Andy Smith
MIne-action specialist

Manual removal of undergrowth - general (2005)


The picture above shows a deminer using a vegetation trimmer in Cambodia.


Section 1: Manual removal of undergrowth

1.1 General

What follows are basic procedures for the clearance of undergrowth using handtools. They are intended to provide a basis that you can edit and refine to suit your equipment and working preferences.

Whenever there is significant undergrowth, the use of mechanical assets to cut the undergrowth in front of manual demining should be considered. Whenever the Risk/Threat assessment for the Task indicates both the presence of undergrowth and active tripwire activated devices, the use of mechanical assets to remove the vegetation is always prefered.

The Manual clearance of undergrowth drill leads directly on to the Metal-detector set-up, Metal-detector search and Signal-investigation procedures.

1.2 Approved tools

All currently approved tools used for the manual removal of undergrowth are powered by the user except for the petrol-driven back-pack "Trimmers". There are restrictions on the manner in which each tool can be used and the places in which their use is appropriate.

The tools generally made available for undergrowth clearance are listed below. At any one Task, one or more of these tools may be deployed. At some Tasks, all will be appropriate for deployment. The deminers shall always be issued with appropriate tools for the Task and have access to strong "gardening" gloves.

A: Shears
B: Secateurs (pruners)
C: Sickle (hook)
D: Saw (one-handed)
E: Wire-cutters
F: Brush-rake (with or without magnet attached)
G: Petrol-driven "Trimmer"

The picture shows examples but designs may vary. Deminers are not obliged to wear "gardening" gloves but they must be available whenever undergrowth includes thorns, is sharp, or has stinging or skin-irritant properties. The gloves are provided to give significant protection in the event of an explosive accident. They protect against the cuts and scratches that can occur during undergrowth cutting.

A deminer engaged in clearing undergrowth will often have a tripwire feeler, hammer and shapening tools amongst his/her tools. None of these must be in the tool-bag but it will sometimes be appropriate for them to be present. (The hammer is used for driving in marking stakes where wooden markers are used.)

A: flat-faced Hammer
B: Tripwire-feeler
C: Sharpening stone
D: Fine toothed file

 

1.2.1 Safety contraints on tool use

All tools could be used in a dangerous manner, but some are hard to use in a safe manner at any time. The following tools may NOT be used in any area that has not yet been declared safe (or presumed safe).

Panga; Machete; Scythe; Chainsaw; axe/hatchet

This prohibition is made because the user cannot reliably control the tool (or the undergrowth it cuts) in a manner than guarantees that there are no impacts on an irregular ground surface. These tools may be used in safe areas, but should never be inside the working area during clearance.

In addition to the tools listed above, the following tools may not be used in an area where the Risk and Threat assessment indicates the presence of tripwire initiated mines or other sensitive devices on the ground-surface (unless that Threat has been removed by mechanical preparation):

Petrol-driven "Trimmer"; Brush-rake

Other constraints include:

When using shears, sickle or saw, the blade(s) must not be inserted into the undergrowth beyond the area that has been visually checked or through which fingers have not passed feeling for obstructions.

When using a sickle (hook), the stem(s) to be cut must be gripped in one hand and cut carefully using the tool with the other hand. The tool must never be swung at the undergrowth in a scything motion.

When using a petrol "Trimmer" the operator should wear frontal leg protection unless the design of the "Trimmer" removes all chance of a broken blade or blade part being thrown back towards the operator. The operator must always ensure that the cutting blade does not touch the ground. The operator should always ensure that his/her feet never leave the safe area.

When using secateurs/pruners, care should be taken not to pull the undergrowth as it is cut. An anvil blade arangment is preferred to limit accidental pulling.

When using a Brush-rake, the tool can only be used on areas that have been visually checked for surface items. The user must always work standing and hold the handle so that he is as far as practicable from the Brush-rake head.

All tools must be in good condition with appropriately sharp blades. Shapening stones and files should be available in the rest area when required.


1.3 PPE during the removal of undergrowth

The removal of undergrowth is normally part of a complete clearance cycle and the same PPE must be worn during every stage. The minimum requirement is that 5mm polycarbonate (or equivalent) eye protection must be worn (in a position that protects the eyes), and that frontal blast protection for the body and groin is worn. Other PPE may be required when the threats in the area are identified as being greater than that posed by anti-personnel blast mines.

It is the responsibility of the Task Supervisor to ensure that appropriate protection against the perceived threats is issued and worn in the correct manner.

 

1.4 Tripwire location

When the Task Assessment indicates a possible threat from tripwire operated mines with functional fuzes, the Clearance Plan will normally require the use of machines for mechanical preparation of the area. Whenever possible, vegetation removal machines will be deployed in a manner designed to ensure that no intact tripwires remain before manual deminers are deployed. The same machine may be set to deliberately strike fuzes, so breaking them from the mine body or initiating the mines.

When it is necessary to use a manual demining tripwire detection procedurel, a tripwire feeler can be used to locate tripwires in advance of the Base-stick or Base-trench. The feeler is made from light-gauge wire or thin, flexible wood (such as bamboo). When the vegetation does not allow the use of a tripwire feeler, the search can be made using the eyes and hands. After a thorough visual check of the area, the deminer searches the area by gently parting any thick vegetation that may conceal tripwires, unexploded ordnance, surface-laid mines, protruding fuses or other suspicious objects.

 

1.4.1 Using the Tripwire feeler

1) The deminer must be in a kneeling or crouching position when using a tripwire feeler.

2) The tripwire feeler should be moved along the ground on the left hand side of the lane, forward of the Base-stick (or Base-trench) to a measured distance - usually between 30 and 50 centimetres depending on the undergrowth.

3) The tripwire feeler must then be raised slowly upwards until clear of the undergrowth or above the deminer's head. The deminer can use the fingers of his free hand to part undergrowth so that any obstruction can be seen.

4) Stages 2 and 3 should be repeated in the centre of the lane and on the right-hand side.

After conducting a tripwire location procedure, the deminer must take great care not to cut undergrowth ahead of the area investigated.

After conducting a tripwire location procedure, deminers using a metal-detector may be required to pass the detector-head through the undergrowth at varying heights as a secondary check. (This method does not work reliably with all models of metal-detector, so is not a general requirement.)

 

1.4.2 Action on locating a tripwire

When a tripwire is found, the deminer must stop work and notify a Supervisor. The Supervisor is responsible for ensuring that the full length of the trip-wire is uncovered without pulling it. Generally, a one metre wide lane parallel to the tripwire (and on one side of it) is cleared in order to safely locate both ends of the wire. When a tripwire is taut, the tripwire must not be moved or disturbed until the ends are exposed and the threat identified. When a tripwire is slack, it may be cut at the discretion of the Supervisor and in the interests of safety.

All task activities within 30 metres should be stopped until the ends of the tripwire are located and action is taken to remove or destroy any linked device.

 

1.5 Manual vegetation removal procedure

The hand-clearance of vegetation must be conducted in a controlled and deliberate manner, avoiding any disturbance of vegetation outside the width of the lane and the safety overlap. Before and during the cutting, the deminer must make repeated visual checks for any item that has become visible.

Generally, trees with a trunk diameter of 10cm or less should be removed during manual work. Exceptions may occur when the undergrowth has a crop-value, such as bamboo. When mature trees are left, the area immediately surrounding the base of the trunk must be cleared to a radius of 2m in order to allow a stretcher to pass, so the relevant lane(s) must be deflected around both sides of the obstruction.

Grass is usually cut to ground level in stages that ensure that surface devices would be seen before that level is reached. During metal-detector use, cutting the undergrowth to ground level maximises the detection depth achieved by keeping the search-head in close proximity to the ground surface.

Undergrowth must always be cut rather than torn or broken.

Depending on the Risk and Threat assessment, it may be necessary to check high branches of mature trees for air-delivered munitions such as cluster bombs. When appropriate, the deminer should complete a full examination of the trunk and all low branches before and during the following procedure.

1) When undergrowth is so tall that it might fall outside the cearance lane when cut, it must be cut in lengths that allow the deminer to hold it and remove the cuttings to the cleared area behind. This can be done from a standing position for taller undergrowth.

2) When undergrowth is unlikely to fall outside the working area, the deminer should work on his knees (unless adverse ground conditions prevent this). Usually, the undergrowth will first be cut to a height of approximately 15cms above the ground. Exceptions to this "first stage" height may be made when the Threat assessment for the Task suggests that large items may be on or above the ground surface. All exceptions must be documented by a Supervisor (usually in the Site Log).

When using a one-handed cutting tool, the deminer should use one hand to hold the undergrowth while the other uses the tool to cut it. When using shears, the deminer should endavour to catch the cuttings as they fall, then remove the cuttings to the cleared area behind.

3) Before making a final cut as close as possible to the ground surface (without touching it), the deminer should look for any indication of devices. This may include areas where no undergrowth is growing. If necessary to see clearly, the deminer should cut the undergrowth closer to the ground in further stages.

4) When the deminer is confident that the tool he uses will not strike any devices, the deminer should cut the undergrowth as close as possible to the ground surface. Because stem thickness often increases near the ground, the deminer should use secateurs (pruners) when appropriate.

5) Any cut undergrowth in the area should then is then removed by hand or by using a Brush-rake. The use of the Brush-rake will depend on the Threat assessment for the Task.

6) Cuttings should be stacked outside the clearance lane for later disposal. Cuttings must always be stacked in an area that would not impede emergency access to the working lanes. Specific areas may be allocated for placing cuttings close to the deminer.

Destroying cut vegetation by burning shall be conducted in a controlled manner inside a safe area after all demining work at the Task has stopped. When burning is not appropriate, cut undergrowth should be stacked in a safe area where it causes no obtruction.

Devices that are located during vegetation removal should be left where they are until the ground up to them has been cleared. The deminer must stop work and notify a Supervisor if unrecognised devices or devices attached to (or hanging from) trees are discovered. The deminer may also be required to stop work and notify a Supervisor when any other device is discovered.

 

1.5.1 Using the petrol-driven trimmer

The petrol-driven trimmer may only be used by a deminer who has been internally trained and certificated for its use. Usually the same person is responisble for its maintenance and for the correct storage of its consumables (oil and petrol). Petrol may not be kept with 25 metres of the explosive store or rest area and must be stored in a protected area where smoking and naked flames are restricted.

When the Supervisor decides to deploy the trimmer, it is usually to to cut a swathe along one side (or both) sides of cleared (or safe) lanes.

Before Trimmer use, the Task Supervisor must ensure that an appropriate means of communication is in place. The noise of the machine prevents voice communication being adequate. When hand-held radios are not available, a simply flag-system can be used and the immediate Supervisor of the Trimmer operator must carry the relevant flag(s). A red flag always indicates the need for work to stop, and may indicate other actions during other procedures. When the flag system is used, the deployment should ensure that the Trimmer Supervisor remains in line-of-sight of the Trimmer Operator at all times. As work progresses, the Trimmer Operator must glance towards the Supervisor before moving position, checking to see whether a red-flag is raised.

Precise use and control of the Trimmer varies with each design. However, the following constraints apply whatever model of Trimmer is used:

1) The Trimmer operator should not put the cutting head in/over the uncleared area until all other personnel are at the safety distance appropriate at the site and documented in the Task assessment.

2) The trimmer operator must wear frontal PPE, and should also wear leg protection when the design of the tool makes this desirable.

3) The Trimmer operator must take all care to keep his/her feet inside the safe-area.

4) The Trimmer operator must not allow the cutting head of the tool to strike the ground at any time.

5) The Trimmer operator should not move around the safe-area with the clutch to the cutting tool engaged.


1.5.2 Burning-off vegetation

Burning-off vegetation prior to clearance can be conducted when the right conditions occur. These conditions are:

a) The clearance plan for the Task does not include the deployment of explosive detecting dogs for at least seven days after the burning.

b) The Task Threat assessment has not identified a high chance of plastic-cased mines on the ground surface.

c) A broad (usually at least two metres wide) fire-break can be made on all sides of the area to be burned.

d) The undergrowth must be low and dry. (Generally, dense or green undergrowth should not be burned-off because it will not burn well.)

e) Essential area-marking must be either already fire-resistant or replaced with fire-resistant markers, such as painted stones and metal pickets.

f) There is no expectation of high winds.

Controlled burnings are subject to the following additional constraints:

1) No demining work should be conducted within the Task safety distance of the area to be burned or in any area where smoke drifts.

2) Sentries must always be posted to prevent people or livestock entering the area during a controlled burning.


NEXT: Metal-detector set-up, and Metal-detector search

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