Remedial Design and Implementation

Benefits and application of the Triad approach to support remedial design and implementation.

The potential benefits of a Triad approach are greatest during remedial design and implementation:

• At this stage of the process, contaminants of concern and their associated cleanup goals should be well defined. This facilitates the selection of appropriate real-time and traditional measurement technologies.



• If a Triad approach has been consistently applied throughout the cleanup process, site-specific measurement technology performance information should be available from the remedial investigation. This simplifies regulatory acceptance and allows a data collection program to be designed with a high degree of confidence regarding its performance. An important point to remember is that even if a particular measurement technology does not have detection capababilities below cleanup standards, it may still play a valuable role in developing the CSM by identifying distinct populations within the site's boundaries (e.g., "hot spots" or small areas with significantly elevated contamination levels).



• Expected unit cleanup costs should be quantifiable. This allows a cost-benefit analysis to be performed that can balance the cost of additional investments in data collection either prior to or during remediation with the cost savings expected from improved remediation performance (e.g., more precise contaminated soil excavation).



• The level of sampling required to support the remedial action may be significant. This presents the opportunity for analytical savings by implementing data collection programs that mix cheaper alternative measurement techniques with more traditional fixed-laboratory techniques.



• The potential for waste minimization (with associated possibilities for cost savings) can be significant. The Triad provides waste minimization opportunities by supporting remedial actions that can be more precise in their implementation, focusing activities only on soils/sediments/groundwater that truly require it.



• There is the possibility for supporting alternative waste disposal decisions for various waste streams generated by remediation work. This presents the potential for cost-savings by having alternative disposal or treatment options available that are the most appropriate for the contaminants encountered as remediation work progresses.

A Triad approach can specifically support remedial design and implementation in a number of ways. Triad-based data collection programs can be used to "fill" data gaps in the CSM that adversely impact design. The issue is that remedial investigations rarely provide adequate information for proper remedial design. This should not be surprising, and does not necessarily reflect an inadequate RI effort. The ultimate remedy is usually not known when the RI is being conducted. The list of contaminants of concern is incomplete. Final cleanup goals have not been defined. The CSM will still be relatively immature at the outset of the RI. Even if a Triad approach is used to support the RI effort, there may still be a need to resolve design data needs once the preferred remedial alternative has been selected.

Primary among data gaps is uncertainty regarding the exact location and extent of soil, sediment or groundwater contamination as defined by cleanup goals for the site. This uncertainty can complicate the design process itself (e.g., determining excavation footprints or locating extraction/injection wells), and also introduce programmatic planning problems (e.g., accurately estimating expected remediation costs or schedules). With a properly formulated CSM that quantifies contamination location and extent uncertainty, Triad-based sampling programs can be designed to better define contamination footprints before remediation begins. Real-time measurement technologies deployed as part of a dynamic work strategy can chase contamination until extents are bounded. This, in turn, provides certainty that contamination volumes are bounded, or that subsurface source terms have been identified.

A Triad approach can also change the nature of remedial actions themselves. For example, building real-time data collection into a remedial design can allow the remedial action to evolve and adapt to site conditions as they are encountered. In the case of soil and sediment contamination where excavation or dredging is involved, data collection conducted as part of the remediation work can allow the segregation of contaminated media either in situ, or immediately after removal. When disposition costs are significant, the ability to segregate contaminated media based on contamination profiles can result in significant cost savings, and even support multiple alternative disposition or treatment options that are best suited to particular contamination profiles. For groundwater or vapor extraction and treatment systems that involve multiple injection/extraction points, monitoring system performance can be used to alter pumping/injection rates to optimize the cost effectiveness of the system over its life-cycle. A Triad-based remedial action will be designed to incorporate dynamic work strategies, facilitating changes in remedial activities in response to real-time data collection.

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