Like many facilities across the country, a shortage of correctional officers has forced other staff members to do double duty.
FCI Mendota Union President Aaron McGlothin works in maintenance services.
He says 15 to 22 staff members per day are getting re-assigned to work in correctional officer posts.
"We have teachers, we have trade professionals, plumbers, general maintenance people... it's been a process that they have used across the country and they are over-relying upon it and it's not making our prisons much safer," he says.
Nearly one-third of federal correctional officer jobs in the United States are vacant.
The Bureau of Federal Prisons says everyone working at its facilities is a trained, sworn correctional worker. Employees are told when they are hired that they should expect to perform law enforcement functions.
"When you augment so many people away from their regular jobs, you are cutting down on the amount of staff available for an emergency response," says McGlothin.
Right now, FCI Mendota houses 961 inmates with 261 people on staff.
And the shortage in employees could soon become even more dire.
"It's not enough. We need more staff because they continuously open up brand new housing units with the influx of these inmates from the private prisons," said McGlothin.
Last week, McGlothin and other employees picketed outside the prison and were joined by Mendota Mayor Rolando Castro.
"Our tax money is in that facility and I want to make sure our employees are safe," says Castro.
According to the union, prison jobs start at around $40,000 with retention incentives.
Mayor Castro says the positions need to be more competitive.
FCI Mendota will hold a hiring event Wednesday and Thursday in hopes of providing relief for current staff.
McGlothin says he hopes to see support from state and congressional lawmakers for even more funding to add prison jobs.
Action News reached out to prison officials, who have not yet provided a comment.