Speaker: Curtis DeGasperi, ENSR Co-Authors: Tarang Khangaonkar, Ph.D.,P.E., ENSR

1. A Screening Model of Sediment Recontamination Following Cleanupat the Norfolk Site, Duwamish River,Seattle, Washington Speaker:Curtis DeGasperi, ENSR Co-Authors: Tarang Khangaonkar, Ph.D.,P.E., ENSR Steve Breithaupt, Ph.D., ENSR John Koch, HDR Engineering, Inc. Rick Andrews, King County Dept. of Natural Resources

2. Henderson/M.L. King CSO Study Objectives • Eliminate CSOs to Lake Washington • Minimize impact of CSOs at Norfolk site on water and sediment quality • Ensure no sediment recontamination following cleanup of contaminated sediments at Norfolk • Evaluate impact of treated CSOs • Evaluate impact of Norfolk storm drain discharges

3. Norfolk Site Map

4. Constituents of Concern • Mercury • 1,4-dichlorobenzene (1,4-DCB) • Benzoic Acid • Bis(2-ethylhexyl)phthalate (DEHP) • PCBs

5. CSO Treatment Approach • Treat resulting CSOs at Norfolk before discharge to the Duwamish using: • Rectangular clarifier (volume: 3.2-5.2 MG) • Tunnel (length = 3,600 ft, diameter = 14.5 ft, volume: 4.4 MG)

6. Modeling Approach • Water quality data collection • Synthetic hydrographs of CSO and storm water flow rates • Model of solids removal during treatment (PHEONICS/Partrak) • Model of toxics removal during treatment (WASP/TOXI5) • Hydrodynamic model of initial dilution (CORMIX3) • Sediment recontamination screening model (SEDCAM/METSED)

7. Norfolk Storm Drains Norfolk CSO Inflow Water Duwamish River Inflow Partitioning Duwamish River Outflow Cd Cp Solids Settling Sediment First-order losses (diffusion/decay) Cp Solids Deep Burial C(t) = Accumulation - Burial - Loss from diffusion/decay SEDCAM/METSED Model

8. SEDCAM/METSED Model Description • Steady-state box model • Quasi-dynamic through use of dilution prediction in each time step • Considers contaminant partitioning to settling sediment • Mixing occurs with previously deposited sediment • Losses occur through deep burial, diffusion, and decay

9. SEDCAM/METSED Model Description (continued) • Generally conservative • Does not consider dynamic movement and dilution of discharge plume during each storm/CSO event • Does not consider contaminant losses due to resuspension and transport of contaminated sediment

10. SEDCAM/METSED Model Application • Sediment recontamination evaluation performed for: • Rectangular clarifier design • Tunnel design • Norfolk storm drain discharges

11. Water Quality Data Summary Average Concentrations (µg/L) Benzoic Acid Aroclor PCBs Mercury 14-DCB DEHP CSOs 0.22 0.46 1.7 1.6 <0.13 Norfolk Drains <0.2 <0.15 2.4 4.5 0.105 Boeing Drains <0.2 <0.14 2.3 2.2 0.060 I-5 Drain <0.2 <0.15 1.6 5.2 <0.13

12. Average Concentration (mg/L) TSS TOC CSOs 111 16 Norfolk Drains 35 6.2 Boeing Drains 6.9 4.0 I-5 Drain 49 14.8 Water Quality Data Summary (Cont’)

13. Hydrodynamic Dilution Model WASP Clarifier Toxics Removal Model Clarifier Hydrodynamic/Solids Removal Model CSO Water Quality Data Synthetic CSO Hydrograph 1 year hydrograph SEDCAM/METSED Recontamination Model Spreadsheet Model - weekly time-step Clarifier Design Evaluation

14. Partition Coeff./Log Kow CoCs % Toxics Removal Mercury 42.3 20,000 L/kg 1,4-DCB 0.1 3.47 Benzoic acid 0 1.87 DEHP 61.3 9.36 PCBs 60.0 7.0 Note: Based on % solids removal predicted by PHOENICS/Partrak - 61.3% WASP Model 4.22 MG Clarifier Toxics Removal

15. SEDCAM/METSED Model Predictions - 4.22 MG Clarifier

16. Model Prediction Washington Marine SQS Maximum Average CoCs Mercury 150 110 410 1,4-DCB 88 8 3100 Benzoic acid 0.1 0.01 650 DEHP 18,800 1,900 47,000 PCB 754 77 12,000 Note: Concentrations of mercury and benzoic acid are in µg/kg dry sediment; concentrations of remaining constituents are in µg/kg organic carbon SEDCAM/METSED Model Predictions - 4.22 MG Clarifier

17. Clarifier Hydrodynamic/Solids Removal Model WASP Clarifier Toxics Removal Model Hydrodynamic Dilution Model CSO Water Quality Data Synthetic CSO Hydrograph 1 year hydrograph SEDCAM/METSED Recontamination Model Spreadsheet Model - weekly time-step Tunnel Design Evaluation

18. Model Prediction Washington Marine SQS Maximum Average CoCs Mercury 168 116 410 1,4-DCB 97 20 3100 Benzoic acid 0.1 0.03 650 DEHP 48,155 8,671 47,000 PCB 1,873 339 12,000 Note: Concentrations of mercury and benzoic acid are in µg/kg dry sediment; concentrations of remaining constituents are in µg/kg organic carbon SEDCAM/METSED Model Predictions - Tunnel

19. SEDCAM/METSED Model Predictions - Tunnel Design • Developed Fortran-executable version of SEDCAM/METSED to: • Allow for use of 19-year synthetic hydrograph • Smaller time steps (approximately 10 minutes) • Flow-based contaminant removal

20. SEDCAM/METSED Model Predictions - Tunnel Design

21. SEDCAM/METSED Model Predictions - Tunnel Design

22. Norfolk Drain Evaluation • Storm drain water quality data • Synthetic storm drain hydrograph (1 year) • Hydrodynamic model dilution predictions • SEDCAM/METSED recontamination modeling • Spreadsheet model - weekly time step • Fortran version - approx. 10 minute time step

23. Model Prediction Washington Marine SQS Maximum Average CoCs Mercury 163 131 410 1,4-DCB 37 18 3100 Benzoic acid 0.5 0.2 650 DEHP 290,000 160,000 47,000 PCB 1,412 818 12,000 Note: Concentrations of mercury and benzoic acid are in µg/kg dry sediment; concentrations of remaining constituents are in µg/kg organic carbon Norfolk Drains - Spreadsheet Model

24. Norfolk Drains - Fortran Model

25. Comparison of Treated CSO and Norfolk Drain Discharges

26. Conclusions • Treated CSO discharges at Norfolk will not recontaminate sediments • Recontamination of sediments with DEHP may occur due to untreated discharges from Norfolk drains