Currently working for a three letter Gov't agency in their IT department and going on three years as system administrator.  I'm also work as the backup SAN administrator, and manage all of the hardware for various server rooms that we operate across our campus and whatever else comes down the pipe.  

I'm starting to notice that my most of co-workers do the bare minimum and get by.  While on the other hand, I'm swamped with work from the time I come in till the time I leave.  Its typically my manager that passes this work onto me, as I know in his head, that he knows, that if the work gets put on my desk, it will get done correctly.  However, this is affecting me from getting other work done, like important projects done for other folks and departments.  My manager has commented on this or that work isn't getting done and its because I'm getting work from him because either other employees let the work slip thru the cracks or don't do the work correctly the 1st time and I have to do the re-work.  

I've also looked back on my career so far and this seems to continue to happen to me.  I grew up in a smaller rural environment so in my mind, my work ethic is pretty good.  

I've brought this up to my manager that we have, for example, a contractor, who either spends most of their time surfing social media websites, socializing with others, or generally screwing around.  I've said that I wanted to pass off some of my work to this contractor.  My manager responded that this would be tough as the contract would have to be re-written.  My response was that I could help with the re-writing of the contract, however it never seems to go any further then that conversation.  

So to sum it up, how do I stop getting all of this extra work from being dumped on me, so I can focus on what I was hired for, system administration?