Ageing underground high-voltage power cables to the Andersons Bay, Dunedin, substation will be replaced to secure the future supply of electricity to 4700 customers in Andersons Bay and Otago Peninsula.
Information supplied from Delta to Dunedin City Council staff said the two underground 33kV cables from Transpower's South Dunedin grid exit point in Portsmouth Dr to the Andersons Bay zone substation were 51 years old and gas-insulated.
The waterproof rubber outer sheath on the cables was deteriorating, causing a risk of corrosion of the metallic layers around the cable, which could lead to a gas leak.
A leak would see the cable, the area's main electricity supply, taken out of service immediately. The likelihood of that happening was low but if it did, up to 60% of customers could lose power for up to a week, Delta engineer Peter Cowan said.
The cables would be replaced with new polyethylene plastic insulated cables, at a cost of $2.7 million.
These particular cables were prioritised for replacement because there was limited redundancy or back-up supply if both cables failed simultaneously, he said.
The council's community development committee this week granted Aurora Energy Ltd, which is to install the cable, an easement to lay about 570m of the new 1.74km cable under Bayfield Park.
Delta said it had investigated alternative routes, but this was the most efficient option and the reserve's car park and turf could be reinstated with relative ease.
The work would take about three weeks, in December or January, and would involve digging a 1m-wide, 500m-long trench, with 20m of trench open at any one time.
There would be little interference with organised sports events.
The committee agreed on the condition that the company pay for the work and any council costs, pay a market rental or amortised fee, meet any construction and remedial costs, reinstate the reserve after installation and be responsible for repair and maintenance of the cable.
The application did not need to be publicly notified because the reserve would not be permanently affected and the rights of the public with regards to the reserve were not likely to be permanently affected.
Grady Cameron, chief executive of Delta (which manages the Aurora Energy network), said the cable replacement was part of Aurora's ongoing programme to maintain and upgrade network assets.
A further five sets of gas-insulated cables of a similar vintage around Dunedin would be replaced over the next 10 years, ranging in cost from $3 million to $5 million for each pair of cables.
Next on the list were those supplying the Neville St substation, next to Carisbrook, which were scheduled to be replaced in 2014-15.
The company would work with the community to ensure the least disruption possible during replacement work, Mr Cameron said.
Work around schools, for example, was intended for the summer months to minimise the effect on access and study hours.
