Planning is underway to rehabilitate the former Shortland tip site where hundreds of tonnes of debris from the Newcastle earthquake were buried.
It was originally estimated the project would cost about $20million, however, this has increased to about $30million due to the project's complexity and scale.
City of Newcastle will put the project out to tender in the near future.
The 37 hectare Astra site was the Lower Hunter's main landfill between 1974 and 1995. It is estimated about 3 million tonnes of waste was buried at depths of up to five metres.
In addition, tonnes of building rubble, some of which contained asbestos, was trucked to the site on a daily basis in the months following the 1989 earthquake.
There have been long-standing fears about the potential for toxins to leach from the site into the adjoining Hunter Wetlands.
City of Newcastle acting director of infrastructure and property Joanne Rigby said the council had been working with the EPA on a plan to remediate the site and protect the nearby environment.
"City of Newcastle is committed to ensuring historic sites like Astra Street are not forgotten and we work closely with the EPA to ensure they're adhering to modern environmental management standards," she said.
"We have completed our preliminary investigations and finalised two detailed designs, which will improve the 20-year-old capping and drainage on the site."
Recent design work has resulted in an updated cost estimate for the project.
"Following further assessments of the site, the cost of the remediation work is expected to significantly increase on initial estimates, which will need to be factored into the 2021 Budget," Ms Rigby said.
The council will invite tenders from five companies identified during an expression of interest process to carry out the construction of enhanced environmental safeguards.
Work is due to get underway next year.
It will include final capping and reprofiling, drainage improvements to aid in management of surface water and sediment runoff, followed by revegetation and landscaping.
"These works will allow City of Newcastle to help protect and maintain the local environment well into the future, safeguarding the water quality of surrounding wetlands and aquatic ecosystems, increasing biodiversity values and promoting long-term native vegetation growth."
''The job needs to be done properly. It's not good enough to have this sitting next to an internationally recognised wetland,'' he said.
