Examining Post-Fire Water Contamination in the Wildland Urban Interface

Wildland urban interface (WUI) fires are occurring with greater frequency throughout the world, and these fires are responsible for widespread damage to structures and infrastructure in many communities. Most community resilience efforts tend to focus on mitigating the damage to buildings and vegetation. However, recent WUI fires involving post-fire water contamination have shifted some of the focus to damaged water distribution systems.

The Tubbs Fire (2017) in northern California, and the Camp Fire (2018) in Paradise, California are among the first known WUI fires where widespread contamination was discovered in the water distribution network but not in the source water after the fire. Following these fires, benzene, naphthalene and other volatile organic compounds (VOCs) were measured at harmful levels in community water distribution systems. The presence of these VOCs within water distribution systems following a WUI fire is especially concerning for human health.

Initial studies have hypothesized that contamination could be the result of three scenarios:

1. The degradation of plastic materials within water distribution systems
2. Back siphoning of contaminated water through damaged plumbing
3. Contaminated air and/or ash being sucked into the distribution system as it depressurized

In this study, the Fire Safety Research Institute (FSRI), part of UL Research Institutes examines post-fire water runoff and smoke condensate samples to identify VOCs that are present. Samples are collected during full-scale and room-scale experiments that are conducted both outdoors and within structures. Different household products and/or vehicles are involved in most experiments to determine the source of the contaminants identified in the samples. Throughout this project, FSRI is working with collaborators from Oregon State University, University of Colorado Boulder, and University of Minnesota to conduct analysis.

Context

During fire incidents, suppression water run-off, suppression agents, smoke condensate and rainfall over ash and soot can contaminate water sources and distribution systems. WUI fires involve structures with household products and vehicles that are part of the fuel and release additional chemicals into the water runoff. Further research is needed to understand the source of these post-fire contaminants when structures and vehicles are involved. 

Research Objectives

Findings in this study will support community resilience efforts during the recovery from WUI fires. Through its research, FSRI seeks to:

• understand the source and specific VOCs that may contaminate water distribution systems during fire events.
• investigate potential mechanisms for systemic contamination from WUI fire smoke and/or ash being pulled into the water distribution system as it is damaged by fire conditions and potentially depressurizes.
• understand what contamination occurs with the heating and degradation of water distribution system components.