Duke Energy Corporation

526 South Church Street
Charlotte, NC 28202

Mailing Address:

EC13K / P.O. Box 1006

Charlotte, NC 28201-1006

May 15, 2012

Via Electronic Mail

Ronald P. Jordan U. S. EPA Headquarters Engineering & Analysi s Division (4303T) Ariel Rios Building 1200 Pennsylvania Avenue, N.W. Washington, DC 20460

RE: Belews Creek Data: Monthly Sampling Events

Dear Mr. Jordan:

Thank you for the opportunity to comment on the draft data from the additional samples taken at Duke Energy Belews Creek St eam Station in October, November, and December 2010, and Januar y 2011. We have done our bes t, given the amount of data provided and the relatively s hort time frame for review, to thoroughly review the data. These comments should be considered prel iminary, as we may, upon further

consideration of the data , have additional comments.

I. General Comments

Data Usability

Duke Energy agrees with EPA’ s efforts to identify and flag potentially erroneous (outlier) data points in the Belews Cr eek data set. If a value is an outlier, however, then it

should be discarded from the dat a set and not used for any purpose. Also, there is no discussion of how flagged data po ints will be used (or exclude d) from consideration in calculating the new steam electric effluent limitations guidelines. For example, data points flagged B, Est, F and T indicate potentia lly significant inaccuracy (bias) in the

associated data.

Duke Energy also questions the validity an d use of the 4-set averages EPA calculated using the four monthly data sets (see Tables A5-1 - A5-3). The use of averages in some cases may obscure important differenc es among data points. EPA should explain how it intends to use the averages.

Also, the EPA uses the following approach when calculating averages: “If at least one result was above the quantitation limit, then 1⁄2 the quantitation limit was used in the average calculation for all resu lts that were less than the quant itation limit and the result2 is reported with a less than si gn (“<”)”. This approach is not justified because it introduces arbitrarily estimated data into the ca lculations. A more consistent, justifiable and conservative approach would be to use the quantitation limit in t he calculations as

is done when all results are below the quantitation limit.

II. Inadequate Treatment System Design and Operational Descriptions and Data

We noted several instances of inadequate treatment system des ign and operational descriptions and data in our earlier comment s on the draft Sampling Episode Report (SER) for Belews Creek. All of those comm ents also apply to the additional data set.

However, we reiterate here an essential point:

• EPA’s study plan should have included a comprehensive study of the coal feed
stock during each sampling event. It is clea r that coal characteristics have a very significant impact on FGD chemistry and wastewater treat ment. While EPA
gathered some information about coal consti tuents during the sampling events, it

should have collected full information about levels of sulfur, metals, and chlorides
in the coal, as well as the heating va lue of the coal being burned during the
relevant period for the sampling event.

III. Analytical Methods Descriptions

Also, as we stated in our ear lier comments, the analytical descriptions in the SER and the analytical narratives omit some basic information that should be included and would be helpful in making data evaluations and co mparisons. We reiterate our request for basic analytical information, as follows:

1. How were the trace metals samples digested? Was a heated strong acid leach digestion patterned after EPA method 200.2 used or some other alternative digestion? Were the metals samples pres erved to pH < 2 at least 24 hours prior to digestion (total recoverable) or analysis (dissolved)? Would EPA provide a description of the diges tion procedure used for metals samples analyzed by

Method 200.7 and 200.8?

2. How were the Hg sample s digested? Was the bromi ne monochloride digestion done at room temperature, heated, by Method 1631E Appendix A, etc.? If heated BrCl digestions were used, what temperature and duration were used? Were the same digestion procedures us ed for samples collected at SP-1, SP-2

and SP-3?

3. Was a bubbler system or a flow-injec tion analytical system used for the Method 1631E analyses? Field duplic ate variability was high for SP-2 and SP-3. What does EPA’s laboratory think may be causing such variability?3 4. Were individual grab samples for Hg flow-proportion composited? If so, was the compositing done physically prior to ana lysis or was the “compositing” done arithmetically after the indi vidual analysis of each sample?

5. What type of 0.45 micron f ilter was used to filter the dissolved Hg samples (e.g., capsule, flat membrane with pre-filter, fl at membrane with no pr e-filter, etc.)? Were the samples allowed to settle and the supernatant filtered or were the whole samples shaken and filtered directly without settling? What was the range of elapsed times after collection that the dissolved Hg samples were filtered?

6. How are known interferences in FGD matrices controlled? For example, chloride

is a known interferent in the COD method and the concentration must be carefully controlled to achieve accurate results.

7. More information is needed in the analytical narratives for matrix spikes and matrix spike duplicates (MS/MSD) that fail. For example, if failed recoveries are close to the acceptance range (87% when the limit is 90 to 100%) then the data can be used with qualification. However, if the recoveries are significantly below the method acceptance criteria then the data should not be used.

8. For the FGD influent (SP-1) samples, were whole, shaken samples used to determine classical analytes (except TD S and TSS) or were the FGD samples allowed to settle and the clearer super natant used for any of the classical analysis

Duke Energy urges EPA to make this info rmation available so that the data can be reviewed in the context of full laboratory QA/QC information and a full understanding of the analytical methods used.

IV. Quality Assurance/Quality Control Issues

Detections in the Field Blanks— The ERG review narrative do es not directly address detections in the field sampling blank ana lyses that were performed on the sampling equipment at each sample location for each sample set. Two of the field blanks contained zinc at levels of concern, as noted below.

Field Blank ID Zinc ( μ g/L)

SP-2 Set 2 15 J SP-1 (only one blank) 9.7 J

EPA’s quantitation limit for zinc from the cu rrent EPA lab is 40 μg/ L. The field blanks

show a contamination problem as to zinc, and call into question the zinc data. In relation to the quantitat ion limit, the amount of contam ination found in the blanks is significant.4 Problems with ICV, CCV, ICB, CCB, ISA, ISB, CRI or MR L Standard (indicated by a “^”)— This “catch all” mark appears to have been used by EPA to indicate a multitude of possible QC problems that would only be evident from an examination of the raw laboratory data. For ICP/MS, problems with the ICV (initial calibration verification) are supposed to be resolved before analysis proc eeds. Also, the CCV analyses (continuing calibration verification, per formed once every ten samples) are supposed to be corrected by recalibration and re-analysis. It is unclear why any of the samples would be qualified for either ICV or CCV outliers.

Also, continuing calibration blanks (CCBs) are a very important QC check when the laboratory is reporting values down to the MD L as J qualified results, as is being done here. ERG stated that they app lied “method specific criteria” in determining whether the CCBs (and other criteria qualified with a “^”, see above) were acceptable. However, for

both the ICP and ICP-MS met hods, the CCB acceptability is based on the reporting limit, not the MDL. For exam ple, Method 200.7 requires only that the CCB be less than the minimum (reporting) level. The ML is defi ned in Section 1.12 of the method: “The ML for each analyte can be calculated by mult iplying the MDL by 3.18 and rounding to the nearest (2, 5, or 10 X 10n) where n is an integer.” If the method criteria are applied,

then the data review would not qualify data until a continui ng calibration blank exceeded the reporting limit. This means that values reported below the r eporting limit can be highly inaccurate even without any data qualifier (other than “J”).

More on Continuing Calibration Blanks (CCB)— This is a very important QC check when the laboratory is reporting values down to the MDL as J qualified results, as is being done here. ERG st ated that they applied “method spec ific criteria” in determining whether the CCBs (and other crit eria qualified with a “^”, see above) were acceptable. However, for both the ICP and ICP-MS methods , the CCB acceptability as based on the reporting limit, not the MDL. For example, Method 200.7 r equires only that the CCB be less than the minimum (reporting) level. T he ML is defined in Section 1.12 of the method: “The ML for each analyte can be calc ulated by multiplying the MDL by 3.18 and rounding to the nearest (2, 5, or 10 X 10n) where n is an int eger.” If the method criteria are applied, then the data re view would not qualify data until a CCB exceeded the reporting limit. This means that values re ported below the report ing limit can be highly inaccurate even without any dat a qualifier (other than “J”).

MS/MSD QC Excursions (“F”)— Any “F” qualified results should be considered

estimated values and excluded from the EPA dataset. The “F” flag appears on the following Belews Creek FGD e ffluent data (Table A5-3):

Set 1 COD, Cyanide Set 4 COD, Cyanide, TDS, and Phosphorus5 V. EPA Requested Information

As requested, please find below the mercury split sample results from the influent to the bioreactor (SP2) and the effluent from the bi oreactor (SP3) from Belews Creek Steam Station for sample sets 1, 2, 3 and 4. Sp lit samples were not collected from the influent

to the wastewater treatment system (SP1) at Belews Cr eek Steam Station during the monthly sampling events.

Belews Creek Split Sample - Total R ecoverable Hg Data for SP-2 and SP-3

Sampling Date SP-2, Total Rec. Hg, μg/L SP-3, Total Rec. Hg, μg/L

10/07/2010 0.504 0.406

11/04/2010 0.124 0.175

12/09/2010 0.795 0.026

01/18/2011 0.135 0.009

Duke Energy notes that 3 of 4 monthly mercury values for SP-3 are above the EPA proposed mercury limit for PSNH’s Merrima ck Station. The proposed Merrimack mercury maximum daily limit is 0.014 μg/l.

Regarding EPA’s question on th e hydroclone overflow recycl ed for Belews Creek Steam Station, the percent recycled from the secondary hydroclone is 0%.

VI. Summary

In summary, Duke Energy reserves the right to comment on these data as EPA

continues its work on the st eam electric effluent guidelines rulemaking. In order to assess the data fully, EPA should provide comprehensive laboratory data for all samples. Duke Energy requests that EPA provide the actual laboratory reports from its contract laboratories for both the 4-day sa mpling episode and the monthly samples in order for Duke Energy to further ev aluate the data and the QA/QC results.