Severn Tunnel Pumping Station Control System Upgrade

User Requirement

The Severn Tunnel links south Gloucestershire in the west of England to Monmouthshire in south Wales under the estuary of the River Severn (

The tunnel has 5 pumping shafts; 4 for track drainage and one for the great spring which leaks up to 35 million gallons of water per day into the tunnel. The control system has to pump water non-stop for 365 days of the year.

The user requirement was to upgrade the obsolete PLC control system with a modern solution where a single point of failure will not stop any of the systems.

It was also a requirement that the system was to be installed without any impact of the pumping or tunnel ventilation systems.


The Solution

The old system consisted of four Siemens Step 5 PLCs located at various locations around the site, interconnected with an L2 network.

The system was upgraded to a high availability system using standard Siemens S7 1500 PLCs & Westermo network switches.

A total of thirteen PLCs were implemented, twelve of which were in groups of two configured as a master / standby configuration the give redundancy in the event of a PLC failure.

The network switches were configured to give a total of four RSTP rings.

The top end visualisation consisted of seven Wonderware InTouch workstations located around the site.

The Results

Whilst there were no cost benefits of this project, the efficiency of the day to day running of the site significantly improved. This included:


  • Extensive alarms highlighting any problems
  • Robust backup system to ensure the site operation continued whilst problems were being rectified

Adbro Controls Limited

Unit 6 Red Shute Hill Industrial Estate

Red Shute Hill




RG18 9QL