Which act introduced the "innocent landowner" defense that states that a landowner isn’t responsible for clean-up of contamination that occurred prior to their ownership, provided they have not tried to cover up the contamination and can prove due diligence in investigating the property when it was purchased?

Superfund Amendments and Reauthorization Act (SARA)

Explanation:

The Superfund Amendments and Reauthorization Act (SARA) of 1986 introduced the innocent landowner defense that states that a landowner is not responsible for clean up of contamination that occurred prior to their ownership provided they have not tried to cover up the contamination and can prove due diligence in investigating the property when it was purchased. The SARA act of 1986 amends the CERCLA act of 1980 which provides that every landowner or facility owner that has contaminants and hazardous materials should make it known to the public. It also provides that an innocent landowner who is not aware of the contaminants in his or her land prior to ownership is not liable for the clean-up.