How to I create a login system for each tab on my site?

I am creating an intranet site for my town. At the main page I have tabs for the Police department, Fire department, Water and sewer department, Town Hall, and the Parks Department. I need a login for each tab on my site. For example if you are from the police department, when you log in you can’t see the fire department, water and sewer, Town Hall, or parks tab’s content. Any help is greatly appreciated.

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