Alarm sounded before landslip

‘‘Can council step in under emergency provisions to undertake any remedial works before any further damage occurs up slope?’’ Geotechnical engineer Ian Brown to council on October 5, 2020.

‘‘Council is very concerned with how this issue is progressing.’’ Council earthworks engineer John Davies on October 5.

‘‘It is unlikely [the Seven Sisters homes] were designed to withstand the impact loading of a landslide.’’ Brown on December 8.

‘‘Serious concerns at the council’s current approach.’’ Lawyers, on December 9, for owners of 188 and 190 Oriental Pde, where there were unconsented earthworks.

‘‘How can we get the neighbours to work together on this before it becomes a much bigger issue?’’ Brown to council on May 3.

Nearly a year of warnings piled up at the Wellington City Council about ground moving above the city’s millionaires’ strip before a large slip thundered down and severely damaged homes.

Council documents, released after a Local Government Official Information and Meetings Act request, show the frustration as geotechnical engineer Ian Brown – engaged by homeowners above unconsented retaining walls behind two of Oriental Parade’s ‘‘Seven Sisters’’ homes – warned of tension cracks and moving boundary pegs.

‘‘Can council step in under emergency provisions to undertake any remedial works before any further damage occurs up slope,’’ he asked the council 10 months before the slip.

It was July 24 when tonnes of earth, rock, and brick came down behind the homes, each valued at between $3 million and $4m. Some backyards were deemed red zones.

One woman was allowed into her bedrooms but was not permitted to sleep in them. Homes above had gaping holes in gardens, which they were not allowed to set foot in.

It is understood the discussion – involving homeowners and insurers – remains ongoing, with some blaming the unauthorised retaining walls behind 188 and 190 Oriental Pde but others saying heavy rain was to blame.

The two homes with unconsented retaining walls are owned by companies belonging to Wayne and Rosemary Coffey. Owners of affected Oriental Pde homes could not be contacted or chose not to comment, with some citing ongoing legal and insurance issues. The Coffeys could not be contacted and Brown would not comment.

‘‘There has been a lot of claim and counter-claim from some of the property owners as to the cause of the slope movement and who was responsible for any mitigation,’’ council spokesman Richard MacLean said.

‘‘Reports to the council generally conclude that the slip occurred due to significant rainfall and the soils overlying bedrock gave way.’’

MacLean confirmed the council was aware of the instability issues before the slip and had ‘‘performed its regulatory responsibilities’’. This included engaging its own geotechnical experts, issuing an abatement notice for unauthorised earthworks, and issuing a dangerous notice to the owner of 188 and 190 Oriental Pde. The council asked a neighbouring property owner – 192 Oriental Pde – to tell tenants to stay out of the backyard on July 23, the day before the slip. It was getting an engineer to check out the site on the Monday but then the slip happened two days before.

Council documents show a report by geotechnical engineering firm Engeo in December said the new retaining walls were at least partly to blame for the shifting ground and cracks. But a report by the same firm after the slip said heavy rainfall was the most likely cause.

Brown, whose company Ian R Brown Associates was contracted to clients in homes above the slip, warned the council about the shifting earth and ‘‘tension cracks’’ on August 17 – 341 days before the ground gave way.

On October 5, he told the council it appeared the Coffeys had not engaged an engineer to assess the slope, as the council had told them to do, and asked the council to use emergency provisions to fix the issue.

‘‘Council is very concerned with how this issue is progressing,’’ council earthworks engineer John Davies said, adding the council would get its own engineer in.

On December 8 – 228 days out – Brown warned the land was accelerating, the slopes would fail, and homes below were at risk. ‘‘It is unlikely they were designed to withstand the impact loading of a landslide.’’

A day later, lawyers for the Coffeys expressed ‘‘serious concerns’’ about the council’s approach and asked that it extend its investigation to look at neighbouring properties.

On May 3, 2021 – 82 days out – Brown again wrote to the council pointing out one survey peg had moved 29 centimetres in two years.

‘‘There has been significant slope deformation in the past weeks,’’ he said.

‘‘We expect that will increase as we move towards winter with increased rainfall. How can we get the neighbours to work together on this before it becomes a much bigger issue?’’

One day before the landslide, he emailed council about more earth movement and cracks, and warned that 192 Oriental Pde – the property that bore the brunt of the slip – was now at risk.