OPERATIONS PROTOCOL FOR ECO-EFFICIENT WOOD
HARVESTING ON SENSITIVE SITES
Quick Reference Card
© ECOWOOD Project (www.ucd.ie/~foresteng)
Step 1
Soil
Strength Score
(1 to 4)
1
Strong
2
Average
3
Soft
4
Very Soft
Cone
Index
(kPa)*
> 500
E
Shear Strength
(kPa)
> 60
> 60
300 –
500
< 300
20 - 60
20 - 60
< 20
< 20
<<300
<<20
<<20
Classification of soil strength based on three soil strength indices. The classification is
based on the lowest index – i.e. the parameter value that falls into the lowest soil strength
category. If none of these three measurements are available, estimate the soil strength
category based on visual observations and local knowledge.
Step 2
Match the Soil Strength
to the Ground Bearing
Capacity (kPa)
Relating Soil Strength to Ground Bearing Capacity (GBC)
Soil Strength
General Description of
Ground Bearing
Score
the Soil Types*
Capacity (GBC)
(1 to 4)
Dry sands and gravels;
High GBC
1
Firm mineral soils
> 80 kPa
Strong
Soft mineral or iron-pan
Medium GBC
2
soils
60 – 80 kPa
Average
Wet gleys and peaty
Low GBC
3
soils
40 - 60 kPa
Soft
Wet peats
Very Low GBC
4
< 40 kPa
Very Soft
* These descriptions will vary with soil wetness
Soil Classification
Classify the Soil as Strong,
Average, Soft or Very Soft
Step 3
Classify the Terrain
Terrain classification*
Soil Strength Score
(1 to 4)
1
Strong
2
Average
3
Soft
4
Very Soft (not suitable for
machine traffic)
Ground Roughness
Score (1 to 3)
1
Even
2
Uneven
3
Rough
Ground Slope
Score (1 to 3)
1
Gentle (< 8o or 14 %)
2
Intermediate (8o – 14o or 14 - 25 %)
3
Steep (> 14o or > 25 %)
Step 4
Match Terrain Classification to
Harvesting System
Matching Terrain Classification to Harvesting System
1.1.1
2.1.1
3.1.1
4.1.1
Tracked Forwarder,
Forwarder, Skidder, Horse
Cable
1.1.2
2.1.2
3.1.2
4.1.2
Forwarder, Skidder, Horse
Forwarder, Tracked Forwarder, Cable
1.1.3
2.1.3
3.1.3
Forwarder, Skidder, Horse
1.2.1
2.2.1
Cable
3.2.1
Forwarder, Skidder, Horse
1.2.2
2.2.2
Forwarder,
Forwarder, Horse
Tracked Forwarder
1.2.3
2.2.3
Chained Forwarder, Cable
1.3.1
2.3.1
Forwarder, Cable
1.3.2
Forwarder, Cable
1.3.3
2.3.2
Forwarder,
Tracked Forwarder,
Cable
2.3.3
Cable
4.1.3
3.2.2
4.2.1
Tracked Forwarder,
Cable
4.2.2
Tracked Forwarder, Cable
3.2.3
4.2.3
Cable
3.3.1
4.3.1
Tracked Forwarder, Cable
3.3.2
4.3.2
Cable
3.3.3
4.3.3
Harvesting System Selection
* Combine Soil Strength with Ground Roughness and Slope to classify the terrain. For example, a
soft soil with an uneven surface on a steep slope has a Terrain Classification of 3, 2, 3
Step 5
Select a Harvester with
NGP less than GBC
Nominal Ground Pressures (NGP) for typical harvester configurations
Typical NGP
> 80 kPa *
Typical NGP
50 – 70 kPa *
3 axle harvester, tyre widths range from 500 – 800 mm
Typical NGP
45 – 60 kPa *
4 axle harvester, typical tyre width = 600 mm
Typical NGP
< 30 kPa *
Tracked harvester
* NGP is dependent on tyre / track size and general machine configuration. Further
details can be obtained from the machine manufacturers.
Harvester Selection
2 axle harvester, tyre widths range from 500 – 800 mm
Step 6
Select a Forwarder with
NGP less than GBC
Typical NGP
70 - 80 kPa *
Typical NGP
50 - 60 kPa *
Typical NGP
50 – 60 kPa *
With Band Tracks fitted:
Typical NGP
40 – 50 kPa
* These NGP values refer to fully loaded forwarders and are dependent on tyre / track size and general vehicle
configuration. Band tracks significantly reduce the NGP. Further details can be obtained from the machine
manufacturers.
Forwarder Selection
Typical NGP
80 – 100 kPa*
GENERAL CONSIDERATIONS
FOR ECO-EFFICIENT MANAGEMENT OF WOOD HARVESTING ON SENSITIVE SITES
IT IS MOST IMPORTANT TO HAVE AN EFFECTIVE HARVEST SITE PLAN IN PLACE THAT COMPLIES WITH ALL LOCAL
AND NATIONAL GUIDELINES ON FORESTRY, FISHERIES, ARCHAEOLOGY AND LANDSCAPE. OPERATIONS MUST
BE CARRIED OUT UNDER THE GUIDING PRINCIPLES OF SUSTAINABLE FOREST MANAGEMENT.
Categories of site damage and degradation due to machinery operations are listed, and the potential remedial
measures.
Soil damage (rutting and compaction)
Repeated passes of heavy machinery on the same track may lead to the
development of ruts. Rutting can be particularly severe on soft soils, such
as wet peats or gleys, and is exacerbated with each vehicle pass. The
internationally acceptable maximum tolerable rut depth is 100 mm.
The soil beneath the ruts becomes compacted, with the zone of maximum
compaction extending to a depth equal to approximately half the rut width
(most severe in upper 150 mm but extends to ca. 300 mm depth).
Compaction decreases soil pore space and prevents water and nutrients
from entering the soil. It also reduces the water infiltration capability of the
soil, hence making the rut an excellent channel for surface water flow.
Prevention and remedial measures
• Use existing knowledge base and measurements (e.g. cone penetrometer, shear cane) to assess ground conditions;
• Select the appropriate machines for the site (i.e. Steps 1 to 6, outlined earlier);
• Minimise dynamic effects by ensuring proper load balance and driving techniques;
• Use brash mat if possible;
• Minimise the number of machine passes;
• If an operation must be executed under wet conditions, avoid waterlogged areas;
• Consider reduced but economically viable forwarder payloads.
• Schedule the work appropriately, wintertime (when frozen) or summertime (when dry)
Soil erosion and sedimentation
Input of soil to the watercourses (increased suspended solids and
sedimentation on the stream bed) is potentially one of the most significant
changes in the environment surrounding the forests. Harvesting can
increase soil input to watercourses by a variety of processes, including:
•
surface run off from landings, skid trails and compacted areas;
•
slope failure caused by the removal of vegetation;
•
increased surface runoff;
•
physical damage to the stream banks, such as slippage and bank
collapse, and;
•
impedance of natural water flow when watercourse crossing
structures are not provided, are damaged, or poorly maintained.
Prevention and remedial measures
•
Select the appropriate machines for the site (i.e. Steps 1 to 6, outlined earlier);
•
Use brash mat if possible;
•
Access roads should be surfaced with weather resistant material such as gravel, and maintained in good condition
during harvesting operations;
•
Smaller ditch drains emanating from the forest should not discharge directly into streams or watercourses, but should be
routed through areas of natural vegetation such as forest edge areas, scrub land or filter media such as straw or brash;
•
Temporary stream crossings should be provided, either built with logs on site or comprising portable equipment;
•
Erosion control and soil stabilisation structures such as terraces should be developed as necessary alongside the
access routes;
•
Regular road inspection to identify and repair damaged areas after harvest operations.
Residual stand damage (stems and roots)
Traffic induced stand damage is important in thinning operations. The
process of soil compaction impedes root proliferation, particularly in the
maximum compaction zone (viz. down to ca. 300 mm). Rutting may make
the surrounding residual trees prone to windthrow (falling over in heavy
winds). Exposed roots are subject to direct scuffing action by the wheels
(or tracks), and this may increase the potential for fungal infections. The
extent of such scuffing damage depends on the degree of rutting and the
severity of the machine’s action e.g. the use of band and full metal tracks
exacerbates the effect. On soft soil, rut depths can extend 500 mm on
poorly maintained main extraction routes, hence root damage may not be
confined to surface roots and can have a substantial impact on the trees.
Example of severe (Class 5) root damage
Prevention and remedial measures
• Select the appropriate machines for the site (i.e. Steps 1 to 6, outlined earlier);
• Use brash mat if possible, and employ only trained operators;
• Limit the movement of tracked machines around residual trees in partial cutting;
• Use appropriate band tracks for the inherent ground conditions.
Surface disturbance
Forestry machines rely on soil shear resistance at the wheels/track and
the soil interface to generate the required drawbar pull. The magnitude of
the drawbar pull depends on several factors such as soil condition, vehicle
weight, tyre (or track) type, load resistance and is invariably accompanied
by a degree of wheel/track slip. Damage due to slip includes:
• scuffing of the soil surface;
• mixing (and dislodgment) of the upper soil layer (top 50 – 100 mm);
• root damage and, in extreme cases, a breakdown in the structure of
the top layer of soil (puddling);
• surface disturbance which may also lead to significant erosion
problems in dry climates.
Example of severe surface disturbance caused
by excessive wheel slip (wet soil)
Prevention and remedial measures
• Select the appropriate machines for the site (i.e. Steps 1 to 6, outlined previously);
• Use brash mat if possible;
• Access roads should be surfaced and maintained with weather resistant material such as gravel;
• Schedule harvesting operations to coincide with best soil conditions.
Water pollution and waste management
Most minor oil or chemical spills can be dealt with by means of a pollution
control kit. This comprises a small (< 10 m long) portable floating boom
(white in photo) that can be placed across a stream to stop the surface
flow of the pollutant slick. Floating absorbent pads (light blue in photo) are
placed on the upstream side of the boom to absorb the slick. Such kits are
available commercially and are contained in a small sack suitable for
carriage on the machine. It is recommended practice that all forestry
machines carry such a pollution control kit. In contrast, major pollution
incidents require a concerted action that may involve local authorities
such as emergency services, environment agencies, etc.
Prevention and remedial measures
•
Harvest managers and machine operators must comply with rules for transportation, storage, handling and disposal of
hazardous substances;
•
Product data sheets and spillage control procedures should be in place where chemicals are in use;
•
Temporary fuel and chemical storage facilities should be located away (approximately 100 m) from watercourses;
•
Machines should carry spillage control kits to contain small oil and chemical leaks, while there should be guidelines for
handling of major spillage incidences;
•
Waste oil and empty oil containers, grease cartridges, paper towels, broken cables and hydraulic hoses should be
temporarily retained on site in disposal bins for disposal later.
In all of the above, bearing in mind the Health and Safety regulations, it is of the utmost importance that;
1. Proper planning is carried out resulting in a documented harvest plan, available on site. This involves consultation with
relevant bodies, both statutory and local, choice of machine and method, timing of operation and adequate monitoring of
on-site activities.
2. Only competent operators are used. This implies trained, skilled, possibly certified operators that have the experience
and knowledge to handle operations on sensitive sites, bearing in mind the constraints that these impose.
3.
Responsibility lies with clearly defined personnel to ensure an adequate quality of work.