Development of a Monitoring Plan for Evaluating Effectiveness of Remedial Actions for Residual Fly Ash in Watts Bar Reservoir, Tennessee

摘要

Background/Objectives. Approximately 437,000 cu yd of residual ash remains in theEmory, Clinch, and Tennessee Rivers after completion of hydraulic and mechanicaldredging to remove the bulk of the 5.4 million cu yd TVA Kingston fly ash spill. The majorityof residual ash is in portions of the Clinch and Emory Rivers that have legacy contaminantsfrom Department of Energy weapons productions facilities at Oak Ridge,Tennessee. Disturbance of those sediments by dredging activities may have a greater environmentalimpact than leaving the residual ash in place and monitoring the natural recoveryof the river system.Approach/Activities. Immediately after the ash spill TVA implemented air, water, andindustrial hygiene monitoring activities to evaluate potential health threats. Within twoweeks, sampling of fish and benthic invertebrates had begun, along with bathymetric surveysand sediment sampling to characterize the extent of the spill. Within three months,scientists from Oak Ridge National Laboratory and the US Army Corps of Engineers EngineerResearch and Development Center at Vicksburg, Mississippi were investigatingpossible effects on fish health and reproduction, and the biogeochemistry of fly ash. TVAalso conducted an extensive series of ash and sediment toxicity investigations. Biologicalmonitoring eventually included multiple species of fish and birds, amphibians, reptiles,mammals, snails, periphyton, and vascular plants. Thirteen universities, three federal laboratories,four environmental contracting firms, four toxicity testing laboratories, andten commercial analytical laboratories were involved at some point.An adaptive management strategy focused resources on areas most likely to experienceadverse effects from the spilled ash. Results were continually evaluated to ensurethe appropriate level of effort was applied to address unanswered questions and to followup on results, as necessary.Results/Lessons Learned. Results from these investigations were integral to the BaselineHuman Health and Ecological Risk Assessments (BHHRA and BERA) evaluatingpotential long-term effects of the residual ash in the river system, and in identifying remedialactions to address the identified risks. For example, from the robust database developedfrom these efforts the BERA was able to use measured concentrations ofcontaminants of concern in prey as input to dietary exposure models, and to use measuredtissue concentrations for comparison with literature-based adverse effects levels.The results developed in these investigations also have been critical for designing acost-effective, yet robust long-term monitoring plan to track the effectiveness of the selectedremedial actions. This presentation describes the development and implementationof that plan, building on the environmental monitoring and research conducted by TVA