Epping to Thornleigh third tracking project M2 motorway and Devlins Creek underbridge alternative design innovations, Sydney

The Epping to Thornleigh Third Track (ETTT) project is a key component of the Northern Sydney Freight Corridor program. The ETTT project involves the construction of six kilometres of new and upgraded track within the existing rail corridor between the Epping and Thornleigh stations. The new third track separates northbound freight from frequently stopping passenger trains with the intent to provide additional northbound paths for freight trains, which reduces waiting times for freight trains and increases the reliability of both freight and passenger services. Beca was initially engaged by the ETTT Alliance to carry out value engineering on the reference design and develop an innovative alternative design. Through innovations in both the design and the construction methodology, the alternative design simplified the scale and complexity of the bridge and approach embankment works. These innovations included bridge construction staging and continuity of the girders, infill diaphragms in the girders, and the construction staging of the main retaining structure. The result was significant cost savings for the contractor and client through reducing the number of spans in the bridge and the amount of temporary works required throughout construction.