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

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 NorfolkEvaluate impact of treated CSOs Evaluate impact of Norfolk storm drain discharges

Norfolk Site Map

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

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)

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)

SEDCAM/METSED Model

Water

Sediment

DuwamishRiver

Outflow

Cd Cp Solids

Settling

First-order losses(diffusion/decay)

Cp Solids

Deep Burial

NorfolkStormDrains

NorfolkCSO

Inflow

DuwamishRiver

InflowPartitioning

C(t) = Accumulation - Burial - Loss from diffusion/decay

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

SEDCAM/METSED Model Description (continued)

Generally conservativeDoes not consider dynamic movement and dilution of

discharge plume during each storm/CSO eventDoes not consider contaminant losses due to

resuspension and transport of contaminated sediment

SEDCAM/METSED Model Application Sediment recontamination evaluation performed

for:Rectangular clarifier designTunnel designNorfolk storm drain discharges

Water Quality Data Summary

Average Concentrations (µg/L)

Mercury 14-DCBBenzoic

Acid DEHPAroclorPCBs

CSOs 0.22 0.46 1.7 1.6 <0.13

NorfolkDrains

<0.2 <0.15 2.4 4.5 0.105

BoeingDrains

<0.2 <0.14 2.3 2.2 0.060

I-5 Drain <0.2 <0.15 1.6 5.2 <0.13

Water Quality Data Summary (Cont’)

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

Clarifier Design Evaluation

CSO Water Quality Data

Synthetic CSO Hydrograph1 year hydrograph

SEDCAM/METSED Recontamination ModelSpreadsheet Model - weekly time-step

Hydrodynamic Dilution Model

WASP Clarifier Toxics Removal Model

Clarifier Hydrodynamic/Solids Removal Model

WASP Model 4.22 MG Clarifier Toxics Removal

% Toxics RemovalPartition

Coeff./Log Kow

Mercury 42.3 20,000 L/kg

1,4-DCB 0.1 3.47

0 1.87

DEHP 61.3 9.36

PCBs 60.0 7.0

Note: Based on % solids removal predicted by PHOENICS/Partrak - 61.3%

CoCs

Benzoic acid

SEDCAM/METSED Model Predictions - 4.22 MG Clarifier

BIS(2-ETHYLHEXYL)PHTHALATE

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

YEAR

µg

/kg

OC

Model Prediction

SQS

SEDCAM/METSED Model Predictions - 4.22 MG Clarifier

Model Prediction WashingtonMarine SQSCoCs Maximum Average

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

Tunnel Design Evaluation

CSO Water Quality Data

Synthetic CSO Hydrograph1 year hydrograph

Clarifier Hydrodynamic/Solids Removal Model

WASP Clarifier Toxics Removal Model

Hydrodynamic Dilution Model

SEDCAM/METSED Recontamination ModelSpreadsheet Model - weekly time-step

SEDCAM/METSED Model Predictions - Tunnel

Model Prediction WashingtonMarine SQSCoCs Maximum Average

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 Design Developed Fortran-executable version of

SEDCAM/METSED to:Allow for use of 19-year synthetic hydrographSmaller time steps (approximately 10 minutes)Flow-based contaminant removal

SEDCAM/METSED Model Predictions - Tunnel Design

BIS(2-ETHYLHEXYL)PHTHALATE

0 10,000 20,000 30,000 40,000 50,000

Maximum

Average

Mo

del

Pre

dic

tio

n

µg/kg OC

DEHP 11573 1357

Maximum Average

SQS=47,000 µg/kg OC

SEDCAM/METSED Model Predictions - Tunnel Design

BIS(2-ETHYLHEXYL)PHTHALATE

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

YEAR

µg

/kg

OC

Model Prediction

SQS

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 stepFortran version - approx. 10 minute time step

Norfolk Drains - Spreadsheet Model

Model Prediction WashingtonMarine SQSCoCs Maximum Average

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 - Fortran Model

BIS(2-ETHYLHEXYL)PHTHALATE

0 50,000 100,000 150,000 200,000 250,000

Maximum

Average

Mo

del

Pre

dic

tio

n

µg/kg OC

DEHP 230000 98500

Maximum Average

SQS=47,000 µg/kg

Comparison of Treated CSO and Norfolk Drain Discharges

BIS(2-ETHYLHEXYL)PHTHALATE

0

1

2

PO

UN

DS

PE

R Y

EA

R

DEHP (lbs/yr)

DEHP (lbs/yr) 0.03 1.6

Tunnel-treated CSO Norfolk Drains

Conclusions Treated CSO discharges at Norfolk will not

recontaminate sediments Recontamination of sediments with DEHP may

occur due to untreated discharges from Norfolk drains