Toxins found in Auckland lakes

19:19, Oct 14 2014

Auckland Council will review its reporting procedures after it was revealed the public wasn't told a toxic herbicide had got into two reservoir lakes.

The move comes after it emerged Auckland water supplier Watercare did not tell the public the reservoirs - lakes Cossey and Waiora in the Hunua Ranges south of Auckland - were closed for five months this year after traces of the herbicide were found.

Council chief executive Stephen Town said today that while he was confident public safety was never at risk, “there remains a concern about who should have been informed of these events and when, and whether this should have been made public at the time”.

“I will therefore undertake a review of council's reporting procedures," he said.

“Our organisation must be as open and transparent as possible and that includes matters within the wider Auckland Council family that are in the public interest.”

Lakes Cossey and Waiora were closed between May and September after spray runoff from a nearby forestry block was washed into them following unexpected heavy rain.

Auckland draws about 20 per cent of its water supply from the lakes but Watercare communications manager John Redwood said there was never any chance of the toxin infiltrating the supply because it was at a different end of the catchment and there was a testing scheme in place to ensure the supply wasn't contaminated.

Redwood said Auckland Council was alerted to the problem but the public was never told and given "exactly the same set of circumstances" they would "probably make the same decision".

"Certainly if there's any risk or slight degree of risk to public safety, that would be an entirely different story," he said.

"The bottom line from our point of view is that it was detected before it entered the supply network and in that sense it shows those procedures do work - which isn't to say it's a good thing to have happened.

"Given exactly the same set of circumstances I think we would probably make the same decision."

Asked why, if there was no risk to safety, Watercare wouldn't inform people anyway, Redwood said: "There is nothing to be gained by informing the public."

The herbicide in question, Metsulfuron-methyl, is used to kill grass and weeds.

New Zealand doesn't have a maximum drinking standard for it but Australia's is 0.4 milligrams a litre.

Redwood said the amount was below the Australian standard: "You're talking such tiny numbers".

This was the first time toxins had infiltrated supply lakes and it had occurred because of unexpected rain so soon after spraying, he said.

"There's been forestry and similar activities carried our in the catchment for a number of years," Redwood said.

"Obviously the guys who do this will attempt to forecast the weather as well as they can.”

Since then Watercare had sat down with council, the land owner and forestry managers to look at their processes, but were confident that nothing more could have been done to prevent the run-off.

"We looked at ensuring the policies and protocols around forecasting following scheduled application dates, we've looked at notification periods," he said.

"There are some pretty strong controls in place."

Town said he was confident that proper safety procedures were in place and were followed.

“Watercare took all steps required to ensure that neither water quality nor water supply were put at risk,” he said.