Groundwater Cleanup Flexibilities
At most sites, the groundwater cleanup approach may incorporate one or more flexible provisions that are found in existing Superfund laws, regulations, policy and guidance. The four provisions described below may be selected and adjusted to meet site-specific conditions and remedial needs. A phased approach to the selection and implementation of groundwater remedies and a groundwater completion strategy both allow a remedial approach to be flexible as remedy effectiveness is evaluated and site conditions change. If a remedy is not achieving cleanup objectives, an effective phased approach and completion strategy will lead to reconsideration of the remedial approach and, if appropriate, the use of one or more flexible provisions.
Monitored Natural Attenuation
Depending on site conditions and cleanup goals, response actions may include “active” treatment or “less active” approaches. For certain sites, monitored natural attenuation, which relies on natural processes that decrease or attenuate soil and groundwater contaminant concentrations, may be used to complement or as an alternative to pump-and-treat or other active technologies.
EPA recognizes that it may not be possible to restore groundwater to its designated beneficial use in some cases. In situations where, from an engineering perspective, it is not possible to restore all or part of a groundwater plume, EPA may waive applicable or relevant and appropriate requirements (ARARs) and establish alternative, protective remedial strategies.
Designated beneficial use
How current and future use of groundwater are determined may be based on EPA designation or designation by state or tribal authorities. EPA recognizes the central role of the states and tribes in making groundwater protection decisions; if a state has an EPA approved Comprehensive State Groundwater Protection Plan or other codified groundwater standards that meet the regulatory criteria, those are the standards that will drive the groundwater cleanup.
Remediation should be completed as expeditiously as possible; however, the time required for remediation may be extended based on site-specific conditions, future use, remediation approach and technology and other factors.
Phased cleanup approach
Site response activities are implemented in a sequence of steps, or phases, such that information gained from earlier phases is used to refine subsequent investigations, objectives, or actions. Phased remedy approaches may include the implementation of early and interim actions. A phased approached may be most appropriate with varied degrees of contamination over the area of the site.
A completion strategy is a tool to help assess whether the remedial action is working as anticipated. and helps focus resources on gathering the most relevant data and other information to inform decision-making on the given remedy’s future steps. The strategy has three key elements:
- Understanding the site conditions and developing a site conceptual model
- Designing site-specific remedy evaluations
- Developing performance metrics and collecting monitoring data