MC Explains | Noida Twin Tower Demolition | Explosives to be used, damage to surroundings and other questions answered

CBRI was appointed as the expert body by the Supreme Court in August 2021 and its approval is needed for the charging process to start. The queries are to do with the quantity of explosives to be used and the selection of the primary and secondary blast floors.

The responses have to be sent to CBRI before an August 6 meeting of all stakeholders including representatives from the police, Supertech and Edifice, which has been scheduled on the directions of the Supreme Court.

Edifice is also yet to receive a No Objection Certificate for use of explosives from the police. This has to be received from the Petroleum and Explosive Safety Organisation’s regional office in Agra.

 What are the explosives being used?

These would be a mix of dynamite, plastic explosives and emulsions. These explosives will be brought in installments from a PESO-authorised magazine in Palwal. No explosives will be stored on site.

The towers will be brought down by using the waterfall implosion method. They will fall inward.

The type of explosives are chosen in such a way to control the force of the blast. In the implosion technique, experts have to arrange the sequence of explosive in such a way that it goes through in a millisecond inside the building. Rooms in a building have a hollow area surrounding them. Therefore, it is only the four walls and the hollow in between that are pulled inside. The implosion does not cause the debris to expand. It gets reduced to just about 17% of the total building, demolition experts said.

The explosives in the columns of the structure will create a sharp burst of outward pressure and spread across the structure like a shockwave, shattering the concrete, resulting in the collapse of the building. The charges will generate a sound like Diwali crackers, sources at Edifice Engineering told Moneycontrol.

 How will they will be used? 

Over 3,500 kg of explosive will be filled within 9,400 holes drilled in the columns and sheers of the nearly 100-metre tall twin towers. According to reports, around 10,000 holes have been drilled from the basement to the top floors of the towers which will be charged with explosives weighing nearly 3,700 kg. The explosives for charging will be brought from Palwal, Haryana, in a regulated quantity and then be placed within the skeletal structures of the twin towers. Gautam Buddh Nagar police will provide a security escort during transporation of the explosives. The beams and pillars of the Twin Towers are also being wrapped in geotextile material to minimise the impact of the blast.

Will surrounding buildings be damaged?

Sources at Edifice Engineering told Moneycontrol that the entire demolition will take place within 9-10 seconds, which will cause a dust balloon as high as a 60-storeyed building. The company says it is prepared to save nearby buildings from the pollution that will be caused by using water jets, fire tenders and fountains. The two towers have been completely covered with black and white geotextile fibre to prevent the debris from scattering in nearby areas. Surrounding safety features, including containers in Emerald Court’s basement and filling the basement with debris, and safeguarding the gas pipelines have been put in place.

Will there be increased pollution? Has the process of clearing debris been finalized?

While the buildings will be demolished in nine seconds, it may take at least three months to remove all the accumulated debris. According to people in the know, more than 50,000 tons of debris will waterfall into the basement. For the final blast, debris will be disposed of in line with the Construction and Demolition. Waste Management Rules, 2016. The debris may be processed at a construction and demolition waste plant or disposed of in a low-lying area.

A dust cloud may take 10-15 minutes to settle depending on the wind speed. Dust and noise levels in the area are being monitored on a weekly basis, the amount of waste generated is being logged and daily water consumption is being accounted for. Dust separators have been installed on the site.

The biggest challenge of the demolition will be in containing the dust cloud, which may be difficult. The company is looking at ways to contain the vibrations by deploying impact cushions. Trenches of 4 metres have also been dug in the blast area to contain the rubble.

 What are the safeguards being taken?

On the day of the demolition, 1,396 residents will be evacuated. They would have to leave either a day before the demolition or just a few hours before the exercise begins. Sources at Edifice said buildings in the vicinity will not be damaged on account of the blast. The velocity of the ground vibrations from the implosion is expected to be 34 mm per second and with Delhi-National Capital Region being in Seismic Zone 5, buildings are designed to withstand vibrations of 300 m per second.

On July 19, 2022, Edifice Engineering submitted a vibration prediction report to the Noida Authority, which had said that the maximum vibration caused by the demolition is expected to be 34 mm per second, while the structures in Zone 5 are designed according to the norms of 300 mm per second.

What are the similarities or differences with previous such demolitions? 

The demolition exercise is similar to the one used in the demolition of multi-storey housing complexes in Maradu in Kerala in January 2020. The only difference is that the Maradu towers had almost half the storeys the Noida Twin Towers have.

In both cases, the Supreme Court ordered demolition of the properties, and in the case of Maradu, the towers had been completed and were even occupied by residents. The Maradu demolition was ordered due to violation of Coastal Regulation Zone requirements, while Supertech was found to be in violation of provisions of the UP Apartment Act. In both cases, the apex court declined to regularise the unauthorised constructions.

In the Maradu case, four buildings had to be demolished. The biggest challenge with regard to the Golden Kayaloram apartment complex was that it was located on the main road and was surrounded by schools and water bodies. For demolition of the Alpha Serene building, demolition experts had to ensure that the adjoining water body did not get polluted and that minimum debris went into the water. Machinery was used to clean the lake immediately. The H2O Holy Faith was a V shaped building and the Alpha Serene building had a hotel and small houses located in the vicinity. The Jane Coral Cove Tower was the largest with only a 2 m setback from the river.

Mumbai-based Edifices Engineering carried out the Maradu blast with the assistance of experts from South Africa-based Jet Demolition, the same as in the case of the Noida Twin Towers.

The complexes housing a total of 343 flats were brought down using the implosion method. As a precautionary measure, people living in the neighbourhood falling under the evacuation zone, within a 200 metre radius from the complexes, had been asked to move out of the area on the two days and ban orders under Section 144 of CrPC were imposed for almost eight hours.

Coastal police in boats had kept vigil along the backwaters running adjacent to the flats.

In the Maradu case, house-to-house searches were carried out for ensuring 100 percent evacuation of people residing in the zone. Residents in the evacuation zone had also been directed to switch off electricity and all appliances before leaving their homes.

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