Work is continuing at Welbeck Landfill Site, where managers say they are developing a public park.
FCC Environment, who run the site, recently applied for planning permission to carry on the scheme for another eight years.
The original project should have been completed in 2008, but this was then extended by another 10 years.
The company's permission to operate at Welbeck ran out on Saturday, 19 May. The site's future is expected to be decided at a planning meeting in either June or July.
Regardless of this, work has carried on at the site.
In a statement, FCC said: "The development will continue to provide a residual waste disposal facility whilst restoring a former colliery spoil tip.
"Restoration of the site will provide significant benefits to the local landscape character, including visual improvement, recreation opportunities and biodiversity gains."
Asked if work was continuing at the site now, a spokeswoman said: “We have continued to liaise closely with the planning authority during the process and anticipate continuing on site whilst the planning process continues, as it benefits all parties to continue with the restoration of this facility.”
Paul Dainton, president of Residents Against Toxic Waste (RATS) has objected to the scheme for all of its 20 year life.
He suggested that the extension of planning permission was a certainty.
He said: "It beggars belief how we've got ourselves into this situation.
"Everything I've said for the last 20 years about this has been proved correct.
"This suggests that they know they're going to get retrospective planning permission anyway. So what's the point in having a hearing?"