Completing the SF Bay Mercury TMDL Carrie Austin SF Bay Water Board 2 Overview of Water Board Response More Stringent Requirements for Wastewater More Stringent Requirements for Wastewater New Water Quality Objectives New Water Quality Objectives Actions to clarify and improve implementation Actions to clarify and improve implementation 3 Mercury Loads and Allocations SOURCE CATEGORY EXISTING LOAD (kg/yr) ALLOCATION (kg/yr) Bed Erosion Central Valley Watershed Urban Runoff Guadalupe River Mining Legacy 922 Atmospheric Deposition 2727 Rural Runoff 2525 Wastewater20 20 14? Dredging and Disposal net loss net loss 0 ambient concentration TOTAL1, 700? 4 Wastewater [Hg] T Trigger Standard NPDES permit calculation Standard NPDES permit calculation Performance based: Mean + 3 SDs Performance based: Mean + 3 SDs About 99 th percentile About 99 th percentile Triggers for advanced & secondary Triggers for advanced & secondary 5 Wastewater Individual WLAs Calculated differently Calculated differently Performance-based Performance-based 99% UCL on the Mean 99% UCL on the Mean Sum of Individual WLAs = group trigger Sum of Individual WLAs = group trigger 6 Revised Wastewater Allocations Municipal advanced -20% Municipal secondary -40% Industrial3? Analysis pending Total2014? Current allocations (kg/year) Revised allocations 17 11? 99% UCL on the mean = 20 kg/yr annual average 7 New Water Quality Objectives Vacate water column objective ug/L 4-day average Vacate water column objective ug/L 4-day average Establish two new fish tissue objectives: 0.2 ppm larger fish 0.03 ppm smaller prey fish Establish two new fish tissue objectives: 0.2 ppm larger fish 0.03 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 Release documents for public review mid-March Public review period through April Public review period through April Water Board action in June 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:bay/guadaluperivermercurytmdl.htmbay/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 Citation: Figure 3-25 Final Conceptual Model Report (Tetra Tech 2005c) Problem: Bioaccumulation Summary of 2004 Fish Sampling Results 13 Citation: figure by Tetra Tech Sources Mining Waste Mining Waste Urban Runoff Urban Runoff Atmospheric Deposition Atmospheric Deposition Natural Hg in soil Natural Hg in soil 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 Table 5.3 Fish Targets (ppm methylmercury, wet weight) Protection of Wildlife Protection of Human Health TL3 Fish 50 150 mm TL3 Fish 150 350 mm Typical Size and Species of Fish Consumed 0.05 ppm0.10 ppm0.3 ppm USFWS calculation USEPA MeHg criterion 17 Achievable Targets Ore underground Cinnabar outcrops on Mine Hill Cinnabar outcrops on Mine Hill Cinnabar nuggets in Deep Gulch 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), dams (i.e., reservoirs and artificial lakes), flood control structures, flood control structures, other engineered features (such as drop structures), and other engineered features (such as drop structures), and non-native invasive vegetation that ponds water 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 40-cm Largemouth bass: 0.6 ppm < 0.66 ppm TL4 human health target Age-1 Largemouth bass: mm length, equals in TL3 < 0.05 ppm wildlife target Age-1 Largemouth bass: mm length, equals 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 Impoundment Methylmercury Allocation 3.0 ng/l (parts per trillion) MeHg seasonal maximum in the hypolimnion 3.0 ng/l (parts per trillion) MeHg seasonal maximum in the hypolimnion of 3 reservoirs and Almaden Lake Mining Waste Total Mercury Allocations 0.1 ppm mercury (annual median, dry weight) in erodable soil finestransported 0.1 ppm mercury (annual median, dry weight) in erodable soil fines transported from the New Almaden Mining District (see report regarding 0.2 ppm mercury) 25 IMPLEMENTATION 26 Start in Headwaters: New Almaden 0.1 ppm mercury in erodable soil fines transportedin runoff 0.1 ppm mercury in erodable soil fines transported in 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 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 30 send to: Carrie Austin SF Bay Water Board 1515 Clay Street, #1400 Oakland, CA