On the morning of Saturday 9 December, partially treated wastewater was discharged from the Raglan Wastewater Treatment Plant at the mouth of Raglan Harbour on the OUTGOING tide without having been through the ultra-violet light treatment.
This was due to a failure of the final UV treatment at the plant. The plant’s automated shutdown system had been initiated.
An unauthorised action of a treatment plant operator saw the automated shutdown overridden and approximately 260m3 of partially treated wastewater was discharged.
This discharge did not enter the harbour as the discharge was completed in the correct tide sequence – the outgoing tide.
An investigation is under way and Waikato Regional Council have been notified of the breach.
Due to the limited volume of partially treated wastewater on the correct tide, there was minimal risk to human health.
Dilution and mixing with water going out through the harbour mouth and out to sea, saw the discharge dissipate quickly as it does normally.
The Raglan Wastewater Treatment Plant does have an automatic shutdown which worked correctly when the UV failed to operate, but this was overridden temporarily by an operator, which will be part of the investigation.
The reason it is partially treated wastewater is because while it has not had the UV treatment, it had been through the full pond treatment.
The time of the discharge was between 7:48am to 9:08am.