The project comprised the replacement of the rotten timber transoms and the rail, installation of ‘check’ rail, minor strengthening works of the supporting pier and adjustments to the approaches and abutments.
The major challenges were working at considerable height above the river and limited access - the bank on each side of the track was steep and covered with thick scrub, with the northern approach alignment through a narrow cutting.
The only access to the site was along the track through a public walkway, with the road 15m below and some distance away from the base of the bridge.
The methodology involved a hi-rail excavator operating on the bridge, slewing 180 degrees to remove existing components and place new components for assembly by workers on the bridge. This method was going to require an estimated five day rack closure with consequential interruptions to rail operations and impact on the client.
During the planning, it was identified that, with some work, the car park to the Stitt River Falls walkway could provide a suitable platform on which to base a mobile crane.
This enabled the machinery to be based on solid ground, resulting in substantially less work from heights and a three-day turnaround - two days less than originally forecast.
Three-day bridge Site works involved bridge carpenters and labourers undertaking site preparation and assisting with placement of the new panels. Welders strengthened the pier and welded new transoms to the existing structure. The rail crew secured and welded the rail and adjusted the approaches.
On day two the team removed the existing rail and transoms, replacing them with new infrastructure. On the third day, heavy rain failed to hamper efforts, with the resourceful rail crew rigging up a shed over the trolley, allowing the rail joints to be welded. The track was handed back to the client in time for the scheduled train at the end of the day.