RALEIGH — The state of North Carolina and the federal government signed an agreement Thursday that could move thousands of residents in adult care homes with serious mental illness into community housing and avoids potential costly litigation.

But there’s still a high price tag for the state to carry out a plan rolled out last month by state health officials: possibly $287 million over eight years. An independent evaluator will examine whether the blueprint will keep pressure upon the state to comply with the plan.

U.S. Department of Justice attorneys had threatened a lawsuit in July 2011 because they said thousands of people with mental illness were segregated from society in adult care homes. Many had been released from state psychiatric hospitals and lacked access to community treatment.

The agreement signed by state Health and Human Services acting Secretary Al Delia and federal attorneys says by mid-2020 the state will provide affordable housing for 3,000 slots for people who otherwise would be living in adult care homes or mental hospitals. At least 100 slots will be available by next July, the agreement said.

No one will be forced to move from an adult care home to the community, although the agreement requires proof residents are making informed choices.

“North Carolinians who have a serious mental illness have a right to choose the very best care environment to meet their personal needs,” Delia said in a news release. “That choice — whether they live in the community or in an adult care home — will be supported with access to mental health and other support services that will be available in part due to this agreement.”

The U.S. Department of Justice said the agreement would “transform the state’s system for serving people with mental illness” and will ensure compliance with the Americans with Disabilities Act in light of a court ruling that gives the mentally ill the right to live in the least restrictive settings.

The agreement gives people who move access to community-based mental health services and directs the state to help them find employment, with the program’s scope growing incrementally to 2,500 people by mid-2019.

The two sides named former Massachusetts state mental health commissioner Marylou Sudders to evaluate independently how the state is matching up to the agreement and where it falls short. The state and federal governments would then attempt to fix the problems, but the agreement ultimately could be canceled without resolution — opening the door again for litigation.

Delia’s agency unveiled its plan to address the complaint in late July before negotiations were finalized and knowledge whether DOJ would accept it or sue. State health regulators didn’t want a judge or court officer to monitor the plan for fear the state would have little control or flexibility, instead offering the idea of an independent evaluator.

The 2011 complaint followed accusations by the group Disability Rights North Carolina in 2010.

Group executive director Vicki Smith was quoted in the state HHS news release saying Delia and Democratic Gov. Beverly Perdue “have not only done the right thing to protect the rights of people with disabilities, they have helped the state avoid costly litigation and destabilizing uncertainty.”

An association representing adult care homes lobbied Perdue against entering into any agreement they argued would force residents out of the homes. Some homes that depend on government funds to house and care for these residents could go out of business, said Janet Schanzenbach, executive director of the N.C. Association (of) Long Term Care Facilities, whose members house about 16,000 residents.

“We do agree that there needs to be additional housing choices for people with mental illness. We don’t feel that signing this agreement is the best way to get it done,” Schanzenbach said. She said Sudders’ role is still too powerful and the agreement’s requirement that the state reach out to adult care home residents at least quarterly to see if they’re interested in moving is overkill.

The first year of the project will cost $10.3 million, reaching up to $67 million in the agreement’s final year, Delia’s office said. The General Assembly set aside money in this year’s budget to begin the transition.

“We hope the U.S. Department of Justice will be a good partner in this agreement and give our state enough discretion to do what is best for all North Carolinians,” said Senate leader Phil Berger, R-Rockingham. House Speaker Thom Tillis, R-Mecklenburg, said lawmakers already are working to stabilize the state’s mental health system and blamed what he labeled the “Obama Justice Department” for leveraging “extreme interpretations of court cases” to require hundreds of millions of dollars be spent.

The agreement addresses one of a series of issues involving North Carolina’s adult care homes, whose residents include people with chronic health problems, Alzheimer’s disease or mental illness. The state is currently computing how many homes can no longer qualify for Medicaid funds because so many in them are considered mentally ill. Thousands of residents also could no longer qualify for personal care services as the program is being reworked.