The council has targeted illegal dumpers by creating construction waste mounds along Illawarra roads for the past three years, and recently started placing piles of soil and other work-site waste along the dumping hot spot between Bulli Tops and Waterfall.

Less than a week after congratulating itself for the success of its dumping deterrent scheme when questioned by the Mercury, the council called an embarrassing press conference on Tuesday to reveal the bungle.

‘‘We have found small fragments of bonded asbestos in the fill material that was used, and we’ll take any actions required to make that area safe in the future,’’ director of planning Andrew Carfield said.

‘‘The fill material was considered to be clean and suitable for this use, but clearly some safeguards there have failed and we’ll need to take actions in the future to prevent this occurring again.’’

Despite the blunder, Mr Carfield and infrastructure director Mike Hyde stood by their unusual program, maintaining it was ‘‘a great initiative’’ which worked to prevent illegal dumping and re-use council construction waste.

‘‘If it wasn’t contaminated, it was going to work beautifully,’’ Mr Hyde said.

‘‘One of the principles we’ve been trying to abide by is to re-use construction materials rather than taking it to landfill. It’s been very effective over the years, but can’t be too widely used because some of our material is contaminated.

‘‘Our council staff have received training to identify asbestos, but unfortunately in this case - possibly due to the occurrence of the rain, mud and dust and so on – small amounts, little pieces of fibro cement haven’t been picked up.’’

The mounds of construction waste have been installed under a ‘‘trial’’ which was started as an ‘‘internal staff initiative’’ and has been ongoing for the past three years.

This means the council does not know the extent of its own problem.

Mr Carfield said there were 10 mounds of council waste along the Old Princes Highway which would need to be investigated for toxic fill.

The council previously placed soil mounds along Mount Keira’s Clive Bissell Drive and Mount Kembla’s Harry Graham Drive, and there are believed to be piles of similar waste near Coomaditchie Reserve.

‘‘We’re not sure of the extent of the contamination,’’ Mr Hyde said.

‘‘We don’t know where it is, it’s been found in a couple [of mounds], but we’re looking at it and we need to see what the extent of it is.’’

Mr Carfield said the council was confident the asbestos along the highway posed ‘‘no risk to public health’’ as the mounds had been covered in mulch to make them safe. He also said there was no risk to Cataract Dam’s catchment even though some of the piles have been placed in water catchment Special Areas.

The stuff-up could prove costly, with the possibility the NSW Environment Protection Agency could fine the council for placing the carcinogenic material along the road.

On Tuesday afternoon, the EPA issued a statement to say it was investigating the council and was ‘‘still considering what level of regulatory action to take and will make a decision in the next few weeks, once the investigation is complete’’.

The EPA’s director of waste, Steve Beaman said he was was ‘‘very concerned’’ about the council’s actions and had requested immediate action be taken to secure the site and safely remove the materials.

The agency also said it was made aware of the contaminated soil mounds last Wednesday afternoon ‘‘following a call from local media’’. 

Last week, a council spokeswoman assured the Mercury the council had cleared the waste piles by the environment watchdog and other government agencies.

‘‘We received universal support from these agencies for the initiative,’’ the spokeswoman said.