Mangakino Wastewater Renewals – An Evidence Driven Approach

The township of Mangakino was developed during the 1950s for workers constructing power stations on the Waikato River.

The 19 km of wastewater reticulation for the 660 homes is all around 60 years old and mostly earthenware.

Taupo District Council is aware that the pipes are coming to the end of their useful working lives and approximately $7million would be required for a complete renewal. This is a significant financial hurdle for the Council.

Evidence indicating the poor condition of the network included a 2006 CCTV survey of 50% of the network, high levels of inflow and/or infiltration (I/I) during rain events and the 2012 smoke testing of most of the town. However, much of this information was incomplete and of variable quality.

Taupo District Council faced a dilemma. It did not have enough information to justify the replacement of the entire network, it could not identify all the specific lines requiring urgent replacement and it could not properly plan for a staged renewal of the network.

To remove the uncertainty, and allow the development of a logical and fully justifiable solution, the council worked with ProjectMax to develop a decision-making strategy. This included undertaking a complete CCTV survey of the network and then applying a structured set of Pass / Fail Criteria to determine if a particular line could continue, required repair, or required rehabilitation / renewal.

The process illustrates the clear benefit of obtaining robust and reliable information to inform decision making. Taupo District Council can now proceed with confidence to plan the works and make appropriate budgetary provisions. The approach highlights the importance of quality control of CCTV inspections and also demonstrates the clear budgetary benefit of only renewing pipes that require this action versus undertaking potentially premature renewals based on age and perceived condition.