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Recontamination of Waterway Cap Thea Foss Waterway (What has been learned?)

Recontamination of Waterway Cap Thea Foss Waterway (What has been learned?). Matthew G. Dalton (Dalton, Olmsted & Fuglevand, Inc.). Particulate Physical t urbidity Nutrients e .g. phosphorus Chemicals e .g lead, PAHs, PCBs. Types of Stormwater Pollution. Dissolved Biologic

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Recontamination of Waterway Cap Thea Foss Waterway (What has been learned?)

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  1. Recontamination of Waterway CapThea Foss Waterway(What has been learned?) Matthew G. Dalton (Dalton, Olmsted & Fuglevand, Inc.)

  2. Particulate Physical turbidity Nutrients e.g. phosphorus Chemicals e.g lead, PAHs, PCBs Types of Stormwater Pollution • Dissolved • Biologic • e.g. fecal coliform • Nutrients • e.g. nitrogen • Chemicals • e.g. zinc, benzene, solvents Dalton, Olmsted & Fuglevand, Inc.

  3. Metals (Kd l/kg) Copper - 22 Zinc - 62 Total Cr – 1,000 Lead – 10,000 Stormwater Sediment ContaminationHydrophobic/Particulate Contaminants of Most Concern • Organics (koc ml/g) (organic carbon-water) • Benzene - 22 • PCE (PERC) - 265 • Naphthalene – 1,191 • Bis(2-ethylhexyl) phthalate – 111,123 • Aroclor 1260 – 822,422 Partitioning Coefficients Source: WAC 173-340-900 Dalton, Olmsted & Fuglevand, Inc.

  4. Sediment/ Stormwater Metals PAHs Phthalates PCBs Pesticides Contaminants of Concern(mostly hydrophobic in nature) • DNAPL Seep • Visual Sheens • PAHs Dalton, Olmsted & Fuglevand, Inc.

  5. Site Vicinity Dalton, Olmsted & Fuglevand, Inc.

  6. Remedy Features Dalton, Olmsted & Fuglevand, Inc.

  7. Hybrid Cap Dalton, Olmsted & Fuglevand, Inc.

  8. Post Remedy Conditions 4,600 Acres Stormwater Outfalls 181 Acres 45 Acres Sheet Pile Wall Dalton, Olmsted & Fuglevand, Inc.

  9. Twin 96” OutfallsHead of Thea Foss Waterway

  10. Monitoring Approach Dalton, Olmsted & Fuglevand, Inc.

  11. Monitoring February 2004 to May 2009 (Five Years) What Happened? Dalton, Olmsted & Fuglevand, Inc.

  12. Sediment Accumulation(2004 to 2009) Dalton, Olmsted & Fuglevand, Inc.

  13. Surface Sediment Above Cap FINES CONTENT ORGANIC CARBON Cap <4% Cap <0.5% Dalton, Olmsted & Fuglevand, Inc.

  14. Surface Sediment Above Cap SQO = 17,000 ug/kg Dalton, Olmsted & Fuglevand, Inc.

  15. Surface Sediment Above Cap SQO = 1,300 ug/kg Dalton, Olmsted & Fuglevand, Inc.

  16. Stormwater Relationship(in sediment) Dalton, Olmsted & Fuglevand, Inc.

  17. Historic Stormwater Relationship 2004 2006 1984

  18. Sediment Trap – Sediment Comparisons Dalton, Olmsted & Fuglevand, Inc.

  19. Sediment Trap – Early Warning Sediment Sample Comparisons – 2008 Data Dalton, Olmsted & Fuglevand, Inc.

  20. Conclusions • Bottom-up and top-down monitoring is working. Early warning samples were successful in identifying recontamination. • Sediment core data, suite of contaminants detected, correlations and trends indicate recontamination has occurred from top-down sources, primarily stormwater. • In-line (pipe end) sediment traps were effective in providing data to assess stormwater recontamination. • Monitoring of hydrophobic (particulate) recontamination is most effective in bottom sediment of the receiving water body. Dalton, Olmsted & Fuglevand, Inc.

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