By Andy Gundry, Head of Utilities and Neil Gregory, Head of Client Engagement – Utilities at Plowman Craven

Earlier this year the standard relating to underground utility detection, verification and location was updated. Called PAS 128: 2022, this British Standards Institution (BSI) Specification moves the 2014 standard forward and defines the way underground utilities should be mapped. With an emphasis on enhanced accuracy, anyone involved in the planning and design of construction and infrastructure projects needs to be aware of the update and what is now required. Here we set out how the changes are impacting the market.

A reminder about PAS 128: 2022

PAS 128 is the UK standard for surveying existing utilities and their surface features as well as planning for new infrastructure. It applies across the country, whether that’s urban or rural areas, in public places or on private sites.

It’s worth noting that the standard updates have been undertaken to improve the quality of surveys for both new and existing underground utilities. This is not just because accuracy is more helpful in the design, planning and delivery phases – reducing conflict, delay, unnecessary work, damage to third party assets, utility service disruptions and redesigns – but also because health and safety is a key consideration.

Clients, architects and contractors have duties under the Health and Safety Executive ‘Avoiding danger from underground services’ guidance known as HSG 47. Clients must make reasonable enquiries about underground services and pass relevant information to the designer and contractor. This is usually based on a PAS 128:2022 QL-D utility record search (desktop search) and potentially a QL-C site reconnaissance survey (visual inspection).

Designers in turn have a duty to reduce or ‘design out’ the risks arising from damage to underground services. Then, contractors must identify potential hazards, assess risk and put safe systems and clear communication in place for their employees, which also safeguards against damage to essential services. This will be based on the findings of the QL-D and QL-C as well as a PAS 128: 2022 QL-B or QL-A surveys for the benefit of safety.

Key updates in the 2022 version

The survey process remains very much the same, but with more comprehensive desktop utility record searches leading to on-site visual inspections to geophysical techniques to detect underground utilities to verification through observation, excavation or exposure. In short, data accuracy has become more prominent and there is more consistency with less room for interpretation.

So, what are the changes? In undertaking the surveys, more detail is now specified on the search method and methodology:

• Incorporation of new technology to include GPR arrays and their use in reconnaissance route mapping prior to Type B survey works • Addition of guidance on training and qualifications of practitioners – every survey practitioner should be qualified to level 3 or 5 NVQ in underground utility mapping • Greater emphasis on the importance of GPR post processing by suitably trained operatives and the recording of all raw data regardless of the post processing requirement • Updates to the application of post processing in detection surveys – M3P/M4P replacing M3/M4 • New guidance on the technical factors that dictate the effort required for a detection survey – 2 geophysical methods / full coverage of sites / recording of all raw data regardless of the post processing requirement • Sharing of data in one large data base (NUAR) National Underground Asset Register has been encouraged – this is to update or improve any known utilities in any location where only statutory, often inaccurate, records are available

It’s also worth noting that the 2014 standard referred to utility assets up to 3 metres deep but this has been removed, with the implication therefore is that it applies to any depth. Further, PAS128 2022 applies regardless of where these utilities are located (e.g., in urban or rural areas, in the street, or on private sites such as hospitals or airfields). It is critical that anyone involved in the planning and design of construction and infrastructure projects is familiar with the updated standard.

The good news is that all of the changes will have positive impacts on the industry. For example, while the technology guidance still lists the same two general methods of detection – Electromagnetic Location (EML) survey and Ground Penetrating Radar (GPR) – it has made GPR data collection and interpretation compulsory across specific environments such as busy urban or congested City areas. This is good news because historically GPR has not always been included in the due diligence phase despite enabling a larger data set for highly congested areas, which brings with it better results, more confidence in the data, lower risk and enhanced H&S information. The standard also stipulates GPR array systems which adhere to the highest PAS levels as standard (M4P).

That said, GPRs and the processing of the resulting data requires a significantly higher investment, which may force smaller companies towards less regulated standards due to cost. Plowman Craven is fully supportive of the advancement of best practice, but it needs to be accessible and viable for projects of different sizes.

More stringent rules now apply around what information is provided. For instance, deliverables need to be clearly explained in terms of the survey type, how many methods were used, reporting including statistics, dates when drawings were requested and when a response was provided clearly dated, and details of equipment calibration. As practitioners, we now have an obligation to hold data for greater periods of time and make this available to our clients upon request, this is inclusive of all RAW data obtained on site.

Last but not least, the use of multi array antennas aid better understanding of the sub surface environment including the detection of voids, buried structures/chambers, underground storage/attenuation tanks and former/buried foundations. This, coupled with the use of intelligent software packages (AI supported processing tools), allows practitioners to gain a better understanding of the sub surface.

In conclusion

The new standards are more rigorous, demand more accuracy or data collection as well as reporting.

This can only enhance the benefits PAS 128:2022 brings:

• More effective planning and safer execution of street works, civil works and ground works. • It provides clarity about the approach to surveys and a consistent approach to data capture. • It enables better informed decisions using more complete, up-to-date, and accurate data. This helps ensure the safety and timely progress of projects. • It can help prevent or reduce conflicts, delays, unnecessary work, damage to third party assets, utility service disruptions, redesigns, personal injuries and loss of life.

In response to the changes, we at Plowman Craven have invested in the latest technology to meet the revised M3P and M4P PAS levels enabling us to provide fast, safe and non-invasive surveys whilst maintaining highly accurate and comprehensive deliverables to clients. Mobile GPR allows us to complete feasibility studies early in the project lifecycle, which aids route mapping, allows designs to be adjusted to avoid underground anomalies and generally makes the process smoother.

The last decade has seen a dramatic increase in the volume of utilities related construction work for maintenance, enhancement and new development purposes. This has brought with it more risk, for those carrying out work on or near underground services, so any standard that helps safeguard them and eliminates risk across the entire project at the same time is very welcome. Surveys done correctly and to a high standard and carried out early in the design process deliver a significant return on investment every time.