Title: Dissolved Oxygen Criteria Assessment (Chapter 5)
1Dissolved 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
2Chapter 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
3SIGNIFICANT 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.
4SIGNIFICANT 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.
5Evaluation of Instantaneous Criteria
- Method 1 Direct evaluation of interpolated
cruise data (same as 2006 deep channel 303d list) - Method 2 Logistic Regression
6Evaluation 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
7Evaluation 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
8Evaluation 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
9Open Water 30-day criterion more strict than
Instantaneous
10Open Water Direct Evaluation less strict than 10
Logistic and more strict than 50 Logistic
11Deep Water 30-day criterion consistent with
Instantaneous
12Deep Water Direct Evaluation consistent with
Logistic
13Deep Channel Direct Evaluation consistent with
Logistic
14(No Transcript)
15(No Transcript)
16(No Transcript)
17(No Transcript)
18(No Transcript)
19(No Transcript)
20Instantaneous Criteria
21SIGNIFICANT 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.
22SIGNIFICANT 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.
23SIGNIFICANT 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.
241-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
251-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
26SIGNIFICANT 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.
27SIGNIFICANT 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.
28SIGNIFICANT 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.
29Non-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
30Rest 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
31Rest of Year Results for 2006 303d list
32Updated 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
33Results of new curves little change
2 changes in attainment RDHMH Open Water now
passes YRKPH Deep Water now fails Both changes
less than 1
34Open Water DO 30-day Attainment
35Deep Water DO 30-day Attainment
36SIGNIFICANT 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.