42
JULY-AUGUST 2013
d
&
ri
IN ACTION
A
fter almost 20 years of multi storey
demolitions, Dundee City Council
awarded their last two tower blocks
to local company Safedem. Starting in 1995,
Safedem has steadily changed the skyline of
its home town by demolishing more than 40
tower blocks across the city in this period.
At 27 storeys, the Derby Street blocks were
built in an area surrounded by sandstone
tenements with ornately carved date stones
from the 1800s.
However, it was a relatively modern
structure dating from the 1970s, St Martins
Church, that was located between the two
blocks that captured the media’s attention.
Derby Street is located in the Hilltown area
of the city - aptly named as the sloping site saw
the tower blocks built off a heavy duty podium
structure that resembled the support legs from
the nearby Tay Bridge. The slope was such that
at the east end of the structure, the 850 mm
(34 inch) thick columns were 9 m tall (29.6 ft)
- at the west end they were just 3 m (9.9 ft).
PREPPING FOR BLAST
The internal floor plan of the
structures was also highly unusual,
with maisonette style homes
spread over three floors, with
the centre of the structure offset
from the main living areas. The
maisonettes were tall and narrow
homes with heavily reinforced
concrete walls dividing the rooms
every 2.75 m (9 ft). A total of 37
heavily reinforced crosswalls at
any one level made this one of the
most rigid tower blocks Safedem has ever
encountered.
All these walls needed to be drilled so each
building had in excess of 5,000 drill holes (a
standard tower block is closer to 2,500 holes),
with each drill hole housing an individual
charge and delay detonator.
When assessing the structures and the
nearby buildings that were to remain, it was
obvious that each structure required its own
unique collapse mechanism. The north block
needed to be initiated at the
east end and directed to the
east towards the nearby main
road. The south block needed
to come straight down and
then rotate away from St
Martins, ensuring the debris
came to rest away from the
church towards a series of
4 storey buildings that also
form part of Safedem’s overall
demolition project in the area. Due to the
proximity of the church a protective screen
constructed of scaffold was erected at the
gable of the church.
The evacuation of this heavily populated
city centre location was carried out by
Safedem s Community Liaison Team.
Hundreds of residents were temporarily
evacuated and catered for in a dedicated rest
centre, ensuring the demolition could proceed
within the target time window.
On initiation, and in front
of thousands of onlookers,
the two structures dropped
as designed in a safe and
controlled manner. On
inspection of the church,
part of the 14,000 tonnes of
rubble from the north block
had come to rest against the
scaffold protection screen.
The screen had ensured there
was no structural damage to
the church, although there
was some minor damage to
a fire escape area to the rear
of the church building. This
minor damage was repaired
in the days following the
implosion.
Safedem Managing Director, William
Sinclair commented: “I was disappointed
to see the minor damage at the church
fire escape area because the standards we
set ourselves are so high. However these
were Dundee’s tallest structures and of a
truly complex and rigid construction, and
I am delighted they are safely down having
collapsed as designed.”
He continued: “This project required real
teamwork from a number of agencies and real
thanks must go to not just the hardworking
Safedem team, but also to Dundee City
Council and Police Scotland who worked with
us every step of the way to deliver another safe
and successful blowdown in Dundee.”
■
Derby
double
