Auckland Council and Auckland Transport discuss Rawene Rd slip
Still from a drone showing the extent of the damage at Birkenhead’s Rawene Car Park. A slip has taken the back section of the car park into the gully below

Top AT and Council staff maintain local development had nothing to do with the massive Rawene car park slip last week.

Here is a selected transcript from the Kaipatiki Local Board (LB) meeting on Wednesday night.

They were questioning AT Senior Communications Advisor Nahri Salim, Auckland Council’s Geotechnical & Geological Practice Lead Ross Roberts, Head of Infrastructure Programmes, Haydn Read; and AT Snr. Investigation and Design Engineer Duncan Miller.

How can experts maintain that the pile driving conducted by the adjacent construction worker did not contribute to the slip?

Lindsay Waugh (LB): So was there no consideration, to your knowledge, of the vibrations from the pile driving travelling along the fill to cause the slip? It would seem to be a sensible assumption?

Roberts: No, vibration from soil drilling are insignificant. My experience of other sites, is that the sort of vibrations that you get from that are insignificant. What you get from trucks going along the road create more vibrations.

John Gillon (LB): I’ve heard from a lot of people that every time the piles were driven they could feel those vibrations all around the area, so I find it very curious that there are less vibrations from that than a truck going past.

Roberts: It is difficult to prove, what triggered the slip, almost impossible. This is following a period of very heavy rain.

Gillon (LB): We are looking to confirm that there will be a review to consider all the circumstances that resulted in the car park slip. Who will be doing that review and will it include looking at whether the vibrations had anything to do with the slip, or anything else?

Miller: Whoever does the review, they will be professional services who will be independent and funded jointly by AT and Auckland Council.

What will the review cover?

Anne-Elise Smithson (LB): What are the technical aspects of this review and can you clarify if the review will consider that vibrations contributed to the slip?

Roberts: A scope hasn’t been written for the review yet. When it comes to actually looking at what caused the slip, we can ask consultants to assess whether vibrations had any impact. I would give it it my 99 per cent confidence they it will come back with a “probably not, but we can’t prove it”.

Smithson (LB): But surely it’s not too much to ask to have that included?

Robert: We will ask that question. I don’t think we will get a good answer out of it.

Salim: The point we want to make, the investigation will not preclude any reason. In the same vein, we will not try and encourage the consultants to focus on any one reason over another than the other. This will be a fair review.

Was preventing the slip possible?

Adrian Tyler (LB): I wonder if this carpark had a higher profile some engineering work might have happened rather than just fences going around it. Could you not have done some engineering work to protect the asset?

Ross: To have put in engineering works would have taken number of months. The slip was very deep. There were no signs early enough for the slip to have been prevented.

John Gillon (LB): But AT have been monitoring the site for 12 months?

Roberts: There have been a lot of small cracks but there are lots of car parks with small cracks in them. The cracks weren’t big enough to trigger a detailed engineering response. When it came to the point where it was that serious to trigger that response – it was too late.

Salim: There was no indication that a slip was imminent.

Will Chelsea Heritage Park be affected?

Lindsay Waugh (LB): Has there been any investigation of the slip into the stormwater works in Chelsea Heritage Park?

Roberts: I’ve been down there myself – there is no immediate impact. The real problem we are considering is that there will be a load of silt coming down. There is also the risk of the landslide causing a dam. So we are monitoring that carefully.

Waugh (LB): On a worst-case scenario could it take out the bank above the lower lake/cooling pond? It’s all precarious land so is there a risk of a knock-on effect?

Roberts: It is highly unlikely, any flooding from a dam establishing and breaching would result in overland flow and it would just spread out and be a bit of a mess on the surface.

Can AT reverse the lease of the carparks?

Richard Hills (Ward councillor): The board was never supportive of the leasing of the car parks. However, we were told they were necessary for safety reasons. Now, we can see there are port-a-coms and everything on those car parks, which means the parks are not being used for the original purpose. If it was a private property next door, you wouldn’t be able to do that. I think that would be the best way to get a positive outcome in the short term to release these car parks back to Birkenhead shoppers.

Salim: Auckland Transport is looking into this.

Are there health and safety concerns for the surrounding buildings?

Danielle Grant (LB): I would like a sense of assurance for the surrounding staff of Mokoia Rd shops, Mokoia Ridge Apartments, and the other building sites on Rawene Rd .

Roberts: It looks pretty convincingly like the fill does not extend further than it has. The risk to those shops is completely unchanged. However, we are investigating this to give residents more confidence and more assurance