Chlorine taste in tap water unlikely

Christchurch’s drinking water supply will be chlorinated by the end of this month – but the levels are likely to be so low people will barely taste it.

The Christchurch City Council has received confirmation from the Drinking Water Assessor (DWA) of the amount of chlorine needed to provide adequate protection.

This comes after an assessment of the city’s well heads found they were unsafe and vulnerable to pollution from dirty surface groundwater.

Council chief executive Karleen Edwards said that because the chemical was to be used as a preventative treatment rather than as a treatment for an existing contamination, not as much chlorine needed to be added.

The council decided in January to treat the city’s water supply for up to a year.

This was in an effort to stave off potential contamination after the assessment of the well heads.

Chlorine would be added at 56 of the city’s pumping stations from late March.

An exact date was yet to be released.

Council city services general manager David Adamson said it was hoped that when all the well heads leading into a pumping station were repaired, that station would no longer need to be chlorinated.

However, the heads would need to be signed off as secure by an expert and the Drinking Water Assessor before this could happen.

He said the level of chlorine was likely to be so low that people would barely be able to taste it.

The council was also now facing a big bill to repair the well heads.

It was originally thought only 28 wells needed repairs at a cost of $840,000, but assessments have shown 103 do not meet the standard.

Council three waters and waste head John Mackie would not say what the additional cost would be because the work was still being scoped and priced by a panel of pre-qualified contractors.

However, the council was still committed to having the work completed within 12 months, he said.

Other, less urgent, capital projects would need to be delayed to fund the increase.

An external review has been launched to uncover all the events leading to the city’s water supply having to be chlorinated.