needed by designers and contractors to comply with their duties. For buried services, “reasonably obtainable” has materially changed since NUAR went live: records that previously required individual statutory undertaker requests are now obtainable in minutes.

A good pre-construction information pack for buried services covers, at a minimum:

• The full set of records obtained, with source, date of extract and licence basis (NUAR licence, statutory undertaker records, asset owner GIS).
• A site plan showing every recorded utility within and adjacent to the works footprint, with owner and asset type identified.
• The PAS 128 quality level of each record, and where higher-quality investigation has been carried out, the survey report.
• Recorded depth and material information where available, with explicit flagging where it is absent.
• Status of recorded assets (live, abandoned, under verification), with the acknowledgement that abandoned status is itself a quality-of-record question until verified.
• Residual risks for the principal contractor to manage on site, including risks that have not been investigated and why investigation was not reasonably practicable.
• The risk methodology used to combine the above into an overall site risk band.

The compliance gap: why most projects fail the test

The most common failure mode is fragmentation. The principal designer holds a NUAR extract. A separate consultant holds the ground investigation report. A third party holds the flood data. None of them are integrated, none of them are time-stamped against the same site polygon, and the “pre-construction information” handed to the principal contractor is a folder of PDFs in different scales and projections.

The integration gap is where strikes happen. A NUAR extract shows a gas main but omits a flood-zone overlap that affected an earlier abandonment decision. A borehole record from BGS would have flagged a contamination zone, but it was never overlaid. GeoSure data showing high shrink-swell potential changes the depth profile of the excavation, but it was never read against the utility record.

Compliance with Regulation 11(6) is, in practice, an integration problem. The records exist. NUAR, the EA flood layers, BGS boreholes and GeoSure are all free or accessible to the principal designer. The duty is to combine them into pre-construction information that is provided “promptly and in a convenient form” to every designer and contractor — not to leave each party to integrate them themselves.

A risk-assessment workflow: data → analysis → report → handover

1. Define the site polygon. The works footprint plus a buffer appropriate to the risk profile (commonly 5–10 m for shallow works, larger for deep excavation or piling). All subsequent analysis is bounded by this polygon and hashed against it.
2. Pull records (QL-D). Extract NUAR data for the polygon. Cross-check against asset-owner records where the asset is known to be of high consequence. Record the extract date and licence terms.
3. Overlay enrichment data. EA flood zones, BGS boreholes, GeoSure shrink-swell and ground-stability layers, MRA coal mining hazard where applicable. These are inputs to both the consequence and the data-quality terms.
4. Validate and detect (QL-C / QL-B). Walkover; commission a PAS 128 QL-B detection survey of the works footprint at the tier the design requires.
5. Verify (QL-A). Vacuum excavate or trial-pit at high-consequence crossings and planned excavation points.
6. Score and band. Combine consequence, proximity and data-quality terms into an asset-level risk score. Aggregate to an overall site risk band.
7. Report and hand over. Issue the structured report to all appointed designers and contractors, and to the principal contractor for inclusion in the construction phase plan. Archive the report alongside the health and safety file.

How a CDM-compliant buried-services report is structured

The internal structure varies by client, but the sections below are the minimum a report needs to support Regulation 11(6) and Regulation 11(3) at the same time. The report we produce in NHDM uses a structure of this kind.

Common pitfalls and HSE enforcement themes

Records pulled but never integrated

NUAR is queried, but the extract is filed without being overlaid against flood, borehole and ground-stability layers. The strike happens at the overlap that nobody saw.

Records treated as design-grade

A QL-D record is used to set excavation depth or to position a pile. The principal designer assumed accuracy the records cannot provide. This is one of the most consistent themes in post-incident HSE narratives.

Survey scope mismatched to risk

A QL-B detection survey is commissioned at a coarse tier (QL-B4) when the design depends on detail that only QL-B1 or QL-A would resolve. The survey looks like compliance, but the residual risk has not actually moved.

Residual risk not communicated to the digger

The information sits in the pre-construction information pack but never reaches the operative on site. The principal contractor’s permit-to-dig system has to be designed to pull risk information through to the point of work, not just to the office.

No audit trail

The report exists but cannot be re-derived. The site polygon, NUAR extract date, analyst and methodology version have not been captured. After an incident, the investigation cannot establish what the principal designer actually saw.

Where NHDM fits

The National Hidden Data Map (NHDM) is a buried-services risk scoring tool we are building specifically to support Regulation 11(6) workflows. The user defines a site polygon; NHDM integrates NUAR, EA flood, BGS borehole and GeoSure data; an asset-level risk score is produced for every utility in the works footprint; and a structured PDF report is issued with a fixed, versioned methodology, suitable for inclusion in pre-construction information. The risk formula combines consequence, proximity and PAS 128 data-quality terms — the data-quality element draws directly on the framework described in our PAS 128 quality levels guide.

The principal designer remains the duty holder. NHDM is a tool that integrates the evidence and produces a defensible artefact; the judgment about what is reasonably practicable for the project is still made by a competent person. For the legal context around NUAR’s licensing terms, see our existing insight on NUAR and the CDM liability.

FAQ

Who is the principal designer under CDM 2015?

The principal designer is the duty holder appointed in writing by the client for any project involving more than one contractor. The role is held by an organisation or individual with the required skills, knowledge and experience to coordinate health and safety during the pre-construction phase. On smaller projects the client may take on the role themselves, but the duties under Regulation 11 still apply.

Does Regulation 11(6) apply to small projects?

Yes. CDM 2015 applies to all construction projects regardless of duration or notifiability. Regulation 11 duties are scaled to the project, but the obligation to assist the client in providing pre-construction information and to share that information with appointed designers and contractors applies on any project with a principal designer.

What counts as pre-construction information for buried services?

At a minimum, pre-construction information should cover known utility ownership and routing across the site (typically from NUAR or statutory undertaker records), the quality level of those records under PAS 128, any depth or material information available, the status of recorded assets (live, abandoned, under verification), and the residual risks that the principal contractor will need to manage. It should also identify what investigation has not been done and why.

Is using NUAR enough to satisfy Regulation 11(6)?

NUAR is a fast and broad records source — in PAS 128 terms, QL-D. It is a strong start for the records dimension of pre-construction information, but it is not a substitute for site investigation where the risk profile warrants QL-B detection or QL-A verification. Using NUAR alone for design that depends on accurate position or depth is one of the recurring gaps we see on audit.

What does "so far as is reasonably practicable" mean for buried services?

It means the principal designer must balance the level of risk against the time, cost and trouble of investigation, and only stop investigating when the cost is grossly disproportionate to the risk reduction. In practice this drives a tiered approach: QL-D records across the whole site, QL-C validation in works areas, QL-B detection of the works footprint, and QL-A verification at planned excavation points and high-consequence crossings.

How long should pre-construction information be retained?

CDM 2015 does not set a single retention period for pre-construction information itself, but the health and safety file (which captures residual risks for future maintenance and demolition) must be handed to the client at project end and retained for the life of the asset. As a practical matter, buried-services records and the data-quality evidence behind them should be archived alongside the health and safety file for the same period.

What are the most common HSE enforcement themes for utility strikes?

Recurring themes in HSE enforcement and prosecution following utility strikes include failure to obtain and use available records, failure to commission a site survey where the records were obviously inadequate, failure to communicate residual risks to the operative actually carrying out the dig, and inadequate permit-to-dig systems on site. Many of these failures originate in the pre-construction information rather than on site.

Does NHDM produce a CDM-compliant report?

NHDM is built to support CDM 2015 Regulation 11(6) pre-construction information. It generates an asset-level risk register from NUAR, EA flood, BGS borehole and GeoSure data for any site polygon, with PAS 128 quality levels and proximity zones applied, and outputs a structured PDF report that includes the methodology, the asset register, residual risks, and the data sources used. The principal designer remains the duty holder; NHDM is a tool that produces the evidence pack.