Outline

1. Brief overview of multibox model (John)

2. Results of independent testing (Katherine)

3. Next steps for development (?) (John)

4. Overview of planned uncertainty testing (Tom)

Multibox PCB Model

CFWG Meeting

September 15, 2005

• Multibox ?– 50 Model Boxes

– 2 Vertical Layers

– 100 cm of sediments

• Physics Forced by:– Tides at Golden Gate

– ‘Delta Outflow’

– Local Tributaries

– Wind, Rain

PCBs in shallow sediments Version 2.0b

PCBs in channel sediments Version 2.0b

Independent Testing of SFEI’s Multi-box Model for PCB Fate and

Transport

Prepared by Tetra Tech, Inc.

Lafayette, CA

September 15, 2005

Next Steps for Model Development

Recommendations from independent testing:

• Documentation is outdated– Provide documentation sufficient to proceed with testing without

creating an extra report.• Include updating equations from draft report• Eventually document everything in a draft technical report

• Review and modify historic input data– Data are available, easy to update inputs

• Add variability to forecast data– Investigate applicability of alternative methods for generation of

forecast inputs

• Investigate sea level rise– Interesting question, out of the scope of this project

• Investigate impact of elevated SSC in Lower South Bay on PCB transport– Contribution to PCB mass transport is likely small,

though an investigation is warranted– Prefer to leave sediment model development to

Schoellhamer et al.

• Evaluate spin-up period. Investigate alternative initialization.– Significant consequences for PCB transport– Artifact of sediment model calibration– Lack data to change PCB initial conditions

• Include additional congeners– Yes

Recommendations from independent testing:

• Can Model / Data comparison be improved?– How good does hindcast need to be?– Probabilistic comparison may be useful– Loading function may be cause of overestimate

• Calibration (of loading curve?) Loading Curve

Recommendations from independent testing:

Estimated Timeline

Create documentation 3-4 days

Review/modify input data 2-3 days

Elevated SSC in LSB 2-3 days

Adjust spin-up period 4-5 days **

Additional congeners 2 days

Improve hindcast (calibration) 5+ days **

Total: 18-22 days

10-12 daysRed indicates steps ‘critical’ to continue with testing

Uncertainty Testing