Dunedin City Council acting infrastructure and networks general manager Leanne Mash said mud tank waste was being tested for asbestos following results showing what she said were low risk levels at the Green Island Landfill.
As a precaution, the council was testing mud tank waste and cleaning procedures had been adjusted to make sure contractors and the public were kept safe.
Initial test results showed the presence of some level of asbestos in a third of the 49 tanks sampled.
Further testing was being done to determine the level of asbestos and related risk.
The council was taking advice from an independent expert and believed there was no significant risk to the general public.
"The asbestos risk is believed to be very low, but as a precaution to ensure contractor safety, a number of measures were put in place as soon as the issue was identified,'' Ms Mash said.
"As a short-term measure, this includes mud tanks only being cleaned when they're blocked, although they are still being checked regularly.
"It is not expected this will cause any issues as the last audit, two months ago, showed 97% of mud tanks were clean.
"Once results are available and safety precautions have been re-assessed, an extra truck will be added to clean all mud tanks as needed.''
In the meantime, contractors would wear protective equipment when cleaning mud tanks and the council was working with them to ensure they were following safe procedures, including proper cleaning and disposal techniques for any clothing and equipment used while cleaning mud tanks.
"We're also taking the additional precaution of using a buffer zone around mud tanks while they're being cleaned to ensure the public is well back from the area,'' Ms Mash said.
The picture would be clearer when more test results were available.
"We weren't previously aware of any asbestos in the mud tanks as it's not usually tested for. "We're letting other councils know so they can check their own systems.
"We expect other cities may have the same issue as asbestos has historically been a widely used material.''
