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Lester McKee and Alicia Gilbreath Sources Pathways and Loadings Workgroup December 8, 2008

Investigating water quality in Zone 4 Line A watershed to understand pollutant sources and pathways affecting runoff. Report includes rainfall-runoff analysis, contaminant measurements, and recommendations for future studies.

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Lester McKee and Alicia Gilbreath Sources Pathways and Loadings Workgroup December 8, 2008

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  1. Item #2a Small Tributaries Loading Study #2:Zone 4 Line A, Cabot Blvd. Hayward Year 1 – Draft FINAL report Lester McKee and Alicia Gilbreath Sources Pathways and Loadings Workgroup December 8, 2008

  2. Item #2a Choice of watershed to study • TMDL reports encourage further development of loading information • Z4LA chosen because it: • Contrasts in size to Guadalupe River • Land use • Climate • Geology and slope

  3. Item #2a Location • Area: 4.47 km2 Industrial: 38% • Commercial: 26% Residential: 33% Sampling location

  4. Item #2a Channel

  5. Item #2a Field equipment

  6. Item #2a Field sampling for contaminants

  7. Item #2a Measurement of discharge

  8. 21 storm events cumulative rainfall = 270 mm (10.6 in) 1.6 year return %77 % of average (45 y record at 50dly to the south Item #2a Results – Rainfall and runoff

  9. Item #2a Results – Suspended sediment

  10. Item #2a Scatter plots

  11. Item #2a Spearman partial correlations – effect of SSC removed • Hg not correlated with Cr, Ni, Se despite common geologic origins

  12. Item #2a Comparisons to CA soils 5 7% 00

  13. All <10% PCB 110/115, 129/138/160/163, 153/168, 180/193 Item #2a Results – Trace organics

  14. BDE 47, 99, 209 (73-88%) Item #2a PBDEs

  15. Item #2a Loads of Organics • Organic carbon: <1% SSC (Guadalupe 0.5-1.1%) • PCB concentrations normalized to sediments (0.13 mg/kg) were 10x greater than found in the Bay • PBDE loads were 2.8 x PCB loads • PAH loads, despite abundant sources lower than PCBs/PBDEs, DDT and similar to chlordanes

  16. Item #2a Z4LA concentration comparisons • Local concentration data • Guadalupe, Coyote, San Pedro storm drain • Hg: Z4LA = Coyote within range of San Pedro << Guadalupe • PCB: Z4LA = Guadalupe >Coyote (*dry year) • PBDE / DDT / chlordane, dieldrin similar trends to PCBs

  17. Item #2a MeHg • SSC proxy to flow • Dilution during high flows • More production during low flows • Similar particle concentrations to wetlands (Heim et al., 2007)

  18. San Francisco Estuary Institute Item #2a Which and how many watersheds should be sampled? Export of POC during climatic years with ~70% mean annual runoff (units: micrograms per square meter (µg/m2) unless otherwise specified

  19. Regional loads estimates(Flow method)

  20. Regional loads estimates(Sediment method) • Discount estimate based on Davis et al. (2000) sediment load: we are quite certain it is too low. • Hg: 84 – 91 kg is less than TMDL estimate (160 kg) • PCB: 13 – 26 kg is similar to TMDL estimate (20 kg) • PBDE: 37 – 79 kg is similar to Oram et al (2008) estimate (60 kg)

  21. Recommendations • Given Z4LA was sampled under dry conditions in the first year sampling continue for either 3-4 years or until storms of <5 year return are sampled • Given regional load estimates are crude at best, effort should be made to: • Develop regional modeling capability • Gather sample a greater variety of land types specifically as input into models • Improve regional data set for MeHg and HgR in the context of “high leverage watersheds” • Given the unexpected similarity between watersheds for the trace organics, effort should be made to reject the hypothesis that imperviousness is more important than sources • An alternative hypothesis is that watershed scale is masking the source issue

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