Underground Utility Detection


PAS128 – A specification for underground utility detection, verification and location

Inaccurate, incomplete and/or out-of-date information on the existence and location of utility assets reduces the ability to make informed decisions. This lack of reliable information during design and construction activities can result in costly conflicts, delays, utility service disruptions, redesigns, personal injuries and even loss of life.

What is PAS 128?

PAS 128 specifies requirements for the detection, verification and location of existing and new underground utilities.
It specifies requirements for the detection, verification and location of existing and new underground utilities, allowing the utility survey industry to deliver its services to a recognised level of accuracy.  It focuses on levels of accuracy – referred to as Survey Category Types – that you can specify when requiring a PAS 128 compliant underground utility survey.

What types of survey are there?

There are four Survey Category Types ranging from D - A:

  • PAS 128 Survey Category Type D
    Using utility record data only (not detected by geophysical methods).  This is the stage where a LSBUD search must be undertaken to be able to assess utility record information.

  • PAS 128 Survey Category Type C
    Using utility record data with site reconnaissance to match utility record with physical utility street furniture as a best fit.

  • PAS 128 Survey Category Type B
    Utility detected by geophysical methods (single or multiple) to obtain a horizontal position and/or vertical position. (Depth) For the positional accuracy of each QL-B sub category please refer to the Accuracy Diagram.

  • PAS 128 Survey Category Type A
    Utility verified and positioned by physical identification. This may be by strategically positioned vacuum excavation, hand dug trail pitting or by visual inspection within a utility chamber.

Who is it for?

This PAS is for use by practitioners (usually a surveyor, geophysicist or subsurface utility engineer). It also might be of interest to clients (such as engineers, constructors, project managers and utility owners), who are responsible for recording information about underground utilities.

Where ground investigation, borehole, trial pit works and other construction works are proposed, a current utility mapping survey conforming to PAS 128 can be used as an indicator of the presence or absence of underground utilities before conducting further ground investigation prior to breaking ground.

What does it cover?

It applies to the detection, verification and location of active, abandoned, redundant or unknown underground utilities and the location of their associated surface features. It applies regardless of where these utilities are located (e.g. in urban or rural areas, in the street, on private sites, such as hospitals or airfields). It applies to utilities buried no deeper than three metres.

PAS sets out the accuracy to which the data are captured, the quality expected of those data and a means by which to assess and indicate the confidence that can be placed in those data.  Although it is aimed at the survey practitioner, there are many LSBUD Users that may need to know how to specify a PAS 128 survey.

More specifically it covers:

  • project planning and scoping process,
  • classification system for quality levels based on survey category type, location accuracy, inclusion of post-processing and level of supporting data;
  • desktop utility records search;
  • detection;
  • verification;
  • location;
  • deliverables.

It does not however cover:

  • emergency utility works as defined by legislation or where there is imminent risk to life or limb;
  • underground basements, underground tunnels (including railways, road tunnels, and underground pedestrian walkways), plant rooms and non-utility based features;
  • above surface utility infrastructure (such as overhead power or telecommunication lines).

How can I find out more information?

For further information on PAS 128, visit: http://www.pas128.co.uk/
Alternatively, visit LSBUD online at www.linesearchbeforeudig.co.uk or call the team on +44 845 437 7365

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