An elevated level of arsenic has been found in two drinking water suppliers who treat water from the Waikato River.
Local Government Minister Simeon Brown has been briefed and has asked New Zealand’s water regulating authority to ensure water providers in Auckland and Hamilton are taking appropriate action.
In a statement this evening, Watercare said there was “no immediate risk” to public health.
It said the maximum acceptable value for arsenic in New Zealand was 0.01 milligrams per litre. Watercare reported a result of 0.011 milligrams per litre to national water regulator the Water Services Authority – Taumata Arowai from a sample taken on November 25.
Meanwhile, Hamilton City Council’s testing on November 19 and 20 recorded results of 0.0113 and 0.0115 milligrams per litre, which were also reported to the Water Services Authority.
“Further sampling has been carried out and Taumata Arowai will receive the results of these tomorrow,” the Watercare statement said.
Watercare added both providers followed standard procedures and were keeping the agency informed omn how they were responding.
“The agencies have extensive sampling programmes in place that have served their purpose in detecting the issue.”
Is the water safe to drink?
National Public Health Service regional clinical director Dr William Rainger said people who were drinking water sourced from the Waikato River “do not need to be alarmed”.
“The limits in the New Zealand Drinking Water Standards are based on the level of risk from a lifetime of drinking the water.
“Drinking water with slightly elevated levels for a short period of time is unlikely to impact people’s health.
“You do not need to boil your drinking water. It is safe to drink.”
Water Services Authority – Taumata Arowai head of operations Steve Taylor said: “This is a short-term exceedance of a long-term maximum acceptable values. Humans require very long-term exposure to this level of arsenic before public health is of concern. The water is safe to drink.
“Watercare and Hamilton City are working to reduce levels of arsenic.”
Where is the arsenic likely to be coming from?
According to Waikato Regional Council environmental science manager, Dr Mike Scarsbrook, arsenic was known to be elevated in the Waikato River, primarily due to geothermal activity.
“We undertake monthly freshwater testing on the Waikato River. Testing was last carried out on 7 November and the arsenic levels were not unusual. These levels are typically above the drinking water standard, which is why treatment is required before drinking water is supplied to households.”
The Waikato River supplied about 20% of drinking water to Auckland, according to Watercare chief operations officer Mark Bourne.
Bourne said in most parts of Auckland, treated water from the river was blended with treated water from dams, however, Pukekohe, Buckland, Clarks Beach/Waiau Pā, Patumahoe, Glenbrook Beach, and Drury south received water solely sourced from the Waikato River.
Since detecting the elevated result, Watercare has reduced production at its Waikato Water Treatment Plant and increased production at its major Ardmore plant, which treated water from four dams in the Hūnua Ranges.
“This extends the processing time at the plant, and we expect it to improve our ability to reduce the level of arsenic in the treated drinking water,” Bourne said.
“We’ve also stepped up our sampling at the treatment plant and within the distribution network, which includes sampling our blended water at the Redoubt Road reservoir.
“We’re working closely with other agencies and will continue to share information as we learn more.”
In Hamilton, the supply remained safe for drinking, bathing, cleaning and cooking, following the test result, Watercare said.
“Testing during a stage of the treatment process on 19 and 20 November recorded results of 0.0113 and 0.0115 milligrams per litre, slightly above the maximum acceptable values.
“Arsenic levels have been stable in Hamilton’s drinking water for many years at below 0.0100 milligrams per litre.
“The current minor exceedance of the standards does not present any immediate concern for public health.”
“Ensuring the quality of our drinking water is a top priority for [the] council and our waters team,” said unit director of three waters Maire Porter.
“While we are conducting additional testing, we want to reassure the community that we are taking the advice of Taumata Arowai, the drinking water regulator, and working diligently to make sure our decisions are based on the most accurate information available.”
Minister briefed, asks for assurance
Local Government Minister Simeon Brown said he has been briefed on the issue this evening.
“I have asked the Water Services Authority to ensure that water suppliers in Auckland and Hamilton are taking appropriate steps, and that they communicate with their customers,” he told 1News in a statement.
“The Water Services Authority is the lead agency for this issue and will be providing regular updates.”
