BBCMerthyr Tydfil's Ffos-y-Fran mine was responsible for 86% of the UK's total coal output before it closedThe Welsh government will make the final decision about a controversial plan to restore the site of the UK's last opencast mine.
Merthyr South Wales Ltd (MSW) sparked anger after submitting a new - and cheaper - restoration plan, which would leave three coal tips in place.
It warned it had "insufficient funds" to deliver a far more extensive plan to restore the landscape, which had previously been agreed.
The government's move to "call in" the application means ministers rather than Merthyr Tydfil County Borough Council will decide the outcome.
The Welsh government said it would be "inappropriate to comment further at this time".
MSW has been asked to comment.
Under MSW's scaled-down proposals, it would seek to reduce the height of one coal tip and leave two others in place.
Chris and Alyson Austin, who live near the mine and have long campaigned against its continued operation, welcomed the Welsh government decision.
"We are really, really pleased," said Alyson.
"We've always felt the local authority lacked the capacity or resources to deal with a complex and controversial plan of this nature."
Chris and Alyson Austin have opposed Ffos y Fran for yearsChris said it would give them a "more objective view".
"This plan isn't like approving an extension on Mrs Jones' house, it's much wider. It's of national significance.
"The local authority's been too close to this for too long and it doesn't have the breadth of resources the Welsh government will have," he added.
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Given the go-ahead in 2005, the UK's largest opencast mine was officially classed as a "land reclamation scheme".
Part of the profits made from selling 11 million tonnes of coal over 15 years had to be used to clean up the site and return it to green hillside.
The tips contain 37 million cubic metres of material removed while the mine was operating.
Under the original proposals the tips would have been used to fill the main mining void - which is 175m (574ft) deep.
Estimates as to how much removing the tips and filling the void would cost vary, ranging from £50m to £175m.
GettyThe Ffos-y-Fran mine is about the size of about 400 football pitchesDaniel Therkelsen, campaigns manager at Coal Action Network, accused MSW of a "profit grab".
"The new proposal is to deliver a restoration on just £15m.
"That might sound like a lot but the promised restoration is budgeted to cost anywhere between £75 and £120m, so it's a tiny fraction of what would be needed to deliver the full restoration," he said.
"What we're talking about here is a very dangerous landscape.
"They talk about erecting fences to discourage people from going near the cliff edge, swimming in the void or going up and down with dirt bikes.
"We've seen in other opencast coal mine sites that have been under-restored, these measures haven't worked.
"We have trust that the Welsh government will see this application for what it is, which is an attempt to extract further profits from that area and abandon its obligations to restore the site."
A geotechnical report prepared for the council warned of a "significant risk of slope instability" from Ffos-y-Fran, while campaigners said plans to keep the tips in place are "staggering".
MSW said suggesting the "purpose-built, engineered structures" posed the same risks as historical coal tips was "incorrect and misleading".
The company's most recently published company accounts include provision of some £91.2m for meeting the requirements of the approved restoration scheme.
However a recent letter from the council to MSW noted that there now "appears to be a reliance" on the company using funds from a £15m account set up jointly with the council as a backup in case the firm went bust.
The mine's consultants responded, saying detailed costings "are currently being prepared".
The Welsh Conservatives accused the Welsh government of acting "far too late on Ffos-y-Fran" and said they were acting now because of the upcoming election.
A spokesperson said: "After years of failure, the priority now must be full, safe restoration with those responsible made to pay - not taxpayers picking up the bill."
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