A new $3.4m hut on the Milford Track has replaced the 30-year-old Mintaro Hut which is closing due to earthquake risk.

The 40-bunk hut is the second hut trampers encounter on the track, just before McKinnon Pass.

DOC’s Southern South Island operations director Aaron Fleming said the new hut is about 2km from the existing hut and walkers would begin using it in the final weeks of this year’s Great Walk season with an official opening planned for next season.

Fleming said the old hut was being replaced as it was in a potential rockfall zone and there was an estimated 15 to 20 per cent chance of an earthquake triggering a major rockfall in the area in the next 15 years.

The new hut cost nearly double the initial estimate of $1.8m and was delayed by several months. Fleming said that figure was “an early estimate in the indicative business case before going to market or costed” and didn’t include the cost of additional work like track rerouting, a new swing bridge or warden’s quarters.

“This cost reflects the remoteness of the site and the complexity of working in a wilderness environment,” Fleming said.

“However, the end result will be a far superior hut equipped to handle the changeable backcountry conditions and out of the path of predictable rockfall paths.”

He said the new hut received significantly more sun and had double glazing, thermally broken windows and better insulation. It also included 70,000 litres of water storage and a specially engineered septic tank that should only need to be emptied once every two to three years, rather than annually.

“Regular and ongoing maintenance and cleaning cycles will ensure that the hut lasts for more than 50 years without the need for significant upgrades or renovations.”