Report warned of landslips
A CONSULTANT’S report to the Gold Coast City Council warned of historical landslides – and the risk of further slips – well before owners were forced to abandon multimillion-dollar homes in the Hinterland.
A Bulletin investigation in May detailed how owners in a luxury estate at Riverstone Crossing, Maudsland, were forced out of their four-yearold homes because in-ground swimming pools were sliding down hills and wooden decks were on dangerous tilts.
In state parliament, Theodore MP Mark Boothman tabled a report by Mortons Urban Solutions to planning assessors at the city council.
The report was commissioned for Stockland Developments Pty Ltd, the developer of the estate in 2012. It was to ensure the housing project could be certified as sustainable and have a “low to very low” slope instability hazard for a design life of 70 years.
The report shows a walkover survey conducted by the consultant found most of the site had no major evidence of slope instability.
But it noted “there are several areas where there is evidence of existing or recent past slope instability involving movements of typically soil in the form of landslips”.
At least 25 lots were highlighted in the report for being unstable and required more work – typically better above and below ground drainage. A landslip appeared to have occurred in a gully.
“This landslip is approximately 50m wide and appears to involve the movement of typically soil,” the report said.
In its response to the Bulletin, Stockland said drainage and necessary earth works were undertaken, and proper certification attained.
Mr Boothman told parliament: “Groundwater seeping out of a slope on a hill should raise red flags. The geotechnical report labelled the area in question hummocky ground … another cause for concern.”
He said lots 585, 586 and 622 of the estate had been assessed as having a slope instability “Hazard Risk Rating of Very High” and were located within a slip area with groundwater seepage evident.
“The report makes recommendations that residents feel were never sufficiently carried out. We should not be allowing residential estates to be built on hummocky ground, land with active slips and areas of groundwater seepage.
“These affected residents are asking for the laws to be changed to reduce the likelihood of this ever happening again,” he said, adding that a petition had been started to ensure proper reforms.
Residents have also raised concerns about drainage after obtaining photographs of early planning of the estate.
The Bulletin asked the council whether it ensured the correct civil works at the estate.
A spokesman responded: “The City is aware of the situation at Riverstone Crossing. In accordance with its responsibilities under the Building Act 1975, the City issued notices to the owners of the affected properties to vacate premises due to safety concerns.”
A Stockland spokesman said: “The purpose of the referenced geotechnical report was to describe the probable engineering solutions required to deliver the relevant stage of the development of the Riverstone Crossing site.
“This report was drafted prior to breaking earth. While the site’s topography is complex, it is not unusual for southeast Queensland.
“The drainage infrastructure delivered on-site, along with the necessary earthworks, was undertaken under the direction and supervision of external experts and contractors and properly certified as part of the approval process.”