Discovering the cause and origin of a destructive wildfire

Fire expert Dave Dobson was hired to find the cause and origin of a wildfire that left a swathe of destruction across farms and forestry plantations in the KZN midlands in 2007. Working years after the event, Dave followed the trail of smoke to uncover the origin of the runaway fire that burnt thousands of hectares to a cinder …

The dispute surrounding the ‘Kentucky’ fire of 25th June 2007 that devastated farms and commercial forests in the Curry’s Post area of KwaZulu-Natal has eventually been settled. The fire caused extensive damage to privately owned farms and commercial forest plantations in the area.

As a result of the fire one of the plantation owners instituted legal proceedings against the owners of two properties where the fire was purported to have originated. This case study deals with the case against the second Defendant, the owner of the farm Kentucky.

The challenges
The objective of every fire investigation is to establish the cause and origin of the fire and to determine the ignition sequence.

The first challenge, and one that is regularly encountered in work of this nature, is the fact that I was appointed to investigate the origin and spread of this fire on behalf of the Defendant some seven years after the event (i.e. in 2014).

The Defendant was not a member of the local Fire Protection Association. This raised two issues. The first was that the Defendant was deemed negligent in the event of a fire originating or exiting his property and the onus rested on the Defendant then to prove his innocence. The second issue was that the Defendant was denied access to information held by members of the Fire Protection Association. This was particularly important in respect of the origin of the fire under investigation.

Other issues that contributed to the charge of negligence against the Defendant related to the presence of a compartment of plantation waste/slash located on the boundary between the Defendant’s farm and a neighbouring commercial forest plantation. This was deemed to be a fire risk which contributed to a massive flare-up that resulted in the fire spreading to the Plaintiff’s plantations.

The fires
A number of fires occurred during this period. The first two occurred on the property adjoining Kentucky Farm (St Clair Estate) while the third, as will be shown later, arose on Kentucky Farm. This led unfortunately to the fire becoming known colloquially as ‘the Kentucky Fire’ which was not entirely correct!

The first fire (fire A) occurred on Sunday 24 June 2007. It was extinguished on St Clair Estate (Kentucky’s neighbour) and played no further role in the events that unfolded the following day.

The second fire (fire B) started on the morning of Monday 25 June 2007 on St
Clair Estate and swept through Kentucky Farm fanned by extreme weather conditions.

A third fire (fire C), that was not reported, started on Kentucky Farm during the afternoon of Monday 25 June 2007. This is the fire that resulted in the extensive damage to commercial plantations and farms in the area, which was the focus of this lawsuit.

Data collection
I approached the investigation in a systematic manner beginning with a site visit and an interview with the Defendant. This proved useful in providing circumstantial evidence tracing the progress of the fire through the Defendant’s property. Of particular importance however, was acquainting myself with the overall fire area which was to prove beneficial later in the investigation.

Empirical data was collected in the form of weather data during the time of the fire, interviews and fire reports from various parties who were involved in fighting the fire as well as photographs taken from the spotter aircraft monitoring the fire. A vital piece of evidence was pictures taken of the origin and spread of the fire recorded by Fire Hawk’s locally based fire tower. This information was not readily available to the Defendant since he was not a member of the local Fire Protection Association. However, the picture sequence of the fire was in the public domain as it was being used to conduct Fire Boss Training courses. A simple request for the pictures provided access to this vital piece of information!

In addition, and rather late in the day, an Expert Report was received from the Plaintiff’s legal team.

Cause and origin of the fire
Once the data had been collected and analysed it was possible to develop a hypothesis of the events that occurred on this day. This hypothesis was then subjected to systems analysis to develop a broad understanding of what happened and to avoid linear thinking. This initial hypothesis is depicted in the following diagramme.

In developing this initial hypothesis consideration was given to the summons which suggested that the fire originated from the Sunday night fire (fire A) that had – according to the summons - not been properly extinguished. Various witness statements however refuted this contention. Furthermore, picture evidence obtained from the Fire Hawk camera appeared to indicate that the fire that damaged the Plaintiff’s plantations originated near some homes on the neighbouring St Claire Estate and was the result of a member of the household throwing out ash from the previous night’s hearth fire during the morning of Monday 25 June (fire B).

When examining a problem systematically there are tools in systems thinking that can assist with an enquiry. Systems archetypes are one such tool. As one works with the problem, developing the story, identifying the key variables and sketching them in causal loop diagrams, patterns begin to emerge which provide keys to unlocking parts of the problem. These generic patterns are described in systems thinking as archetypes (Kim, D., H. and Anderson, V. 1998).

A typical “Escalation” archetype now emerges where discarded ash from a previous night’s fire catches alight and starts a fire (fire B). This fire later enters the plantation slash on Kentucky and under deteriorating weather conditions escapes causing havoc to farms and commercial forest plantations down wind. This served as an initial hypothesis for testing against further empirical evidence.

The crucial evidence related to the slash in an old pine compartment located on Kentucky Farm, adjacent to the boundary between Kentucky farm and a neighbouring commercial forestry estate. The trees in this compartment had been clearfelled six years prior to the fire and most of the plantation residue would have decomposed by the time of the fire. Nevertheless the Plaintiff’s Expert presented pictures showing clear lines of fire burning in the old pine compartment which were ascribed to the brush piles having caught alight. The picture also clearly showed a road in the area.

I was aware that no such road existed and began searching for an answer to this conundrum. It turned out that the fire depicted in the photographs was actually burning on a property on the other side of the Curry’s Post road some 1.5 km away! The owner of the property was contacted and confirmation was received that he had in fact cleared and stacked jungle wattle and gum in this area of his farm a few months prior to the fire! The picture of the plantation slash burning that was presented as evidence of negligence on the part of the Defendant was incorrect – the photos were of another property on the other side of the Curry’s Post road.

Brush burning 1.5 km away from the Kentucky fire.

It was time to test the validity of the evidence of the fire entering and escaping from the old pine compartment on Kentucky Farm.

A closer inspection of the photographic evidence of the fire in the section of Kentucky farm bordering the commercial forest revealed further interesting empirical data. The first was clear evidence – i.e. straight line burns - of firebreak burning in kikuyu camps adjacent to the old pine compartment on Kentucky. Wild fires do not burn in straight lines. From the available photographs it was evident that the party responsible for initiating this firebreak burn lost control of the operation resulting in it entering the old pine slash compartment on Kentucky farm, and subsequently the neighbouring forest where it was brought under control by the land owner. However, the fire in the old pine slash compartment on Kentucky continued to burn. This was fire C.

Unburnt Kikuyu camps on Kentucky Farm. Fire heading to the Kentucky homestead.

The events leading to the origin of this fire were never reported, although mention was made in a fire report of drip torches being issued to a helitack ground crew who were dropped in the area in an effort to mop up and contain the fire.

Soon after this, evidence of the fire break between Kentucky and the commercial forest plantation being half burnt indicated a further attempt to contain the fire. The Expert for the Plaintiff (who had previously been contracted by Kentucky’s neighbour to prepare a report on the fire) mentioned the “application of a counter fire along the land owner’s boundary closing up to the main plantation road.”

Clearly there were numerous attempts to introduce counter fires and fire-breaks along this boundary under extreme weather conditions.

At the same time as fire C was burning in the old pine compartment on Kentucky farm, a power failure at the landing strip where the water bombers were refuelling delayed their return to the fire. A further complication arose when weather conditions became too dangerous to fly. Eventually the fire exited the old pine compartment and was driven, out of control, by the extreme weather conditions across many farms before entering the Plaintiff’s commercial pine plantations where extensive damage was experienced.

Final hypothesis
It now becomes possible to develop a final hypothesis describing the fire. This hypothesis is summarised in the diagramme that follows.

Initially as mentioned a preliminary hypothesis was considered which was represented by an “Escalating” archetype: Discarded ash catching alight and resulting in the fire spreading onto Kentucky Farm from whence it enters the slash in the old pine compartment and later spreads to neighbouring farms and forest plantations (fire B).

However, on further investigation a second archetype emerged – a ‘Fixes that Fail’ archetype where an unintended consequence of the use of counter fires or fire-breaks set in an effort to contain fire B, results in the fire escaping and entering the old pine compartment on Kentucky farm from whence, after a delay (indicated by the parallel lines) the fire enters farms and commercial forests causing immense damage (fire C).

An interesting addition to the overall picture is the loop linking Curry’s Post road to the main fire. Pictures of the windrowed plantation slash on a property some 1.5 km away from the Defendant’s farm across the Curry’s Post road from the Defendant was presented as evidence of negligence on the part of the Defendant. This was shown as being clearly incorrect!

Results
After careful consideration of the evidence and interviews with people involved it became clear that the Defendant did not act negligently.
The unintended consequence of trying to “fix” the problem of fire B exiting Kentucky by burning counter fires and fire-breaks on the Defendant’s property is the probable cause of the subsequent damage to farms and forests downwind of Kentucky. This counter fire activity was never reported.

The evidence presented of the extreme fire danger posed by the plantation slash on Kentucky plus the photographic evidence of windrowed slash burning in support of this claim was refuted.
In the end the Plaintiff’s summons was deemed to have no substance and was subsequently withdrawn. The Plaintiff ended up having to pay the Defendant the cost of suit.

References
KIM, D., H., ANDERSON, V. 1998. Systems Archetypes Basics. From Story to Structure. Waltham Massachusetts, Pegasus Communications Inc.

Sawdust fires and the law

Despite the fact that sawdust piles are fire hazards, they are very unlikely to spontaneously combust as a result of heat build-up as the composting process of pure sawdust is too slow. This argument was accepted by the judge in a court case in which a sawmiller was sued by a neighbouring landowner who claimed that a sawdust pile spontaneously combusted, causing a fire that damaged his plantation. DAVE DOBSON reports …

Background
This case study deals with allegations of spontaneous combustion in sawdust heaps on the Defendant’s property that resulted in a fire that devastated a neighbouring commercial pine plantation.

The Client
The client was the Defendant in this case; the owner of a property on which eucalypts were grown to supply a sawmill that processed the timber to produce pallets.

The sawdust arising from the milling operation was dumped at various localities on the property and not incinerated on account of the danger associated with this operation.

This case deals specifically with the claim by the Plaintiff that as a result of the manner in which the Defendant managed the sawdust, spontaneous combustion occurred. This lead to the wild fire that burnt the neighbouring commercial pine plantation belonging to the Plaintiff.

The Challenges
A number of challenges arose in the case but the most important one related specifically to the sawdust. In the summons it was claimed that the sawdust piles constituted a fire hazard in that:
• The Defendant had not intermittently layered the sawdust with soil.
• The Defendant had not restricted the height of the sawdust heaps so as to avert or minimise the risk of spontaneous combustion occurring in the sawdust pile.

The Plaintiff claimed that these two omissions were largely the reason for the spontaneous combustion occurring.

A third claim was that the Defendant failed to maintain an effective firebreak around the perimeter of the sawdust piles. Such a firebreak - if implemented - would have contained the fire to the sawdust pile.

The Solution
While sawdust fires are recognised as being a potential fire risk, SAFIRE Insurance Company Ltd. had at the time that this court action commenced (2012) never received a claim emanating from smouldering sawdust piles.

However there was a single incident reported to SAFIRE of a fire in a sawdust pile, but this was not the result of spontaneous combustion of the pile. This was a fire in sawdust at a sawmill on the farm Etterby in the Richmond district. This fire was extinguished by digging out the smouldering sawdust and dousing the area with water. The fire had entered the sawdust while the landowner was burning a firebreak around the sawdust pile.

Spontaneous combustion does at times occur at composting facilities when the compost heaps self-heat to temperatures high enough to ignite. In these instances no external heat source is required. In order for composting organic material to ignite very specific conditions are required. These are:
• A C:N (Carbon:Nitrogen) ratio of 20:1 to 35:1 is required. Sawdust has a C:N ratio of between 300:1 to 400:1. The result of this is that the composting process for pure sawdust will be extremely slow. (Nitrogen is required to feed the micro-organisms that are responsible for the composting process. There is simply not enough of this nutrient for them to thrive!)
• The moisture content of the compost heap must be greater than 50%. Below this percentage the composting process slows down.
• Aeration is required for rapid, efficient composting. Allowing the organic material to become anaerobic (compacted) will slow the composting process.

In the composting process temperatures in the compost stack rise and can reach 70^OC to 80^OC as a result of the activity of the micro-organisms breaking down the organic material. Above 80^OC micro-organisms die and chemical reactions take over. This chemical heating can continue to raise the temperature of the organic material until it reaches about 150^OC at which point ignition can occur. It is important to note that both the biological and chemical oxidation processes require oxygen to proliferate. Progress is extremely slow under low oxygen (anaerobic) conditions.

Back to the spontaneous combustion sawdust pile court case. In this case the Expert for the Plaintiff used the example of silage production, likening the heat build-up in silage to spontaneous combustion. From the previous discussion a number of points arise. The first is that maize used for silage is green and thus contains a high proportion of nitrogen that is required by the micro-organisms to break down this organic material. The organic material is also moist which fulfils the moisture requirement. However, silage is compacted thus resulting in anaerobic conditions. The silage will simply not burst into flame!

Further issues that mitigated against spontaneous combustion in the sawdust on the Defendant’s property were that the sawdust was spread and compacted i.e. this would have limited the oxygen available to the micro-organisms responsible for composting this organic material. The sawdust pile in question was merely one meter deep and any heat build-up would have been rapidly dissipated. Finally, had there been any combustion in the sawdust pile a source of fine ash would have marked the site of ignition. No such evidence was found.

Sawdust waste – like this – is highly unlikely to spontaneously burst into flames due to heat build-up as the rate of decomposition is too slow!

Conclusion
Spontaneous combustion will not occur in sawdust. The primary reason being the C:N ration of this organic material. Sawdust fires will invariably be the result of fire from the outside entering the sawdust pile - as was reported in the Richmond case.

The result of the trial was a finding in favour of the Defendant. Spontaneous combustion was ruled out as the origin of the fire, and honey hunting was identified as the source. This activity had set a stump alight which later - under extreme weather conditions - ignited grass on the edge of the sawdust pile. Despite attempts by the Defendant’s team to put the fire out, it swept across the sawdust pile as well as the firebreak around the sawdust pile into a gum compartment and on into the Plaintiff’s property.

*Related article: How to calculate plantation fire damage