A more thorough explanation:

The Comprehensive Environmental Response, Compensation and Liability Act, also known as CERCLA or "Superfund," is a law that aims to clean up sites contaminated with hazardous waste and prevent future contamination by assigning liability to parties involved. The Environmental Protection Agency (EPA) enforces CERCLA.

Under CERCLA, the federal government can take two types of actions:

• Removal Actions: Short-term actions taken to address releases or threatened releases that require a prompt response.
• Remedial Actions: Long-term actions taken to permanently and significantly reduce the risk of release of hazardous substances. These actions may only be taken at places on the National Priorities List (NPL).

CERCLA casts a wide net in bringing in responsible parties. The law allows for enforcement when there may be an imminent and substantial endangerment to the public health or welfare or the environment because of an actual or threatened release of a hazardous substance from a facility. Potentially responsible parties (PRP) include:

• Current Owners/Operators
• Past Owner/Operator at the time the pollution occurred
• Arrangers (person who arranged for disposal of a hazardous substance at a site)
• Transporters (person who transported a hazardous substance to the site)

Although CERCLA imposes strict liability and joint and several liabilities, there are limited defenses available to avoid CERCLA liability. These include:

• An act of God/an act of War
• Third-party defense
• Innocent Landowners
• De minimis settlements
• Separate Harm
• Contiguous Properties

A brownfield is a property whose use "may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant." CERCLA created a provision to protect developers and encourage them to clean up brownfields. The statute prevents liability being assigned to a bona fide prospective purchaser, so long as the purchaser does not impede the performance of either a response action or natural resource restoration.