The DEQ has interpreted its regulatory definition of hazardous waste to extend to mixtures of hazardous wastes and environmental media (such as contaminated soil and groundwater). Media that are contaminated with listed or characteristically hazardous waste must be managed as hazardous waste until they no longer contain such wastes.

The DEQ has not issued any general rules as to when, or at what levels, environmental media contaminated with hazardous wastes are no longer considered to "contain" those hazardous wastes. Under this "contained-in policy" DEQ has the discretion to determine contaminant-specific health-based levels, such that if the concentrations of the hazardous waste constituents were below those levels the media would no longer be considered to contain the waste.

The health-based levels used in making contained-in determinations are established on a site-specific basis, in accordance with general State guidelines, or by means of a site specific risk assessment. The DEQ's contained-in policy is consistent and reflects EPA's long-standing "contained-in policy."