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Rot inside impregnated poles increasingly detected, especially when installed directly into ground or concrete

An inspector identified a significant number of rotten poles whilst inspecting ropes courses in the Netherlands. The problem was identified on treated poles which were buried in the ground. Rot was identified in the core of the pressure treated poles just beneath ground level (see sample Pict. 1 resp. sample Pict. 2) and also on different points up to 2 metres above the ground.

The problem can only be identified when inspecting very carefully to the core and usually only with the use of approriate tools (e.g. drilling, hammer + drift punch, ...). Inspection is more difficult for treated poles (those treated under pressure). Such poles often appear sound from the outside even though the core can be rotten. This is what was discovered in the Netherlands.

LARGE PoleExteriorWithDriftpunch       LARGE PoleRotNearGroundline       LARGE-PoleRotFewMetersAboveGroundline
Sample Pict. 1: Pole appear sound
from the outside, but the drift punch
shows an enourmos insertion depth
after breaking the harder shell.
Sample Pict. 2: There was rot found
in the core of the pole after removing 
parts of the harder shell of the pole.
Sample Pict. 3: Sometimes rot
of the core can be found also
a few meters above the
groundline.


The problem was identified for poles...

  • ... which were buried (into the ground) and
  • ... which were pressure treated

In the case referred to above, the rot was found on poles that had been installed upright; however, experience suggests poles installed horizontally (Balance-Beam, Giant Ladder etc) are more likely to rot from the inside (see sample Pict. 4) as it is harder for water penetretrating shakes (cracks running parallel to the grain) to escape. Similarly, where there is not a good flow of air (e.g. concealed behind plates) rot is likely to be accelerated.

Immediate steps:

  • The issue was discussed between the Dutch inspector, the sector representative for inspection, members of the safety commission and the executive Board. The most important findings from these consultations are included in this safety warning.
  • A member of the safety commission has personally contacted all Dutch Ropes Courses that have received inspection certificates within the last 5 years to make sure they are aware of the problem.
  • This warning urges all RC inspectors and operators to double check if there ropes course might be affected. Although the issue was found in the Netherlands, it is likely not isolated to this region and probably also present in other countries.

Recommended steps for RC inspectors and operators:

The well known phenomenon of internal rot (in pressure treated poles) can be attributed to a number of factors. In any case great care must be taken when inspecting timber poles of all descriptions. 

Source: http://www.erca.cc/index.php/en/publications/safety-alerts/228