Nova Scotia Power wants to spend $2 million to shore up transmission towers that are being eaten by rust, CBC News has learned.

Eight towers on a transmission corridor bringing electricity to metro Halifax need repairs.

The problem was first discovered ten months ago on a metal transmission tower north of Beaver Bank. The steel base had failed and the lines were slack, but the tower was still standing. NSP field leader Mike Cassidy said a new, above ground support had to be built.

"We had to drive piles down 20 feet, layer I-beams across and another one through the centre of the tower and built a new space in the tower which now supports the whole weight of the tower," he said.

Rust aggravated by the pyritic slate in the ground is eating away at the steel anchors The poles are embedded between three and nine metres deep.

It leaches acid in to the soil and the water creates rust.

Charlene MacMillan, Nova Scotia Power’s manager of technical programs, said the full extent of the problem in Nova Scotia is unknown.

"The areas of pyritic slate are localized so the exact number is an ongoing live part of the project to determine," she said.

So far, Nova Scotia Power has carried out three repairs with no loss of power.

It said not every tower will have to replaced. A few will use artificial anodes embedded next to the steel base to attract the rust.

"That preventative solution is much more cost effective less and prevents us from getting into a situation where we have a tower in a failed condition," said MacMillian.

The utility said looking for rust underground is now part of their inspection process