Works to remove ground pollution on Dublin's Poolbeg Peninsula may be necessary to allow residential development according to the Environmental Protection Agency (EPA).
The EPA warned some years ago that because the area was once used for landfill it would not be suitable for houses with gardens.
The agency said housing units raised above a ventilated ground level would bring risks to acceptable levels.
The EPA carried out an inspection of the 10 hectare Irish Glass Bottle site in 2009, which is part of the 34 hectares in Poolbeg recently given fast-track planning approval with the potential for up to 3,000 homes.
At the time of the report, the former glass bottling site was found to be no longer a pollution risk of itself after the owners Beckbay removed two metres of soil matter.
But an inspectors report states that this was to remediate pollution from the bottling works and did not address the historic use of the site as a rubbish dump.
The report states that the issue of pollution would have to re-examined by the planning authority before planning permission for housing was granted.
The report noted that the Poolbeg peninsula is reclaimed land and was used as landfill for 30 years up to 1978.
Tests carried out on the Glass Bottle site found hydrocarbons and metals in the soil and levels in the groundwater were above those allowed for drinking water.
The tests also found methane gas emissions though these were low and had decreased over time.
Becbay were given a Integrated Pollution Control (IPC) licence to remediate the Irish Glass Bottle site and this was surrendered in 2009.
The EPA's report said it was possible that another waste licence would have to be issued before residential development.
The Irish Glass Bottle site was bought by Becbay for €412 million but is now under the control of NAMA and valued at around €50 million.
Housing has already been built on decontaminated land in Dublin's Docklands.The Bord Gail lands including Sir John Rogerson's Quay took fuve years to clean up at a reported cost of €40 million.