Waikouaiti and Karitane residents have been told to stop using tap water for drinking, cooking or preparing food until further notice.
The order was issued yesterday after a sample taken at the Waikouaiti reservoir on January 20 showed an elevated level of lead. The result, received on Friday last week, prompted yesterday's notice, but the Dunedin City Council and Public Health South had already received indications several times in recent months that something was amiss.
The Dunedin City Council revealed today six samples out of 90 taken in the past six months returned results with elevated lead.
The first of these was received on August 13, 2020.
The council says that after a verification test, and consultation with an independent drinking water assessor, it was determined this was a one-off spike rather than any indication of a widespread issue.
Regular sampling continued and at that stage, there was no evidence of continuing elevated levels of lead in the water, the council says.
Dunedin City Council infrastructure services general manager Simon Drew said it was important for residents to understand yesterday's notice was issued as a precaution based on public health advice.
Of the six results with elevated lead levels, four were recorded at the Waikouaiti Golf Club – near the end of the supply line – one at the Karitane Bowls Club, and one at the Waikouaiti raw water reservoir. No elevated results were recorded at a sample site on the main street of Waikouaiti.
Any decision to issue a notice not to drink the water is based on expert public health advice.
All of the results with elevated lead levels received by the council were sent to the independent drinking water assessor contracted by the Ministry of Health and decisions made in consultation with them, the council said.
The key result that led to the notice being issued was from a sample taken at the Waikouaiti reservoir on January 20. The sample result was received by the council on January 29 and forwarded to the drinking water assessor.
On Monday, Public Health South called a meeting to discuss the appropriate course of action. That meeting took place yesterday morning.
The council then received advice from the medical officer of health that all consumers on the water supply should be advised not to use tap water for drinking, cooking or preparing food until further notice.
The council said it acted on that advice immediately.
The tests were not part of regular monitoring of water. They were to assess corrosion of pipes.
The council began taking the additional samples in July.
This sampling was undertaken at four sites – the Waikouaiti Water Treatment Plant, Waikouaiti township, Waikouaiti Golf Club and the Karitane Bowls Club – and was not expected to detect elevated levels of lead.
The council said the August 13 result showing elevated lead levels was "not completely uncommon, as lead can occur in water due to corrosion of old pipe fittings and private plumbing fixtures".
"On receiving the results, we notified our independent drinking water assessor and put in place an increased sampling and ‘pipe flushing’ plan. Flushing helps to remove metal traces from pipes. In consultation with the drinking water assessor, this action was considered appropriate until more data could be gathered.
"During the next 14 weeks, lead tested well below the acceptable limits, except for one result at the Waikouaiti Golf Club on October 9, 2020. This trend indicated that the result received on August 13 may have been an isolated incident at a localised point on the network.
"The next result which returned elevated levels of lead was from samples taken on December 8, 2020, at the Waikouaiti Golf Club and Karitane Bowls Club.
"Sample results take around 10 days from the day of sampling. Therefore, the results of the December 8 samples were emailed from the lab to the DCC on December 18, 2020.
"Unfortunately, because this sampling had been for asset management purposes rather than for drinking water standards monitoring, the email was sent to an inbox not being monitored while the staff member was on leave."
The council said this would be of little comfort to Waikouaiti and Karitane residents. Procedures had been changed.
When council staff picked up the results on January 7, 2021, the drinking water assessor was notified again.
"Again, the expert advice we received was that more sampling and investigation was required to determine the extent of the issue. Public Health South concluded that public notification was not yet required.
"The result at the Waikouaiti raw water reservoir was the first time we had received results showing elevated lead levels at the water source.
"On February 2, 2021, we received advice from the medical officer of health that all consumers on the water supply should be advised not to use tap water for drinking, cooking or preparing food until further notice. We acted on that advice immediately and put a range of measures in place to inform residents and provide safe drinking water."
Southern medical officer of health Susan Jack said today Public Health South had received information about two unusually high test results that had been gathered by the council before Christmas.
"Our initial approach was to check the accuracy of the results, any particulars around the testing sites, and monitor the situation closely," Dr Jack said.
"On Monday, we received information that an elevated result had been gathered from raw water at the reservoir.
"This raised concerns that there could be contamination in the wider water supply, so we made the recommendation to take a precautionary approach, and advise residents to not use tap water for drinking or food preparation while we seek to understand what is happening.
"We understand this has been concerning news, and thank the community for their co-operation as we work to better understand this situation.
"We are recommending households not use tap water for drinking, cooking or preparing food while the source of contamination is investigated. It is still safe to use the water for bathing, washing hands and clothes.
"We remind everyone that boiling water does not remove lead. Rather, it can increase its concentration in water, so it is important for people to follow the advice and do not drink the water, or use it for cooking or preparing food.
"If you have any health concerns in relation to this, we recommend you discuss this with your GP, who can undertake an assessment and arrange for a blood test if it is deemed necessary."
