Chapter 11: Drilling Precautions and Requirements

Learning Objectives

• Explain precautions required for drilling.
• Identify the drill operator's responsibilities related to the inspection and maintenance of drilling equipment.
• Describe what to survey to ensure site stability.
• Explain the drilling requirements that apply once drilling begins.

Overview

A blaster is expected to know and understand the precautions and requirements for drilling where explosives will be used. Unsupervised drilling into rock can result in accidents.

Employers must provide drillers with the information, instruction, training, and supervision they need. This helps ensure the safety of drillers and other workers and the safe operation of equipment.

Pre-Drilling Requirements

The following requirements apply before drilling begins.

Inspect and Maintain Drilling Equipment

The drill operator's responsibilities include the following:

• Ensure that equipment and accessories are ready for work.
• Visually inspect the drill to detect any abnormalities, such as cracks, missing parts, and leaks.
• Ensure that levelling jacks, measurement devices, and tools for proper drill set-up on stable ground are in working order and are used.
• Ensure that dust-control equipment and devices are in place and in good working order.
• Wear adequate hearing protection when working with or near drills.
• Inspect the drill's safety devices (e.g., the emergency shutdown system) and ensure any accessories needed are present and in good working order.

Inspection Checklist

Here are some examples of things to inspect and what to look for:

• The hoses are in good condition and secured with whipchecks (safety cables).
• The feed chain, tracks, and belts have proper tension.
• The oil, filters, and fluids are in good condition.
• All machine parts are lubricated.
• The centralizer is clean.
• The drill rods are in good shape and threads aren't over-worn.
• The winch and cable blocks are in good condition.
• The hammer is working correctly.

Required Safety Equipment and Accessories

Ensure the following safety equipment and accessories are present:

• Hose mender
• Fire extinguishers
• Spill kit
• Tools
• Spare parts

Survey the Site for Stability and Previous Blasting

The site and the surrounding area must be surveyed. The goals are to determine the following:

• The stability of rock faces and the locations where the drilling rig will operate
• Whether the area has been blasted before

The area to be blasted may have to be excavated by machinery to do the following:

• Stabilize the material.
• Create a safe surface on which the drilling rig can move and operate.
• Expose previous blast holes.

If evidence of previous blasting (such as protruding wires or cartridges) is found, the blaster must examine the site for misfires. Old blast holes (also known as bootlegs or sockets) or remnants of holes should be examined and clearly marked for identification during upcoming drilling operations.

Deal with Misfired Holes or Unexploded Explosives

Misfired holes or holes containing unexploded explosives are dangerous. Drilling into explosives can cause an explosion. Check for misfired holes and unfired explosives before drilling. These explosives must be dealt with before other regular work can be carried out. Disposal procedures are covered in Chapter 9, "Disposing of explosives."

Locate and Mark Underground Utility Services

Drilling into underground gas or electrical utilities can cause an unexpected explosion or electrocution. Before drilling begins, the location of utility services must be determined and clearly marked.

BC 1 Call is the link between the excavating community and the owners of underground utilities (such as pipelines, communication cables, and water utilities) who are registered members of BC 1 Call. People who plan to disturb the ground submit requests (at no charge) to identify underground utilities. BC 1 Call then contacts its members who own utilities in the area and notifies the user about where utilities are buried on the site.

Mark Where Holes Are to Be Drilled

Ensure that the blast pattern design is properly laid out and blast-hole locations are adequately marked for the drill.

Drilling Requirements

The following requirements apply once drilling begins.

Measure the Depths of Overburden

Overburden is material (dirt, gravel, sand, etc.) that lies on top of the material to be drilled and blasted. Special care must be taken to note the depths at which the drill hits bedrock. This is crucial information for blasters, as they will need to adjust the collar length appropriately when loading.

Ensure Good Communication Between Blaster and Driller

Ensuring good communication between the blaster and the driller is an occupational health and safety requirement in B.C.

The driller must maintain a detailed report of each anomalous (unusual or abnormal) drill hole. The report must contain the following information:

• The date, location, burden, spacing, depth, diameter, angle, and marking of each drill hole
• Any changes in geology, including the presence of subsurface water, mud seams, or voids, and similar details

The blaster must review the report before loading begins.

The anomalous holes detailed in the report must be clearly marked at the blast site. Marking and identification can be done in many different ways. Examples include using double or triple cones (drill hole plugs), spray paint, sticks, etc.

Signs to Watch For

The driller can be of great help in assessing rock variations that are not apparent from the surface. The driller should watch for the following signs and communicate them to the blaster:

• Slow penetration, excessive drill noise and vibration - Signs of hard rock that may be difficult to break.
• Fast penetration and lower-than-usual drill noise - Indicate soft rock that may be more easily broken.
• Sudden drops of the drill - Indicate the drill has entered a void, a slip, or a soft seam.
• Changes in penetration time - Signs of different rock layers.

Don't Drill Near Bootlegs

Drilling must not take place within 15 cm (6 in.) of any part of a bootleg or socket (an old blast hole). This requirement aims to prevent contact with any leftover explosives from previous blasting operations.

Don't Drill Near Loaded Holes

In most operations, it is unnecessary to drill near loaded holes or to load near drilling operations.

Under the Occupational Health and Safety Regulation, no drilling can take place within 6 m (20 ft.) of any part of a hole containing explosives. The exception to this rule is when prior written permission has been obtained from WorkSafeBC.

Dealing with collapsing drill holes or conducting drilling and loading underwater may require written permission from WorkSafeBC to deviate from the Regulation's 6 m (20 ft.) restriction. If permission is granted, the blaster must direct the angle and depth of the holes being drilled to ensure no contact is made with explosives in adjacent loaded holes. A tamping rod placed in the collar of the loaded hole may help determine the correct angle for the new hole.

Ensure Sufficient Hole Diameter and Depth

Each drilled hole must be wide enough to let the explosives travel to the bottom of the hole without ramming, pounding, cutting, or excessive pressure.

Check for proper hole depth before moving the drill to begin the next hole.

Take Precautions While Changing Drill Steel or Bits

While a drill is rotating under power, the operator must not manually add or remove drill steel or bits without a helper. The operator and the helper must stay clear of rotating parts of the drill system. Do not wear loose clothing when working near rotating shafts.

Take Precautions When Drilling Angle Holes

Drill angle holes only when measurement equipment and controls are in place. These devices help to ensure correct blast-hole location and end direction.