A82 forest operations - work types
Throughout the course of the A82 project the work we need to do falls into five categories which impact to varying degrees on the A82. These are;
This will involve our existing skilled and competent teams using our normal harvesting systems and machinery to fell trees. On less steep slopes, harvester teams (who cut the trees) and forwarder teams (who move them to forest roadside for pick up) will use “wheeled” machines. On steeper slopes a skyline winch and chainsaw teams will do the work. They will also use tracked harvesters, which can operate on steeper ground.
This will involve felling trees using winch systems and machinery that is not readily available in the UK. The steepness of the slope and the large size of the trees means that areas where we need to do this are classed as extreme – trees as heavy as 10 tonnes (at Loch Ness side) will need to be hauled 600m up slope to the nearest forest road. This work can only be done by highly skilled operators using specialist ‘skyline’ equipment like Duffy Skylining
Thirty or forty years ago many people working in hill forests were familiar with skyline or “cable way” systems but the amount of skyline harvesting carried out in Scotland has declined and fewer people have direct experience of operating skylines. Forestry skyline systems in the UK generally use a stationary winch and series of wire cables and pulleys to move fully or partially suspended trees or logs to the roadside for processing and stacking.
During the early years of the last century there was little or no cableway extraction in Britain although tractor mounted winches did some timber extraction on ground that was too difficult for horse extraction; where tractors were used the winches "skidded" the trees over the rough ground. Some experimental cableway work was done in the 1950s but it wasn’t economic and horses and tractors prevailed until cableway systems got better and more effecient. They were increasingly in use through the 60s and 70s until greatly improved skidding tractors and forwarders capable of tackling easier hill terrain became available; from this point on the use of cableways began to diminish.
Cableway extraction diminished even more during the 1980s when a difficult timber market forced most forest managers to focus on low-cost tractor logging - and thinning ceased in many hill forests. A brief revival for cableway systems in the 90s was short-lived thanks to a significant fall in timber prices that made much cableway logging uneconomical.
Cableway work requires special skills, a good understanding of the system and an ability to assess and deal with the requirements of each individual situation. Training is essential for efficient and safe cableway work. It also requires skilled chainsaw operators who can fell large trees in difficult conditions, however, because of widespread mechanised harvesting, they too are in short supply.
There are two main types of skyline system – the low level, which raises the front of the load just enough to allow it free passage over obstacles, and the fully or partially suspended skyline systems, which uses a locking carriage to hold the load firmly in place and carry it over obstacles entirely.
Fell to Recycle (FTR)
This involves felling young trees that are then chipped or simply left in the forest. This work will be carried out mainly by chainsaw, although machines may be used on less steep ground. The aim is to fell areas of conifers whilst they are still relatively small and fairly easy to deal with.
Before we can do any harvesting, a lot of civil engineering work is required. The forest road network needs to be upgraded and improved and our civil engineering teams will improve entrances into the forest, replace bridges, upgrade forest roads and build harvesting facilities such as tracks and stacking bays.
This involves assessing the condition of the hill face and designing, installing and working on measures to secure slope stability and the safe removal of rock in support of timber harvesting on the steep ground. Appropriate measures include rock catch fences, netting, bolts (to secure the rock face), anchors and geosynthetics (sheets of plastic mesh - grids and cell - to help strengthen the hill face or drain soils). This has been a main feature of the operations at Glen Righ and these types of operations will also be required elsewhere in the Great Glen.
During the weekend of 9-12 December 2011 a section of the A82 north of the Corran Ferry was closed to allow the safe removal of a potentially dangerous 250 tonne rock - map showing location (PDF 1MB) - that geotechnical engineers had advised us was unstable and that needed to be removed in a controlled way as soon as possible.