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Lessons Learned from an RX Burn

On the evening of Tuesday, November 1st, I got the text message no prescribed burn manager wants to get. “Looks like your fire isn’t out.” I had just gotten home from the burn, frantically thrown off my smokey clothes, showered off the soot, and changed to head back into town for a meeting. Guess that’d have to wait. I scrambled back over to Bloody Run County Park, where I found that indeed, the fire wasn’t out. I had assumed, as is sometimes the case, that someone had called in a smoldering snag still blazing, but my heart sank when I saw otherwise.

Timber burns are a little different than prairie burns. A large “snag,” or standing dead tree, may smolder for quite some time after the fire on the ground has gone out. As long as the surrounding vegetation is burned out, and the snag can’t fall or throw an ember out of the fire line, it’s a perfectly acceptable part of the process.

Snag burning in the black

But in this case, the actual ground fire was still going. It had escaped through a weak point in the fire line and slowly crept along the forest floor, eventually adding about 3.5 acres to our intended 10-acre burn.

View from the far end of the campground

A small part of the escape crept into the adjacent DNR-managed wildlife area, which I was able to put out with a rake. The rest of the escaped fire was burning county ground when the McGregor Hook and Ladder arrived with more manpower and water to extinguish the remaining flames. My first feeling is embarrassment. I have spent a lot of my time as the county natural resource manager extolling the virtues of timber burns, and Bloody Run is one of our finest case studies. So to have that case study tarnished by an escape, even if not a severe one, bruises my ego and will doubtlessly make it harder for me to make my case going forward that these practices are necessary and beneficial. My second feeling is regret. On burn day, as we’ve done for 9 previous successful burns at Bloody Run, I cleared a line down to mineral soil through the leaf litter and duff along the perimeter. At the time, I wasn’t entirely comfortable with the line and would have preferred to make another pass. However, having looked at the hourly weather, I knew things would get more volatile in the afternoon. So I had a choice to make. On the one hand, we could ignite now (11:30 AM), and take advantage of the full complement of personnel on hand (5 people) to contain the burn perimeter; once the perimeter was black, the chances of escape drop dramatically. Or, I could make another pass on the lines and ignite when conditions would make containment much more difficult in the event of an escape.

Map of firebreaks & ignition strategy

In the end, we felt we had made the right decision. We were able to get a high-quality burn through. In the past, we’ve had to extinguish the flames early due to time running out; in this case, the target area was consumed by 2:30 PM. All personnel spent the next 75 minutes felling burning snags, extinguishing smoldering logs near the perimeter, and duffing off the line once more. We felt after “mop-up” that the burn was successful with a low chance of escape, and departed by 3:45.

I got the fateful alert at 5:30 PM. Somewhere in that intervening 105 minutes, the escape occurred; based on the observed rate of spread during the intended burn and my arrival, there was likely some lag time before things started up again.

Perimeter of burned area; note that digital map does not match on the ground boundaries

With prescribed burning, there’s always some chance of escape. Of the tens of thousands of prescribed burns executed each year nationwide, approximately 16% escape. What we do as fire managers is try to minimize that likelihood. There’s even a web database of these incidents from which fire managers can learn from each other’s experiences. I’d like to take a moment to talk through what we do leading up to a prescribed burn to make sure it meets our goals in the safest possible way. First, we start with the prescription: the prescription lays out the conditions necessary to execute the burn.

This prescription includes weather data, the location of firebreaks, the fuel moisture levels, the personnel and equipment required, hazards, and all manner of other checklist items. It also includes our goals for the burn – suppress woody species, stimulate grasses and forbs, etc.

The prescription also lays out communications: chain of command, and parties to notify in advance of ignition. That list includes neighboring landowners and Clayton County dispatch, who in turn text the fire chiefs. There is not, however, a template to fill out to determine the best prescription. That requires some more experience and study specific to the site.

When we started burning at Bloody Run, I explored the temperature, humidity, and fuel moisture levels required for oak leaf litter to combust. We did our first burn with only theoretical knowledge, and our prescription has been fine tuned with each subsequent field experience. The conditions on Tuesday met the criteria that have allowed for successful, safe burns in the past. Getting a good timber burn requires very dry conditions, and it’s not surprising that a lot of the social media commentary questioned the wisdom of burning in such conditions. Clayton County was not then, nor is it now, in a burn ban.

Burn bans are established when the majority of fire chiefs in the county agree to the need, and request the state fire marshal to issue the ban. With no such ban in place, and the conditions met for our prescription, we decided to go ahead with the burn.

That’s the thing I’d most like to clear up: this was not a careless, thoughtless exercise. We have established the necessary prescription and adapted it to the changing conditions as each fire has done what it’s supposed to do to the fuel composition.

Obviously, we will be adapting that prescription again following this learning experience. Some new parameters will be established for cleaner fire breaks, more hazard tree cleanup ahead of ignition, and a more thorough mop-up process before walking away from the burn.

On the brighter side, nothing burned that couldn’t handle it.

Burned area of Bloody Run WMA (DNR property)

In fact, our stewardship plan for Bloody Run developed by professional foresters recommends a burn for the areas that unintentionally got burned; we simply never thought the conditions would allow that fuel to ignite. Now we know it can, and we can use that information for the better in the long run.

Leaf litter fires have long been a part of Iowa wildlife’s evolutionary history. They would have had ample time with the rate of spread, and the low intensity, to weather the event. The native vegetation will likely be grateful; garlic mustard and Japanese barberry have low tolerance to fire, but our native grasses, sedges, and forbs will bounce back even better.

Flame height: ~8-12", rate of spread ~2-3' per minute

In the end, fire is an efficient but touchy tool in the restoration kit. It is extremely regrettable that we failed to adequately contain it in this circumstance, and that we had tired firefighters and a fine to pay as a result. But it’s difficult to learn in life without mistakes, and the only way to avoid making mistakes is to avoid doing anything at all – we’ve learned that in Iowa’s oak woodlands, doing nothing at all can often be as bad as doing too much.

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