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Tad Deshler Windward Environmental LLC

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  1. Alternative Evaluation Framework for Managing Dioxins/Furans in Dredged Material Proposed for Open-Water Disposal Tad Deshler Windward Environmental LLC

  2. A tiered testing approach has been used successfully for many years, but this approach is largely chemical-independent Biological testing frequently involves laboratory bioaccumulation studies

  3. Why might dioxins/furans merit a different approach? • Given the toxicity of this chemical group, the environmental concern is often fish/shellfish consumers • In such cases, laboratory bioaccumulation tests for dioxins/furans do not focus on the appropriate endpoint • Bioaccumulation is lower for dioxins/furans as compared with that of other bioaccumulative compounds

  4. Bioaccumulation of Dioxin/Furans 50th percentile (median) PCBs – 1.5 Dioxins/furans – 0.03 Source: EPA BSAF database (v. 1.0)

  5. Dioxin/Furan Tissue Concentrations in Puget Sound

  6. Alternate Framework • At Tier 3 and above in the existing framework, project-specific decisions are made using sediment quality objectives for dioxins/furans, which were developed for the protection of benthic invertebrate communities • For the protection of fish/shellfish consumers, suitability determinations would not be made on a project-by- project basis • Instead, monitoring program would be developed for disposal sites to determine if dredged material is having an unacceptable impact on fish/shellfish resources

  7. Alternate Framework (cont.) • Pilot study should include baseline monitoring at disposal site and background areas • Adaptive management approach based on future (bi-annual?) monitoring should be paid for by dredging proponents with money that might otherwise go to bioaccumulation testing • If disposal site monitoring indicates increasing dioxin/furan concentrations in fish/shellfish, the sediment quality objective can be adjusted downward

  8. Monitoring Strategy • Include species consumed by people that are known to live in the vicinity of the disposal site • Collect enough samples to document expected variability in concentrations • Establish action thresholds • Exceedance of thresholds would trigger evaluation of projects using the disposal site

  9. Interpreting Monitoring Data • Exceedance of tissue action thresholds would trigger evaluation of recent projects that used the disposal site • Projects could be ranked with respect to dioxin/furan concentrations in dredged material • Concentrations associated with higher-ranked projects could establish new sediment quality objective

  10. Benefits of an Alternate Framework • Provides more certainty for dredging proponents, particularly in urban environments where dioxins/furans are more likely to be found • May reduce unnecessary upland disposal • Expense of upland disposal (given overly protective evaluation procedures) may make some dredging projects infeasible • Upland disposal can have greater adverse impact on environment and human health than does open water disposal when all impacts are considered

  11. Questions? Tad Deshler tad@windwardenv.com