Opening Remarks
 

1:05 - 1:25 p.m.

Commitment to Long-Term Stewardship:  An Overview of Scientific Processes and Technical Innovation to Ensure Safe and Resilient Management of Legacy Sites

Darina Castillo, U.S. Department of Energy, Office of Legacy Management

The production and testing of nuclear weapons and other peace-time energy research activities left a legacy of radioactive and chemical waste, contamination, and hazardous facilities and materials. The Department of Energy Office of Legacy Management’s (LM) mission is to protect human health and the environment at 103 sites located in 29 states, three Native American Reservations, and one U.S. territory, stretching from Amchitka Island in Alaska to Puerto Rico. LM’s portfolio requires long-term surveillance and maintenance (LTS&M) activities spanning potentially hundreds of years in diverse set of political, social, and environmental conditions. As such, LM is studying and applying new cost-effective technologies that improve worker and public safety and enhance protection of the environment.  

LM is focused on projects that address disposal cell cover performance, groundwater protection, and advanced technology applications. Specifically, LM has made strides in cells cover enhancements including evapotranspiration (ET) covers, understanding of subsurface erosion, groundwater modeling and monitoring, and advanced monitoring technologies, such as lysimeters and remote sensing. Examples of scientific enhancements include pilot studies that determined that vegetations can reduce percolation significantly and ultimately, providing substantial disposal cell performance benefits while reducing management costs and labor.  Additionally, remote sensing and a supercomputing platform to model and backcast ET at several western US sites informed the site's groundwater and contaminant transport models. These studies and their supporting technologies are also leading to alternative disposal cell designs and improved performance-evaluation methods and policies.

LM maintains partnerships to remain informed of emerging engineering and scientific advancements. LM-sponsored studies promote data sharing and scientific achievements by collaborating with other federal agencies, the environmental community, universities, national laboratories, and the international scientific community. These engagements provide LM the opportunity to share lessons learned and expertise in legacy sites and in LTS&M at all types of residually radioactively contaminated sites. LM’s investment in scientific studies and innovative technologies continues to advance the protection of human health and the environment.

Coauthor: Brian Peake (RSI EnTech, LLC)

1:25 - 1:45 p.m.

Sustainable Remediation in Washington State: Building Resiliency to Climate Change, Minimizing Environmental Impacts, and Maximizing Environmental Benefits

Chance Asher, Washington State Department of Ecology

This presentation will summarize Washington State’s efforts to increase the sustainability of cleanup remedies in the midst of dealing with climate change impacts. The state has over 11,000 contaminated sites―which include contaminated sediment, soil, and groundwater, failed landfills, mining sites, and leaking underground storage tanks (i.e., gas stations).

Washington State is vulnerable to many climate change impacts.  The state has over 28,000 miles of marine and freshwater shorelines, including the Pacific coast, Puget Sound (the third largest estuary in the United States) and the Columbia River (the largest discharge to the Pacific Ocean in North and South America).  A majority of contaminated sites are located along or near the waterfront—making them vulnerable to sea level rise, increasingly severe storms, flooding, and landslide. And, the state has plentiful forests, grasslands, shrub-lands, and drought in the eastern half of the state is commonplace—making these areas highly vulnerable to wildfire. All of these vulnerabilities have potential to impact the sustainability of remedies.

Washington State has re-defined the traditional concept of sustainable remediation by developing guidance that includes:

1.    An adaptation strategy to increase resilience of remedies to potential climate change impacts such as sea level rise and wildfire by conducting site-specific vulnerability assessments using a GIS application, developing risk management scenarios based on site-specific tolerance to climate change, and incorporating resiliency in all phases of cleanup.

2.    A mitigation strategy to minimize greenhouse gas emissions from the cleanup process.

3.    A green remediation strategy to reduce environmental impacts and increase environmental benefits from remediation by implementing best management practices and evaluating the effectiveness of green alternatives.  

Case studies will be presented that show the vulnerabilities of contaminated sites to climate change and how sustainable remediation can work by incorporating remedy resilience to climate change, mitigation, and green remediation.

1:45 - 2:05 p.m.

Applying Environmental Forensics and Modeling of Uncertain Environmental Systems for Effective Remediation and Stewardship

Boris Faybishenko, Lawrence Berkeley National Laboratory

Effective remediation and stewardship are crucial for safeguarding health and the environment, especially for organizations managing potentially hazardous sites. Recent research highlights the importance of integrating climate resilience into environmental cleanup strategies. Combining sustainable remediation practices with climate change adaptation creates resilient approaches that better address current contamination and the challenges posed by a changing climate and emerging pollutants. The first step is to develop a conceptual framework for assessing climate adaptation and environmental resilience in remediation projects by evaluating both risks and opportunities related to climate change and extreme weather events. The presentation will outline key components of this framework and their environmental impacts: (a) using innovative environmental forensics that blend various scientific disciplines to investigate contamination incidents, identify sources and types of pollutants, determine the timing and extent of contamination, and analyze long-term weather patterns; and (b) making predictions amid uncertainty, which is vital for effective environmental cleanup, as models forecasting contaminant behavior and assessing long-term exposure are inherently uncertain due to the highly variable nature of these processes. This is particularly true when predicting the success of remediation efforts, where limited data and incomplete understanding can lead to uncertain outcomes. The presentation will also explore advances in monitoring methods, especially through climate and environmental forensics used to reconstruct past climate and contamination events, as well as numerical techniques to manage uncertainty in remediation modeling. 

2:05 - 2:25 p.m.

5-D Approach for Resilient Groundwater Remediation

Alka Singhal, Arcadis

With over 126,000 contaminated sites in the U.S.—and roughly 12,000 unlikely to achieve full restoration this century—long-term or perpetual management is increasingly necessary. Many of these sites are located in areas vulnerable to climate-related hazards such as flooding, wildfires, and sea-level rise. The 5-D Approach for Resilient Groundwater Remediation introduces a framework built on five key dimensions: Data, Design, Dynamics, Decision-making, and Durability. This approach supports adaptive, climate-informed remediation strategies that enhance long-term effectiveness.

Two case studies illustrate the application of this approach. In the first, climate projection data was used to simulate future recharge scenarios, altering infiltration rates in a groundwater model supporting a pump-and-treat system. Results showed significant shifts in hydraulic containment, suggesting the need for additional extraction wells. The second case involved a site discharging to a gaining stream. Under projected drought conditions, contaminant mass loading to the stream increased, highlighting the need to anticipate hydrologic changes and adapt remediation strategies accordingly.

These examples demonstrate how climate change can alter groundwater flow and reduce the effectiveness of conventional remedies. The EPA is increasingly requiring climate vulnerability assessments, particularly under CERCLA. Tools ranging from basic screening to integrated climate-groundwater modeling can support adaptive planning. The 5-D framework provides a structured path to evaluate and enhance remedy resilience, ensuring that long-term site management remains protective under changing environmental conditions.

Open Discussion
 

BREAK
 

3:15 - 3:35 p.m.

Zonation of US Nuclear Facilities Based on the Meteorological Time Series Analysis and FEMA Indices for the Environmental Resilience Assessment

Boris Faybishenko, Lawrence Berkeley National Laboratory

The siting and operation of nuclear facilities must prioritize resilience and safety, particularly in the face of extreme weather events and long-term environmental considerations. For the locations of the 54 nuclear power plants in the United States, we developed a database of (a) meteorological parameters (including temperature, precipitation, and wind direction, using the PRISM and Reanalysis databases) and (b) the U.S. Federal Emergency Management Agency (FEMA) National Risk Index (NRI) hazard parameters. With this database, we conducted a statistical analysis of temporal trends in meteorological variables and calculated the Standard Precipitation-Evapotranspiration Index (SPEI) as an integrated meteorological index for the past 120 years. We performed a hierarchical clustering analysis of the SPEI (a quantitative measure) together with the FEMA Index hazard parameters (a qualitative measure). The results of the cluster analysis were then used to categorize the locations of the nuclear power plants into various regional zones. The developed environmental zonation does not correspond to the widely used Köppen-Geiger climate classification.

The presentation will also illustrate examples of the analysis of extreme weather events at several nuclear facilities (e.g., extreme precipitation and flooding). The approach developed can be employed for resilience planning, adaptation of nuclear facilities, mitigation, remediation, and long-term stewardship, considering anticipated environmental risk.

Coauthors: Dylan O'Ryan, Peter Nico, and Andrew Jones (LBNL)

3:35 - 3:55 p.m.

Climate Adaptation at Hazardous Waste Sites: Supporting Better Environmental Outcomes

Eric Mielbrecht, EcoAdapt

Ever wonder how climate change is being addressed at some of the most significant hazardous waste sites in the U.S. so people and the environment are protected? The Department of Energy (DOE) responded to the Government Accountability Office’s 2020 recommendation to better assess and mitigate the effects of climate change at its sites through its 2021 Climate Adaptation and Resilience Plan, associated guidance and actions. Many sites efficiently completed standardized assessment and have implemented resilience actions. However, concerns of the potential vulnerability of more complicated remedial actions and where long term reliability is essential sparked collaboration to support in-depth investigations and unique data tools that are leading to remediation design parameter changes, innovative monitoring systems and adaptive response policies. This presentation will highlight unique challenges and resilience actions from DOE Office of Environmental Management sites across the U.S. and focus on a collaborative process led by experts from Savannah River and Lawrence Berkeley National Labs, Massachusetts Institute of Technology and EcoAdapt to further understand vulnerabilities and develop resilience actions for disposal cells at the Savannah River Site and support better outcomes for nearby communities the environment.

Coauthor: Emily Fabricatore (SRNL)

3:55 - 4:15 p.m.

Uranium Remobilization from a Riparian Wetland: Implications on Long-Term Stewardship and Extreme Rain Events

Daniel Kaplan, Savannah River Ecology Laboratory, University of Georgia

Natural attenuation of contaminants by wetlands can cause these landforms to become secondary sources of contaminants, that is, they concentrate contaminants from the primary anthropogenic sources and then become potential secondary sources.  The objectives of this field study were to: 1) measure the remobilization of uranium (U) in a stream flowing through a contaminated wetland on the Savannah River Site in South Carolina, and 2) develop empirical relationships between rainfall and U remobilization. Stream water was sampled hourly during six storm events that varied between 0.69 and 9.87 cm rainfall and caused the stream flow rate to increase as much as 2500% greater than base flow.  U concentrations in all filtered samples, U<0.45µm, were well below the Maximum Contaminant Limit of 30 µg/L U.  Not surprisingly, most of the U transported in the stream was associated with suspended solids, U>0.45µm, which accounted for as much as 94 vol% of the U in the stream water.  Suspended solids U concentrations were as high as 967 mg-U/kg (background is 0.5 mg-U/kg) and had solid:liquid U-concentration ratios of >72,000 [(µg/kg)/(µg/L)].  Consequently, a significant (p <0.001) correlation was found between turbidity and stream water total U concentrations, which can be used to provide early guidance for estimating stream U concentrations.  Using a significant linear relationship (p <0.001) between rainfall and the mass of U remobilized during sampling events, it was estimated that about 30% of the remobilized U in 2024 occurred during the three greatest rain events.  Additional calculations indicated that since the release of 43,500 kg U into the wetland about 55 years ago, that 864 kg U, or 2.2 wt% had been remobilized.   This estimate is consistent with U mass balance calculations for the site that indicate 94 wt% of the released U remains in the wetland sediment.  Long-term predictions of increases in rainfall and extreme rain events in South Carolina may increase the rate of contaminant dispersion from riparian systems.

Coauthors: Karah M. Greene and Wei Xing (University of Georgia); Arelis M. Rivera-Giboyeaux (SRNL); Peng Lin (University of Georgia)

4:15 - 4:35 p.m.

Resilience Planning and the Development of the Risk Budget Tool to Support Low-Activity Waste Glass Disposal in the Hanford Integrated Disposal Facility

Keith Thomsen, Hanford Tank Waste Operations & Closure, LLC

The Hanford Waste Treatment and Immobilization Plant (WTP) Low-Activity Waste (LAW) Vitrification Facility is nearing the start of producing glass from actual tank waste. Ensuring the stability and durability of the immobilized LAW (ILAW) glass is critical for meeting WTP contract requirements, long-term performance expectations, and regulatory standards for disposal in the Integrated Disposal Facility (IDF). The 2017 IDF Performance Assessment (PA), developed in accordance with DOE Order 435.1, the associated manual, and permit conditions for mixed-waste disposal under the Hanford Site Resource Conservation and Recovery Act (RCRA) permit, evaluated the baseline LAW glass waste form’s long-term integrity. It used groundwater impact simulations to inform the Excel-based Risk Budget Tool (RBT), which assesses future groundwater risks under varying inventory and performance scenarios.

This paper will outline the LAW glass testing program, highlighting how it supports waste form performance under evolving environmental conditions. It will also detail efforts to improve the RBT by incorporating new WTP glass formulation and composition-property correlation models. These updates aim to link feed qualification data, final glass composition, and estimated dissolution behavior in the IDF. Additionally, updating the RBT will include resiliency capabilities, such as sensitivity analyses to evaluate the impact of emerging resiliency stressors such as climate change and periodic extreme weather events. These improvements are part of Hanford’s long-term commitment to proactive stewardship and underscores the site’s dedication to resilient, science-based environmental management.

Coauthors: David J. Swanberg and Rodney S. Skeen (Hanford Tank Waste Operations & Closure, LLC); Sebastien N. Kerisit, James J. Neeway, Benjamin Parruzot, R. Matthew Asmussen, and Gary L. Smith (PNNL)