Development near National Grid assets has to be managed carefully so it does not create unacceptable safety risks, block Transpower’s access for vital maintenance and upgrade work (including emergency repairs), or otherwise restrict the efficient and safe operation of the Grid.
The Auckland Unitary Plan is Auckland’s planning rulebook. It contains rules for land use, subdivision and development near Transpower’s lines and substations.
Land use and development
Land use and development (e.g. earthworks, buildings, structures) may need resource consent from the Council before they can occur in the “National Grid Yard”. The National Grid Yard is shown in the Auckland Unitary Plan. In most cases The National Grid Yard is the area 12m either side of the centreline of National Grid lines and 12m around the edge of National Grid towers and poles (see image below). The National Grid Yard reduces to 10m either side of the centre for lines on single poles.
New houses and external alterations to existing houses require non-complying resource consent if they are within the National Grid Yard. The plan rules permit and restrict other specific activities and development, depending on their compatibility with high voltage transmission infrastructure. New, or extensions to existing sensitive development (houses, creches, schools, etc) always require non-complying consent to locate in the Yard. The rules are generally less restrictive for development in existing built up, “compromised” urban areas of Auckland compared to mostly undeveloped, “greenfield” or “uncompromised” areas. These areas are all mapped in the Council’s GIS viewer.
Auckland Council makes the decision on all applications for resource consent, but may choose to consult with Transpower as an affected party.
Subdivision is managed within the National Grid Subdivision Corridor. This Corridor has varying widths in Auckland depending on the maximum “blowout”, or swing, of the conductors (“wires”) on each individual line span (the distance between the support towers or poles). The National Grid Subdivision Corridor in Auckland is mapped on the Council’s GIS viewer. You can enter an address and search for that property in the viewer. You can also turn on the Infrastructure - National Grid Overlay to see if the property is within the National Grid Yard or National Grid Subdivision Corridor.
Many activities, including residential building, can occur within the National Grid Subdivision Corridor provided they are set back from the 12 metre National Grid Yard. Transpower has input into subdivision proposals within the National Grid Subdivision Corridor to ensure access is preserved for maintenance and upgrade work, and to manage reverse sensitivity impacts (e.g. the risk of noise and other complaints from people who build houses close to Grid lines).
Photographs of common corridor management challenges
This house was built under the lines in Auckland before the corridor rules came into effect. Now, this house would need to obtain non-complying resource consent as it is located within 12m of the HEP-ROS A centreline. Non complying resource consent is the most difficult type of resource consent to obtain and the council would identify Transpower as an affected party (i.e. we could lodge a submission on the developer's application).
This photo shows the mitigation measures that had to be put in place to ensure the house could be built safely. This type of development is undesirable from Transpower’s perspective because there are on-going risks to occupants (e.g. getting on the roof to retrieve a frisbee).
If not carried out carefully, earthworks can create instability and erosion that threatens a structure’s stability and can result in also clearance violations (not maintaining safe separation between people and live lines). Photos taken from Auckland and Whitby.
Industrial and commercial development can block access and create reverse sensitivity/nuisance effects (restrict business activities). In many areas of Auckland, new commercial and industrial development needs to obtain a non-complying resource consent to be established within 12m of Grid centrelines. In other areas, these developments are permitted mid-span (the middle point between two support towers), although the code that controls safe separation between activities and transmission lines – NZECP:34 must still be complied with, which certainly isn't the case in the last photo!). Talk to Transpower’s Environment Policy and Planning Group if you would like more info on where commercial and industrial development is and isn't restricted in Auckland.
Container load and unload facility in Auckland which experienced a major electrical flashover when a container was inadvertently lifted into a live 220 kV line. This caused a widespread power outage that affected the upper North Island including the refinery at Marsden Point.
HEN-HEP 3 crane incident, December 2017
There are significant risks with mobile plant working under and near transmission lines. Despite NZECP:34 requiring a minimum approach distance, (separation between people/machines and live lines), the responsibility of maintaining these safe separation distances comes down to operator awareness and safety procedures on the site, such as use of “spotters” to warn mobile plant operators that safe separation has been lost. Transpower works with our Service Delivery Managers, Land Owner Liaison Officers and others to review construction management plans that detail how the risks of mobile plant are to be managed. We are also working with other teams at Transpower, including Health & Safety, to increase industry knowledge and awareness.
Subdivisions, where larger properties are broken up into smaller blocks, can result in our established access being physically blocked. These photos show towers “locked in” behind fences after a subdivision in Timaru was approved without adequate consultation and consideration of Transpower’s access requirements.
Links to useful documents