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| Resource Library > Technology Transfer > Programs and Initiatives > Performance-Based Management > Exit Strategy |
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Exit Strategy
Restoration programs based on optimized, performance-based, remedial and monitoring processes have a high probability of success. However, the measure of "success" must be defined in terms of stakeholder approved performance-based metrics. A cleanup plan using decision logic should state how cleanup goals will be measured to demonstrate their attainment, and a completion plan can be used for this purpose. Completion plans should be updated whenever new information is available. Knowledge of the selected or imposed cleanup goals and the expected time of completion, however, is not sufficient to assure restoration success. The larger purpose of the completion plan is to identify all requirements that must be met, as measured through stakeholder approved performance-based metrics, to complete the restoration program. The completion plan in essence is an exit strategy.
An exit strategy should define the restoration goals and the methods that will be used to assess whether the goals are being attained. Project managers should develop an exit strategy in consensus with stakeholders. Ideally, an exit strategy should address the stakeholders concerns, meet all applicable regulations, identify all performance metrics, assess costs/risks/future use/benefits of the remedial actions and identify all requirements to terminate RA-O and LTM activities. If delisting or de-permitting is applicable, the exit strategy should describe the milestone(s) that will trigger initiation of delisting/de-permitting procedures, decommissioning of systems/wells and define its schedule.
Exit Strategy Definition
The exit strategy is a dynamic plan that addresses the approved restoration program goal(s) that are achievable in a reasonable time-frame based on future land-use, in accordance with the current conceptual site model (CSM). It must also determine the following:
- How performance of the restoration project(s) will be measured - the RIPS tool should be used to track performance
- Which decision logic will be used to select operational changes
- How attainment of cleanup goals will be demonstrated
- How system(s) operation and LTM will be terminated
- How site closeout, delisting or de-permitting will be performed
The restoration program goal(s) should be identified. Typical goals include the following:
- For an engineered cleanup - Physical removal, containment, ex situ or in situ
- For a passive restoration - LUCs and ICs, TI waiver
The Importance of the Conceptual Site Model (CSM)
It is impossible to make informed decisions based on an inaccurate conceptual site model (CSM). The CSM must be complete, up to date, and include the following three models:
- Hydrogeologic: Sufficient lithological and groundwater information should be collected to understand hydraulic conductivity, hydraulic gradient, and the directions of groundwater flow. Aquifers and aquitards should be identified. This information is essential for predicting plume dynamics.
- Risk Assessment: Realistic potential and completed pathways to receptors, based on current and future land use, must be identified and considered in the remedial design.
- Operational and Monitoring Performance: Consider biological, chemical, and physical site conditions that affect implementation of the selected technology, and measurement of its performance:
- Biological: Microbial activity at the site must be assessed to determine if biodegradation of the chemicals of concern is potentially practical, or if biological activity will hinder operation of the system(s). Natural attenuation parameters need to be measured to determine if site modifications would enhance natural attenuation
- Chemical: Groundwater geochemistry that could potentially impact performance of the remedial system(s) should be evaluated. Chemical properties and interactions of the chemicals of concern (COCs) with the site soils and GW solutes need to be defined. These include soil gas characteristics, and retardation factors due to adsorption or weak chemical bonding with soil particles and soil organic matter
- Physical: Effects of soil texture, organic matter content, temperature, moisture, porosity, cementation, and aeration on the remedial system performance should be evaluated.
An Exit Strategy Document Should Address the Following Topics:
- Performance-based Metrics: The CSM and the RAO will help define the metrics to be used in assessing the performance of the remedial action(s) and the monitoring program(s). For example, if the RAO of a pump-and-treat system is capture, piezometric measurements along a transient between the extraction wells would be effective in measuring capture. On the other hand, volume of water extracted by a pump-and-treat system is not an effective performance metric. Downgradient verification sampling for contaminants of concern is a secondary performance metric
- Decision logic: Because sites are generally heterogeneous and complex, the use of decision trees to manage operation, monitoring and closeout is highly recommended. Decisions trees should be dynamic as additional information becomes available during implementation, and deviations from predicted performance occur. These deviations should be reflected in refined decision trees, with the concurrence of stakeholders, and lead to modifications in the operation or monitoring.
- Cleanup Goal Attainment: The manner in which attainment of the restoration goals will be demonstrated should be clearly defined and understood, and should have the concurrence of all stakeholders prior to implementation of the remedial action. This process should identify the methodology and locations where the goals will be measured and the margin of error that will be permitted in these measurements .
- Termination: Termination of the RA-O should be defined in the operational decision tree. Once cleanup goals have been attained as defined above, the remedial action should be terminated as restoration complete.
As with the remedial action, LTM should be managed with the assistance of decision logic and decision trees. Sampling frequency should be consistent with groundwater velocity and retardation factors. If groundwater velocity is a few feet per year, an appropriate sampling frequency might be once per year or longer. However, if groundwater velocity is greater than 300 ft/yr and the retardation factor in minimum, monthly sampling frequency might be appropriate.
The decision tree should clearly identify under what conditions an analyte or a sampling location will be considered redundant. This decision tree should define the procedure by which redundant analytes and sampling locations will be eliminated.
- Site Closeout and property transfer of BRAC sites: The primary restoration goal is to return sites to safe and useful conditions. This condition may not be attainable at all sites and for those LUCs & ICs will be required.
The remedial action operation decision tree should identify under what conditions the cleanup goals will be considered as met, site closure documentation should then be submitted to the appropriate regulatory agencies and de-listing from the National Priority List or removal of the site's RCRA permit requested as applicable. This goal should be included in the schedule to complete.
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