Blasting and
Explosives Awareness
Guidelines drafted by the Civil Engineering Committee
have been reviewed and approved by the labour-management network
1.0 INTRODUCTION
Explosives and blasting operations are widely used on construction
projects to move underlying rock common throughout Ontario. While
the explosives are becoming more reliable and efficient, undetonated
or partially detonated charges can pose significant hazards should
they be undetected or handled incorrectly.
This document is divided into two sections outlining how workers
may come into contact with explosives and methods to eliminate
or minimize hazard exposure. The first section addresses work
sites in which qualified drilling and blasting contractors are
employed while the second section concerns work sites at which
blasting activities are not part of the contract, although the
sites included blasting activities in the past.
2.0 CONSTRUCTION ACTIVITIES AFFECTED
Employees of blasting contractors are continually exposed
to the hazards associated with the use of explosives. These workers
and their companies are required under federal and provincial
legislation to have specific procedures and practices addressing
the safe transportation and handling of explosives and associated
equipment.
Excavation crews working on sites involving blasting operations
may be exposed to the hazards of undetonated charges during removal
of blasted rock. Such excavation may be required for road building,
pipeline work, housing, commercial or industrial construction,
power plants, bridge construction, and the like.
Construction crews working on sites where blasting is not
required, but occurred in the past, may also be exposed to the
hazards of partially or undetonated explosives still active underground.
3.0 PROJECTS WITH BLASTING OPERATIONS
3.1 Responsibility of Blasting Contractor
The blasting contractor shall comply with all federal and
provincial legal requirements in connection with the use, storage,
and transportation of explosives, including the Canada Explosives
Act and the Transportation of Dangerous Goods Act.
Only workers thoroughly experienced in handling explosives
shall be permitted to supervise, handle, haul, or detonate explosives.
The blasting contractor shall follow all pertinent construction
regulations in addition to its own written precautions and procedures
in protecting workers from the blasting site during drilling,
charging, detonation, and inspection.
An audible blast warning system must be employed to warn workers
on the site of the impending blast, as well as clearance to re-enter
the blast zone ("all clear signal"). Once the blast
has occurred, and prior to giving the all-clear signal, the blasting
contractor is responsible for conducting an inspection of the
blasted area to ensure that all charges have detonated. If charges
are found to be partially detonated or undetonated altogether,
the blasting contractor shall ensure that the explosive charges
are dealt with in a safe manner (see section 3.4 Dealing with
Misfires).
Misfires must be identified, reported, and
dealt with
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3.2 Identifying Misfires
The blasting contractor, under the authority of the constructor
on site (if one exists), shall assume responsibility for handling
a suspected misfire in a blast site. A suspected misfire refers
to the following:
- any remaining blast hole or portion of a blast hole which
contains damaged signal tube, electric detonator wires, detonating
cord, or safety fuse
- any remaining portions of a charged blast hole (i.e. "cutoff"
or "bootleg") which is suspected to contain explosives
- any unexploded charge or suspected unexploded charge
- any situation where a safety fuse has been used and the number
of "shots" counted is less than the number of blast
holes fired
- any situation where there is reason to suspect that explosive
charges have failed to explode.
The first priority in dealing with a misfire is to guarantee
the safety of personnel and to make the location secure. Persons
not directly involved in treating the misfire may be required
to leave the blast area until remedial action is taken. The directions
of the blaster-in-charge must be followed at all times.
3.3 Discovering and Reporting Misfires
The blasting contractor must inspect the blast area prior
to giving the all-clear signal. When a misfire is found during
the post-blast inspection by the blasting contractor, the blaster-in-charge
should examine the site, advise guards to remain in place, and
attempt to re-fire the explosive. If the misfire is not successfully
re-fired and/or it appears unlikely that it will re-fire, the
all-clear signal should be given and the area around the misfire
should be barricaded for later disposition.
If any worker suspects or discovers a misfire during excavation,
digging operations shall cease immediately in the area and a
supervisor shall be notified. The supervisor shall notify the
person responsible for having the blasting contractor deal with
proper disposal of the misfire. The blasting contractor shall
examine the location to determine whether it is safe to work
in the area. If additional misfires are found in a blast site,
the misfire area and a five-metre radius shall be barricaded
until the blasting contractor has dealt with the misfires.
3.4 Dealing with Misfires
Only workers qualified and experienced in working with explosives
shall attempt to deal with misfired explosives. The blasting
contractor shall assume responsibility for undertaking the disposal
of misfired explosives.
A blasting contractor may re-fire a misfire if detonating
devices are undamaged. Once the misfires are re-fired, the blasting
contractor shall re-inspect the area to ensure proper detonation.
Where a misfire cannot be re-fired by ordinary means, the blasting
contractor may have to remove stemming material to re-prime a
hole and blast when appropriate. In areas where the explosives
are exposed, such as in a spoil pile, the blasting contractor
shall carefully remove them from the blast area for disposal
by an appropriate means.
The blasting contractor must take special precautions when
dealing with equipment used to uncover or extract explosives
in a blast hole. One such precaution is the use of nonconducting
plastic or rubber hoses when using water to wash out stemming
or water-soluble explosives. Workers should stay upwind of any
blasting operations since fall-out may contain chemicals that
could irritate eyes, nose, skin, or throat.
3.5 Record of Blasting Information
Each blasting contractor in Ontario shall keep an accurate
record of type and amount of explosive used, blast pattern, depth
of drill holes, and location of suspected misfires (not found)
for each project worked on. This record shall be retained by
the blasting contractor and the owner of the project to ensure
that future contractors can refer back to it as required. If
blast holes or patterns were laid out by survey methods, those
records shall also be retained to ensure accuracy of locating
blast holes and blasting limits in future works.
3.6 Responsibility of Other Contractors on Site
Employers on a site with drilling and blasting activities
are responsible to ensure worker safety. All employers must be
aware of hazards from lost, partially detonated, or undetonated
explosives along the right-of-way where blasting has taken place.
These explosives may be located in drill holes, rock rubble,
or lodged in bootlegs.
The contractor in charge of excavating blasted material shall
equip all excavating machinery used in the clearing and grading
operation with shatterproof glass (Lexan Mar Guard or equivalent)
in front of the operator's position. This initiative will protect
the operator from flyrock should the equipment encounter undetonated
charges. Personnel attending backhoes or loaders involved in
excavating blasted material must stay clear of the work and only
approach the area when the equipment has stopped. All employers
shall ensure that workers and operators wear the prescribed personal
protective equipment for the task assigned.
Employers must instruct and ensure that all workers immediately
report to their supervisor any suspected misfires or explosives
found during excavation or other work.
3.7 Precautions When Working in Blasted Areas
The blasting contractor must be cautious when preparing for
another round of drilling and blasting on the same site. The
blasting contractor must be able to identify all previous blast
holes to ensure that new holes are not drilled on top of them,
potentially setting off partially detonated charges still present
at the bottom of the hole.
The following procedure shall be followed by the blasting
contractor prior to the start of each drilling operation in those
areas where blasting has previously been conducted:
- The bedrock surface area within a 300 mm radius of the proposed
holes shall be thoroughly cleaned of all debris down to bare
rock using manual or machine excavation and compressed air.
- A thorough examination shall be made of the bedrock to locate
previous blast holes or remnants of holes to ensure that no missed
holes or cut-offs are encountered.
- Any pre-drilled holes or remnants of holes that are found
shall be circled with red/orange fluorescent paint and marked
with a like-painted stake and shall be examined by a qualified
blaster to determine that they are free from undetonated explosive
products.
- Drilling shall not start until all holes or hole remnants
in the area have been located, circled with paint, marked by
a stake, and determined to be free of undetonated explosive products
by a qualified blaster.
- Should explosives or suspected explosives be encountered:
the area shall be clearly marked as being hazardous and
entry restricted to personnel experienced and qualified in blasting
techniques;
no attempt shall be made to remove or destroy any powder
or detonators; and,
the contractor in charge of the site (constructor) shall
be notified immediately in order to liaise with the blasting
contractor and approve a method of destroying the explosives.
- Holes shall not be drilled within the prohibited radius adjacent
to any loaded holes. These distances are specified in provincial
regulations for the province where the work is located.
- Where ground water or a rainstorm has resulted in the accumulation
of water in a drill site, dewatering must be conducted to allow
drilling personnel to maintain a clear view of the drill surface.
Previous blast holes call for special precautions
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4.0 PROJECTS WITHOUT BLASTING OPERATIONS
Where new contracts are called for projects on previously
blasted sites, contractors and their employees are at risk of
being exposed to potentially live old explosives. It is possible
that partially detonated or undetonated explosives still remain
active underground in drill holes or as remnants in overburden.
The hazard exists if the contractor is unaware of previous blasting
or, when aware, does not use mitigating procedures during excavation.
A more hazardous situation arises when contractors and their
employees do not report the discovery of explosives immediately
to qualified personnel.
4.1 Obtaining Site Information
During the tendering process for a project, contractors should
inquire whether the site was the location of previous blasting
operations, if this information is not already stipulated in
the tender documents. If information is available from the owner
or the blasting contractor who worked on the previous project,
it is prudent for the successful contractor to get a copy.
If excavation or disturbance of the blasted area is part of
the new contract, the contractor must attempt to lay out blast
limits and patterns if such information is supplied.
4.2 Mitigating Measures
As they do when excavating newly blasted areas, contractors
shall equip all excavating machinery with shatterproof glass
and wire mesh in front of the operator's post to prevent any
flyrock from injuring the operator. Workers on foot should always
stay a safe distance from the equipment and only enter a machine's
work zone when activities stop.
If any worker suspects or discovers old explosives or drill
holes during excavation or other activity, work in the area must
stop and a supervisor shall be notified immediately. A supervisor
shall consult with the owner of the project to have a qualified
blasting contractor inspect the site and dispose of explosives
in an appropriate manner.
Unqualified workers and equipment operators
should not attempt
to handle or dispose of explosives in any manner.
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