Human Health & Ecological Risk Assessment / Environmental Investigation Support: Smokey Mountain Smelter Superfund Site


Human Health & Ecological Risk Assessment / Environmental Investigation Support: Smokey Mountain Smelter Superfund Site


USEPA Region 4


  • Data Gaps Review
  • Multi-media Field Investigations and Sediment Toxicity Testing
  • Human Health Risk Assessment (HHRA)
  • Baseline Ecological Risk Assessment (BERA)
  • modified Rapid Bioassessment Protocols
  • Cost saving measures


Avatar led the HHRA and ERA for the Smokey Mountain Smelter (SMS) RI/FS in Knoxville, Tennessee. The RI/FS was a collaborative effort between EPA and the Tennessee Department of Environmental Conservation (TDEC). The SMS RI/FS evaluated the extent of contamination and potential impacts on the 27-acre site, the Flenniken Branch Watershed that receives runoff and discharge from the site and the Knob Creek Embayment portion of the Tennessee River. Primary contaminants of concern at this site include aluminum, arsenic, chromium, copper, lead and zinc that were discharged during smelting activities and continue to be released from on-site landfills, settling ponds, and groundwater.

Avatar provided a data gaps summary for determining site investigation needs and participated in multi-media field investigations for the site. Avatar provided support in the preparation of a Sampling and Analysis Plan and QAPP to ensure DQOs were being met.

The HHRA was conducted in order to characterize the potential exposure and risks associated with soil, groundwater, fish tissue, and soil gas at the SMS Site. The evaluation of the SMS Site was unique due to the presence of a clay cap of the onsite aluminum dross and salt cake landfill. Avatar developed a quantitative evaluation of essential nutrients due to unusually high levels resulting from previous site activities (i.e., salt cakes). Based on the proximity to nearby residential properties, an evaluation of potential future residential exposure to indoor air was conducted based on soil gas. Active railroad lines and the lack of onsite buildings made this a unique evaluation for the SMS Site. Lastly, the HHRA evaluated exposure to site anglers, which proved challenging given the proximity of other potential source areas and the contribution from the Tennessee River. Given these unique and complex conditions, the HHRA was able to adequately identify and quantify exposures to current and potential future human health receptors without the burden of excessive sampling and characterization of contaminated media.


The ERA focused on impacts to the benthic community in Flenniken Branch and the fish and benthic communities in the Knob Creek Embayment. Benthic community and habitat assessments followed TDEC macroinvertebrate survey procedures (modified Rapid Bioassessment Protocols) including habitat quality evaluations and taxonomic metrics comparisons. Sediment toxicity testing (28-day Hyalella azteca) was also conducted to complete a sediment triad evaluation. Bottom feeder and upper trophic level fish species were collected from the Knob Creek Embayment and health condition indices were collected prior to submission for chemical analysis. Food chain models for both avian and mammalian receptors were evaluated.

In addition, Avatar negotiated state agency support in the collection and enumeration of benthic community samples and the collection of fish samples, thereby saving the project over $37K and worked with the sediment toxicity contract laboratory in the development of a serial dilution study that simplified the estimation of clean-up levels and saved the project the expense of collecting additional sediment samples, estimated saving approximately $21K.