Rose Bay Property Damage Fears Over Planned Mid-Rise

A State Significant housing proposal in Rose Bay has locals and councillors in arms over the apparent danger to nearby properties.

The $86 million project slated for 21-31 Dover Road intends to replace five existing homes with one eight storey block of flats. A two-level underground carpark is also planned. This would require builders to burrow six metres underground, through the harbourside suburb’s uniquely shallow water table.

Dewatering — the removal of underground water on site — will need to be undertaken before construction can take place above. However, a geotechnical report commissioned by residents indicates that it could do damage to 40 close-by properties, increasing to 130 when other developments nearby are also considered.

Dewatering, excavation to exceed council advice

The report, commissioned by a number of Wilberforce Avenue residents and produced by Fortify Geotech, raises concern about the risks of de-watering to surrounding houses, and about the scale of excavation.

It refers to a previous council-commissioned report, which recommended that the drawdown of groundwater levels be limited to 0.3 metres outside of the site’s boundaries. Despite this advice, the reduction is expected to measure between 0.3 metres and 1.3 metres on up to forty properties on several streets. This potentially extends even to some buildings on New South Head Road, including Hotel Rose Bay.

“The GHD report commissioned by Woollahra Municipal Council states that such drawdown can cause settlement and damage to properties,” the document warns. It says that there are “numerous examples” of construction dewatering causing damage to neighbouring properties in Rose Bay and Double Bay.

“There is also the well known case of Mascot Towers,” it continues. Those residential flats suffered extensive structural damage due to adjacent dewatering, and had to be evacuated.

In addition, the scale of excavation — totalling about 15,000 square metres — is six times the limit recommended by the council.

Latest report full of red flags, says councillor

Julian Parmegiani is a Liberal councillor representing the Vaucluse ward, which includes the development site. He told the City Hub that the Fortify report has “more red flags than a May Day parade.”

“Building an eight storey block on wet sand will be a challenge, if not impossible,” he added.

“The question on everybody’s lips is, who will pay for the damage if construction goes ahead? Homes in the Rose Bay Low and Mid-Rise (LMR) precinct might become uninsurable and possibly unsellable.”

Residents First Woollahra councillor Merrill Witt concurred. “Woollahra Council has been flooded with LMR development applications for Rose Bay and Double Bay. Ten are currently on exhibition.”

Witt noted that determinations are pending on two State Significant development applications in Rose Bay, with the outcome up to planning minister Paul Scully. “Because both are utilising the Affordable Housing Bonus, a public hearing will not be held.”

Developers are frequently exploiting the Affordable Housing Bonus, she said. The bonus enables 30 per cent greater height for Low and Mid-Rise developments, if 15 per cent of the floor area is designated as affordable for 15 years.

“This means that if these DAs and SSDAs are approved, Rose Bay will be effectively saddled with high density developments” in medium density residential zones, she continued.

The council wants Rose Bay and Double Bay exempted from the Low- and Mid-Rise housing reforms, citing the high water table beneath the suburbs.

Residents “cannot believe” they must protect homes, says group

The Rose Bay Residents Action Group said that the “vulnerability of this complex hydrogeological platform has been widely known by Woollahra Council, and documented in expert reports dating back as far as 1999.”

“It appears,” they opined, “that developments have been approved outside the excavation controls in Double Bay for years, leaving damage behind. Then developers have used precedents as a means of getting the next dangerous DA through, and Council, the panel or the Land and Environment Court have approved it.”

“Residents cannot believe they have been placed in a position where they are fighting to protect the structural integrity of their homes.”