SPRINGFIELD — With the sale of the Thomson Correctional Center to the federal government no longer appearing to be an “if,” the question of “when” took center stage Tuesday.

In a background briefing with reporters, senior White House officials offered no specific date for when the first federal prisoners or detainees will arrive at the northwestern Illinois lockup.

But there are a number of steps that must first be taken that indicate it could be several months before the facility is up and running.

Following are some of the issues facing state and federal officials as they move toward transforming the mostly unused state prison into a federal facility dedicated to housing terrorist detainees and other maximum-security federal inmates.

The sale

Illinois Gov. Pat Quinn says the state will need to get three appraisals in order to set a sale price for the property, which has seen an investment of state dollars exceeding $170 million. The prison would be sold to the Federal Bureau of Prisons, which would then lease part of the prison to the Department of Defense.

Construction work

Security at the facility also must be upgraded. The property currently is enclosed by an exterior 12-foot fence. There also is a 15-foot interior fence with a dual-sided electric stun fence.

Federal officials want to lock it down even more.

“It would add additional upgrades to those,” a senior White House official told reporters Tuesday.

Interior changes also are anticipated, because terrorist detainees will not be housed with regular inmates.

“It’s really an amazing facility,” the White House official said.

Outside the walls

A letter outlining the purchase notes that federal departments and agencies, including the departments of Homeland Security, Justice and Defense, will work with state and local law enforcement authorities to identify and mitigate risks. Federal officials also have consulted with local, county and state law enforcement authorities to begin the process of identifying additional resources they may require to handle the increased population of federal inmates and detainees.

The Quinn administration had no immediate comment on whether roads in the region will be upgraded.

Congress and the General Assembly

Although its not clear whether lawmakers can do anything to block the sale from proceeding, state and federal legislators will have a voice in the process.

On Dec. 22, a special panel of the Illinois General Assembly will hold a hearing to discuss the closure of Thomson. The members could vote that day whether to support or oppose Quinn’s proposal. But the panel’s decision is not binding on the governor.

Congress also will likely get in on the act when the administration asks for money to buy the prison or seeks changes in federal law regarding the transfer of detainees to the U.S.

Among those expecting the issue to be discussed in the nation’s capitol is U.S. Rep. Phil Hare, D-Ill.

“Language was passed earlier this year that said federal funds could not be used to house detainees on U.S. soil. That would have to be amended,” Hare said Tuesday.

‘Many steps’ left to be taken

While no one was offering concrete estimates Tuesday, White House officials were stressing they want to move forward in a “timely, secure and lawful manner.”

A letter to Quinn from top federal officials, including Secretary of State Hillary Clinton and Attorney General Eric Holder, acknowledged the process could take a while.

“There are many steps still to be taken and many requirements still to be met, but we look forward to working with you to complete the federal acquisition of the facility in Thomson,” the letter noted.