Contractors World UK & Ireland Vol 3 No 6 - page 22

Too tall to demolish with
conventional machinery
“It was too tall to demolish with conventional
machinery and the alternative of manually
dismantling it piece by piece would have
necessitated operatives working at height
for extended periods of time. The health and
safety risks associated with such a labour
intensive option were simply unacceptable.
The fact that the 4,000 tonne tower has
been in operational service for many years
added to concerns.
“We knew that the controlled use of
explosives was the safest way forward but
the fact that the tower had been the produc-
tion centre for ammonium nitrate fertiliser
prills created an added
hurdle to overcome.
“Ammonium nitrate
can itself, under certain
conditions, become an
energetic substance
and hence has a
potential to explode.
If such a chem-
ical residue was to
be subjected to either
significant impact –
as would be experi-
enced when the tower
hit the ground during
the demolition process
– or was to come into contact with a heat
source, there was a risk of secondary deto-
nation and explosion.
“We, therefore, needed to eradicate any
potential risks posed by the presence of
ammonium nitrate, before a decision could
be made.”
This was done by:
• Taking samples from the structure and
surrounding floor slabs to assess the
degree of contamination
• Holding joint consultations between RVA’s
explosives engineers and recognised
experts to advise both in the properties
of ammonium nitrate and theoretical
explosives
• Leading a series of hazard study
workshops so that each party had a
complete understanding of the issues
involved and could bring together
their specialist skills and knowledge to
mitigate any remaining risks.
Page 22
Contractors World - UK & Ireland Vol 3 No 6
Unlike building demolition, industrial works
pose their own dangers through chemicals and
hazardous materials.
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