Otira Tunnel Washing

Overview / Gallery

The Otira tunnel is 8.5km long and runs under the Southern Alps between Arthurs Pass and Otira.


The tunnel first opened in 1923 and since then has been a vital link for the west coast. Operating a passenger service for this line, Kiwi Rail keep a close watch on the maintenance and condition of the tunnel to ensure the safety or both the coal trains and passengers that travel the iconic route.

Case Study

The Requirement The Solution The Outcome

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.

The Requirement The Solution The Outcome

Prime Pump offered Grindex Submersible pumps and Varisco open diesel units as a solution for this application.


Varisco diesel drive units provide water supply from a stream for the washing process - Equipped with fish screens to protect the wildlife in the streams.

Down the bottom, we have Grindex Maxi pumps, pumping the coal dust and water mixture into Geotextile bags for drying, and later removal. The ability for these pumps to run dry 24/7 without damage was a key benefit in the decision to go with Grindex.

The Requirement The Solution The Outcome

The remoteness and sometimes extreme temperatures of this application make it challenging when trying to offer a solution that will do the job efficiently and effectively.
However – the pumps have been working consistently and the maintenance on the tunnel is progressing.


Grindex and Varisco are designed specifically for harsh conditions, and many of them have found themselves in much worse applications than this. They are built to take the knocks and harsh treatment that comes along with the job.

Trusted by:


City Care Fonterra Bathhurst Buller City Council Connell CPB HEB Transmission NCTIR Grey District Council McConnell March Waste Management Westland Milk Products Kennards Hire