Ausgrid owns and maintains a small substation, known as a kiosk, in Rosser St, Rozelle, which supplies about 150 local homes and businesses. The substation is on land situated on top of a significant heritage wall. Next to the substation, and also on top of the wall, a small-leaf fig tree has self-seeded and grown into a very large tree.
While the tree contributes to neighbourhood amenity, it has grown so large that the invasiveness of its root system has made the wall and the kiosk substation unsafe. The roots are making the wall increasing unstable and are affecting the base of the substation and conduits carrying live electricity cables. The branches are also impacting the drainage of the school buildings next door.
Independent arborist reports have found that any trimming of the root system will make the tree increasingly unsafe, posing significant risks to the community. If a fault occurs at the kiosk substation, the only way crews can safely restore power is to trim the root system to allow safe access to the substation equipment and cables. This would destabilise the tree and leave it at risk of falling over.
We began speaking with the community about this project in 2013, and have since carried out further investigations into ways to preserve the tree while safely resolving these risks. We have been discussing this issue with local residents and stakeholders to try to find a solution that keeps everyone safe.
Outcome of consultation
As part of our further investigations into these safety and reliability issues, Ausgrid has examined a range of alternative solutions for the site. We have also carefully considered feedback from the community and stakeholders, and reviewed the expert advice from independent, heritage and engineering reports.
Our detailed response to submissions following the May 2016 community information session is available here.
The coexistence of the fig tree, the substation and the heritage wall remains an unacceptable safety risk to the community and to our crews. Our review has found that removing the tree is the only feasible solution to these safety risks and all the other factors that need to be addressed.
We understand the loss of this tree may cause concern for the local community. However a suitable and adequate alternative, which ensures the safety of the community and our staff, as well as a safe and reliable power supply, is unfortunately not available.
After notifying the community Ausgrid safely removed the the tree on Tuesday, 27 September 2016 and has begun planning work for repairs to the wall. Because this work is likely to require an interruption to the power supply to the nearby school, it is expected that remediation work will occur in the December/ January school holidays.
We will notify the local community before any work begins.
Moving the kiosk substation into Rosser Street.
Assessment: While moving the kiosk off the wall and into the footpath or roadway, it is unfortunately impractical, due to space restrictions. A kiosk on Rosser Street would present traffic hazards and safety issues in the narrow street.
Moving the kiosk substation to an alternative position on the school grounds
Assessment: Ausgrid does not have an easement on the school grounds. The school is understandably not willing to provide land for the substation.
Replacing the kiosk substation with pole top substations in Rosser Street
Assessment: Augmenting the underground network to be connected to overhead infrastructure would impact the reliability of the high voltage underground cable that supplies the substation and about 2,200 local homes and businesses. This means the likelihood of power interruptions too all of these properties would be increased and there would be less flexibility for switching the network around to quickly restore the supply. Physically, it requires substations to be installed on top of two poles in Rosser Street, which would be very close to homes and may present noise issues for the residents, due to the narrowness of the street. Sections of high voltage overhead powerlines and the infrastructure to connect it to the underground cable would also need to be installed, increasing the visual impact of the network running down Rosser Street.
Moving the kiosk substation to Punch Park
Assessment: The park is unfortunately too far away from the area the substation supplies, making it unviable from a technical perspective.
Raise the kiosk substation
Assessment: Any option to move the substation, including raising it above ground, is likely to cause root damage to the tree, leaving it at risk of falling over. A raised substation in this location would also not meet the electrical Network or Australian Standards for this type of infrastructure.