"The top 1200-1500mm of soil on the site has been of concern, and while the site held up well in the significant rainfall earlier in the week, some localised works has caused an area of the site to weaken and slip," Mr Tuck said.
He said crew worked on site throughout the night, and the head of the compaany's geotechnical team was satisfied that by starting dewatering immediately and dropping the current water table by around 1 metre (which was achieved by 3am this morning) the slip should be stable enough to be removed by this afternoon.
The slip happened during part of preparations for dewatering the site, which would then allow the removal of a layer of waterlogged soil and green matter, he said.
As part of the site investigation prior to commencing works, the company's consultants and contractors drilled and profiled over 100 spots across the site, recording bore logs and cataloguing thousands of metres of soil samples.
This had given its geotechnical team a very clear profile of what material they could expect to encounter on site at various depths.
Mr Tuck could not estimate how much mud had slipped but depending on whether rain forecast for lunchtime arrived, he expected the road to reopen by 3pm today.
The company planned to remove the top layer of material over the coming weeks and get through to the preferred working platform of tightly packed river gravels beneath, he said.
