We are entering the dawn of the terminally ill skyscrapers.
Modern multi-storey buildings started to emerge out of the landscape in the middle of 20th century. And for many of these early skyscrapers...their days are numbered.
The average US multi-storey building will last for about 73 years, according to research prepared for the US Department of Energy by Pacific Northwest National Laboratory (PNNL).
This average is generally accepted throughout the world. Though some buildings can last for about 200 years.
At the moment there are two main ways of demolishing a skyscraper...belting it down with a wrecking ball or blowing it down with explosives. Though the Japanese have developed another method which involves the building being lowered down floor by floor..( See article: http://www.wotwaste.com/waste-articles/commercial-waste/zen-buddhism-and-the-art-of-building-demolition.)
Sick and dying buildings are going to become more common and more problematic. One could say its a growth industry for engineers and demolition companies.
End of life buildings was one of the topics at the Annual Demolition Summit, held on November 6, 2009 in Amsterdam.
Martin Bjerregaard from UK engineering firm Golder Associates spoke on the challenges facing demolition and engineering companies who have to safely and economically remove these buildings.
These challenges include how to sort through, identify and handle ozone depleting CFCs (chlorofluorocarbons), asbestos, lead and PCBs (polychlorinated biphenyls).
Hazardous chemicals and materials are knitted into the fabric of these worn out buildings.
PCBs were used for aircondtioning coolants, sealants, water proofing, fluorescent lighting, adhesives, wooden floor coatings, PVC coatings and as electrical insulators. They were also used in electrical appliances such as toasters and fridges.
PCBs have been linked to liver, thyroid, stomach and skin disease; in addition to immune system and learning problems in children.
In 1976, PCB production was banned by the US. Then in 2001 the UN introduced the Stockholm Convention on Persistent Organic Pollutants which banned PCB production. Over 152 countries have signed the convention.
But it is not only PCBs and CFCs which are woven into ageing skyscrapers and high rise flats. Up until about the 1980s many of the pipes and walls were painted with lead paints. Asbestos was used in floor tiles, roofing, wall plaster, insulation and fireproofing.
And just to make the problem of building contaminants even more difficult many of these materials cannot simply be dumped into landfill.
The buildings have to be thoroughly and one would hope responsibly stripped out into a shell by demolition contractors before the building is levelled.
Painted concrete for instance has to be assessed to find out the lead concentration. If its too high it cannot be recycled into concrete aggregate.
All PCB and CFC building parts have to be carefully stripped, separated and removed. Any spillage, or escape of vapours risks worker health and contamination of other building parts.
These PCB and CFC coatings, insulators, coolants, sealants, lights, tiles and the like are then taken away to be destroyed, usually by incineration or irradiation (though sometimes ultrasound, microbes or chemicals are used for PCBs)
Quite apart from all of that, strip out specialists also remove glass, wiring, shelving, metals, built in furniture, plastics and other recyclable materials. About 50 percent of a building is recycled. With the biggest recyclables being concrete (for roads), steel, glass and copper.
But its a complicated process made more complicated by the hazardous materials inside these old buildings. And within the next 20 years that problem is going to become larger.
http://www.demolitionsummit.com/
http://www.ecy.wa.gov/programs/hwtr/index.html
http://www.wbdg.org/ccb/ARMYCOE/PWTB/pwtb_200_1_44.pdf
http://www.cecer.army.mil/techreports/ERDC-CERL_TR-07-2/ERDC-CERL_TR-07-2.pdf
