Auckland Transport followed “do minimum” advice to save $300,000 – that decision may have cost ratepayers $3.85 million.
The council organisation received the recommendation in a report from an engineering company regarding cracks found in a North Shore carpark.
Two years later, those cracks became landslides.
On October 9 and November 28, 2017 two massive landslides swallowed the back end of Birkenhead’s Rawene car park, threatening nearby buildings and destroying infrastructure.
A Geotechnical Assessment Report was completed by engineering company GHD group in 2015, to assess the cracks and stability of the car park and surrounding area.
NOTE: Click here to See original article for A snip from the October 2015 GHD report, which recommends Auckland Transport monitor the to-be Birkenhead slip site, labelled as the “do minimum” option.
Auckland Transport were given three options: A “do minimum” option of monitoring the area, a reinforced soil structure, and a retaining wall.
The report recommended monitoring and maintenance because of the relatively high cost, which Auckland Transport followed.
“The ‘Do minimum’ option is considered most feasible and appropriate at this stage,” the report dated October 2015 said.
Even though it was the highest risk of future failure, the immediate cost at $20,000 was substantially less than $500,000 each for the other two options.
But on February 27 this year, Auckland Council found itself forced to approve an amount of $3.85 million for the Rawene Slip.
Of that, $2 million will cover the emergency works already completed, and $1.85 million for the design and permanent stabilisation works and the construction will be in addition to this.
A joint statement from Auckland Council and Auckland Transport defend the actions taken by staff.
“The remedial option recommended in 2015 by GHD was monitoring, which would not have prevented the slip occurring,” a spokesperson said.
“The options described may have provided some extra stability to the slope but given the scale of the Birkenhead slip it is quite possible that they would not have prevented it occurring.
“It was considered unlikely that the GHD proposed monitoring gave any enhanced level of warning, over and above visual monitoring, to realistically allow time to install physical mitigation measures other than fencing the area off to ensure the safety of the public.
Kaipātiki Local Board deputy chairwoman Danielle Grant said the information from the report was not shared with the local board.
“The report was several years ago. The stress that this [slip] has caused our Birkenhead community, it is extremely concerning that AT hadn’t shared that information earlier,” she said.
“They didn’t act on it. It wasn’t really until the significant cracks were appearing, that it was brought to the attention of the local board.”
Current geotech lead Ross Roberts said that Auckland Transport did broadly follow the recommendations of the 2015 report and to say otherwise is inaccurate.
“It [the report] didn’t recommend building a retaining wall. The recommended option was monitor the site,” Roberts said.
Article by Laine Moger
Published 03 March 2018 > North Shore Times -stuff.co.nz