The Dunedin City Council recently announced it was investigating a short-term plan to divert screened wastewater into the Kaikorai Stream to avoid untreated sewage flooding residential homes and roads in low-lying South Dunedin during heavy rain.
Both Ngai Tahu and the regional council have been briefed about the plans, and a consent would be needed from ORC if the scheme goes ahead.
ORC policy planning and resource management acting director Ian McCabe said the council would be likely to impose conditions if the consent was granted.
Any application also needed to include an assessment of the environmental effects, Mr McCabe said.
There were no significant natural values associated with the main stem of the stream in the ORC's water plan, but there were indigenous animals and plants living in the large brackish water lagoon and extensive saltmarsh which the stream ran into, Mr McCabe said.
There were also environmental and cultural values associated with the Kaikorai Estuary, he said.
Any consent application would need to be assessed on the national requirement to maintain or improve water quality.
Until more details about the nature, scale and intensity of the proposed scheme were known, it would be difficult to know how any ecological and environmental adverse effects might be avoided, remedied, or mitigated, Mr McCabe said.
City council 3 waters group manager Tom Dyer said initial discussions between the three parties had highlighted potential environmental and ecological impacts.
Any wastewater diverted into the stream would be screened and heavily diluted by the amount of water in the system, Mr Dyer said.
There was already a consent for the city council to discharge wastewater into the stream during flood events, but not at the scale being proposed, he said.
