The Barrier Times has reviewed 114 pages of redacted Auckland Transport correspondence detailing the financial disputes and engineering complexities behind road repairs across Aotea following January’s storms.
AT previously told the Barrier Times that major slip repairs would not be completed until June 2027, meaning the island could go through one and a half storm seasons before the damage from January is addressed. At the time, AT said 18 underslip locations required remediation, with five still requiring further investigation and detailed design.
With many of the slips unaddressed, the correspondence shows contractor price negotiations, funding reviews and AT actively exploring whether cheaper construction specifications can be used.
One of the clearest examples is the Blackwell Drift Culvert on Shoal Bay Road, where AT has been negotiating the price of the work with Fulton Hogan.
“Pricing for the Blackwell culvert is still being finalised, with negotiations ongoing with Fulton Hogan,” an internal memorandum says.
The memo says AT is exploring “alternative options” to support a price comparison and, because of the “high cost” of the culvert, is considering relaxing the engineering specification. It specifically asks whether 40 MPa concrete could provide “comparable durability and performance while achieving cost savings”.
The issue was still being worked through months after the storm.
In July, AT said its consultant was revising the drawings to change the specification, including the use of 40 MPa concrete, while refining the precast units to improve construction and transportation.
“Once AT receives the updated drawings, the works will be issued for repricing,” the update says.
The documents do not say AT has run out of money, or that a lack of funding has stopped the entire recovery programme.
They do show cost directly influencing decisions about the work, with AT changing specifications and negotiating prices before proceeding.
Funding was also still being considered on other infrastructure work.
An AT update on the Cowshed Bridge project states: “Funding implications remain under review, and further updates will be provided as the evaluation progresses.”
AT’s July update says 14 underslip locations now require remediation, including four major sites on Puriri Bay Road, Medland Road, Aotea Road and Rosalie Bay Road. Site investigations have been completed and detailed design is progressing.
Beca’s engineering report makes clear that the work is not necessarily about permanently stabilising every slope.
“The proposed solution is an emergency works solution to reinstate low traffic volume route,” the June report says.
The options are based on site walkovers, UAV surveys, LiDAR information and engineering judgement, with Beca stating: “No analysis or site investigations have been undertaken.”
The report describes the work as “Emergency works reinstatement only” and says “no safety improvements” are proposed.
Beca also acknowledges that some risks will remain after the work.
It says cut slopes could be affected by “heavy rain events and general weathering”, while “existing slip scarps are vulnerable to further movement or potentially retreat particularly where the toe of the slope is being eroded by streams or ocean”.
At Shoal Bay Road, a rock buttress is one of the proposed remediation options, but Beca says it would need to be “monitored and likely maintained/topped up, particularly following extreme weather events”.
The engineering report also shows why conventional retaining structures are not a straightforward answer on some of the island’s steep slopes.
At Aotea Road, the failed road-edge retaining wall has left a very high and steep scarp. Beca says a wall reinstating the road edge would need to be about six to seven metres high.
It says gravity retaining solutions, including gabion baskets and reinforced concrete L walls, would require major temporary works and likely close the road during construction. A cantilever wall would require deep piles into rock, specialist equipment and temporary working platforms and would be “prohibitively expensive”.
Instead, Beca recommends retreating the road into the hillside, cutting into the existing slope and using drainage to reduce groundwater.
A similar approach is proposed at Rosalie Bay Road, where the slip has reduced the road to about three metres wide and the scarp is four to five metres high.
Beca says retreating into the hillside by cutting into the slope for up to about 40 metres is considered viable, while conventional gabion baskets and reinforced concrete L walls are not considered suitable because of bearing-capacity limitations, the need for major temporary works and the likelihood of a significant road closure.
At Medland Road, the scale of the problem is much greater than damage to the edge of the road.
Beca describes the slip as approximately 50 metres wide, with cracks and small displacements extending another 25 metres. It is affecting the road and adjoining property, and Beca says previous drainage remediation has not been effective.
The slip is also considered likely to reactivate. Beca says movement is likely to be driven by elevated groundwater and describes the failure as relatively deep, extending a significant distance downslope.
That is why Medland was identified as one of three high-priority sites. The internal assessment describes it as a “large underslip affecting road and downslope property” and says the site is “Complex”. It also warns that the slip could affect programmed work on a large culvert nearby.
Beca recommends retreating the road further into the hillside at Medland and installing major drainage to reduce groundwater. It says timber pole or gabion walls would not be expected to have an acceptable factor of safety against further land movement because of the deep-seated failure.
The cost of these engineering options is reflected in Beca’s estimates, redacted by the Transport authority.
The report warns that transporting materials and equipment to Great Barrier Island would likely increase the costs and recommends more accurate quantity surveying. The estimated cost of the Shoal Bay Road options has been withheld from the released report under the Official Information Act provision relating to prejudice to negotiations.
The correspondence also reveals AT is understaffed for the slip remediation programme.
An April email says a business case was being prepared seeking “additional staff support for the slip remediation work that occurs across the region”.
The exercise was intended to establish the scale of the work and “how it is currently resourced”, including the resources available for investigation, design and construction.
The remediation programme comes as the Aotea / Great Barrier Local Board considers alternative routes for parts of the island’s road network, including the use of existing paper roads, as it looks at the vulnerability of roads to slips and coastal erosion.
It coincides with Beca’s warning that some of the failed areas are vulnerable to further movement, particularly as streams or the ocean continue to erode the land.
AT has previously told the Barrier Times that major slip repairs had completed their investigation phase and were in detailed design, with construction completion targeted for June 2027.
At most sites, the proposed solution is to cut further into the hillside rather than construct expensive retaining structures, while also focussing on continued monitoring and maintenance.
At Shoal Bay Road, the firm says the proposed rock buttress will likely need to be “maintained/topped up” after extreme weather.
