Minister for Transport John Graham is confident a rail maintenance blitz on the weekend on the line south of Sydney to Wollongong will overhaul reliability for commuters.

With more than six million people using the over 100-year-old South Coast and 40-year-old T4 line each month, the line was declared a “maintenance critical zone”.

Major trackwork was undertaken on the T4 Illawarra Line and South Coast Line between Dapto, Port Kembla and Central.

At Engadine, a 250-metre section of track was renewed, whch included:

• Replacing ballast to stabilise the track and help prevent future speed restrictions.
• Specialised welding works in which the rail was cut, and taken out, to allow for it to heat up and expand in summer. This helps to manage rail expansion during summer months. In the winter additional sets of rails are added back in.
• The drainage system was graded to maintain track foundation integrity in wet weather conditions.

The maintenance team also resurfaced the section to remove defects and deliver a smoother ride for passengers.

“The T4 and South Coast Line is critical infrastructure for commuters living across the region, and passengers deserve a rail network they can rely on," Graham said.

“We’re delivering on the recommendations of the Independent Rail Review – investing $423 million in essential upgrades and fast-tracking maintenance work that keep our network safe, resilient and reliable."

He added that the disruption on the weekend was necessary "so we can deliver a safer, smoother and more dependable service".

Sydney Trains CEO Matt Longland said his team was hellbent on creating a more resilient and reliable network.

“These upgrades are exactly the type of targeted maintenance that will make a real difference for commuters," he said.

"By renewing track foundations, improving drainage and strengthening rail infrastructure, we’re reducing the likelihood of disruptions on one of Sydney’s busiest lines.”

The lines were reopened before Monday morning's peak commuter period.

Among the work that took place was:

• Completing the rebuild of platform 2 at Jannali;
• Signalling modifications and testing in the rail corridor at Hurstville,
• Ballast cleaning between Waterfall and Coalcliff;
• Embankment and cutting stabilisation works at Waterfall, Stanwell Park and Coalcliff;
• Retaining wall works at Woolooware;
• Drainage works at Coledale; rail welding works at Waterfall; and turnout refurbishment at Sutherland.