These FAQs are based on guidance provided by The Survey Association (TSA) and BSI PAS 128 and are provided to give a summary of what constitutes an underground utility survey – and the value for money it represents.
Image

What is an underground utility survey?

Why carry out underground utility surveys?

What techniques are used?


What results can be expected from a survey?


What are the limitations of a survey?


What level of survey do I require?


Further questions

 


What is an underground utility survey?                                                                   

This is the process of carrying out both desk-based and site investigations using a variety of non-intrusive techniques to provide accurate plans of the buried utilities within a specified survey area.

top


Why carry out underground utility surveys?

Many benefits arise from having good quality mapping of the buried utilities of a site, including:

  • Ensuring safety of both the public and the workforce during construction work
  • Minimising cost and disruption arising from damage to existing utilities
  • Minimising project delays
  • Optimising designs of new works by knowing the constraints of the site

top


What techniques are used in carrying out these types of surveys?

Several technologies can be used to obtain information on the position of buried pipes and cables. Each will have a varying degree of success and accuracy in a given environment. When performing an underground survey it essential that the appropriate equipment and methodology is used in the best way for the given situation. Each will find some pipes and cables in some situations, whereas, with an educated approach, most if not all utilities can be accurately determined in a wide variety of situations. The two most commonly used techniques are radiodetection locators and ground penetrating radar (GPR). SafeGround operators have many years’ experience with both techniques to bring you the best survey solution.

 top


What results can be expected from a survey?

At the end of this document is a summary of the different levels of survey that are suggested to satisfy the various client requirements for utility tracing and mapping. Though ‘mark out’ on site may be appropriate in some instances, it is recommended that the results be provided as plots onto accurate base mapping. We can provide a range of drawing formats including CAD, DXF and DWG.

top


What are the limitations of a survey particularly concerning accuracy and depth of investigation?

Some of the main criteria affecting the success of a survey will be the site conditions, the sub-soils and the depth and type of utility being surveyed. As long as these factors are not too constraining, positional and depth accuracies of around 50–150mm can be expected down to a depth of 1.5–2m. It is possible to detect larger utilities at greater depths. It must be appreciated that radiodetection will not detect non-metallic utilities whereas GPR should pick up most material types.

However, even with a full comprehensive multi-technique PAS 128 survey, we cannot provide a 100% guarantee that every single utility has been detected. No company can provide this without undertaking costly multiple excavations. However, we do ensure that every effort has been made to locate the buried services and obstructions using a range of techniques to provide you with the means that all reasonable care has been taken.

top


What level of survey do I require?

In 2014, the British Standards Institution (BSI) issued a new Publically Available Specification (PAS) 128, which specifies the minimum that should be done in respect to underground utility detection, verification and location, and also provides guidance and pointers to best practice.

RSK are proud to have been part of the team that helped develop the new standard. RSK's George Tuckwell was on the steering committee developing the standard, and was seconded onto the drafting panel to help write the section on detection (To view George's presentation of the standard click here).

PAS 128 gives the client much more control over the specification of the survey and the tools to hold the practitioner accountable for their data acquisition and deliverables. Utility surveyors can no longer operate to unknown levels of quality that produce varying levels of detail and then hide behind the  “black box “ of GPR as an excuse.

The new PAS 128 standard sets out 4 category types (levels of accuracy) of survey:

top


Further questions

We are always happy to advise on principles and techniques. To discuss the benefits of a well-designed and well-executed survey, please feel free to contact us for more information.

top

 
 
Contact usSite map

© 2015 RSK Group plc, All Rights Reserved.
Contact: + 44 (0) 1442 416 656, safeground@rsk.co.uk

      Follow us on  Twitter  Facebook  Youtube  linkedin  RSK GROUP RSS  Bookmark and Share