Powerlines' effect on South Australian street trees a growing issue with housing infill: cost to underground $40-60b
The issue of powerlines effect on South Australian street trees in urban areas intensified with the loss of tree canopy due to housing infill.
About 80% of South Australia’s electricity supply lines network, with a total length of 88,000 kilometres – was above ground in 2023.
The underground powerlines were in Adelaide city centre, some suburban main roads and for all new housing subdivisions (at the developer’s cost). The issue of powerlines effect on street trees in urban areas intensified with the loss of tree canopy due to housing infill. Electricity supplier SA Power Networks, an oversea-owned private monopoly in South Australia, was criticised for its role in felling trees to make way for electricity infrastructure.
The company said it supported more greening of urban areas. It argued that the controversial trimming of trees near powerlines could be reduced if more approriate street tree species were used. It was working with Healthy Living, Green Adelaide, and the University of South Australia on trialling more suitable tree species.
Since the Ash Wednesday bushfire in the late 1980s, state laws required that trees be cut back by specific amounts from powerlines to ensure safety and reliable power supply. One important change to those laws allowed a risk-based approach to trimming trees around low voltage powerlines near homes in the metropolitan area and larger regional towns). This allowed trees to grow through stand-alone 230 volt residential powerlines (those not also having 11,000 volt lines above). This allowed for more balanced pruning.
ABC (insulated and bundled) cables were used extensively through the Adelaide Hills but had several shortcomings. ABC cables for high-voltage powerlines were no longer manufactured and low-voltage ABC cable was less capable of managing increased the energy flows from continued growth of rooftop solar, electric vehicles and greater electrification of households.
SA Power Networks estimated the cost of undergrounding the electricity network would be between $40 billion and $60 billion. Spending $40 billion would directly add more than $1,250 per annum to home electricity bills each year for about 50 years and roughly eight times that for businesses. Overhead powerlines were cheaper to maintain and, when there was a fault, power can be more quickly restored when compared with underground lines.
SA Power Networks said that, despite the high cost of undergrounding, it would support expanding the South Australian government’s powerline environment committee. The committee, administered around $10 million annual funding from SA Power Networks and the local government sector, met monthly to review council proposals to underground sections of power lines in “strategic” locations. Over the previous 20 years, 212 kilometres of overhead powerlines have been undergrounded through the committee. SA Power Networks suggested that its “most cost effective approach” was to install conduits – tubing protecting electrical wires – to “facilitate potential undergrounding at a later stage”.
A spokesperson for the Local Government Asssociation of South Australia said it understood the significant cost to undergrounding powerlines “but if we’re serious about improving our tree canopies for better greening and cooling, particularly in our urban communities, then these are the discussions we need to have.”
