The rail line was closed for two weeks in April after heavy rains caused landslips at a number of locations and damaged the tracks.

The urgent work saw buses replacing trains between the two stations until the day before Anzac Day, when the line was reopened ahead of schedule.

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"The South Coast line was severely impacted by successive weather events, which caused significant damage to rail infrastructure in the region," a Transport for NSW spokesperson said.

"More than 300 maintenance workers were rostered around the clock to complete various remediation, maintenance, clean-up and repairs at around 12 locations along the line."

This included working through the Easter period.

The Mercury understands the cost of the repairs has so far reached $10 million with more work still to come, which is not expected to cause any further closures.

"The final cost of repairs along the South Coast line will not be known until all work is completed," the spokesperson said.

"The remaining work may take months but this has no impact on services."

The worst-hit area was around Otford, where the rail embankment was dug out at least six metres below the level of the track.

Part of the repair bill included the removal and replacement of around 10,000 tonnes of ballast, which had to be trucked in and out of the area via Otford Road.

Heavy-duty diggers also had to be brought into the site to carry out the work.

Meanwhile the ongoing work at Macquarie Pass is expected to cost more than $2 million but the spokesman said the final cost would not be known until all work is complete.

"The repairs to Macquarie Pass are part of an emergency response to a natural disaster," the spokesperson said.

"Our first priority is to complete emergency repair work and restore access to Macquarie Pass as soon as possible."

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