Due to the steep gradient and the length, the tunnel poses some difficult challenges in maintenance.
The build up of coal dust from over the years, has come to the point where the passenger service has been halted through the tunnel. Instead, passengers are taken by busses to the other end of the tunnel, while the train makes the decent/ascent, with just the Kiwi Rail staff on board.
Work is underway to wash the tunnel with high pressure jets, to remove the coal dust from the interior walls
This water flows down through the ballast to a holding area and is then pumped into geotextile bags.
Submersible pumps were needed to do this job, as well as some other units for providing water at the top for the jets.