Methylmercury TMDL

1

• Methylmercury TMDL Implementation Plan for
  theSacramento-San Joaquin RiverDelta Estuary
• 2006 National Monitoring Conference
• Michelle Wood

2
Outline

• TMDL Primer
• Why a MeHg TMDL?
• The Delta MeHg TMDL

3
Federal Clean Water Act Section 303(d)

• Requires Total Maximum Daily Loads for waterways
  that dont meet WQ standards even after
  controlling point sources

4
Definition of TMDL
The amount of a pollutant that a water body can
receive and still meet water quality standards
(assimilative capacity)
5
TMDL Elements

• Problem statement
• Numeric target
• Source analysis
• Linkage analysis
• Allocations

6
A TMDLWithout ImplementationGhost Regulation

• State Porter-Cologne Water Quality Control Act
• Requires Regional Boards to implement TMDLs
• TMDL implementation plans are amended into State
  water quality plans (Basin Plans)

7
Central Valley Mercury TMDLs
8
The Delta
gt1100 mi waterways Drains 1/3 of CA
ReduceCentral Valley Mercury Outflows by 110
Kg/yr
9
Methylmercury

• Most toxic form of mercury (a potent
  neurotoxicant)
• Sulfate-reducing bacteria convert mercury to MeHg
• gt90 mercury in top trophic level fish is MeHg
• Exposure to MeHg is through consumption of fish
  shellfish

10
MeHg Bioaccumulates
Delta Water Largemouth Bass1 6,500,000
0.1 ng/l
11
(No Transcript)
12
Concerns about Focusing Control Program on Only
Inorganic Hg

• Millions of kilograms released to waterways by
  historic mining
• Much remains in channels may be untreatable
• Necessitate reliance on natural erosion as a
  reduction strategy
• May take centuries to wash the mercury from the
  waterways

13
Interrupt the Methylation Cycle

• Identify sources of MeHg
• Reduce methylation, and/or
• Reduce mercury sources that supply the
  methylation sources
• Shorten time to see fish tissue improvements from
  centuries to decades

14
Outline

• TMDL Primer
• Why a MeHg TMDL?
• The Delta MeHg TMDL

15
MeHg TMDL Elements

• Numeric target (a.k.a. WQO)
• Source analysis
• Linkage analysis
• Implementation plan with Allocations
• Monitoring and evaluation

16
Numeric Target

• Protect humans and wildlife
• Main factor fish consumption rates
• There are many options

17
Alternative Targets for Human Protection
18
Wildlife Targets
19
Recommended Targets

• Large TL4 Fish 0.24 ppm
• Humans 1 meal/week of mixed bag
• Protects piscivorous wildlife species
• Small TL3 Fish 0.03 ppm
• Protects wildlife consuming small fishwhere
  there are no big fish to monitor

Key Policy Question
20
MeHg Linkage

• Links targets to sources using the Delta-specific
  mathematical relationship between water and fish
  MeHg concentrations
• Determines a MeHg goal for ambient water

21
MeHg Sampling Locations Used in Linkage
TL4 Fish LMB Water
22
Weighted Average MeHg Levels in TL4 Fish (mg/kg)
23
Large-mouthBass Lengthvs. MeHgConc.
350 mm
Good method for evaluating long-term changes!
24
TL4 Fish WQO 350 mm LMB Hg Goal
25
350 mm LMB MeHg Goal Average Annual Water MeHg
Goal
26
RecommendedControl Program

• Control MeHg sources
• Control TotHg sources
• Reduce MeHg exposure to the fish eating public

27
5-Year Study Period

• Conduct studies to characterize control
  existing MeHg Hg concentrations and loads
• GOALS
• Address uncertainty in load estimates
• Develop technically economically feasible
  controls

28
Preliminary Municipal WWTP MeHg Monitoring Results
29
Mercury Offset Program

• Enable beneficial projectsto proceed even
  ifon-site mercury controls are not feasible

30
Timeline

• Within 30 years If implement MeHg controls,
  achieve measurable reductionsin fish tissue
  mercury
• 100 years Fully achieve WQO

31
Adaptive Implementation
Lower Fish MeHg
Action
32
Next Steps

• Report for scientific peer review
• Release draft BPA staff report
• Board Hearing in Fall/Winter 2006

33
AcknowledgmentsData, Methods Ideas

• SFEI, UCDavis, SRWP, CMPSF Water Board staff,
  DHS, OEHHA, DFG,Moss Landing Marine
  Laboratories, USGS, USFWS CALFED Mercury
  Program

34
Questions Discussion
35
(No Transcript)
36
Weighted Average MeHg Levels in TL4 Fish (mg/kg)
37
Average AnnualAmbient MeHg Levelsin Water(ng/l)
38
Delta MeHg SourcesAverage Annual Loads
39
San Joaquin Subregion Methylmercury SourcesTotal
Loading 478 g/yr
Agri-
Wastewater
Other
cultural
9
Tributaries
Lands
Inputs
77
5
23
Open
Water
Wetlands
Urban
4
4
1
40
Yolo Bypass Subregion Methylmercury SourcesTotal
Loading 1,000 g/yr
Wetlands
Other
39
Tributaries
Inputs
51
49
Open
Water
8
Agricultural
Lands
2