Fighting Natural Cover Fires
A review of the techniques and factors to be considered when combating grass, brush and forest fires
—Photo by John Titchen
NATURAL COVER fire fighting, the extinguishment of grass, brush, weeds, lots, forest, trash and dump fires, represents about 25 per cent of the alarms and 50 per cent of the fire fighting duties of many fire departments. Yet the budgeting of expenditures and the specific training in extinguishment techniques for this type of fire fighting are seldom given their proper places in a department’s planning.
Many fire chiefs also seem to forget that a large portion of the assessment rolls upon which their financing is based is composed of land values. I have heard a chief, over a fire radio, refuse to respond to a brush fire “because it was woods burning; call the state conservation department.” The chairman of the board of fire commissioners echoed this view. It was necessary to obtain a copy of the assessment roll in question to prove to these officers that it was just as much their duty to extinguish outdoor fires as those in structures.
Outdoor, non-structural fire fighting is composed of two types: Fires which involve autos, trucks, trains, air and water craft; and those which involve natural cover.
There are two principal methods of extinguishing natural cover fires, both evolving from the familiar fire triangle, but from different sides. The wet, or conventional water method, used by most fire departments extinguishes the fire by cooling. The dry, or “waterless” method, used by most conservation agencies extinguishes the fire by removing the fuel. The command decision of which to employ must be made early in the size-up by the officer in charge.
Factors affecting the decision are those of fire size, available help, type and distance of exposures, rate of spread, estimated time of control, weather, fuel, slope and terrain.
The governing factors for wet fire fighting are: The length of hose lines to be used as compared to the distance and time required to reach the most remote part of the fire; the amount of water available; and the possibility of resupply of water via tank trucks, hydrants or natural sources in the fire area. The use of brushbreaker type forestry trucks should be considered as a special-hazard type of protection, being designed for particular soil and fuel types.
The knapsack tank is a useful item of equipment in wet fire fighting. It is most valuable where fire intensity is low, water resupply is near and plentiful (such as a mountain stream), and the fire fighters have been trained in the proper use of the pump and tank. The tanks are particularly useful in mop-up and patrol phases when used with a wetting agent additive.
When water is not available in sufficient quantity to effect complete extinguishment, either beyond reach of hose lines, or beyond the capacity of municipal water supply, tanker relays, or natural sources, the dry line method will be quicker.
Dry-line extinguishment is more efficient when fires occur in rough terrain, soft ground, and far from roads, where the brush is light and may easily be removed. The leaves of hardwood trees may be cited as an example of this type of brush.
Size-up determines use
The first phase of waterless fire fighting is, as in all fires, the size-up. The first arriving officer must decide whether or not to use it. Once the decision is made, the job of controlling and extinguishing the fire may commence.
The first factor of consideration is economic: That of extinguishing the maximum amount of fire with the minimum amount of effort. The United States Forest Service has reduced this to a dollarand-cents ratio of fire losses to fire suppression costs through loss statistics on natural cover fires. A decision to hold a fire along a natural barrier, while permitting a larger area to burn, may result in a more rapid job of fire extinguishment and a resulting lower cost.
Fundamentally, the waterless method of natural cover fire fighting is an adaptation of the “one lick” forest fire line construction which is used by agencies controlling major fires in heavy timber. Manpower is organized into crews who proceed to surround the fire with an incombustible barrier (the line, or fire line).
— Waterous Company photo
There are two ways to do this: The patrol method, where each man has his assigned section, and the “one lick” or continuous production method, where each man performs a simple task rapidly while in motion along the perimeter of the fire. A number of men performing the same task is called a “group.” Several groups performing different tasks are called a “crew.” The entire organization moves somewhat like a centipede around the fire.
A fire company (five men and an officer) can be organized as follows:
The Officer — Determines location and route of fire line; removes fallen branches
Clearing Group—Consists of an axe man who chops dead falls clear to width of line, and a rake man who rakes litter and brash clear of line
Digging Group—Consists of a hoe man who chops duff away to mineral soil, and a shovel man to clean out line
Patrolman—Works to rear along line to be sure that fire does not bum across; backfires if necessary
This organization, working initially about 30 to 50 feet aw’ay from the edge of the fire, can control about 25 feet of fire line a minute. By expanding the size of the crew with manpower from mutual aid response it is possible to reach rates as high as one mile per hour in suitable terrain and fuels.
A dry-line fire fighting team is organized as a crew of men, divided and equipped to perform particular tasks by groups while in forward motion around the perimeter of the fire. The jobs of the task groups are:
- To locate the line to take maximum advantage of terrain, together with sufficient distance from the fire to permit the full line to be built in a relatively cool smoke-free area
- Clearing low brush and fallen timber from the line and adjacent areas
- Digging out roots and duff to mineral soil
- Improving line to form incombustible barrier by covering duff with mineral soil on both sides of the excavated line
- Burning out, from the dry line towards the fire, the small remaining strip of unburned fuel
- Patrolling to the rear to be sure that the line will contain the fire, including mop-up of remaining hot spots and snags.
Equipment used for dry-line fire fighting is not unusual or expensive. The exact tool load of each group and crew should remain flexible, as different areas of the same fire may require slightly different action. The important factor in dry-line work is to keep the tasks evenly distributed so that the entire crew can move forward at a steady rate.
Common tools and their uses include:
Machete—Mark line; clear light (up to 2-inch diameter) brush
Single and double-bit axe—Clear brush; cut downed timber; cut burning snags and stumps
Brush hook—Clear brush
Pulaski Tool—As axe, clear brush; as hoe, grub out ground; cut roots, cut burning area out of stumps and snags
Council Rake (also has other names)— Mows light brush; used as grub hoe
Fan Rake — Removes hardwood leaves and light duff
Broom — Removes leaves, pine needles and dry grass
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NATURAL COVER FIRES
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Pitchfork—Removes heavy broken brush
Pike Pole—Pulls snags clear of line; pushes standing snags clear of line when falling
Hoe—Digs to mineral soil
Pick Mattock—Digs and removes rocks
Pick—Loosens dirt and removes rocks
Shovels—Clean out trench; cover stumps and snags with dirt
Matches, Oil Torches, Fusee Flares, LPG Torches—To start backfire
Asphalt Rake—Control and spreading of backfire
Back-Pack Pump—Control of backfire; patrol
Power tools may also be used, but some heavy equipment requires skilled operators and may be expensive to obtain and maintain. Power saws and bulldozers are very useful in mop-up.
The size of the dry-line crew may be from five to several hundred, and is determined by the number of men available. Crews may be increased or decreased as the fire situation changes, with manpower being added or removed while in operation. Large crews become unwieldy and hard to manage but sometimes are helpful when building a wide line, such as a jeep trail across “new” country, or when a large number of untrained men are to be indoctrinated rapidly in dry-line techniques.
The important factor to remember in outdoor fire fighting is time. When the perimeter of the fire is doubled, the area burned (and therefore both the cost of extinguishment and the fire loss) increases four times. It is important at night to route crews so that extinguishment will be complete along a road. Sometimes two crews are sent through the burned area to the head of the fire, working back along a line to the road.
When detected early, many of the natural cover fires can be handled by a single pumping unit with a booster stream. Late detection, rapid fire travel,
or the necessity of calling a mutual aid pumper to respond to the initial call,
often carry the fires beyond the reach of booster streams (usually 300 feet from the paved highway) before the attack phase can be completed. Many woods and forest fires originate in remote areas as far as one mile from suitable roads. The use of waterless fire fighting has permitted better utilization of manpower at small fires and more rapid control of remote and large fires.