Improving Long-term Monitoring of Contaminated Groundwater at Sites where Attenuation-based Remedies are Deployed
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Improving Long-term Monitoring of Contaminated Groundwater at Sites where Attenuation-based Remedies are Deployed Miles E. Denham 1 Mark B. Amidon2 Haruko M. Wainwright3 Baptiste Dafflon3 Jonathan Ajo-Franklin3,4 Carol A. Eddy-Dilek2 ●
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Received: 18 March 2020 / Accepted: 5 October 2020 This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020
Abstract This study presents an effective approach to tackle the challenge of long-term monitoring of contaminated groundwater sites where remediation leaves residual contamination in the subsurface. Traditional long-term monitoring of contaminated groundwater sites focuses on measuring contaminant concentrations and is applicable to sites where contaminant mass is removed or degraded to a level below the regulatory standard. The traditional approach is less effective at sites where risk from metals or radionuclides continues to exist in the subsurface after remedial goals are achieved. We propose a long-term monitoring strategy for this type of waste site that focuses on measuring the hydrological and geochemical parameters that control attenuation or remobilization of contaminants while de-emphasizing contaminant-concentration measurements. We demonstrate how this approach would be more effective than traditional long-term monitoring, using a site in South Carolina, USA, where groundwater is contaminated by several radionuclides. A comprehensive enhanced attenuation remedy has been implemented at the site to minimize discharge of contamination to surface water. The immobilization of contaminants occurs in three locations by manipulation of hydrological and geochemical parameters, as well as by natural attenuation processes. Deployment of our proposed long-term monitoring strategy will combine subsurface and surface measurements using spectroscopic tools, geophysical tools, and sensors to monitor the parameters controlling contaminant attenuation. The advantage of this approach is that it will detect the potential for contaminant remobilization from engineered and natural attenuation zones, allowing potential adverse changes to be mitigated before contaminant attenuation is reversed. Keywords Groundwater Long-term monitoring Radionuclide contamination Remediation ●
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Introduction Post-closure long-term monitoring is required at waste sites where residual contamination is left in the subsurface to inform site owners and regulators of any unexpected contaminant behavior that could be a potential threat to human health and the environment. Sites with residual contamination are those where contaminant source zones have been contained but not eliminated, as well as those in which
* Miles E. Denham [email protected] 1
Panoramic Environmental Consulting, LLC, Aiken, SC, USA
2
Savannah River National Laboratory, Aiken, SC, USA
3
Lawrence Berkeley National Laboratory, Berkeley, CA, USA
4
Rice University, Houston, TX, USA
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remediation of contaminated gro
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