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A Screening Model of Sediment Recontamination Following Cleanup at the Norfolk Site, Duwamish River, Seattle, Washington Speaker: Curtis DeGasperi, ENSR.

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Presentation on theme: "A Screening Model of Sediment Recontamination Following Cleanup at the Norfolk Site, Duwamish River, Seattle, Washington Speaker: Curtis DeGasperi, ENSR."— Presentation transcript:

1 A Screening Model of Sediment Recontamination Following Cleanup at 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 v Eliminate CSOs to Lake Washington v Minimize impact of CSOs at Norfolk site on water and sediment quality v Ensure no sediment recontamination following cleanup of contaminated sediments at Norfolk âEvaluate impact of treated CSOs âEvaluate impact of Norfolk storm drain discharges

3 Norfolk Site Map

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

5 CSO Treatment Approach v Treat resulting CSOs at Norfolk before discharge to the Duwamish using: âRectangular clarifier (volume: MG) âTunnel (length = 3,600 ft, diameter = 14.5 ft, volume: 4.4 MG)

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

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

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

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

10 SEDCAM/METSED Model Application v Sediment recontamination evaluation performed for: âRectangular clarifier design âTunnel design âNorfolk storm drain discharges

11 Water Quality Data Summary Average Concentrations (µg/L) Mercury14-DCB Benzoic Acid DEHP Aroclor PCBs CSOs <0.13 Norfolk Drains <0.2< Boeing Drains <0.2< I-5 Drain<0.2< <0.13

12 Water Quality Data Summary (Cont’) Average Concentration (mg/L) TSSTOC CSOs11116 Norfolk Drains356.2 Boeing Drains I-5 Drain4914.8

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

14 WASP Model 4.22 MG Clarifier Toxics Removal % Toxics Removal Partition Coeff./Log K ow Mercury42.320,000 L/kg 1,4-DCB DEHP PCBs Note: Based on % solids removal predicted by PHOENICS/Partrak % CoCs Benzoic acid

15 SEDCAM/METSED Model Predictions MG Clarifier

16 Model Prediction Washington Marine SQS CoCs MaximumAverage Mercury ,4-DCB Benzoic acid DEHP18,8001,90047,000 PCB ,000 Note: Concentrations of mercury and benzoic acid are in µg/kg dry sediment; concentrations of remaining constituents are in µg/kg organic carbon

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

18 SEDCAM/METSED Model Predictions - Tunnel Model Prediction Washington Marine SQS CoCs MaximumAverage Mercury ,4-DCB Benzoic acid DEHP48,1558,67147,000 PCB1, ,000 Note: Concentrations of mercury and benzoic acid are in µg/kg dry sediment; concentrations of remaining constituents are in µg/kg organic carbon

19 SEDCAM/METSED Model Predictions - Tunnel Design v Developed Fortran-executable version of SEDCAM/METSED to: âAllow for use of 19-year synthetic hydrograph âSmaller time steps (approximately 10 minutes) âFlow-based contaminant removal

20 SEDCAM/METSED Model Predictions - Tunnel Design

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

23 Norfolk Drains - Spreadsheet Model Model Prediction Washington Marine SQS CoCs MaximumAverage Mercury ,4-DCB Benzoic acid DEHP290,000160,00047,000 PCB1, ,000 Note: Concentrations of mercury and benzoic acid are in µg/kg dry sediment; concentrations of remaining constituents are in µg/kg organic carbon

24 Norfolk Drains - Fortran Model

25 Comparison of Treated CSO and Norfolk Drain Discharges

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


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