The federal environmental statutes are four different machines bolted to the same chassis, and the lawyer who treats them interchangeably will lose. This guide walks through each in turn: CERCLA's strict, retroactive, joint-and-several liability, its four classes of potentially responsible parties, the landowner defenses that only work if you did all appropriate inquiries first, and the sharp doctrinal line between Section 107 cost recovery and Section 113 contribution drawn by Cooper Industries and Atlantic Research; RCRA's forward-looking cradle-to-grave permitting regime and the imminent-hazard citizen suit that Meghrig confined to injunctive relief; the Clean Air Act's cascade from NAAQS to state implementation plans to New Source Review and Title V permits; and the Clean Water Act's Section 402 discharge permits, its Section 404 dredge-and-fill program, and the jurisdictional reset that Sackett v. EPA delivered to "waters of the United States." It closes with NEPA's purely procedural mandate, the standing rules that govern citizen suits after Lujan and Laidlaw, the administrative, civil, and criminal enforcement ladder including the responsible corporate officer doctrine, and how environmental liability travels through corporate and real estate transactions. A running hypothetical -- Ironwood Partners buying a shuttered metal-plating plant -- carries the doctrine from diligence through allocation. Statutes and cases are cited throughout, with explicit flags where the law is unsettled or moving fast.