Just-built homes in Whangarei's newest suburb are at risk from slips, fresh geotech evidence shows.
Geotech engineers say
more than a dozen houses on Stage 2 at Kotātā Heights in Morningside may become unstable if the land moves, leading to weaker foundations and damaged land, buildings and infrastructure.
More investigation is under way to determine the risk of deep-seated instability.
To date, no obvious movement is affecting houses at Kotātā Heights, at the southern entrance to the city, and the Whangarei District Council said no concerns have been raised that would stop people from staying in their homes.
However, the council has put a hold on two building consent applications in Stage 2, and four in other stages while it waits for more geotechnical engineering.
The Northern Advocate approached homeowners in the affected sections, but none wanted to talk.
TYhe six-stage Kotātā Heights has elevated views of the harbour and farmland just minutes from the city.
After a land slip at the end of Manuka Pl in Raumanga in August last year, WDC asked engineering consultant Tonkin + Taylor to study the underlying geological formations in the area, as well as on Kotātā Heights.
Manuka Pl resident Tony Stringer and his wife were moved to temporary accommodation after last year's land slip made their house uninhabitable and damaged WDC infrastructure.
The council believes work on land next to Kotātā Heights by former mayor Stan Semenoff resulted in the land slumping and the Stringers having to vacate their home.
The report summarised findings of recent deep borehole investigations, among other tests, on Stage 2 lots which were separated into northern and southern areas.
The northern area consists of lots one to 15 while southern has lots 16 to 34.
Tonkin + Taylor's November 18 report to council general manager infrastructure Simon Weston found Lots one to 10 in the northern area of stage two were not at risk but Lots 14 and 15 were and Lot 11 might be.
In the southern area, Lots 11 to 18, 20 to 22, and 31 to 34 were at risk.
Geotech specialists Initia said stormwater discharge and runoff on the western slopes below the northern and southern areas could increase the risk of slips.
Kotātā Developments and the company's engineers are looking at what work might be needed to mitigate ssues.
Weston said WDC was working with the developer to help them find solutions.
"We have put on hold applications for consents that included information that Tonkin and Taylor's report raised questions around. We, along with the developer, have installed monitoring equipment to measure land movement over the site.
"Our concern is to ensure the development is safe for developers, contractors, home owners and visitors, and also to protect the ratepayers' infrastructure," Weston said.
Tony Davies-Colley, a director of Kotātā Developments, said development of stages three to six were ongoing.
"As with all subdivisions, engineering and geotech work will be completed to council's satisfaction. The geotech consultants work is incomplete at this point," he said.
Although WDC has approved the Kotātā Development subdivision, under the Building Act 2004 is has to refuse a building consent if the land on which houses are to be built is subject to, or likely to be subject to, a natural hazard such as subsidence or slips.
WDC has written to owners of at-risk homes on Stage 2, recommending that they check with their insurer in the interests of full disclosure.