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Dissolved Oxygen Criteria Assessment (Chapter 5)

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Title: Chesapeake Bay Water Quality Criteria Addendum Author: hhawk Last modified by: hhawk Created Date: 11/6/2006 2:58:38 PM Document presentation format – PowerPoint PPT presentation

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Title: Dissolved Oxygen Criteria Assessment (Chapter 5)


1
Dissolved Oxygen Criteria Assessment (Chapter 5)
  • Significant Comments and Recommended Resolutions

Rich Batiuk and Gary Shenk November 14-15, 2006
Chesapeake Bay Water Quality Steering Committee
Meeting
2
Chapter 5-DO Attainment(Attachment M)
  • Background
  • Clarification of temporal periods for assessing
    dissolved oxygen attainment
  • Clarification open-water criteria apply to
    shallow-waters
  • Methodologies for assessing attainment of the
    7-day, 1-day, instantaneous minimum criteria
  • Refinement of OW, DW reference curves
  • Rationale for not publishing percent
    saturation-based dissolved oxygen criteria

3
SIGNIFICANT COMMENTS
  • Issue No. 1 Assessment period
  • A concern has been raised regarding the summer
    criteria attainment assessment period.
  • Recommendation
  • Water Quality Steering Committee should agree to
    publish guidance recommending open-water and
    deep-water dissolved oxygen criteria continue to
    be assessed for June 1-September 30 for the
    summer period and open-water dissolved oxygen
    criteria continue to be assessed also during the
    non-summer October 1-May 31 period.

4
SIGNIFICANT COMMENTS
  • Issue No. 2 Allowable exceedances of
    instantaneous minimum criteria
  • Conflicting comments were received expressing
    concern about the EPA recommendation that
  • attainment assessment of the instantaneous
    minimum dissolved oxygen criteria be conducted
    strictly based on analysis of violations of the
    observed data within the appropriate designated
    use segment over the appropriate time of the year
    and three year assessment period without
    application of the CFD methodology and use a
    reference curve.

5
Evaluation of Instantaneous Criteria
  • Method 1 Direct evaluation of interpolated
    cruise data (same as 2006 deep channel 303d list)
  • Method 2 Logistic Regression

6
Evaluation of Instantaneous Criteria
  • Method 1 Direct evaluation of interpolated
    cruise data (same as 2006 deep channel 303d list)

Note No reference curve is used in evaluation.
Each cruise is interpolated separately and used
as a point in the CFD. Any violation of the
criterion at any time during the 3-year period is
a failure
7
Evaluation of Instantaneous Criteria
  • Method 2 Logistic Regression. Determine the
    probability that an exceedence occurred in each
    month, given location, time, and observed DO.

Calculate probability that DO was below the
criterion given the observations that month.
Interpolate probabilities
Assign an acceptable probability
Apply CFD and reference curve
8
Evaluation of Instantaneous Criteria
  • Direct Estimation
  • Estimate of space and time below criterion is
    unbiased
  • No reference curve necessary
  • Straightforward Procedure
  • Estimate of pass/fail biased toward passing
  • (reduced with more samples or application of
    reference curve)
  • Logistic Regression
  • Estimate of space and time below criterion bias
    not known
  • Reference curve and/or acceptable failure rate
    necessary
  • Complex Procedure
  • Estimate of pass/fail bias unknown

9
Open Water 30-day criterion more strict than
Instantaneous
10
Open Water Direct Evaluation less strict than 10
Logistic and more strict than 50 Logistic
11
Deep Water 30-day criterion consistent with
Instantaneous
12
Deep Water Direct Evaluation consistent with
Logistic
13
Deep Channel Direct Evaluation consistent with
Logistic
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20
Instantaneous Criteria
21
SIGNIFICANT COMMENTS
  • Issue No. 2 Allowable exceedances of
    instantaneous minimum criteria
  • Recommendation
  • Water Quality Steering Committee agreement on the
    method to be used in assessing attainment of the
    open-water and deep-water instantaneous minimum
    dissolved oxygen criteria OR give clear
    directions to the CAP Workgroup and the
    analytical team working on the two methodologies
    as to what to pursue and what to/not to focus on.

22
SIGNIFICANT COMMENTS
  • Issue No. 2 Allowable exceedances of
    instantaneous minimum criteria
  • Recommendation (Continued)
  • If work is not completed on a methodology in time
    for publication in this Bay criteria addendum,
    then proceed forward with assessing attainment of
    the instantaneous minimum dissolved oxygen
    criteria strictly based on analysis of violations
    of the observed data within the three year
    assessment period without application of the CFD
    methodology and use of a reference curve.

23
SIGNIFICANT COMMENTS
  • Issue No. 3 Assessing attainment of 1-day, 7-day
    mean criteria
  • Recommendations and concerns were both expressed
    in response to proposed approaches to developing
    methods to assess attainment of the 1-day and
    7-day mean dissolved oxygen criteria.

24
1-day and 7-day DO criteria
  • Can not be measured, must use some type of model
  • Directly use Bay Model
  • Not based on data, not unbiased
  • Years of simulation are not always the most
    current

25
1-day and 7-day DO criteria
  • Statistical Simulation Model
  • Run many instances and sample it.
  • Can be constructed if spatial and temporal
    structure of variance and distributions are known
  • Buoys
  • Continuous monitoring
  • Water quality mapping
  • Bay model

26
SIGNIFICANT COMMENTS
  • Issue No. 3 Assessing attainment of 1-day, 7-day
    mean criteria
  • Recommendation
  • Water Quality Steering Committee should charge
    the CAP Workgroup and the existing analytical
    team to complete their work on methodologies for
    assessing attainment of the 1-day and 7-day mean
    dissolved oxygen criteria in time to publish the
    recommended methodology in the final Bay criteria
    addendum.

27
SIGNIFICANT COMMENTS
  • Issue No. 4 Statistical evaluation of attainment
  • Recommendations for proceeding forward with the
    STAC recommended development of statistical
    methods for assessing attainment.
  • Recommendation
  • Water Quality Steering Committee should support
    follow-up work in the next several years on the
    recommendations laid out in the STAC expert
    panels report.

28
SIGNIFICANT COMMENTS
  • Issue No. 5 Implication of new
    open-water/revised deep-water ref. curves
  • Concerns were expressed about the new
    biologically-based open reference curve, the
    revised/updated deep-water reference curve and
    implications for future criteria attainment
    assessments.

29
Non-Summer (Rest of Year)
  • Open water to bottom everywhere
  • Uses Jan 1 through May 31 and Oct 1 through Dec
    12 of same year.
  • Uses default 10 reference curve
  • Does not drive decisions

30
Rest of Year Results for 2006 303d list
  • 33 assessed areas passed OW summer and OW ROY
  • 42 failed OW summer, but passed OW ROY
  • 3 failed OW ROY, but passed OW summer
  • CB3 and CB4 failed DW and DC
  • SASOH passed OW, failed ROY by 1.6

31
Rest of Year Results for 2006 303d list
32
Updated Reference Curves
  • Published reference curves were developed using
    old evaluation procedures and IBI locations that
    did not necessarily reflect the correct
    designated uses.
  • New curves developed consistent with latest
    procedures

33
Results of new curves little change
2 changes in attainment RDHMH Open Water now
passes YRKPH Deep Water now fails Both changes
less than 1
34
Open Water DO 30-day Attainment
35
Deep Water DO 30-day Attainment
36
SIGNIFICANT COMMENTS
  • Issue No. 5 Implication of new
    open-water/revised deep-water ref. curves
  • Recommendation
  • Water Quality Steering Committee should agree to
    the publication of the proposed
    biologically-based open-water dissolved oxygen
    criteria reference curve.
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