PAS 128 Survey Type B (Detection)

What is a PAS128 Survey Type B (Detection)?

As defined in PAS128 it is “The remote detection of underground utilities uses geophysical techniques. As the survey area is scanned, signals are received and analysed for anomalous responses. If the positions of these anomalies form linear strings they can be interpreted as features, such as utilities.”

This means that, unlike Survey Types D & C, Survey Type B can identify the location of utilities both horizontally and vertically within clearly defined accuracies based on methods of the location used.

Why would I consider requesting a PAS128 Survey Type B?

Some of the main reasons for undertaking Survey Type B are:

• Survey Type D (Desktop) has been carried out and there is a high density of utilities within the site area.
• Survey Type C (Site Reconnaissance) has been carried out and has identified clear discrepancies between owner-provided utility information and onsite surface feature locations within the site area or unable to locate surface features.
• Ground excavation work is required, so a more accurate location of utilities is needed in compliance with HSG47 (Avoiding Danger from Underground Services).

Methodology

A utility survey team will visit the site; they will have with them all owner-provided utility information (Survey Type D) and equipment to carry out a full site utility detection. PAS128 specifies that there are two minimum techniques for the geophysical locating of utilities. These are:

• Electro Magnetic Locating (EML) using a hand-held receiver and signal transmitter.
• Ground Penetrating Radar (GPR) and when required post-processing of recorded data.

Both techniques (when used on their own) have limitations but combined they give a far greater chance of accurately locating any utilities within the site area.

All traced utilities are marked up on site and recorded using GNSS and total station for accurate mapping of utilities.

Quality Levels

All detected utility segments will be given a quality level up to QL-B1P following PAS128 format.

Deliverables

All utility survey data will be presented in a digital model format to clients’ specified requirements and will have a supporting utility survey report which will include methods of detection used, any concerns about individual utilities that may require further investigation, an overall summary of all site findings and where possible photographic site evidence to support survey findings.