The DCC carries out all water sampling required under the national drinking water standards, set by central government. In addition, to maintain safer drinking water, the Ministry of Health, the DCC and all other councils regularly remind all residents to run water from all drinking taps and filters for a few minutes each day to remove any metal traces such as lead from plumbing fittings.
In July last year, the DCC began taking additional samples of the Waikouaiti/Karitane water supply for asset management purposes, namely to check how corroded the pipe network was. 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.
A result from the Waikouaiti Golf Club received on 13 August showed elevated lead levels. This is 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 9 October 2021. This trend indicated that the result received on 13 August 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 8 December 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 8 December samples were emailed from the lab to the DCC on 18 December 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.
We realise this will be of little comfort to Waikouaiti/Karitane residents. We have made an immediate change to our operational procedures to ensure that lab results which exceed safe drinking water guidelines, regardless of the intended purpose of the sampling, are sent to an inbox that is frequently monitored. We have also put a procedure in place to ensure that the lab actively flags to us results which exceed safe drinking water guidelines.
When staff picked up the results on 7 January 2021, we notified the independent drinking water assessor. 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 most recent sample to indicate high levels of lead was taken at the Waikouaiti raw water reservoir (at the Waikouaiti Water Treatment Plant) on 20 January 2021. We received this result on 29 January and again notified the independent drinking water assessor (contracted by the Ministry of Health).
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 2 February 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.
Detailed information regarding test results will be made available on the DCC website www.dunedin.govt.nz once it is available.