Research Capabilities
Performance Assessment
PNNL staff in the Environmental Systems group conducted research that resulted in several approaches and tools for conducting performance assessments for remediation technologies involving contaminant extraction from the subsurface via a carrier fluid and for contaminant migration through the vadose zone. Brief summaries of these related research areas are given below. Links to pages containing more details, associated software, and relevant documentation are provided. Training videos are available from the websites below for the P&T and SVE performance assessment guidance.
Pump-and-Treat Performance Assessment
A structured approach has been developed for assessing pump-and-treat (P&T) performance to support a decision to optimize, transition away from, or close a P&T remedy. An updated conceptual site model frames the site in terms of specific decision elements, which are applied in a decision logic framework to facilitate selection of an appropriate outcome. Case studies are presented to illustrate each potential type of outcome.
Soil Vapor Extraction System Guidance
A stepwise approach was developed for gathering information and performing evaluations to support soil vapor extraction (SVE) remedy decisions related to groundwater protection to determine whether the system should be optimized, terminated, or transitioned to another technology (to replace or augment SVE). A decision logic approach is used to address remedy decisions based on an updated conceptual site model, the regulatory context, and an estimate of the impact that the remaining vadose zone source has on groundwater concentrations. The SVEET calculational tool is included to facilitate the evaluation process.
Vapor Intrusion Estimation Tool for Unsaturated-Zone Contaminant Sources
For some sites, assessment of SVE performance will include evaluation of vapor intrusion into buildings and quantification of the amount of source remediation necessary to meet vapor intrusion protection goals. An approach was developed to estimate vapor intrusion into buildings that is the result of contaminant diffusion from unsaturated-zone contaminant sources (vapors arising solely from groundwater plumes are not addressed). The calculational steps of this approach are incorporated into the VIETUS calculational tool.
Vadose Zone Performance Assessment for Inorganic Aqueous Waste Disposal Sites
A structured approach using a mass-flux based framework was developed to evaluate transport and attenuation of contaminants through the vadose zone. Numerical simulation results provide quantitative information for estimating future contaminant flux to the groundwater based on site-specific conditions. The approach also provides guidance for conducting and presenting the evaluation of vadose zone contaminant transport in the context of the EPA protocols for evaluating Monitored Natural Attenuation. Collectively, the assessment elements provide an effective approach for conducting an evaluation to support remedy decisions.