Steffen and Debbie Schubert claim that major drainage and excavation work at the neighbouring retention basin which fronts Richardson Road had the potential to “undermine their rear retaining wall and property fence”.

They are also concerned about a reported blocked drain, an issue which Port Stephens Council has acknowledged.

“A significant blockage has been identified in the outlet pipe on the south side of Richardson Road, and the council has directed the developer to remove the blockage prior to the release of a Subdivision Certificate,” a council spokesperson said.

“Council expects the developer to clear the blockage by late September (possibly sooner).”

The Schuberts, who purchased their retirement home on Halloran Way three years ago, said that they became concerned following excavation works carried out to accommodate a neighbouring housing sub-division.

“Since the work the water level has crept up to within 100mm of our back fence,” Mr Schubert said.

“Fortunately of late we have not had much rain, but we are scared every time it rains. All we ask is for the installation of reinforcements to the outer retaining wall.”

The council spokesperson said that in the unlikely scenario that there are multiple extreme rain events occurring back-to-back, which the network in its current state could not handle, then emergency overland flows from the basin would cross at the intersection of Richardson Road and Halloran Way.