Wildland Fires

Wildland fires cause enormous damage every year in the United States. In 2006, there were more than 96,000 wildland fires that burned nearly 10 million acres. Approximately 85% of the wildland fires in 2006 were attributed to human activity. The increase in wildland/urban interface is often blamed for the increase in wildland fire incidents.

Careless human activity—for instance, campfires and the use of vehicles and powered tools—often starts small fires that can quickly transition into major incidents if the fuel and weather conditions are right. Additionally, arson remains a major concern for law enforcement agencies. Exponent has assisted law enforcement agencies with our expertise and advanced analytical techniques to assess physical evidence obtained during wildland fire investigations.
Commercial operations in wildland/urban interfaces need to use extraordinary care to prevent instances where a small fire on their premises results in damage to thousands of wildland acres. In many instances, a minor lapse in fire prevention procedures can be used to allege liability for starting the fire. Power utilities operating transmission lines over thousands of miles of wildlands, and power-generating stations in remote areas, are especially exposed to this risk. 

As with any fire investigation, determining the origin of a fire is the first step in wildland fire investigations. Wildland fire behavior is substantially different from structural fires in terms of fuel load, wind conditions, topography, the size of the fire and its effect on the direction and rate of fire growth and travel. Movement and intensity patterns are also typically different from those found in structural fires. Exponent’s experienced wildland fire investigators can assist in conducting scientific origin determination. 

High-voltage transmission lines in proximity to vegetation are often identified as the cause of wildland fires. However, high-voltage lines can arc to ground only over a finite distance. This distance is increased in the presence of flames and smoke. At times, arcing can occur between conductors in the presence of fire and smoke, instead of between conductor and ground. Thus, the presence of arcing evidence alone does not necessarily support a conclusion that the arcing started the fire. 

Exponent uses detailed site inspections and accurate mapping of the area of origin using advanced laser-based tools to obtain an accurate estimation of the air gap between transmission lines and vegetation. The capture of transmission data leading up to the fire provides crucial evidence regarding the nature and timing of the arcing. Our staff has also developed analytical tools that estimate the actual distance over which an arc can occur under specific conditions of the transmission line and the nature and geometry of the electrical ground. 

We utilize state-of-the-art computer simulation packages that allow the assessment of fire growth for given fuel loads, weather conditions, topography, and suppression activities. 

Exponent has investigated the cause and origin of wildland fires for numerous power utilities and process industry facilities. The multidisciplinary nature of Exponent’s teams enables the coverage of all aspects of these complex investigations. Our fire and explosion team determines the origin and coordinates the activities of additional resources. Our electrical engineers assist in analyzing electrical ignition sources. Our civil engineering and environmental practices assist in the detailed surveys of area of origin, aerial surveys of the burn damage, and preparation of GIS data for computer simulations. Our ecological practice can assist in the assessment of damage and consult on rehabilitation of the burned areas. Exponent engineers and scientists also have expertise in remote sensing and photogrammetry. 

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