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INCORPORATING MULTIPLE LINES OF EVIDENCE INTO SEDIMENT QUALITY OBJECTIVES. Stephen B. Weisberg Southern California Coastal Water Research Project. WHAT IS MLOE?. POSSIBLE FLAWS WITH RELIANCE ON INDIVIDUAL INDICATORS Benthos Physical disturbance (anchor, dredging) Oxygen stress Chemistry

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incorporating multiple lines of evidence into sediment quality objectives

INCORPORATING MULTIPLE LINES OF EVIDENCE INTO SEDIMENT QUALITY OBJECTIVES

Stephen B. Weisberg

Southern California Coastal Water

Research Project

what is mloe
WHAT IS MLOE?

POSSIBLE FLAWS WITH RELIANCE ONINDIVIDUAL INDICATORS

  • Benthos
    • Physical disturbance (anchor, dredging)
    • Oxygen stress
  • Chemistry
    • Paint chip
    • Tar ball
  • Toxicity
    • Confounding factors (ammonia)
    • Agitation enhanced bioavailability
  • A recognition that no single indicator type is sufficient to assess sediment quality
  • Confidence increases when we can demonstrate both exposure and effect
  • There is also some scientific uncertainty associated with each line of evidence
    • Measurement error
    • Interpretation error (e.g. Benthic indices)
what is mloe1
WHAT IS MLOE?
  • A recognition that no single indicator type is sufficient to assess sediment quality
  • Confidence increases when we can demonstrate both exposure and effect
  • There is also some scientific uncertainty associated with each line of evidence
    • Measurement error
    • Interpretation error (e.g. Benthic indices)
challenge
CHALLENGE
  • MLOE has not yet found its way into sediment quality criteria
    • Mostly used in site-specific assessments
    • Case-specific reliance on “Best Professional Judgment”
  • Challenge is to create a consistent MLOE application
    • Primary users will often be inexperienced engineers
    • Need a more rigorous structure than BPJ
issues
ISSUES
  • For what purpose will MLOE approach be used?
  • What are the end points (beneficial uses) of interest?
  • Which indicators will be used to address each MLOE end point?
  • How will these indicators be weighted in a scoring system ?
    • Will scoring be ordinal or binary?
purpose
PURPOSE
  • Primary purpose: To determine if beneficial uses at a station are impaired
  • Secondary: Programmatic applications of station criteria
    • Waterbody evaluation (303d listings)
    • Discharge compliance decisions
    • Local cleanup levels
    • Dredge material permitting
  • We plan to provide guidance toward application process
    • Water code vs. site-specific decisions
issues1
ISSUES
  • For what purpose will MLOE approach be used?
  • What are the end points (beneficial uses) of interest?
  • Which indicators will be used to address each MLOE end point?
  • How will these indicators be weighted in a scoring system ?
    • Will scoring be ordinal or binary?
beneficial use protection categories
BENEFICIAL USE PROTECTION CATEGORIES
  • Aquatic life (Infaunal) effects
  • Human health effects
  • Fish and wildlife effects
  • MLOE will be used within each, but independent assessments will be conducted for each beneficial use
which indicators
WHICH INDICATORS?
  • Infaunal effects
    • Sediment chemistry
    • Sediment toxicity
    • Benthic infaunal assemblage
  • Human health
    • Sediment chemistry
    • Fish/bivalve tissue chemistry
  • Fish/wildlife
    • Sediment chemistry
    • Tissue exposure
    • Biological effects
mloe scoring infaunal effects
MLOE SCORING – INFAUNAL EFFECTS
  • At least two legs of the triad are necessary to conclude impairment
    • Need to demonstrate both exposure and effect
mloe scoring infaunal effects1
MLOE SCORING – INFAUNAL EFFECTS
  • At least two legs of the triad are necessary to conclude impairment
    • Need to demonstrate both exposure and effect
  • Ordinal scoring
    • Too much uncertainty to create binary thresholds
    • There is a desire to prioritize among sites
    • There is also a desire to assess trends
score each indicator from zero to three
SCORE EACH INDICATOR FROMZERO TO THREE

0 – Reference condition

1 – Slight deviation from reference (possibly defined by measurement error)

2 – Moderate effect

3 – Severe effect

outcomes at the station level
OUTCOMES AT THE STATION LEVEL
  • Unimpaired (0 – 1 points)
  • Likely unimpaired (2 – 3 points)
  • Likely impaired (4 – 6 points)
  • Clearly impaired (7 – 9 points)
devil is in the details
DEVIL IS IN THE DETAILS
  • Scoring multiple metrics within an indicator class
    • e.g. Multiple toxicity tests at a site
    • e.g. Incorporating both empirical and EqP approaches
  • Less than three legs of the triad measured
  • Others you would like me to address?
multiple metrics within a class
MULTIPLE METRICS WITHIN A CLASS
  • Average score
  • Worst score
    • They each measure different things
  • Prioritizing among tests
    • Most sensitive test
    • Least sensitive test
    • “Best” test
  • Highest quality data
  • Some combination of frequency and severity
devil is in the details1
DEVIL IS IN THE DETAILS
  • Scoring multiple metrics within an indicator class
    • e.g. Multiple toxicity tests at a site
    • e.g. Incorporating both empirical and EqP approaches
  • Less than three legs of the triad measured
  • Others you would like me to address?
what if only two lines of evidence are available
WHAT IF ONLY TWO LINES OF EVIDENCEARE AVAILABLE?
  • Looking for a combination of concordance and magnitude
  • Unimpaired: No effect from either indicator
  • Likely unimpaired: Small effect with no indicator, but no effect for the other
  • Unclear: Large effect with one indicator but no effect for the other
  • Likely impaired: Some effect for both indicators
  • Clearly impaired: High effect for both indicators
what if there is only one line of evidence available
WHAT IF THERE IS ONLY ONE LINE OF EVIDENCE AVAILABLE?
  • Different circumstance than having three lines of evidence where only one line shows an effect
  • Philosophy is still the same: Need demonstration of both exposure and effect
    • Want to avoid false positives
  • Classify stations that score a 3 as “Presumed Impaired”
    • Not used initially; Would revert to “likely impaired” if no new data are collected within three years
    • Want to guard against false negatives
moving from station assessment to system assessment 303d example
MOVING FROM STATION ASSESSMENT TO SYSTEM ASSESSMENT: 303d EXAMPLE
  • Impairment of a station does not equate to system impairment
  • Probably few (no?) systems without some anthropogenic impact
  • There is assessment uncertainty at the station level
    • Measurement variability
    • Assessment tool error
  • Present State Board approach defines impairment relative to frequency of station/sample exceedances in waterbodies with the least human influence
    • That approach can work here
establishing frequency threhold for defining system impairment
ESTABLISHING FREQUENCY THREHOLD FOR DEFINING SYSTEM IMPAIRMENT
  • Identify systems (or subsystems) that are least influenced
  • Use project data base to create a frequency plot
    • Select a frequency threshold based on the plot
    • Might also use site replicability information
    • Might also incorporate a magnitude component to the threshold
establishing frequency threhold for defining system impairment1
ESTABLISHING FREQUENCY THREHOLD FOR DEFINING SYSTEM IMPAIRMENT
  • Identify systems (or subsystems) that are least influenced
  • Use project data base to create a frequency plot
    • Select a frequency threshold based on the plot
    • Might also use site replicability information
    • Might also incorporate a magnitude component to the threshold
  • Particularly need your input at this stage
    • Defining reference systems
    • Interpreting frequency plot
    • Determining need for habitat specific thresholds
some 303d devil in the details
SOME 303D DEVIL IN THE DETAILS
  • How many stations are necessary to classify a waterbody?
  • What if stations are non-random and non-representative of the system?
some 303d devil in the details1
SOME 303d DEVIL IN THE DETAILS
  • How many stations are necessary to classify a waterbody?
  • What if stations are non-random and non-representative of the system?
  • We will need to provide guidance on such issues
303d product from this project
303d PRODUCT FROM THIS PROJECT
  • Guidance document describing recommended approach
    • Point out consistency/differences from State Board approach for other stressors
  • Includes graphics that describe analytical results
    • Frequency plot from reference sites
    • Station repeatability information
  • Ultimate 303d decisions made by other individuals
    • So far, they find this approach agreeable
human health
HUMAN HEALTH
  • Both legs (tissue chemistry, sediment chemistry) necessary to conclude impairment
    • Linkage between exposure and effects even more necessary than for benthic effects
  • Tissue chemistry thresholds are straightforward
    • State has fishery closure levels
  • Sediment chemistry thresholds are less clear
    • Will likely differ from infaunal effects thresholds
    • We are exploring both empirical and mechanistic models
special issues human health
SPECIAL ISSUES – HUMAN HEALTH
  • Can we do a station assessment?
    • Exposure will generally be system-specific rather than station-specific
  • Are all species acceptable?
    • Resident vs. migratory
    • Indicator vs. human consumed species
fish wildlife effects
FISH / WILDLIFE EFFECTS
  • Will probably require three lines of evidence as necessary to conclude impairment
    • Sediment chemistry, tissue chemistry, biological effects
    • Greater physical dislocation between sediment and effect
  • Thresholds for each line are less well developed than for other modes of effect
  • Mechanistic modeling becomes increasingly important
    • Also increasingly difficult
  • Least amount of data
    • Most applications will need to be based on first two modes of effect
    • Our goal is to develop framework for the future
timeline
TIMELINE
  • Draft sediment quality objectives due August 2005
  • Workplans for individual indicator elements already prepared and studies begun
  • We will prepare a MLOE integration workplan following this meeting
    • We will ask the Scientific Steering Committee to review it next
  • Looking for your input today