In a release from Te Mato Vai yesterday GHD, a design company, is engaged by the Ministry of Finance and Economic Management to carry out the design work for Stage two of Te Mato Vai.
This Stage two work involves upgrades to existing intakes and trunk pipelines and new treatment and reservoir storage facilities to help improve the quality and reliability of the water supply.
GHD’s Steve Carne outlined how a comprehensive investigative process has been carried out using a dynamic hydraulic computer model of the system to define the sizes of the storages, treatment facilities and pipelines that comprise the stage two works.
Stage two will involve upgrading the existing intakes around the island that supply water to Rarotonga, provide storage and treatment facilities at those intakes, and upgrade the trunk mains or feeder pipes to the ring mains and to consumers’ connections. Stage One is the laying of the ring mains which has been underway since the beginning of this year.
The modelling shows that in times of high flow a small number of higher up intakes – Avana, Avatiu, Ngatoe, Takuvaine and Turangi – are capable of supplying the whole system.
But modelling also shows that because of the limits on the storage that can be made available, in some extended dry periods some places could still run out of water.
Reducing water demand throughout the community and reducing leakage in the current system will help further reduce this risk of supply failure.
The current model builds on the previous model developed earlier in the year as part of the Master Plan.
It is enhanced with new data and information now available since the completion of the Master Plan (that is information not available to AECON when they did the Master Plan).
This includes verification of the model with data of flows and pressures from a network of meters installed by ICI earlier this year. The designed details of the new ring mains currently being constructed under stage one of Te Mato Vai by CCECC were also incorporated in the model.
Overall though, when stage one and two are complete and the system is fully functioning, there will be more flexibility for the people who operate the system to supply water from intakes with plenty of water to parts of the system whose normal intakes are low or out of water, states the release. -Release