Discussing a report to the environmental science committee on surface water quality of the Water of Leith, Kaikorai Stream, Careys Creek and Waitati River, Cr Deaker asked what could be done to improve those waterways.
Environmental information and science director John Threlfall said there were no surprises in the report as an earlier State of Environment report had shown water quality in those waterways was "not great" although there had been a slight improvement.
"There is no quick fix."
This report aimed to establish a baseline water quality, he said.
Water quality scientist Rachel Ozanne said in her report bacteria levels in the urban streams were elevated and likely to be directly attributable to stormwater discharges or cross connections with foul sewer systems.
Urban stormwater contained a wide variety of contaminants, that in sufficient concentration and quantity could cause significant pollution, degrading the water quality, she said.
This was particularly the case with the Water of Leith and Kaikorai Stream, with both waterways exceeding recommended guidelines because of high bacterial contamination.
Waitati River and Careys Creek had good water quality, but in the Waitati catchment water quality improved with distance from the head waters.
Both waterways' water quality was generally within recommended recreational contact guidelines, she said.
Cr Gretchen Robertson said the report highlighted that water quality was an issue in urban and rural areas.
Mr Threlfall said the stormwater issue was a big one and involved the Dunedin City Council which managed the stormwater outfalls.
The ORC was working with the DCC, which was having to apply for consent for stormwater discharge and was developing catchment management plans to improve stormwater management.
It would cost "billions" to retrofit all stormwater lines and would require disturbing roads, pavements and people's properties.
Instead, the aim was to prevent the situation getting any worse, he said.
"It comes down to what people will accept and what they are prepared to pay for."
The city council had done a lot of hard work to fix the cross-connection problem, but it was possible some could still exist.
