Is your infrastructure fire-resilient?
In recent years western states have been at the center of wildfires that have burned countless homes in just days. In the aftermath of these fires, miles of drainage pipes have been compromised. Melted pipes have caused sinkholes, closed roads, and put city residents on notice for possible roadway collapses during heavy rains. It’s clear the effects of wildfire can go much deeper than what we see on the surface.
Water run off/flooding
According to The National Oceanic and Atmospheric Administration (NOAA), in each of the past seven years (2016-2022), the United States has experienced a major wildfire event with damages averaging over 13 billion dollars per event.
NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters (2023).
Most pipes are buried with several feet of earth cover over the top protecting them from direct contact with surface fires. However, every drainage system also has several exposure points that need to be accounted for. Culverts, by definition, will almost certainly have two ends exposed at surface level (so long as they are not permanently submerged). If fire resilience is a priority, these end sections should be designed to withstand contact with flames and high radiant temperatures. Storm sewers are open to the surface at every inlet of the system. These access points potentially put underground systems at risk.
Aside from the obvious wildfires, there are several other avenues that can introduce fire into a drainage system.
Routine ditch burnings
Routine ditch burnings that are common in many communities to manage excessive vegetation introduce fire risk to any culvert or storm sewer that outlets into a ditch.
A simple cigarette butt or firecracker
A simple cigarette butt, firecracker or hot charcoals from tailgating dropped into a storm sewer grate can ignite dry leaves in the bottom of a catch basin and create a chain reaction in storm systems beneath our feet.
Fuel spilled on a roadway will naturally flow into some type of drainage system. If that fuel ignites, buried pipelines could be compromised.
The most obvious threat to a pipeline from a fire is the potential to ignite the pipe material itself. To address this concern properly, it’s important to understand that there are differences in how different pipe materials respond to exposure to flames. The table below shows concrete compared to alternative materials and the temperatures which induce ignition and melting. Note that concrete is classified as non-combustible material by the National Fire Protection Agency, fulfilling the requirements set by ASTM E136.
If fires cause a culvert or storm sewer to burn, there are a number of issues that can arise. A burnt-out culvert can certainly lead to immediate collapse, causing disruptions on the surface above, but some of the secondary effects may be even more severe. After a culvert or storm sewer is burnt out, it leaves behind a cavern of dirt beneath the ground. Rainfalls that follow a drainage burnout can cause catastrophic damage to entire communities as the water quickly erodes roadways, foundations, and other infrastructure from beneath the ground. This is particularly hazardous following a wildfire since the loss of above-ground vegetation can create additional severe flow conditions more than normal. Roadways that are adversely affected by these washouts and/or collapses may affect critical access roads, making it difficult or nearly impossible for residents to evacuate or for first responders to access the communities directly affected by the fire. The ensuing chaos resulting from a burnt pipeline makes clear the importance of building fire-resilient infrastructure.
The solution to these problems is relatively simple: for pipes that may be exposed to flame or high radiant temperatures during their service life, utilize pipe materials that are unaffected by those conditions. From that standpoint, it is only reasonable to avoid the use of alternative materials in those settings. At a minimum, it is recommended that culvert or daylighted storm sewer end sections are comprised of non-flammable materials.
For a fully resilient solution, reinforced concrete pipe (RCP) is the most universally trusted material for drainage pipes in the face of a wide range of natural threats – particularly wildfires. As mentioned previously, concrete is inherently a non-combustible material and can effortlessly handle short-term exposure to flames or extreme temperatures with virtually no risk to the structural integrity of the buried system. Specifying and utilizing RCP on your projects helps build more resilient communities and future-proof our infrastructure.
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