FOR such explosive results, it is a very delicate operation.
Final preparations are being made for the demolition of the twin cooling towers at Tinsley in the early hours of Sunday.
The job has to be spot on because the Tinsley viaduct, carrying the M1 and A631 on separate raised carriageways, is only 12 me
tres away.
Get it wrong and the damage to the viaduct and motorway could be disastrous, both from a structural and financial point of view.
Already 1,250 holes have been drilled into each of the 3,500 ton concrete towers ready for the explosives.
On Sunday morning – the estimate is around 3am – there will be two separate demolitions.
First will come the detonation of the south tower and then, after two seconds, the detonation of the north tower. The slight delay is to mitigate the ground vibration caused as the structures collapse.
Initial charges will destroy the legs of the towers on the side furthest away from the viaduct, causing the structures to start leaning away from the bridge. Milliseconds later further charges will be set off in the tower shell almost immediately above the failing legs.
Then charges will be set off in the shell of the tower nearest the viaduct.
The overall effect is to ensure the towers fall away from the viaduct before collapsing down and in on themselves, leaving little spoil outside of the blast site.
Demolition contractors are Robinson and Birdsell and the explosive used will be Nitroglycerine, which is preferred for its precise destructive qualities.
The actual detonation will be started by a non-electrical firing line connected to the detonation cord. The name of the person who will start the countdown will be announced today, the winner of a text competition.
Less certain is how many people will turn up to see a Sheffield landmark disappear in clouds of dust.
Those who do should head for the Meadowhall car parks where viewing platforms are being offered free of charge.
Restaurants at Meadowhall will be open until 11pm and there may be some catering into the early hours for the benefit of demolition-watchers. Toilets will be open.
Meadowhall managers are pointing out that the shopping centre will be open as normal on the Saturday, Sunday and Bank Holiday Monday.
Roads will be disrupted, though. The Government's Highways Agency is closing the M1 between Junctions 32 and 35 from around midnight on Saturday/Sunday and it is expected to remain closed for most of Bank Holiday Sunday. The A631 Tinsley viaduct lower deck will also be closed.
Drivers heading north are being advised to leave the M1 at J32, join the M18 northbound and the M62 westbound, rejoining the M1 at J42. The reverse route is recommended for drivers travelling south.
But it's the end of the road for the 250ft towers, once part of Blackburn Meadows power station, which have been a landmark for around 70 years.
Their owners, power firm E.ON, say they are structurally unsound. They are planning to redevelop land next to the viaduct as a biomass power station, generating renewable energy for around 40,000 homes.
The company is compensating for the loss of the landmark by financing a piece of public art elsewhere in the city.
But the long-running intention of blowing up the towers – delayed until E.ON and the authorities were satisfied with the demolition operation – has generated a storm of protest.
Tom Keeley, aged 25, was the co-organiser of a campaign to save the towers and have them converted into works of arts.
He left Sheffield in April this year, along with fellow co-organiser Tom James. Tom Keeley has gone to London and Tom James to Beijing.
Tom Keeley said: "I don't feel angry about it any more. But it seems that good ideas can't happen in Sheffield on the scale that we would like them to happen.
"Their fate has been sealed and they are going to be martyred soon. There are a lot of people in the city to whom the towers mean so much. They have grown up with them.
"People will remember them for a long time after they are gone."
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