Approval for the extension of a Co Tyrone goldmine was based on inaccurate maps, it was claimed on Thursday.
Local man William Donnelly alleged that more than 20 hectares of the site at Cavanacaw, near Omagh were never properly assessed.
Mr Donnelly is seeking to overturn a failed legal bid to stop underground work at the operation.
Judgment was reserved following submissions at the Court of Appeal in Belfast.
Mining has been carried out at the site by Omagh Minerals, a subsidiary of Canadian firm Galantas Gold Corporation.
In 2015 the then Department for the Environment Minister, Mark H Durkan, gave the green light to the extended project.
Planning permission was granted for underground work at the existing mine on the basis of compliance with strict environmental conditions.
At the time Mr Durkan said these would include progressive restoration of the above ground site to ensure the protection and enhancement of habitat over time.
But Mr Donnelly claimed there was an unauthorised removal of large quantities of rock.
Part of his case centred on the environmental impact and possible acidity of this waste rock.
Points were also raised about the size of the site being either 60 hectares or 81 hectares.
According to Mr Donnelly that raised the possibility that the Minister was “misinformed or even confused as to the scale of the project being approved”.
Lawyers for the Department countered by insisting work was already covered by previous planning approval obtained more than 20 years ago.
No regulations were breached during the decision-making process, they argued.
In September last year a High Court judge dismissed Mr Donnelly’s challenge against the Minister’s decision.
He appealed that verdict in a fresh attempt to have the approval quashed and a new planning process undertaken.
Issues were raised about the application being for 60 hectares, while maps and drawings submitted as part of the process allegedly covered an 81 hectare area.
Following arguments Lord Chief Justice Sir Declan Morgan pledged to deliver judgment as soon as possible.
Outside court Mr Donnelly, who runs a bed and breakfast business in the area of the mine, said: “The ground for challenges was that the Department approved inaccurate drawings.
“Twenty-one hectares shouldn’t have been approved, they were never properly assessed.”