Ronald owned property which he discovered was contaminated with hazardous waste.

Ronald owned property which he discovered was contaminated with hazardous waste. Ronald learned that 20 years earlier, Smith's Petrochemical had owned the property and had used the property as a disposal site for some of its manufacturing chemicals. Ronald also learned that Bennett Trucking has hauled the chemicals to the site under contract with Smith. Under these circumstances, which, if any, of the parties can be liable for the costs of cleaning up the site under CERCLA?