Can Fire Suppressant Gels Protect Log Decks?
A Case Study to Test the Concept

Dave Schroeder
Wildland Fire Operations Research Group
Forest Engineering Research Institute of Canada

Introduction

As part of its log deck protection project, FERIC is investigating techniques that may aid in preventing or suppressing fires in log decks.  In 2005, an opportunity arose to explore the effectiveness of fire suppressant gels at the Community Protection Trials site (formerly International Crown Fire Modeling Experiment) near Fort Providence, NWT.  These gels are mixed with water, and absorb many times their weight in water. Because the gelled water adheres to the surface of forest fuels, the gels enhance water’s effectives in suppressing fire.  FERIC, the Government of the Northwest Territories, and Alberta Sustainable Resource Development took advantage of the opportunity and conducted a case study to test the technique.

 

Case study objective

The objectives were to:

• Observe/record the spread of fire into the log deck from an adjacent debris pile.
  
  
• Observe the effect of fire suppressant gel on fire spread through the log deck.
  
  
• Attempt to suppress the log deck fire with water.
  
  
• Use results to provide direction for future research.
  

 

Methods

The case study utilized a log deck (Figure 1) composed of jack pine extracted from an adjacent fuel management plot in 2004 (Figure 2).  Wood moisture content was not measured, but the deck had dried for one year after falling.  In addition to the main deck, five small satellite decks were also built.  These satellite decks were positioned at different distances from the main deck to see if they might be affected by heat radiating from the larger fire.

Gel was applied to three sections of the large deck and to four of the five small decks (Figures 1 and 2).  The gel container was attached to a standard 1.5 inch fire fighting hose and mixed automatically once the pump was started (Figure 2).  On the two center sections of the large deck, gel was only applied to the tops and the sides facing the satellite decks.  Four of the satellite decks were completely coated while the fifth was left untreated (Figure 1).

The fire was ignited in the adjacent debris pile (Figure 1) and allowed to progress into the deck.  Fire behavior was recorded with video and still photos.  During the fire suppression portion of the trial, 2200 litres of water were applied to a 6-m section of the log deck using a standard forest fire fighting pump (Mark 3 see-http://www.wildfire-equipment.com/index.cfm) and a 1.5 inch hose with a standard nozzle.

Figure 1. Schematic showing treatments applied to the log decks.

Figure 2.  Applying gel to the log deck.

 

Results and discussion

The fire spread from the debris pile to the deck via surface fire (Figure 3).  Some embers landed on the top of the deck but they did not result in ignition.  The fire progressed along the back of the deck (the side facing the standing trees) as surface fuels and debris had not been removed and no gel had been applied to this area.  The deck was completely engulfed within 20 minutes after the fire had spread from the debris pile.

Figure 3. Fire spreading from the debris pile to the log deck.

During the first 1.5 hours after ignition, fire behaviour within the three gelled sections of the large deck was visibly less intense than for the rest of the deck (Figures 4 and 5).  The gelled section facing the debris pile did not prevent the deck from igniting because the fire spread along surface fuels and by-passed the gelled area.  If more surface fuels were removed and more gel was applied to the section facing the debris pile, the spread of the fire into the deck may have been slowed.

Figure 4.  Fire has spread along the back of the deck. 
Gelled section is in the center of the figure and is not on fire.

Figure 5.  After one hour the entire deck is engulfed, but the gelled section (in the centre of the main deck) is not burning as vigorously as the rest of the deck.  The back side of the deck was not gelled and is burning vigorously.

The attempt to suppress the fire with water was unsuccessful.  Figure 6 shows the water being applied to a 6 m section.  Although the fire appears to be extinguished (Figure 7 - far end of deck) the center of the pile continued to burn.  Eventually the entire deck burned (Figure 8). 

All of the satellite decks, except the one with heavy gel application, were consumed.  The fire spread from the large deck to the satellite decks as a creeping surface fire that eventually ignited unprotected wood.  The heavy gel application provided enough gel on the surface to prevent ignition.

Figure 6.  Water application to suppress the deck fire.

Figure 7.  After 1.5 hours, the entire deck was engaged and ground fire had engaged 2 of the satellite decks.

Figure 8.  All of the decks burned, except the one with the heavy gel application.

 

Summary

• Fire suppressant gels have potential to slow the spread of fire through a log deck and to prevent ignition.
  
  
• Direct suppression of fires in log decks is unlikely, and this has been the experience of forest industry and forest firefighting agencies on large scale deck fires.

 

New questions

• How much gel is needed for industrial scale log decks and what is the associated cost?
  
  
• How can the gel be applied to be effective? 
  
  
  • Timing? 
    
    
• Amount? 
  
  
• Penetration into large decks? 
  
  
• Safety issues of accessing a burning log deck or a deck that is being threatened by wildfire.

FERIC will work with forest industry and gel vendors to answer these questions.