Pilot Bay, Matura foreshore, Waimapu Estuary and Waikareao Estuary have been affected by sewer overflows.
Contamination could also be from from flood water that has been through industrial areas, garages and storage sheds. The Chapel St overflow was a controlled release of treated wastewater from the Chapel St plant. Mr Currin said it was necessary for to release water for about 30 minutes on Saturday morning after the treatment plant became overwhelmed with double the usual volume of water that was entering the wastewater system.