Main cable anchor failure injures zipline employees
Employees of a Vancouver Island zipline company were working on a summer day amongst the trees when a main cable anchor failed on the launch side of the zipline. The failure caused a complete release of the cable, causing the employee riding the line to fall several meters to the ground. Another employee who was holding the zipline cable at the loading area was also thrown off the platform onto the ground.
Ziplines are installed using a variety of methods to anchor the main riding cable. Examples include trees, rock anchors, steel towers and concrete foundations. In this case, the zipline used an eyebolt connected to a rod embedded in concrete.
Technical Safety BC's investigation found high probability that the primary cause of failure was the installed orientation of the eyebolt, which produced a significant bending load at the thread which exceeded material strength. It was possible that the actual load on the eyebolt had been underestimated which reduced the margin of safety.
After our investigation, the owner of the zipline started work on repairing the zipline. We issued an alteration permit for the repair work and conducted an alteration acceptance inspection before the zipline reopened to the public.
There are currently 71 active ziplines in BC operated by 13 different contractors. The size of the operations range from those with one to 12 ziplines, and line lengths ranging from 50 metres to over 2,300 metres; the highest lines are more than 200 metres above the ground. Ziplines installed in BC must go through an installation permit and design review process. The installation permit application and the documentation relating to the design must be stamped by a BC Professional Engineer to confirm it meets all Act, Regulation and Code requirements.
The incident report summary provides further details of this incident.