$24m The hole
Ratepayers face big bill after early warning system rejected
Auckland Transport rejected advice by engineers to set up an “early warning system” to monitor unstable land long before two massive slips in Birkenhead that could cost $24 million to put right.
The revelation has shocked local residents, businesses and Northcote MP Jonathan Coleman, who said AT had the information about unstable land at Rawene Rd carpark, did not act on it and have let down the community.
Auckland Council’s chief operating officer, Dean Kimpton, has defended the actions of AT staff, saying that while they did not follow the recommendations of engineers, they carried out regular visual inspections of the carpark and acted when large cracks appeared.
The warning bells were sounded in 2015, two years before the first slip swept away 25 carpark spaces in October last year, followed by a second, larger landslide in November that sent a drilling machine tumbling into the Rawene Reserve and workers scattering.
Papers obtained by the Weekend Herald under the Official Information Act show a geotechnical assessment by GHD engineers in 2015 found signs of pavement cracking and kerb stones separating.
Boreholes revealed poorly compacted fill to build up the carpark was capable of moving under its own mass, particularly if saturated.
GHD recommended two options to fix the unstable land at the carpark for $500,000 or $550,000, and a “do minimum” option of geotechnical monitoring. The latest council estimates put the cost of fixing the slips between $14m and $24m.
GHD said the option of monitoring the site monthly was the most feasible and appropriate and would act as an “early warning system” to respond to any undue movement efficiently and cost-effectively.
In a statement attached to the OIA response, AT chief engineer Andrew Scoggins said the carpark was monitored for cracks on a “nominal monthly basis . . . however the site visits were not documented, which is normal process for an area that is not showing change”.
The monitoring did not include ground monitoring pins and sealing existing cracks as recommended by GHD because it was deemed unlikely to give any enhanced level of warning beyond visual monitoring, said a joint statement from AT and council.
It was not until two years later on September 14, 2017, when big cracks appeared in the carpark that AT brought back a geotechnical specialist to check the ground and its stability.
Coleman said: “Auckland Transport needs to explain why they didn’t act on this independent advice . . . something major has happened which could have been averted.”
Birkenhead Brewing Company cofounder Brad Boult said “somewhere along the line their systems have failed dramatically”. Highbury optometrist Tony Chadwick said: “You do have to wonder why [at] a body funded by the people for the people there is so much . . . secrecy.”
Claire Balfour, the body corporate chairwoman at the nearby Mokoia Ridge Apartments, said the latest revelations showed a bureaucratic aversion to do anything. Another resident, Graham Tucker, said AT had put his family and others at risk by not acting on the GHD report.
“I’m shocked they didn’t do anything. It’s starting to make me very angry,” Tucker said.
Kaipatiki Local Board chairwoman Danielle Grant said the slips had impacted on the community and caused huge distress, both financially and emotionally. The GHD report should have been shared with the Local Board to have the opportunity to consider the options, she said.
No one from AT would be interviewed about the GHD report, on the basis Auckland Council is now managing the issue, overseen by Kimpton.
Kimpton said AT staff decided not to do geotechnical testing on the carpark but to visually monitor the site, which was successful because when they noticed additional movement they got engineers back and protected public safety.
He said AT made the right call based on experience and the evidence at hand.
“When they did spot the cracks they got Opus [engineers] in,” he said.
Kimpton said even if an inclinometer — a geotechnical instrument for monitoring movement below ground — had been used at the carpark as advised by GHS, it would not have bought enough time to act because the slip happened quickly.
The AT-council statement said the options to fix the unstable land may have provided some extra stability but given the scale of the slip it is quite possible that they would not have prevented it occurring.
It said most of Auckland has soils that swell in winter and shrink in summer. Building controls take this into account and council created a team of geotechnical specialists last year to respond to issues and recommend solutions where public land may be affected, including coastal erosion.
Asked by the Weekend Herald several times how much it would cost to fix the slips, Kimpton said he had “no idea” or “nothing that can be relied upon” beyond a minimum of $1.8m for temporary repairs so far.
A report to this week’s finance and performance committee said urgent repair works have cost $2m, design and other work is expected to cost $1.85m and preliminary costs for a permanent fix are $10m to $20m.
It is also costing $80,000 a month to pump stormwater and wastewater out of the landslide, which continues to move slowly and remains a significant risk, the report said.
The GHD costs of $500,000 and $550,000 for a permanent fix did not include detailed design, site supervision, land purchases, GST and a suggested 30 per cent contingency.
Meanwhile, a $9m stormwater project to strengthen unstable land at Chelsea Heritage Estate below the slip means the project cannot be built as planned for safety reasons and “may have to be cancelled or subject to significant cost and programme overruns”, said the report.