Industrial activities that occurred prior to UC ownership led to the majority of contamination found at the RFS. The three main pollutant sources were:
- The California Cap Company (the former site owner), which manufactured mercury fulminate for blasting caps from the 1870s to 1940s on what is now the RFS property.
- Stauffer Chemical Company, acquired by Zeneca Inc., which operated on property adjacent to the RFS from 1919-1962. Stauffer Chemical manufactured sulfuric acid, pesticides and other chemicals. This neighboring property is now owned by Cherokee-Simeon Ventures, LLC, also known as "CSV."
- An unknown source of polychlorinated biphenyls (PCBs)