Q: What are the most critical aspects to consider in heavy industrial/commercial demolition practices? A: Timing, safety and health are three of the most critical, and apply across all projects. Other factors are dependent on the type of demolition required and are usually identified only after a geotechnical investigation. There is, however, a general rule of thumb that can be applied to what may be needed in terms of skills and equipment: plant-heavy sites lend themselves to fewer people and a large number of machines; or the opposite, where there are hardly any machines but a large proportion of personnel. There is no one-size-fits-all formula or approach.
Q: Are SA safety procedures up to par? A: The most successful demolition projects are those that follow global best practice. Unfortunately, this is not the rule in SA, or the rest of the continent. Currently, the market has a diverse group of demolition companies, most responding to tenders that specify a hierarchy of needs. Unfortunately, when the lowest price is the foremost requirement, it is quality and safety that are the trade-off. It’s pretty much left up to the individual companies to take care of their safety procedures.
In my mind, safety is a non-negotiable factor, which is why Jet Demolition has its own integrated safety-management programme. We have also opted for an annual audit of our safety systems by NOSA. Our performance level of 98.14% is regarded as among the highest internationally in the commercial construction industry.
Q: What role does the support structure play? A: Building contractors build from the ground up, from laying foundations to erecting support columns and secondary supports, all of which work towards the highest and most dangerous point. They therefore have some level of security in knowing exactly what the support structure looks like. Demolition contractors don’t have this luxury. With the majority of demolition projects, you’re working from the most dangerous or difficult point of a structure down, towards a point of safety on the ground. This obviously requires finite consideration of all the factors that will ensure a safe demolition, particularly if the structure is in close proximity to buildings.
Q: The Bank of Lisbon implosion in Johannesburg, which you undertook late last year, is considered a textbook example. What were the challenges? A: The Bank of Lisbon demolition was the seventh-tallest concrete-framed structure ever imploded globally. It presented some of the most challenging on-site conditions we’ve ever worked in. There were no structural drawings available, so we had to physically determine the make-up of the building. We had to locate electricity, water and fibre-optic cabling and ensure they would be protected during the implosion.
Our geotechnical investigation, resulting in our designing and installing lateral support to the basement retaining walls, was to ensure their stability during and after demolition. As the main building columns tapered from the bottom to the top, we undertook a detailed assessment of the column size and rebar strength at all points. And with the nearest building just 7.8m away, we also had to account for the very tight constraints of the surroundings. This translated into our using more than 60 000 m2 of geotextile fabric and 1 600 rolls of diamond-mesh fencing to contain the blast and curtain the explosion. We used 914 kg of conventional mining and civil engineering explosive with 2 363 separate charges, which were timed individually and sequenced perfectly in accordance with our implosion design. It took a year to ready the historic 108m-high, 31-storey building for demolition and just eight seconds to bring it down.
Q: What is the value of mechanisation in demolition practices? A: Mechanisation has removed the direct physical interface between personnel and demolition work actions. It reduces man hours substantially and improves the safety profile of the project dramatically. There’s also a reduction in costs for clients, because multiple contractors are replaced by a single service provider, and activities can therefore be undertaken simultaneously. However, specialised demolition equipment, such as we use, is not available in SA. Also, it should be replaced on a 6 000 hour basis. Certainly this is the policy we apply to ensure we contribute to safe, reliable and efficient outcomes of demolition projects.
Q: What regulatory or compliance representatives are needed on-site? A: The regulatory environment is wholly dependent on the scope of work to be undertaken and may include one or multiple traffic authorities; SAPS; consulting service providers, inclusive of engineers; legal representatives; the Department of Water Affairs and Forestry; heritage societies; individual town planners and municipalities; and even the National Nuclear Regulator. The latter is crucial when demolition experts are required, if they are certified as Jet Demolition is, to be able to handle hazardous materials, such as the radioactive decontamination of contaminated steel, concrete and asbestos. When emergency demolition is required, such as in the case of a bridge where safety has been compromised, turnkey rapid demolition solutions must account for public safety above all costs.