Fire Fighting in Canada

Features
Strategies and tactics for peat fires

A unique suppression challenge

February 22, 2023  By Gavin Parker


Peat fire burning in open farmland. All Photos: Gavin Parker

Unlike forest and grassfires, peat fires can spread slowly for days, weeks and even months. They smoulder at a lower temperature with little flame, producing large quantities of smoke and greenhouse gasses. For suppression, they provide unique planning, logistical and operational challenges in a demanding environment. 

Methods for protection of assets, containing and extinguishing
Influencing the depth of burning and fire spread is fuel moisture, further drying by the fire, oxygen, the type and density of fuel. Burning may continue until inert minerals or deeper levels with a higher fuel moisture are reached. In some cases, fuels or soils may also become hydrophobic, repelling water. 

Several options can be used to reduce smoke and particulate emissions, protection of assets, containment and extinguishment. One or a combination of methods such as cooling, increasing fuel moisture, restricting oxygen and in some instances removing or separating the burning fuel from the unburnt may need consideration. 

Strategies and tactics
Peat fires may require different methods, equipment and machinery than what is typically used for surface fuels; this also includes the supply and delivery of water. 

Advertisement

Water can reduce dust and smoke, increase fuel moisture, contain and extinguish the fire. Peat can require large volumes of water adding to logistical and operational demands. Water can be obtained from a variety of sources such as, rivers, dams, lakes or wells. Transfer to and around the site can be by traditional fire service equipment, large and small diameter hoses and pumps. Large capacity agricultural, hose reels, irrigation pipes and pumps can also be utilized.  

Machinery and hand tools can be utilised to remove hazards, surface fuels, protect assets, contain and extinguish the fire by accessing, separating or removing fuels. They can also increase safety, efficiency and the effectiveness of works and water used. Consider practices and procedures used for land management and peat restoration for efficiency and reducing post fire rehabilitation.

Machinery should have enclosed cabins with dust filtration, roll-over protective or falling-object protective structure (ROPS/FOPS) as per agency requirements. Consider low ground pressure equipment, and accessories such as “swamp/access mats” that can be used by excavators operating on soft ground. A recovery plan for bogged equipment may also need consideration. 

Use an “anchor point” to prevent fire escape. All work should be checked visually and with a thermal imaging camera if available and monitored. Objectives and strategies may include one or a number of methods or tactics, these can include, but are not limited to the following:

Returning and retaining moisture on the site: Blocking drains or damming areas in conjunction with the direct/indirect application or redirection of water can increase fuel moisture.

Direct and indirect application of water: This can restore moisture levels, reduce dust and extinguish the fire. The effectiveness will be dependent on quantity and depth to extinguish the fuels. This can be used on shallow burning material with direct water application using a straight jet/spray, or lancing probes for deeper material. The use of hand tools or machinery can assist in water penetration and mixing. 

Methods can also include the use of sprays, sprinklers, ground monitors, and even open hose lines. These can remain in place unattended, then redeployed as needed reducing firefighter exposure to dust, ash and smoke. 

Aircraft: In remote or inaccessible areas, aircraft can be used to deliver water, foam or retardant to prevent surface fires spreading to peat areas until ground resources are in place.

Reducing the supply of oxygen to the fire: Hot spots can be capped by applying water and working it into the ash, char and peat to form a “mud slurry”, which will cool, adding fuel moisture and increasing fuel density. 

Class A foam or compressed air foam system (CAFS) may cool and reduce oxygen. It can also suppress smoke and dust emissions, providing a safer working environment for other strategies and tactics used. 

Capping small areas or “hot spots” using inert material such as clay or compressing soils with a machine can be problematic long term unless moisture levels are also returned. 

Removing and clearing surface vegetation: This can improve access and reduce hazards such as trees falling. It may be necessary for any of the strategies and tactics used. It can prevent surface fire spread and allow penetration of extinguishing mediums. This can be achieved using a combination of hand tools, machinery and powered equipment such as chain saws.

Removing burning material: This involves digging out all burning peat and adjoining margins of unburnt material, then relocating it to a non-combustible surface such as clay/sand, or a suitable container. The material can then be broken up and spread out until extinguished, with water also used if available. This tactic may be suitable for extinguishing small areas, particularly if little or no water is available.

Separating burning materials by cutting a clean edge to the lateral margins of the fire : On shallow burning edges the fire can be contained using machinery or hand tools to dig at the fires edge, separating the burning peat from adjacent unburnt material. As its dug, both burnt and unburnt “spoil” can be placed back onto the burnt area to reduce the risk of fire spread with the application of water to dampen the material. The damp unburnt fuel removed from the edge and under the burning peat can also assist in raising the overall moisture. Following extinguishment, the spoil can then be pulled back into position while dampened again if required. 

Trenches: When dug to the depth of the underlying mineral material they provide a barrier in the fuel to prevent fire spread. Alternatively, if the mineral level is out of reach; deeper, very damp unburnt peat could perform the same function. In some cases, if sufficient water is available, the trench could be filled or partially filled to form a “moat” around the fire. 

These techniques can be problematic. If filled with water, a trench will require a significant supply and may have to be continually maintained. If left dry, it may drain water from the surrounding area, further reducing fuel moisture and promote fire intensity.

Trenches and spoil piles can restrict access and may create a safety hazard, requiring an exclusion zone. Works may also have to comply with regulatory codes of practices for excavation work. 

Utilising hand tools or machinery to rip or rake through shallow burning material: It can be effective to break up the burning material to allow water penetration. Equipment with a rake, toothed bucket, or ripping attachment can be used. For small areas, suitable hand tools may be appropriate.

Opening up deep-seated fire: An excavator can be used to dig to or below the burning material and surrounding margins while applying water. As the material is broken up the water will be able to penetrate, cool and extinguish the fire, if sufficient water is available and applied it may also form a “mud slurry’. 

Ripping a narrow line on the fires edge: By using a ripping attachment to the depth and edge of the burning peat, water should then be able to penetrate, extinguish and return moisture with minimal disturbance. The main disadvantage with this method is the extinguished line will be narrow and may require monitoring and follow-up work. Once complete the spoil can be spread back into place and monitored.

Allow the fire to continue burning until it reaches damp fuel or inert materials: Once the fire edge has been contained or extinguished, any remaining unburnt islands and the continued downward burning within the perimeter may eventually stop when it either reaches the deeper inert mineral layers, or peat fuel is too damp to sustain combustion. This will require an assessment to evaluate burning potential. 

Peat burning edge cut to prevent fire spread

Any planning to allow fuels to simply burn itself out should consider the short and long-term environmental impact with further peat loss, the release of smoke and other greenhouse gases into the atmosphere, the impact on soil and water quality and potential for further fire spread. 

Conclusion
Peat fire behaviour is much different to surface fires as much of what is burning may be unseen and unknown.

They may require some unique control options compared with surface fires. A size-up and full appreciation will enable planners to formulate a course of action with clear objectives, strategies and tactics. This and an ongoing evaluation are important in developing and implementing a plan that is safe, effective and efficient. 

The views expressed are that of the author and may not be that of CFA or FRV.  


Gavin Parker is a senior station officer with Fire Rescue Victoria (FRV), Australia, who started his his firefighting career with Country Fire Authority (CFA) – Victoria in 1995. 


Print this page

Advertisement

Stories continue below


Related