Southport Gasholders
- Project Type
- Demolition of 3 No. Gasholders in Southport, Cheshire
- Client
- National Grid Properties Ltd
- Value
- £1,870,000
- Contract Period
- Nov 2008 - Jun 2009
- Services
-
- Decontamination and Demolition
Description
The site in Canning St, Southport is a live National Grid gas pumping station. On it were three gasholders: one four lift spiral guided above ground holder, one three lift below ground spiral guided holder and one MAN rigid gasholder. The above ground holder was 56 metres in diameter, the below ground 47metres and the MAN holder 90 metres tall and 50 metres in diameter.
The site still contains live gas facilities and is surrounded by industrial and commercial units. Local interest was high as the tall MAN holder had become a local landmark and a regular nesting point for peregrine falcons. Close liaison with all parties was absolutely essential.
At tender stage, our bid was considered on quality, price, experience and proposed method. Our submission, whilst not the cheapest price once again, was successful taking into account the system operated by National Grid that enabled us to obtain the highest score of all the tenderers.
The work involved the disposal of contaminated water, sealing oils, hazardous sludge and the demolition of the three holders.
The water treatment and removal was complicated by the reduced pumping levels set by the utility provider, which meant that a system of back pumping from holder to holder had to be instigated to ensure the offsite thresholds were not exceeded and the programme achieved. In all over 8 million gallons of water was treated and removed off site, with 100 tonnes of hazardous sludge.
The rigid MAN gasholder is particularly significant. This type of holder works using a floating piston inside the main structure. Using oil and tar sealing systems, this floating piston-type gasholder operates within a fixed tank construction for the dry storage of gases in restricted sites, due to its low foundation cost, small footprint and constant working pressure. The construction of it is such that its strength is gained from the total structure itself. Demolition is therefore extremely sensitive. On an open and redundant site, these structures can be simply blown down with explosives. On this live and constricted site it is impossible. It has to be demolished working off the raised piston, from the inside, top to bottom. The highest degree of engineering expertise and care is therefore required. To assist with the removal of the scrap steel, the largest crawler crane in the UK, with a height of 100m and a reach of 70 metres, is required to ensure the whole structure can be reached.
