3... 2... 1... FIRE!
And in just 14 seconds, about the same amount of time that
it will take you to read this paragraph, a six-story reinforced concrete
building in East Pennsboro Township was reduced to a pile of rubble. The old
making way for the new.
The implosion was swift and precisely executed by MECO
Demolition Inc. and Pettigrew Inc, both of Bensalem, PA. But the successful
result was only made possible because of the work that went into preparing the
site for those 14 seconds. It may seem like a simple process. Just set some charges,
push a button, and BOOM. Actually, much advance planning was done, focusing on
public health and safety, protecting the integrity of the surrounding
buildings, and cleanup afterwards.
The process began last year when gutting the building of all
non-structural materials began. Furniture, lighting and plumbing fixtures,
doors, floor and ceiling tiles, heating and air conditioning equipment, etc.
were all removed. This preparation allows the resulting rubble to be not much
more than a pile of concrete and steel re-bar, which will be recycled into
other materials and used for other construction projects.
In September, a pre-demolition asbestos inspection was
performed by Indoor Environmental Concepts of New Jersey. Asbestos is a
naturally occurring mineral that due to its wear resistance and fire retardant
properties was used in many applications prior to the 1970s. Floor tiles from
four locations were determined to be asbestos containing material and removed
from the building. All other materials sampled were reported as none detected.
The Department of Environmental Protection (DEP) had several
roles in the implosion. First was to ensure that environmental impacts to the
air and the surrounding area are minimized or eliminated. DEP air quality staff
performed a site evaluation to review the completion of the asbestos removal
prior to implosion, and to scan the premises for any other materials that while
not necessarily hazardous, might be better removed than left in place during
DEP mining staff issued a blasting activity permit. The
permit spelled out the terms that must be met to comply with state regulations
for vibration, noise, and public notifications.
The implosion did produce a cloud of dust. Dust is an
unpreventable by-product of the demolition process. In conventional demolition,
dust is slowly released over a period of several weeks. The surrounding area
cannot be adequately protected from dust infiltration. During an implosion, the
same quantity of dust is released over a vastly shorter period, making it
easier to control, and making cleanup much more practical.
The implosion produced a 14-second impact event with safe
and tolerable vibration levels which were monitored at five locations surrounding
the site. Ground vibrations resulting from collapsing a structure with
explosives is equal to or less than the impact of the repeated slamming of a
7,000-pound wrecking ball. The vibrations were expected to be five times lower
than acceptable federal and state standards.
So, now that the building has been demolished, the next
steps in the redevelopment process will begin. The material will be recycled
and reused. The site will be cleared and new structures will be constructed.
The past made way for the future. And it all happened in just 14 seconds.