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Triad is a Federal/State Interagency Partnership

Operation and Maintenance

Application of the Triad approach to operation and maintenance activities associated with long-term remedial actions.

Within CERCLA terminology, operation and maintenance usually refer to activities associated with a long-term remedial action that has a life-span measured in years. Examples include pump-and-treat groundwater remediation systems, landfill caps, reactive subsurface barriers, vapor extraction systems, and long-term natural/enhanced bioremediation. For each of these, there is the operational need for ensuring that systems are performing as expected and determining as quickly as if possible problems are developing that require attention. There is also the CERCLA five year review requirement for sites with truly long-term remedial approaches.

These cases add another dimension to data collection: time. As discussed earlier, spatially sparse data sets often contribute the bulk of uncertainty to decision-making. The problem of insufficient sample numbers to support confident decision-making is compounded for monitoring programs over time. One of the key benefits of the Triad approach is the ability to bring a mix of measurement technologies to bear on sampling problems, allowing a much denser data collection program for the same sampling and analysis budget, which in turn means that better decisions will be made. As a simple example, a large number of monitoring wells might be screened with real-time measurement techniques for potential problems, and a subset of those selected for more definitive fixed-laboratory analyses where screening results were not conclusive, or pointed to unexpected conditions. Another example is the use of dedicated in situ depth-to-groundwater probes to monitor potentiometric surfaces for groundwater systems. These are capable of logging data every few minutes or hours (as compared to months or quarters for more traditional measurement approaches), and so can be used to flag situations where groundwater gradient changes might compromise the effectiveness of a passive system such as a subsurface reactive barrier.

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