Assessing ecological risks to the fish community from residual coal fly ash in Watts Bar Reservoir, Tennessee

Abstract

EDITOR'S NOTE:The Baseline Ecological Risk Assessment (BERA) of residual coal-fly ash in Watts Bar Reservoir was conducted following a 2008 spill from the Tennessee Valley Authority Kingston Fossil Plant (Roane County, TN). Results of the BERA were used to focus the long-term management strategy for the impacted river system. This article is among 7 peer-reviewed articles in the special series, "Ecological Risk Assessment for Residual Coal Fly Ash at Watts Bar Reservoir, Tennessee." The series includes articles presenting the following: problem formulation for the river system; sediment toxicity test procedures; benthic community analysis techniques; methods used to evaluate risk to benthic receptors, fish, and riparian and aquatic wildlife; an extensive analysis characterizing risk to the insectivorous tree swallow; and finally, how the BERA results influenced management decisons. ABSTRACTExtensive site-specific biological and environmental data were collected to support an evaluation of risks to the fish community in Watts Bar Reservoir from residual ash from the December 2008 Tennessee Valley Authority (TVA) Kingston ash release. This article describes the approach used and results of the risk assessment for the fish community, which consists of multiple measurement endpoints (measures of exposure and effects) for fish. The lines of evidence included 1) comparing postspill annual fish community assessments with nearby prespill data and data from other TVA reservoirs, 2) evaluating possible effects of exposures of fish eggs and larval fish to ash in controlled laboratory toxicity tests, 3) evaluating reproductive competence of field-exposed fish, 4) assessing individual fish health through physical examination, histopathology, and blood chemistry, 5) comparing fish tissue concentrations with literature-based critical body residues, and 6) comparing concentrations of ash-related contaminants in surface waters with US Environmental Protection Agency's (USEPA) Ambient Water Quality Standards for Fish and Aquatic Life. These measurement endpoints were treated as independent lines of evidence that were integrated into an overall weight-of-evidence estimate of risk to the fish community. Collectively, the data and analysis presented here indicate that ash and ash-related constituents pose negligible risks to the fish communities in Watts Bar Reservoir. This conclusion contradicts the predictions by some researchers immediately following the ash release of devastating effects on the aquatic ecology of Watts Bar Reservoir. The information presented in this article reaffirms the wisdom of carefully evaluating the evidence before predicting probable ecological effects of a major event such as the TVA Kingston ash release. This study demonstrates that a thorough and detailed investigation using multiple measurement endpoints is needed to properly evaluate ecological effects. Integr Environ Assess Manag 2015;11:88-101. © 2014 SETAC

Application of ecological risk assessment in managing residual fly ash in TVA's Watts Bar Reservoir, Tennessee

“…Fish community surveys were given the greatest weight in the estimation of risk to fish. Similar to the benthic community surveys, they indicated no ecologically important impacts to individuals due to residual ash that might subsequently be manifested at population or community levels (Rigg et al , this issue). The results of fish toxicity tests, reproductive competence evaluations, and fish health studies also suggested no notable adverse effects of the ash at the organism or suborganism level (Rigg et al , this issue).…”

“…The 17 receptor groups evaluated included fish, benthic invertebrates, aquatic plants (periphyton and macrophytes), and wildlife that feed in and around the river system (see conceptual site model in Figure 2 in Walls, Jones et al 2015, this issue). BERA details are available in the project report (ARCADIS ), and details for several receptors are presented in 5 other articles in this series (Buys et al , Meyer et al , Rigg et al , Stojak et al , Walls, Meyer et al ).…”

“…Five key factors influenced the BERA conclusions: 1) availability of site‐specific population and community data for several receptor groups (Walls, Jones et al , this issue); 2) sediment toxicity test results for a broad range of ash concentrations (Stojak et al , this issue); 3) dietary exposure model results (Meyer et al , this issue); 4) availability of site‐specific bioaccumulation data (Buys et al , Meyer et al , Rigg et al , Walls, Meyer et al , this issue); and 5) the scope and breadth of the assessment (Walls, Jones et al , this issue). These factors collectively provided a high level of confidence in the BERA's main conclusion: only benthic invertebrates and insectivorous birds in the Emory River had sufficient potential for adverse effects from the residual ash to warrant risk management.…”

Ecological risk assessment for residual coal fly ash at Watts Bar Reservoir, Tennessee: Site setting and problem formulation

“…These various types of samples were used to estimate bioavailability and bioaccumulation of COPECs from diet and other exposure pathways, as well as to model bioavailability to the respective predators. Subsequent articles focus on the evaluations for fish (Rigg et al , this issue), benthic invertebrates (Buys et al , this issue, and Stojak et al , this issue), aquatic‐ and riparian‐feeding wildlife (Meyer et al , this issue), and aerial‐feeding insectivores (i.e., tree swallows; Walls et al , this issue).…”

“…They were evaluated at the suborganism level, assessing molecular, biochemical and physiological endpoints. Fish health metrics in this study included reproductive condition (ovary stage, oocyte condition, estimation of fecundity), gonadosomatic index (GSI) (relative size of gonad to body size), bioenergetic and hematological responses, histopathological indicators, indicators of carbohydrate‐protein metabolism, organ dysfunction responses, measures of electrolyte homeostasis, and indices of feeding and nutrition (parameters associated with digestive physiology) (Rigg et al , this issue; Bevelhimer et al ). Avian health metrics included tree swallow, heron, and osprey egg weight, volume, length, and width.…”