Onsite

Me and my project: Dismantling a century-old gasholder

25 August 2018

The Southall MAN gasholder towered over its environment

Careful planning and bespoke methods were key for The Coleman Group’s project manager Josh Scriven when leading a challenging project to dismantle an iconic gasholder, which towered over a London community for a century.

MAN gasholders are notoriously challenging to dismantle. Apart from the sheer size and iconic status of these historic structures, dismantling work is inevitably constrained by the environment in which they are situated. Traditional techniques often can’t be used and specialist experience is critical.

The Southall MAN gasholder – a local landmark – was 95 metres high, 60 metres in diameter and 100 years old.

There were a significant number of constraints I had to consider and plan for prior to dismantling, namely the third party, high-risk assets which surrounded the structure.

These included Network Rail Infrastructure (London Paddington lines were just 20 metres away), a live gas plant located 10 metres away, high and medium pressure below ground pipework which surrounded three sides of the structure and a Heathrow long stay car park nearby. We were also restricted to no hot works on the site.

It took months of preparation to gain approval for the works, including meetings with key stakeholders, before we could install the necessary temporary works and control measures.

Start of works

We knew we would have to use bespoke methods to dismantle the structures, working from the roof structure with mounted cranes. This would allow us to cut the roof structure and float it on a bed of controlled air before dismantling the main structure, remaining self-contained within the footprint and minimising space required around it.

Project manager Josh Scriven (right) with contracts assistant James Doherty

Careful planning, sequencing and bespoke fabrication was critical to successfully installing all temporary works on programme, making sure our cranes were mounted on the roof before the winter months.

Dismantling the MAN holder

Due to weather exposure, we then made a collaborative decision with our client National Grid Property to demobilise over the winter months to prevent risk to our workforce and delays caused by adverse weather.

Once back on site and after a detailed re-inspection of all components, the next stage was to release the roof from the gasholder to create our floating working platform and start the dismantling. The idea of floating over 500 tonnes of steelwork and using it as a working platform was daunting at first, but after installing specialist blower equipment and function testing, it is an efficient and safe process.

Even with the winter demobilisation, however, we had to carefully monitor the weather because we were lifting large panels of steelwork from great heights. Wind speeds had to be measured for every aspect of lifting and clearly displayed, briefed and monitored throughout. We mounted anemometers to the roof, linked to apps on our mobile phones.

Challenge and reward

There is no doubt this was a challenging project, involving the complex dismantling of an iconic structure under unique and significant site constraints. However, the more challenging the project, the greater the achievement both for The Coleman Group and for me personally.

I am proud to have managed a project of such complexity that will develop me further in my career whilst also delivering a best practice demonstration for the entire demolition and construction industry.

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