Mercury TMDLs in the Central Valley of California Implementation Issues

1. Mercury TMDLs in the Central Valley of CaliforniaImplementation Issues Tom Grovhoug, Larry Walker Associates January 19, 2005

2. Overview of Mercury Problem • Fish exceed target levels in tissue • Sacramento Valley is mercury enriched • Valley is historic freshwater marsh • Wetlands in river system and Delta provide sites for methylation – CALFED is adding wetlands • Multi-million dollar research underway to understand mercury processes and controls in the system

3. Map of TMDL Watersheds

4. Mercury TMDL Approaches • Reduce current mercury loads in proportion to the amount of mercury excess in fish tissue • Implement load reduction through WLAs and LAs • Monitor and adjust WLAs and LAs in future if fish tissue targets not achieved

5. Implementation Issue No. 1 Control of mercury in fish may not be attainable through control of existing loads • Legacy mercury in the active sediment layer in the system provides a reservoir of mercury for methylation • Local environments and food web characteristics likely control levels in fish

6. Mercury Conceptual Model

7. Are Load Controls the Answer? • Current load vs Total Hg concentrations • Total Hg concentrations vs Hg in fish

8. Watershed-wide: Significant Correlation to THg?

9. Implementation Issue No. 2 Little flexibility in fish tissue targets, which are being adopted as WQ objectives • Targets may not ever be attainable • Use attainability issues – were targets attained in 1975? • Triennial review as adaptive response? – NOT EFFECTIVE

10. Implementation Issue No. 3 Ongoing Focus on NPDES Discharges • WLAs have immediate regulatory impact on point source dischargers as WQBELs – additional removals through treatment controls are not cost-effective • Point sources are de minimus contributors to total mercury loads

11. Implementation Issues – Summary • What if load is not a controlling variable? • What if targets are not attainable? • How will new knowledge about mercury fate, transport and bioaccumulation be considered in TMDLs?

12. Recommended Adaptive Management Approach Given the high degree of uncertainty: • Clearly acknowledge that uncertainties exist in TMDL load reduction plan • Focus load reduction on biggest uncontrolled sources • Avoid major impacts on minor sources

13. Recommended Adaptive Management Approach • Build in commitment/mechanisms to allow new information to impact direction of TMDL implementation • Emphasize risk reduction through identification of and communication with fishing populations • Initiate program to assess attainability of fish tissue targets based on historic and future conditions (i.e. wetlands) (UAA)

14. Mercury Offsets – TMDL Issues • Three Offset projects under consideration • Settling Basin improvements • Abandoned Mercury Mine remediation • Streambank erosion control – mercury enriched soils due to mining, geothermal

15. Mercury Offsets Streambank Restoration Mine Site Settling Basin

16. TMDL Issues with Offset Projects • Proposed WLAs • Abandoned mercury mine – 95% reduction • Mercury enriched stream – 70% reduction • Settling Basin - ?? • PROBLEM: Don’t leave opportunity for viable offset projects • FACT: None of three projects will likely occur in the absence of offsets

17. Adaptive Implementation • SOLUTION: Allow third party offsets to occur through TMDL implementation language • e.g. place WLA on responsible parties but allow other parties to do projects to achieve the WLA reductions and still receive an offset credit

19. Mercury Conceptual Model 5 Multiple Source Types and Locations Fish Tissue 1 4 [Hg] in Water Bioaccum-ulation 2 Transport 3 Ambient [MeHg] Transformation

20. Mercury Conceptual Model Conceptual Model of Mercury Transformation and Accumulation in the Food Chain

21. Potential Linkage Relationships Linear 1:1 Non-linear Linear Other None

22. Individual Site: Mid Bear Creek • Non-linear • Negative slope • R2<0.01

23. Harley Gulch Data for BAF BAF= 1,021,865