Severe damage to infrastructure, not water shortage, cause of restrictions

Christchurch City Council is urging the public to be patient as contractors work tirelessly to repair the city’s water supply system as quickly as possible.

Water restrictions have been in place for the City and Lyttelton Harbour communities since October this year, after the earthquakes in September 2010, and February and June this year caused severe damage to the water supply network.

The recent earthquakes on 23 December also resulted in further damage to the network, which has placed increasing pressure on contractors to repair new breaks to pipes. Over the last six days, contractors have made solid progress in repairing major leaks which has helped reduce the total demand on the water supply system.

Council City Water and Waste Manager Mark Christison says that the issue is not about the amount of water in the aquifers below the city, but rather the network’s ability to pull this water up from the aquifers and deliver it around the city to meet the peak demands during the summer season.

Mr Christison says these summer peaks are three to four times the size of the average winter demand and this increase is due almost solely to outdoor irrigation use.

“Normally reservoirs help to buffer the heaviest demand days but the city has lost its largest reservoir (32,000 m3 at Huntsbury). To-date we have managed to replace this with a 6,000m3 structure. This means the city has lost key storage at a time when water demand is at its peak.

“The damage to our water infrastructure is serious and whilst we are making good progress in restoring assets to service, the ongoing large earthquakes are causing ongoing issues by causing more water pipes to crack and leak. After each significant earthquake, all wells and wellheads must be reinspected and any that are found to be damaged have to be shut down until repaired. This creates more work for contractors and frustrates building the capacity back into the network,” he says.

The Council has made significant progress on repairing the City's reservoirs and it is only this work that has enabled the water restrictions to be limited to Level 3. Major repairs have been completed at Denton (Avonside) and Sockburn reservoirs as well as a new 6000m 3 reservoir being commissioned just before Christmas in the old Huntsbury Reservoir. A further 13 reservoirs have been repaired since the 22 February.

While the Council recognises that the possibility of a total outdoor watering ban will frustrate some residents, the ban will only be necessary if significant earthquakes, dry weather conditions and public non-compliance with the current water restriction rules occur.

Mr Christison says the Council has also investigated connecting suitable private wells (those which meet Ministry of Health Drinking Water Standards requirements) into the public system to help supplement the network over the summer months. However, only one well (in South Brighton) has been found suitable to meet this need and will be connected early in the New Year. Water consumption in the last 24 hours has dropped due to repair crews making good progress on leaks and cooler, wet weather.

“We would like to thank the community for their understanding shown to-date, but ask people to remember that the real challenge for keeping summer water demand under control will occur over the next 8 - 10 weeks through January and February. Strict adherence to the current water restrictions will hopefully get us through the summer, subject of course, to no further large quakes,” Mr Christison says.

Water Restrictions – Facts

Level 3 water restrictions have been in place for Christchurch and Lyttelton Harbour communities since 8 October this year.

The restrictions have been imposed under the Water Related Services Bylaw 2008.

The restrictions do not apply to residents and businesses that have private wells on their properties or require water for production such as garden centres and car sale yards.

The network repairs since 22 February include:
- 72 wells repaired and back in service (17 wells are yet to be complete).
- 26 kms of water mains have been replaced.
- Repairs to 13 reservoirs have been completed.
- A new smaller 6000m3 reservoir has been commissioned in the old Huntsbury reservoir (6000m3 capacity). The second unit will start construction in the New Year.
- A new water pump station has been commissioned at the Huntsbury site.
-The new Rawhiti Water Pump station is in its final stages of design.
- 7 new wells have been drilled and are currently being commissioned onto the network over the next month this includes an Environment Canterbury monitoring bore in South Brighton. Another two wells should be available by Autumn 2012.

The total repair bill for damaged water infrastructure is estimated at $146 million, however, recent damage caused by December’s earthquakes is sure to increase this cost.

If Level 4 water restrictions are imposed this will mean a total outdoor watering ban for all residential and commercial businesses that draw water from the public supply (i.e. not those who own private wells).