Temporary fix allows reopening of tunnel

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JOHN.COSGROVE@nullcluthaleader.co.nz

One reopens while the other stays closed.

The Lawrence cycle tunnel has reopened following an innovative remedy, while the McLean Falls remain closed.

The Clutha Gold Cycle Trail Big Hill tunnel reopened after the trust which maintains it cleared away the slip and pre-positioned a large container inside the tunnel to make it safe to enter again.

Using a tractor, workers cleared the debris and then pushed the container into the tunnel, positioning it under the 1m hole that has appeared in the ceiling.

Now plans for a more permanent structure are under consideration.

The trust still advise it is best to have a light when cycling or walking through the tunnel and to take care as contractors were still working from Beaumont to Lawrence in certain small areas.

At the other end of the Clutha District, the McLean Falls remain closed.

The huge slip below the falls which has blocked the popular walking track in the Catlins continues to cause headaches for local businesses and Department of Conservation staff.

Doc senior ranger Brent Affleck said that following the March 14 landslip at the scenic McLean Falls a recent site inspection by a geotechnical engineer assessed the landslide to be 88m long and it had physically increased in size since the initial event.

The report said rocks were continuing to be dislodged and falling to the valley floor.

“The engineers said the likelihood of additional minor rockfalls sourced from within the existing landslip scar has been assessed as ‘high’ and there is a significant risk to the safety of people in the vicinity of the falls,” he said.

The slip inundated the track walking surface with rocks and vegetation, and also destroyed two visitor-related structures including a viewing platform.

Mr Affleck said following the recommendations of the geotechnical report Doc will be contracting industrial abseilers to carry out specialist rock-scaling work on the heavily fractured 12m sandstone bluff.

“Once the rock-scaling has been completed, the total length of the slip will be sluiced with water using a firefighting monsoon bucket underslung from a helicopter.

“The goal is to remove as much loose material as possible from the landslip scar and wash the debris downslope but any heavy rain events also have the potential to trigger a further landslip.

“There is a single large accumulation of debris located at the base of the bluff and this needs to be washed downslope to ensure a safe working environment before the Department’s track construction team can being work reinstating the track to this popular attraction.”

Mr Affleck anticipates that each stage of this process will bring further material down on to the area of the track.

“This rock and vegetation will need to be cleared before the track can be reopened to the public.

“I cannot provide a clear timeframe before the track will be opened again as progress will be determined by what each stage of the process reveals and it could be months [before it] is reopened to visitor access,” he said.

Local businessman Paul Bridson said he went in with Mr Affleck and immediately noticed that more debris had covered the track.

He said the major portion of the new debris was from the trunk and base of a large dead Rata tree that had fallen down.

Mr Bridson said the consulting geologist found that the tree had broken loose from the crumbling rock formation and slid down and over the track, taking out a viewing platform for the lower falls while also covering the lower portion of the track and steps leading up to the final section.

“There was also another Rata tree angling out from the same rock formation that was considered a stabilisation hazard and would have to be removed.”

He also saw that several feral goats were dislodging rocks on the slip face.

Mr Bridson said the preliminary prognosis was that it would not be a quick fix and the site would need substantial work to make the track safe again, clear the debris and repair the track.