A plan to boost staffing at the Fulton County jail would cost taxpayers up to $20 million over the next four years.

Sheriff Ted Jackson Wednesday said that's the tab to hire 339 new deputies and detention officers to address chronic staffing shortages at the Rice Street jail. The first new staffers would be hired next year, Jackson said.

Improving staffing is the last hurdle Fulton County must clear to end federal supervision at the jail, where overcrowding and poor conditions prompted a lawsuit that has dragged on for a decade.

Jackson said the extra staffing would make the jail safer and cut down on employee turnover that has made it difficult for the county to maintain proper staffing.

“It’s a major milestone that the sheriff’s office and the county sat down and almost completed,” the sheriff said.

Any new staffing would have to be approved by commissioners.

Jail inmates sued Fulton in federal court in 2004, citing dirty and dangerous conditions. The lawsuit described a short-staffed jail where inmates slept on the floor, plumbing and other basic systems didn't work and inmates and employees alike were assaulted.

The following year, the county agreed to make scores of improvements. But progress has been slow and county officials sometimes improved conditions only after a judge threatened to throw them in jail.

Still, county officials have completed most of the list at a cost of more than $200 million. Most recently they spent $4.8 million to replace faulty jail locks.

But chronic staffing shortages have proven difficult to address. Recently, U.S. District Judge Thomas Thrash ordered the county to provide a plan to address the problem. On Tuesday, they delivered that plan.

Jackson said he’s not sure how many new staffers will be hired in 2015 and at what cost. But under Jackson’s staffing plan the county would hire the 339 new employees over four years. Jackson estimated the total price tag at $20 million.

Southern Center for Human Rights, which filed the lawsuit on behalf of inmates, has said it would like to see Fulton comply with the court order for six months to a year before ending the litigation.

County Commission Chairman John Eaves said he needs more information on the staffing plan before he can comment.