A contaminant transport model is a work-in-progress hypothesis. Contaminant transport models are useful because they simplify reality for the purpose of predicting outcomes. In environmental litigation, contaminant transport models are used to confirm or challenge the allegation that a contaminant release occurred at a discrete point in time based on the observed presence of a contaminant some distance from the source. This opinion is usually based on knowledge of the location of the release, chemical test results, and a contaminant transport model.