The Marshall Fire

On December 30, 2021, the Marshall Fire, a wind-driven wildfire swept through the City of Louisville, the Town of Superior and unincorporated areas of Boulder County, Colorado, burning 6,219 acres, destroying nearly 1,100 homes and businesses, and claiming the lives of two people. The Marshall fire is considered to be the most destructive in Colorado’s history with over $2 billion in losses.

Two of our expert teams were deployed to the incident to conduct (1) a detailed post-fire forensics investigation to determine the origin and cause of the incident, and (2) a wildfire risk assessment to evaluate building performance during the fire, in addition to identify the breath and range of physical, environmental, social and regulatory vulnerabilities that contributed to the devastating losses experienced in the impacted communities.

Our forensics experts, retained by the Boulder County Sheriff and District Attorney’s offices, performed witness interviews, on-site observations of the fire scene and fire patterns, researched location and types of ignition sources in the area as well as applicable weather data; and reviewed photography and video of witnesses and/or automated camera systems. The investigation gathered and considered all evidence and data, considering veracity and assembled an incident timeline. We then developed a list of possible cause hypotheses of the fire and offered opinions regarding the origin and cause of the fire, and the role played by the electric utility.

For the wildfire mitigation assessment, our team of experts collected hundreds of on-the-ground observations and evaluations of damaged and undamaged homes and commercial structures, along with inspections of individual building components, systems, and materials. The team also conducted numerous interviews with state and local first responders, building officials, planning departments, residents, and other agencies, as well as evaluated numerous technical reports developed from by other partners such as NIST and IBHS.

Our research uncovered the hazardous combination of high winds known as a “Mountain Wave” with wind speeds of 50 to 60 mph with gusts up to 80 to 115 mph significantly damaging vulnerable power sources near ignitable and mixed natural vegetation. In addition, long-term drought, high temperatures and local resident activity unexpectedly created coincidental ignition sites in tandem.

While utility-specific wildfire safety regulations, guidance and practices have been adopted in the State of California, where several utility-related wildfires have caused catastrophic losses, the development and adoption of similar standards and practices has not yet occurred more broadly at a national or international level.

Similarly, for the built environment, wildfire/WUI safety codes and standards, guidance documents and programs already exist at the national level (e.g., IWUI code, NFPA 1140) and at some state and local levels (e.g., California Building Code Chapter 7A), however the adoption, customization and enforcement of these codes and standards, policies and practices are limited.

Beyond codes and standards, the incident highlighted the need for more holistic approaches to wildfire resiliency – the need for actions to be taken at community, neighborhood, subdivision, parcel and building scales that encompass the disaster life cycle: preparedness, planning, response, mitigation, and recovery.

In addition, utilizing structure density and fire separation to limit urban conflagration, performing fine-scale hazard, risk and vulnerability assessments and mapping, coordinating mitigation for multiple hazards, and adding better vegetation management policies and practices for wildland spaces, communal open spaces, greenbelts and integrated recreational areas are all areas that show opportunities for improvement for this incident.

The results of this investigation and mitigation assessment are now used to inform improvements to building/fire codes and standards, best practices, guidance documents and other policies on wildfire preparedness, prevention, mitigation, recovery and rebuilding. Through the Building Science Disaster Support program (BSDS) of the Federal Emergency Management Agency (FEMA), the observations and recommendations from the incident have resulted in the development of several mitigation assessment team (MAT) products such as:

• Recommendations to improve codes and standards, guidance documents and programs.
• Recommendations for code adoption, customization, and enforcement.
• Detailed fact sheets for homeowners, builders and design professionals addressing structural hardening, defensible space, multi-hazard considerations, subdivision planning, detailing and joints, smoke and ash infiltration.
• Training and outreach presentations and workshops.
• Marshall Fire Technical Report.

Our wildfire risk mitigation team continues to work with our STARR II partners, FEMA and other federal/state/local governments, non-profits, and private sector clients to better understand, prepare for, respond to and recover from future wildfire threats, particularly at the wildland-urban-interface. This includes providing community wildfire protection plans, utility wildfire mitigation plans, community outreach, education and training for enhanced wildfire resiliency planning and implementation for planners, engineers, designers, builders and the public at large.