Unsuitable for swimming? Water grading assessment rethink likely

A health warning sign at Corsair Bay in late January. PHOTO: HAMISH MCCLURE

A new approach by Environment Canterbury to how long-term water quality grades are assigned at swim sites around Lyttelton seems likely after it agreed to change the way it models sites for swimming suitability.

ECan science team leader Shirley Hayward said it is possible predictive modelling might also change the way long-term swim grades for the bays are assessed, to take into account predictable rainfall-driven contamination.

It comes after considerable public pressure over how ECan grades swimming sites long-term, particularly at popular sites like Corsair Bay and Cass Bay.

Corsair Bay was graded “unsuitable for swimming” for the entire summer because of high bacteria readings over the past five years – many of those readings coinciding with high rainfall.

However, testing through January this year showed the water quality was good to excellent.

Athletes ignored the warnings in the build-up to the Canterbury Classic triathlon. PHOTO: HAMISH MCCLURE

In a report presented to ECan’s water and land committee, Hayward said: “In response to concerns raised by the community this summer, we will investigate a new approach whereby rainfall-affected results can be predicted”.

“We will look at new ways to communicate the public health risks adequately to the community,” Hayward said.

This will include consistent messaging, including signage, of those risks.

Staff will also continue with faecal source tracking and other investigations to try to find out why sites have degraded, Hayward said.

The suggested change in approach will rely on other organisations, such as Community and Public Health Te Mana Ora agreeing, she said.