Ōrākei Main Sewer repair and relining
Work to rehabilitate the damaged section of the sewer and the sinkhole on St Georges Bay Road.
Duration
2023 onwards
Location
St Georges Bay Road, Parnell
Status
Construction
Background
On the afternoon of Monday 25 September 2023, we were alerted to a sinkhole hole that had formed in a carpark off St Georges Bay Rd, above the 2.1m-diameter brick Ōrākei Main Sewer. This wastewater transmission main serves large parts of central and west Auckland. The sinkhole was associated with the wastewater pipe collapse blocking the sewer. A temporary pump station and bypass was installed to stop wastewater overflows into the environment and to allow debris to be cleared. This work has now been completed and the repair started in March 2024.
Sinkhole and sewer repair
The repair involves pipe-jacking a series of liners into the damaged sewer to restore full strength and flow capacity. Installation of the liner is now complete and a grout/cement product is being put in place between the old pipe and the liner to secure it into position. After grouting we will commence the reinstatement of the sinkhole area in the carpark. Further information will be provided as more detail comes to hand. Please note, pedestrian access across Alberon Reserve has been reopened. Please follow the signage on-site.
Once the repair is completed, the temporary pumps in St Georges Bay Road and the bypass pipeline will be removed. This is expected to occur around August 2024.
Stage 2 relining
Over the past few months, we have been undertaking a condition assessment of the remaining 9km of the Ōrākei Main Sewer to help mitigate the risk of future failure. The condition assessment has identified the need to rehabilitate further sections of the ageing pipeline.
The next section, stage 2 works, will involve access via a deep shaft in the northern section of Alberon Reserve and relining of the sewer between manholes 14 and 15 (refer map below) with glass reinforced plastic liner. This technology will enable the Ōrākei Main Sewer to continue in service for another 100 years.
Subject to approvals, site preparation for stage 2 is anticipated to begin in early August with site preparation. A deep shaft will be constructed to enable access to the Ōrākei Main Sewer for relining, as well as construction support area including a site office and storage area being set up in Alberon Reserve. It is anticipated that stage 2 Work should be completed by February/March 2025. A laydown area to support the construction works will also be within the reserve.
During this time, Alberon Reserve walkways will remain open however there will be sections of the Reserve which will fenced off for health and safety. While parts of the reserve will be fenced off, access between Alberon Street and St Georges Bay Road will remain as well as the pathway between Alberon Place and Havana Coffee. The southern section of the reserve will remain open for normal recreational use. Further details of the layout are shown on map 1 below.
Future relining
The deep shaft will remain open after the completion of stage 2, as it will be a key access point for stage 3 relining works between manholes 14 and 13 which will commence towards the end of 2025. As this is a live environment conveying wastewater and stormwater in a combined sewer, we are unable to work safely over the winter months when there is increased rain, increasing the volume of fluid in the sewer.
Stages 4 and 5 of relining are being planned for future years.
