bdarnell,
I can't think of any regulatory issues. Check NFPA 30, Flammable & Combustible Liquids code, for fire issues. Two thoughts though. First, contact your fire marshall and see if he has any issues with the configuration. Second, ask yourself the question "Will the failure of any one of these items be made worse by the presence of any of others?" If yes, you'll want to rethink the configuration.
Also, is this a hazardous watse facility (e.g. TSDF) or hazardous waste accumulation area?
MikeCJ