Clearing of vegetation is usually necessary and almost always desirable as a preliminary to moving or shaping ground. Any growth makes dirt or rock difficult to handle, and its decay will cause settlement of fills. To satisfy environmental concerns during construction, a building site must be surrounded by silting fencing. This is plastic sheeting several feet high to prevent silt material from being carried off the site by rain or wind onto neighboring property.
Some clearing of growth heavier than grass or weeds is done almost as an end in itself, for agricultural purposes. It makes possible replacing woods and brushlands with pasture, crops, or tree farms.
Clearing is preferably a machine job. It may be done by a wide variety of standard excavators, particularly by bulldozers, front loaders, and backhoes. But if the job is large and/or difficult, it will probably pay to buy or rent one or more of the specialized clearing machines or attachments discussed in Chapter 21.
Loose materials break into dust by impact, crushing, and grinding. The dust is released during loading, transporting, and dumping and may be blown by wind. When airborne, it can reduce visibility, causing accidents, damage to equipment, and serious health problems. Fugitive dust of only 2.5-micron size is respirable and easily inhaled into the lungs. It may include nitrogen oxides, sulfur dioxide, and volatile organic compounds. That small dust can cause more harm to human health than larger 10-micron dust that causes the visibility problem. The larger dust may be controlled by spreading chloride salt, mainly calcium chloride or magnesium chloride, on the material prone to produce dust.
In the United States the Environmental Protection Agency (EPA) cites storm water runoff as the most common cause of polluting surface waters and storm water runoff from construction sites has a significant impact on the water quality of streams and rivers. Consequently, the federal government passed regulations called the National Pollutant Discharge Elimination System (NPDES) intended to protect the nation’s water supply.
When there is construction activity disturbing the soil on a site, such as excavation or grading during site preparation, there is the potential for runoff that will cause contamination of the nearby waterways. Phase II of the NPDES regulations applies to any site of one acre or larger. Construction projects on sites of this size need an erosion and sediment control plan to apply for a state NPDES permit and also a local permit, if the community has a population of 10,000 or more. Unfortunately, the regulations vary from state to state and also may be different from city to city in the same state. To determine the requirements for a specific project it is advisable to check with the appropriate agency for the project location.
Many municipalities are now mandating the use of readily available erosion control techniques, such as exposing the smallest area of land possible for the shortest period of time or building a retention pond to detain runoff water long enough to allow settling out of suspended sediment.
The erosion and sediment control plan will certainly include silting fencing, mentioned in the first paragraph of this chapter. It may include roughening the soil surface or the use of turf reinforcement mats and straw bales or other forms of check dams to control erosion and hold back runoff flow in ditches. The plan should be prepared by or in the name of the owner- operator of the site. It is generally prepared by the project’s consulting engineering or architectural firm. It is not unusual for the contractors, who do earth moving on the site, to be co-permitees and their personnel required to receive instruction about the NPDES regulations before they can do any work on an NPDES-permitted site.
Cut or uprooted vegetation must be processed or removed as part of most clearing jobs. Possible ways include burial, allowing time to decay; burning, shredding, or chipping; removal from the area; and various combinations of these methods.
Disposal methods will be discussed below and throughout the chapter. They are considered first because of the extent to which they affect techniques of clearing.
Nitrogen. Disposal of vegetation by any method other than by burning is likely to be complicated by absorption of nitrogen by decay processes. This element is essential for life of every kind. Although abundant as a free gas in the air, its quantity in fixed or usable form in the soil is limited.
The problem of nitrogen deficiency is usually not a strong objection to disposal of vegetation by any reasonable method such as surface decay, or mixing into soil or plowing it under. Nor does it prohibit the use of wood chips for soil cover. But nitrogen deficiency must be considered in assessing both the immediate and possible long-term effects of the work.
The deficiency can be largely corrected by addition of suitable amounts of nitrogen-rich fertilizer throughout the period of decay or by planting legumes that can obtain nitrogen from the air. The end result is usually substantial enrichment of the soil, as the presence of abundant nitrogen aids the conversion of vegetation to soil humus.
Surface Decay. Cut or uprooted vegetation is sometimes left on the ground to rot. Soft material such as grass and nonwoody plants may disappear in a few weeks, but trees will make the area unusable for years. Prevention of regrowth is made difficult.
Disadvantages of disposal by surface decay are reduced, and may even be eliminated, if woody material is reduced to small pieces as part of the clearing operation. This may be done by using a shredder or a heavy rotary mower for clearing, or a chipper to grind up pieces after cutting.
This method is suitable for construction only if clearing is done long in advance of removal of topsoil.
Burial. In agricultural work, burial is often the preferred means of disposal if equipment of the proper type is available, and is big enough to handle the growth density and trunk sizes involved, and if the soil is soft enough to permit it.
Grass, weeds, brush, and sometimes saplings may be buried intact by a brush-breaker plow, or slashed, chopped, and partially or wholly buried by a heavy disk harrow. Rolling choppers can disintegrate and partially bury medium-size trees, including trunks.
Burial of this type is used in agricultural rather than construction clearing, and only when the ground can be left undisturbed (except for planting of a cover crop) until a large part of the material has de -cayed. This process may take weeks or years, depending on vegetation type and maturity, and weather.
In construction, about the only permissible burial is undisturbed, low-cut stumps under deep fills. When allowed, this exposes the fill and its supported structures (usually road pavement) to eventual settlement as the wood decays. This danger is often outweighed by advantages in prevention of sliding of fill down a slope, and in economy.
Loose stumps are often buried, but the operation is likely to be expensive and unsatisfactory. Attached roots make them enormously bulky; cutting roots back to the buttresses is likely to ruin saw chains by contact with clinging dirt. They are still awkward after cutting back.
Fill including stumps will almost always settle badly. Spaces left in and under irregularities will gradually fill with soil, allowing the surface to sink. Rotting of the wood will cause slow, long-term settlement. Both effects are at a minimum if burial is in permanently wet mud that will flow around them immediately and preserve them against decay.
In any soil, one stump can be packed in more solidly than a number of them. A common practice, when there are just a few big stumps, is to dig out each one with a backhoe, dig the hole deeper, put the stump back in it, and backfill. This shortcut is often not on the plans, and may cause surprise and dismay later, when the surface settles or a small machine tries to dig a trench through the area.
Burning. Where burial is not practical, burning is usually the most efficient method of disposal and does the least long-range damage to the environment. Most of the discussions in this chapter are based on the presumption that fire will be used.
However, since open burning is prohibited or severely restricted in an increasing number of states and localities, it is worthwhile to examine the relative advantages and disadvantages of fire compared with other methods of disposal.
It will be assumed that burning is handled by reasonably experienced crews, with proper regard for safety and confinement of the fire to the vegetation being cleared.
Piles of brush or trees usually contain one-fifth to one-tenth solid matter, the rest being air space. These solids average at least half water, and most of their dry weight is cellulose, lignin, and other burnables. The ash that is left after efficient burning is only a few percent of the dry matter (exact figures are difficult to obtain). A good fire will therefore reduce the vegetation to a small fraction of a percent of the original bulk.
The ash residue is too fine to be good fill material, but its quantity is so insignificant that it can usually be incorporated in other soils, or pushed aside, without difficulty.
It may be reasonably held that efficient burning results in the total removal of cut and uprooted vegetation.
Soil under a hot fire is rendered unfit for supporting growth for 1 to 3 years, but can be restored by plowing or ripping, and fertilizing.
A fire in dry material, with plenty of air, will burn mostly with hot clean flames, which produce carbon dioxide and water vapor, with few pollutants. Green wood and leaves, wet or dirty piles, and most weakly burning fires will give off large amounts of smoke, containing variable quantities of methanol, methane, acetic acid, tars and oils, and carbon monoxide.
Such fires, if upwind from inhabited areas, may create an extreme local nuisance, but its duration is very short. It is doubtful if the pollutants they put into the atmosphere equal those that would have been discharged during the natural lifetime of the plants themselves if they had not been destroyed. The burning concentrates them into a few hours or days.
The pollution problem that faces the world does not arise from country areas or from any activities (including open fires) normally conducted in them. It is a problem of cities, factories, and internal combustion engines.
It is therefore quite unreasonable that burning should come under total or almost total bans, while the real offenders are usually let off with moderate percentage reductions of their offensiveness.
Regulations against burning are costly. Substitute means of disposal, which are discussed in following sections, are more expensive under most circumstances, require vastly increased consumption of fuel, and may create environmental problems of long duration. The extra cost in highway construction alone is probably already in the tens of millions of dollars a year.
Clearing by hand in cold weather may be practical only in the presence of hot fires, for both their emotional uplift and their actual prevention of acute discomfort, including frostbite. Even without need for heat, there is little satisfaction in clearing brushy land if the debris must be left to litter the ground, making it dangerous for people and animals; or heaped into unsightly piles that take years to rot. And loss of unfarmed and unmowed fields to brush is a serious and increasing ecological problem.
The cost of buying or renting shredding equipment, noise, fueling problem, and danger to inexperienced operators put these machines out of reach of most people who wish to do their own clearing.
Chipping. Brush, saplings, and even big trees may be fed into machines that reduce them to chips of small and fairly regular size, by action of a rotating toothed drum (see Fig. 1.1). These chips may be scattered or piled in the work area, or fed through a chute into dump trucks.
A small machine can be towed behind a pickup truck, and often maneuvered on the job by hand. It is hand-fed with bundles of brush, and with saplings up to 3 or 4 inches (7.6 or 10.2 cm) diameter.
At the opposite end of the scale are monsters which can gulp down entire trees, with trunks up to 20 inches (50 cm) in diameter, without need to even trim the branches.
The chips that are produced may be a definite asset, may be a problem, or may have no importance.
A few modern paper mills are able to digest wood chips that include bark and twigs, and will pay good prices for them. If such a mill is within economical hauling range of a clearing job, chipping pays off both in money and in utilization of the wood. In other areas, chips might be sold for processing into pressed wood, or charcoal and distillation products.
There is also a possibility that chips can be used on the job, either because they are really useful or because it is the best way to get rid of them. They can hold soil on slopes while vegetation becomes established and can add organic material to poor soils. Some applications are discussed in Chapter 7, together with possible problems.
Chips from light to medium thickness of vegetation may be left scattered on the ground, to be incorporated with the topsoil when it is pushed off or cultivated. If the growth is heavy, the chips are likely to make the soil critically short of nitrogen, and difficult to work, and to accumulate in spots as pockets of almost undiluted wood.
Chipping is usually not practical for uprooted stumps, unless they are very small in proportion to machine capacity. Their bulk and shape make it difficult or impossible for the guards to pass them or the drums to grip them, and the dirt and rocks stuck to them damage cutters and make the chips unsalable.
Chips made from stumps in the ground are always contaminated with dirt.
Piling chips, either by keeping a discharge chute in one direction or by dumping them from trucks off the work area, should be permitted only when they are to be reclaimed later. Such piles are likely to remain for many years before decaying enough to permit growth of vegetation.
Chipping machines are expensive, consume large amounts of fuel, are extremely noisy, and may be dangerous to personnel. Their use in mass clearing is justified when there is good use for the chips, in areas of high fire danger, or where smoke cannot be tolerated.
In addition, chippers are valuable in low-volume or selective clearing and trimming, where the cutting would otherwise have to be hauled away.
Removal from Area. Removal of cleared vegetation from the work area may be anything from a sound and profitable operation to a financial and ecological disaster.
Where lumber or paper mills are within economical hauling distance, it may be possible to sell cut trees profitably. In some cases, the user of the wood may be glad to cut and remove the usable part of the vegetation and pay for the privilege.
The usability and value of trees vary greatly, in both quality to be found on the job and the processing equipment that will handle them. Some users are very narrowly restricted as to species, size, straightness, and soundness. Others will take (usually at a lower price) almost anything that is recognizable as wood. In any big job, it may be worthwhile to invest considerable time in investigating possible outlets.
Firewood is another possibility. Very high prices are often paid for wood cut in 2-foot (61-cm) lengths and split to cross sections averaging 30 square inches (190 sq cm) or less. Lower but still interesting prices may be paid by cordwood dealers for cut (and perhaps trimmed) trees which they process themselves. But this market is largely limited to the vicinity of cities.
If the vegetation must be removed and nobody wants it, the cheapest disposal is to just push it off the right of way, or out of the construction area, and hope to forget it. Fortunately this practice is usually not allowed. Even if it is, it may have disastrous effects on high-priced sur -veyors’ reference points.
If the contract requirement is off-site disposal at a distance, there may be several possibilities. Both bulk and problems can be greatly reduced, although possibly at considerable cost, by chipping the vegetation and hauling out the chips. Otherwise, trees should be trimmed into lengths suitable for dump trucks or trailers, or flatbeds of either type, with all angles in trunks or branches cut to make them lie flat. Nondumpers require a log-handling crane at the disposal site. Brush may be chipped and loaded, or loaded whole.
Except with medium to large tree trunks, or chips, these loads are likely to be mostly air. Haul cost per pound will be proportionately high.
Unchipped vegetation that is hauled off the job, and is not to be burned, may be dumped in piles over a wide area or stacked in high piles with a log grapple or clamshell. See Fig. 1.2.
The result is almost always an environmental nightmare. Bulk is enormous in relation to the amount of clearing done, appearance is generally a first-class eyesore, and the dumps may be dangerous or impossible to cross for many animals and for people. They may serve as inaccessible infection points for plant insects and diseases.
FIGURE 1.2 Clearing with a rake blade.
Depending on the size and variety of vegetation involved, and climatic conditions, these unfavorable conditions may persist for 5 to 20 or more years.
Legal Basics. The discovery of contaminated ground is an environmental hazard. Excavating contractors or site developers, who normally move “clean dirt,” must be wary about protecting the business from the legalities of environmental hazards. They must do everything feasible to protect themselves from environmental entanglements. An environmental due-diligence survey should be done. It involves three stages: (1) initial assessment (any history or current evidence of contamination), then (2) investigation, and finally (3) remediation.
For instance, assume a basement is being dug in a development and an old, unknown underground storage tank is broken and leaks heating oil into the ground. Who is to be blamed? As the contractor, you may be in trouble if your only insurance is a standard, comprehensive, general liability policy. To cover this special liability, it is necessary to have an “environmental rider” on the basic liability policy.
In addition to adequate insurance coverage, contractors should protect themselves by asking for phase 1 and phase 2 reports at prebid meetings. The phase 1 report involves a thorough investigation of the site’s past uses as well as uses of surrounding properties. Phase 2 details the results of soil and water sampling at the site.
Even if the reports indicate the site has a clean bill of health, the construction contract should have a stop-work clause—especially if excavation is involved. This allows the contractor to stop work without penalty if potential environmental hazards are found. The contractor should then contact the project owner, or her or his agent, and report the finding. If the owner refuses to report a situation that poses an immediate hazard to human health or the environment, the contractor may be bound to report the situation to the proper authorities.
Reporting environmental problems can be complicated simply because of the numerous agencies that require notification. If a required one is missed, the fine can reach $25,000. To avoid any oversight, report to all possible agencies—the Environmental Protection Agency (EPA), state agencies, fire departments, local planning commissions, the National Response Commission, and the like.
If a regulatory agency determines that the property’s contaminated soil must be cleaned, the owner must carefully select an experienced soil remediation contractor. This is important because the property owner is fully liable for the contractor’s actions—and penalties for bad actions start at $10,000 per day.
Treatments. In the early days, most contaminated soil was simply dug up and hauled to a landfill. However, now in the United States the Environment Protection Agency (EPA) encourages alternative treatment methods to actually clean the soil or make its contaminates less harmful. These methods are known as soil remediation techniques. They can be classified into five general categories: biological, physical, immobilization, chemical, and thermal.
A 1993 EPA report “Cleaning Up the Nation’s Waste Sites: Markets and Technology Trends” gives insight into the uses of the various technologies. The technique chosen for a given site depends on the contaminants and the site’s geology. For example, cleaning up an old gas station may be handled best with vapor extraction if the contamination is mostly gasoline and if the soil is not too dense. In dense soils, biomediation could be a better choice. But if heavier oils are present, thermal desorption may be most effective.
Biological remediation (bioremediation) uses microorganisms, such as bacteria, that eat soil contaminants and turn them to harmless—or at least less toxic—compounds. This method is preferred because it works in situ, i.e., is done in place. Nutrients and oxidizers are added to the soil to stimulate the growth of hydrocarbon-eating bacteria. A specialized equipment system, called MecTool, is used for in situ soil remediation and can inject microbial nutrients to depths of 100 feet (30 m).
Physical methods for remediation include such processes as drawing a vacuum through wells drilled in the soil to pull out volatiles, or pressurizing the wells with heated air, or in situ steam stripping, a vacuum extraction process with steam injection wells. The vapors captured in all three processes are then treated to remove the contaminants. Another physical technique uses a water-and-detergent solution to wash the contaminants from the soil.
Detection. The use of trenchless technology can be helpful in locating the extent of contamination. Compact directional drilling equipment is used to reach areas of the underground that are inaccessible under a building or other obstruction. Refer to Fig. 20.51.
As stated for the National Ground Water Association in the United States, “horizontally” drilled wells have been installed to perform remediation of subsurface groundwater and soils with pump and treat systems, such as by air spraying, soil vapor extraction, and bioremediation. Horizontal wells also are used to prevent contaminant migration and for characterization, i.e., taking samples for evaluation, under buildings and other areas where surface conditions prevent drilling of vertical wells. Because underground plumes often spread horizontally, fewer horizontal wells are required to treat a site than the numbers of vertical wells that would be needed. The EPA believes horizontal well technology has the potential for significant cost saving on site remediation projects.
The success of horizontal directional drilling (HDD) depends on the drilling machine’s electronic guidance system and its correct use. Currently there are two types of systems: (1) the walk-over system and (2) the wireless system. The wireless guidance system uses computers to calculate information necessary to steer the directional bore. This system is generally used for long, deep installations.
The majority of horizontal directional installations use the less expensive walk-over electronics system. There are two basic components: (1) a radio transmitter mounted in the drill head and (2) a handheld receiver operated by a crew member, who walks on the ground surface directly above the drill head as the pilot hole progresses. The transmitter sends signals to the receiver which processes the information and displays it on the receiver. This tells the drill head location and depth, roll angle of the drill head slanted face, and the pitch or horizontal inclination of the drill head. This information is transmitted to the drill machine operator by two-way radio so that he or she can make adjustments in the drilling process.
The use of vacuum excavation or potholing has been useful in locating underground pipelines that could be damaged by HDD running into them. Vacuum excavation, described in Chapter 5, is used to protect against damage to underground utilities when excavating.
Immobilization is a process in which a binding agent, such as cement, fly ash, kiln dust, or asphalt, is mixed with the soil to physically or chemically immobilize contaminants. This method could be called solidification, while chemical treatment is more stabilization. Dechlorination is a chemical remediation technique used with soils to react with chlorine in such compounds as polychlorinated biphenyls (PCBs), creating by-products that are less toxic than the original contaminants.
Among remediation methods that rely on heat are the in situ vitrification, incineration, and thermal desorption. Incineration is the most frequently used of any soil treatment method at federal cleanup sites, according to the EPA. A thermal desorption system puts the contaminated soil through a heated, rotating drum as in an asphalt plant. The temperatures in the drum are sufficient to vaporize the contaminants for collection and treatment.
Dozer. Dozers and loaders are basic machines for clearing, both with regular blades or buckets and with special attachments. They work best when the ground is firm enough for support, and where they are not hampered by holes, gulleys, sharp ridges, and rock. These forms of equipment are described in Chapters. 15 and 16.
Uneven surfaces make it hard to keep the blade in contact with the ground, and lead to burial rather than removal of vegetation in hollows. However, there are few places where a dozer cannot aid hand-clearing crews, by clearing areas where it can work, moving logs and cut brush, cutting roads for supply trucks, or firebreaks.
Dozers have a particular advantage over hand crews where briars and vines are abundant, as these are very tedious to cut but can be readily stripped off by the blade, provided the operator does not take too long a pass and get caught in the tangle.
Unless he or she is completely protected by a cab with windows, an operator should have hand clippers to cut a path out if necessary.
Brush and small trees may be removed by a bulldozer moving with its blade in light contact with the ground. It will uproot or break off a number of the stems and will bend the rest over so that by a return trip in the opposite direction, it can take out more. If the distance is short, it is best to doze the whole patch in one direction, then across or backward.
Individual small trees are first knocked over, then pushed out with another pass in the same direction.
Results will vary with the type of vegetation and the condition of the soil. Hard-baked soils will cause a high percentage of broken stems, while wet or sandy conditions favor uprooting, which is more satisfactory for most purposes. The work can be speeded up by having a laborer cut out or pick up individual bushes that would otherwise require another pass by the dozer.
If the job requires removal of light stumps and roots, they may be overturned in one pass and pushed out in the next. It may be necessary to dig several inches into the soil to get a grip on them, then backblade the soil into the holes.
Brush heaps may be largely freed of dry, loose dirt by rolling them over with the blade and shaking the blade up and down. If this is ineffective, rolling them over backward or pushing them from the side may be tried. A dozer with a blade which can be easily tilted down on either end is very good at this work, as one corner can be used for taking out roots and pushing piles without taking a bladeful of dirt along with it, and the blade can be returned to flat position to skim off surface brush.
Rake Blade. Rake blades, which are made for the larger bulldozers and loaders, add to clearing efficiency under most conditions. See Fig. 1.2. They allow working below ground level, to take out roots as well as surface material, usually without bringing the soil along with them, if it is dry or sandy.
However, they may be somewhat specialized. A blade with teeth close-set enough to handle brush may bend a tine if it collides with something solid, while one strong enough for impact is apt to have too wide spacing for brush. This type of equipment is described in Chapter 21.
With or without rakes, any mechanical loosening and removal of brush that is to be burned should be done when the soil is dry for best results. If it is wet, it lumps and sticks.
If the loosened material is allowed to dry, much of the dirt can be shaken out while piling, by rolling and shaking.
Burning. Generally in the United States it is necessary to get a permit from the local authorities to burn for clearing. In general, it is best to burn machine-cleared vegetation at the same time that it is piled. A hot fire, including heavy wood, is prepared, and brush piles are pushed up on it. A new fire is made when the push gets too long.
Best results are obtained if the vegetation is uprooted and allowed to dry at least a few days before burning. This may be done by backing the dozer into the woods from the cleared edge, and uprooting small patches, or individual trees, pushing them clear of the ground, and then leaving them.
The trash dries more rapidly scattered on the ground than in piles. Dirt will tend to dry and break away from stumps, and to sift out of roots and stems. When burning, the brush nearest the fire is put on it first.
Fires fed by a dozer tend to get choked up with dirt. In general, matted light brush is more difficult to clear and to burn than heavy brush or small trees, as it tends to slip under the blade or to bring too much dirt with it.
Fire Box or Trench. The local authority which issues a permit probably would be more inclined to do so if the burning was to be done in a fire or burner box or trench prepared for the burning. The system for doing this controlled burning is described and illustrated later in this chapter.
Dozer Protection. When a dozer is clearing dense undergrowth, there is the danger that it will fall into some hole, natural or artificial, whose presence is concealed by the brush. This may be guarded against by scouting the area on foot, and by moving forward in a succession of short pushes overlapping each other on the side. This enables the operator to watch from one side, without getting branches in her or his face, and to observe the nature of the ground. In addition, it avoids tangling the dozer in branches and vines.
Any dozer used for clearing work should be thoroughly protected with crankcase and radiator guards; the latter include screen with holes not over ¼ inch (6.4 mm), and accessible for removal of leaves and trash. The engine needs side guards. The operator should carry hand tools to cut herself or himself out of tangles.
Minimum operator protection is a strong overhead structure. See Fig. 1.2. Most new clearing units have complete, extra-strong cabs, often heated and air conditioned.
Accidents have been caused by branches moving throttle and clutch controls.
Other Machines. There are a number of types of equipment that are used for chopping or shredding brush, which may bury it or leave it on the surface to rot or to be removed by other equipment or laborers. Refer to Chapter 21 for the special equipment.
A big rotary mower mounted on the rear of a wheel tractor is highly effective up to its thickness-of-stem limit, which may be 1½ to 3 inches (38 to 76 mm). Vertical rotary shredders may handle double that size. Brush is mostly chopped or shattered into small pieces, but root systems are seldom disturbed. There is no suppression of regrowth.
The sickle bar or hay cutter, in heavy-duty models, will cut brush up to ¾-inch (19 mm), but with considerable wear and breakage. It does not chop the stems and is little used in clearing.
Either a rotary or a sickle bar can be used to suppress regrowth by repeated mowings.
A big moldboard plow, preferably a brush-breaker model, can put brush and saplings underground, cover them neatly with dirt, and leave them to rot. The area is usually harrowed lightly and planted to grass or a cover crop immediately.
A big heavy disc harrow, with discs 24 inches (0.61 m) in diameter or larger, chops brush and buries a large part of it. See Fig. 1.3. Big pieces may be loosened, chewed, and pushed around without burying.
FIGURE 1.3 Clearing with a disc harrow. (Courtesy of Rome Plow Co.)
Both the plow and the harrow tend to create ridges and troughs in the ground surface, because they move loosened dirt to the side.
A rolling chopper knocks down, tears, and mashes both brush and trees, and cuts near-the-surface roots. A small portion of its cutting is buried.
Mechanized Logging. In some large-scale operations, logging may be almost completely mechanized, with felling, trimming, bucking, and transport (or piling and burning) done by highly specialized machines, some of which are described briefly in Chapter 21.
However, most clearing-for-excavation projects must rely on more standard machines and/or hand labor.
Cutting or Uprooting. Big equipment can handle small trees in the same manner as brush. But big trees, or any trees too large to be walked down by the equipment on the job, may require special kinds of work.
Pushing a tree over with a dozer or pulling it down with a cable follows the general methods described for stumps later in this chapter. However, a machine can generally uproot a much larger tree than a stump, because of greater leverage from a higher push or pull point and help from the weight of the tree, which tends to tear out its roots as it leans.
Handling Trunks. Tree trunks, even in sapling sizes, may be tricky and dangerous to push around. One may ride up over the top of even a big dozer blade during ordinary pushing. It may be put under tension by pushing while an end is blocked, which may result in its whipping with great force against the cab, or into other machines or workers in the area. An operator must be vigilant in avoiding such a situation.
When felled trees are pushed into heaps for burning, the piles contain so much air-space that they may be very fire-resistant. Heavy branches and crooked trunks increase this difficulty.
Branches may be cut off and trunks cut into pieces to make more compact piles. Or the pieces may be placed on an existing fire by a clamshell.
Subcontracts. If trees are to be removed which are of no value on the job, an attempt should be made to sell them. To contractors desiring to confine themselves to dirt work, the best arrangement is to get the customer, whether sawmill, firewood dealer, or whatever, to buy the trees on the stump and cut and remove them. A danger is that the logger may fail to do the work in the time specified, and so force contractors to do it themselves at the last moment. In making such an arrangement, the disposal of the scrap wood and brush and the height of the stumps should be specified.
A sawmill operator is interested only in large, sound trunks, whereas a pulp or firewood worker can use bulky branches also. The mill will ordinarily pay the best prices but do the least work toward cleanup of the tract, unless it has an arrangement with pulp or firewood users to take its tops and limbs.
No one wants the rotten trees, crooked branches, and brush, but the lumbermen may agree to burn them, if this is a part of local logging practice; or if the contractor accepts a complete cleanup job as partial or full payment for the wood.
Cooperative clearing arrangements may be made in which the logger is assisted by the contractor’s tractors or trucks.
Stump Height. Stump height may be determined by local law or lumbering custom. From a clearing standpoint, high stumps are more easily removed than low ones, and are especially desirable when the machinery is undersized for the job or depends primarily on winches. Low stumps are more difficult to cut, particularly where the trunk flares out widely at the bottom, but do not impede machines as much and can often be filled over and left.
Cutting. If the trees are valuable and lumbermen will not clear them out in time, the contractor may cut and stack them for future sale. This, as a logging proposition, is somewhat out of the field of this book and will be considered very briefly.
FIGURE 1.4 Felling a tree. (Courtesy of Homelite.)
Practically all wood cutting is now done with chain saws operated by one worker. Their construction and operation are described in Chapter 21.
There are a number of sizes and models. Thick logs require long blades and increased power. For any log thickness or blade length, increase in engine power means faster cutting, but also more weight to handle.
Most experts recommend use of a bar long enough to cut the average size tree on the job in one cut. Undergrowth should be roughly cleared around the tree before cutting it, to reduce danger to workers and tangles with fallen trees.
A tree should be notched by a V cut up to one-third of trunk thickness, on the side toward which it is expected to fall. The bottom cut of the notch should be made first and should be horizontal, the other sloped down to meet it. See Fig. 1.4.
The tree is then cut through from the other side with a level cut 2 inches (51 mm) or more above the floor of the notch.
If the saw bar is longer than the tree diameter, or a hand crosscut is used, the line of cut is parallel to the back of the notch.
The cut is theoretically finished when the strip of uncut wood (the hingewood) has been reduced to 
or 
of trunk diameter. The tree should now fall toward the notched side in a direction at right angles to the length of the hingewood, if its balance has been judged directly. If the hingewood tapers, direction will tend to shift toward the thicker side.
The hinge may be crushed as the tree starts to lean, and may narrow the edge of the cut, binding or even crushing the saw. It is necessary to be alert to pull the bar out quickly. It can be put back in if the fall does not occur.
Direction of Fall. Natural direction of fall of a tree is influenced by a number of factors. Location of its center of gravity, as affected by lean, twist, and limb location, is primary. Direction and velocity of wind may be important.
When practical, cutting should be done so as to take advantage of natural factors, to drop the tree in the direction that it tends to fall. This direction can be made positive, or altered moderately, by appropriate notching and cutting.
For greater changes in direction, including tipping the tree oppositely from its normal inclination, wedging or line pull is needed.
FIGURE 1.5 Use of saw and wedge.
Wedging. If there is the slightest question about the direction the tree will fall, a wedge of wood, plastic, or magnesium should be driven lightly into the back of the cut, to prevent wrong-way leaning. This protects the saw against binding, and may influence direction of fall. See Fig. 1.5.
A large tree that has a moderate tendency to fall in a wrong direction can be forced into the right one by wedging. The wedge or wedges may have to be iron or steel, as other materials may not withstand heavy driving. Saw manufacturers oppose any use of hard metal.
The moving saw chain must never touch a hard wedge, as it would suffer immediate and severe damage. The wedge therefore cannot be inserted until the cut is deep enough to provide ample working space for the saw, and the operator must exercise extreme care.
Wedging tends to overturn the tree to the side directly opposite. But the fall will be affected by other factors, such as unbalance to the side, taper in the hingewood, or wind pressure. These factors should be allowed for in placing the wedge.
Wedging may be started with a soft wedge, to keep the cut open until it is deep enough to use the hard one.
One wedge may not be sufficient to tilt the tree. A similar wedge may be driven just above it, Fig. 1.6A, or a thicker wedge driven beside it. Since a thin entering wedge is not needed now, a made-on-the-job wood wedge, Fig. 1.6B, may be used.
FIGURE 1.6B Making a wood wedge.
FIGURE 1.7A Pulling from the side.
The hingewood may be cut thinner to make wedging easier. But if this strip is made too thin or cut through, or if it is weak because the wood is brittle or decayed, a badly unbalanced tree may fall backward over the wedge.
If tree diameter is too small to safely accommodate a wedge and a chain saw, the chain may be replaced by a hand crosscut, if one is available. Or the tree may be pulled by a line fastened high up, or pushed by a pole or a loader.
Pull or Push. Direction of fall can usually be controlled by a rather light pull on a line fastened high up, the higher the lighter. The first problem is placing the line, which could require either a good climber or a tall ladder, and must be done before starting the cut.
The tree should not fall on the workers or machine doing the pulling. Heights of trees are difficult to estimate, so it is safer, and uses a shorter line, to use a pulley block or blocks and pull from the side. See Fig. 1.7A.
The best machine for pushing a tree is a backhoe. It has a high reach in proportion to machine size, and can stand back far enough not to interfere with the cutting.
Pull or push is usually light at first, and is increased as the cut deepens.
Tree cutting is dangerous work, because of the nature of the tools used and the sometimes unpredictable behavior of trees and their parts.
Direction. In spite of best judgment and efforts, a tree may fall in an unexpected direction, even backward across wedges. And a fall may occur much sooner than expected, because of concealed weakness in the base, or a puff of wind.
No one should be in a cutting area except the worker(s) at the foot of the tree. They must be alert to move quickly. The critical area should be clear of brush and litter, as tripping over it might have fatal consequences.
A chain saw that is not being used, or any other valuable equipment, should be placed behind a tree or other protection during tree felling.
Overhead Breaks. Some trees come apart while being cut (Fig. 1.7B). Blows of a hammer on a wedge, rouZgh contact of a pusher bucket, or even the vibration of a saw may loosen dead limbs so that they come crashing down around the base. If the trunk is decayed, it may break as it starts down, with the lower part leaning and falling conventionally, but leaving the upper parts in the air to come straight down.
This will not happen when a tree is live and healthy throughout, but dead branches and decay are not necessarily visible from the ground. It is more common in tall trees than in short ones, and the pieces fall harder.
Hard hats are not sufficient protection against the weight of pieces that might fall. The top must be watched closely during work, and workers must not be ashamed to run instantly if anything breaks loose. The danger area is usually small and close to the trunk, although this varies with limb spread. But, of course, do not take the direction the tree is expected to go.
FIGURE 1.7B Trees may come apart.
FIGURE 1.8 Moving hung-up tree with pole.
Leaners. A tree may be held from falling by other trees. This may be by comparatively light contact of branches while the cut tree is nearly vertical, or because of fall into a crotch or across heavy limbs.
Such a tree may be brought down by moving the lower end away from the direction of fall. A small or medium tree can be moved by prying the butt up with a pole and swinging the pole. This can be repeated as many times as necessary. See Fig. 1.8. Medium to large trees may be lifted or pulled by a machine, or pulled by a block and fall.
If the trunk cannot be moved, it must be cut in the air. Because of the strain of its position, only shallow cuts or notches can be made in the upper side, with the main cut from below. Pinching of the saw and erratic movements of the trunk can be expected and can be dangerous.
As each piece is cut and knocked or pried out of the bottom, the remainder should slide down to rest on the ground, usually at a steeper angle.
Cutting the supporting tree is too dangerous to be attempted. It is usually under great extra tension and is likely to snap and fall suddenly during work. The leaning tree would then be apt to drop on the workers doing the cutting. See Fig. 1.9.
Trimming. When the tree is down, the branches should be cut off nearly flush with the trunk, before any other trees are dropped across it to make a tangle. Light branches and any heavier wood which is to be wasted should be piled, burned, chopped up, or taken away by the methods described for brush.
Removal. The trunks may be dragged out of the woods by tractors or cut (bucked) into lengths where they fall. Saw logs for small mills may be from 8 to 16 feet (2.4 to 4.9 m) long, the size being largely determined by the use for the sawed wood, the capacity of the mill, and the trucks that carry the logs. Piling, which may often be made from thinner trunks than saw logs, is left full length. Cordwood is usually in 4-foot (1.2-m) sections, and split to a size that one person can handle. Pulpwood varies in length in different localities and is usually peeled but not split.
Dragging (Skidding). Crawler tractors are the standard equipment for dragging long logs, but with good ground conditions they may be replaced by rubber-tired machines with either four-wheel or two-wheel drive.
FIGURE 1.9 Never cut the support tree.
Crawlers and four-wheel drives usually carry loaders or dozers. Their efficiency may be increased by mounting winches, and by use of log carriers and various rigs too specialized for description here.
A log is usually pulled by means of a chain or cable fastened around its butt, choker-fashion, and attached to the tractor drawbar or winch. The most important consideration in arranging this is to get the butt off the ground, or riding on the ground very lightly, as digging in will take greatly increased power and will rip up the trail. A short line, particularly to the top of a winch, is helpful unless the log has a greater diameter than the height of the draw point.
The log may also be pulled onto a stoneboat, or other sled, and the line passed through the eye, or two lines used as in Fig. 1.10.
If the tractor is sufficiently powerful, several logs may be pulled at a time by attaching them individually to different lines. If only one line is available, they may be fastened with one choker, which should be fastened well back, as such piles often come apart while being towed.
Two-wheel-drive tractors can drag logs or bundles of logs on dry ground. Loads must be small, but they move briskly. If the tractor has a hydraulic lift drawbar which can be chained to the log to lift its butt off the ground, its efficiency is more than doubled, as the weight on the driving wheels is increased and friction is greatly reduced.
Moving Short Wood. When trucks can get in the woods, cordwood and pulpwood are usually cut to size and trucked out. As wood is much lighter than dirt, a dump truck can carry several times its body rating, if the pile stays on. Make an arrangement by placing planks, poles, or thin split logs vertically along the body sides to permit high piling. These are held in place by the piled logs. If the road is rough, it is wise to pass a chain from the body over each row of logs and to tighten it with a load binder.
If the wood is cut short, and rain or unforeseen mud conditions make trucking impractical, it may be dragged out by tractors. If a stoneboat is available, logs may be piled on it, and the tractor line threaded through the eyehole over the pile and anchored on the back. The eyehole should be beveled so that a chain or cable can slide freely through it, as the tractor pull will then hold the logs to the stoneboat. See Fig. 1.11. If no boat is available, the logs may be piled on the line, which is then looped around it as a choker. Parts of the piles may be chained by snaking the line under them, without repiling.
FIGURE 1.10 Skid-pan log hitches.
Storage. Wood should be stored outside of the work area where it will be accessible both during and after the digging. Poles and logs may be very useful in shoring up banks, making corduroy roads, getting machinery out of the mud, and other purposes. A buyer might be found for the wood at any time. Stored logs or cordwood should be stacked so as to be off the ground and well ventilated. This makes it easier to remove them later and delays damage from rot and borers. Cordwood is usually stacked in easily measured units.
Personnel. If possible, experienced loggers should be employed for lumbering. They will be able to do it much more efficiently than equally energetic and resourceful persons not used to the work. The difference may be as much as 10 to 1.
FIGURE 1.11 Cordwood on stoneboat.
A stump is the base of a tree trunk and its attached root system. The trunk part may be anywhere from a few inches (centimeters) to many feet (meters) in diameter. It usually flares out near ground level into root buttresses, which connect it to the major roots. Its top may be flush with the ground or several feet high.
Roots form a network near the ground surface. A few species of trees have a taproot, a strong root that extends more or less straight down from the center of the trunk. It makes stump removal much more difficult.
Stumps are a major problem in most clearing that involves trees. They can sometimes be cut low and left under deep fills, but usually must be removed.
Stumps may be broken out by uprooting the whole tree, then disposed of as part of the tree or separately. But it is more usual to cut and remove the tree and then take out the stump.
Stumps may be pushed out by powerful dozers; dug out by somewhat less powerful dozers, rippers, or hoes; pulled out with cables or chains; or blasted. Blasting may be combined with other methods. It is occasionally practical to burn stumps in the ground.
Once out of the ground, stumps present a problem of disposal. As massive pieces of green wood caked with dirt, they are difficult to burn. Nevertheless, this is usually the best way to get rid of them. They are so bulky and irregular in shape that they are hard to bury, and they are an eyesore in piles. Since they rot, they cannot be used in fills under structures.
Pushing. Crawler tractors, with dozer blade or loader bucket, or a special narrow stumping blade, are standard for uprooting by pushing. Stumps should be cut high—at least 36 inches (0.91 m)—for good leverage.
The blade or bucket is lowered to contact the stump a few inches below the top, and the machine is moved forward in low gear. If the stump yields, forward push is continued until the trunk leans so far that effective contact is lost, or until the roots bulge in front of the tracks.
The tractor is then backed, and the edge forced under the upturned roots. Lifting while moving forward slowly should roll the stump out of the ground, breaking all roots except those on the far side. See Fig. 1.12.
Further pushing to get out the far roots may drop or mire the tractor in the stump hole, or may roll up a too-big ball of roots and soil. It may be better to finish freeing the stump by going to its other side.
A number of stumps may be overturned in one direction, then the tractor turned to finish them up from the other.
The same method is followed to uproot a standing tree, except that a high push point is used for greater leverage, and the capacity of the machine relative to trunk diameter is improved.
FIGURE 1.12 Two passes to push out a stump.
Before pushing a tree with any type of machine, the operator should look to make sure that it is alive or at least sound. If a rotten tree is pushed near the base, it may break high up and a top section fall on the dozer. Large dead branches are sometimes dropped with equally disastrous consequences. A dozer to be used extensively for tree pushing should carry overhead guards for the operator.
A tree may bend or split without affecting the roots, in which case the push should be applied lower on the trunk, or from a different direction.
Digging Out. If it does not yield at all to pushing, it must be dug out. This is done by trenching around it with the dozer to cut the roots. Each time the dozer cuts a big root, it may turn and push the stump to see if it is loosened. The operator will often be able to tell when it has been softened up by the way it shakes as the roots break. The ramp need be built only after an attempt to uproot from a lower level has failed.
Roots should be cut as close to the stump as the power of the dozer permits, but it is a waste of time and power to buck at a heavy root repeatedly when it could be easily broken a foot or two farther out and the stub crumpled back.
Pushing over a stump may leave a hole so large that the dozer cannot cross it to complete the tearing out. In this case the dozer may be stopped at the edge, with brakes locked and the blade holding the stump up. The operator can climb down and block the stump from settling back with stones or a log, then back the machine and push dirt into the hole, or break down its edge so that it can walk into the stump.
If an area is to be excavated after clearing, stumps may be left until digging has undermined them and cut many of their roots when they can be easily removed.
Shovel Dozer. A shovel dozer or front-end loader can remove stumps in the same manner as a bulldozer, or make use of the hydraulic control bucket in special techniques. A stump of small to medium size may be dug by tilting the bucket floor downward from 30 to 60 degrees and forcing it into the ground close to the stump, as in Fig. 1.13, using both down pressure and forward motion. With the machine pushing forward, the bucket is then flattened and may be driven under the stump, cutting and tearing the roots, then rolled back, lifting the stump from the ground. If it falls off, the bucket is dropped to contact it and to roll it out of the ground. If it stays in the bucket, it can be carried to a pile or loaded directly on a truck.
The high lift gives the dozer shovel excellent leverage for pushing over trees.
Bucket teeth are desirable for stumping, as they aid penetration, get a better grip on the stump, and are useful for knocking dirt off the ball and for raking out roots.
Methods of handling stumps with a dozer bucket are described in Chapter 16.
Selection of Machinery. Big machines, and special machines, greatly reduce time, effort, and breakage in clearing work, and should be used whenever a job is large enough to justify their purchases or hire. Stumps that can be knocked right out of the ground may be removed at the rate of one a minute or better; moderately resistant ones may take 2 to 5 minutes; and those which are definitely oversize may take an hour or more. It is easy to see the time that can be saved by applying overwhelming power.
FIGURE 1.13 Stump removal with shovel dozer.
A good clearing team may be made from a heavy tractor with a stumper, assisted by a smaller one with a shovel dozer. If these machines work together closely, the stumper can devote its entire time to breaking out the big ones, while the dozer takes out small stumps, knocks down brush, finishes off loosened stumps, piles and removes them, and smooths the ground.
Revolving Shovels. The backhoe is probably the best stumper among the shovel attachments. Usually, the operator tries to take the stump by a direct pull first. If it resists, it can be weakened by chopping roots on the far side and by trenching at the sides. Except in the case of very large stumps, digging and removal can be done from one position. It may be necessary to put blocks against the tracks to prevent the shovel from dragging toward the stump when power is applied.
A dragline is used in the same manner but is less efficient at chopping roots and does not have as strong a pull. However, it can often take out a number of stumps without changing position, and is able to backfill the holes and grade the area at the same time.
A power shovel with a dipper stick is used in somewhat the same manner described for a dozer shovel. It has more penetration and can trench to cut roots more readily but is less maneuverable.
The hoe and the dipper are more effective than dozers in rocky ground and among interlocked stumps, as they can apply their power in smaller spaces. It is often necessary to devote time to digging out rocks before the stump can be attacked. If the roots are strongly entrenched in bedrock or oversize boulders, the rock may have to be blasted before the stump can be pulled.
Rippers and Scrapers. Rippers may be used to cut stump roots and to pull out stumps directly. With two teeth (or one tooth mounted at the side), the ripper can cut roots close to the trunk on all sides. The tractor is then backed with raised teeth to catch the far side of the stump, then forward to pull it over. Another back pass enables the operator to get a tooth under the stump, and lift and roll it out.
Scrapers (nonelevator models) can take out small and low stumps, but this involves complicated maneuvering and danger of getting the stump jammed in the bowl.
Close Quarters. Stumps are often so located that uprooting them would damage pavement or buildings. Such a stump may be removed in chip form, with little disturbance, by a carbide-toothed wheel driven by a tractor or truck power takeoff. Cutting is usually carried 4 to 6 inches (10 to 15 cm) below ground level.
Tree Killing. Under most conditions dead stumps are easier to remove than live ones, because of the disappearance of the hair roots which bind them to the earth and the weakening of the larger roots. Softwoods in well-drained soils may show perceptible weakening in a few months, while rot-resistant stumps in saturated ground may remain firm for many years. In any case, dead stumps contain lighter wood and hold less dirt than live ones.
It may therefore be advantageous to kill trees well in advance of removal in cases where plans are made early enough. This may be done by cutting, girdling, poisoning, burning, or drowning. The same methods are not equally effective in different localities with different species, so advice should be obtained from local tree experts.
Burning peat soils in the dry season will kill trees and loosen the stumps, but because of smoke and smell nuisance, and danger of spreading, it should be done only under carefully controlled conditions.
If it is possible to dam a stream so as to flood a wooded area for several months during the growing season, some of or all the trees may be killed. Unfortunately this usually is possible only in swamps, and swamp trees are more resistant to drowning than those in dry locations.
Stumps may be pulled out of the ground by a cable to a power source. This method, although widely used, is less popular than in the past. Bigger machinery and special attachments have made it possible to push or dig out most stumps encountered on construction jobs, without taking the extra time to rig lines.
However, such equipment is not always available, it may cause too much damage, and it cannot work efficiently on soft ground. Pulling will probably continue to be an important method of stump removal.
The pulling line may be a chain, cable, or rope, and the power may be direct pull by a machine or animal, winding in of cable on a winch, either machine- or hand-powered, or a combination of these methods with pulley blocks.
The stump line is generally a choker type which tightens its grip as the pull increases. In smaller sizes, chain is preferred because it is easier to carry, safer to handle, and more resistant to abuse. However, it is much heavier than cable for the same strength, and in large sizes it is too weighty to be practical.
Line pulling is preferred when the ground is too rough or soft to allow machinery to get at stumps directly, and when available force needs to be increased by multiple lines.
Chains. A more detailed description of chain and fittings will be found in Chapter 21. A standard tow or logging chain is composed of short straight links, carries a round hook on one end and a grabhook on the other. The round hook may be fastened to the chain by a ring, or a ring may be used instead of this hook.
Either the round hook or the ring can be used in chokers. The hook is easier to attach and to detach, but may fall away from the chain when it is slack. The ring may be used by passing the grabhook through it and pulling from the grabhook end; or for stumping, the chain near the ring may be pulled through it to form a loop that is dropped over the stump.
The grabhook fits over any individual chain link, and will not slide along the chain. It is used to adjust the length of chain by increasing or decreasing the amount of double line, by moving it toward or away from the choker end, or by passing the chain behind a tractor drawbar pin, and preventing it from being pulled out again by attaching the grabhook to the slack side, making it too large to be pulled through the space. In this case the surplus chain is slacked, and if it is long, must be hung on some part of the tractor. See Fig. 1.14.
FIGURE 1.14 Grabhook uses, and stump choker.
FIGURE 1.15 Fastening line to stump.
Grabhooks are used to anchor a chain to a tree that is to be saved. The lack of sliding pressure makes it possible to protect the bark by pads and sticks placed on the side receiving the pull. The grabhook may also be used to make a ring which can be used to make up a choker.
Figure 1.15 shows three ways of fastening a line to a stump. In each case, the stump is shown to be grooved by an axe at the back. This cut is quickly made, and will prevent the chain from squeezing off during the pull and delay its slipping off as the stump leans. Part (A) is the easiest and most usual method, pulling at the center; (B) is a side pull, a little harder to arrange, but it puts less of a kink in the line, so that it can be used with cable as well as chain, and gives the advantage of a twist on the stump; and (C) is the overhead method, which requires an inverted T notch. This gives the greatest leverage but is more likely to slip off than the others.
Care should be exercised not to put loads on a chain that is twisted or kinked, as it will be broken or damaged. It can be readily checked for straightness, as the links which are in one plane should lie in an almost-straight line.
Alloy steel chains weigh only about one-third as much as standard chains in proportion to strength. If a crew is careful enough not to lose chains, and is conscientious enough not to abuse them by kinking or gross overloading, alloy chains will amply repay their much higher cost in reduced labor and fatigue, and by greater efficiency.
As an example, one ⅜-inch (9.5 mm) alloy chain, weighing 1.6 pounds per foot (11.6 kg per m), is 30 percent stronger than the same make of ⅝-inch (15.9 mm) ordinary chain, weighing 4.1 pounds per foot (29.6 kg per m).
It is recommended that the alloy chain be dipped in bright red paint so that it can be easily recognized, and recovered readily if mislaid.
Cables. Only the method shown in Fig. 1.15, part (B), should be used in pulling a stump with a cable choker, as the sharp bends involved in the others will cause early breakage of the cable.
If a double cable line is used to reduce strain, or to shorten the rope, it should not be bent around sharp angles. A stump is generally round and smooth enough not to cut a cable wrapped around it, and the end hooks or loops can be attached to the drawbar. If the load is angular, it is better to fasten a snatch block to it with a chain or sling choker, and to run the long cable through the block pulley.
If a double cable is so wrapped around the load that it cannot slide around it, great care must be taken to adjust it so that both ends share the strain equally, unless a single line is strong enough to take the entire pull alone.
Root Hook. A root hook may be used when a stump is too big to pull directly. Enough soil is dug away to expose the lateral roots, the hook is placed to grip one of these, power is applied, and the root is torn out. This process is repeated until the stump is sufficiently weakened to be taken out on one of the root pulls, or by direct pull on the butt.
The root hook may also be laid on top of a stump, with the teeth in a notch on the back. A pull on this gives excellent leverage, but the edge of the stump is liable to tear off. See Fig. 1.16.
Taproots. The presence of a taproot increases resistance of the stump. If the ground is hard, this root may be broken or pulled apart. If the ground is soft, or the wood very tough or pliable, the pivot point may crush and the root bend so that the pulling power is exerted directly against the length of the root, without benefit of leverage. In such a case, the upper roots of the stump may be torn up sufficiently so that an axe, or a special long chisel, can reach and cut the taproot. The cut should be made while pulling, as tension makes the wood part more easily.
Pulling Clear. If the force is sufficient to uproot a stump, the roots opposite the pull break first, then those at the side, permitting the stump to be pulled onto its side. If the line does not slip off, the stump may be rolled and dragged out of the ground, but this often takes much more power than overturning the stump, and may be beyond the capacity of the machine that is doing the pulling.
If the stump will not come all the way, the line may be slacked and a log placed or chained against the stump, as in Fig. 1.17. This log will provide a new fulcrum and aid the breaking out. Or the line may be taken off and the tractor moved to pull in the opposite direction, which should free it without difficulty. If a number of stumps are being pulled, all of them may be overturned one way, before pulling the tough ones in the opposite direction.
Half-uprooted stumps are easily knocked out by dozers, and may be left for them to save the trouble of rerigging.
Resistance. A stump’s resistance varies in different directions. If on a slope, downhill pull is most effective. Otherwise it should be pulled toward its strongest roots, as these are easier to bend than to pull apart, and can be dealt with more easily when the rest of the stump is loosened.
The most obvious variable in stump resistance is its height. Greater height means greater leverage and easier pulling. Limiting factors are difficulty of high cutting and of fastening heavy chains at a height, and the trunk breaking under pull.
A buried stump is the hardest of all to pull and usually must be dug out. On filled land, two separate systems of lateral roots may be found, one under the old ground level and the other near the surface, in which case it may be necessary to cut the trunk below the upper roots, in the same way as a taproot.
A stump which yields to pull but will not break loose can often be uprooted by moving it as far as possible, slacking off to allow it to settle back, and pulling again, repeating this process a number of times. This is most effective if done slowly and smoothly, whether with winch or traction. This method is very effective with trees, as the trunk will bend with a whipping motion that exaggerates the force of both the pull and the snapback.
Chopping the roots on the side opposite the pull, while they are under maximum tension, weakens the resistance. A moderate amount of digging will generally expose the main lateral roots.
When a stump has been split by blasting, the pieces are most easily pulled away from the center, rather than across it.
Uprooting Trees. If trees are so large that their stumps will be difficult to remove, it may be advisable to pull the trees over rather than to cut them down. This gives the opportunity to fasten lines as high as desired and to make use of the weight of the tree. As soon as the tree is pulled toward the tractor, its center of gravity shifts to that side and aids greatly at breaking out the roots. If a large log is chained to its base, on the pull side, the force of the tree’s fall will be more effective at breaking roots on that side. The log will also serve to prevent the trunk from digging into the ground where it would be difficult to cut.
If the tree tends to break or split instead of uprooting, additional chokers may be used below the main pull point to distribute the strain and bind the trunk together. This can be done by pulling with two or more machines, or with multiple lines and blocks that will be described later.
If the trunk is smooth, a ladder will be needed to get a high grip. The chain may be held from sliding down by a nail or a notch, when necessary.
Pulling trees is apt to be wasteful of lumber, as the bottom of the trunk may be put under such strain that it will split when cut.
Pulling Small Growth. Brush and small trees often grow where they cannot be reached by pusher machinery, because of soft or rough ground or nearness to buildings. A landowner may wish to do her or his own clearing without hiring a dozer. Hand cutting may not be satisfactory because of sprouting. In such cases pulling techniques will be applied to small growth.
An automobile has sufficient power for pulling some brush and small, stiff-trunked trees, but the work does not do it any good. Trucks and farm tractors usually put more power on the job and are less likely to be damaged by the exertion.
If the stems are stiff, fastening may be made high for leverage. If they are flexible, height does not matter, and the greater strength of the base may make it the best place.
Chains tend to slide along smooth stems, and they often can be made to grip by wrapping once or twice around before fastening. Light chain with small links holds much better than coarser types. A round hook or ring should be used to make a choker. If stems are close together, it is often possible to pull several at a time by putting a single choker around the group. It will slide up until it can pull them all tight together and then should hold.
Brush tongs get a good grip on small trees and flexible plants, and are easy to attach and to remove, but their weight may outweigh these advantages.
Plants too well rooted to respond to the power available may be weakened by digging out and cutting roots, or pulleys may be used to step up the power.
Power to pull stumps may be supplied by almost any machine or by animals. The crawler tractor is preferred for heavy work, but wheel tractors and trucks may also be used. However, the most power -ful, most convenient, and best controlled pull is obtained from winches. These are most efficient when mounted on crawler tractors, but may be on wheel tractors or trucks, or may be portable units operated by a hand crank.
For general clearing work, the most effective tool is a dozer carrying a power winch. The winch consists of a heavy spool drum that is mounted on the back of the tractor and driven by the power takeoff. It is controlled by the tractor main clutch and the power takeoff engagement lever. In addition it may have a transmission, giving rotation of the drum in either direction, and in large machines permitting several speeds of rotation. A jaw clutch or neutral gear is used to disconnect the drum from the driveshaft, to allow it to turn freely when the cable is being removed. A brake is provided to slow or lock the drum when necessary.
The winch may hold 200 or more feet (61 or more meters) of cable of a size proportionate to its power. Additional cable can be carried on a separate spool and connected to the winch cable by a choker device when needed.
In small sizes, the winch cable generally is fastened at the working end to a short piece of chain equipped with a round hook. Larger cables may be fastened directly, or through a swivel or single link, to a round hook, or a wide-face cable grip hook. The cable is generally underwound on the drum, that is, leads from the work to the lower part of the drum. This gives better stability under heavy load than overwinding.
Stump Pulling. To winch out a stump, the tractor should be placed facing directly away from it, and both brakes locked on. The winch jaw clutch should be released, its brake set to drag very slightly, and the cable pulled to the stump by hand. If the brake is not used, the drum may continue to spin after being pulled, and unwind and snarl the cable.
If the winch will not freewheel, or the cable is very heavy, the drum is turned backward by the engine to pay it out. It is convenient to have two operators, one to operate the winch and the other to pull the cable. If no helper is available, the operator can stand near the winch while it turns, stripping the cable and coiling it on the ground until there is enough. The operator then stops the winch and drags the cable to the stump. The cable must then be whipped up and down and the twists worked out to avoid kinking when pulled.
The winch cable may be put around the stump directly, may be hooked to a choker chain or cable, or may be run through one or more snatch blocks.
Power is applied to the winch and the cable is reeled in, care being taken to see that it feeds onto the drum properly. The stump may come out or the tractor may be dragged backward. If the latter, the tractor may be anchored by a chain from the blade or front pull hook to a tree. Resistance to pull may also be increased by backing it against a log or bank, or by trying to pull the stump by tractor pull and allowing the tracks to spin until they have built mounds behind them. If the anchoring or blocking is effective, the stump will come out—if nothing breaks, slips, or stalls.
The drum carries a number of layers of cable so that it has a greater spool diameter full than empty. It therefore reels in cable more slowly and powerfully on a bare drum than on a full one. On a bare drum, logging winches will give 50 to 100 percent more pull than the tractor itself; on a full drum, the same pull as the tractor or somewhat less. But with torque converter drive, strongest pull may be with a full drum.
Jammed Cables. Using a nearly bare drum not only gives the greatest pull but also reduces damage to the cable. If a long cable is wound smoothly onto a drum under moderate tension, and a heavy pull applied when it has built up several layers, the last wrap may squeeze between the wraps below, as in Fig. 1.18(A). This scrapes and wears the cable and jams it so that it will not spool off again. The best way to free it is to turn the drum until the catch is in the position shown in (B), and jerking it, or anchoring the end and driving the tractor away. Or, in the same position on the drum, the cable may be given a couple of wraps around the drawbar, and the winch turned backward as in (C).
If the cable is wound unevenly onto the drum, with the wraps crossing each other at random, it cannot cut down between lower layers readily, but may put severe kinks in sections of cable that cross under it, and this cross wrapping may not entirely prevent it from squeezing in and sticking.
FIGURE 1.18 Freeing winch cable.
In spite of these difficulties, a long cable is desirable for general work. If reasonable effort is made to spool it in evenly while working, it will usually be rough enough to prevent excessive sticking, without too much bending or crushing.
Two-Part Line. Where the distance to the stump is less than one-half the cable length, a two-part line may be used by attaching a pulley to the stump and by running the line from the winch around the pulley and back to the drawbar. The useful strength of the cable and the pull between the tractor and the stump are doubled.
The tractor may have to be backed against a heavy log or an outside anchor used in the manner to be described below. The tractor should not be anchored by the front pull hook while using a double line anchored on the drawbar, unless the manufacturer states that it is strong enough to take the strain.
Rocking. The winch and tractor pulls differ in quality, and it may happen that the pull of the tracks will do jobs that the winch will not. Use of the tractor drive helps in “rocking” stumps or trees out. The line is left slightly slack, and the tractor moved forward in low. As the line tightens, the stump may lean a few inches, then stop. When the tracks start to spin and the clutch is released, the weight of the stump, combined with the spring in the roots and in the line, will pull the tractor back. The clutch is immediately reengaged and held until the tracks spin or the engine lugs down again.
If the stump is within the tractor’s power range, repeating this maneuver should gradually break it out. A long cable has more elasticity than a short one, or a chain, and will be more effective at rocking.
This procedure should not be allowed to degenerate into yanking, where the tractor is given a long enough slack run to be brought up with a jerk when it tightens. This will break more tractors and cables than it will pull stumps.
Cable Breakage. Cable or chain breakage is a serious danger to both operator and helpers. A cable particularly stretches under strain, and if it breaks suddenly, it may whip with great force. The danger to the operator is greatest if the break is fairly near him or her. The cable used should be the best quality, in the largest size recommended by the winch manufacturer, if the tractor is to be anchored or used for rocking; and it should be inspected frequently for weak spots.
Another danger inherent in the use of cable is cutting and tearing of the hands and clothing on broken wires. Preformed cable gives minimum trouble of this kind and should be used when possible. Leather-palmed gloves are good protection for the hands.
Either hemp-center or wire-center cable may be used, according to preference or manufacturer’s recommendation. Wire center is about 10 percent stronger, size for size, is stiffer, and is not as easily deformed by crushing. It is more difficult to handle, and when kinked or crushed is much harder to straighten. Standard 6 × 19 constructions are usually recommended.
It is good practice to work a winch at less than its maximum capacity, and to avoid anchoring the tractor unless absolutely necessary. Moderate loads give long life to cables and winch parts, and avoid severe catching on the drum. If the work is heavy, strain can be reduced by the use of pulleys and multiple lines.
Broken cables can be repaired by splicing, but the length of cable used in the splice, and the labor involved, may be too great to justify this method for the short cables ordinarily used in land clearing.
A rough repair may be made by trimming back the broken ends, overlapping them as in Fig. 1.19, and fastening them with two or three cable clamps, for sizes up to ⅝ or ½ inch (15.9 or 12.7 mm), or with three or more for larger sizes. Or two interlocked loops may be made, as in (B), fastened with clamps or any type of loop fastening. Cables repaired in this manner are weakened but may last a long time. The patch will not go through pulleys and is inconvenient in other ways.
Winches on Wheel Tractors. If a winch is mounted on a wheel tractor or truck, it is usually necessary to anchor it for heavy pulls. The anchor chain or cable should be attached to the winch frame, or to a heavy member as near to it as possible, to reduce strain on the tractor.
An important consideration in the use of these winches is the fact that the cable will tend to take a straight line between the work and the anchor. In making a high pull, as in Fig. 1.20(A), the tightening cable may lift the tractor and turn it over sideward. In (B) the downward pull may blow the tires, unless the axle housing is blocked up, as in (C).
FIGURE 1.19 Temporary cable repair.
FIGURE 1.20 Vertical effects of winch pull.
If a wheel tractor is not anchored, a rear winch must be underwound, and care must be taken that the machine does not overturn through rising on the front, a danger which is particularly serious if the tractor is driven to move the load.
Truck Winches. A truck winch is usually of the horizontal drum type. It may be mounted in the front bumper, on a flatbed body, or between the body and the cab.
Rotation may be for underwinding, overwinding, or both. Power is from the power takeoff, controlled by the truck engine clutch pedal.
The principal handicap of a truck winch is the difficulty of maneuvering it into position for a straight pull. One or more pulleys may be required to obtain a proper direction of pull and a straight line onto the winch. The truck should have all the wheels blocked, or be anchored by a line from a frame member near the winch.
A gypsy spool or capstan winch (Fig. 1.21) may be mounted vertically on the forward end of a flat body, chiefly for dragging loads onto the truck. A hemp rope is looped around it two or three times, with one end attached to the work and the other end held by the operator. If the operator leaves it slack, the spool will turn inside the rope; if she or he pulls it tight, the working end of the rope will be pulled with great force. The slippage on the spool absorbs shocks that would break the rope and enables it to do very heavy pulling, under exact control. However, the gypsy is not ordinarily used for stumping.
Hand Winches. Hand winches are turned by a hand crank, operating through one or more sets of reduction gears. Under most conditions, it is not possible to make a full turn of the handle because it strikes obstructions, or passes through awkward positions. A large part of the work of winching consists in removing and replacing this handle, and if much work is to be done, a ratchet handle should be purchased, or made up by adapting one from a heavy socket set.
The winch is usually equipped with a friction brake and a pawl that can be engaged to prevent it from turning backward when the handle is released.
Operation of these devices is tedious because of the number of crank turns which must be made to reel in the cable; and exhausting because of the force which must be applied to the handle to develop the rated pull of the winch. It is important that it be thoroughly lubricated.
Hand winches can be used in places inaccessible to power equipment, are comparatively inexpensive, and are surprisingly powerful. Sometimes they can take out tougher stumps than a power winch of the same pull, because the line can be left taut and tightened gradually or from time to time as the stump yields. Their weight, with cable, may be from 75 to 300 pounds (34 to 136 kg), so that carrying one of them any distance is at least a two-person job. It can often be transported in a loader bucket.
Hand winches are sometimes mounted on a truck, in which case they serve largely as a spool to carry cable, most of the pulling being done by the power of the truck. If the job is too heavy for the truck, it may be anchored or blocked and the work done with the winch handle.
If not mounted on a truck or other carrier, the winch should have a V-shaped towbar, or a subframe by which it can be anchored. Planks should be provided to build up a base in line with the pull, since if the line of pull is high, the winch will be lifted off the ground and will not be steady enough to allow turning the handle.
Snatch Blocks. If pulling stumps takes the full power of the tractor or winch, it may be advisable to use snatch blocks to obtain greater power at slower speed. These devices, also known as blocks and as pulleys, are pulleys set in frames that are provided with one or two round hooks or rings, usually on swivel connections. For most field work, single pulley wheels, with a latch attachment permitting insertion of a cable at the side, are best, as cables usually carry attachments too large for threading; a tedious job even when possible.
These blocks can be obtained in sizes to match any cable or strain. In large sizes they are very heavy, and several workers, or a loader, or light winch or other lines may be used to move them.
Figure 1.22 shows several riggings using pulleys. If the lines are approximately parallel, and the pulley bushings lubricated, each additional line will add about 90 percent to the single line pull. This puts no extra strain on the winch cable, but the chokers holding the blocks must take the combined pull of all the lines fastened to them.
FIGURE 1.22 Stump-pulling layouts.
The advantage obtained from the use of a block is decreased when the lines are not parallel, becoming zero when the angle between the lines is 114 degrees. Still wider angles result in loss of power.
The number of lines that can be put on one stump may be determined by the number of blocks on hand, the space available for fastening them, the strength of the available anchorage, or the amount of cable. Light machines may use six or eight blocks on a heavy stump.
Rigging is simplified by the use of series and sling blocks, as in Fig. 1.23. The tractor line –passes around a block pulley to an anchor, doubling the pull at the block frame. This is attached to a heavier line which passes around another pulley to an anchor. The second pulley is pulled with almost four times the power of the winch.
FIGURE 1.23 Use of sling block.
The sling block makes possible the use of a double choker on the tree being pulled. The choker cable is approximately centered in the sling pulley, and both ends are hooked around the tree. Such a double choker can be of lighter and more flexible cable than a single choker.
Rigging. Multiple blocks require care in rigging and pulling. Two anchors are better than one, as they spread the cables over a wider space where they are less apt to interfere with each other. Each block is best fastened to a separate choker, but one may be fastened to each end of a chain passed behind the stump if it is strong enough to take a double pull; or one to both ends of a chain given one turn around the stump. It is good practice to notch the stump for each chain used, so that the chains and blocks will not slide into each other as it yields.
Rigging is done with the lines slack. When they are pulled tight, an inspection should be made to make sure that no pulley latches have fallen open, as a pull on an open block will bend it and cut the cable; that no pulleys are jammed with debris, or liable to pull into each other; and that no chain hooks have become disengaged. As the line is wound in, all blocks should be watched to make certain that they do not collide. Lines should not be allowed to drag on each other.
If the winch does not carry sufficient line for the distance or the number of lines involved, extra line can be added by the use of a take-up block, as in Fig. 1.24. A standard practice is to use the winch line from the tractor to near the first snatch block, and the extra line for reeving. The take-up cannot be pulled through a snatch block, and is liable to cause trouble if included in the multiple lines.
The extra line is often carried on a spool supported on a pipe axle and brackets. This should have a drag brake of some kind, to prevent spinning when paying out. The brake might consist only of a log leaned against the face or side, or a worker’s gloved hand.
Anchors. It is often a question of whether the stump or the anchor will yield. Anchor lines should be as low as possible and stump lines high. It may be best to pull the largest stumps first, using several smaller ones for anchorage if necessary. In a clean-clearing job, there is always one last stump for which there is no anchor, and if it is small, it may be pulled out directly; or in any case it will respond to less elaborate artificial anchors than a large one. On the other hand, a large stump will be a dependable anchor, and will prevent the need of frequent rerigging when anchors pull out.
FIGURE 1.25 Artificial anchor.
The final stump may be pulled by use of a living tree as an anchor. A choker should not be used under any circumstances on a tree which is to be preserved; padding and blocks should be used with a grabhook loop.
If no anchor is available, one may be made, ground conditions permitting, by digging a T-shaped trench, 2 or more feet (0.61 or more meters) in depth, as shown in Fig. 1.25. A log is placed in the crossbar, the cable anchored to it and led up through the sloping trench toward the work. Load and local conditions will determine the depth of cut and size of log. In medium soil, a standard railroad tie 2 feet (0.61 m) down should hold a horizontal pull of 5 tons (4.5 metric tons). This is sometimes called a “deadman.”
Advantages of Blocks. Stump pulling with a winch and blocks takes more time and care than direct winch pull, but results are generally more satisfactory. Jerks and jars which are destructive to machinery and cables are largely eliminated. Lighter cable may be used, and a sufficient number of lines will reduce the tension on any one so much that squeezing and crushing on the drum will not occur.
Methods. Some of the methods for disposing of the ground materials in clearing the land have been discussed earlier in this chapter. For many years in the past, brush, tree slash, and stumps to be disposed of while clearing a site have been trucked off to landfill disposal areas. In addition to the loading and hauling costs, the landfill owners might have charged $30, or so, to dump a load on the landfill. Recently, that part of the cost has been climbing steadily and may now be as much as $400 per load in the United States. With such a high cost there has been an incentive to develop other means for disposing of the wood growth on the land to be cleared.
Special Equipment. Brush and limb chippers have been used extensively for reducing small sizes and quantities to wood chips. The material created in this way generally is small in quantity and is left on the site for ground cover. However, this type of equipment cannot handle stumps and other large logs. To handle and dispose of large quantities and sizes of wood, a different type of equipment is needed.
A heavy-duty wood-processing and stump grinder had to be developed. The challenge was met by Morbark with a piece of machinery called a waste recycler. It is a towable wastewood processing machine with a carbide knife cutting wheel in the tub powered by a 650-horsepower (485 kw) diesel engine. The piece of equipment is rigged with a full-circle-rotating, grapple knuckle-boom for self-loading the material to be ground into chips. See Fig. 1.26. Other manufacturers are now making this kind of wood-processing equipment.
FIGURE 1.26 Waste recycling chipper. (Courtesy of Morbark Industries, Inc.)
One contractor has mounted the waste-processing machine on a crawler track undercarriage so that the machine can be pulled around a large site. This eliminates some of the problems of hauling the timber trash to a central disposal point, saving on labor costs and avoiding a large pile of mulch material.
In the Ground. Dead, dry stumps can sometimes be burned without taking them out of the ground, but the process is usually slow and laborious.
A standard tool for stump burning is a large kerosene blowtorch, called a flame gun. See Fig. 1.27. It may be blocked to flame against a stump. One person can operate several, or do other jobs while taking care of one. When the wood starts to burn, the torch may be moved to another stump and brought back if the fire dies down. Green wood will require continuous heat for many hours.
The torch will operate most effectively if directed into a cavity with an opening in the far end so that a draft can move through it. If the flame is aimed into a dead-end hollow, very high temperatures will be attained, but because of lack of oxygen the wood will distill rather than burn and will be destroyed slowly. If the flame is used against the outside of the stump, it should be directed upward to draw a current of fresh air between the flame and the wood.
Dry stumps may also be burned by starting a wood fire alongside them, and keeping it supplied with logs and snags placed to almost touch the stump. The draft and reflection of heat will keep both surfaces burning, but the loose wood must be moved in rather frequently. This method may remove only the top and outside of the stump, leaving a conical core.
Care should be taken to avoid spreading stump fires. Roots may burn underground to start surface fires at a distance. Soils rich in humus, such as swamp peat or forest loam, may burn unless saturated with water, and are very difficult to extinguish.
In a Pile. Because of difficulties in burial, and scenic and environmental damage in piling, the best way to get rid of a pile of stumps is to burn them. However, it is becoming increasingly difficult to get a permit for the work.
The practical side is also difficult. A stump may cling to more than its own weight of dirt and rock, most of which should be knocked off to make it burnable. This may be done by allowing the dirt to dry, then kicking it around with a dozer or other machine, or by picking up with a grapple and clamshell and dropping.
Even if clean, green stumps are difficult to ignite. If they must be piled before burning, the base of the pile should include a substantial quantity of old tires, preferably topped by a layer of logs.
But the surest way is to burn them at the same time they are piled. Build a hot fire by the methods described in the next section, supply it with enough heavy wood to keep it hot for several hours; then roll, push, or lower stumps onto it, in sufficient quantity to make a thick mass that can sustain fire by itself.
A grapple or clamshell on a power crane is the best machine to feed a stump fire, even if the stumps are pushed to it by dozers. It can place them properly, stack them high, and avoid pushing dirt with them.
Stump fires are very hot and may burn for weeks. There is usually very little smoke, and few sparks.
A great deal of time and effort are wasted in ineffective attempts to burn brush, and for this reason proper procedure will be discussed in some detail.
Even green, wet brush and logs will burn vigorously once properly started, but considerable heat is required to boil off the sap and water, and to ignite the wood. This heat may be obtained originally from a carefully built fire, or by use of flammable chemicals.
Building a Fire. The fire should be on level ground, or on a hump. If built in a hollow or against a rock or stump, inward flow of air will be hindered, and brush added to the top of the fire will be held up away from the heat. All flammable material should be cleared or burned away from around the site, particularly downwind. Fire-fighting tools should be available.
Figure 1.28 illustrates two ways of starting the fire—andirons and tepee. The “andirons” consist of a pair of small logs, or rocks, or ridges of dirt. Twigs and sticks, preferably dry, are laid across the andirons. These should be laid in one direction so that they will lie close together, but should not fit together so well as to prevent air and heat going between them. No leaves or grass should be included.
This pile may be ignited by burning paper, grass, or leaves under it. The material must be dry, and must not be packed tightly, as this reduces the oxygen supply and the heat of the flame.
A self-feeding starter may be made by tearing a section of 10 to 30 pages of newspaper into a strip that will fit easily between the base logs, lying flat. Crumple the top sheet, and light it.
As it burns, the heat will cause the next sheet to curl up and burn. The process repeats for every sheet, keeping a brisk fire going for long enough to ignite dry logs. No kindling is needed, but of course small, dry wood starts faster than thick, green pieces, for which the process may have to be repeated.
When the cross sticks start to burn, more and heavier sticks are added, then partly trimmed branches, and finally, when a good bed of embers and strong flames are present, untrimmed bushes and branches. It is a good plan to put on a few logs or snags at this time to give the fire staying power.
The tepee is similar in principle. The sticks are piled on end around the kindling. As heavier pieces are added, the tepee is crushed, but if it is burning well, this will not matter.
A danger in transition from the hand-tended fire to the roughly piled one is that the untrimmed brush may include so much airspace that the heat cannot cross it effectively. The fire may burn a dome-shaped hole over itself, then die down. In such a case, sticks should be poked into the fire itself to build it up, and the brush over it should be compacted by rearrangement or piling on of heavy sticks. This is tiresome work and may fail. It is better to tend the fire longer before piling on loose material, to be sure it will not have to be worked over afterward.
Artificial Helps. Old tires provide excellent material for starting a fire. Trimmed brush can be piled on them as soon as they are burning.
A dying fire may be pepped up by use of kerosene, fuel oil, gasoline, or similar fluids. To be effective, these must be applied at the base of the pile. Because of its explosive qualities, gasoline should be applied only as a stream from a blowtorch or similar pressurized device with a fine nozzle, and only when it burns as it is ejected. If it does not burn, it may accumulate in sufficient quantity to cause an explosion.
Putting flammable fluids on the heap itself may produce a fine flame, but it will have little kindling effect, as the evaporating fuel will absorb the heat that radiates downward.
Flame guns produce a hot flame up to 20 inches (50 cm) long. They are effective kindlers when directed into the base of a pile.
A brush burner is a portable unit that combines a heavy fan to direct a strong wind into a pile being burned, with a mist of fuel oil for kindling. Few piles can resist one for long. See Fig. 1.29.
If the fire dies down in spite of nursing, it may be best to build a new fire nearby, with greater care to avoid airspaces and coarse, green wood early in its life.
Transferring Embers. Once a good fire is burning on the job, its embers may be shoveled out and used for starting other fires. This should be done rather frequently, as a long brush carry adds greatly to labor costs.
Four or five shovels of hot embers may be laid on the ground in a pile, and fine brush, or dry twigs and wood, piled on it. Or the embers may be sifted down through piled brush. The embers give a sustained heat and consume little oxygen, so that a strong new fire starts quite quickly.
Feeding. It usually takes at least two people cutting and dragging brush to keep one fire burning briskly. If it is allowed to burn down, it is good practice to put the unburned ends in the center hot spot, before piling on more brush.
When a dozer is used, ample supplies of fuel can be brought to the fire, and it is usually well packed by the pressure of the blade and the weight of the machine if it climbs up on the pile.
The principal problem of dozer feeding is dirt. This tends to block the fire from spreading into new material, and to smother parts already burning. Every effort must be made to reduce the amount of dirt by rolling and jostling piles, holding the blade high enough not to dig in, and giving the vegetation and mud a chance to dry before bringing it in.
A hot fire will burn through quite a lot of soil, but it will seldom burn clean. After it cools, the remaining stems and stumps can be sifted out by the dozer and used in building the next fire.
Good results in fire feeding are obtained only if most of the new material is placed on top of the flames.
Burning Piles. If the brush is piled a long time before being burned, dropping a match in it on a hot day may accomplish its complete removal. If it has been piled only a few hours or a few days, a fire may be built on the windward side against it but not under it. This fire may be caused to spread into the heap by keeping it buried under compact brush, so that the fire is fed and the heat reflected into the pile. If the brush has leaves, it is good practice to cover any place where flames show through. A strong fire cannot be smothered with hand-piled brush.
Brush piles may be pushed on top of fires by a dozer, placed by a clamshell, or rolled on by a number of workers using long poles.
If brush is being cut in an area presenting unusual fire hazard, or the cutting is in small, scattered areas, it may be desirable to truck it to a central burning place. A continuous fire may be maintained with incoming loads dozed or hand-piled onto it, or the brush may be piled to dry and burned off occasionally.
Brush up to a few inches in diameter can be reduced to chips by a chopping machine, after which it can either be left on the ground or easily trucked to a dump.
Clamshell. One excellent combination for heavy clearing and burning is a large dozer, preferably with a rake blade, and a clamshell shovel. The dozer uproots and pushes in brush and trees, and the clamshell picks them up, shakes dirt out, and places them on top of the fire. See Fig. 1.30.
The clamshell can also maintain a fire, moving in unburned ends, and can bury it under dirt at the end of the work day.
FIGURE 1.30 A good fire tender.
A clamshell is also often the best tool for high stacking of vegetation that is to be left to rot, and for burning old piles that need rehandling.
Banking Fires. If the job is not extensive enough to justify the employment of someone at night to watch the fires, and any flammable material is nearby, they should be buried under a few inches of clean dirt at the end of the work. Humus or rich topsoil should not be used. The soil cover will prevent sparks from blowing, will preserve a hot bed for use in the morning, and, if the cover is not removed, may make a fair grade of charcoal.
Any contractors burning brush in an area subject to brush or forest fires are subject to heavy responsibility if one of their fires spreads. Also, in the presence of extensive forest fires from any cause, contractors may be required by authorities to use their workers and equipment to control them. At such a time there might not be experienced fire-fighting personnel available to direct the work. A brief outline of fire-fighting techniques is therefore considered appropriate.
Hand Tools. Where the material burning is largely grass and associated weeds, or thin brush, fire can be beaten out. Household brooms, occasionally dipped in water if possible, are very effective. Shovels or leafy bushes or branches can be used with good effect. Each blow should be directed so that flying sparks are knocked toward the burned area.
The fire may also be starved by scraping away the vegetation just beyond the flames. This may be done with shovels, hoes, rakes, grub axes, or almost any piece of metal. A special type of fire-fighting tool, shaped like a heavy rake and fitted with sickle bar teeth instead of tines, is quite effective. Bushes may be cut with axes, machetes, bush hooks, or pruners.
Extinguishers. Backpack fire extinguishers, which consist of a water tank carried like a knapsack, a flexible hose, a hand pump, and a nozzle, are important pieces of equipment. See Fig. 1.31. If the grass is low or thin, spraying in the path of the fire may stop it. If the fire is strong and moving rapidly, the water may be most effectively used for putting out smoldering spots behind the beaters. Addition of a wetting agent—a small quantity of almost any detergent will do if regular compounds are not available—increases the effectiveness of the water by enabling it to soak through vegetable litter and punky wood.
Pumps. If streams or ponds are available, the contractor’s pumps, particularly the light centrifugal type, are very valuable. A welder or machinist can usually make adapters quite quickly that will permit fire hose to be attached to the pump outlet. The high pressures used in regular fire pumps will probably not be developed, but sufficient pressure will be available for wetting down firebreaks or making direct attacks on anything short of a crown fire.
Sprayers. Tree-spraying outfits make good fire fighters. These usually consist of a tank holding from 200 to 500 gallons (757 to 1893 liters); a high-pressure pump driven by a small gasoline engine, or by the power takeoff of a towing tractor, or a carrying truck; a reel of hose; and a nozzle. Those having an engine are generally mounted on a wagon chassis that can be towed by almost any motor vehicle. If the pump is tractor-driven, adaptation to most wheel tractors can be made quickly. The handiest models are those mounted on a motor truck.
Such equipment can generally be rented or borrowed in almost any area. The volume of water delivered through the nozzle is small, but pressure is high and results are usually excellent.
Dozers. A bulldozer can put out a grass fire by starting behind the fire and straddling its line, as in Fig. 1.32. It may be able to scrape off the grass without cutting much into the ground. If this is not practical, it can skim off the sod until the load is heavy, then swing it into the burned area, or raise the blade and spread the sod over the next few feet of flames, smothering them. An angle dozer can sidecast the sod into the burned area, and a hand beater, or extinguisher, should follow to put out any spots that are missed.
FIGURE 1.31 Backpack extinguisher.
Method of Attack. Windblown fires should not be attacked directly at the front, as this procedure is both dangerous and ineffective. A new fire running before a wind will assume a shape similar to that in Fig. 1.32. A direct attack on the front means fighting flames several feet deep. If these should be put out, fire blowing up the sides could rekindle them in a few seconds. A crippled person or machine ahead of the fire could not escape being burned.
Pinching off the sides is both effective and reasonably safe. The fire is extinguished starting at the back so that the heat and smoke are blown away from the workers. Provided a constant watch is kept behind them for rekindled spots, the fire cannot repossess the extinguished area. When the front is reached, it is attacked from directly behind as well as on the sides.
If the fire is too strong for the force fighting it, the front will continue to advance, but the work on the flanks will limit its width and make easier the task of stopping it with firebreaks or backfires, or after a shift in wind direction. It can sometimes be turned by concentrating on one flank.
FIGURE 1.32 Fire-fighting with dozers.
Firebreaks. A firebreak is any strip bare enough of flammable vegetation to delay or stop the spread of fire across it. Roads, open water, plowed fields, close-cut lawns, and even footpaths may be used. In addition, breaks may be prepared in anticipation of fire along the crest of hills or mountains, at property lines, or at the edge of the areas being cleared.
Advantage should be taken of any existing breaks when deciding where to place one to stop a fire already burning. A short line is preferable, and valuable property or highly flammable areas should be protected. The break should be far enough from the fire to allow time to finish it and to start backfires; it should be in vegetation least apt to make a spark-producing or a high fire, and on terrain favorable to operation of machinery. A compromise among these features must usually be made.
A bulldozer may be walked along the line of the break, alternately cutting and filling, so as to mix the vegetation with dirt. Hand workers with cutting or digging tools follow, to cut out any spots where fire might cross. If the brush is heavy, the dozer may turn to push heaps of it out of the path. An angle dozer or a heavy grader might be able to make a single clean cut in each direction, turning the sod and brush out from the center.
In grass or light brush, a plow or heavy disc harrow might do a better or faster job than a dozer. The plow makes a rather narrow strip with each trip, and is subject to jamming with brush but does not have to go back over its work. A harrow may require several trips and might not be effective.
The hand tools listed earlier may be used to build a complete break, or to work one over after the machinery has passed.
Backfires. A strong fire adds to the force of the wind which is moving it, somewhat as a blowtorch builds up its fuel pressure. The combined force may be enough to project a sheet of flame many feet in front of the burning line, and to shower sparks for long distances ahead. For this reason, the fire may cross a break of any practical width and make the area too hot for fire fighters.
The principal use of the firebreak is to provide a line from which backfires can be started. Since the break is made on the downwind side of the fire, a new fire started on that edge burns upwind. The backfire should be made in a continuous strip along the break so that it will not be able to turn and blow back toward it. It will increase in strength as it progresses, but will be steadily farther away from the protected side. When it meets the main fire, there is liable to be a spectacular flareup and heavy production of sparks. If the backfire has been started in time, this should be far enough away from the break that few sparks will cross it, and those can be extinguished by men patrolling the break. If no shift in wind occurs, the sides of the fire can then be put out by the crew working from behind, aided by the firebreak crew.
If the break is made in a forest where the flames might crown (burn in the tops), the trees on each side of the break should be bulldozed or cut so as to fall away from the center.
Since a change in wind direction may occur at any time, care should be taken not to start backfires prematurely, and to keep workers and machines in positions where they can get away if the fire turns toward them. The burnt-over area, ponds or wet swamps, and plowed land or well-grazed pastures are suitable retreats.
Workers on the fire lines must be kept provided with food, water, and tools, and relieved for rest periods. Machinery must have fuel but may be skimped on other maintenance in sufficiently dangerous situations.
Backfiring, and possibly other phases of fire fighting, may be regulated or prohibited by local laws.
Rekindling. After the spreading of a fire has been checked, it must be patrolled until all danger of its making a fresh start has passed. A grass fire in a clean field may be safe to leave within an hour, while wooded areas containing dead or fallen trees, or rich dry soil, may be dangerous until after several soaking rains.
Dead stumps may burn a long time and are difficult to extinguish unless ample supplies of water are available. Fires burning under and between logs on the ground can often be put out by moving the logs apart, or can be caused to burn out more quickly by piling additional wood on them.
The worst hazards are standing dead or hollow trees, called snags by the lumbermen. If close to the line, snags may set fire to the unburned area by falling into it. They frequently produce sparks that may drift long distances. Even thorough soaking may not extinguish them, and it may be necessary to cut them down or maintain an expensive patrol for days or weeks.
Cutting a burning tree is a tricky and dangerous job, as the cutters are in constant danger of being hit by falling pieces, and temperatures at the base may be too high for them or their tools. This job is best left to experienced fire-fighting crews.
Snags may be pushed over by bulldozers, but the tops are apt to fall on the machine. A cab with maximum-strength overhead protection is needed for operator safety.
The best time to check a burned area for hot spots is immediately after a rain, or a heavy dew, as the moisture near the fires will steam.
Underground Fires. Underground fires, such as occur in rich forest soils and dried-out swamps, constitute a special problem. When fire gets in them, often by smoldering down a dead root, they will burn hot and persistently. Plain water has little effect on such a fire unless applied in such quantities that the area is flooded. Smaller quantities do not penetrate the deeper burning zones, which have sufficient heat to evaporate quantities of water from surrounding peat, and then spread through the dried material.
Special nozzles consisting of pipes long enough to reach the bottom of the fire are helpful. The lower end is plugged, and a fairly large hole is drilled in the plug to wash humus out of the way as the pipe is pushed down, and smaller holes in the side spread a soaking spray. The use of wetting agents will substantially reduce the amount of water required, and may make the difference between success and failure where the water supply is limited.
Such a fire may be confined by trenching down to inorganic or saturated soil. The digging may be quite difficult because of roots, and a backhoe or dragline shovel might have to be used.
FIGURE 1.33 Incineration box by Air Burners, LLC.
Peat fires spread very slowly unless they ignite surface vegetation or litter which set fire to the soil at new points. If equipment is not immediately available to extinguish or ditch the fire, leaves and flammable trash should be removed for 10 or more feet around it, to prevent rapid spreading while arrangements are made to put it out.
Burning Box or Trench Air Burners’ system (see Fig. 1.33) provides a method for burning wood products on site in either a refractory-lined box or an earthen-lined trench. The operating prin -ciple of the air curtain within an incineration setup is based on a controlled high-velocity stream of air across the upper portion of the combustion chamber in which the clean wood waste is loaded. For proper operation the air curtain machine has to provide a curtain of air over the fire that has a mass flow and velocity that are in balance with the given mass flow and velocity of the burning wood waste. When done well the ash from the typical wood waste is a very useful soil additive, and as such offers a commodity that can be marketed to plant nurseries and farms as a potting soil additive.
Boulders. An area may be so strewn with loose or partially buried boulders that work is difficult, and the removal of these rocks may properly be considered clearing.
If large enough machinery and suitable disposal points are available, the rocks may be turned or dug out and pushed away. If they are too large for easy handling and disposal, they should be broken up.
Breaking may be done by blockhole or mudcap blasting, backhoe-mounted demolition hammers, drilling followed by plug and feathers splitting, or a muscle-operated sledgehammer. See Fig. 1.34.
A plug and feathers set consists of a pair of half-cylinders (feathers) with outer surfaces fitting in a drilled hole, with inner faces shaped for driving a thin steel wedge (plug) between them by air or hand hammer, or by hydraulic pressure.
The very gradual taper of wedge and cylinder halves causes blows or pressure on the plug to be converted into a tremendous sideward pressure, which can split large boulders and break off chunks of bedrock.
Under many circumstances, however, a contractor may prefer to get rid of the rocks by digging and pushing. The dozer is the standard tool for this work. Efficiency can be increased by use of a tilting blade, a dozer shovel bucket, a stumper, or a heavy-duty rake blade.
A dozer can move quite a large rock on firm ground, perhaps several times its own weight. If the stone is too large for direct pushing, it can be pushed first on one side, then on the other. If it is rounded, it can be rolled by lifting the blade while pushing. If the blade does not have enough lift to control it over, it can hold it in a partially rolled position, with locked brakes, while the stone is blocked up. The blade may then be lowered and the push and lift repeated.
Partly buried rocks may be pushed or dug out in somewhat the same manner as stumps. The resistance they offer is usually more rigid than that of stumps, and if a rock will shake in the first few direct blows of the blade or bucket, it should come out. It is sometimes very difficult to get a grip on smooth sloping surfaces, so that an excessive amount of digging must be done just to get a hold.
When a grip is obtained with a dozer blade, the rock may be raised and pushed. The engine clutch should be slipped, or the converter-equipped engine throttled so as to supply just enough forward pressure to keep the blade in contact with the rock while it lifts it vertically, and, when it is high enough, rolls it out. The rock may slip back into its hole at any time, and it is good to have a helper throw stones or logs under it so the blade can be dropped and a fresh grip obtained. If no helper is available, the operator can lock the brakes to hold pressure against the stone and do the hole filling himself or herself.
FIGURE 1.34 Boulder split by plug, hydraulic-powered.
If a big stone is rolled out without blocking, it may leave such a large hole that the tractor may be damaged if it falls in it. The danger is more serious than with stumps, as rocks leave sharper-edged and harder holes.
A rock should be pushed from all angles before digging it out, as it may be susceptible to pressure from only one direction. If it is to be dug out, a bowl-shaped crater of considerable size is excavated, working on three sides, if a good grip is available at the top, or all around it if the top is smooth. When it is finally loosened, it may be found that it is so heavy that the dozer cannot get it up out of the hole.
It probably can be pushed out by following the procedure outlined in Fig. 1.35. The dozer builds a ramp out into the crater, shaped so that the machine will be pitched downward when its blade meets the rock. With gravity assisting, it should be able to push the stone a short distance up the opposite slope. The ramp is then built out, and another push made until the stone is out of the hole.
Loose boulders may be pushed out of the work area and scattered, piled, or arranged in walls; or they may be buried, being either used as a fill or wasted in holes. Holes may be dug to bury them.
Where many boulders are pushed into a hole they afford unsafe footing for a bulldozer and may pile up above the desired grade. A moderate amount of dirt, either scraped off the bank or trucked to the spot, will allow the dozer to fill in the holes and stabilize the rocks so that it can walk across them in pushing other boulders to their resting place.
If the area is to be finished to a grade, it pays to be liberal in supplying covering soil, for if the layer is thin, the dozer working on it may hook into freshly buried rocks and turn them into high positions. They can seldom be put back in place because of soil and other rocks getting under them, and it may be necessary to knock their tops off with hammers or explosives, or dig them out and rebury them. Digging a boulder out from among others is very difficult, and is likely to turn them up.
Rocks may be trucked away from the job. They may be loaded by lifting in or on a loader or dipper shovel bucket, by clamping in a clamshell or grapple, or between a hydraulic hoe bucket and the stick.
FIGURE 1.35 Getting boulder out of a hole.
Or a crane may lift them by tongs, chains, or cable slings. Light chains grip well, but are easily damaged.
Ordinary dump truck bodies may be severely battered by oversize rocks. The floor may be protected by an extra sheet of steel, a layer of planks, or just a few inches of dirt.
Stone Walls. Stone walls built to dispose of boulders removed from farmland are very common in some sections of the country, and may include rocks large enough to present a problem to machinery. The big base stones are often partly or completely buried, interlocked, and bound in place by tree roots. The smaller stones may be valuable for use in masonry, and may be removed by hand before or during the wrecking of the wall.
A dozer of sufficient size can walk right through the wall and scatter it around, but an under-size machine may have to start at a gateway, or find a weak spot to break through and widen the hole by worrying the rocks out one at a time. If the wall cannot be broken from one side, it should be tried from the other.
Foundations. Old foundations and other masonry structures usually yield readily to heavy machinery. High walls should be pulled down, as they might fall on a machine pushing them.
If a foundation is too strong for available machinery, it may be weakened by blasting along the lines where it meets the floor and other walls, by mudcapping or drilling. Demolishing very heavy or extensive structures, however, is a house-wrecking job out of the field of this book.
