Woronora property owner ordered to re-engineer design of new house after retaining wall section collapses

Collapsed section of retaining wall on the steep building site at Woronora. Picture: woronora.com

Collapsed section of retaining wall on the steep building site at Woronora. Picture: woronora.com

A Woronora property owner was ordered to re-design a new house being built on the steep site after part of a retaining wall collapsed.

The failure of the wall, which occurred in late September after prolonged heavy rain, resulted in tonnes of steel and concrete crashing down the Prices Circuit site, the website woronoravalley.com reported.

The collapsed section was estimated to be about 20 per cent of the wall.

"Two huge girders toppled with three panels of loose slabs," the website said.

"They were scattered like giant dominoes, as the shallow soil supporting them was washed away, including part of a neighbour's yard."

A spokeswoman for Sutherland Shire Council said officers visited the site the day the council was informed of the collapse.

"A geotechnical engineer and structural engineer were also required to attend," she said.

"The owner was required to re-engineer the design to ensure the site was safe.

"A council officer returned several times to the site to monitor the progress of remedial works.

"The repairs are now complete."

Don Page, of woronoravalley.com, contacted the three councillors who represent the area, saying it was "a dangerous example of excavation and building".

"Council, as consent authority, should probably investigate how such a large structure went so badly wrong, and may fail again catastrophically with someone buried beneath it."

The website report said truckloads of clay and rock had been removed from the site over a year by heavy equipment.

"Massive excavations of clay and rock began about three years ago, gouging a deep hole in the hillside and left unsupported for some time," the website said.