Potential fire behaviour in deep chipped fuel beds: Field studies and observations on the BC Hydro Northern Transmission Line right-of-way

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1 Potential fire behaviour in deep chipped fuel beds: Field studies and observations on the BC Hydro Northern Transmission Line right-of-way October 2013 Contract Report CR Steve Hvenegaard, Researcher, Wildfire Operations FPInnovations Report Title 1 fpinnovations.ca

2 FPInnovations is a not-for-profit world leader that specializes in the creation of scientific solutions in support of the Canadian forest sector s global competitiveness and responds to the priority needs of its industry members and government partners. It is ideally positioned to perform research, innovate, and deliver state-of-the-art solutions for every area of the sector s value chain, from forest operations to consumer and industrial products. FPInnovations staff numbers more than 525. Its R&D laboratories are located in Québec City, Ottawa, Montréal, Thunder Bay, Edmonton, Hinton, and Vancouver, and it has technology transfer offices across Canada. For more information about FPInnovations, visit: BC Hydro Contract Report CON836 BC Hydro Number CR ACKNOWLEDGEMENTS This project was financially supported by BC Hydro. The author would also like to thank personnel with the British Columba Wildfire Management Branch for providing logistical and operational support. CONTACT Steven Hvenegaard Researcher Wildfire Operations (780) steven.hvenegaard@fpinnovations.ca Follow us on: 2013 FPInnovations. All rights reserved. Unauthorized copying or redistribution prohibited. Disclosure for Commercial Application: If your mill requires assistance to implement these findings, please contact FPInnovations.

3 Table of Contents INTRODUCTION... 5 OBJECTIVES... 5 METHODS... 6 Study Site... 6 Fuel Load in the Chipped Fuel Bed... 7 Ignition Probability and Sustained Flaming Tests... 8 Experimental Burns Weather Data Collection Fuel Moisture Sampling Fire Suppression Resource Requirements Comparative Fire Behaviour Analysis RESULTS Fuel Load in the Chipped Fuel Bed Ignition Probability and Sustained Flaming Fire Behaviour Point Ignitions Line Ignitions Surface Fuel Consumption Potential Fire Behaviour in Other Wildland Fuel Types Suppression Challenges Weather Data Analysis DISCUSSION Changing Nature of the Chipped Fuel Bed Ignition Potential of the Fuel Environment Fire Behaviour in a Chipped Fuel Bed Comparison of Fire Behaviour in Adjacent Fuel Types Suppression Challenges CONCLUSIONS REFERENCES Appendix A: Match-Drop Test Results Appendix B: Point Ignitions and Fire Behaviour Data Appendix C: Line Ignitions and Fire Behaviour Data FPInnovations Page 3

4 List of Figures Figure 1. Chip management operations and fuels on the South Fulmar road (July 2013) Figure 2. Chipped fuel bed in ROW before (left) and after (right) construction activities Figure 3. Study site looking south (left) and north (right)... 7 Figure 4. Fuel sampling pit at the South Fulmar study site Figure 5. Test site in the open ROW... 8 Figure 6. Slash debris and surface fuels in adjacent buffer zone Figure 7. Fuel environment in the adjacent standing timber Figure 8. Duff-consumption pin indicating surface fuel consumption Figure 9. A typical backpack pump consists of a neoprene water bag with a brass hand pump List of Tables Table 1. Location and elevation of the study site and the Nass Camp weather station Table 2. Percentile weather scenarios for the Nass Camp weather station Table 3. Distribution of fuel particle size at the NTL ROW study site Table 4. Comparison of observed fire behaviour on September 6 and predicted fire behaviour Table 5. Hourly weather data and FWI values from the Nass Camp weather station FPInnovations Page 4

5 INTRODUCTION BC Hydro is clearing vegetation from the Northwest Transmission Line (NTL) right-of-way (ROW) to allow installation of towers and transmission lines. Large volumes of vegetative biomass are created from the cutting of standing timber and surface vegetation. Conventional removal practices include hauling out merchantable timber and on-site burning. In some sections of the NTL ROW hauling out timber is not economically feasible and burning is not acceptable. As an alternative approach, BC Hydro has implemented an on-site chipping program, which results in large accumulations of chipped woody debris. Dozers are used to spread the chips and, when possible, mix it with mineral soil. During this spreading and mixing process, the chipped debris is compacted to a depth of approximately 50 cm. BC Hydro is concerned with the potential risk of wildfire and fire suppression challenges in this fuel environment. In July 2013, FPInnovations researchers observed the vegetation management operations in the NTL ROW, and sampled and evaluated the chipped fuel bed. A preliminary finding was that the surface fuel layer (0 10 cm) could reach a moisture content that would support ignition and sustained burning. Moisture content in the deeper layers of the fuel bed, however, would probably not support combustion. In September 2013, FPInnovations returned to the site to evaluate the potential risk of ignition, document fire behaviour, and assess fire suppression requirements in this unique fuel environment. This report summarizes those findings. OBJECTIVES During this study, researchers aimed to: compare the ignition potential of surface fuels in distinct fuel environments of the ROW and adjacent vegetation zones measure the following fire behavior characteristics in the chipped fuel bed of the ROW: o rate of spread o fire intensity o surface fuel consumption determine the appropriate suppression resources for containment of wildfires in the chipped fuel bed FPInnovations Page 5

6 METHODS Study Site The study site was approximately 75 km north of Terrace, British Columbia and was accessed from Fulmar Road via the Nisga a Highway. During an exploratory visit in July 2013, we observed chipping operations, chip management processes, and the chipped fuel beds (Figure 1). We observed dozers spreading piles of chipped fuels produced by the chipping operations and driving on the chips to compact the fuel bed. In some areas, the chips were mixed with mineral soil. This process resulted in a long section of a uniform, compact mat of chipped fuel between Kilometre 5 and 6.5 (Figure 1) ranging in depth from 50 to 70 cm. Figure 1. Chip management operations and fuels on the South Fulmar road (July 2013). When we returned to the site in September 2013, we discovered that extensive construction activities (footing installations and structure assembly) had altered the chipped fuel bed. The additional vehicle and equipment traffic had increased the compaction of the chipped fuel bed and had ground much of the fine fuels into the fuel bed (Figure 2). There were pockets of the original chipped fuel bed remaining in the ROW, but overall the continuity of the fuel had been broken up considerably. We located a short, undisturbed section at Kilometre 6.5 that was suitable for our study (Figure 3). At this location, the chipped portion of the ROW was 28 m wide bounded on both sides by a 19 m buffer zone consisting of slash fuels and low shrubs. FPInnovations Page 6

7 Figure 2. Chipped fuel bed in ROW before (left) and after (right) construction activities. Figure 3. Study site looking south (left) and north (right). Fuel Load in the Chipped Fuel Bed Fuel load data collection for chipped fuel environments is often conducted using destructive, plot-based sampling, and planar intercept methods (Kane et al. 2009) to determine an overall fuel load (weight per unit area). The chipped fuels across the NTL ROW study site are of greater depth (up to 70 cm) and uniformity relative to other documented fuel beds. Given the time required for destructive sampling of the entire fuel bed depth, sample drying, and analysis of fuels in our study site, we chose to use a less intensive sampling method that would still deliver data appropriate to our research objectives. We collected chipped debris from three randomly chosen sampling pits to a depth of 10 cm within a 50 x 50 cm quadrat (Figure 4). These samples were oven dried at 95 o C for 48 hours, sorted (McRae et al. 1979), and weighed to determine the fuel load by size class and to determine the bulk density of the most influential layer of chipped fuel the upper 10 cm. Bulk density is used to determine the amount of chipped fuel in a given layer and the amount of fuel available for combustion. Bulk density can also be FPInnovations Page 7

8 used to determine the lofting, or aeration, of a chipped fuel bed. It may be possible to use this data to monitor compaction of the chipped fuel bed over time. Figure 4. Fuel sampling pit at the South Fulmar study site. Ignition Probability and Sustained Flaming Tests We studied three distinct fuel environments in and along the NTL ROW, each with similar slope and aspect: the open ROW, the adjacent buffer zone, and the adjacent standing forest. The open ROW (Figure 5) consisted of a continuous, uniform chipped fuel layer (fuel particle size described in Table 3). The majority of the fuels were less than 1 cm in diameter with no large pieces. There were no overstory fuels. Figure 5. Test site in the open ROW. FPInnovations Page 8

9 In the adjacent buffer zone along the east side of the ROW, the surface fuels consisted of hemlock, spruce, aspen, and cedar slash with a few shrubs (Vaccinium spp.). There was dry moss of moderate depth. Dead and down fuels included small branches with dead juvenile stems (Figure 6). Figure 6. Slash debris and surface fuels in adjacent buffer zone. In the adjacent standing forest to the east of the ROW, about 10 m in, the overstory was dense with cedar and hemlock. The understory consisted of cedar, hemlock, and aspen. The surface fuels consisted of a thick, damp layer of moss and litter fuels (twigs, needles, and aspen leaves) (Figure 7). Figure 7. Fuel environment in the adjacent standing timber. We conducted match-drop tests on three consecutive days during the peak burning hours ( ) when conditions were favourable for ignition (lower fuel moisture content resulting from rising temperature and falling relative humidity). A match-drop test is a standard procedure (Schroeder et al. 2006) used to evaluate the probability of sustained flaming of a surface fuel layer (Beverly and Wotton 2007, Schiks 2013). A lit wooden match is placed on the receptor fuel bed. A successful ignition is recorded if the receptor fuels continue to burn for two minutes. If the first test is not successful, the test is repeated using two matches. If the second test is not successful, the test is repeated with three matches. If none of the match drops within this series sustains burning, the test is considered a failure. FPInnovations Page 9

10 In each of the three sites, we placed a row of numbered flags. We conducted a match-drop test every hour at a randomly chosen numbered flag in each of the three sites. Experimental Burns We conducted point ignitions and line ignitions on September 5 and 6 when fuel moisture content was low enough to support sustained burning. Prior to igniting each test burn, we measured air temperature and relative humidity. We placed duff-consumption pins at regular intervals in line with the wind direction and used these to measure forward and backing spread rate. We used a drip torch to ignite the chipped fuels in either a point or a 5 m line. During the observation time for each test burn (up to 50 minutes), we recorded wind speed and the fire spread distance. We recorded the growth of the fires at regular intervals throughout the observation time and measured the overall fire dimensions after each fire had been contained. To measure surface fuel consumption, we placed duff-consumption pins in the chipped fuel bed at set intervals within the projected burn area and measured the depth of consumed fuel after the fire had passed. Weather Data Collection Site-specific Fire Weather Index (FWI) values (Van Wagner 1987) could not be calculated because there was no on-site weather station that recorded the weather over the summer. Instead, British Columbia Wildfire Management Branch (BCWMB) provided daily weather data and FWI values for nearby weather stations for the timeframe of our study. The Nass Camp weather station 18 km north of the study site was chosen as the most representative weather station for our study (Table 1). Table 1. Location and elevation of the study site and the Nass Camp weather station. Location Coordinates Elevation NTL ROW Study Site Nass Camp Weather Station N 55 o W 128 o N 55 o W 128 o m 191 m BCWMB also provided historical ( ) daily weather data and FWI values for the Nass Camp weather station. We processed this data to establish weather values and FWI values for the 50 th, 75 th, and 90 th percentiles (Table 2). The Initial Spread Index (ISI) was chosen as the most appropriate fire behaviour index to reflect the potential for quick changes in fuel moisture content, wind speed, and resultant fire behaviour. The ISI is derived through a combination of Fine Fuel Moisture Code (FFMC) and wind. During each of the match-drop tests and experimental burns we recorded wind speed, air temperature, and relative humidity using a Kestrel 3500 pocket weather meter. FPInnovations Page 10

11 Table 2. Percentile weather scenarios for the Nass Camp weather station. Percentile Wind Speed Fine Fuel Moisture Code Duff Moisture Code Drought Code Initial Spread Index Buildup Index Fire Weather Index Fuel Moisture Sampling We collected a fuel sample from the receptor fuels in the surface layer for each match-drop test in each separate fuel environment. We also collected a representative sample of surface fuel prior to each experimental burn. Samples were oven dried at 95 o C for 48 hours to determine the fuel moisture content. Fire Suppression Resource Requirements When we finished documenting each experimental fire, we instructed the BCWMB initial attack crew to contain the fire with the minimum amount of resources (personnel and equipment). We observed and documented the suppression tactics and the time required to prevent further spread of the fire. Comparative Fire Behaviour Analysis We compared the observed fire behaviour for these experimental burns with predicted fire behaviour for other wildland fuels commonly found in and along ROWs. We used the REDapp 1 fire behaviour calculator and entered the same FWI values recorded during the experimental burns. REDapp is a decision-support tool, which assists fire practitioners in evaluating fire potential and predicting fire behaviour. This tool incorporates the Canadian Forest Fire Behaviour Prediction (FBP) System (Hirsch 1996) to calculate fire behaviour outputs based on weather inputs and FWI values. For our fire behaviour predictions we used the S-3 fuel type (Coastal Cedar-Hemlock-Douglas-Fir Slash) to represent the slash fuels in the buffer zone, and the C-5 fuel type (Red and White Pine) to represent the adjacent standing timber (C-5 is typically used for fire behaviour predictions in the Interior Cedar-Hemlock Zone). We also made predictions for the fuel environment at the sampling site on the 5L61 ROW (Hvenegaard and Schiks 2013) using the Matted Grass (O-1b) fuel type at an 80% curing rate. We compared rate of spread (ROS) and head fire intensity (HFI) observed during the experimental burns to predicted ROS and HFI for other fuel types. We calculated ROS (m/min) by measuring the fire-spread distance and dividing by the spread time. Head fire intensity is defined as the rate of heat energy release per unit time per unit length of the fire front (Hirsch 1996) and is expressed in kw/m. 1 REDApp. The Universal Fire Behaviour Calculator. FPInnovations Page 11

12 HFI is a mathematically derived quantity; it cannot be measured directly. HFI can, however, be estimated by observing flame characteristics and comparing these to documented visual references of HFI (Alexander and De Groot 1988, Alexander and Lanoville 1989). We used these visual references to estimate the HFI for the line ignition of highest intensity and made relative estimates for the earlier line ignitions. RESULTS Fuel Load in the Chipped Fuel Bed The average fuel load (oven dried) of the chipped fuel removed from sample pits was 17 kg/m 2. Given that these samples were collected from the top 10 cm, it follows that the bulk density of the chipped fuel bed was 170 kg/m 3. The size class distribution of chipped fuel is outlined in Table 3. Table 3. Distribution of fuel particle size at the NTL ROW study site. Size Class 1 (<0.50 cm) 2 ( cm) 3 ( cm) Percent of Total 76.6% 13.6% 9.8% Ignition Probability and Sustained Flaming A period of unsettled weather preceded our study; cloudy weather and high relative humidity dominated the weather pattern. However, during the three days of ignition testing, the sky cleared, temperature increased, and relative humidity decreased. This drying trend contributed to lower fuel moisture, which resulted in more successful ignitions. We had 12 successful ignitions: 8 in the chipped fuels of the open ROW, 4 in the adjacent buffer zone, and 0 in the adjacent standing forest. A comparison of recorded weather values and fuel moisture measurements between the three test sites for the same ignition times showed two trends (Appendix A). First, the most favourable conditions for drying (high temperature, low relative humidity) were recorded in the open ROW. Conditions in the adjacent buffer zone were moderately favourable and in the standing timber, least favourable. Second, fuel moisture content was generally lowest in the open ROW and highest in the adjacent standing timber. Fire Behaviour We conducted experimental burns on the afternoons of September 5 and 6 when weather and fuel moisture conditions supported burning in the chipped fuels. As expected, more vigorous fire behaviour occurred during the peak of the burning day when fuel moisture content was lowest. We observed typical fire behaviour characteristics including elliptical growth patterns, accelerating spread rate, and increasing rate of spread and fire intensity with greater slope and wind speed. FPInnovations Page 12

13 Point Ignitions Initially, the point ignitions exhibited low intensity fire behaviour with slow rate of spread. As these fires moved through the acceleration phase, they grew in intensity and rate of spread until they reached equilibrium. This acceleration phase was about 10 minutes. Once a fire reaches equilibrium, the rate of spread remains steady provided that fuel, weather, and topographic factors remain constant. The point ignitions exhibited a typical elliptical growth pattern. The measured length-to-breadth ratio for these burns was somewhat less than what was predicted for a grass fuel type (Taylor et al. 1997). For the first two point ignitions, we measured the overall rate of spread from ignition to extinguishment. The rate of spread for these fires was very slow (0.03 and 0.06 m/min) (Appendix C). It was not apparent if the fire spread rate had reached equilibrium. The remaining ignitions exhibited slightly more vigorous fire behaviour and the spread rate in the later stages of fire growth ranged from 0.25 to 0.50 m/min. The rate of spread in the last point ignition was likely faster because the wind direction aligned with an uphill slope. Line Ignitions Relative to the point ignitions, the line ignitions exhibited more vigorous fire behaviour in the early stages of development. Where a point ignition goes through an acceleration phase, a line ignition achieves equilibrium rate of spread almost instantly in open fuel types. These ignitions were all conducted on the same day and we observed a dramatic increase in rate of spread and fire intensity as we moved into the peak of the burning day (Appendix B). Fuel moisture content and wind speed appear to be the most influential factors driving fire behaviour. This relationship can be seen in the increased fire behaviour with rising ISI. Surface Fuel Consumption Throughout the experimental burns, we observed superficial surface burning with minimal surface fuel consumption. The maximum depth of burn (Figure 8) was 5 cm. Figure 8. Duff-consumption pin indicating surface fuel consumption (i.e., depth of burn). FPInnovations Page 13

14 During our visit in July 2013 we speculated that only a shallow layer of dry surface fuel was available for consumption and that deeper layers were too moist for sustained burning. An analysis of one fuel bed moisture profile showed that the moisture content of the surface fuel was 11%, and at the 10 cm layer the moisture content was 56%. Potential Fire Behaviour in Other Wildland Fuel Types Table 4 summarizes the observed fire behaviour in the chipped fuels of the NTL ROW and predictions for fire behaviour in the O-1b (the 5L61 ROW), the S-3, and the C-5 fuel types. While the C-5 fuel type (Red and White Pine) is not modeled specifically for an Interior Cedar-Hemlock forest, the descriptions of stand structure, surface fuels, and ladder fuels closely resemble those characteristics seen in the standing forest adjacent to the ROW (Figure 7). The S-3 fuel type (Coastal Cedar-Hemlock-Douglas-fir Slash) is based on slash fuel resulting from logging of coastal species. The buffer zone adjacent to the ROW had a mix of slash fuels with a few small shrubs and pockets of heavy slash, but generally the accumulations of slash and organic layer were less than the volume described for the S-3 fuel type. Given the variation in the slash fuel volume, fire intensity in this zone will be variable as well. The predictions in Table 4 for fire intensity in the S-3 fuel type are likely at the top end of fire behaviour that would be encountered in the buffer zone fuels. Given the weather and fuel conditions measured in this study, fire behaviour in the standing forest fuel type will likely be low intensity (Rank 1) while the other fuel types will produce Rank 2 or Rank 3 fire behaviour. 2 The closed canopy of an Interior Cedar-Hemlock forest limits solar radiation from reaching the sparse surface fuels resulting in a relatively moist fuel environment. The grass component of the open 5L61 ROW would result in greater ROS and higher HFI than that observed in the open chipped fuel bed at the NTL study site. Table 4. Comparison of observed fire behaviour on September 6 and predicted fire behaviour. Time of Ignition Initial Spread Index Buildup Index Observed NTL ROW Predicted 5L61 ROW Predicted S-3 Predicted C-5 ROS HFI ROS HFI ROS HFI ROS HFI *ROS is measured in m/min and HFI is measured in kw/m. 2 The Fire Intensity Rank System enables firefighters to communicate a summarized assessment of fire behaviour. A description of the system can be found at FPInnovations Page 14

15 Suppression Challenges The five fires that resulted from the point ignitions were easily contained (i.e., further fire spread was prevented) by one firefighter with a backpack pump 3 (Figure 9). The largest of these fires observed under the lowest fuel moisture conditions grew to 9 m long with 21 m of perimeter. The short perimeter, low-intensity fire behaviour (Rank 2), and minimal depth of burn allowed for easy containment and extinguishment by one person with a backpack pump. Figure 9. A typical backpack pump consists of a neoprene water bag with a brass hand pump. The three line ignitions on September 6 were also easily contained with backpack pumps, but with increased fire intensity, fire size, and perimeter, suppression was more challenging. The fire at 1540 had the greatest fire intensity (30 cm flame length) and spread rate ( m/min). Even with these fire behaviour conditions and 49 m of fire perimeter, two firefighters were able to contain the fire s growth with backpack pumps in less than 5 minutes. Extinguishing the entire fire, however, was more difficult than expected because the water pump malfunctioned. A large portion of the mop-up 4 was done with backpack pumps and hand tools. Extinguishing a fire with a limited water supply is a slow and methodical process; mop-up on this fire required about two hours to accomplish. Weather Data Analysis The study site lies within the Skeena Fire Zone, which is in the Interior Cedar-Hemlock biogeoclimatic zone 5. This zone is strongly influenced by Pacific maritime weather systems that provide abundant rain 3 Backpack pump A portable water container equipped with a hand pump and backpack straps. Canadian Interagency Forest Fire Centre (CIFFC) Glossary of Forest Fire Management Terms 4 Mop-up is the act of extinguishing a fire after it has been brought under control. CIFFC Glossary of Forest Fire Management Terms 5 British Columbia Ministry of Forests brochure. Available: FPInnovations Page 15

16 and heavy winter snowfall. Typically, this area has high soil moisture during the summer due to slowmelting snowpack and frequent precipitation. However, in the Skeena Fire Zone received less than normal fall precipitation and winter snowfall. Early snowmelt in February and minimal precipitation in May and June resulted in higher than normal drought codes (DC), resulting in the burning of the deeper duff layers on some fires. 6 Our weather data analysis showed that the DC for the Nass Camp weather station was above the 90 th percentile on 45 of 192 days on which FWI values were recorded in Hourly weather data from Nass Camp for (Table 5) shows the changes in FWI values throughout the burning day and is a good indicator of potential fire behaviour. These hourly records indicate that the ISI values were above the 65 th percentile at the time of our study. It should be noted that recorded hourly weather values at the weather stations are an instantaneous measurement on the hour. We recorded the average wind speed and gust speed over the duration of each burn. Hence, the effect that on-site winds had on fire behaviour may be different than what is suggested by ISI values recorded at the Nass Camp weather station. Table 5. Hourly weather data and FWI values from the Nass Camp weather station. Date Time Temp ( o C) RH (%) Wind (km/h) FFMC ISI FWI Sep Sep Sep Sep Sep Sep Sep The FWI values determined in the percentile weather scenarios are an indication of the overall weather and fuel moisture conditions of this area. A comparison with FWI values from other weather stations in British Columbia and the associated weather percentiles shows the diversity of the biogeoclimatic zones across the province. For example, a weather data analysis (Hvenegaard and Schiks 2013) for the Mable Lake 2 weather station 40 km east of Vernon indicated that the ISI for the 75 th weather percentile is 5.7 compared to 2.8 for the Nass Camp weather station. 6 Personal communication with Tony Falcao, BCWMB. September 3, FPInnovations Page 16

17 DISCUSSION Changing Nature of the Chipped Fuel Bed As the chips become more compacted over time, aeration and drying of the fuel bed is reduced. This limits the depth of available fuel and reduces the potential fire intensity. In areas where the continuity of the chipped fuel bed is disrupted by wheel tracks and areas of mineral soil, fire spread will be interrupted. Regrowth of shrubs and herbaceous plants within the chipped fuels will likely retard fire propagation. Grass, on the other hand, can contribute to rapid rates of spread once it has cured. Although regrowth in deep chipped fuel beds is unlikely, patches of mineral soil may provide a receptive seed bed. The effect on fire behaviour will depend on what plant species recolonize these areas. Ignition Potential of the Fuel Environment Our match-drop test results clearly indicated a higher frequency of ignitions in the open ROW. Increased solar radiation and lower relative humidity contributed to lower fuel moisture content. Given the increased industrial traffic and the ease of access to the open ROW for recreational users, there is the potential for more ignition sources in this zone compared to the buffer zones and adjacent forest stands. Baxter (2002) found that ATVs can cause fires in grass. It is not unreasonable, therefore, that given the properties of the surface layer of a chipped fuel bed the same potential exists along the NTL ROW. Our match-drop tests showed successful ignitions in the open ROW when FFMC was low as 80. While this value may indicate a threshold for ignition, we have insufficient data to determine an ignition probability model for the chipped fuel environment. Fire Behaviour in a Chipped Fuel Bed We conducted experimental burns on the study site over a short period of time under low to moderate fire hazard conditions. The highest fire intensity and greatest fire growth occurred during the last line ignition, which was close to the peak of the burning day ( ). Fuel moisture content was 15% and winds were 6 km/h, gusting to 13 km/h. The ISI estimated for this time was 3.3. The fire behaviour we observed provides a benchmark for estimating fire behaviour under higher fire hazard conditions. For example, an increase in wind speed to 20 km/h would increase ISI to 5 (90 th weather percentile). Fire behaviour in chipped debris fuel environments has not been extensively documented and fuel models are not available to estimate fire behaviour. However, fire behaviour predictions in other open fuel types (e.g., matted grass) predict that an increase in ISI from 3 to 5 will double the rate of spread and fire intensity. By applying this to our observations, increasing ISI from 3.3 to 5 would produce a rate of spread of 3 m/min and a flame length of 0.6 m; this is equivalent to Rank 2 to Rank 3 fire behaviour. Comparison of Fire Behaviour in Adjacent Fuel Types A comparison of observed fire behaviour in the chipped fuel bed in the NTL ROW to predicted fire behaviour in the 5L61 ROW illustrated some differences in fire spread and intensity. Even though the grass volume in the 5L61 ROW was minimal, this fuel component contributed to a greater spread rate and intensity. The S-3 fuel type may not be a good representation of slash fuel accumulations in hydro FPInnovations Page 17

18 ROWs, but is more typical of fuels in the adjacent buffer zones. For purposes of comparison, the predictions for the S-3 fuel type presents fire behaviour conditions that could result in an extreme scenario of slash accumulation in the buffer zone. These comparisons suggest that the chipped fuel bed is a favourable alternative to either a grass-debris combination or slash in an ROW. Questions are often asked about whether the properties of a linear corridor make it a fuelbreak or a wick. The chipped fuel bed does provide some advantages for fire suppression operations on the NTL ROW and may allow crews to use the ROW as a fuelbreak. Ease of access and egress for firefighting crews is afforded by the relatively smooth, continuous chipped fuelbeds. In addition, the moisture content of the chipped fuels in the ROW responds quickly to water and crews can use this to create a barrier to fire spread. In the slash fuels of the adjacent buffer zone, fire behaviour will likely be of greater intensity than in the chipped fuel bed. The abundance of elevated surface fuels and the vertical structure of the slash fuels together create a fuel environment that dries more quickly and contributes to more intense fire behaviour. If a high intensity fire spreads from the slash fuels of the buffer zone into the chipped fuels of an open ROW, fire intensity may decrease sufficiently to allow crews to safely and successfully control the fire spread. Suppression Challenges At the time of the experimental burns, the fire hazard conditions were close to the 75 th percentile and the fire crew had no difficulty in controlling them. The amount of surface fuel that is available for consumption will influence fire intensity. Because only a thin surface layer was dry enough to burn, the fire intensity and rate of spread did not challenge the fire crew. However, deeper layers of dry fuels will increase fire intensity and may create fire suppression challenges. Sustained smouldering in the deep layers makes mop-up more difficult. The Drought Code (DC) is the FWI value that is used to indicate the moisture content and burning potential in the deep duff layers and large fuels. However, there seemed to be a disconnection between the moisture content we measured and observed in the deep chipped fuel bed layer (56% and wet to the touch) and the DC of 341 (Nass Camp July 18). Generally, a DC above 300 is considered the threshold at which the deep duff layers will burn and cause difficulty in control and mop-up. CONCLUSIONS The chipped fuel bed in the Northern Transmission Line right-of-way is a unique wildland fuel environment. Particle size, quantity, depth, and compaction all contribute to a fuel bed with moisture absorption and retention qualities unlike most other chipped fuel environments in linear corridors. In this study, the layer of surface fuel available for consumption was minimal and the deeper layers of chipped material were wet. Our comparative match-drop tests demonstrated that there is a higher frequency of ignition and sustained burning in the chipped fuels of the open ROW than in the buffer zone or the adjacent standing forest. Given the abundance of receptor fuels and increased potential for industrial and FPInnovations Page 18

19 recreational activity in the ROW, there is a greater probability of ignition in the chipped fuel environment. Observed fire intensity in the chipped fuel bed was lower than what was predicted (using the same weather and FWI values) for other fuel types (cured grass and slash debris) commonly found in linear corridors. At high fire hazard conditions, fire starts that spread into the slash fuels in the adjacent buffer zones will increase in intensity and will present suppression challenges. The observed fire behaviour from these experimental burns provides a benchmark for estimating fire behaviour at higher hazard conditions. The Initial Spread Index (ISI) reflects the primary drivers (fine fuel moisture content and wind speed) of fire behaviour in the chipped fuel bed. An increase in wind speed from 10 to 20 km/h will raise the ISI from 3 to 5 (75 th to 90 th percentile) and existing fire behaviour models predict that this will cause the fire intensity and rate of spread to double. However, data collected from more experimental burns will help researchers develop a fire behaviour model specifically designed for chipped fuel beds that would provide more accurate predictions. Questions remain regarding the changing moisture profile of the fuel bed and how the amount of available surface fuel may change over time. FPInnovations is interested in working with BC Hydro to conduct more sampling to further our understanding of moisture profiles and potential fire behaviour in chipped fuel beds. At this point in time, the quantity and nature of vegetative regrowth in the ROW is uncertain. The change in vegetation should be monitored and its effect on fire behaviour evaluated. This study has increased our understanding of ignition potential and potential fire behaviour in chipped fuels. While there is a risk of ignition, the overall fire behaviour potential does not exceed other typical fuel environments in linear corridors. The measures outlined in Schedule 3 of the Restrictions on High Risk Activities in the British Columbia Wildfire Act (2005) are appropriate for industrial operations in the chipped fuel environment. Because industrial crews working in the ROW are trained in basic fire suppression and are equipped with firefighting hand tools and water delivery equipment, they should be able to control small fire starts in the chipped fuel bed. Industrial operators should continue a business as usual approach to working in the NTL ROW and exercise ongoing awareness and diligence to fire preparedness and immediate response to fire starts. FPInnovations Page 19

20 REFERENCES Alexander, ME; De Groot, WJ Fire behavior in jack pine stands as related to the Canadian Forest Fire Weather Index (FWI) System. Can. For. Serv., North. For Cent., Edmonton, AB. Poster (with text). Alexander, ME; Lanoville, RA Predicting fire behavior in the black spruce-lichen woodland fuel type of western and northern Canada. For. Can., North. For. Cent., Edmonton, Alberta, and Gov. Northwest Territ., Dep. Renewable Resour., Territ. For. Fire Cent., Fort Smith, NT. Poster (with text). Beverly, JL; Wotton, BM Modeling the probability of sustained flaming: predictive value of fire weather index components compared with observations of site weather and fuel moisture conditions. International Journal of Wildland Fire 16: British Columbia Wildfire Act [online]. B.C. Reg. 38/2005. Queen's Printer, Victoria, BC. Available: Hirsch, KG Canadian Forest Fire Behavior Prediction (FBP) System: user s guide. Nat. Resour. Can., Can. For. Serv., Northwest Reg., North. For. Cent., Edmonton, AB. Spec. Rep. 7. Hvenegaard, S; Schiks, T Mulched fuels and potential fire behaviour in BC Hydro rights-of-way. FPInnovations Wildfire Operations Research, Hinton, AB. Project Report. Available: Kane, JM; Varner, JM; and Knapp, EE Novel fuelbed characteristics associated with mechanical mastication treatments in northern California and southwestern Oregon, USA. IJWF 18: McRae, DJ; Alexander, ME; Stocks, BJ Measurement and description of fuels and fire behavior on prescribed burns: a handbook. Environ. Can., Can. For. Serv., Great Lakes For. Res. Cent., Sault Ste. Marie, ON. Inf. Rep. O-X-287. Schiks, T Modelling the probability of sustained ignition in mulch fuel beds. Available: Schroeder, D; Russo, G; Beck, J; Hawkes, B; Dalrymple, G Modeling ignition probability of thinned lodgepole pine stands. For. Eng. Res. Inst. Can. (FERIC), Vancouver, BC. Advantage Report 7 (12). Taylor, SW; Pike, RG; Alexander, ME Field guide to the Canadian forest fire Behavior Prediction (FBP) System. Nat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, AB. Spec. Rep. 11. Van Wagner, CE Development and structure of the Canadian Forest Fire Weather Index System. Agriculture Canada, Canadian Forest Service, Ottawa, ON. For. Tech Rep. 35. FPInnovations Page 20

21 APPENDIX A: MATCH-DROP TEST RESULTS Site Date Time Temp ( o C) RH (%) Wind (km/h) Cloud Cover (%) Shaded Fuel Moisture (%) FFMC * Success Open ROW Buffer Zone In- Stand Zone Sep 4 Sep 5 Sep 6 Sep 4 Sep 5 Sep 6 Sep 4 Sep 5 Sep N N N N N Y G 5 80 N Y G 6 20 N Y G 5 30 N Y G 10 0 N Y G 11 0 N Y G 11 0 N Y G 10 0 N Y N N G N N N N N N G 9 20 N N G 2 30 N Y G 18 0 N N G 12 0 N Y G 8 0 N Y G 9 0 N Y Y N G Y N Y N Y N Y N Y N G 3 0 Y N G 4 0 Y N Y N G 3 0 Y N * FFMC is the hourly fine fuel moisture code calculated from the Nass Camp Weather Station. FPInnovations Page 21

22 APPENDIX B: POINT IGNITIONS AND FIRE BEHAVIOUR DATA Weather and Fuel Conditions Fire Behaviour Fire Containment Date Time Temp ( o C) RH (%) Wind (km/h) Fuel Moisture (%) Initial Spread Index Spread Rate (m/min) Flame Length (m) Growth Time (min) Overall Length (cm) Width (cm) Length/ Breadth Ratio Perimeter Length a (m) Sep G b Sep G b Sep G c Sep G c Sep G c a Calculated using an online calculator b Overall spread rate from ignition to extinguishment c Actual spread rate measured after 10 minutes of acceleration FPInnovations Page 22

23 APPENDIX C: LINE IGNITIONS AND FIRE BEHAVIOUR DATA Weather and Fuel Conditions Fire Behaviour Fire Containment Date Time Temp ( o C) RH (%) Wind (km/h) Fuel Moisture (%) Initial Spread Index Spread Rate (m/min) Flame Length (m) Growth Time (min) Overall Length (cm) Width (cm) Perimeter Length b (m) Sep G Sep G Sep G a Line ignitions were 5 m. b Estimated FPInnovations Page 23

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