Work on reclaiming land at a smokeless fuel site once described as the "dirtiest factory in Europe" has begun in south Wales.
Up to 100 lorries will take waste from the site
The Phurnacite plant at Abercwmboi in the Cynon Valley, which once employed over 1,000 people, closed more than 15 years ago.
Residents have waged a campaign over many years to get the remains of the site cleaned up.
The £12m project is one of the biggest reclamation schemes ever in Wales.
The plant produced smokeless fuel briquettes which caused a big environmental problem because of its by-products.
Despite the length of time since the factory closed, the site is still contaminated by hazardous waste.
The site employed over 1,000 people in its heyday
Up to 100 lorries a day are taking the waste away to a special disposal site. Earlier plans to use trains failed to be realised.
Steve Smith, head of land reclamation at the Welsh Development Agency, said: "This is one of the most significant reclamation schemes currently underway in Wales.
"The removal of over 100,000 tonnes of contaminated waste which sits on a site extending to over 140 acres is a very large project."
Campaigners claim millions of pounds could have been saved if work had started earlier.
Former Phurnacite worker Malcolm Cook told BBC Wales: "When we could have removed it for approximately £3.5m to £6m, that has now gone up to £12.5m.
"Most importantly, they have only estimated that there are 122,000 tonnes to be removed. We as former workers are not convinced of that amount."
Five years ago, ex-workers who claimed they had developed cancer and other serious illnesses were forced to drop their fight when legal aid was refused.
A link has never been proved between working at the plant and ill health.
However, 250 people have asked a specialist solicitor, Gareth Morgan, to investigate.
Mr Morgan, who instigated coal miners' compensation claims in Wales, has already commissioned research.
He said it showed a "clear connection" between the emissions given off at the site, which workers were exposed to, and certain cancers.
"We are now instructing experts to deal specifically with this plant and the problems that have arisen from it."
It is hoped the operation will create a prime development site.