Environmental Restrictions on Recycling Center: How do I find them?

I have a friend that wants to open a metal recycling center. He is starting from scratch and has a lot of business experience and connections, but he does lack the information needed to find environmental restrictions/requirements. I have assured him that everybody on the SDMB be some smart’ns, and they could refer to the proper sites, books, etc…
Can anybody help?

The best starting place is going to be your (and presumably his) state’s environmental regulatory agency, which in Oklahoma looks to be the Oklahoma Department of Environmental Quality. They should be able to walk him through relevant state and federal requirements.

Thanks for the help. I didn’t even know where to start.