1 

### MEMORANDUM

TO: Steam Electric Rulemaking Record

FROM: Dan-Tam Nguyen

DATE: July 28, 2015

SUBJECT: Evaluation of Alternatives for Handlin g Qualified Analytical Data in the Steam Electric Pollutant Loadings

1 Introduction
For the Steam Electric Rulemaking, EPA collected analytical data from various data sources, including EPA’s field sampling and CWA 308 mon itoring programs, EPA’s detailed survey for the industry, public comments, industry report s, and plant-monitoring data. Depending on the source, analytical data can be qualified base d on how the concentration compares to samplespecific detection or quantitati on limits determined by either the analytical method or the instrumentation used to test the wastewater sample. EPA defines the following terms:

 Method Detection Limit (MDL): The minimum concentration of a substance that can be measured and reported with 99 percent confid ence that the analyte concentration is greater than zero.

 Quantitation Limit (QL): The minimum concentration of a substance that can be reported with a specified degree of confidence that the analyte concentration is less than that minimum concentration and greater than the MDL. The QL can be no lower than the concentration of the lowest initial calibration standard. The QL is often referred to in
Effluent Limitation Guidelines and Standard s (ELG) support documents as the reporting
limit.

Analytical laboratories genera lly qualify sample results when the measured analyte
concentrations are below the MDL and/or belo w the QL (hereafter, termed as “qualified results”). As defined below, the analyte concentr ations can be qualified as a U-qualified result or a J-qualified result, generally designated w ith a “U” or “J” qualifier, respectively.

 U-Qualified Result or Non-Detect: The observation below the MDL, often reported as “U” by the analytical laboratory. EPA generall y refers to this value as a non-detect.2  J-Qualified Result: Observations reported with an es timated value and associated “J” flag by the analytical laboratory, indicating a definitive observation of the analyte in the sample that is measured above the MDL but below the lowest initia l calibration point.

Analytical data 1 from EPA’s sampling and monitoring programs included information on both qualified- and J-qualified result s and their related MDLs and QL s; however, data from other sources contained varying levels of this in formation. This memorandum summarizes EPA’s methodology and three alternative approaches for handling the varying levels of MDL and QL information for qualified results in pollutant load ings and removals estimates. To evaluate the differences, EPA calculated pollutant loadings and removals using the three alternative approaches and compared the results to the pollut ant loadings EPA calculated for the final rule.

2 EPA Methodology for Handling Qualif ied Results for the Final Rule

For all wastestreams, EPA’s estimates of baseline pollutant loadings and pollutant removals for the final rule use one half the sample-specific QL (or reporting limit) for all qualified results (example shown in Figure 1 ).

Figure 1. Example Using EPA Approach for Handling Qualified Results (in bold)

This approach allows EPA to use a consistent methodology for all wastestreams and for all data sources using the QL, which was largely availa ble for the analytical data EPA collected. Additionally, using “1⁄2 QL” results in a greater probability of some results being above the value used in the loadings and some being below the value used in the loadings. The QL is known for all qualified results in the FGD data set that EPA used in pollutant loadings/removal calculations. However, for fly ash and bottom ash transport wa ter, there are qualified results where there are insufficient data available to determine the resp ective sample-specific QL. In these instances the observation is reported as a “less than” resu lt along with a value, but EPA does not know

1 EPA used all data that met its data quality criteria in the calculation of pollutant loadings for the final rule; see the Technical Development Document for the Final Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (EPA 821-R-15-007) for more details on these data quality criteria. QL (4.0) 0 MDL (1.2) 1⁄2 QL (2.0) J-Qualified Result U-Qualified Result3 whether the reported value is the sample-specifi c MDL or QL. For the purpose of estimating pollutant loadings and removals, EPA assumed th e reported value is the QL and used one-half
that value in the calculations.

Although a J-value is the laborator y’s best estimate of the analyt e concentration for a J-qualified result, EPA chose not to use the estimated J-value associated with J-qualifie d values because it is a measurement made below the lowest point on the initial calibration curve (i.e., QL), and thus, a J-value has greater uncertainty than the MD L and QL associated with its result.

3 Alternative Approaches Considered for Handling Qualified Results
EPA considered three alternative approaches for handling the qualified resu lts that were included in baseline loadings and pollu tant removals calculations:

1. Include U-qualified results at a concentr ation equal to one half the MDL and Jqualified results at a con centration equal to the mi dpoint between the MDL and QL.
2. Include U-qualified results at a concentr ation equal to one half the MDL and Jqualified results at a concentration equal to the reported J-values.
3. Include U- and J-qualified results at a concentration equal to the QL.

Each of these alternative approach es is described in detail below.

Alternative Approach 1
This alternative approach sets U-qualified result s at a concentration equal to one half the MDL and J-qualified results at a con centration equal to the midpoint between the MDL and QL (i.e., 1⁄2 (MDL+QL)), as illustrated in Figure 2.

Figure 2. Example Using Alternative Approach 1 for Handling Qualified Results (in bold)

Alternative Approach 1 requires knowledge of both the QL and the MDL and can only be used in instances when both values are provided in the data. EPA field sampling and CWA 308 data QL (4.0) 0 MDL (1.2) Midpoint between QL and MDL (2.6) J-Qualified Resul t U-Qualified Resul t

1⁄2 MDL

(0.6)4 and a limited amount of industry data include both values. For purpos es of this analysis, for all remaining industry data where the MDL is unknow n for qualified results, EPA set the qualified results equal to 1⁄2 QL. Where there are insuffici ent data available to determine the respective sample-specific QL, EPA used the appro ach described in Section 2.

Alternative Approach 2
This alternative approach sets U-qualified result s at a concentration equal to 1⁄2 the MDL and Jqualified results at a concentration equal to the reported J-values, as illustrated in Figure 3.

Figure 3. Example Using Alternative Approach 2 for Handling Qualified Results (in bold)

Similar to Alternative 1, this alternative requires knowledge of both the QL and the MDL and can only be used when these two values are prov ided in the data. For all non-detects where the MDL is unknown and for J-qualified results without reported J-valu es, EPA set the concentration equal to 1⁄2 QL. Where there are insufficient dataavailable to determine the respective samplespecific QL, EPA used the approach desc ribed in Section 2.

Alternative Approach 3
This alternative approach sets all U- and J-quali fied results equal to the QL, as shown in Figure 4. For data where the QL is not available, EPA set the qualified results equal to the MDL. Although Alternative Approach 3 would allow for use of a consistent methodology for all
wastestreams and across all data sources like in the methodology EPA used for the final rule, using the QL for all qualified results overestimat es the baseline and option loadings because all qualified results are actually measured with a specified degree of confidence below the QL. QL (4.0) 0 MDL (1.2) Reported J-value J-Qualified Result U-Qualified Result

1⁄2 MDL

(0.6)5 Figure 4. Example Using Alternative Approach 3 for Handling Qualified Results (in bold)

4 Comparison of EPA’s Approach to Alternat ive Approaches on Pollutant Loadings and
Removals
EPA performed pollutant loadings and removals calculations for each wastestream and technology option using each of the three alterna tive approaches for handling qualified results. EPA compared the resulting pollu tant loadings and removals ag ainst those used for the final
ELG. QL (4.0) 0 MDL (1.2) J-Qualified Result U-Qualified Result6 Table 1 presents a summary of the difference in pollutant loadings and removals for FGD
wastewater and

Table 2 presents a summary for fly ash and bottom ash transport water.

Based on the results of this comparison, EPA de termined that using any of the alternative approaches for FGD wastewater resulted in small variations in pollutant loadings and removals from EPA’s approach. Alternative Approaches 1 and 2 also resulted in small variations from EPA’s approach for fly ash and bottom ash tran sport water, although Al ternative Approach 3 showed a larger increase in TWPE pollutant loadi ngs and removals. As discussed earlier in this memo, EPA does not favor this approach because a ll qualified results are actually measured with a specified degree of confidence below the QL; ther efore, using the full QL in this alternative approach for all qualified results tends to ove restimate the estimated baseline and option loadings.7 Table 1. Comparison of EPA and Three Altern ative Pollutant Loadings and Removals for FGD Wastewater

Alternative Approach Technology Option % Change in Pollutant Loadings Relative to Final ELG % Change in Pollutant Removals Relative to Final ELG

lbs TWPE lbs TWPE

1 Baseline -0.00015 -0.085 NA NA Chemical Precipitation -0.00010 -0.31 -0.00039 0.18 Biological Treatment -0.00010 -0.35 -0.00040 0.15

2 Baseline -0.00032 -0.090 NA NA Chemical Precipitation -0.00036 -0.30 -0.00008 0.16 Biological Treatment -0.00036 -0.34 -0.00012 0.13

3 Baseline 0.0020 0.47 NA NA Chemical Precipitation 0.0037 0.82 -0.0069 -0.036 Biological Treatment 0.0037 0.98 -0.0069 -0.012

Table 2. Comparison of EPA and Three Altern ative Pollutant Loadings and Removals for Fly Ash and Bottom Ash Transport Water

Alternative Approach Technology Option % Change in Pollutant Loadings Relative to Final ELG % Change in Pollutant Removals Relative to Final ELG a

lbs TWPE lbs TWPE

1 Fly Ash Transport Water Baseline 0.00 0.00 0.00 0.00 Bottom Ash Transport Water Baseline 0.00000027 0.21 0.00000027 0.21

2 Fly Ash Transport Water Baseline 0.00 0.00 0.00 0.00 Bottom Ash Transport Water Baseline -0.0000032 -0.053 -0.0000032 -0.053

3 Fly Ash Transport Water Baseline 0.078 15 0.078 15 Bottom Ash Transport Water Baseline 0.15 37 0.15 37 a - The change in the removals for fly ash and bottom ash transport water are approximately equal to the change in the baseline loadings because it is a zero discharge option. However, there are some plants that will continue to discharge fly ash and bottom ash transport water after implementation of the rule because they are generating units with a capacity of 50 MW or less, or oil-fired generating units, that are not facing any more stringent requirements than already exist under the previously es tablished best practicable control technology currently available (BPT) regulations.