BAM Nuttall, Morgan Sindall, Balfour Beatty Group, Ferrovial Agroman UK and Laing O'Rourke Construction
Civil Engineering
Permit to Dig, PAS128 Utility Survey


Tideway is one of the largest and most ambitious civil engineering projects in Europe. It aims to construct a 25km tunnel under London’s river that will prevent the tens of millions of tonnes of pollution that currently pollute the River Thames every year. The overall cost of the project is approximately £4.2 billion.

This necessary expansion of London’s sewer network is due for completion in 2024, and is being carried out across 24 construction sites in London.

The construction in the West region will be delivered by a joint venture of BAM Nuttall Ltd, Morgan Sindall Plc and Balfour Beatty Group Ltd (BMB). This contract is known as Tideway West with work taking from Acton to Fulham.

The construction in the Central region will be delivered by a joint venture of Ferrovial Agroman UK Ltd and Laing O’Rourke Construction (FLO). This contract is known as Tideway Central with work taking place from Fulham to Blackfriars.

Vision Survey was chosen to manage the permit to dig particulars for the West and Central Section of the projects, based out of the main Kirtling Street site where the two Tunnel Boring Machines were housed at the time of writing.

Vision are utilising the below methods to successfully manage the permit process with minimal issues:

PAS128 Utility Surveys

Vision’s utility department is currently undertaking PAS128 Utility surveys for all eight sites in the Central Sections as instructed by FLO.

The PAS128 survey consists of two parts:

EML (Electro Magnetic Location) Survey

An EML survey will detect buried utility services via handheld receivers using Electromagnet and radio frequencies.

GPR (Ground Penetrating Radar) Survey

This involves scanning the surface area with a transmitter/antenna utilising a hand driven system.

By incorporating both these methods and adhering to the PAS128 specification the identification of the utility service is achieved through a combination of onsite interpretation, in-house post-processing of the GPR data, along with on-site reconnaissance and historical records.

Once the on-site survey is complete Vision processes the GPR data and incorporates this with the EML data into an AutoCAD drawing, providing Fusion with a compliant utility service drawing.

Permit to Dig Control

Permit to Dig directly links to health and safety by avoiding service strikes by eliminating the risk of hitting buried services when excavating.

Using the information gathered through the PAS128 surveys we are able to define where specific underground services are located. This can be passed on to the excavation teams in the form of a “Permit to dig”. No digging can commence until it is signed off as safe to do so by Vision staff.

Video Case Study

Be sure to check out the latest update video below to see exactly how Vision Survey is involved in one of the largest civil engineering projects in Europe.