premises for developing and applying sediment quality objectives presented and (mostly) agreed upon...
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PREMISES FOR DEVELOPING AND APPLYING SEDIMENT QUALITY OBJECTIVES
Presented and (mostly) agreed upon during the October 27, 2004 meeting of the
Advisory Committee
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BASIC GOAL OF SQO APPROACH
• The primary goal is to determine if beneficial uses at a station are impaired
• Assessment of larger areas and/or waterbodies is a secondary goal
• The method for aggregating site-specific data for larger assessments may depend to some extent on the specific application (e.g., waterbody evaluation for 303d listing, dredging)
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UNDERLYING PHILOSOPHY
• At least two lines of evidence (or legs of the triad) are necessary to conclude a beneficial use is impaired
• One line of evidence alone is too subject to error
• Need to demonstrate both exposure and effect
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TECHNICAL APPROACH
• Develop quantitative scaling of indicator values
• Avoid simple binary thresholds
because:
• Thresholds are uncertain and less responsive to degrees of change or difference
• Scaled values are more useful for tracking trends
• Scaled values produce more meaningful assessments
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APPLICATION GUIDANCE
• Challenge is to create a consistent MLOE application
• Primary users will often be inexperienced engineers– BPJ not a realistic option
Goal is to develop a “cookbook” that:- Addresses specific applications
- Relates SQO to existing regulatory frameworks
- Clearly states how SQO should NOT be used
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BENEFICIAL USE PROTECTION CATEGORIES
• Aquatic life (Infaunal) effects
• Human health effects
• Fish and wildlife effects
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INDEPENDENT ASSESSMENT OF BENEFICIAL USES
• MLOE will be used within each beneficial use, and independent assessments will be conducted for each
• If any one beneficial use fails, the station fails, i.e., assessments are not additive across beneficial uses
• However, the aquatic life use will probably take precedence because of state of knowledge and availability of data
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GENERAL CONCERNS RELATED TO IMPLEMENTATION
• Need strategies and guidance for working with imperfect information, e.g., “burden shifting”
• Aggregating station-by-station assessments within context of specific regulatory frameworks
• Constraints on use of SQO, i.e., what they are NOT suited for
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SPECIFIC IMPLEMENTATION ISSUES
• Station assessment– Chemistry that is not bioavailable
– Imperfect information
– Burden shifting mechanism
– Incorporating other information
• 303d listing guidance– # stations needed for system assessment
– Toxic response but low chemistry and OK benthos
– Data collection after listing
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STATION: UNAVAILABLE CHEMICALS
• Hard to define and demonstrate potential for impact– Would depend on plausible mechanism(s)
– Possible long list of mechanisms
– Station might never get clean bill of health
• Margin of safety not clear if have elevated chemistry but OK toxicity and benthos
• Establish burden shifting incentives that foster further investigation
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STATION: IMPERFECT INFORMATION
• Potential problems with data quality, recency, seasonality, conflicting requirements
• Need minimum data requirements– Minimum list of chemicals to be measured
– Use data less than 5 years old
• BRI developed for summer; being assessed for other seasons
• BRI requires surficial sediments; dredging requires deeper cores
• Guidance must address all these issues
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STATION: BURDEN SHIFTING MECHANISM
• Value of incentives vs. rigid requirements
• Acknowledgment of imperfect information, varied application scenarios
• SQOs and related guidance should define several specific burden shifting mechanisms– What are thresholds for triggering burden shifting?
– What is the time frame within which incentives play out?
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INCORPORATING OTHER INFORMATION
• Triad data may not always be definitive
• Other data may be valuable in interpreting Triad results
• Need to avoid potential for “dueling data”
• Three Triad legs should trump other data for final decision making
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303d LISTING APPLICATION
• 303d guidance unclear about spatial distribution of samples needed for assessment– SQO guidance should somehow address this
• Guidance should include incentives for further investigation when results equivocal
• Questions re link between finding of impairment and identification of specific chemical cause– 303d and TMDL processes focus on specific causes
– Link between SQO and 303d / TMDL desirable
– Examine 303d / TMDL guidance for potential linkages