Christchurch's water could still be chlorinated even with an exemption
Chlorine could still remain in Christchurch’s water supply even if the city manages to gain an exemption from a new law mandating the disinfectant.
Twenty-four of the city’s 68 reservoirs need work before they can be deemed “demonstrably safe” under Christchurch City Council’s new water safety plan.
Work to repair the reservoirs was supposed to be completed by December, but the council now says it is not sure when the work will be done.
There have been delays due to the Covid-19 lockdown, and difficulties in sourcing materials and in getting the design work finished, said council head of three waters and waste Helen Beaumont.
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Small delays in these types of projects could add a year to the timeline because the council could only take large reservoirs out of service over the winter months, when the demand for water reduced significantly, she said.
Despite the delays, the council still planned to apply for an exemption from mandatory chlorination from the new drinking water regulator Taumata Arowai.
A new law states water supplies must be chlorinated, but suppliers can apply for an exemption from March 1, 2022.
Beaumont said the council believed it was possible to be granted an exemption from mandatory chlorination even if it still had some reservoirs where the risk was “unacceptable” according to its own water safety plan.
Those areas would continue to be dosed with chlorine until the necessary repairs had been carried out, she said.
Work was either underway or about to begin at nine reservoir sites, located in the central and west zones, and one in Lyttelton. The central zone includes thousands of households from Papanui and Shirley to right through to Cashmere including the central city. The west zone takes in Wigram, Halswell and Hornby.
Another 15 reservoirs were considered to be an unacceptable risk. These were in the central and west zones.
Beaumont said the council did not yet know what work needed to be done at some reservoirs because it still needed to inspect them from the inside.
External inspections gave the council an idea of what to expect, but a full scope of work could only be finalised once an internal inspection was done.
The council could not confirm when the work would be done until all the inspections had taken place. It was not clear when that would happen.
“Until we have completed the next round of internal inspections and specified the works that are required to be undertaken, we cannot put a definitive timeline on when the required works will be completed,” said Beaumont.
As each tank was brought up to standard, the chlorine would be removed from that part of the network, subject to the well heads being secure and the backflow risk being acceptable, Beaumont said.
The council has been “temporarily” chlorinating the city’s water supply since March 2018 and has been working to remove it ever since, spending millions of dollars on infrastructure upgrades.
It has been trying unsuccessfully to get a water safety plan signed off by assessors working on behalf of the Ministry of Health for almost two years. A water safety plan outlines how the council will safely provide water to the city.
The new regulator Taumata Arowai has taken over the role of assessing the plans and would provide feedback to the council.
About 20 per cent of the city’s residents receive water without chlorine most of the time, because the council has already completed the necessary work in some areas.
Mayor Lianne Dalziel said earlier this month the council would be ready to submit its water safety plan to Taumata Arowai by the end of the year.
Once it had received feedback and taken it on board, it would apply for an exemption.
Dalziel said the council could not provide a specific timeframe for applying, but it would do so as soon as it was in a position to do so.
“Obtaining an exemption under a new framework that hasn’t been tested before will no doubt be a challenge, but we will be as well-prepared as we can possibly be.”