Construction company linked to Wānaka flood damage fronts

Authorities are investigating why dirty water from a retention pond at a Wānaka development site flooded several properties early on Monday morning, as the company potentially responsible for the damage fronts up.

The ground floor of a home on Aubrey Road was covered in 100 millimetres of silt-laden water by 9am, while the deluge affected five properties all up.

The top of Wineberry Lane also suffered some minor damage.

Lou Harper surveys the damage as floodwaters recede at her home on Wānaka's Aubrey Road, Monday, July 1, 2024.

Both the Queenstown Lakes District Council and the Otago Regional Council are now investigating the incident, although both are tight-lipped on details.

However, Crux understands water flowed from a worksite connected to the Pembroke Heights subdivision into the top of Wineberry Lane and then followed a path downhill to Mount Roy Terrace and eventually a property on Aubrey Road.

John MacKay, the managing director of Benchmark Construction, the key company on the development site, has confirmed to Crux the surge of water was due to an unexpected breach of one of the ponds designed to catch water run off during construction phases.

Mr MacKay says while the pond was "designed and constructed accordingly" water appears to have travelled through its walls, running through earth alongside a pipe.

"We can't say categorically what's caused it," he says.

"At the moment, all of us are saying we can see what has happened, but we don't know why it has happened."

Mr MacKay says the company is fully cooperating with authorities in their investigations and has visited impacted property owners.

"It happened - we're not hiding."

While MetService had weather advisories in place for the area on Sunday, Mr MacKay says he has received various reports on exactly how much rain fell overnight, some of them conflicting.

"We're honestly not sure if it was an unusually large rainfall."

A senior manager for the company, who is Wānaka-based, headed to the site in the middle of Sunday night to check how systems were coping as forecasted rain persisted.

Water breaches what should be a retention pond at worksite connected to the Pembroke Heights subdivision on Monday, July 1, 2024 (Image: Supplied).

Mr MacKay says the manager pumped some water away from the pond in a controlled discharge.

The Otago Regional Council's acting manager compliance Chris McSweeney says members of his team responded to the incident on Monday, and were back at the scene on Tuesday investigating the matter.

"ORC staff became aware of the issue while conducting proactive monitoring of the site," he says.

"As the matter is subject to a current investigation, no further comment will be made at this time."

On Monday, a spokesperson for the Queenstown Lakes District Council confirmed the flooding appeared to be "related to a failure of erosion and sediment controls on private property after heavy rain", although they did not name the owner involved.

The Aubrey Road home of Lou Harper and Helen Henson on Monday morning, July 1, 2024.

The council's monitoring and enforcement team is also investigating the incident.

Wānaka councillor and deputy mayor Quentin Smith says he has been asking questions of the council on behalf of residents.

He says at this stage this appears to be the latest in a string of stormwater management failures on large subdivisions in Wānaka, and that is disappointing.

Meanwhile, the owners of the most flood-damaged property are still reeling from Monday's events.

Lou Harper and Helen Hanson used homemade sand bags in an attempt to keep floodwater out - but to little effect.

The dirty water inundated their home covering skirting boards, soaking carpets and couches, damaging furniture, and entering kitchen cupboards.

Firefighting crews were on the scene shortly before 9am and worked to pump water away from private properties on Mount Roy Terrace and Aubrey Road, but little could be done to save the couple's home from damage.

Main image (Supplied): A fast-moving, dirty river of water enters the Aubrey Road property of Lou Harper and Helen Henson, at approximately 8am on Monday, July 1, 2024.