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Completing the SF Bay Mercury TMDL Carrie Austin SF Bay Water Board

Completing the SF Bay Mercury TMDL Carrie Austin SF Bay Water Board. Overview of Water Board Response. More Stringent Requirements for Wastewater New Water Quality Objectives Actions to clarify and improve implementation. Mercury Loads and Allocations. Wastewater [Hg] T “Trigger”.

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Completing the SF Bay Mercury TMDL Carrie Austin SF Bay Water Board

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  1. Completing the SF Bay Mercury TMDLCarrie AustinSF Bay Water Board

  2. Overview of Water Board Response • More Stringent Requirements for Wastewater • New Water Quality Objectives • Actions to clarify and improve implementation

  3. Mercury Loads and Allocations

  4. Wastewater [Hg]T “Trigger” • Standard NPDES permit calculation • Performance based: Mean + 3 SDs • About 99th percentile • Triggers for “advanced” & “secondary”

  5. Wastewater Individual WLAs • Calculated differently • Performance-based • 99% UCL on the Mean • Sum of Individual WLAs = “group trigger”

  6. Revised Wastewater Allocations Current allocations(kg/year) Revisedallocations 17 11? 99% UCL on the mean = 20 kg/yr annual average

  7. New Water Quality Objectives • Vacate water column objective0.025 ug/L4-day average • Establish two new fish tissue objectives:0.2 ppm larger fish0.03 ppm smaller prey fish Second fish tissue objectives in California – Clear Lake was first.

  8. Timeline and Next Steps • Release documents for public review mid-March • Public review period through April • Water Board action in June

  9. Guadalupe River Watershed Mercury TMDL Carrie Austin SF Bay Water Board

  10. Debut: GRW Hg TMDL Public Comment period closes 06/30/06 Documents available from: http://www.waterboards.ca.gov/sanfranciscobay/guadaluperivermercurytmdl.htm • TMDL Project Report Jan06 • Final Conceptual Model Report May05 • Derivation Numeric Wildlife Targets Apr05

  11. TMDL Overview • Problem • Sources • Targets • Allocations • Implementation

  12. Problem: Bioaccumulation Summary of 2004 Fish Sampling Results Citation: Figure 3-25 Final Conceptual Model Report(Tetra Tech 2005c)

  13. Sources • Mining Waste • Urban Runoff • Atmospheric Deposition • Natural Hg in soil Citation: figure by Tetra Tech

  14. Mining Waste Erodes into: Predominantly Alamitos Creek & Lake Almaden Canal from Almaden  Calero Reservoir Jacques Gulch into Almaden Reservoir Small area into Guadalupe Reservoir Remainder into Guadalupe Creek

  15. TARGETS

  16. Numeric Targets = “Fishable”

  17. Achievable Targets • Ore – underground • Cinnabar outcrops on Mine Hill • Cinnabar nuggets in Deep Gulch • No deep lakes Hypothesis: low mercury bioaccumulation pre-mining

  18. ALLOCATIONS

  19. “Impoundments” Impoundments are engineered structures that pond water. • dams (i.e., reservoirs and artificial lakes), • flood control structures, • other engineered features (such as drop structures), and • non-native invasive vegetation that ponds water

  20. Fish in Reference Reservoir Fishable: • 40-cm Largemouth bass: 0.6 ppm < 0.66 ppm TL4 human health target • Age-1 Largemouth bass: 0.09 ppm @ 89 mm length, equals 0.045 in TL3 < 0.05 ppm wildlife target

  21. Allocation: Hypolimnion MeHg

  22. Downstream Implications Figure 6.7 Dissolved Methylmercury Below Reservoirs, July 2003 Citation: Figure 5-10 Final Conceptual Model Report (Tetra Tech 2005)

  23. Lower [Hg]sed Lower [Hg]fish

  24. Allocations based on Reference Reservoir

  25. IMPLEMENTATION

  26. Start in Headwaters: New Almaden 0.1 ppm mercury in erodable soil finestransportedin runoff BMPs for erosion control w/in 10 yrs

  27. Impoundment MeHg Production Thermal stratification (natural, good) Low DO in hypolimnion SRB produce HS-which dissolves mining waste SRB produce MeHg

  28. Is Oxygen the Solution to MeHg? Thermal stratification (natural, good) oxygenated hypolimnion

  29. Dissolved Hg Hypotheses • Wet season:HgDiss transported in storm water from mining waste quickly attaches to particulates; erosion control sufficient. • Dry season:main concern with HgDiss is dry season dissolution of mining waste under anoxic conditions

  30. Summary Figure S-1 Solving the Mercury Problem Citation: figure prepared by Tetra Tech

  31. Comments on Guad Hg TMDL Public Comment period ends June 30send to:Carrie AustinSF Bay Water Board1515 Clay Street, #1400Oakland, CA 94612 caustin@waterboards.ca.gov

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