How long does it take to get to an Engineering V?

I am currently a sophomore in high school and i have been looking into different careers to try and pursue, and I really want to do something I like. I think the one that I would want to do is environmental engineering. I was checking the salary that the engineers make in average and I noticed there are different levels like and Environmental engineer I is an engineer that is fresh out of college. My question is how long does it take to go from an Engineer I to Engineer II and so on