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Mop Up Question

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  • Mop Up Question

    Looking for some input from those more experienced with timber fires as to what is considered "enough" mop up. We're in the prairie, so most of our wildland fires are grass and field fires where there's not much left smoldering to worry about mopping up, and it's pretty easy to drive a truck around a field to wet things down. However, we recently had a fire in some timber that resulted in some very divided opinions. Some felt that we stayed on scene much longer than we needed to doing mop up operations (which take much longer in timber than in a field), while others felt it was necessary to ensure that fire didn't spread after we left. I'll try not to tip my hand as to my opinion.


    4-5 acre fire in hardwoods started by open burning. A few steep but shallow (20-30 foot max) ravines. After the fire was contained (which didn't take long), we still had quite a few stumps and garbage (several large garbage piles at the bottom of the ravines) smoldering throughout the area. Winds were fairly calm during containment, but right at dusk the wind kicked up slightly and we soon had stumps that had been smoldering now burning openly throughout the black area. Forecast was for 5-10 mph winds overnight, I think gusts ended up being more than that (was shaking the siding on my house), but I'm not sure.

    In a "small fire" situation like this, what's the "appropriate" level of mop up? Soak every smoldering stump until it's for sure out, just focus on the 20' or so around the perimeter, or something in between? We're primarily a structural department and as I mentioned the large majority of our wildland fires are field fires, so out folks don't have much experience in timber fires. Is there a rule of thumb to use based on forecasted wind speed? Does the onset of dark become a factor? Any thoughts are appreciated.

    Thanks in advance,


  • #2
    Too many variables for any one answer - first - how receptive were the fuels outside the line ? If it did get out would it be a problem? How accessable were the hot spots ? Could you do a thourough job ? Or would you just be delaying a re-kindle ? Sometimes the best use for water on a mop up is for drinking while you are letting things take care of them selves. Does the RH pretty much always go up after dark in your area ? A lot of stuff is experence and seat of your pants guessing.
    The only hard fast rules I can give you are - if the un burned area is lighter type fuels - mop up a little deeper, also anything above knee high burning gets more attention than stuff on the ground. The garbage you mentioned was in a ravine ? proably best to let it burn - garbage pits are a good place to get hurt and or breathe some crap - (no one wants to hike into the woods packed up) - if I have the water and man power and I am spooked by whats down wind , 60 to 75 feet in is a good distance in to mop up cold. Any deeper and you will wear out both hose and men. Sorry I couldnt be more specific, but a lot depends on your area and resourses.


    • #3
      We experience a number of fires in woods and timber stands each year. Most of the fire occurs in either pine stands with some in mixed pine and hardwoods stands.

      We do have the luxury of being able to get a Forestry plow on just about every fire. Once the plow has made a line, we inspect the area around the line for any trees that could fall and create slopover. We also break up and knockdown any fire in all the stumps burning within 10-20' of the line, depending on wind conditions. We will often leave much of the stumps and other residual fire in the center of the fire burning as manpower simply isn't available for complete extinguishment. The vast majority of the time fires burning underground is not a tremendous issue for us.

      If we are unable to get a plow on the fire, we are much more detailed in regards to extinguishment. As a rule, everything within about 30' of the edge of the fire will be extinguished and depending on wind, we will cut a 4-6' line on the downwind side and a 2-4' line on the upwind side. heavy stumps and logs burniong in the interior will get broken apart and extingushed and all burning trees will be dropped and opened up.

      We much prefer fires where we get a plow.
      Last edited by LaFireEducator; 03-31-2011, 05:36 PM.
      Train to fight the fires you fight.


      • #4
        My opinion, That small of a Fire needed 100% mop up. But working with VFD i can understand not Girding and cold trailing. 4-5 acres is pretty small, one engine could handle that in about 2-3 hours depending on variables.

        Any thing that is Flaming need to be put out and broken up, Major smoking stumps need to be dug and cleaned out, especially close to the line. Drop any trouble tree's or anything that will be a hazard.

        If not, Mop up 2-3 chains for winds under 10-12MPH
        3-4 for anything over 15 MPH.
        5-6 for anything higher up to 25MPH
        Courage, Being Scared to Death and Saddling Up anyways.


        • #5
          my agency's current policy on mop-up is 100 feet in (for larger fires (we're talking bigger than 10 - 20 acres here)) or 100% (especially for interface fires)
          IF you can, i would try an bust up any smoking stumps and drown them well, a wetting agent or foam works well in mop up, hazard trees close to the fires edge should be felled (if it can be done safely), break up and scatter piles to reduce the heat buildup

          darkness will allow you to see anything still flaming or glowing more easily, but makes many other hazards much worse.
          I would definitely consider wind speed and direction, as well as forecasted weather conditions (hot and dry, rainy, etc) as to how much mop up you may need, and anticipate coming back out the next day to recheck your fire (and continue mop up)

          and as LA said, contact your state Forestry agency, see what resources they have that can assist you. I work for Forestry, and Im more than happy to help mop up after I've plowed a fireline, knocking down snags, busting up stumps and scattering piles is so much easier with my dozer than by hand, as well as I can create or improve access to the fire to get brush trucks in to complete mop up
          "If you can't be a good example, the you'll just have to be a terrible warning."


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