Soil Vapor Extraction System Guidance
Soil vapor extraction (SVE), a prevalent remediation approach for volatile contaminants in the vadose zone, may exhibit a diminishing rate of contaminant extraction over time due to diminishing contaminant mass and/or slow rates of removal for contamination in low-permeability zones. Upon indications of a diminished contaminant removal rate, SVE performance needs to be evaluated to determine whether the system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. The guidance presented in the SVE System Optimization, Transition, and Closure Guidance report (PNNL-21843; available below) specifically addresses the elements of this type of performance assessment. A stepwise approach is presented for gathering information and performing evaluations to support SVE remedy decisions. Steps include revisiting the conceptual site model, considering relevant information, quantifying the impact of remaining vadose zone contaminant sources on groundwater, and integrating the assessment outcomes into a decision logic approach to address optimization, transition, and closure decisions. This material highlights relatively recent advances in use of mass flux/discharge approaches and includes a calculational tool to facilitate the evaluation process.
The Soil Vapor Extraction Endstate Tool (SVEET) is a spreadsheet tool that provides a convenient method for the user to apply the calculational procedures described in Appendix C of the PNNL-21843 report for estimating the impact of remaining vadose zone contaminant sources on groundwater concentrations. SVEET allows the user to easily enter information and see the estimated groundwater concentration results that are calculated for one or more scenarios conforming to the generalized conceptual model, which is described in the report. Appendix C of the report also walks through an example calculation and Appendix D provides details about the SVEET software, including system requirements, installation, the user interface, and application of the software. In situations where vapor intrusion is a potential concern, the VIETUS software provides a parallel approach to estimating the impacts of a vadose zone source on soil gas concentrations and vapor intrusion into a building.
SVEET is in the process of being updated as part of the ESTCP project ER-201731 (Development of a Decision Support Tool for Vadose Zone Remediation of Volatile Contaminants). This project will update the SVEET software to permit an expanded range of input parameter values, thereby enhancing the applicability of the tool for DoD and other sites. Software revisions and field demonstrations will take place in 2018 and 2019. DoD remedial project managers interested in applying the SVEET software as part of this ESTCP project should contact us for more information.
- New Version targeted for October 2019
- SVEET Software v. 1.x
- SVE System Optimization, Transition, and Closure Guidance (PNNL‑21843)
- Flow Charts for the SVE Guidance