LOS ANGELES (CBSLA) – About 4,000 Kaiser Permanente workers in California began a five-day struck Monday amid union contract negotiations with the healthcare giant.

Mental health workers picket outside a Kaiser Permanente facility in Panorama City, Calif., on the first of a five-day strike. Dec. 16, 2019. (CBS2)

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The group made up of psychologists, therapists, psychiatric nurses and mental health clinicians walked off the job Monday from about 100 Kaiser Permanent hospitals and clinics up and down the state.

They are part of the National Union of Healthcare Workers (NUHW). They have been without a contract for over a year.

Their demands include higher pay, increased staffing, pensions for newly-hired employees and better overall retirement and health benefits.

“Kaiser clinics remain severely understaffed, patients are routinely forced to wait six-to-eight weeks for therapy appointments and clinicians are so overbooked that they have to work after hours trying to help patients who can’t wait for care,” NUHW said in a statement.

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Kaiser said that the union rejected a contract proposal from a neutral mediator.

“We have been jointly working with an external, neutral mediator to help us reach a collective bargaining agreement with the NUHW,” Kaiser said in a statement. “The mediator recently delivered a proposed compromise to both sides that we are seriously considering; however, the union has rejected it and announced plans to strike instead of working through the mediated process.”

The workers will be picketing outside facilities in Fontana, Anaheim and Panorama City all week.

Kaiser said its hospitals and clinics will remain fully open during the strike.

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In September, Kaiser reached a tentative agreement with more than 67,000 California workers on a new nationwide contract. The deal represented hundreds of different types of workers, ranging from optometrists, pharmacists and nurses to maintenance and service. Earlier that same month, dozens of Kaiser employees were arrested during a Labor Day protest outside the Kaiser Permanente L.A. Medical Center in East Hollywood.