Riverlinx CJV - £710k - Apr 2020 to Dec 2020
Civil Engineering
PAS 128 Utility Survey, Permit to Dig & Drone Survey


Silvertown Quays is a redevlopment scheme of 50 acres of former  London docklands warehousing in the East London district of Silvertown. It is situated on the northside of the River Thames, the southside of the Royal Victoria Dock on the opposite quay to ExCeL exhibition centre, and immediately west of London City Airport.

The tunnel project is being delivered by RiverLinx consortium ( comprising  Aberdeen Standard Investments, BAM PPP PGGM, Cintra, Macquarie Capital and SK E&C) for the Transport for London. The contract is worth about £1 billion and includes the design of a 1.4-kilometres twin-bore road tunnel under the River Thames, as well as 0.6-kilometers of access ramps. The Silvertown project will significantly reduce congestion in and around the neighboring 122 year old Blackwall tunnel. Currently, an estimated one million hours are wasted each year queuing for the Blackwall tunnel. The new tunnel is the first major road crossing across the River Thames since the QE2 Bridge at Dartford opened in October 1991, and the project will result in a six-fold increase in public transport provision across this area of the River Thames.

Few key facts:

  • 350 000 square meters – area surveyed
  • Approx. 1800 Manholes / IC’s – number of pit schedules
  • 1.3 TB of Geophysical data

Vision Survey has been chosen by Riverlinx to assist with the enabling works by delivering the following essential services.

PAS 128 Surveys

Vision’s utility department completed a full PAS128 Utility surveys across both sides of the River.

The PAS128 Utility 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, in this rural environment we use a quad bike system, which enables us to cover a significate amount of meterage per day and accommodate the rough terrain and changing ground conditions. Alternatively, for the more restricted/narrow area’s we will utilise 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 will process the GPR data and incorporate this along with the EML data into an AutoCAD drawing, providing Fusion with a compliant utility service drawing.

Towed GPR for PAS 128 Utility Surveys

Towed GPR for PAS 128 Utility Surveys

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.

How We Went About Completing the Project

Initially we completed drone photogrammetry to get an overview of the area to help with planning and data acquisition.

Aerial Images using Drone Surveying

Aerial Images using Drone Surveying

The project was carrying out in the highest specification of Utility survey – PAS 128 in M4P methodology. We used 3D GPR methodology to maximize resolution and accuracy of Utility identifications. 3-4 teams were working parallel in the same time and they were sending the data simultaneously to the processing centre.

We worked across all the seasons in difficult environments, in all kinds of weather (rain, snow, very hot), terrain (dual carriageways, verge, pavements, rough terrain, close to deep water), days, nights, with Traffic Management, as required.

We used a GIS based application to record manhole and inspection chamber information in the field.

The data was collecting in different environments, so the preparing of the data to interpretation forced to apply advanced processing sequence with deconvolution and enhancement of the signal. During analysing and interpretation of geophysical data, Vision’s Geophysicists were finding some of the abandoned utilities and they were confirming by excavations in further stage of the Silvertown Projects. Final delivery included 3D solid model of underground infrastructure and Vision’s drawings were used for updating bigger model and GIS database.

Silvertown 3D Utility Survey Model

Silvertown 3D Utility Survey Model

Problems & Solutions

During the works we dealt with two main issues as follows:

Problem 1 – High crime level and equipment was stolen, despite having security on site.  Dog Security for PAS 128 Utility Surveys

Solution 1 – Security needed to have a greater presence to deter criminals especially during lockdown, so a K9 unit was used that had the desired effect

Problem 2 – Covid 19 lockdown delayed the start of the work.  Covid during PAS 128 Utility Survey

Solution 2  – We used a one-man team in a vehicle for the towed GPR to obtain information to process whilst people worked from home.