Demolition of Noida twin towers will leave behind 35,000 cubic metres of debris

Supertech's illegal twin towers in Noida, which are taller than Delhi's Qutub Minar, will become India's highest structures ever to be demolished on August 28.
The buildings measuring a little over 100 metres will literally collapse like a house of cards in a process that would take less than 15 seconds for them to come down, according to project officials.
The demolition would be done through a controlled implosion technique for which over 3,700 kg of explosive will be used in the eye-popping event that would also leave behind a whopping 55,000 tonnes of debris to be managed.
Mumbai-based Edifice Engineering along with their South African partner firm Jet Demolitions is carrying out the job, which is certain to make it into civil engineering feats of the world.
"It will take nine to 10 seconds for all the explosives to blast in a series making a loud noise. After the blasts, the structures won't come down all at once and would take four to five seconds to come down completely," Edifice Engineering partner Utkarsh Mehta told PTI.
"The time for dust dissipation is estimated to be 10 minutes," said Mehta, whose company has previously executed demolition of illegal residential complexes in Kerala's Maradu, Telangana's secretariat and central prison, and old Motera stadium in Gujarat, among others.
Project officials said the explosives used for demolition include detonators, emulsions and shock tubes, which have explosion material in gel or powdered form.
"These explosives are not very strong in nature but when used in large quantities, they are able to break concrete. These explosives are sold in a regulated manner and strictly after permission from various government agencies," an official said.
The demolition of Supertech's twin towers in Noida's Sector 93A comes in pursuance of a Supreme Court order that found the structures to be illegal and built in violation of norms.
According to the estimates prepared by the project officials, the demolition of the Apex (32 storeys) and Cyane (29 storeys) would leave behind approximately 35,000 cubic metres of debris to be cleared and clouds of dust to dissipate.
Noida Authority's General Manager (Planning) Ishtiaq Ahmed said 21,000 cubic metres of the debris would be moved out and dumped at an isolated land measuring five to six hectares in city's work circle seven limits and the remaining would get accommodated in the basement areas of the twin towers where a pit has been made.
"The post demolition debris would be managed scientifically as per rules and guidelines. A final decision on it would come from the regional pollution control board which is examining a report from Edifice Engineering on debris management," Ahmed told PTI.
According to Mehta, around 1,200 to 1,300 "truck-loads" of debris would have to be moved out from the site.
"However, there has been one good thing of late. The Jet Demolitions team has been tracking the flow of the wind for the last one week or so and found it flowing towards the West. If the same pattern continues, then most of the dust would blow towards the front side of the twin towers, a road followed by an open city park," he said.
The favourable wind direction would prevent the dust from settling within the premises of Emerald Court and ATS Village societies – both in close proximity to the twin towers.
Though, all the debris will not go to waste as it will yield an estimated 4,000 tonnes of iron and steel that Edifice plans to use to recover a part of the demolition cost.
Meanwhile, the Noida Authority has a construction and demolition waste management plant in Sector 80, with a capacity of 300 tonnes per day.
However, considering the rubble that would be moved out, it is still not clear whether it would be processed there and if yes, then how and over what duration of time.
According to project details, the Apex tower has 11 primary blast floors -- where all columns on the floor will have explosives fixed and blasted -- and seven secondary floors -- where 60 per cent of the columns will be blasted.
Cyane has one less primary blast floor.
The charged columns are wrapped in wired mesh and geotextile cloth to prevent debris from flying and damaging nearby buildings.
There will be six layers each for floors between the basement and sixth floors and four layers each on the upper floors, according to the details.
For the protection of Emerald Court and ATS Village, both societies will also have geotextile covering.
About 225 tonnes of wired mesh made of galvanised iron and geotextile in 110-km length would be used in the entire process.