Regulation 47 of the Safety, Health and Welfare at Work (Quarries) Regulations, 2008 requires that 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.
A copy of any relevant information contained in the blast specification must be 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 blasting specification may need to be updated in light of any information received from the Driller/Drill Log or the Shotfirer on the day of the blast
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 blasting 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 blast specification should record information on:
- The location of the area to be blasted in the quarry;
- A drilling plan should be included showing the hole positions, the length, diameter and the angle of inclination of each hole and direction to which the drill was set for each hole;
- The surface position and number or other identifier for each shothole;
- The angle of inclination, direction, length and diameter of, and extent of any sub grade drilling for each completed shothole;
- An adequate determination of the burden around each shothole
- 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;
- Using the available information, particularly that from items 4, 5 and 6, 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;
- The amount, type and position of explosives, the description and position of any detonator and the type and position of any stemming actually used for each shothole;
- The system of initiation, including full details of any delay sequence and timing;
- The danger zone, shotfiring position and sentry positions should be determined;
Detailed information on the Duties of the preparation of a blasting specification is in Part 5 (Explosives) of the SAFE QUARRY GUIDELINES TO THE SAFETY, HEALTH AND WELFARE AT WORK (QUARRIES) REGULATIONS 2008.