Untreated wastewater will continue to be poured into Christchurch's waterways during storms and high rainfall.
The city council is applying to Environment Canterbury for a new resource consent to continue discharging untreated wastewater into the waterways and harbours in emergencies.
More than 700,000cu m of wastewater, including raw sewage, had been discharged into the waterways since 2012.
Wastewater includes sewage and shower, washing machine and sink water. The wastewater system had built in overflow points, which allowed wastewater to be released during storms. It overflows into the Avon and Heathcote rivers, the estuary, Lyttelton, Diamond Harbour, Governors Bay and Akaroa.
Following the September 2010 earthquake, ECan granted the city council consent for occasional overflows into waterways so it did not flood on to people's properties.
However, because of earthquake damage, a non-enforcement agreement was put in place.
But that ceases in March, so the city council either needed to comply with its original consent, or apply for a new one.
City council three waters and waste acting head John Moore said it was unlikely to be able to meet its consent conditions, as it appeared the frequency of overflows may exceed what was allowed.
He said it would be possible to stop wastewater overflows with a new pressure sewer network, however, that would cost $3 billion.
Canterbury University's Waterways Centre for Freshwater Management Professor Bryan Jenkins said the national standard for wastewater discharges was once every two years.
However, in Christchurch it was happening once every six months, he said.
For the city's rivers to be used safely for recreation, there could not be any sewage flowing into them, he said.
"Until that's dealt with, we can't have swimmable Avon and Heathcote Rivers."