"What we prefer to do is construct direct fire line along the fire's edge…you can directly observe what the fire is doing, and you can move back to the area that you have just worked as your anchor point."
That's one of the first things you learn about in firefighting and firefighter safety, is how to construct an effective fire line at an anchor point. Usually it's at the base of the fire. It's at a point where, let's say, the ignition source was at. So it's already burned there, and it's moving out away from you. Oftentimes it's in a "V" shape. But you want to be anchored at a base so that when you start building your fire line you can move back to that location as a safety zone, if nothing else. So you're flanking the fire by building a line along the fire's edge, or you're making an indirect line of fire line construction, and you're burning the fuel as you're completing the fire line. The fire line construction can take on the form of chain saws used to cut brush, large trees or small trees. We'll remove the vegetation in front of the firefighters that are carrying axes, what we call pulaskis, as well as other modified tools, shovel-like tools as well as rakes. The fire line is scratched down to mineral soil, or cleared of any vegetation down to mineral soil. The width of the fire line is dependent on the type of fuels that are in the area. If you're in an area of real heavy fuels, you want to make a wider fire line—five, seven, [feet]—in some cases, a dozer width wide, maybe ten feet wide. But we can usually get by on a three- to five-foot fire line in most fuel types. Where you have to make them wider is when you're cutting along some real dense brush, like chaparral in Southern California. Your fire lines there effectively have to be one or two dozer blades wide to prevent the fire from spotting over your line. Oftentimes, if the winds are strong enough, that's not even going to stop it.
So again, you have your fire line being constructed along the flanks of the fire, and you're working your way around towards the head of the fire, but you're doing this gradually along the safe edges of the fire so that you're not out in front, again, of the fire, without an anchor on either side. That way, if you do get in that situation, and the fire burns around your line, then you just have to start over again. This way, you have a good solid base to work from, and encircle the fire.
A fire line can also be assisted or constructed, if you will, by using air tankers. The retardant tankers can build fire line for you by boxing-in a fire. You'll have the first drop in a strategic location, and then continue your drops, attaching to the previous one, which is why you have the color in the retardant, so that the pilots can see where the last drop was at, and they'll connect right to that, work their way around the fire. Once they have it encircled, it's not going to stop the fire totally, but it will slow it down or retard it. What you need to have are firefighters on the ground to get into the area that is now slowed down by the use of the retardant, and build the fire line in conjunction with the retardant. You can effectively use retardant in the construction of fire lines to encircle the fire and stop it from moving.
Kern: So while you're on either side of the fire, flanking it, it's actually burning next to you.
Sheppard: It can be. That's where you have direct fire line construction right next to the fire's edge; or you can move away from it, whether it be fifty feet, a hundred yards, or even a mile. And there you have indirect fire line construction. What we prefer to do is construct direct fire line along the fire's edge. It seems like that wouldn't be the safest thing to do, but in actuality, in most cases it HAS been the safest thing to do. Because there you can directly observe what the fire is doing, and you can move back to the area that you have just worked as your anchor point. Your escape route leads right back to there. You're carrying fire with you, and so you're blackening along the fire's edge. Once it's burned, you can move into that area safely. You're working directly along the flanks of the fire, and as you move along to the head of the fire, that's where it might get a little more difficult if it's moving so rapidly you can't get around to the head of the fire safely. You may need to back off a little ways, and go indirect. Build your fire line out away from the fire and set your backing fires or burnouts to remove the vegetation, again, that I talked about before, in advance of the main fire moving against your fire line.