Can Christchurch swallow chlorination?

If a leading water quality consultant is right about the state of Christchurch’s drinking water supply, then the region may have its head in Canterbury river gravel about the risks to that supply.

Iain Rabbitts, a water consultant who was an expert adviser on the response to the Havelock North outbreak, is in Christchurch to do a health and safety engineering check for the city council on its temporary chlorination of the city’s water supply.

The council has been adamant that the safety precaution of chlorinating the water’s supply will be a temporary fix only but Rabbitt suspects that is a luxury, and one which may be removed by the Government.

The Christchurch City Council is anticipating the Government’s release of a report on the Havelock North’s drinking water tomorrow. The inquiry was commissioned in the wake of the town’s outbreak of gastroenteritis in August 2016 when more than 5000 people fell ill, with E. coli confirmed in the water supply.

Rabbitts believes that report will recommend establishing a new drinking water regulator and that if so, it is almost inconceivable that the regulator will not mandate permanent chlorination for most urban water supplies.

Mayor Lianne Dalziel has said she is concerned about the Government making a blanket decision for the country and will argue for Christchurch to be exempted from mandatory chlorination. Declaring her absolute confidence in Christchurch’s supply, she said she would ‘‘fight like tooth and nail’’ for an exemption.

Rabbitts argues that Havelock North has taught us much more about the potential risks to water supplies and that for Christchurch to somehow be exempted from mandatory chlorination, it would need to do much more than its current $21.5 million programme of upgrading and repairing the city’s 155 well-heads.

He says the council’s policy of authorising chlorination for only 12 months is forcing an unnecessary rush on that programme and that the city could get more bang for its buck if it were to step back, review the entire network and then decide how best to safeguard it.

Given the stakes, both in terms of the cost of upgrading the water supply (permanent chlorination is said to be in the ballpark of $100m), and of what might be thrust upon the city, we need to ask why the rush?

Chlorination is an emotive issue but much of that emotion is not based on sound science. Chlorination is proven safe and the potential harm from contaminated water supplies is large, despite the low risk.