Dunedin City Council were planning to upgrade the existing wastewater treatment plant at Green Island but they believe that there had been some issues with the 1050mm diameter concrete discharge pipeline in the past, including H2S corrosion. DCC wanted to avoid a situation of completing the plant upgrade and then 'unexpectedly' having to spend a whole lot more on the pipeline. For that reason they wanted to undertake an inspection and condition assessment of the concrete pipeline to enable evaluation and planning of any remedial works that may be required now or in the future. The concrete pipe runs from the wastewater treatment plant 1.853Km to the Waldronville pump station and then an additional 0.314km to the beach.
ProjectMax was engaged to carry out the inspection of the 1050mm diameter pipeline using multi-sensor inspection unit, including CCTV, laser profiling and sonar profiling of the outfall, and then to assess condition and remaining structural capacity of the pipe. ProjectMax also evaluated the operational factors that influenced the rates of bacterial corrosion to predict remaining useful life and intervention strategies that DCC could undertake to extend the useful life of the pipe.
DCC obtained detailed information on the condition and remaining useful life of the outfall pipe which enabled them to plan for the upgrade of the treatment plant that will cater for both the current and future needs of the facility.