The developer of the former Koppers timber treatment site in Bungendore has defended the project saying the contamination is low and the remediation process will make it safe.
The proposed seniors housing project was approved by the Queanbeyan-Palerang Regional Council last week.
Alex Brinkmeyer, director of Aland Pty Ltd, is the owner and developer of the site at 65 Forster Street. He said tests were done in 2013 which showed low contamination, even in certain areas deemed "hot spots".
Last week, the Sunday Canberra Times revealed the council had conditionally approved seniors housing at the site, which is contaminated with carcinogens "exceeding the applicable screening criteria for residential land use".
Mr Brinkmeyer said given the amount of time that had passed since the Koppers facility existed at the site - about 35 years - most of the carcinogens, like arsenic, had washed away naturally.
"We're not here to cause angst or problems for people," he said.
"It's not an atomic site. In those days they used to use arsenic, but arsenic dissipates. It disappears, it gets washed away and diluted.
"It's been diluted to such a point where really it isn't much of a problem."
Mr Brinkmeyer said the exact plans to remediate the site depended on new testing, which would show how much of the soil was contaminated and where.
The process would be either to wash the soil on the site, or the more expensive option of digging down to remove the layer of contaminated soil and replacing it with new top soil.
"You can remediate any site, there is nothing new about remediation," Mr Brinkmeyer said.
After the site is remediated, an independent auditor chosen by the council would give the green light for development.
A council spokesman said a site auditor was required only where contamination issues were complex.
"Site auditors are accredited by the state government and, if satisfied that the reporting, remediation and validation processes have been carried out satisfactorily, issue a site audit statement which definitively states what the land can be used for and if any special conditions apply," the spokesman said.
He said based on the information provided to the council, the council was satisfied the site could be remediated.
Mr Brinkmeyer said following successful remediation, the first stage of development at the site would be 40 two-bedroom seniors housing units for those aged 55-plus.
The "gated community" would include an electronic gate system and fencing, as required by law for security, Mr Brinkmeyer said.
The second stage would be subject to rezoning of additional land.