What is PAS 128?

PAS 128:2014 is the latest specification for underground utility detection, however a new revision to the standard is being released in 2022 (watch our video here). The purpose of the PAS 128 specification is to set out clear requirements when carrying out the detection, verification and location of active, abandoned, redundant or unknown utilities. It applies in all areas that any utilities are present and are no deeper than three metres underground (for example in urban or rural areas, in the street, or private sites, such as hospitals or airfields).

PAS 128 provides a strong procedure for delivering utility surveys in the UK. There are four Survey Category Types referred to in the specification and each one focuses on levels of precision specified in an underground utility survey that is PAS 128 compliant.

Anthony Burd, Head of Market Development for Construction at BSI said: “The application of PAS 128 is not just restricted to current solutions, but will afford as yet unrealized benefits. For example, the use of remote robotic techniques to maintain asset networks in busy highways in future to reduce the need for intrusive maintenance practices (road excavations). Similarly, accurate mapping of utility networks could improve asset modelling capabilities with more determined outcomes.” (source: BSI Group)

Many respected organizations were involved in the development of the PAS 128 document including: Chartered Institution of Civil Engineering Surveyors, Heathrow Airport Holdings Limited, Highways Agency, Institution of Civil Engineers, National Joint Utilities Group and Transport for London.

Benefits of the PAS 128 specification

Following PAS 128 ensures a high level of accuracy and certainty of the results for each utility detection survey. This increased accuracy and reliability provided to the client enables them to plan effectively for all utility-based activities.

Catsurveys recommend that the PAS 128:2014 document is consulted in conjunction with all detection surveys provided, as an aid in understanding the survey results. It is also beneficial when considering a utility survey and the level of information required.

Although it is a voluntary guidance, the higher standards set by these guidelines ensure confidence and reliability of the results. PAS 128 creates a common environment for both the client and contractor to specify, survey and deliver data.

Survey Quality Types

With a selection of survey types, detection methods, quality levels and geospatial locations, the PAS 128 survey criteria cover various aspects of the development process including: project planning and scoping, classification system for quality levels, desktop utility records search and detection, verification and location.

The following survey definitions are used in PAS 128:

Survey type D – Desktop utility records search

Desktop utility records search (DURS) is the identification of underground utilities via the collation and analysis of existing utility records. Downtime can sometimes occur due to the late arrival of DURS. Catsurveys’ specialised DURS team can reduce delays during the Underground Utility Detection process and provide information quickly and efficiently to our clients.

Survey type C – Site reconnaissance

Site reconnaissance is a desktop exercise combined with a site walk-through and is aimed to confirm the route proposal (where Underground Utility Detection may not be necessary). Our team can walk the site and provide a Custom Street View (CSV). This allows us to visually identify any potential hazards from surface level which we can feedback before further Underground Utility Detection takes place. The study is handed over to the client in CAD, PDF, Word and Excel formats and inclusive of the proposal being superimposed on the route photographs.

Survey type B – Utility detection using EML and GPR

Multiple underground utility detection procedures can take place to provide the most accurate and detailed mapping. Both electromagnetic location (EML) and ground penetrating radar (GPR) are used to detect each utility within the survey boundary. Each detection method is recorded geospatially, and the data is compared against existing utility records. By evaluating this data, a clearer understanding and parameters of confidence can be established.

Survey type A – Verification via intrusive inspection

Underground utility detection begins with manhole reporting and verification of all manholes that could affect the specified area. This underground utility detection method can be extended beyond the site boundaries if required.

Verification of a utility that does not have an access point can be achieved by means of trial holes. Catsurveys will carry out a full PAS 128 survey of the required area, marking all utilities which have been located on the ground around the excavation site. If we were unable to locate any utility, shown to be present from existing utility records, this would also be marked to show their presence.

Why is the implementation of PAS 128 important?

As the demand on the nation’s infrastructure continues to rise, due to newly constructed developments, the requirement to replace and maintain existing utilities increases. Inaccurate or incomplete information on the existence and location of utility assets can be damaging when making decisions on new utilities or rehabilitation works. A lack of reliable information during design and construction activities can result in expensive conflicts, the safety of workers and the public being put at risk, unnecessary work often needs to be terminated, damage to third party assets and wasteful design solutions.

As a result, it is vital that accurate information for the location of underground utilities is available. Accurate mapping of utility networks helps to improve asset modelling capabilities with more resolute outcomes.

Have confidence in Catsurveys

We asked our Principal Utility Surveyor, Joe White, what impact the specification has had on how we operate. “In a way, the implementation of PAS 128, has simplified the way we operate. Before, we had to interpret what the client wanted and the level of survey they required. Now, there is basically a menu of surveys they can request which is standard across the industry.” Joe explains. “There is also a choice of how in depth we go to achieving the required results. It clearly sets out the quality levels we should be able to obtain, and the percentage of utilities located, based on this choice.”

We asked Joe if he believes PAS 128 improved the way we work and the results for our clients; "Certain clients require different levels of information and accuracy. We can advise them on the different level of survey available, possibly saving time and money."

"The way a survey is now carried out has become more standardized. We, as a company, have inserted certain procedures to comply with PAS 128 and record quality levels as the survey is progressing. Previously, if we were unable to locate a certain utility to any degree, we had to justify this somehow. With PAS, we now have quality levels, giving a sliding scale of confidence. On the positive side, when we state that we have located a utility with multiple techniques, we can offer a higher quality level. Our client can revue our survey and relate it to PAS, they will be confident that our findings are a true reflection of what is achievable from a survey." Explains Joe.

"In summary, I think that PAS reinforces the quality surveys we had been producing in the past and will continue deliver in the future."

We believe that it is important to work with an experienced company that you can trust. Don’t settle for less, contact us for a quote today.