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The Coleman Group - Demolition contractor and associated services
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19 Jul 2019
The next step for Sale’s gasholder in Manchester
Intro to the project

After an extensive and rigorous risk and environmental assessment, a now defunct gasholder located in Sale, Greater Manchester has begun to be dismantled. The Coleman group have undertaken this challenging task in removing this gasholder which was built in 1945 and was simply named “Gasholder No.5”.

Project Manager, Andy Crawford is spearheading the operation with fellow colleagues Chris Mann, Jemima Wong and Paul Cuthbert with work having started on the site in May 2019 and is expected to be completed in September.

The gasholder in question is an above ground tank, 46.5m in diameter and 9.9m high. Over the years since it was made redundant the gasholder compound has been flooded which has made accessing the top of the holder impossible.

The Site Challenges

Explaining some of the challenges that the team has encountered on site is Chris Mann, Site Manager and he said:
“This job is much more high risk than other projects I’ve previously worked on, as we are working next to a live gas main and other buildings in the area. The big problem that we have is groundwater flooding the site which is being pumped and treated 24/7 in order to maintain safe access to the gas holder.

“The next stage in this project is that we’ll have to remove all the sludge from the tank, while protecting the gas main leading in to the site. Our job now is to give access to the environmental company who’ll be cleaning the tank out for us.

Chris explains that the plan is to cut a series of holes through all the skins of the gasholder to give the environmental company safe access in to the tank to remove hazardous materials (following all the safety procedures involved) with confined space emergency exits. Scaffolders will also put up structures for further safer access to the site.

He adds:
“The stairs that lead up to the gasholder will be removed and we’ll cut a bigger hole through the skin once again which will be done by a machine. This will give us a bigger opening in to the tank for any plant machinery that need to go in, obviously we’ll have to leave the outside skin up to stop water getting in to flood it all again but also to stop anything coming out.”

The Environmental Challenges

Dismantling the gasholder hasn’t been without its environmental challenges, Jemima Wong, Environmental Manager explains:
“These are the first gasholders where I’ve been in the health and safety lead. It’s been a big learning curve for me personally but this particular gasholder has actually got quite a few environmental constraints.

"We’ve had an issue with newts found on site as some species are protected and invasive plants such as Himalayan Balsam and Japanese Knotweed then there’s also the issue with the floodwater.”

Concerning the health and safety of the workers on site, Jemima has set up QR codes that can be found around the site, they are scanned with an app on a smartphone and can provide a quick reference to a method statement or risk assessment for the task workers are undertaking.

“To get the hazardous material from inside the gasholder, our environmental contractor will use a remote controlled robot dozer to move the sludge that’s in the bottom and push it towards the suction pipe of the disab, this reduces man entry and the risk for anyone to be injured.”

Jemima then explained what will happen to all the materials when the job is done. She said:
“Scrap from the demolition of the gasholder will be recycled and general waste will go to a waste transfer station where it’ll be segregated and recycled depending on the waste.

“All the water being pumped out of the gasholder (12 litres per second) is treated on site by a carbon filter and then discharged to foul sewer under consent from the water authority. Hazardous waste such as the sludge and oil are sent to be treated and recycled or disposed of as necessary.”

History behind the structure

In the 200 years that the UK has been using gas power, gas holders were used to store coal gas (town gas) and later natural gas for the UK's urban areas (such as Sale and Manchester) but now many are becoming obsolete.

After natural gas was discovered in the North Sea in 1965 the UK gas network went through a massive process of conversion. Town gas stopped being used and North Sea gas started to be transported into the UK under high pressure in pipes.

From then on, it was only when extra capacity was needed in the gas network that gas holders would be used. As the network of pipelines became larger and more effective, these occasions became fewer.

By the 1990s, most local gas networks were able to function at full capacity without the use of gas holders. The National Grid at the time owned over 500 gas holders and with even more being owned by other companies.

In 1999, the decision was made to start demolishing them. Now, with property prices at record highs in much of the UK, the National Grid and others have started to use the professional services of The Coleman Group to start dismantling them and sell the land off.