Water Supply Resilience
What can we do to prepare for compromises to our water supply?
Water Treatment Plants:
The water for the Hauraki Plains communities is supplied from two interconnected water treatment plants (WTP). The larger plant at Kerepehi can produce 12.5 million litres per day. The smaller Waitakaruru plant can produce 6.5 million litres per day.
The Kerepehi WTP takes water from the Waihou River at the Pekapeka intake located on Hauraki Road. The Waitakaruru WTP takes water from the Mangatarata Stream. We also hold a consent to take water from the Waitakaruru River and store it in a former Quarry on Steen Road. We can store raw water during winter time to use in the warm summer months as both the Waitakaruru River and Mangatarata Streams often drop below the consented take-level. The raw water supply for Waitakaruru WTP is then used only from the Quarry Raw Water Reservoir
The plants treat the water to a high standard (both WTP’s produce water that exceeds the required drinking water standards). This is stored in potable water reservoirs (10ML at Kerepehi and 1.1ML at Waitakaruru) and then pumped out into the reticulation network by a series of booster pumps.
Our reticulation network (pipes and pumps) is made up of 364 kms of pipes – the oldest installed in the 1930’s. The reticulation network is made up of a combination of brittle (iron, asbestos and concrete) and ductile (uPVC, MDPE and alkathene) pipes. Unfortunately 224 km of the Plains reticulation network is classified as brittle.
What are the risks to our potable water supply and what can be done?
Earthquakes
The Kerepehi fault line runs generally north – south through Plains and out into the Firth of Thames.
In the event of even a small earthquake, we will likely see damage to our brittle pipes.
A large earthquake could see significant damage to our intake structures, raw water storage tanks, water treatment plants, treated water storage, booster pump-stations and our brittle networks. This means a significant, if not complete, loss of treated water supply for all of our communities.
What are we doing to improve Resilience?
Water supply:
We are preparing a new resource consent application to enable us to take additional water from the Waitakaruru Stream to fill the Quarry, increasing the resilience of our supply. This should help maintain our supply during periods of drought.
Networks:
We have a works programme in place to replace the brittle pipes. This includes a current $6M replacement project for the raw water main for Kerepehi.
We are steadily replacing the network based on how critical the pipe is for the network. The more critical a pipe is for the overall network, the higher it is on the replacement list.
The brittle pipes are replaced with MDPE (Medium Density Polyethylene) pipes which are significantly more resilient.
We are also investigating the option to connect the Paeroa network to the Plains network. This will mean we can supply the Plains with water from the Paeroa Water Treatment Plant, if the treatment plants in the Plains are compromised.
Our communities will be provided with drinking water with tankers and water containers should the worse happen and we have a complete loss of supply from the treatment plants.
What can you do to be prepared?
Leaks
If you see a leak in the network, please contact our Service Request team either via phone on 07 862 8609 or 0800 734 834 (within the district) or online at www.hauraki-dc.govt.nz Remember a leak that looks small above ground may be a massive leak underground.
Urban Properties
For those who live in towns, make sure you have your emergency kit ready for earthquake situations. Visit the https://getready.govt.nz/ website for more information.
Farms and Rural Properties
For farmers and rural properties, to make sure your supply is continuous, you will need to have 24 hours of storage onsite. If you don’t boost your supply, you may find you lose water pressure or water completely during times of peak demand.
If there is a large earthquake, farms may be without water, besides any 24 hour supply storage. Fonterra and Dairy NZ have shown that they can and will mobilise rural support during response to earthquakes. This was demonstrated during the Christchurch and Kaikoura earthquake events.
The length of time for the loss of potable water production, depends on the level of damage caused to infrastructure and which infrastructure is actually damaged.