What are operable units?

Sometimes, EPA divides larger sites into smaller pieces called “operable units.” This can help make site investigation and cleanup more efficient. At Smurfit-Stone Mill, there are three operable units. 

Operable Unit 1 is approximately 1,570 acres. It is and has historically been used largely for agricultural purposes, including cattle grazing and croplands. 

Operable Unit 2 covers about 255 acres and is the former core industrial footprint of the former mill site.
Operable Unit 3 spans over 1,700 acres and includes former wastewater treatment facilities consisting of a former clarifier and settling ponds, aeration basins, polishing ponds, treated water holding ponds, infiltration basins, and locations in the Clark Fork River where hazardous substances from the site have come to be located. Apart from occasional daylighting of the Clark Fork River, these holding ponds have been dry since operations at the former Mill ceased in 2010.