Definitions for "BACKGROUND LEVEL"
The concentration of a substance in air, water, or soil that occurs naturally or is the result of human activities not related to a hazardous waste site; conditions in the area near, but not affected by, a hazardous waste site. "Background samples" are often taken to compare an area's natural or pre-existing conditions to conditions at a hazardous waste site.
The concentration of a hazardous substance that provides a defensible reference point with which to evaluate whether or not a release from the site has occurred. The background level should be reflective of the concentration of the hazardous substance in the medium of concern for the environmental setting on or near a site. Background level does not necessarily represent pre - release conditions, nor conditions in the absence of influence from source(s) at the site. Background level may or may not be less than the detection limit, but if it is greater than the detection limit, it should account for variability in local concentrations. Background level need not be established by chemical analysis.
Levels representing the chemical, physical, and biological conditions that would result from natural geomorphological processes such as weathering or dissolution.