The DEC said it had included the concerns of Dalyellup residents and the Shire of Capel when it issued a licence with tough conditions on Millennium.

Dalyellup campaigners are dismayed at the decision after they had fought for the past 10 months to close a site which holds toxic material including dioxins.

David Yeoman said he felt the community’s health concerns had not been seriously considered and believed the decision had been made to continue the site while the community consultation was still open.

Mr Yeoman said no-one who had raised concerns had been contacted by the DEC.

"The residents of Dalyellup at this time still remain unconvinced by DEC’s decision and will remain so unless they can prove otherwise," Mr Yeoman said.

DEC director of environmental regulation Alan Sands said he had been aware of the issues raised by nearby residents.

"Even though radiation levels and dioxins are at extremely low levels, they have been key concerns for the community," Mr Sands said.

He said the radiation levels at the boundary of the Dalyellup site are comparable with background levels for the Swan Coastal Plain and Darling Scarp areas.

"Testing at the site for dioxins and furans also indicates that nearby groundwater and soil samples are well below (standard levels)," he said.

Tough conditions imposed by the DEC on Millennium include ongoing monitoring of groundwater and radiation levels up to and beyond 2013.

Millennium’s South-West project manager Andy Males said the company welcomed the decision and it was recognition of an excellent safety record.

"We fully support the licence conditions for extensive monitoring of water and air quality so we can continue to assure the community that the site is safe."

Mr Males said more than 20 years of monitoring has demonstrated that the solid waste disposal site is safe for the community and the environment.