Pros
Lots of opportunities for advancement if you are willing to move.
Cons
It usually isn’t the fault of the middle management, but the corporate philosophy is to do as much as possible with as little as possible. They work people as hard as they possibly can. Getting pay increases is extremely difficult - even when you get promoted. There is zero thought given to the long-term effects of burning people out, training people properly, having the resources to be able to do the work well. They will pile more stuff (often not related to your job) on as soon as they see you able to take a breath. And once you touch it, it is your responsibility forever. Honestly, it is an awful company to work for. There is a very good reason all quality people end up leaving. The reason there is so much opportunity for advancement is because the turnover is so high. But don’t plan on getting in, getting promoted, then moving to another company with the higher job title; Clean Harbors does such a poor job training people that the people who expect to take the knowledge they gain from working there and apply it to a new job at a different company often find themselves in over their head.