Rebuilding the other infrastructure
Rebuilding retaining walls
We appreciate that many people's homes, and their access to them, are affected by the state of the retaining walls.We're working closely, alongside Christchurch City Council and the Historic Places Trust, to plan for safe, effective, and affordable repairs which respect the heritage values. It may be several years before funds will become available to place the wall facings.
The general approach for rebuilding the walls is to make sure the walls are better able to withstand any future earthquake activity. We've already worked hard to repair or make safe many walls while we plan and prioritise the permanent rebuilding.
In general, we will rebuild walls as structurally-designed, reinforced concrete walls. Our rebuild work provides for future decorative wall facings. Once rebuilt, the walls will be better able to withstand any future earthquake activity.
Each retaining wall is unique. The design solution for walls may differ, depending on the level of damage, ground conditions and access. Additional investigations will be needed in some areas to inform the design solution.
Rebuilding Lyttelton's retaining walls is challenging due to:
- steep topography
- their age – most of the walls were not designed to modern standards
- insurance coverage for the walls is minimal.
SCIRT has been directed to rebuild retaining walls which are on or support publicly owned land. Rebuilding retaining walls on private land is the responsibility landowners, who should contact EQC or their insurer.
We expect to begin work to permanently rebuild retaining walls in Lyttelton early in 2012. Each wall will have unique requirements and rebuilding times will vary. It may take several years before all the walls are rebuilt. We are reviewing rebuild priorities with consideration of geotechnical assessments, CERA zoning, and funding approval. We'll perform rebuilding work according to a well defined prioritisation process, considering factors like:
- how many people are affected and how much they are affected
- heritage and cultural values
- dependencies with other nearby infrastructure (for example, wall repairs on Selwyn, Ross and Shackleton Streets in Lyttelton has been prioritised because water and waste systems are affected)
- maintaining services and facilities like emergency access, schools, transport
- availability of funding
- any constraints on site access.
Where possible, we will always advise the local community when work will begin at individual sites.
SCIRT has released additional information for the community about retaining walls and progress:
- SCIRT in Lyttelton – what's the story with retaining walls? (article, March 16, 2012)
- Lyttelton retaining walls - community update (notice, March 2012)
- Anchors on dry land above Lyttelton (article explaining ground anchors, April 27, 2012)
- Lyttelton's Sumner Road retaining wall will resume once easements finalised (article, May 28, 2012)
- Your questions about Lyttelton retaining walls answered (distributed in Lyttelton, March 2012)
- Lyttelton Community Meeting, Monday March 12, 2012 (video of public meeting)
- Drilling ground anchors into Sumner Road retaining walls, Lyttelton (video, April 2012)
The Avon River's banks primarily protect against tides rather than river flooding from heavy rain. Emergency stopbanks were temporarily erected to avert serious overflowing in the king tide of July 2011. There is further work to be done compacting the current stopbanks. We also expect to move most of our temporary emergency stopbanks to stabler and higher ground after we've done further assessments and when the eventual land uses of the residential red zone are decided.
To reduce the risk of flooding from weakened stopbanks, 30 damaged storm water outfalls have been repaired.