Hastings Wastewater Treatment Plant discharges treated effluent to the Hawke Bay via a 3km long outfall pipeline constructed in the early 1980’s. This outfall is a critical element of the treatment plant as the historic beach discharge and short outfall are no longer acceptable to the community other than in an emergency situation.
Shortly after its commissioning, there were issues with the outfall and several significant repairs were required. This paper outlines the historic issues, the repairs undertaken, the condition investigations, rehabilitation carried out recently and further works planned to maximise the life of the overall asset whilst minimising expenditure.
A recent innovative external FRP pipe repair method for a short land based section of highly corroded concrete pipe was developed to allow the outfall to remain operational, whilst working in with the timing of low tide and minimum treatment plant flows to allow works to be completed. Repairs to a section of steel pipe and the full replacement of the ocean diffuser are also detailed in the paper.
The approach of targeted condition investigations, investment in repairs and renewal of specific outfall components is expected to significantly extend the overall economic life of the outfall system.