The glass was dumped at the site on Hadlow Drive in Bywong more than two years ago, and residents say when the trucks started bringing the pile from Canberra they contacted the Yass council, but nothing was done.

Denise Hudson, who lives nearby, said she had also written to the ACT government, including ministers, in 2015, asking what authority the contractor had to take the glass from Canberra and what was being done to ensure it was properly handled.

She believed the glass came from the ACT government materials recycling facility at Hume and was uncleaned, with the possibility of medicine bottles, syringes or other material among the dump.

"This guy somehow or other brought out tonnes of this stuff without any due diligence from the ACT government," she said.

"You can imagine us jumping up and down and saying we're worried, we're worried, help us out here. It's been a litany of failures, I believe, that's my opinion, on the part of the Yass Valley Council."

Ms Hudson said water flowed from the dump site to a floodplain east under the Federal Highway into dams on rural properties and from there to Brooks Creek, which flowed to Yass dam.

Residents were concerned about contamination of their dam water, and were concerned when the contractor had a glass crusher on site about the dust contaminating their roof-fed drinking water.

Glass sent to recycling in Canberra, including through household bins, is now processed by Re Group at Hume, which is crushing it as an alternative to sand for asphalt, concrete, sandblasting, pool fliltration, and as a heavy cover for dangerous landfill. Re Group took over in February 2016.

It is unclear what happened to Canberra's recycled glass before then, but the Yass Valley Council said the amount that ended up at Bywong was "staggering", with "hundreds of truckloads".

"Our guys have been staggered by the amount and they haven't been able to estimate it with any degree of accuracy," council director of planning Chris Berry said.

The operator had planned to establish glass recycling on site, but his application hadn't met the threshold and had been withdrawn.

The council had begun enforcement action to have the site cleaned in 2015 but had been forced to withdraw the order after its legal team found "technical problems" with it.

It started again on another direction to clean up the site, but in the meantime the operator had transferred to the property to a family member and filed for bankruptcy.

The new owner didn't have the financial or technical ability to clean up the site, Mr Berry said.

"We reassessed on that basis and suspended the action because there's no use chasing somebody if they can't do it," he said.

The council had told the owners that if they applied for planning permission to build a house on the site, or change the zoning, they would have the clean up the glass.

In the meantime, the council believed the dump, while an eyesore, was "not causing us any significant environmental or public risk at this stage", so it had been ranked a low priority.

Mr Berry said there was no evidence to suggest there was anything but crushed and processed glass on the site.

While the council had the power to clean up the pile and pursue owners for costs or recover costs from the property, the clean up and legal costs would be borne by ratepayers and the property, as "a couple of hectares of vacant land", was not worth much.

"It would be a bucket-load of money and we don't think the ratepayers should have to pay that," he said.

A series of questions were put to the ACT government on Wednesday, which responded only to say that the ACT did not have a contract with the company concerned.

Resident Roger Melton, who spoke with ACT waste authorities on Wednesday to no avail, said the NSW and ACT governments should "knock their heads together and come up with a solution".

"Somebody is going to have to pay. Somebody always has to pay when administration fails, and this is a classic case of administration failing."

Mr Berry said the council had considered topsoiling over the site and landscaping it, but NSW environmental authorities were not happy with the option.