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

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 risks to benthic organisms, fish, and riparian and aquatic wildlife; an extensive analysis characterizing risk to insectivorous birds; and finally, how the BERA results influenced management decisions. ABSTRACTA baseline ecological risk assessment (BERA) was performed for residual ash in the Watts Bar Reservoir following a release of fly ash from the Tennessee Valley Authority (TVA) Kingston Fossil Plant. The site consists of parts of 3 rivers in eastern Tennessee comprising over 32 river kilometers. The purpose of the assessment was to determine if residual ash negatively impacts maintenance and reproduction of balanced communities or populations of potentially exposed ecological receptor groups in these rivers. This introductory article summarizes the site and environmental setting, assessment and measurement endpoints, risk characterization methods, and the study approach. Subsequent articles describe ecological risks to fish, benthic invertebrates, aquatic-and riparian-feeding wildlife, and aerial-feeding insectivores; and the role ecological risk characterization played in determining the most effective management of the residual ash, setting project remediation objectives and targets, and designing long-term monitoring to measure the effectiveness of the selected removal action. Integr Environ Assess Manag 2015;11:32-42. © 2014 SETAC

Characterization of coal ash released in the TVA Kingston spill to facilitate detection of ash in river systems using magnetic methods

“…However, no dredging was performed downstream of the ash storage area (see inset map, Fig. 1), or in the Clinch or Tennessee Rivers downstream of the spill and 400,000 m 3 of ash is estimated to remain in the river system [2]. There are pockets of ash up to 0.125 m thick within the riverbed in the area between ERM 4.0 and CRM 3.0 [7].…”

“…Due to its association with heavy metals, coal ash is now recognized by the public as a substantial threat to drinking water, recreation, aquatic organisms and habitat [3,4]. Most of the coal ash spilled at Kingston was mechanically and hydraulically dredged, however 400,000 m 3 was mixed with legacy contaminants, primarily 137 Cs and Hg released from US Department of Energy facilities at Oak Ridge [2] and another 92,000 m 3 eroded during a flood prior to dredging [5]. The remaining ash has been and continues to be scoured, suspended and mixed with riverbed sediments as it is transported 71 km downstream to the Watts Bar Dam where it will be buried within reservoir sediment.…”

“…This practice received little attention from the public until December 2008, when 4.1 million m 3 of coal ash at the Tennessee Valley Authority (TVA) Kingston Fossil Plant in Kingston, Tennessee spilled into the Emory River in the upper reaches of the Watts Bar Reservoir system [2]. Due to its association with heavy metals, coal ash is now recognized by the public as a substantial threat to drinking water, recreation, aquatic organisms and habitat [3,4].…”

Evaluating risks to wildlife from coal fly ash incorporating recent advances in metals and metalloids risk assessment

“…Such reference reaches represent background conditions (no known contaminant releases) and had significantly lower concentrations of the ash‐related COPECs in the sediment. The highest amounts of residual ash were in the Emory and Clinch rivers (Table S1 in Supplemental Data has sediment COPEC concentrations; Walls et al , this issue, provides ash amounts).…”

“…A section of the Emory River was filled with ash up to 9 m deep. Although some affected areas in the Emory River were dredged from March 2009 to August 2010 (approximately Emory River Mile [ERM] 1.8 to 5.5, Figure ), approximately 400,000 m 3 remains in over 20 river miles in the system (hereafter, called the site), having the potential to adversely affect wildlife (Walls et al , this issue).…”