Some of the proposed modifications and additions were:

a new dive structure just east of Westmead Station and new platforms at Parramatta Station;

a tunnel under Harris Park connecting the Great Western Line to the Carlingford Line at Camellia

duplication of track along the existing Carlingford Line from Rosehill-Camellia to Carlingford;

a tunnel connecting Carlingford with Chatswood via Epping with new stations at Macquarie University, Macquarie Park, Delhi Road and UTS including construction of a cut and cover tunnel under the Lane Cove River; and,

upgrading of seven existing stations.

Expected usage of the upgrade was:

During peak periods, there are expected to be about 10 trains per hour between Epping and Chatswood and about 6 trains per hour between Parramatta and Epping. The total travel time between Parramatta and Chatswood is estimated to be around 25 minutes.

Later the upgrade was reduced to Epping and became the Chatswood to Epping rail link.

Some facts about the link follows and were obtained from Thiess, one of the Builders of the link.

The Epping to Chatswood Rail Line is the largest publicly-funded infrastructure project underway in NSW. Its 12.5km of underground passenger rail line will link the Main North Line near Epping to the North Shore Line near Chatswood. Two separate tunnels are being constructed, with cross passages spaced approximately 200m apart to ensure passenger safety in the event of an emergency. Crossover passages, allowing trains to change between the tunnels, are also being constructed at three points along the route.

Thiess and Hochtief are undertaking the project together in a fully integrated joint venture (THJV), with Alstom as the exclusive subcontractor for systems elements. The Thiess Hochtief Joint Venture’s CIVSYS-1 works involve the design and construction of the twin tunnels, dives, cut and cover structures and other civil works to accommodate a new twin-track underground heavy rail line.

This includes the bulk excavation and concrete structures for three new underground stations at Macquarie University, Macquarie Park and Delhi Road, together with an underground extension to the existing Epping Station.

Other aspects of the joint venture’s works are the design, construction and commissioning of rail systems including permanent way, signalling, electrification, ventilation, communications, fire services, walkways, noise mitigation and other services for the section between Chatswood and Epping.

Each measuring approximately 7.2m in diameter, the rail tunnels are separated by a central pillar and were excavated by Tunnel Boring Machines (TBMs) operating on a 24-hour basis. Most of the rock excavated for the tunnelling works was removed via a conveyor system through the tunnels, with almost 100% being reused or recycled.

When opened in 2008, the new line will be fully integrated into the CityRail network, create the capacity for an additional 12,000 rail passengers a day and make public transport more attractive to a greater number of residents and visitors to Sydney.