More slippage is expected in the Auckland suburb of Birkenhead, while the land settles down after a second massive landslide, but residents to not need to worry, geotech expert says.
Birkenhead’s second landslide, which swallowed a piece of stabilising machinery, tore a lot closer to the back of the Mokoia Rd shops on November 28.
This followed a first slip, which took out half the carpark on Rawene Rd in early October.
Auckland Council officers answered questions from concerned residents and business owners at a meeting organised by the Kaipātiki Local Board on December 7.
Auckland Council’s geotech lead Ross Roberts said he was “expecting more subsidence”.
However, Roberts said there was no danger to the buildings in the area because the slip so far has been only legacy landfill.
“The fill is moving away but the natural ground is staying where it is,” he said.
“The Mokoia Ridge apartments are on natural ground, built on the ridge before the fill was in place. For that reason we are not worried about the buildings.”
Recently, there have also been concerns about a second crack that has appeared in the Mokoia Rd car park across the road from the original slips.
Roberts said there was no reason to be concerned about this new crack.
The crack is consistent with damage from vehicle loading and is not related to the fill, he said.
“It is inconsistent geologically with the slip. There is no danger.”
Currently, geotechnical testing was ongoing around the site, to identify the cause and the remedy for the incident.
The first priority was making sure stormwater didn’t get into the slip. The second was trying to stabilise the area.
In the long-term, Roberts said a full fix will be some variant of building a wall into the ground.
Resident Ruth Jackson asked for reassurance the natural soil hadn’t been eroded.
Roberts said it was very, very unlikely.
“In general, fill is erodible, the clay is not erodible but we are doing investigations.”
Brian Cox said he was more than frustrated that Auckland Council was not being open to the public.
“The mere fact that you have a machine in the gully, you have no idea what’s going on,” Cox said.
Article by Laine Moger
Published 08 December 2017 > The North Shore Times – stuff.co.nz