Chapter 23: Avalanche Control

Learning Objectives

• Explain the concept of avalanche control.
• Define the common terms related to avalanche control.
• Describe the qualifications, roles, and responsibilities of personnel who work in avalanche control blasting operations.
• Explain how closures and sweeps are carried out in the danger area.
• Describe the general requirements for handling explosives in avalanche control operations.
• Discuss actions required to examine the blast site after a blast.
• Describe the requirements and procedures for disposing of misfires.
• Identify the blasting experience required to obtain a WorkSafeBC avalanche control blasting certificate.
• Describe Avalaunchers, their composition, and how to work with them in avalanche control.
• Describe how cornice-control operations work and why they are used.
• Explain how hand-charging operations work and why they are used.
• Explain how case-charging operations work and why they are used.
• Describe how helicopter deployment works and why it is used.

Overview

"Avalanche control" refers to using explosives to reduce the risk that avalanches pose to people, property, and activities. It can involve intentionally triggering avalanches during times when people are not present at a facility or on a road. It can also involve frequently triggering smaller avalanches to help prevent larger, more destructive avalanches.

Avalanche control can be done only by blasters with an avalanche control blasting certificate and one or more avalanche control endorsements.

Common Terms

Personnel

Every avalanche control blasting operation in B.C. must have an individual with both of the following:

• A WorkSafeBC certificate valid for avalanche control blasting with the appropriate endorsements for the control methods used
• An Explosives Regulatory Division letter or equivalent

When more than one certified blaster is present in a team, a blaster of record must be designated to oversee all aspects of the blasting operation.

Blasting operations must have a minimum of two workers: the blaster and an assistant. Exceptions may apply in helicopter operations as specified in the respective written procedures. Some operations may have more than one assistant.

If assistants do not hold valid blasting certificates (with required endorsements), the blaster must do the following:

• Exercise visual supervision over them.
• Be responsible for their work during loading, priming, fixing, or firing of explosives.

Responsibilities

Every person who has knowledge and control of any particular activity in a blasting operation must ensure that the activity is planned and conducted in a manner consistent with the Occupational Health and Safety Regulation and recognized safe blasting practices.

Explosives and blasting accessories must be stored, transported, handled, and used:

• In the manner recommended by the manufacturer
• In accordance with the OHS Regulation

Blaster of Record

The blaster of record is responsible for:

• Determining whether avalanche control measures are required, and if so, what type of mission is performed
• Conducting a safe and efficient avalanche control mission from the time it is announced to the time the facility or road is reopened
• Ensuring that all members of the team understand the blasting plan and their roles and responsibilities
• Carrying out all phases of the mission, including:
  • Charge preparation
  • Communication
  • Safe travel
  • Target selection
  • Deployment of shots
  • Dealing with any misfires that occur
• Recording all blasting activity and results in a personal blasting log

Blasters must be familiar with the following:

• The manufacturer's handling recommendations
• Current laws and regulations related to acquiring, transporting, storing, using, and disposing of explosives

Blasters are also responsible for immediately reporting any theft or attempted theft of explosives to the Chief Inspector of Explosives at the Explosives Regulatory Division of Natural Resources Canada.

Any dangerous incident involving explosives, whether or not there is personal injury, must be reported to WorkSafeBC.

Assistant

The assistant is responsible for assisting the blaster of record as necessary. This can involve tasks such as:

• Assisting with loading, priming, fixing, or firing of explosives
• Alerting the blaster about unsafe conditions
• Recording observations in the log book kept at the worksite

Record Keeping

Every blaster must maintain a personal blasting log. Blasting logs must be kept for at least five years.

In the log, keep records for each explosive placed and its results.

The blaster should also maintain avalanche occurrence forms that include the following information:

• Avalanche characteristics
• Any resulting damage
• Closure and sweep start and end times

A copy of the approved avalanche control procedures must be kept on site. The procedures should be available for all workers and for inspection by WorkSafeBC upon request.

Reviewing and Revising Procedures

Avalanche control work procedures must be submitted to and accepted by WorkSafeBC before any work is performed.

Employers must ensure the following:

• All procedures for the use of explosives in avalanche control are reviewed annually.
• Proposed changes to the procedures are submitted to WorkSafeBC for approval before implementing them.

Avalanche program workers should review the procedures regularly to ensure they reflect current industry best practices.

Carrying Out Closures and Sweeps

The danger area includes:

• The blast site
• All areas affected by the air blast
• All terrain where avalanches could result from the use of the explosives

The danger area must be:

• Cleared of people before each avalanche control operation begins
• Confirmed clear by radio communication

Designated workers must carry out road or facility closures and perform a "sweep" (i.e., clear people out of an area) before every avalanche control operation. Where backcountry users may be present, perform a visual sweep of the danger area. A visual sweep is done by helicopter.

Blasting signals for avalanche control are not necessary as long as the above measures are taken to ensure safety within the danger area.

Closure control workers with warning signs and physical barriers should be located at each end of a closure area. Sweep workers are responsible for travelling between the identified closure points to ensure the following:

• No one remains within the danger area.
• It is safe to proceed with avalanche control operations.

The sweep workers notify the blaster of record by radio once they have left the danger area.

Once avalanche control is complete, the blaster of record notifies the closure control workers on site. Provided no further avalanche activity is expected, the maintenance contractor or facility operator is responsible for:

• Clearing the road or facility of avalanche deposits
• Ensuring the road or facility is safe before reopening it to the public

Handling Explosives and Returning to the Blast Site

Handling Explosives

Specific procedures for preparing explosives are contained in each avalanche control operation procedure. Explosives must be stored, transported, handled, and used in a manner recommended by the manufacturer.

The blaster of record determines the most appropriate primer-assembly location closest to the blast site. The blaster of record also ensures that explosives and detonators are only brought together at the last practicable moment.

Returning to the Blast Site

After a blast, the blaster of record carefully examines the blast site for undetonated explosives and other dangers where possible. Where this is not possible (for example, where a blast site is inaccessible), the blaster of record will observe and listen to the detonations and verify the charges have fired. If the blaster of record thinks that a charge did not fire, they will record the suspected misfire in their blasting log. Then the blaster follows the misfire-disposal procedures.

Disposing of Misfires

Misfires anywhere in the avalanche path create hazardous debris that can affect a road or facility. Because these misfired explosives can move due to natural or planned avalanches, the blaster of record must be on site before cleanup starts.

All workers must be educated in the following:

• How to identify explosives
• The potential hazards of a misfire
• Who to contact if an explosive is found

When a safety fuse assembly fails or appears to have failed to ignite, the control team must treat this situation as a misfire. This means waiting for at least 30 minutes, or for the length of time recommended by the manufacturer (whichever is longer), before approaching the misfire location.

The location of found misfires must be communicated immediately to the blaster of record. All work is suspended until the blaster of record has disposed of the misfires.

All misfires and suspected misfires are to be recorded in the blasting log. Suspected misfires are explosions that may have detonated properly but may not have been heard or seen by the control team due to a deep snowpack, strong winds, or poor visibility.

Misfire Disposal Procedures

Misfires should be disposed of as soon as safely possible. Ensure that a misfire is not disturbed. It should be detonated using a new primer of equal or greater VOD that is placed as close as possible to the unexploded material without making contact. Use non-sparking shovels when digging for misfires in the snowpack.

If snow or avalanche conditions prevent access to misfires, they should be left until spring when conditions are safer. Mark the locations of these misfires and record their GPS coordinates as soon as possible to identify the areas to be searched later. At least two patrols should be conducted during the spring and summer to find and dispose of misfires. These recovery missions are usually performed as soon as the snow melts and before vegetation grows significantly.

Access points where recreationists could enter areas affected by avalanche control operations must have physical barriers with signs warning of the dangers of misfires. In some cases, blocking access to an area may not be feasible. In these situations, prominent warning signs with a phone number to call for current information must be clearly visible at all access points.

Disposing of Explosive Products

In some cases, it may be necessary to dispose of explosives without detonating them. In these situations, follow the procedures set out by the manufacturer.

Avalanche Control Blasting Certificate

To obtain a WorkSafeBC avalanche control blasting certificate, a candidate must have a minimum of six months of blasting experience (one full snow season). This experience must be gained while working under the direction of a blaster of record who holds a valid certificate.

The candidate must have a minimum of six missions and 25 shots in each endorsement being sought. This experience must be recorded in the candidate's blasting log. It must also be verified in a letter of competency from the blaster of record or employer prior to the examination.

A maximum of two missions in a day will be counted toward certification. Candidates must take part in the complete mission. Preparing charges does not count as a mission.

Avalanche Control Blasting Endorsements

WorkSafeBC offers four endorsements for an avalanche control blasting certificate:

• Avalauncher
• Cornice control
• Hand charging
• Helicopter deployment

Avalauncher

An Avalauncher is a type of gun used for delivering explosives to inaccessible or remote targets from a safe distance. An Avalauncher operates by releasing a measured amount of compressed nitrogen gas through the barrel. The gas propels an explosive projectile toward a target.

The gun is composed of the following:

• Two chambers
• A floating piston in one chamber
• A series of interconnected hoses and valves
• The barrel

Bottles of compressed nitrogen provide the required gas pressure.

The explosive projectile detonates on impact due to a mechanism within the tail fin assembly. The mechanism does not become armed until the projectile has left the barrel of the gun and a series of safety devices has been removed.

Avalauncher Round

An Avalauncher round is made up of the following:

• An explosive (cast pentolite or Composition B booster, 1 kg or 2 kg)
• A high-strength detonator (minimum no. 8)
• Accessories (tail fin assembly)

Transportation and Assembly

Avalauncher boosters and detonators must be transported separately to the gun platform and assembled on site.

Before assembling the projectile, inspect the tail fin assembly. Ensure there are no irregularities in the moulding or working action of the safety pin, the bore rider pin, or the base plate arming wire.

Inspect the detonator well (cap well) of the booster. Ensure there are no obstructions. Make sure there is sufficient detonator well depth by inserting a wooden dowel.

Note: Do not dismantle primed Avalauncher projectiles or return them to the magazine.

Avalauncher Team Roles

The blaster of record must have an Avalauncher endorsement and assumes the role of gunner. The second team member assumes the role of assistant.

Blaster of Record Responsibilities:

• Ensuring safety of the entire operation
• Operating the gun
• Supervising the blast site
• Confirming detonation of charges
• Preparing the rounds
• Loading and remotely firing the rounds
• Completing the blasting log

Assistant Responsibilities:

• Recording the shots in the log book
• Double-checking the system assembly
• Observing the projectile in flight
• Confirming base plate separation in flight
• Confirming the targets and detonation of charges

Pre-Use Inspection

Before using an Avalauncher, do the following:

• Ensure the nitrogen tank valve is closed. Inspect all hoses, and make sure connections are tight.
• Check all safety and pressure-release valves for normal functioning.
• Inspect pressure gauges. Check ball valves and emergency pressure-release valves for damage and normal functioning.
• Check exterior surfaces of the Avalauncher and all fittings. Look for signs of wear, dents, or other damage. If there is any visible damage (including dents) to the pressure vessel, do not use the Avalauncher until it has been inspected by a competent authority (i.e., the manufacturer, a professional engineer, or Technical Safety BC).
• Ensure elevation and direction locks work properly.
• Perform a visual inspection of the barrel. Ensure there are no obstructions, debris, dents, or other flaws that could interfere with the launch of the projectile.
• Slide an inert projectile (tail fin assembly and base plate) through the barrel. Ensure there are no obstructions and that clearances are adequate.
• Test the system (dry fire the gun).

Any damaged or faulty parts found during the pre-use inspection must be repaired or replaced before using the Avalauncher.

Generic Avalauncher Procedures and Commands

Follow the manufacturer's firing procedures. These procedures include a series of verbal commands:

1. "All valves closed." - Line, fill, fire safety, and fire valves have all been closed.
2. "Aim." - The gun has been placed at the desired elevation and pointed at the target.
3. "Breech open." - The breech has been opened.
4. "Barrel and breech clear." - The barrel and breech have been visually inspected and are clear.
5. Final check to ensure base plate arming wire and safety cotter pin are in position.
6. "Shot in breech." - The projectile has been placed into the breech.
7. "Safety pin out." - The safety cotter pin has been removed from the bore rider pin.
8. "Breech locked." - The breech has been closed and locked.
9. Open pressurized-line valve, fill valve, close fill and line valves.
10. "Clear the deck." - Move to the remote firing location behind the blast shield.
11. "Ready to fire." - Visual sweep complete.
12. "Safety off." - Remote safety valve opened.
13. "Fire." - About to open the remote-fire valve.
14. "Safety on." - Safety and fire valves closed.

After firing:

• Ensure the nitrogen cylinder valve is closed.
• Observe the target to visually confirm detonation.
• Repressurize the gun to a minimum standard (seat the gun).

Cornice Control

A cornice is a body of hardened snow that hangs over the edge of a mountain ridge. Depending on its size and structure, a cornice can trigger an avalanche if it breaks off and falls on the slope directly below it.

A cornice can be removed by placing charges in a line within or on top of the snowpack and detonating them to effectively "cut off" the cornice. These cornice-control explosions often initiate avalanches that help stabilize the slopes below.

Equipment

The following equipment is typically used in cornice-control operations:

• Explosives (ANFO, cast boosters, safety fuse assemblies, shock tube assemblies, detonating cord, etc.)
• Pull-wire lighters or shock tube initiators
• Timing device
• Portable radios
• Blasting tools and accessories
• Hearing protection
• Appropriate mountaineering equipment

Personnel

The blasting team consists of a blaster of record and one or more assistants. The blaster of record must hold a valid avalanche control blasting certificate with an endorsement for cornice control.

Procedures

1. Initiate the area closure.
2. Proceed to the target area.
3. Ensure that the closure is effective and the area is clear.
4. Identify the work area and proper belay locations and techniques.
5. Initiate the belay.
6. Dig or punch holes in the snow at the required spacing and depth.
7. Remove a detonating cord assembly from the pack and bury it in each hole.
8. Lay out detonating cord within the safe zone with enough extra cord off the cornice area.
9. Cut the detonating cord from the roll.
10. Connect the detonating cord branchlines to the main trunkline.
11. Move everyone out of the blast site.
12. Attach two safety fuse or shock tube assemblies to the detonating cord.
13. Trim the fuses just before attaching pull-wire lighters.
14. Light the fuses and confirm they are burning.
15. Move to a predetermined safe location to await detonation.
16. Check for misfires and record results.
17. Notify closure control workers.

Safety Precautions

• The cornice blasting team members must be within voice and visual contact at all times.
• Safety fuse assemblies must be carried separately from detonating cord and other explosive products.
• The blaster and all crewmembers must leave the danger area immediately after fuse ignition.
• Use hearing protection during detonation.
• Do not carry flammable or sparking materials with explosives.
• All personnel working on the cornice must be "on belay" at all times.

Hand Charging

Hand charging involves deploying charges by hand into target areas of an avalanche start zone. Workers on skis transport explosives in backpacks to a location near the start zone. On arrival, the blaster deploys the charges into target areas. Once the shots have been deployed, the workers retreat to a safe area to await detonation.

Hand charging usually occurs in unfavourable weather and snowpack conditions. Charges are usually assembled in advance at a safe, sheltered location close to the blast site.

Hand charging lets blasters place shots accurately into target areas. It also allows blasters to control many areas in a short period of time at minimal expense.

Equipment

• Explosives
• Safety fuse assemblies
• Pull-wire lighters
• Timing device
• Portable radios
• Blasting tools and accessories
• Avalanche-specific PPE (transceiver, probe, shovel)
• Hearing protection
• Appropriate means of transportation (skis, snowmobiles, snowcats, etc.)

Procedures

1. Initiate the area closure.
2. Proceed to the target area.
3. Ensure the closure is effective and the area is clear.
4. Identify the target locations.
5. Remove primers from the pack.
6. Trim fuses and attach pull-wire lighters.
7. Light the fuses and confirm burning.
8. Use an underhand throw to toss the hand charges into the desired locations.
9. Move to a predetermined safe location and wait for detonation.
10. Check for misfires and record results.
11. Repeat as necessary.
12. Notify closure control workers.

Note: If a fuse fails to light, deploy it and treat it as a misfire. Relighting safety fuse is prohibited.

Safety Precautions

• The blaster of record and assistant(s) must be in voice and/or eye contact at all times.
• Do not attach pull-wire lighters until ready to deploy.
• Leave the danger area immediately after fuse ignition.
• Use hearing protection during detonation.
• Do not carry flammable or sparking materials with primers.

Case Charging

Case charging involves detonating a relatively large explosive charge — 25 kg (55 lb.) or more — directly in front of the targeted avalanche paths. The resulting shock waves disturb the snowpack and cause the release of unstable snow.

Case charging is ideal for unconfined slopes with start zone elevations within 150 m (164 yd.) of shot placements. This type of explosive control is ideal for cleaning out short-slope avalanche paths.

Equipment

• Mode of transportation (truck, snowmobile, or snowcat)
• Timing device(s)
• Portable radios
• Explosives
• Safety fuse assemblies
• Pull-wire lighters
• Blasting tools and accessories
• Hearing protection

Procedures

1. Initiate the area closure.
2. Proceed to the avalanche control area.
3. Ensure sweep and closure have been performed.
4. Position a guard outside the danger area.
5. Prepare the explosives in an avalanche-safe location.
6. Drive to the blast site.
7. Park facing the exit direction, keep engine running.
8. Place the explosives so all charges are in contact.
9. Trim fuses and attach pull-wire lighters.
10. Light the fuses and confirm burning.
11. Drive immediately out of the danger area.
12. Check for misfires and record results.

Safety Precautions

• Do not attempt case charging if significant natural avalanche activity is expected.
• Do not work directly beneath the avalanche path.
• Guards must be equipped with warning devices and search and rescue equipment.
• Case charging should only be applied to short slopes.
• Park the vehicle between the avalanche path and the blaster.
• Use longer safety fuse assemblies if uncertain about escape time.

Helicopter Deployment

Helicopter deployment can be used to easily and safely apply explosives to the snowpack in a relatively short period of time. This control method can access terrain that is difficult or impossible to reach by other methods.

Helicopter deployment is not an option during:

• Periods of poor visibility
• At night

Under federal regulations, helicopter operators must obtain approval to drop explosives from rotorcraft and transport dangerous goods.

Equipment

• A helicopter with a radio set on a closed frequency
• Intercom headsets or flight helmets
• Fall-restraint systems (harnesses, anchors, lanyards — seat belts cannot be used as anchor points)
• Timing devices
• Explosives (ANFO, cast boosters, emulsion cartridges, safety fuse assemblies, etc.)
• Pull-wire lighters
• Blasting tools and accessories
• Terrain photos

Personnel

The blasting team usually consists of a helicopter pilot, a blaster of record, and an assistant. An assistant is optional and at the discretion of the blaster of record and the pilot.

The blaster of record must be certified for transportation of dangerous goods (TDG) by air and must hold a valid avalanche control blasting certificate with an endorsement for helicopter deployment.

Procedures

1. Initiate the area closure.
2. Arrange the helicopter for safe explosive drops.
3. Test intercom and radio.
4. Rehearse charge-deployment procedures with voice commands.
5. Load primers aboard in a jettison-able container.
6. Attach lanyard to approved anchor points.
7. Put on approved harness.
8. Proceed to target areas.
9. Confirm closures and sweeps are complete.
10. Ready the primer and pull-wire lighter on approach.
11. Trim fuse and attach lighter: "Lighter on."
12. Ignite fuse: "Fuse lit."
13. Drop charge down and away from helicopter: "Shot is away."
14. Record time and location.
15. Stop placing charges 90 seconds after lighting first fuse.
16. Move to safe location to observe detonations.
17. Record results and repeat as needed.
18. Notify closure control workers.
19. Dismantle unused primers after landing.

Dealing with Non-Functioning Safety Fuse Assemblies

If a safety fuse assembly fails to light, the blaster deploys the charge as a dud when it is safe to do so. This should be done within 45 seconds from the time the pull-wire lighter was activated. The pilot positions the helicopter over a location where the charge can be disposed of, then moves to a safe zone. The blaster of record stops further deployment and observes the waiting period for misfires. Relighting safety fuse is prohibited.