Hundreds of Nassau County police officers are expected to retire before the beginning of 2016.

PBA President James Carver says roughly 250 members of the department are likely to retire in 2015, and another 150 will likely retire in 2016.

The department already has some of the lowest staffing levels since the 1950s.

The police union is raising a red flag about how those retirements could affect Nassau residents.

County Executive Ed Mangano says the county plans to hire 500 police officers by 2016 to replace retirees.

However, Carver says it will take time to fill the jobs. He says it takes six months for new officers to complete the academy and then get trained on the job.

Mangano said in a statement that the transition would "save taxpayers hundreds of millions of dollars" because the new officers will be subject to new labor contracts that require them to contribute to their health care and pensions.