Theme: 03. Green and Sustainable Remediation

Topic Area: 3c. Climate Resilience and Site Remediation

Formatted Title:

From Global to Local: Using Models for Climate Risk Screening and Resilient Remediation

Background/Objectives:

At least 126,000 contaminated sites in the US have residual contamination at levels preventing them from reaching regulatory closure. Approximately 12,000 of the sites will likely not achieve complete restoration in less than 100 years. In these cases, long-term or even perpetual management will be necessary. In 2019, the U.S. Government Accountability Office published a report indicating that 60% of environmental cleanup sites are in areas that may be impacted by flooding, storm surge, wildfires, and/or sea-level rise. Recently, the U.S. Environmental Protection Agency (EPA) has been explicitly requesting assessment of the vulnerability of the protectiveness of remedies to the effects of climate change and evaluation of measures to make remedies more resilient based on forward-looking climate data. Examples from existing projects demonstrate the value of resilient remediation, how global-scale models are downscaled and linked to local-scale models, and how modeled simulations can be used to predict the impact of climate change on remediation.

Approach/Activities:

Modeled outputs from case studies demonstrate the value of resilient remediation of contaminated sites. Our first case demonstrates the applicability of simulating different recharge scenarios from climate projection models perturbing the infiltration rate in the site groundwater model of a site with a pump and treat remedy. The comparison from the base case indicates the change in the flow field and hydraulic containment in the future, indicating the need for additional extraction. A second example is from a large remediation site, where the groundwater is discharged to a gaining stream. The modeling results show an increase in the contaminant mass loading to the stream, with predicted drought conditions in the future.

Results/Lessons Learned:

Contaminated sites are widespread, and, along with all facilities operating on decadal or indefinite timescales, are vulnerable to the effects of climate change. In the near term, States and local authorities may drive the adoption of resilient remedies, but we have seen the EPA explicitly requiring climate change vulnerability assessments and evaluation of resiliency measures. Most notably, we find these requirements more routinely demanded on sites regulated under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). Tools are available to assess vulnerability down to the facility scale from simple climate screening to more detailed analysis which can support adaptation planning. The project examples show the benefit of linking downscaled global climate models to local-scale models for the benefit of remedy design and adaptive site management. Specifically, these cases show that climate change effects the direction and magnitude of contaminated groundwater flow and can reduce the effectiveness of pump and treat remedies.

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Christopher Ritchie