Te Mato Vai
Providing a reliable supply of safe drinking water to the people of Rarotonga
The purpose of the Te Mato Vai project is to replace Rarotonga’s aging water network, improve storage and introduce treatment to provide our people with a reliable and safe water supply.
Addressing a number of environmental and health risks associated with the island’s current water network, it is one of the largest and most important projects ever to be undertaken in the Cook Islands. The Te Mato Vai project is a development milestone for the Cook Islands and will have significant national health, economic and environmental benefits.
The project is a vital component of the Cook Islands National Sustainable Development Plan and complements a range of work underway in the renewable energy, tourism, education, health, transport and economic sectors – all designed to ensure a more prosperous future for the Cook Islands.
At the heart of the project is an extensive overhaul of the infrastructure that collects and distributes water throughout Rarotonga. Te Mato Vai will establish a new pipe network and significantly upgrade 10 of the island’s 12 water intake sites, introducing new treatment and storage facilities, to manage demand more effectively.
This major development initiative is possible due to the first-ever tripartite agreement between the Governments of the Cook Islands, New Zealand and the People’s Republic of China.
Alongside our work to build new infrastructure, we’re also aiming to encourage responsible water consumption, as water usage in Rarotonga is excessive by world standards.
Water supply
improvements
Rarotonga’s water supply comes from 12 water catchment valleys. These catchments feed twin pipes – the outer and inner ring mains – that circulate the island and connect to water users through a series of cross main and sub main pipes.
The Te Mato Vai project will deliver significant improvements to both the mains pipe network (Stage 1) and the intake catchments
(Stage 2).
After the new treatment facilities are completed, we will install water meters and new data monitoring technology. This will enable us to track water usage to understand how much water is being used, and where and when.
We are also future proofing the treatment facilities to enable disinfection through chlorination.
Project timeline
2016 - New ring mains construction
The Chinese Civil Engineering Construction Corporation (CCECC) completed construction of the new ring mains in December 2016. This work included installation of just over 55km of pipeline. The construction contract included a 12 month ‘liability period’ from January 2017, during which the CCECC was responsible for rectifying any defects.
The PMU continue to monitor for any defects, and regularly inspect reinstated stream crossings particularly following heavy rainfall events.
Landowner consultation
In late 2016 we met with landowners of all 10 intake sites to discuss the works associated with planning for Stage 2 of the Te Mato Vai project. Landowners of all sites granted consent for us to access the sites to undertake survey and ground investigation work.
2017 Trunk main commissioning
Construction to connect the existing trunk mains to the new ring mains commenced in May 2017. The trunk mains at Turangi, Matavera, Tupapa, Ngatoe and Papua were the first to be connected. In September, the Cook Islands Trading Corporation (CITC) Building Centre was awarded the contract to supply the materials needed to connect the new ring mains from Avarua to Kauare.
2018 Ring main commissioning
Ring main commissioning commenced in mid-January 2018 with work crews connecting sub-main and commercial property water pipes to the new ring main, starting in Muri and continuing around the island. The ring main commissioning works were scheduled to take approximately 26 weeks. However works progressed well and the works were completed much earlier than scheduled, in mid-May 2018. The new ring mains are now ‘live’.
Stage Two works
The contract for the design and construction of Stage 2 was awarded to McConnell Dowell in August 2017. In mid-September 2017, the McConnell Dowell team began surveying land at each of the 10 water intake sites, following with ground investigations from mid-October. Investigations at the intake sites involved excavating test pits to understand soil conditions, to inform the preferred location and form of the proposed structures.
The next stage of consultation with landowners began in late 2017, to present initial detailed designs of the structures to them.
Construction is complete at most sites, and commissioning is underway. ‘Commissioning’ means we will disinfect all the new water system infrastructure, then connect it to the public water network that supplies Rarotonga’s homes and businesses. As it gets connected, the public water supply will go through all steps of the new treatment system except chemical disinfection (chlorination) of the water supply. See our blog post about commissioning for more on this.
We are aiming to complete the Te Mato Vai project in 2020.
2020 and beyond
Following completion of the physical works by 2020, the project will enter an operation and training phase, as To Tatou Vai employs local people to operate and maintain the new water supply system. The system will incorporate water meters and a control and distribution system (known as a SCADA system) to enable efficient water usage monitoring and management.
The Te Mato Vai project is a development milestone for the
Cook Islands and will have significant national health,
economic and environmental benefits.
Stage One
Replacing and connecting the new mains
We’ve replaced the old asbestos ring and cross mains with new pipes made from an extremely durable, high density polyethelene material. The new ring mains have been commissioned and are now ‘live’ with water running through them. Water is taken from an intake, and will be treated through the new upgraded treatment and filtration facilities (Stage 2).
Water then travels via the trunk mains, which are connected to the new ring mains and ‘sub mains’ which carry water to property boundaries.
The old ring mains will remain operational until we’ve connected all properties still connected to the old ring main to the new ring mains, either directly or via a sub main.
Stage Two
Upgrading the intakes
The contract for the design and construction of Stage 2 was awarded to McConnell Dowell in August 2017. In mid-September 2017, the McConnell Dowell team began surveying land at each of the 10 water intake sites, following with ground investigations from mid-October. Investigations at the intake sites involved excavating test pits to understand soil conditions, to inform the preferred location and form of the proposed structures.
The next stage of consultation with landowners began in late 2017, to present initial detailed designs of the structures to them.
Construction at all sites has commenced, with many sites nearing commissioning. The aim is to complete all Stage 2 construction by 2020.
Water Treatment
‘Potable water’ is a term commonly used to describe water that is considered safe for human consumption whether through drinking, cooking or personal bathing. Multiple treatment steps are needed to get Rarotonga's stream water potable.
This is because stream water contains harmful micro-organisms including bacteria and viruses that can make people sick. Regular water safety tests completed by MoH’s Public Health division have shown that community water stations are not reliable sources of safe drinking water.
You can read To Tatou Vai's water testing results here, and the Ministry of Health's test results here.
The diagram below explains the four key steps we'll use to treat the public water supply:
The Te Mato Vai project management unit has assessed the most commonly used water supply disinfection options – these are UV, ozone and chemical (chlorine) systems. Factors considered include safety, complexity, reliability, capital cost, and ongoing operational and maintenance costs.
Based on this assessment, the PMU recommends chlorination as the safest, most cost-effective and reliable disinfection system for Rarotonga.
More detailed information and answers to the most common questions is available via our publications page.
In the video below, Water New Zealand's water quality expert Jim Graham explains why disinfection is important.
Don't like chlorine? It's very easy to remove from your drinking water. Watch the video below to learn how:
A closer look at the water treatment system
![IMG_2430[1].jpg](https://static.wixstatic.com/media/596eb4_9800445e435b4d998c1b90d81a8869bc~mv2_d_3264_2448_s_4_2.jpg/v1/crop/x_0,y_120,w_3264,h_2208/fill/w_204,h_138,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/IMG_2430%5B1%5D.jpg)
Frequently Asked Questions
General questions
What is the purpose of Te Mato Vai?
The Te Mato Vai project aims to provide everyone in Rarotonga with a reliable and safe water supply.
Why is it necessary?
Upgrading the water network will have significant national health, economic and environmental benefits. Access to safe drinking water benefits all of us - it supports healthy families and makes Rarotonga a safe place to live in and visit.
The current system relies on old, leaking pipes, has limited storage capacity (which affects year-round supply) and does not include any treatment facilities to filter out debris and sediment.
How much is it costing, and who is paying for it?
Te Mato Vai, the largest infrastructure project in the history of the Cook Islands, is expected to be completed by 2020 and estimated to cost approximately $89.7 million. The project is funded through a tripartite agreement between the governments of the Cook Islands, New Zealand and the People’s Republic of China. Originally it was scoped in the 2013 Masterplan which identified $60 million as a rough cost estimate, from a likely range of $30m to $90m based on the scope definition at that time.
The Te Mato Vai project started in 2014 and was divided into two stages with several parts to each stage. Between July 2016 and present day, a number of Te Mato Vai project activities have been completed and, for a number of reasons and requirements, activities have also been added, or re-priced. The increased scope has also resulted in additional community benefits, for example we’ve upgraded some of the access roads to the intakes. With over 90% of the contractor’s workforce being resident Cook Islanders, much of these additional costs are being returned to our local economy, and benefiting our communities.
Who is managing the project?
The Cook Islands Government has engaged GHD New Zealand Limited to project manage the Te Mato Vai project through the Project Management Unit (PMU). A multi-agency Steering Group oversees the PMU’s work, to provide a consistent direction for Government policy and funding.
Once we have completed the project, To Tatou Vai (a new Crown-owned water authority) will operate and maintain the new water supply infrastructure.
How long will it take?
We expect the upgraded network to be operational in 2020.
Will I have to pay for water in future?
The Cook Islands Government has stated that, in future, it intends to charge for excessive water consumption. The Government will determine a free allocation, and ‘excessive use’ will be any use above the allocation. The Government will decide how much the free allocation will be in future, when more information on water use is available.
Tariffs will both encourage more responsible water use, and cover the cost of operating and maintaining new infrastructure.
How can I get involved?
You can contribute to the project every day, by only using the water you need. One of our biggest water issues is wastage. While the new infrastructure will address some of this by replacing leaking pipes and improving drinking water quality, you can help by thinking about how you can reduce the amount of water you use. Even simple changes, like avoiding running taps continuously when washing up, or spending a little less time in the shower, will make a significant difference.
Health questions
Will the water piped to my home be safe to drink?
The new infrastructure will include storage and filtration systems that will address the current water quality issues. These systems will include collecting debris at the intake and filtering sediment through a settling tank and sand filter.
To be considered safe to drink by World Health Organisation standards, we must disinfect the water to remove harmful bacteria. Chlorination is not part of Stage 2 of the project, but we are future-proofing the treatment facilities to enable this step to be added at a later stage.
PACl questions
What is PACl?
Polyaluminium chloride, or PACl, is a coagulant used in the water treatment process to remove small particles of dirt and other contaminants. When mixed with untreated water, the PACl sticks to small particles of dirt and other contaminants and clumps them together so they sink to the bottom of the tank. This process is called coagulation. Coagulation also helps remove harmful protozoa (tiny organisms that can cause diseases such as Giardia).
Why do we need PACl?
If a water source is very clean, like groundwater, water treatment without a coagulant is possible. In Rarotonga stream water contains high levels of sediment and suspended solid waste, such a bird droppings. PACl is required to help clump these contaminants together so they can be removed as part of the water treatment process.
How much PACl will be used?
The amount used will depend on how much dirt is in the water and the specific needs of each intake site. A trial will be conducted to provide us with more information on this. We will use a monitoring system to adjust the PACl dosage to suit the water quality and ensure we only use the minimum amount needed.
Do we still have to boil our water?
While using PACL will help to remove some of the contaminants in the water, we are only commissioning the first three steps of the water treatment process. The forth step, disinfection, will not be implemented yet so we recommend you continue to boil your water prior to drinking.
Is PACl safe?
Yes, it is safe to use PACl as part of the water treatment process. New Zealand and Australian Drinking Water Standards both recognise the use of PACl in water treatment to deliver clean and safe drinking water.
The water treatment steps include coagulation, flocculation, clarification and filtration. PACl is used in the coagulation step and part of the process that is recognised in the Guidelines for Drinking-water Quality Management for New Zealand as “well-proven technology for the significant removal of colour and particulate matter including protozoa (e.g. Cryptosporidium oocysts and Giardia cysts), viruses, bacteria, and other micro-organisms.”
There have been concerns from interest groups and unsubstantiated reports in technical literature about residual chemicals, such as aluminium, in the water affecting human health. The World Health Organisation concludes from a large number of studies and scientific evidence, conducted over many decades (e.g. by Srinivasan et al 1999), that adverse health risks have not been demonstrated in any credible studies.
We will be following industry practice and guidelines to ensure PACl is used safely and effectively.
What is PACl sludge?
Polyaluminium chloride, or PACl, is a coagulant used in the water treatment process to remove small particles of dirt and other contaminants. During the coagulation treatment process, PACl is mixed into the water, where it attracts the contaminants. The PACl and contaminants clump together and sink to the bottom of the tank so they can be separated from the cleaner water above. The clean water left at the top of the tank is then directed into the next step of the treatment process. The PACl and dirt that settles to the bottom of the tank is called ‘sludge’.
Is sludge safe?
Well documented water treatment process science tells us that the PACl sludge is in many respects like a soil, and can be reused or disposed of in a number of ways without damaging the environment. However, like any waste product, PACl sludge must be managed responsibly.
How much sludge will the Te Mato Vai system produce?
We can’t accurately predict how much sludge the Te Mato Vai system will produce because it will depend on weather, its effect on stream flows, and the unique conditions of each intake site. For example, heavy rainfall that disturbs the soil and carries more sediment into the stream will result in more PACl needed to remove the contaminants in the water and more sludge produced.
This is one of the reasons for the PACl trials – the trials will help us understand how much PACl to use at each site, how much sludge will be produced and the sludge’s consistency.
What will happen to the sludge?
There are a number of ways to safely and responsibly dispose of PACl sludge. Once we have results from the PACl trials we will be better able to determine the best method for Rarotonga.
During the PACl trials the sludge produced in the sedimentation tanks will be transferred to the sludge ponds for further drying and on-site storage until the best disposal method is identified.