APPLICATION OF THE IEM-2M MERCURY FATE AND TRANSPORT MODEL IN HAZARDOUS WASTE COMBUSTION FACILITY RISK ASSESSMENTS

1. APPLICATION OF THE IEM-2M MERCURY FATE AND TRANSPORT MODEL IN HAZARDOUS WASTE COMBUSTION FACILITY RISK ASSESSMENTS Sarah A. Foster, Paul C. Chrostowski, CPF Associates, Inc. Suellen Pirages, International Center for Toxicology and Medicine Mark Nealley, Environmental Profiles 2006 Waste Management National Meeting Arlington, VA January 19, 2006

2. Importance of Mercury in Risk Assessment Process • Mercury is often a risk driver in combustion facility risk assessments • Often accounts for more than 90% of the total non-cancer hazard index for the fish ingestion exposure pathway

3. Presentation Outline • Mercury models in EPA combustion source risk assessments • Compare default to IEM-2M • Case studies • Conclusions

4. Mercury Models For Combustion Source Risk Assessment • HHRAP • Finalized September 2005 • IEM-2M Model • Mercury Report to Congress (1997), Utility Report to Congress (1998), HWC Risk Assessment (1999) • SERAFM Model (under development) • IEM-2M update • Regulatory Impact Analysis for Clean Air Mercury Rule (2005) • All models developed by USEPA

5. Watershed & Waterbody Modeling • Site-specific IEM-2M application • Replaces small portion of HHRAP framework • IEM-2M feeds into HHRAP • Use IEM-2M to calculate dissolved mercury waterbody concentrations  calculate fish tissue concentrations • Verified performance of IEM-2M against EPA example calculation from MACT risk assessment

6. HHRAP and IEM-2M

7. IEM-2M Case Studies: Facilities • Four hazardous waste combustion facilities in eastern US • 3 cement kilns • 1 on-site incinerator at manufacturing facility

8. IEM-2M Case Studies: Waterbodies • Five waterbodies • Cement kiln #1 – river • Cement kiln #2 – river • Cement kiln #3 – lake and swamp • Incinerator – creek

9. Modeling Flow Chart Compile input data Watershed: Calculate differential equation input values Watershed: Solve and compile output from 3 watershed differential equations Waterbody: Calculate differential equation input values Waterbody: Solve and compile output from 6 waterbody differential equations IEM-2M modeling results

10. Modeling Flow Chart Compile input data Watershed: Calculate differential equation input values Watershed: Solve and compile output from 3 watershed differential equations Waterbody: Calculate differential equation input values Waterbody: Solve and compile output from 6 waterbody differential equations IEM-2M modeling results

11. Inputs to IEM-2M • Site-specific • Chemical-specific • Chemical independent constants

12. Site-Specific Inputs to IEM-2M • Emission rate • Dispersion and deposition modeling results • Waterbody and watershed dimensions • Water flow rate • Total suspended solids • Unit soil loss • Precipitation • Facility lifetime

13. Chemical-Specific Inputs • Mercury Report to Congress • Data for three Hg species • Henry’s law constants • Diffusivities • Partition coefficients • Transfer coefficients • Transformation rates

14. Chemical Independent Constants • Mercury Report to Congress • Sediment solids density • Soil layer thickness • Solids settling velocity • Solids resuspension velocity

15. Comparison of Site-Specific Characteristics

16. Comparison of Site-Specific Characteristics

17. Modeling Flow Chart Compile input data Watershed: Calculate differential equation input values Watershed: Solve and compile output from 3 watershed differential equations Waterbody: Calculate differential equation input values Waterbody: Solve and compile output from 6 waterbody differential equations IEM-2M modeling results

18. Comparison of Site-Specific Loading Rates

19. Modeling Flow Chart Compile input data Watershed: Calculate differential equation input values Watershed: Solve and compile output from 3 watershed differential equations Waterbody: Calculate differential equation input values Waterbody: Solve and compile output from 6 waterbody differential equations IEM-2M modeling results

20. Parameters Evaluated in Differential Equations Facility Lifetime (time-dependent/steady-state)

21. Example IEM-2M Model Output

22. Modeling Flow Chart Compile input data Watershed: Calculate differential equation input values Watershed: Solve and compile output from 3 watershed differential equations Waterbody: Calculate differential equation input values Waterbody: Solve and compile output from 6 waterbody differential equations IEM-2M modeling results

23. IEM-2M and HHRAP Results: Soil Concentrations

24. IEM-2M and HHRAP Results: Waterbody Concentrations

25. IEM-2M and HHRAP Results: Sediment Concentrations

26. HHRAP – IEM-2M Comparisons • Dissolved meHg water column concentrations and fish ingestion hazard quotients, on average, 50 times higher using HHRAP versus IEM-2M (range 8-190) • Benthic sediment meHg concentrations may be slightly higher or lower using HHRAP versus IEM-2M • Watershed soil results slightly higher using HHRAP

27. Site-Specific Conclusions • No clear pattern of parameter influence • Important site-specific factors • Emission rates • Deposition rates to watershed • Size of watershed area (soil erosion) • Total loading to waterbody • Total suspended solids concentration • Waterbody flow rate • IEM-2M applications were accepted by EPA Regions and state review agencies