Engineering Excellence: safely maintaining our network

22 May 2024

Every year, we carry out hundreds of projects to keep the communities we work in safe and warm. Mike Dongworth is our Engineering Manager for Southern Maintenance Projects, who were recently involved in removing large pipes from Durnsford Bridge in Wimbledon.

Here’s Mike’s story of how the project came about.

Our Project Team is responsible for a wide portfolio of work which includes:

  • Replacing our governors, which are you used to manage pressures in local networks
  • Diverting our Intermediate Pressure (IP) pipes
  • Work to decommission our gas holders
  • Inspecting and restoring our IP & High Pressure (HP) gas mains
  • Installing Access Prevention Measures on bridge crossings. This may include the removal of abandoned pipes to eliminate the risk to members of the public.

We recently completed a project to remove a 24" Cast Iron gas main at Durnsford Bridge in Wimbledon. The main was supported by steel girders spanning 280m across the bridge, going over the main railway lines running out of Clapham Junction, the UK’s busiest interchange train station.

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A metal pipeline attached to a bridge going over train lines

After being abandoned in 2017, not only was the pipeline showing signs of disrepair but it could also be easily accessed by members of the public, which raised significant safety concerns. Our team was tasked with removing the pipeline under significant financial and time constraints, so the pressure was on.

Along with my Team Manager Ian Spice, there were many challenges to overcome before the main work could start. This included getting the services of a competent Contractor and engaging with stakeholders such as Network Rail and the Highways Authority.

As always, we needed to make sure the project was carried out safely. We had to first provide Network Rail detailed method statements, safe systems of work and risk assessments. This demonstrated that we were taking all reasonable precautions to prevent material falling on to the tracks below.

We also had to ensure the safety of our trackside team when working over the railway. This required the suspension of railway services. We would normally pay Network Rail for a possession of the track during our works, which can be very costly.

However, due to our relationship with Network Rail, we had the opportunity to enter a ‘shared possession’. This is where the section of track is closed for a set period. It allows various contractors to work together to deliver track remediations and other maintenance activities. This reduced the cost to SGN significantly as we only had to pay a 6% share of the overall possession cost. 

We not only had the railway lines to consider but also a full closure of the bridge to traffic. This resulted in a large diversion for all road users including public transport. By working closely with Transport for London, we managed to implement these plans and make sure we provided plenty of notice to our customers. Without a doubt, this reduced complaints and kept the local community on our side.

There were other challenges to overcome such as the removal of an illegally built structure over the pipe.

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A small brick building with metal shutters down the front

Although this was an illegal structure (having been built without our consent) and we could rely on sections of the Gas Act 1986 and the Pipeline Safety Regulations 1996 in support of our argument to have it removed, we were met with significant legal challenges. Thanks to the help of our legal team and in particular, our Dispute Resolution Solicitor Hannah Robinson, we managed to have the structure removed before we started the main works.

Once we had overcome these challenges, we went to work on the removal of the pipe, and its supports.

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A section of pipe hanging in mid-air over a bridge at night

The project took seven weeks to complete. By working closely with our contract partner Dyer & Butler and maintaining communication with external stakeholders, the project was delivered ahead of schedule and, more importantly, safely.

This is just one of many challenging and fascinating projects delivered year after year by our team which I am proud to be a part of. 

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A bridge with a section of gas pipe capped