RIVERSIDE, Calif. -

The Board of Supervisors today approved a contract with Banning to pay the city $450,000 a year to offset the expansion of a Riverside County jail there.

The contract would not become operative until the board formally approves a project to enlarge the Larry D. Smith Correctional Facility by 400-1,600 inmate beds.

A memorandum of understanding between the county and city has been in place since 2007 and will remain in effect until June 2018. The contract approved by the board today would be a continuation of the existing MOU, and annual payments from the new contract would begin in 2019, according to Supervisor Marion Ashley.

The contract stipulates that the city would be entitled to a 3 percent annual inflation adjustment to the county's base payments. It also notes that the city has promised to invest contract revenue into public safety.

The board is expected to move ahead, provided revenue is available, with a sweeping plan to expand countywide detention facilities -- and possibly add a new one -- to address worsening capacity constraints in the five jails.

At the current inmate growth rate, according to the sheriff's department, the county will need an additional 4,000 jail beds by 2020, or will be forced to step up the practice of turning some inmates out into the streets before they have completed their sentences in order to make room.

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 just under 4,000 beds available.

Supervisors are unanimous in the belief that Assembly Bill 109, the Public Safety Realignment Act of 2011, has exacerbated the county's jail overcrowding.

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.

According to the sheriff's department, 1,000 inmates housed in the county's jails are AB 109 prosecutions.