Asbestos and traces of oil may have to be removed from a Liverpool open green space to make it fit for human habitation.
It's hoped that the former Festival Gardens site on the waterfront will eventually have up to 2,500 homes as part of a major regeneration plan.
But a recently published report reveals that some parts of the land, in Otterspool, contain harmful substances.
Liverpool council , which owns the site, had already said that work to clear the site could cost as much as £29m because the site was a major landfill between 1954 and 1981.
But an environmental impact scoping report, published as the council prepares to progress with cleaning up the site, warns that a failure to treat the soil could damage the health of people who would eventually live there.
The report says: "Based on the results of risk assessments undertaken to date the made ground soils (where natural and undisturbed soils have largely been replaced by man-made or artificial materials ) may pose a risk to the human health of future site users.
"The made ground has the potential to cause contamination of the groundwater beneath the site and surface waters adjacent to the site."
It goes on to say that the ground is 'shown to contain low concentrations of asbestos and concentrations of a number of metals and hydrocarbons'.
According to the report, further work will be carried out to figure out the best way to treat the land and decontaminate it.
The council received nearly £10m of funding from Homes England earlier this year to help towards the costs of preparing the site for the construction of homes.
The council has an ambitious plan for the area, hoping to preserve the Festival Gardens but building homes elsewhere on the festival site.
It wants to turn the land into a £700m "cultural garden suburb" including up to 2,500 homes and potentially a leisure attraction.
The authority bought the site in 2015 for £6m.
It had fallen into disrepair after being effectively abandoned in the years following the 1984 International Garden Festival.
