What did the risk assessments find?

EPA completed the risk assessments and found the following:

• OU1 does not pose a human health or ecological risk concern.
• OU2 has  unacceptable risks for hypothetical future residents and commercial/industrial workers exposed to surface soil and groundwater used as drinking water under an unrestricted land use scenario. Risks are primarily driven by exposure to COPCs in groundwater. 
• OU3 has unacceptable risks to hypothetical future residents consuming the site groundwater as drinking water. 
• Baseline Ecological Risk Assessments for OU2 and OU3 found potential exposure to manganese to be the primary risk driver for fish and aquatic receptors in the Clark Fork River. Mercury may also pose a risk to small home range receptors, like mice and robins. Mercury may also pose a low to moderate risk to larger terrestrial receptors, like grouse and deer.