Southern DHB Medical Officer of Health Dr Michael Butchard has recommended the Do Not Drink notice (DNDN) on the Waikouaiti, Karitane and Hawksbury Village water supply can be lifted.
This follows a comprehensive investigation by the Dunedin City Council into elevated lead levels that had been detected in the area, finding customer pipes, fittings and tapware leaching lead into the water were most likely the cause of the high lead results at the Waikouaiti Golf Course and the Karitane Bowls Club.
The most likely cause of the high lead result in the raw water reservoir is lead in sediment from a spike in water turbidity. Sediment is filtered out by the treatment process, so does not reach the treated water.
However, it is recommended that people at the Waikouaiti Golf Course and Karitane School still do not drink the water.
Dr Butchard has also called for greater awareness of the potential exposures of lead in the environment, either through our water via customer pipes, fittings or tapware, or other sources such as lead-based paint found on older houses – and the steps that can be taken to mitigate these risks.
“We appreciate the comprehensive investigation from the DCC, and the challenge of trying to uncover the cause of the high lead readings. We thank everyone for their understanding and patience over the past months as we have sought to understand this issue. Special thanks to the Waikouaiti Golf Club, and Karitane Bowls Club, who have worked cooperatively through this investigation.
“We will continue to work with the DCC, Ministry of Health and other agencies to raise awareness of these risks, and support public health measures to reduce exposure to lead in our environment.”
Considerations for determining recommendation to lift notice
Dr Butchard said the recommendation to lift the notice was based on what is best for public health, and acknowledged the DCC’s commitment to health-based decision-making on this issue.
He noted that prolonged DNDNs have their own public health risk due to drinking water from other sources, with roofs, private bores or dirty containers potentially becoming contaminated.
Based on the DCC’s investigation, the following aspects needed to be considered in relation to lifting the Do Not Drink Notice and determining the next steps.
No evidence of background lead in water supply
There have been no elevated post-flush lead levels since 20 January, and the vast majority have been below the level of detection. The Waikouaiti River Catchment Risk Assessment undertaken by Tonkin & Taylor found there are unlikely to be sustained elevated discharges of lead within the river catchment.
There are alternative explanations for each spike. At Karitane Bowls Club and Waikouaiti Golf club, the combination of customer plumbing, stagnant water and likely particulate material in the golf club sample are most likely to have led to the high readings. At the raw water reservoir, sediment particulate was the likely cause, due to the tank being around 40 per cent full and intake open, causing turbidity. It is important to note that particulate lead is filtered out in the treatment process.
Mitigation factors in place
A stronger monitoring system for the water supply is now in place, with testing carried out weekly, in a greater number of locations. A further real-time monitor is being calibrated, to provide an even higher level of assurance
A clear notification process for any elevated lead reading has been established.
Stronger communications messages are being launched regarding the areas of risk, namely the possibility for lead to have leached from plumbing: flush 500ml each time prior to use to minimize the risk from any lead leaching from your tap; and flush your pipes daily for 30s, and for two minutes or potentially longer if you have high risk pipes.
Further information can be found at www.dcc.govt.nz
Managing public health risk at sites with elevated readings
The readings at the bowls clubs appear to have been the result of an old meter the water passed through. This has been replaced with a plastic unit, so there is no ongoing risk to drinking the water at the Karitane Bowls Club.
It is recommended people do not drink the water at the Waikouaiti Golf Club. Further work is being undertaken on the pipe work at this location which will address the most likely cause of elevated lead readings at this site.
Out of an abundance of caution, Public Health South asked that readings were taken at other sites of community importance, namely the schools and early childhood centres. Elevated lead readings were found at Karitane School, and again this is likely due to pipe or tap fittings. Therefore we are recommending people do not drink the water at this location. We are working with the school and Ministry of Education on the next steps to address this situation.
Wider public health concerns regarding lead fittings
While not directly relevant to the question of whether to recommend lifting the DNDN in the affected communities, this experience has shone a light on a wider issue, regarding pipes and fittings that contain lead that can leach into the water supply.
We will work with the DCC to do more to raise awareness of the importance of flushing pipes and taps before drinking water
This issue goes beyond Waikouaiti, Dunedin city, or indeed the Southern district. This is a national concern, and one that requires ongoing attention, both in terms of public awareness, auditing of at-risk sites (such as those with long or large diameter customer pipes, or irrigation systems, especially with high public usage by young children), and regulation around the standards for taps, pipes and fittings on our properties.
Through our investigation, we also identified other potential exposures to lead, for example through home renovation or working with lead-based products. We remind everyone of the importance of reducing exposure to lead from all sources.
Further information can be found at https://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/lead-poisoning