Introduction

When you need to know the location and type, size, depth and number of underground utilities, it is important to ensure that when engaging a consultant or specialist surveyor, that the enquiry or instruction is clear and preferably uses a known, robust and respected specification. There are many ways of providing data to depict underground utilities. These include providing record drawings, historic data, site visits, detecting the underground utilities via various geophysical survey methods and excavating to confirm location.

The Chartered Institution of Civil Engineering Surveyors (CICES) suggests clients consider the PAS 128:2022 Specification for the detection of underground utilities. This has been developed with input and advice from professional bodies, survey practitioners, technology providers and academia and it is recommended that it is referenced in any specification document to ensure that tender returns are robust and technically sufficient. The PAS 128:2022 Specification for underground utility detection, verification and location can be purchased from the BSI website.

You will need to specify in detail the type of PAS 128 survey required when you enquire, as well as the level of detail that you need and expect from a surveyor. This will ensure that you receive the type of survey you are expecting, plus the level of detection, quality and type of data presentation that you need.

PAS 128:2022 provides example project workflow diagrams within Annex E (informative) on pages 55-59 inclusive, to assist with project planning.

PAS 128 is split into four different survey types which can be used to determine the quality level of survey data provided to the client by the surveyor:

• Survey Type D: Desktop utility records search
  This is where underground utilities are approximately identified through the collation and analysis of existing paper and digital utility records via a thorough search of potential asset owners.
• Survey Type C: Site reconnaissance
  This is where existing records are supported and validated by the visual inspection of above-ground physical evidence observed or recorded during a site visit.
• Survey Type B: Detection 
  This is where underground utilities are detected by geophysical techniques, visual inspection, metadata collection and are geospatially located.
• Survey Type A: Verification 
  This is where underground utilities are visually identified via a manhole or inspection chamber or are excavated and exposed.

About this guidance

The CICES specialist Utilities and Subsurface Mapping Panel (USMP) has produced this best practice guidance to assist clients when specifying verification, detection and location for PAS 128 survey types D, C, B and A. 

When you see the symbol  this is where we suggest text clients could copy to help them in seeking robust, informative and clear tender returns.

This document should be read in conjunction with PAS 128:2022. This guidance is provided as an open and free-to-use document, information is provided in good faith. No survey accuracy is guaranteed, implied or given. Users should always refer to the full PAS 128 specification for clarification where necessary. While there is an extensive client guide (Annex B) within PAS 128, it is recognised that many clients may wish to incorporate elements of the PAS 128 specification within their own tender and specification documents.

It is recommended that clients familiarise themselves with the Secure Data Management for Utility Surveys best practice guidance and guidance notes from The Survey Association which will help when tendering.