Three former lead paint manufacturers who lost a landmark lawsuit in Rhode Island would have to pay an estimated $2.4 billion to clean up hundreds of thousands of homes contaminated with lead under a state proposal released Friday.

The cleanup plan provides the most detailed roadmap to date for the mammoth undertaking of ridding Rhode Island homes of lead paint contamination. It would involve 10,000 workers and is projected to take four years. The state expected to file the plan in Superior Court later Friday, said a spokesman for Attorney General Patrick Lynch.