National Grid Bolton gas holder demolition

Execution and key achievements

The gas holder was successfully dewatered and desludged before structural demolition
The steel roof and inner three steel walls were cut into sections and recycled
All work completed safely with no incidents
By working closely with stakeholders, there was minimal disruption to site work
Maintained strict PPE, site access, work permits and toolbox talks

Working with National Grid

National Grid is a multinational energy company, focused on cleaner energy by investing in electricity networks and emerging technologies.

Veolia was appointed to safely undertake the demolition and infilling of the below-ground gas holder for future redevelopment. The holder was flooded with 1,200 cubic metres of water, above a thick layer of sludge. This required dewatering and desludging by a subcontractor prior to any demolition works.

Heavy machinery working on demolishing a gas holder at National Grid

Project highlights

Supporting the energy sector

Partnership with National Grid in Bolton

Total project costing £1M+

Executed over 16 months

How we demolished the gas holder and overcame challenges

The demolition works included the removal of the steel roof, the central masonry pier, the existing redundant gas pipes and three internal steel walls. The backfill material was a specified mix, primarily consisting of 6A material for drainage, compacted shale clay and 2A grade stone with 0.10 metres of 20mm cobbles on top to match the existing ground of the site.

_{^{Demolition challenges}}

There was a sensitive retaining wall on the southern boundary in close proximity to the gasholder and a public road. We closely monitored the vibration with action thresholds set at 2.5 mm/s and 5 mm/s and tilt monitors. A no-vibration drum was used for the 13-tonne roller to protect the wall.

An adjacent Cadent Gas pressure reduction system requiring 24-hour access. We coordinated closely with Cadent Gas to schedule site visits at appropriate times, with no plant or wagon movement ensuring safe, uninterrupted access.

_{^{Dewatering challenges}}

During the dewatering process, the pump could not reach the bottom of the holder to fully dewater it. We placed the pump between the inner metal walls, to reach the bottom of the gas holder. For the last 0.5 metres of water, we brought in a 6 foot 5 bulk import to create an access ramp for plant operations.

We installed two access scaffolding, one for main use and emergencies within the gas holder. All workers were equipped with a gas monitor and signal to alert any dangerous gas levels, keeping workers and the air quality safe. An evacuation drill was timed to ensure any workers within the gas holder could safely leave within a reasonable time.