We had the good fortune to be able to work with Graham Construction Ltd again on the Chelmer Viaduct replacement project in Chelmsford Essex. The contract award was in March 2016 and we commenced on site in July.
The viaduct was 900 metres long, stretching over an area of wetland with a bridge in the centre over the River Chelmer. The replacement structure had been built to one side and at its closest point was less than two metres from the condemend viaduct. We were also restricted to working only on the footprint of the old structure to eliminate any futrther environmental damage or impact to the natuarl wetland area. In addition, the bridge had to be demolished keeping the tidal way open.
Work commenced from both ends towards the central bridge. On the south side we deployed an Hitachi 460 with a Rotar RDP 42S concrete cracker supported by a Liugong 922E with secondary processor, grab and bucket attachments. On the north side an Hitachi 290 excavator, with Rammer RC22 Concrete Craker was supported by a Volvo EC210 machine with attachments.
The viaduct was demolished up to each bridge abutment and all the reinforcement removed, leaving a good haul road made up of the concrete rubble. Both Hitachi machines then changed boom configuration to high reach to be able to stand on the river bank and reach out to demolish the bridge deck onto the previously installed floating pontoon deck covered with over 200 Ekki Mats. Starting from the outside beams and in the centre, the deck was progressively demolished one beam at a time, removing the concrete rubble from the pontoon as work progressed.
Actually the work had to stop for a couple of days after torrential rains flooded the wetland and we had water up to the top of the machine tracks! However once the levels had subsided.,we were able to restart and the four machines worked their way back to each end digging out the rubble and loading onto Tippper Lorries for removal off site to local recycling facilities.