We all know what the drop zone is, right? The BPG defines the drop zone as the “area where the tree sections of the tree will land during felling or pruning operations”.
The drop zone is not to be confused with the hazard zone.
The hazard zone can be as large as the whole work site, as is often the case in arboricultural operations. We can also establish a safe zone for workers to rest, or no-access zones for workers’ safety.
All these zones can be identified in your hazard assessment of the work site.
There are three paragraphs referring to the drop zone in the BPG:
49.11 Before tree dismantling begins, a drop zone and a hazard zone shall be identified and workers made aware of both of these zones (the hazard zone shall include the drop zone).
49.12 Clear communication shall be maintained between the Arborist in the tree and the ground crew within the hazard zone before cutting and lowering branches.
49.13 No worker shall enter the drop zone until having received an ‘all clear’ from the climber.
When I developed my Safe Operations Procedures (SOPs) a while back, one thing I was missing in the above was a rule of thumb for the drop zone size. So I went afield to search what other industries use. It didn’t take me long to find a rule in the Forestry ACOP.
The paragraph below describes how a forestry worker shall operate within the safety zone.
The safety zone in forestry operations has a similar function to the arboricultural drop zone.
11.4 Safety zones – two tree length rule
11.4.1 All fallers and harvester operators shall ensure that, within two tree lengths of the tree being felled, there are no:mobile plant without appropriate protective structures
- working ropes – exception: cable yarder assisted felling or ropes that have been lowered to the ground and are not operating
- live powerlines – exception: where a felling plan has been authorised and agreed (for further information refer to section 2.14) other operations.
11.4.2 Mobile plant with the appropriate protective structures may work closer than two tree lengths but not closer than one tree length of felling operations unless they are directly assisting in the tree felling operation.
11.4.3 No person shall be closer than two tree lengths to a tree being felled, unless that person is:
- the faller
- assisting the faller
- training others or being trained
- observing or auditing.
Any person within two tree lengths of a tree being felled shall be under the direct control of the faller. Exception:
The faller is under the direct control of a trainer.
11.4.4 Aside from the tree faller no person shall operate a chainsaw within two tree lengths of a tree being felled. Buddy cutting is not permitted.
11.4.5 No tree shall be felled within two tree lengths of any road, railway or public access until the provisions of section 2.12: Signage and temporary traffic control have been complied with.
I used the template from above and some German guidelines that I had been taught to develop our own drop zone rule of thumb.
Pro Climb’s SOP for operating in the drop zone.
The drop zone is an area twice the radius of the section lengths being cut from the tree with a minimum radius of 5m. If a whole tree is being felled, the drop zone is twice the radius of the tree height. The centre of the circle is measured from the location of the cut.
In some cases the drop zone may need to be extended or can be reduced in one direction to allow for specific terrain anomalies, for example, a tree removal conducted on a slope will need a larger drop zone downhill than uphill.
Using rigging and cranes can also significantly change the shape and size of the drop zone.
Always consider the worst case scenario and adjust the drop zone accordingly. Any adjustments to the normal drop zone needs to be recorded on the hazard ID form.
If there are any structures or targets in the drop zone, arboricultural rigging techniques are to be used to prevent any damage to these. Buildings are to be evacuated if located within the drop zone. The climber, faller or EWP operator shall ensure that, within the drop zone, there is no:
- mobile plant without appropriate protective structures
- work equipment – exception: rigging tools and felling tools used for the tree operation at hand.
EWPs with the appropriate protective structures may work in the drop zone if they are directly assisting with the tree operation.
No person shall be in the drop zone unless that person is:
- rigging for the climber or EWP operator
- assisting the rigger, climber, faller or EWP operator
- training the rigger, climber, faller or EWP operator.
Any person within the drop zone shall be under the direct control of the faller, climber or EWP operator. An exception would be if the faller, climber or EWP operator is under the direct control of a trainer.
Aside from the faller, climber or EWP operator, no person shall operate a chainsaw within the drop zone of a tree removal.
Exceptions can be made if the worksite requires others to use a chainsaw in the drop zone as long as a clear work plan and communication channels are established.
A supervisor needs to be identified and take control of the work co-ordination.
If the drop zone overlaps with any power lines, the provisions of section 19 of the BPG need to be followed.
If the drop zone overlaps with any roads, railways or public access the provisions of section 21 of the BPG need to be followed.
As always, the thoughts above are only a starting point for a bigger discussion.
Struck-bys are still one of the most common accidents in the tree care industry. We believe a clear understanding of the drop zone and its purpose in the arboricultural work site will reduce such incidents.