Peat fires are unique and challenging in Minnesota winters

Peat fires are unique and challenging in Minnesota winters

26 January 2012

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USA — Gully, Minn. — Peat fires can be a common occurrence during a dry Minnesota summer. They are normally rare in the middle of the winter, but this season may be an exception.

The winter peat fire Dec. 26 near the town of Gully in Polk County, which was ignited by a surface fire in grass and brush, is an example of the increased challenges faced by the Department of Natural Resources (DNR) and local fire fighters. They battled cold, wintery conditions to control the fire before ultimately putting it out.

“It’s unusual for us to be battling a peat fire at this time of year,” said Brian Pisarek, DNR Northeast Region program forester and peat fire expert. “The lack of precipitation this fall made conditions just right for something like this to happen.”

There have been several other wildfires that resulted in peat ignition in northwestern Minnesota from fall through early January. That’s a testament to the unusual weather conditions in Minnesota recently.

Flooding the burning peat, or using peat nozzles attached to a hose, are the most efficient and effective ways to extinguish a fire, and the least disruptive to the area soils and vegetation. Flooding consists of building a dike around the fire and using large irrigation pipes to completely cover the ground in water. Peat nozzles, designed much like a metal garden wand, are inserted under the peat to shoot high-pressure streams of water into areas where the peat is burning underground.

Battling winter peat fires by flooding or with peat nozzles can be difficult. That’s because accessing nearby water and keeping water pumping equipment from freezing before and during delivery of the water to the fire can be challenging. Water doesn’t flow well when air temperatures are in the teens or single digits.

“Normally, we can find a nearby water source in a ditch or neighboring pond or lake,” explained Dana Carlson, Warroad area forest supervisor. “But in the winter, and with the drought conditions, it can be difficult to access available local water sources. That can cost us fire-fighting time, and require a greater amount of manpower and resources to haul water from greater distances.”

Other common tools used to extinguish peat fires are excavators and dozers. Heavy equipment is used to mix burning peat with deeper layers of soil that still contain moisture. The equipment breaks up the burning particles, mixing, cooling and sealing the peat off from oxygen so it is no longer able to burn. Tillage equipment can also mix surface snow or applied water to help extinguish burning peat.

Areas of peat are found throughout Minnesota. Peat is an accumulation of partially decayed plant material, often found in wetlands or areas that had been wetlands at one time. It can accumulate to a depth of from 20-30 inches to several feet in deep bogs. Peat soil generally absorbs moisture, but unusually dry conditions, such as those Minnesota is experiencing this winter, can desiccate the upper peat layers and increase the potential for peat soils to burn. Ironically, when peat is extremely dry it becomes hydrophobic, meaning it actually repels water.

Peat fires pose are dangerous to extinguish because the fire smolders beneath the ground as a glowing combustion rather than as an open flame. Windy conditions can cause peat embers to pop up to the surface and ignite surrounding frozen, dry vegetation. Firefighters are at risk of severe burns on their feet and legs if they fall into subsurface pockets of burning peat. The heavy, dense peat fire smoke can lead to respiratory problems in people and livestock. It also has caused vehicle crashes in low-visibility driving conditions.

The Dec. 26 peat fire has been extinguished, but the area is being monitored by DNR foresters. Unchecked, peat fires have the potential to last for years during cyclic dry periods.

With little fall precipitation, warm winter temperatures and scarce snow cover, an unusual winter fire season is upon us, and spring may come in “like a lion” in a few months.

According to the Minnesota climatology office, “without ample, widespread precipitation in the late winter and early spring, the state will face deficient soil moisture supplies and low water levels in wetlands, lakes and rivers.” Additionally, areas with a hard deep frost and lack of snow cover will experience increased runoff in the spring, resulting in less groundwater recovery. It is anticipated this will contribute to control problems if fire ignitions do occur.

“It would be extremely helpful to get much needed winter moisture followed by a nice slow melt,” Pisarek said. “We firefighters would all sleep better at nights – at least through the next few winter months.”

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