Behavior of Service Lateral Pipes during Wildfires: Testing Methodologies and Impact on Drinking Water Contamination

Abstract

Wildfires have damaged civil infrastructure throughout wildland urban interface communities, including water distribution systems. Post-wildfire, communities have detected volatile organic compounds (VOCs) within drinking water systems. This paper focuses on the behavior of service lateral pipes used for potable water under fire conditions, with an emphasis on testing methodologies and impacts on drinking water contamination. The authors tested commonly-used service lateral pipes (type L copper, galvanized steel, schedule-40 PVC, and STIR-7 HDPE) at elevated temperatures to determine critical threshold temperatures at which these pipes thermally degrade. This paper summarizes tests evaluating type L copper, galvanized steel, schedule-40 PVC, and STIR-7 HDPE pipe materials at elevated temperatures and numerical simulations to examine fire scenario characteristics that may thermally degrade pipes. Post-heating treatments of the pipes were considered (spirals, small pieces, and whole sections) to examine the influence of different testing methodologies on the contamination levels found in water, primarily how the surface area exposed influences the concentration of contaminants during a fire. Water was analyzed following EPA 524.2, and regression curves were fitted to the results to quantify the threshold temperatures at which pipe materials may release VOCs exceeding federal limits. Practical metrics, including wildfire conditions (heat flux and burn duration) and pipe burial depths, were varied to investigate under what circumstances buried service laterals may exceed threshold temperatures. From the series of tests performed, the authors conclude that neither galvanized steel nor copper released VOCs exceeding the federal limit at the highest tested temperature (300 °C) and that the threshold temperatures for PVC and HDPE were 194 and 254 °C, respectively. Additionally, results show that the surface area of pipe materials tested does affect contamination levels; however, regardless of the surface area tested, the heating of relatively short lengths of pipe (less than 3.25 m) can release contaminants exceeding federal limits.

Oregon's Unprecedented Labor Day 2020 Fires: Impacts and Response

“…Plastic pipes, such as those made of high-density polyethylene, polyvinyl chloride (PVC), or cross-linked polyethylene, are commonly used because they are affordable, durable, and ductile during a seismic event. During a fire, these pipes will be heated above their operational temperatures and will often begin to leach VOCs into the water distribution system (Metz et al 2023, Isaacson et al 2021. In addition to the 2020 Labor Day fires in Oregon, recent wildfires such as the 2017 Tubbs Fire and 2018 Camp Fire in northern California and the 2021 Marshall Fire in Boulder County, Colo., released VOCs into drinking water distribution systems.…”