Likelihood of Release

The likelihood of release factor category measures the likelihood that a hazardous substance has been or will be released to the environment. The likelihood of exposure factor category measures the likelihood that individuals will come directly into contact with hazardous substances.
Likelihood of release has the same structure in all three migration pathways.
Either an observed release is documented or the potential to release factors are evaluated.
An observed release is assigned the maximum value for likelihood of release (550 points).
An observed release can be documented either by "chemical analysis" of environmental samples or by "direct observation" of substances entering the ground water, surface water, or air.
If an observed release cannot be documented, then the potential to release factors are evaluated.
Potential to release is assigned a value of between 0 to 500 points.
Potential to release is generally evaluated based on the product of source characteristics and source containment factors.
- The source characteristics factors reflect the physical and environmental characteristics of the source and its location that influence the likelihood of release from the source in the absence of man-made barriers.
- The containment factors represent the physical characteristics of the man-made barriers at the source that lessen the likelihood of release.

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