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PA-AWRA Conference October 22, 2004

Modeling to Support Development of TMDLs for PCBs in the Delaware Estuary. PA-AWRA Conference October 22, 2004. Key Themes. All TMDLs are not created equal. Models are essential for complex pollutants in water bodies with multiple point and non-point sources.

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PA-AWRA Conference October 22, 2004

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  1. Modeling to Support Development of TMDLs for PCBsin the Delaware Estuary PA-AWRA ConferenceOctober 22, 2004

  2. Key Themes • All TMDLs are not created equal. • Models are essential for complex pollutants in water bodies with multiple point and non-point sources. • They allow a better understanding of the sources, processes, and interactions influencing pollutant transport and fate. • Facilitate decisions on the relative importance of source categories and reduction strategies. • TMDLs for complex pollutants like PCBs should be developed in stages.

  3. Factors Contributing to the Complexity of PCB TMDLs • PCBs are a class of chemicals. • Human health criteria must be updated. • PCBs are hydrophobic with significant interaction with sediments. • Sources of PCBs include contaminated sites, NPDES discharges, CSOs, air deposition, tributaries, non-point source runoff, ocean and C&D Canal and sediments. • The Delaware Estuary is a complex water body with significant tidal influence.

  4. Zone Designations for the Delaware Estuary

  5. PCBs • Man-made organic chemicals with a biphenyl base structure and 209 possible chlorine substitution patterns. • Terminology: Aroclors, congeners, homologs. • Properties: Hydrophobic, tend to accumulate in sediments and tissues.

  6. Modeling Objectives • Gain understanding: • Determine PCB load-response relationships. • Determine principal controlling processes. • Address management questions: • Determine PCB TMDL for each zone. • Allocate TMDLs among sources. • Assess the impact of load reduction strategies.

  7. Challenges for this Effort • Complexity of system • Tidal • Multiple PCB source categories - including 142 individual NPDES discharges. • Limited available data • Loadings • Ambient concentrations • Ambitious schedule • Court mandates • Administrative agreements

  8. Principal Mass Loadings and Fluxes

  9. Delaware River PCB Model (DELPCB) • Modified version of DYNHYD5/TOXI5 • EPA-supported and widely used for toxic chemical TMDLs and contaminated sediments. • Model formulations/code extensively tested and assessed with observations at numerous sites. • Builds upon modeling work at other sites: • Kalamazoo River RI/FS • New York Harbor CARP Model • Green Bay Mass Balance Study • Upper Hudson River RI/FS • Fox River RI/FS

  10. Delaware River PCB Model (DELPCB) • Represents water column and sediments • One-dimensional in longitudinal • 87 spatial segments • Time-variable • Hydrodynamics • Tidal heights • Chloride mass balance • Organic carbon sorbent dynamics • Particulate carbon (biotic and detrital) • Dissolved organic carbon • Penta-PCB homolog

  11. Calibration Approach • Short-term Calibration • Running Calibration Approach - 19 months (September 2001 to March 2003) • Emphasis on water column concentrations • Suite of different model calibration metrics • Decadal-scale consistency check • 74 years (1930 to 2003) • Emphasis on surficial sediments and dated cores • Significant uncertainty in the historical loading trend.

  12. Spatial Plot: Relative Impact of the Boundary Conditions:Median Values:BC = 100mg/l for Mouth of the Bay, C&D, Schuylkill, and/or Trenton

  13. Penta-PCB Load by Source CategorySeptember 1, 2001 through March 31, 2003

  14. Total and Dissolved Penta PCBs (Upper and Middle Estuary)

  15. Decadal Scale Simulationfor penta-PCB in Water Column

  16. Atmospheric gas phase PCB concentrations

  17. Summary of Approachfor Stage 1 TMDLs • Utilize both a conservative chemical (chloride) and the penta-PCB models that cycle inputs from the period February 1, 2002 to January 31, 2003. • Calculate annual median TMDL loadings to be consistent with both the model simulations and the 70 year exposure for human health criteria. • Extrapolate penta-PCB results to Total PCBs.

  18. Ratio of Penta-PCBs toTotal PCBs in Ambient Samples

  19. Key Findings • The principal sources of PCB loadings are contaminated sites, non-point sources and point sources. • The atmosphere is currently a sink for PCBs, but will be a significant PCB source as criteria are approached. • PCB loadings at head of tide (Trenton) have a significant influence in the Delaware Estuary. • Water column PCBs are influenced by ongoing watershed sources and legacy contamination in the sediments.

  20. Summary points • Model for PCBs is developed, calibrated and is scientifically credible. • Model was used to develop Stage 1 PCB TMDL, but Stage 2 is necessary to address uncertainties. • TMDLs will be based upon the most stringent water quality criteria: revised human health or wildlife criteria. • TMDLs will be established by summing the 10 PCB homologs. • The TMDLs will be developed using homolog- specific PCB water quality models. • Model can be extended to other contaminantsand to other watersheds.

  21. Contact Information Thomas J. Fikslin Head, Modeling & Monitoring Branch Delaware River Basin Commission West Trenton, NJ 08628 609-883-9500, x253 Thomas.Fikslin@drbc.state.nj.us Reference Reports: www.drbc.net

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