RIVERSIDE, Calif. -

Plans to expand Riverside County jail facilities to prevent large numbers of inmates from being returned to the streets because there's not enough space to keep them locked up will be on the Board of Supervisors' agenda today.

Supervisors Marion Ashley and Jeff Stone will be asking their colleagues to support a proposal titled "Incarcerate More Prisoners Responsibly In Satisfying Overwhelming Need," or IMPRISON.

The immediate goal is to expand the Larry D. Smith Correctional Facility in Banning by adding onto existing jail wings so there's room for an additional 400 to 1,600 inmate beds, according to the supervisors.

"The sheriff has identified, through his strategic plan, a need for an additional 4,000 jail beds by 2020 and a total of 13,500 by 2050," the supervisors wrote in their proposal. "It is imperative that the board develop a plan for short, medium and long-range capital projects to meet these needs and provide for the safety and security of our residents."

Ashley and Stone worried about the lack of sufficient correctional space to house recidivists contributing to current jail overcrowding -- a condition largely blamed on Assembly Bill 109, the Public Safety Realignment Act of 2011.

Under the law, so-called "non-serious, non-violent" offenders convicted of felonies that do not stem from a sex crime are to serve their sentences in local detention facilities. Proponents of realignment suggested that jail sentences would be capped at three years, but that has not held true. Some convicts in local facilities are serving terms in excess of 10 years.

AB 109 also made counties responsible for prosecuting and, often, incarcerating parole violators.

In 2012, the sheriff released nearly 7,000 "low-level" inmates early for lack of space. Under a two-decade-old federal court order, the county must have a bed for each detainee or let some of them go. They're known as federal "kickouts."

The county has a just under 4,000 beds available.

The IMPRISON proposal calls for the priority expansion of the Smith facility and advocates completion of the 1,250-bed expansion of the Indio Jail, or East County Detention Center. However, the supervisors also favored building out the Robert Presley Detention Center in downtown Riverside to facilitate adding another 900 beds.

The supervisors say there's also room to expand the Southwest Detention Center in Murrieta by around 2,000 beds.

Ashley and Stone did not leave out the controversial Mid-County Detention Center, or Hub Jail, as a possible solution to capacity constraints. On the recommendation of Supervisor John Benoit, the Hub Jail was knocked off the county's list of capital improvement priorities in 2011 in the face of what supervisors then agreed were prohibitive costs.

The $300 million facility was to be erected on a 200-acre site in Whitewater, just off Interstate 10, on the eastern approach to Palm Springs. The project would provide between 1,200 and 4,800 new inmate beds.

Coachella Valley tourism and hospitality interests widely opposed the concept, saying it would severely degrade the area's appeal.

"The county should continue to pursue the Mid-County Detention Center, completing all environmental and design work so that it is shelf-ready in the event state or federal grants become available in the future for new jail construction, separate and distinct from `jail expansion,"' Ashley and Stone said.

An IMPRISON companion proposal seeks board approval for renewal of a subvention agreement with the city of Banning to offset impacts stemming from enlargement of the Smith jail. The city would receive $450,000 a year, with an annual inflation adjustment of up to 3 percent..