Federal and state regulatory agencies are continually assessing what chemicals or compounds warrant regulation when present in the environment. These assessments regularly result in adding new, previously unregulated, chemicals to the various lists of regulated substances. Because this evaluation tends to be a long process that involves input from multiple stakeholders (i.e., regulators, scientists, the public, etc.), the chemicals being evaluated for potential regulation or those recently regulated are commonly referred to as emerging contaminants. These contaminants are often not new compounds; in many instances, they have been developed, manufactured, sold, and discharged over periods of many years or even decades. Ergo, planning and predicting environmental monitoring costs associated with the future regulation of such emerging, often not well-understood, chemicals is no exact science and non-static. Add in other variables, such as changing, non-compatible, or obsolete remedial and treatment technologies, certainty and predictability become even murkier. Due to these factors, regulators and/or responsible parties may identify that environmental monitoring and remedial mechanisms that had previously been deemed acceptable to protect public health from old contaminants may be entirely inadequate to protect against emerging contaminants. This results in a regulatory mandate to rewind and re-evaluate the regulatory process, and the adequacy of the environmental monitoring and remedial mechanisms previously approved by a regulatory agency for implementation at a site. These topics are often not easily understood or predictable. So, therein lies the purpose of this article: to provide some information that is important to ponder if you are a responsible or interested party behooved to plan for these contingencies.