As we can see from the November 2008 article,
"Construction Blasting Fundamentals,"
there are many forms of risk associated with blasting work. It is clear that,
despite these risks, experience reveals that blasting can be performed without
incident, when adequate risk-control measures are used to manage the work.
Liberty Mutual Group
To ensure safe blasting procedures, it is very critical to understand the
terminology used in the specifications. As a general rule of thumb:
The "blast site" is the area where explosive material is handled during
loading, including an area extending at least 50 feet in all directions.
The "blast area" is the entire zone that may be affected in any way by the
Every blasting operation must have a "Blaster-in-Charge" (BIC). This individual
has overall responsibility for all aspects of the blasting operations. Prior
to any blasting, the general and site-specific blasting hazards and environmental
impacts must be defined for each blast site. Blasting plans and procedures must
incorporate all reasonable measures necessary to eliminate negative impacts
on persons, property, and the environment.
Explosive storage on-site should be limited as much as possible, but if this
is necessary, then all federal, state, and local regulations governing explosive
storage must be followed.
In blasting design there are generally two major considerations: safety concerns
and operational concerns. Safety concerns should always come first.
Before blasting, the Blaster-in-Charge should assemble all blast crew personnel
to review the blast area security plan and blast emergency plan. The blast area
is the area in which there is any potential for flying material, air over-pressure,
or gases from an explosion to cause injury to persons. The Blaster-in-Charge
should cover the following issues:
Acknowledge the shot is properly loaded, hooked up, secured, and ready
Review the blast firing time schedule.
Review the direction of the blast movement, and define the blast area
for security purposes.
The Blaster-in-Charge should specify who should fire the shot and define
the safe shot initiation location.
Review the communication system that should be used between the Blaster-in-Charge
and all blast area security personnel.
Specify what signals should be used to announce:
Outline general emergency plans that should be used in case of an accident
or other unplanned event.
Review procedures for handling misfires.
Confirm all warning signs have been posted
The Blaster-in-Charge should coordinate blasts, with all concerned parties,
on an approved schedule. To do so, clearing and guarding procedures must be
set, communicated, maintained, and evaluated.
A safe area around the shot area should be determined and cleared. Guards
should be assigned to secure all possible entryways into the blast area.
The Blaster-in-Charge should be in constant radio communication with
all personnel during the clearing and guarding operation.
When all guards confirm that the area is secure, the Blaster-in-Charge
should connect the primary initiation device 5 minutes before the scheduled
The 5-minute blast warning signal should then be sounded.
Four minutes later, the 1-minute blast warning signal should be sounded.
At blast time, the Blaster-in-Charge should fire or instruct the designated
shot-firer to fire the blast.
After the post-blast fumes have dissipated to safe levels, the Blaster-in-Charge
should inspect the shot area. During the examination the blaster should
All misfires should be safely removed, and other hazardous condition
corrected or secured.
When the area is clear of hazards to nearby traffic, the public, or the
job site personnel, the Blaster-in-Charge should give the all-clear signal
and relieve the guards from their posts.
An approved lightning detector should be used to monitor approaching
electric storms. All precautions should be taken in the event of a storm.
When blasting misfires occur—or are suspected—the misfire procedures plan
should be initiated. The Blaster-in-Charge should determine the affected area.
No one is to enter this area for at least 30 minutes.
Only the minimum required people should enter the area to safely re-fire,
wash out, or recover unshot explosives.
Record the location of any potentially undetonated explosives on the
Expand the blast security area if flyrock potential is increased when
misfires are re-blasted.
The elements of specific blast emergency plans should vary based on the unique
site conditions. The plan as a minimum should include the following.
Post all emergency response telephone numbers, including medical response,
OSHA, MSHA, fire department, police, state regulatory authorities, home
phone numbers of all site supervisors and workers.
Plan should be clearly communicated and understood by all personnel.
Define notification procedures and their timing.
Identify location of first-aid kits and identify first-aid providers.
Individual blast reports should be prepared for each blast. Blast reports
should include the following.
Blast date, time, and location
Weather end environmental conditions, such as wind speed and direction.
Blast geometry: hole size(s), hole depth, drill pattern, number of holes,
bench height, and sub-drilling.
Blast hole loading summaries: typical hole loads, explosive types, primers,
detonator delays, stemming type and quantity, as well as total explosive
Shot volume and powder factor calculations.
Initiation timing schemes: in-hole delays, surface delays, and planned
hole firing times.
Blast effect monitoring data (such as ground vibration levels, air-over-pressure
Notes about blasting results.
Name and signature of blaster-in-charge.
Risk management in blasting work is increasingly becoming more challenging
as work inevitably occurs in more populated areas. Not only is the work closer
to people and structures, but concern about blasting effects on animals and
utilities are also increasing. Sometimes it is possible to use mechanical methods
to excavate rock, but these are slower, costly, and may still have vibration
issues. Regardless of the scale of the blasting work, sometimes engineers and
contractors underestimate the importance of preparing blasting controls and
public relations programs. The consequences of this are often severe.
The public's perception of blasting has been forged from scenes in movies
like Die Hard and
Apocalypse Now. People do not want blasting
occurring, or explosives stored, near their homes. Some recent tragedies with
explosives have created genuine fear amongst the general public. In light of
these liabilities and public relation issues, it is imperative to ensure that
the blasting plan is as foolproof as possible, and the public informed about
the work planned for the site and educated about blasting, its effects, and
the controls put in place for everyone's protection.
For most projects, engineers develop blasting specifications designed to
ensure that blasting is done safely and in conformance with project requirements.
The quality and thoroughness of the specifications can greatly affect the outcome
of the project. In most cases, risk is transferred by contract clauses, but
in some serious cases, owners and others have become embroiled in legal action
and have ended up with financial losses.
Contractors and blasters usually understand the risk associated with the
work. Occasional accidents and incidents, such as flyrock and premature detonation,
are the result when blasters do not employ adequate blast design and control
practices. Along with these well-known risks, there are secondary risks such
as vibration and air overpressure that result from blasting operations. Other
issues that may have some impact may involve explosives storage and transportation.
Engineers and planners can use the following approach to manage blasting
risk. First, ensure that the project design is practical. Second, define prequalification
requirements for the contractors who are to bid on the project. Third, develop
specifications that clearly define performance and safety requirements for the
work. Fourth, ensure that the work is overseen by capable personnel.
Safe blasting requires four basic elements:
Unless property is damaged by flyrock, most claims of damage caused by vibration
and air overpressure are "perceived" damage claims, where observed damage may
have been caused by other conditions such as settlement, poor construction,
weathering, differential temperature, and humidity.
All blasting projects—large or small—occurring near any concerned neighbors,
require some level of public relations work. The level of this public relations
(PR) work is a function of the blasting duration, timing, and the level of concern
by the neighbors. Engineers and designers understand that it is unlikely that
the planned blasting will cause any real injuries to the neighbors or damage
their property. Because of this belief, it is sometime hard for them to become
enthused about PR work. The neighbors, however, have a different impression
of explosives, which is gained from popular TV, movies, and well-publicized
accidents or disasters. So, ignoring the public is to invite potential delays
and eventually costly legal action.
Generally the neighbors' areas of concern fall into three categories:
It is usually a good idea to hire a competent public relations firm to handle
the PR issues as they relate to the project. The activities include:
Pre-blast surveys are an extremely important tool for prevention of blasting
complaints and subsequent damage claims. In many cases, pre-blast surveys lower
the project liability risk, as well as serve as a venue to educate the neighboring
public. A professionally performed survey also will influence the attitude of
the adjoining property owners. Depending on the project, the area surveyed can
be as close as 300 feet or half a mile and greater.
Pre-blast reports should include written notes, photographs, or video, and
in some cases, diagrams and measurements to classify existing conditions. Settlement
surveys by independent firms may also be necessary. The surveyors should be
given some PR training so that they may effectively start the public education
It is important to understand that risk management starts well before the
blaster shows up for work on the project. Engineers and planners must ensure
that the project design is practical. The contractors are prequalified to ensure
that they are capable to successfully perform the work. The specifications must
clearly define the performance and safety requirements of the work. And that
the work is overseen by qualified and capable construction personnel at all
Note: Safe blasting procedures and risk
management are discussed in "Construction
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