The walkway at Dolomite Point on the West Coast at Punakaiki. Photo: Greymouth Star / Brendon McMahon
Mice have been at play at the West Coast's premier visitor site, the Pancake Rocks at Punakaiki.
A section of the track to the blowholes was closed due to a crack caused by a mouse burrowing in the sensitive limestone landform.
Department of Conservation Western South Island director Mark Davies told the West Coast Conservation Board meeting a shaft had emerged past the main viewing area on the Dolomite Point Track.
The entire site was regularly checked given the geological factors, with natural weathering by the sea which form the natural blow holes through the limestone karst headland.
"We've got about eight sites that we monitor on the Dolomite Point Track, sites that have got some geological risk ... We've got a trigger action response plan."
Davies said that response was triggered in early March when a small "tomo" (hole in the limestone formation) was found. A small section of track past the main viewing platform was closed as a result.
The small cavity discovered at the edge of the Dolomite Point Track walkway. An ecologist told the Department of Conservation they believed the hole was likely to be due to the collapse of a mouse burrow subsequently discovered below the surface. Photo: Supplied / DOC
Staff discovered that during some track work dating back to the 1920s a hole had been filled with rubble, which had recently come loose.
DOC Buller operations manager Suvi Van Smit said a ranger also noted a small hole about 150mm wide at the edge of the walkway.
"As it was on the northern abutment of the rock arch a section of the track was closed so a geotechnical assessment could be done to ensure it didn't indicate subsidence or instability in the rock mass."
When a 2-metre-long endoscope video camera was inserted to inspect the cavity, it came up with a surprise.
"While this was being done a live mouse was spotted approximately 700mm into a horizontal offshoot from the hole.
"No soil subsidence or instability underneath the walkway was seen with the camera. An ecologist who reviewed the video said the cavity was consistent with a mouse burrow and the hole was likely to be due to the collapse of the burrow."
A view of the surge pool with undercut geology over which the Dolomite Point Track at Punakaiki passes. Photo: Greymouth Star / Brendon McMahon
Van Smit said another three cavities spotted nearby were also likely due to mouse burrowing.
"Geotechnical advice was that the opening of the original cavity should be backfilled, and the track surface sealed with an asphalt patch.
The walkway is open again.
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