Safe Quarry - Health and Safety Authority

PART 5
EXPLOSIVES
44. BLASTING SPECIFICATION
(Regulations 47)
47. The operator shall ensure that -
(a) an adequate written blast specification, including
identification of the danger zone based on an
assessment of the risks, is prepared by the
explosives supervisor for each shotfiring
operation at the quarry to ensure that, so far as is
reasonably practicable, when such shotfiring
occurs, it will not give rise to danger, and
(b) a copy of any relevant information contained in the
blast specification referred to in paragraph (a) is
given to any person upon whom it imposes duties
The purpose of the blasting specification is to
minimise the risk associated with the firing of shots.
The blasting specification must be specific to each
blast, to take account of site conditions.The specification
should be designed to:
minimise the risk of flyrock being projected
outside of the declared danger zone;
minimise the risk of misfires
enable the location of any misfired shots to be
accurately determined; and
ensure, where possible, that faces are left in a
safe condition after a blast.
The specification should take account of:
(i) experience gained from previous blasts at the
quarry;
(ii) any unusual circumstances which are present or
likely to arise; and
(iii) the design of the excavation.
The following matters need to be addressed when
planning, preparing for and undertaking a blast:
1. The location of the area to be blasted in the
quarry must be specified;
2. A drilling plan should be prepared showing the
hole positions, the length, diameter and the
angle of inclination of each hole and direction to
which the drill is to be set for each hole;
3. The surface position and number or other
identifier for each shothole;
4. The angle of inclination, direction, length and
diameter of, and extent of any sub grade drilling
for each completed shothole;
5. The burden around each shothole should be
adequately determined.Where this cannot be
done safely from the top or base of the quarry
face it must be determined by surveying/
profiling or by other remote means by which a
person is not placed at a risk of falling or being
struck by falling objects from the face or the
bench. Surveying/profiling of the working face
to establish burdens is not mandatory. Its use is
based on a risk assessment by the explosive
supervisor/shotfirer in order to determine the
likelihood of hazardous flyrock.
The risk assessment should take into account the
following factors:
control measures required to ensure the safety
of persons determining the burden from either
the top or bottom of the quarry face;
height of the face;
planned burdens and spacings;
diameter, angle and azimuth of the shotholes;
type and quantities of explosive used and the
initiation systems;
geology of the face and the history of the
quarry in relation to geologoical anomalies; and
proximity of the public, dwellings, roads, railway
lines, commercial buildings or other places of
work to the blast area.
6. Any geological anomalies, which could affect
the blast, in particular those identified during
drilling and inspection.These might include the
presence of cavities, clay bands, joint planes,
bedding planes or discontinuities;
7. Using the available information, particularly
that from items 4, 5 and 6, shown using plans
and sections, the burden for each shothole
should be determined and consequently the
amount, type and placement of explosives to
be used, so that the blast can be carried out
safely;
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SAFE QUARRY GUIDELINES TO THE SAFETY, HEALTH AND WELFARE AT WORK (QUARRIES) REGULATIONS 2008