Road repair process and slips Road repair process and slips
The road repair process
Auckland Transport is working hard to repair the damage caused by the recent extreme weather events in Tāmaki Makaurau Auckland. Locations that have the highest risk or safety needs are prioritised for attention.
On this page
- Road repairs mahi (work) explained
- Why does it take so long to repair roads?
- What are the steps / works involved?
- What are the reasons for a road being open or closed?
- My road is not on the list, why?
- How much will it cost to fix my road?
- How long is it going to take to repair my road?
- Do you monitor the stability of the road and how often?
- Glossary of slips and repair terminology
Road repairs mahi (work) explained
You may have noticed different repair work around roads near you and wondered what they’re for. We’d like to give you a bit of a run down and explain a bit of the mahi (work) we’re doing
Bunding
- A barrier, dam or mound used to help channel water from the rain, away from the slip face to improve drainage and soil strength
- These are only temporary fixes and will be removed when the permanent work is started.
Example of bunding on the road surface on Kellys Road, which will channel rainwater on the road past the slip.
Polythene
- Plastic sheeting over the slip to stop more rain from soaking into the slip or eroding the surface. It's secured tightly so that water running over the ground won’t get under the sheet.
- We need to prevent as much rainwater as possible from soaking into the soil
- It also helps prevent further slips in that area.
- In some areas, we can only cover parts of the slip (due to our team’s safety in being able to place it) and in other area’s simply not safe or possible to cover the slip.
Example of Polythene over slip face, combined with bunding treatment.
Frequently asked questions
Most of the damage to the roads has been caused by the earth under the road being washed out by large volumes of water either above or underground. 90% of slips are caused by saturation and underground water There are several steps that need to be followed to repair the damaged roads.
Each road will need a unique plan for the repair which may include:
- Allowing the soil to dry – whilst the soil is still saturated it is difficult to assess the depth of the damage, and there is the risk of further movement.
- Geotechnical assessment & investigation– engineers will drill into the soil to discover the depth of the damage, followed up with offsite assessment and report. Depending on the severity of the slip it may take weeks to months depending on the testing required or whether the site simply needs to be monitored.
- Planning and design – a plan to rebuild the road is designed. In many cases, this will include rebuilding the earth under the road and constructing retaining walls. These designs then go through safety assessments.
- Procurement and delivery – the resources needed for the rebuild must be ordered and prepared. A contractor is engaged for the physical works, and traffic management plans need to be approved before the work onsite can begin.
- Funding needs to be sourced which can be a lengthy process.
General steps for the repair process
- Budget approval
- Design approval
- Consents approval
- Procurement approval
- TMP (Traffic Management Plan) approval
A road is open if it's been assessed by our team as safe to drive on. Roads are closed if there is a risk to safety.
If your road is not on the list, it’s because it’s now open with no restrictions and is safe for all to drive on.
The list only mentions sites that are high risk to the public, if significant traffic management is in place or there is a large impact to roads and traffic. Other roads have been identified by our teams and we’re working on ensuring they’re safe and prioritised for further assessment.
Costs are dependent on the assessment and severity of the damage.
This will depend on the assessment, severity of the damage and availability of resources. This includes road crews and equipment that have already been scheduled for BAU road maintenance and redeployment of crews to help in Northland, Hawkes Bay & Te Tairāwhiti. Roads will also be prioritised based on the highest risk or safety needs.
Yes we will keep an eye on all slips and monitor the stability of the road on a regular basis especially after heavy rain. How often depends on the location, if it’s on a busy section of road, may impact accessibility for a community or has weight or speed restrictions in place.
Glossary of slips and repair terminology (thanks to Waka Kotahi)
Types of slips
Overslips/landslides
Soil and soft rocks near coastal areas, don’t need much rain to cause a slip, or more commonly known as a landslide.
An overslip is when vegetation, soil or other debris slips down onto the road from a bank or hill.
Overslip in Muriwai
Landslide on private land, Titirangi
Overslip, Wood Bay Road, Titirangi
Underslips/dropouts
Underslips occur on the downhill side of the road. They don’t always directly affect the road’s surface but pose a risk if unaddressed. When a section of the road’s surface and foundation has dropped away either from an underslip or other erosion, we call this a dropout.
These issues usually occur in hill country with weak geology, or in areas near the coast or rivers. They often happen suddenly during a storm event, though there are some known sites that we continue to monitor.
Underslip, Karekare
Subsidence
When the surface of the ground sinks it’s called subsidence. Sometimes we can’t see that subsidence is happening until it has already created a hazard on the road. Causes include too much water in the ground and weak underlying soil and rock. Subsidence is a major problem in this region.
Subsidence - Scenic Drive, Waiatarua between Forest Hill Road & Elevation Restaurant (*Elevation site)
Flooding
Flooding occurs when water cannot drain away and spills onto the road. Heavy rain, blocked drains, steep banks, and limited vegetation can contribute to the effects of flooding.
Storm flooding - Kellys Road, Oratia
Treatments to improve resilience
Soil stabilisation
A method used to treat subsidence sites is called Colmix. This involves using a specialised drill rig to mix a small amount of lime and cement into the soil to create a solid column, which improves the strength of the soil. Steel shafts can also sometimes be used to achieve the same goal.
Drainage improvements
Soft rock and soil like we have on the Western beaches and Waitākere Ranges can absorb a large amount of water and become unstable. By reducing the amount of water reaching the ground and removing water from under the surface, we can improve soil strength so that both overslips and subsidence become less likely.
Candia Road, Swanson – before storm damage
Candia Road, Swanson – after repairs to drainage & culvert
Retaining walls
Where a reasonable foundation under the soil exists, a retaining wall can be used to reform an area of road. Retaining walls can be made from various materials: commonly iron or wooden posts and wooden boards, mass blocks of concrete or rocks, or baskets with rock fill inside.
Retreats
Sometimes the best thing to do is relocate the road away from the issue. This could include moving the road onto more stable ground or away from a river.
Rock protection
Rock protection (known as a rock revetment) is a rock barrier to protect against erosion. Where erosion is occurring, a revetment can remedy the situation by placing fill at the site and then building a thick layer of large rocks to absorb the wave or river energy.
Rock protection on Waiti Bridge, Bethells Beach
Site monitoring
There are several site monitoring techniques that can be used such as camera and drone surveillance to monitor slopes.
Rockfall fence
Low rock fall fences are effective for holding back small quantities of rock and are easy to maintain.
Groynes
A groyne is a physical barrier that intercepts sediment that would otherwise erode a particular area. It is used to ‘river train’ and deflect flowing water away from high erosion-risk zones.
Gabion walls
A gabion wall is a cage or box filled with rocks, concrete or sand and soil used for erosion control. They can be used between the river and the road to prevent underslips.
SLIPS - what you need to know
We’ve put together some general information about slips.
- In the first instance, we encourage you to get in touch with your insurance provider as soon as possible.
- AT is responsible for managing the Auckland Transport System which includes public roads.
- From time-to-time storm events cause minor and major damage to public roads and private property across the wider Auckland region.
- When this happens, AT undertakes a process of assessing the extent of damage to public roads and then prioritizing repair work as fast as possible.
- In the case of private land damaged from recent storm events, AT is not responsible for repairing that damage.
On this page
- Location clarification of slips
- Steps if you've been affected by a slip
- Complexity around large slips and the time it takes to fix them
- Earthquake Commission (EQC) responsibility
Location clarification of slips
Slips on a public road or footpath
If a slip has caused a blockage on a public road or public footpath, call our Customer Care team on 09 355 3553 or contact us online.
Footpath slip in Titirangi Village
Slips on private land
- The owner of private land is responsible for repairing damage to their own land including repairing any slips on their land due to storm events. That work may require the landowner to stabilise their own land to prevent further slips on it.
- Vehicle crossing repair (where the driveway leaves the legal boundary of a property and continues until it meets the road. It allows vehicles to cross over berms or footpaths to access the road) and reinstatement is the responsibility of private landowners. Private landowners are directed to clause 29(7) and (8) of the AT Activities in the Road Corridor Bylaw 2022.
- If a private landowner has constructed an accessway to their property on an unformed road (either with or without the approval of AT) AT is not responsible for maintaining or repairing that accessway. It is an offence under the Local Government Act 1974 to do work on the road without AT’s approval.
- In the case of private land or property damaged in recent storm events, the owner of that land or property should contact their insurance provider to discuss the damage.
- A private landowner may be able to make a claim with EQC for slips on their land. A private landowner should contact EQC to find out if they qualify for cover.
- If a private landowner is unsure where their property boundary exists, they should get in touch with Auckland Council through their website or over the phone on 09 301 0101.
Slip on private land in Titirangi
Slips affecting both public and private land
- Where a slip affects both private property and public roads, this may require discussions between the private landowner and AT as to repairs.
- Any private assets (such as garages, fences and other structures) located on the road require AT’s approval for that encroachment. Those assets (including their repair) are the responsibility of the private landowner.
- Repairing damage to a driveway is the responsibility of the private landowner.
- Repairing damage to a vehicle crossing is the responsibility of the private landowner. See AT Activities in the Road Corridor Bylaw 2022.
- In the first instance, private landowners should ask their insurance providers what is covered by their insurance.
- To determine your boundary, get in touch online with Auckland Council or over the phone 09 301 0101.
Steps if you've been affected by a slip
- Is it an emergency?
- If it’s causing an immediate safety risk call 111.
- If you can smell gas call 111.
- If the ground on the public road or footpath looks unstable and has a risk of moving or a slip is about to happen, call our Customer Care team on 09 355 3553.
- If you have no power, call your electricity provider.
- If a dangerous hazard is posed by the electricity network (such as damaged poles or downed/clashing power lines) contact Vector or Counties Energy
- If your water pipe is broken- turn off the mains and contact Watercare 09 442 222.
- Staying safe in a slip
- Stay away from the slip area. This is dangerous and should be avoided.
- Follow signs and stay behind safety barriers.
- Please do not attempt to travel through closed sections of the road. This can cause further damage and risk to your safety and the safety of others.
- Sightseeing is discouraged especially in Resident-only access areas. This puts already vulnerable roads under stress and causes safety risks. Access is only for those who live in these areas.
- Have a plan and be ready to leave quickly if you need to, especially in areas prone to slips.
- Do not attempt to voluntarily clear fallen trees or debris, excavate slips or roads in these areas. It is unsafe. Please leave it to emergency response crews and contractors as they have safety assessment procedures in place. Whilst it can look safe, there can be stability issues in the ground beneath.
- In some places, it’s unsafe to open the road to even one lane of traffic, due to the nature of the damage, and the unknown stability of the remaining road surface.
- If you think it will be a safety risk, call 111.
Complexity around large slips and the time it takes to fix them
- Slips can’t always be fixed quickly, especially when they’re in remote areas with limited access.
- We need to investigate and assess sites that require technical expertise, which can take time.
- This information helps us to come up with a plan on what’s the best way to repair the damage.
- We need to contact those affected in neighborhoods and communities, including landowners, residents and the general public, take feedback on board and keep everyone updated.
- We can then assess if the road can be fixed quickly or temporarily and re-opened when safe albeit with restrictions until the permanent repairs start.
Steps to repair large slip include:
- Initial Geotech assessment – this is done when the slip first occurs if we’re concerned about the immediate stability of the slip. We do this to assess the best way of clearing the slip.
- The slip is cleared, the area is made safe, and we monitor the slip to see if there is any additional movement – this may require more geotechnical assessments to confirm.
- After a while, when the slip face settles and things dry out a bit, we will undertake a review of the slip face. This is when we start to understand a few things like the potential cause of the slip, high level remediation options and start to think about how we progress the remediation.
- If we decide that some remediation work is required (eg a retaining wall), we then need to factor how this will fit into our existing programme of work and budgets.
- When we know the priority of the job, we can then programme it in and undertake the design process.
- The design then goes out to tender so we can get contractors on board and only then will any serious construction work begin.
- Depending on the size, complexity and priority of the individual situation, this process could be as quick as a few months up to a few years to complete.
Earthquake Commission (EQC) responsibility
- The Earthquake Commission (EQC) is a New Zealand Crown entity that provides insurance to residential property and invests in natural disaster research and education.
- If your home is insured, you may be covered by EQC for a natural landslip. For more information go to EQC on its website or call on 0800 DAMAGE (0800 326 243)