Pure water for a quarter of Christchurch as spectre of longer treatment looms elsewhere

Wednesday, 8 August 2018

Christchurch City Council water boss Helen Beaumont has warned chlorination may have to continue in a large swathe of the city.

A quarter of Christchurch will have chlorine-free water supplies by the end of the month as work to fix vulnerable wells is completed.

But half the city could have chlorinated drinking water for longer than the expected 12 months after it was found work to bring wells fully up to standard at 17 pump stations is impossible within the timeframe.

The city council is considering recruiting drilling contractors from across New Zealand and Australia in an effort to accelerate the complex operation of raising well heads above ground and head off the need for a longer period of chlorination.

Officials are also assessing the possibility of a 'sticking plaster' approach - doing enough work on 38 wells below ground at the 17 pump stations so they can be signed off as safe and made chlorine-free, and then raising them above ground so they meet standards later, potentially in two years.

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They may have to bring in costly UV treatment at 12 pump stations, which could have a bill of up to $24 million just to set up, putting the estimated budget of $35 million for the entire work programme in doubt.

The council is worried increased water use over summer could hamstring the number of wells that can be taken out of service to be fixed, and has asked residents to be conservative so it can get on with repairs.

Helen Beaumont, who heads the water supply improvement programme, warned that people face three potential scenarios - the cost of work going up, living with water restrictions or having chlorinated water for longer.

The city council wants residents to conserve water over summer so it can get on with fixing vulnerable well heads.

Beaumont told Stuff it was 'probably impossible' for the wells at the 17 stations to be chlorine-free if water use was not curtailed, saying residents will be asked their views on a water conservation campaign that could start later this month.

'That would tell us what measures people are willing to adopt and give us a sense of what's possible,' she said.

'We don't want to just assume everybody is willing to conserve water and then lock in contractors [to work on wells] who then are not able to do the work - we do want to test that.'

But she promised there would be no 'water police' out across the city, instead hoping people will understand the need to be conservative.

Residents turned off by the taste of chlorine are still flocking to a spring of fresh water in Cashmere.

A report from Beaumont updating councillors on progress revealed work on 23 above-ground wells in Ferrymead, central areas and the north west mean 24 per cent of Christchurch's supplies - to about 35,000 households - will be chlorine-free by the end of August, though this may change if summer usage puts increasing demand on the network.

Major works to fix well heads at seven pump stations supplying 17 per cent of the city's water is well under way, with most of this $7.4 million first tranche of work - which includes $2.3m for UV treatment at a central pump station - expected to be completed by the end of the year.

The second tranche of work, which involves the 17 pump stations at risk of having chlorine for longer, is unlikely to start until at least early next year.

Raising the 38 well heads that are below ground could cost between $5.85m and $13.65m, with the bill likely to rise further for minor works on other wells above ground.

There are also growing concerns that water drawn from a shallow aquifer that supplies a large section of central Christchurch may no longer be secure.

Tests have revealed that water from some of the 17 wells that access the aquifer is not old enough to be deemed secure under drinking water standards, meaning water could have to be treated with UV for years to come, potentially decades.

Beaumont said there had been no records of E.coli transgressions at these wells.