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PART
1: THE BIRTH OF EXPLOSIVE DEMOLITION
Black
Powder
Historians
generally agree that the first true "explosive"
was black powder, which was developed around the
13th century. The first recorded use of black
powder for demolition purposes appears to have
occurred in the early 1600s, when quarries in
Hungary began using it for rock blasting. Shortly
thereafter, black powder was put to use in the
tin mines of England, and Switzerland adopted
blasting technology for road construction.
One
of the first documented attempts to actually fell
a building with explosives occurred in 1605, when
disgruntled Englishman Guy Fawkes placed barrels
of explosive powder under the British Parliament
in an attempt to blow-up the structure and kill
King James I. Although Mr. Fawkes was apprehended
before he could detonate his explosives, the event
drew considerable attention, and 400 years later,
it is still commonly referred to throughout the
United Kingdom as "The Infamous Gunpowder
Plot."
Another
benchmark in the history of explosive demolition
occurred in 1773, when demolitionists used 150
pounds of gunpowder to raze the 700-year-old Holy
Trinity Cathedral in Waterford, Ireland. According
to a report in The Irish Times, the structure
"succumbed to a deafening boom, and was instantly
reduced to rubble."
This
appears to have been one of the first documented
attempts at a controlled "building implosion,"
although modern demolition experts point out that
the use of such a low-velocity explosive probably
caused more of a building ex-plosion.
 Explosives
Come To America
The
use of explosives to demolish structures in America
began in the early 1850s, when San Francisco was
repeatedly decimated by a series of great fires.
In a desperate attempt to limit damage from these
events, city council members approved the use
of explosives to demolish various buildings in
a fire's path in the hopes of cutting off its
fuel supply. A city ordinance ordered the appointment
of a Chief Fire Engineer, whose official responsibilities
included, "the blowing up of any building
or buildings with gunpowder which he may deem
necessary for the suppression of fire."
Not surprisingly, this radical abatement method
often met with vocal opposition from many of the
residents and merchants who lost their homes and
businesses. However from that point on, San Francisco
fire departments purchased and stored gunpowder
as a standard firefighting tool, and the city
would continue to figure prominently in explosive
demolition experimentation for years to come.
 Nitroglycerin
While
America's rock blasting and fire-fighting industries
were just beginning to capitalize on the advantages
of blasting powder, an Italian chemist named Ascanio
Sobrero was completing work on his powerful new
explosive mixture, nitroglycerine.
By
the late 1850s, nitroglycerin had established
a reputation as an extremely efficient - but volatile
- explosive.
However
several scientists, including Swedish chemist
Alfred Nobel, began experimenting with ways to
stabilize nitroglycerin by combining it with various
amounts of diatomaceous earth (also known as kieselguhr).
Nobel eventually developed a safer, more shock-resistant
form of explosive that he named dynamite.
 The
Impact of Dynamite
In
America, some of dynamite's first uses were to
create trenches for irrigation systems, to blast
rock in mines and quarries, and to remove trees
and stumps. This in turn led to larger and more
ambitious roadway projects, which helped "pave
the way" for the industrial revolution.
It
wasn't long before dynamite was being applied
to thousands of projects around the globe, including
many experimental, one-of-a-kind structural endeavours.
The full range of undertakings is far too lengthy
to list here, but among the more unusual:
*
In 1883, an engineer in Budapest, Hungary used
five small blasts to fell a 200-foot-tall, octagon-shaped
masonry chimney in one of the first recorded uses
of dynamite to demolish a structure.
*
In 1889, dynamite was used to break apart an 11-million-square
foot solid mass of debris that became wedged against
a Pennsylvania Railroad bridge as a result of
the Great Johnstown Flood.
*
In 1900, South African saboteurs packed two locomotives
with dynamite and started them towards each other
from opposite ends of a railway tunnel in an attempt
to destroy the tunnel. Although resulting explosion
demolished the engines, the structure itself suffered
little damage as most of the energy merely dissipated
back through the open entrances.
The
1900s: Critical Uses for Explosive Demolition
By
the turn of the century, the first "skyscrapers"
were being built in major cities across America,
which meant that demolitionists would eventually
be called upon to remove ever-taller structures.
On April 18, 1906, San Francisco was struck by
the most famous and devastating of its many earthquakes.
The quake killed hundreds of people, initiated
more than 50 fires, and broke hundreds of water
pipes throughout the city. This left dynamiting
as the only way to check the fire's advance. Within
hours, the Mayor of San Francisco dispatched telegrams
to surrounding communities stating simply, "Send
fire engines and dynamite, immediately."
For
four days and nights, hundreds of firefighters,
miners and military troops worked furiously to
blast entire city blocks in an attempt to choke
off the inferno. By the time the last fire was
extinguished, thousands of buildings had burned
to the ground and hundreds more had been leveled
with dynamite. But the blasting efforts were at
least partially successful and were credited with
saving large western sections of the city. In
the weeks that followed, many blasters were called
upon yet again, this time to explosively demolish
dozens of unstable, burned-out structures throughout
the region.
 The
First "Building Implosions"
Aside
from being utilized as a desperate fire-abatement
method, there gradually evolved two other primary
reasons to consider the use of explosives to bring
down structures: Worker safety and preventing
harm to adjacent liabilities. Quite often, demolition
experts found these two factors dovetailing.
To
address both issues, engineers began devising
ways to bring walls down within their own perimeter
through the use of explosives. This was usually
accomplished by one of two methods; either by
blasting one wall at a time, or by carefully pre-weakening
several of the walls and columns in tandem and
simultaneously blasting them inward.
One
such project, the demolition of Delaware, Ohio's
fire-ravaged City Hall, was profiled by consulting
engineer R.N. Van Winkle in The Explosives Engineer:
"The
building was located on the busiest corner of
the city, and utmost care was necessary in planning
its removal…The fire had weakened the structure
to such an extent that it was a menace to both
life and property, and to the business of adjacent
stores and shops.
The
95-foot-tall clock tower was the first to be shot
down. Drilling and blasting of this part of the
structure offered some very difficult problems.
While several thousand spectators watched the
blasting and falling of the main building, stack
and clock tower, not a spectator or workman was
injured and in no instance did any material fall
outside of the curb line…In exactly eleven
days the building was completely removed."
Although
at the time no descriptive name existed for felling
structures in such a controlled, inward fashion,
these projects were later credited by many industry
veterans as the first true "building implosions"
performed in the United States.
More
important, however, these early efforts were the
first to demonstrate the advantages of applying
explosive technology to emergency response operations.
Over the past century, explosives have been used
to fell structures rendered unstable by a myriad
of external forces such as fire, earthquakes,
tornadoes, sinkholes, collisions, terrorist acts
and inferior construction.
 1910-1920:
Expanding the Market
During
the century's first few decades - and with experimental
shaped explosives still in their infancy - conventional
dynamite was becoming a valuable tool for the
destruction of large industrial structures such
as smokestacks, railroad bridges and mine headframes.
Dozens of these items were blasted during this
era, and powder manufacturers gradually began
encouraging their clients to consider economics
in decisions relating to explosive demolition.
An
article written by C.B. Spicer of the Hercules
Powder Company profiled the demolition of four
heavily reinforced grain silos in St. Louis, Missouri,
and told of the savings the property owner realized
by choosing explosives over contracting for scaffolding
and manual demolition.
"The
project attracted considerable attention as an
engineering feat, (and) much favorable comment
was expressed on the use of explosives as the
controlling factor. …(Another) advantage
to dropping the silos by this method was that
the impact with the ground demolished the stacks
so completely that the debris could be conveniently
handled by a steam-shovel."
This
was one of the first documented instances wherein
the use of explosives as a catalyst for exploiting
the earth's natural gravitational-pull to facilitate
"debris breakage" was recognized as
an economic asset, and this benefit remains a
significant factor in many blasting-versus-conventional-demolition
decisions made today.
 Not
Always Perfect
Although
the industry was experiencing many successes during
this era, explosive demolition could hardly be
considered an exact science. While most projects
went well, several of the more stubborn structures
- particularly concrete silos and wide-based smokestacks
- took three or four blasts to bring down. In
fact, a few of these structures were never successfully
blasted, and eventually required the use of heavy
equipment to tip them over.
Still,
few people seemed particularly upset, as most
projects performed during this era were viewed
more as curious oddities than anything else.
 The
1930s: The Golden Age of Exploration
In
1931, the Florida Dynamite Company was hired to
raze the Central Schoolhouse in downtown Miami.
This job differed from most blasting projects,
however, in that the building showed no signs
of fire or structural damage. In fact, there was
nothing physically wrong with it. The general
contractor had merely decided - correctly as it
turned out - that spending $60.37 for dynamite,
caps and wire would be the most efficient way
to bring the building down.
Throughout
the 1930s, structural explosive demolition was
overseen by engineers working directly for large
dynamite manufacturers. Their goal was not necessarily
to implode buildings, but to find new and innovative
ways to sell more blasting products. They soon
realized that in order to use dynamite near populated
areas with consistency, they would have to limit
the effects of flying debris. So they began experimenting
with various types of "protective measures."
It
was during this era that wooden boards were first
placed in front of adjacent windows, and demolition
contractors began parking company trucks around
their projects' perimeters to shield nearby exposures.
Blasting teams also endeavored to cover the dynamite-packed
holes with whatever they had at their disposal,
which led to some creative undertakings. After
one particularly successful bridge demolition
in Germany, the project's Operations Supervisor,
Mr. William Weiss, proudly wrote in The Explosives
Engineer:
"The
stone bridge to be blasted was near occupied houses,
so the holes were covered with bundles of willow
branches, and throughout the blasting operations,
nearby buildings suffered no injury, nor were
there any accidents."
 By
the end of the decade, structural explosive demolition
was becoming less of an oddity and more of a specialized
service offering a predictable, successful result.
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