HIGH CROSSING TOWER PILE CAPS, SPENCER GULF, SA
Electranet Transmission Services is responsible for the transmission of electricity throughout South Australia. Following inspection of the transmission pylons across the Spencer Gulf near Port Augusta, it was evident that the concrete pile caps to the five marine towers were deteriorating due to salt attack on the reinforcing steel. Existing coatings had failed, and various spalls were visible on the concrete, which had been repaired some time previously.
Electranet called tenders for the necessary repairs, and a contract was awarded to Marine & Civil Maintenance in June 2004.
The specification called for concrete repairs by sprayed gunite to the damaged areas and the application of a silane primer and a methacrylate top coat system to all surfaces of the twenty pile caps. In addition, the shrinkage cracks around some of the previous repairs required epoxy resin injection.
While the materials and methods were straightforward, the location of the work in an exposed offshore site provided challenges for access and protection of the environment. Purpose-built scaffolds were erected at each pile cap so that repairs could be made to the soffits and sides of each. Plant, such as the compressor and gunite machine, were stored with the bulk materials on a 9m barge, which was moored at the site and was attended round the clock by a work boat and a qualified operator. Two other boats were used to ferry staff and materials between the site and Port Augusta.
Work was completed ahead of schedule in ten weeks.