Legal Question in Real Estate Law in California

If you want a definitive answer, you need to consult with an environmental law specialist. I do not believe, however, that you are required to do anything other than make full disclosure of everything you know about potential hazmat contamination when selling a residential property (very different rules apply to commercial properties). As much as that may depress the value of the property, it may net out cheaper than a clean-up, because you would still have to disclose the contamination and clean-up, which would likely depress the value almost as much, and you would have spent the clean-up money.

I agree that selling with full disclosure of everything the heirs know is probably better than trying to take on remediation yourselves. Acquiring property by inheritance is probably the safest way to be, or have been, in the chain of title to contaminated property from the standpoint of personal liability under CERCLA.