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."
-Star Media
