Orange County supervisors approved a contract Tuesday to house federal immigration detainees at two county jails, a deal that will bring in more than $30 million a year and help save jobs in the Sheriff's Department.

The Sheriff's Department has been negotiating with U.S. Immigration and Customs Enforcement for months to house more than 800 detainees at the James A. Musick Facility near Irvine and the Theo Lacy Facility in Orange.

The jails could see the first influx of detainees as early as the first week of August. Sheriff Sandra Hutchens said the flow of detainees to the jails will be gradual - arriving in groups of a couple dozen -building up to a maximum of 838.

The jails have dorm-like facilities that Immigration and Customs Enforcement prefers for holding detainees, former inmates who have completed their sentence and have been transferred to federal custody pending resolution of their immigration status.

Often, the detainees are ultimately deported and those who are released - a prevailing concern for cities where the jails are located - will be transferred to federal institutions and released there.

Immigration and Customs Enforcement has no facility of its own in the greater Los Angeles/Orange County area and contracts with local jails to house detainees or sends them to other states. Both the Los Angeles County Sheriff's Department and Santa Ana Police Department jails house immigration detainees.

The five-year contract will bring in about $31 million for the current fiscal year and $35 million each for the next four years, at a daily rate of $118 per detainee. The Sheriff's Department will get $94.15 of that and the remaining $23.85 will go to the Orange County Health Care Agency, which will provide medical and mental health services.

The money will help the Sheriff's Department offset a projected $65-million budget shortfall next year and stave off additional cutbacks and layoffs.

"We did save jobs," Hutchens said after the meeting, but added that it was difficult to say how many.

As part of the contract, both jails will undergo some renovations for Immigration and Customs Enforcement staff office space. Space suitable for courtrooms will be found at Musick for deportation proceedings.

Orange County has more than 6,600 jail beds, the Sheriff's Department said, and more than 2,000 of them are empty.

Earlier this year, the Sheriff's Department released several hundred inmates before the completion of their sentences. At the time, critics accused Hutchens of timing the early releases to make room for federal detainees. The sheriff, though, said the releases were mandated by a new state law that recalculated how much of an inmate's sentence needs to be served.

Though the contract's approval is welcome news for the department's budget, it faces opposition from the city of Orange.

On Monday, that city's attorney sent a letter to county supervisors, saying the contract could violate a 1995 agreement that prevents Theo Lacy from being expanded, physically or operationally. The jail is in the middle of a sprawling county complex, across the street from the Block at Orange shopping center.

The city will take up the matter at next Tuesday's meeting.