Evidence That Matters: Informing CCR Closure Decisions Through Site-Specific Risk Assessment

Generic models, such as those used in the EPA’s 2014 and 2024 national risk assessments of coal combustion residual (CCR) units, often rely on conservative assumptions that may not reflect the complexity of site-specific conditions. When used as the sole basis for decision-making, these models can lead to misinformed or overly cautious management strategies that may not be appropriate for individual sites. In contrast, our site-specific approach to risk assessment relies on the extensive environmental investigations at multiple Tennessee Valley Authority (TVA) fossil plants in Tennessee. These investigations included collecting data from surface water, sediment, and biological tissues as well as assessing indicators of aquatic community health. Our methodology emphasizes the integration of multiple lines of evidence to inform human health and ecological risk assessments (HHERAs) conducted under the Tennessee Department of Environment and Conservation (TDEC) Order. This presentation outlines our framework for prioritizing and synthesizing both quantitative and qualitative lines of evidence. Attendees will gain insight into which lines of evidence we found to be most relevant and reliable for assessing human health and ecological risks from CCR units. The framework begins with receptor-specific screening of CCR Parameters across relevant environmental media, using both medium-specific and receptor-specific screening levels. It then incorporates a critical evaluation of whether observed exposures are attributable to CCR units or are consistent with local or regional background conditions. This distinction helps avoid misattribution of risk. Ultimately, this approach supports more informed, transparent, and site-appropriate decisions regarding CCR unit closure and corrective actions that reflect the realities of each site rather than generalized assumptions.