The main contaminants are the metals mercury, lead and copper from the California Cap Company operations.
Pyrite cinder waste (waste from sulfuric acid production) that includes an assortment of metals (arsenic, cadmium, copper, lead, mercury, selenium and zinc) and creates low pH (acid) conditions, was deposited by Stauffer Chemical Company in the early 1900s.
An isolated spot of PCB contamination was found at the outfall of the Western Storm Drain in Meeker Slough and was cleaned up in 2003, although detectable PCBS remain in some other locations at RFS.