This project for Far North District Council involved the removal and replacement of 2 precast bridge deck units on Bridge D21 and 6 units on bridge D22 on Diggers Valley Road between Broadwood and Kaitaia. The contracts for the manufacture and installation were let separately purely to allow us to commence manufacture promptly. The first contract was the off-site manufacture of the precast reinforced concrete bridge deck units. The second contract involved the removal of the existing deteriorated units, demolition and rebuild of the abutment back walls to match the new panels and the installation of the new bridge units, bridge jointing and installation of guardrail / railing.
The construction of the panels was difficult because they had to be made to fit an existing bridge. Prior to commencement of manufacture we went to site with the drawings to ensure that all dimensions, interfaces, connections and details were thought about as getting the manufacture of the panels correct would ensure the installation works would also be successful.
We had to re-build the existing deteriorated abutment back walls, and to match to the new bridge panels which were slightly thicker than the existing ones. Getting the abutment back walls constructed in the correct locations were critical, as the panels had only a 6mm gap between each other to allow for expansion and contraction.
The biggest challenge that we faced was that we were unable to close the bridge fully throughout the works as there was no suitable detour route & we needed to maintain access for residents (and the school bus which used the route daily). We were able to complete the abutment back wall demolition and reconstruction and other preparatory works whilst keeping the road open under traffic management and using roadway cover plates as a temporary measure to allow a safe passage for vehicles. After liaison with stakeholders we were able to implement a two-week road closure during the school holidays to allow the bridge panels to be removed and reinstalled. This provided significant health and safety benefits and also ensured productivity on the installation works. The road was re-opened 4 days ahead of schedule.
The project was successfully completed in May 2018 ahead of schedule and the road closure minimised. The road was scheduled to be closed for 12 days however due to the fact we were able to allocate additional personnel on site, undertake long days and we had a window of favourable weather conditions for installation of the panels, we were able accelerate the programme and reopen the road 4 days ahead of schedule.
The project was completed on budget and the variations for the project were negative (saving for the client by substituting materials).