Auckland Council and Watercare say they will not investigate the source of a herbicide contamination, which forced the closure of the Wellsford Water Treatment Plant last month.
The plant was closed on Thursday July 14, after routine testing found MCPA herbicide exceeded Ministry of Health limits. Water was trucked in to maintain the reservoir and the plant returned to service the following day after all tests showed MCPA levels were well below guidelines.
Watercare says the contamination did not pose a serious health risk, as the water standards are conservative and based on the risk to a lifetime of exposure to the chemical.
“The compound has not been demonstrated to have high toxicity and the maximum acceptable level established by the Ministry of Health is conservative,” a Watercare spokesperson says. “Other countries have significantly higher action levels.
“We’ve sought advice from international water quality expert Professor Colin Fricker, who has told us ‘a single set of results that exceed the MAV are extremely unlikely to represent a threat to public health’.”
Information about the closure was put on Watercare’s website and sent to media.
“By using water tankers to maintain local reservoirs, the water supply to Watercare’s 862 Wellsford customers was not affected and it was not necessary to inform them directly of the plant’s closure.”
Watercare and Council say they aren’t taking any further steps to investigate the contamination source and the responsibility for an investigation appears to rest awkwardly between the two bodies.
Watercare says it is only responsible for treating the water and it is Council’s responsibility to investigate the pollution of waterways.
But Council says it is not investigating the incident and would only investigate following an official request from Watercare, the Auckland Regional Public Health Service, or a member of the public.
Watercare maintains it has fulfilled its responsibilities.
“We have followed protocol in that we informed Auckland Council and the Medical Officer of Health immediately after receiving confirmation of the laboratory result. “This is the procedure and we have fulfilled our responsibilities to the letter of the law, ensuring our water is safe to drink.”
Watercare started quarterly testing for the herbicide MCPA two years ago following an assessment of the catchment. After reviewing the monitoring programme, Watercare decided to begin monthly testing in July due to farming and forestry activity upstream from the treatment plant. Last month was the first positive reading since monitoring began.
“This testing is not required by the Medical Officer of Health and was never undertaken when the treatment plant was operated by the Rodney District Council,” a Watercare spokesperson says.
Wellsford GP Dr Tim Malloy says he has seen no evidence that water quality was affecting the health of Wellsford residents.
“I have not been aware of any increase in the spectrum of disease at this time of year than I would normally expect,” he said.