CORPORATE EHS SERVICES

Duke Energy

526 South Church Street
Charlotte, NC 28202

Mailing Address:

EC13K / P.O. Box 1006

Charlotte, NC 28201-1006

January 31, 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: Miami Fort Sampling Episode Report No. 6560, July 11-16, 2010

Dear Mr. Jordan:

Thank you for the opportunity to comment on the draft Sampling Episode Report (SER) for the Miami Fort July 11-16, 2010 sampling event. We have done our best, given the amount of data provided and the relatively short time frame for review, to thoroughly review the data within the report. Howe ver, these comments should be considered preliminary, as we may, upon further cons ideration of the data, have additional

comments.

Also, in addition to the analytic al results in the SER, Miam i Fort supplied four additional samples taken in four separ ate months: September 2010, November 2010, December 2010, and January 2011. Exami nation of the full data set is necessary to reach any general conclusions. For that reason, we urge EPA to supp ly the additional data as soon as reasonably possible, so that we c an evaluate the entire dat a set in the proper

context.

I. General Comments

Facility Overview and Wastewater Treatment Description

Within Section 2 of the SER, Duke Ener gy requests the follow changes to be made:

• On page 2-1, Section 2 (Facility Overview, 5 th paragraph) incorrectly states

that Miami Fort has had i ssues with blue plume stack emissions. This is not the case; lime is injected as a precaut ionary measure. We suggest revisingthe sentence to read: “Miami Fort inje cts lime into the flue gas between the

air heater and the ESP to control sulfur trioxide emissions.”

• On page 2-3, Section 2.2 (FGD Wastewater Treatment System, 3 rd
paragraph) creates confusion around the us e of ferric chloride, which had

been discontinued as an additive by the time of the July 2010 sampling. We suggest revising the sentence to read: “Miami Fort tested the effectiveness of the Nalmet® 1689 by adjusting the feed rate and addition amounts, in

combination with other FG D wastewater treatment additives (i.e., polymer).”

Data Usability

Duke Energy agrees with EPA’s efforts to identify and flag pot entially erroneous (outlier) data points in the Miami Fort data set. Howeve r, the identified outlie rs are still generally included in calculating four- day averages and other analyses. If a value is an outlier,

then it should be discarded from the data set and not used for any purpose.

Also, there is no discussion in the SER of how flagged data points will be used (or excluded) from consideration in calculating the new steam el ectric effluent guidelines. For example, data points flagged B, Est, F and T indicate potentially significant inaccuracies (bias) in the associated data.

Furthermore, statistical methods are available to systematically ident ify “outliers” which may then be excluded from a data set before fu rther interpretation. Such tests provide a consistent method and rationale for rejecting or keeping data which is useful to ensure that the variability (present in every data set and asso ciated with many sources of uncertainty) in the measurements is preser ved. If such methods will not be applied here, then a clear and consistent narrati ve for how questionable data points are

indentified and either c onsidered or rejected during data interpretation, summaries, etc. should be provided.

Inadequate Treatment System Design an d Operational Descriptions and Data

The SER lacks some basic technical info rmation that is very important to a comprehensive understanding of the analytical resu lts. This information is also key to understanding the conditions under which a certain level of treatment can be reliably

achieved.

System Design Information

The SER should include, at a mini mum, the following information:

1. Daily retention times for eac h stage of the treatment system;

2. Dimensions and water volume sizes for all individual components of the treatment system, including each holding tank , reaction tank, clarifier, sand filter, and biological treatment unit; and3. A full description of all types of filter media us ed in the system.

Some of the above information has been provided to EPA either prior to or during sampling events or through EPA’s Informati on Collection Request (I CR). Duke urges EPA to integrate this information into the SER so the data can be understood in the specific context of the Mi ami Fort treatment system.

System Operations Information

In addition, EPA should provide information on the load of each operating unit prior to the sampling event, as well as, on each of t he sampling days. While the SER states the design megawatt capacity of Miami Fort, it d oes not indicate the actual megawatt output for each day of sampling. There is no wa y of determining, based on the SER, whether the facility was operating at fu ll capacity. Daily actual load information is also important to understanding the sampling event results.

Also, EPA’s sampling and analysis plan should have included a comprehensive study of the coal feed stock during each sampling event. It is clear that coal characteristics have a very considerable impact on FGD chemistr y and wastewater treatment. While EPA gathered some information about coal constit uents 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 value of the coal bei ng burned during the relevant period for the sampling event.

Mercury reporting units

In the draft SER, all metals dat a are reported in units of mi crograms per liter (parts per billion, ppb) except mercury (Hg) data that are reported in units of nanograms per liter (parts per trillion, ppt). Th is approach is unnecessarily confusing and gives the reader an initial impression that Hg levels in FGD wastewaters are very high and similar to those of the major cations such as calc ium, magnesium and sodium. All metals, including Hg data, should be reported in t he same ppb units to avoid confusion.

Description of unfiltered metals data

In the draft SER, all unfiltered metals sample data are referre d to as “Total Metals.” This term is also used in the analytical narratives (Appendix B) for both EPA methods

200.7 and 200.8. This is misl eading and incorrect. Both EPA methods 200.7 and 200.8

use the term “total recoverable metals” to describe the unfiltered metals data generated by the method.

Dissolved metals and mercury data

The accurate measurement of dissolved merc ury (Hg) and metals in FGD wastewaters is challenging. EPA defines di ssolved metals, as metals, including Hg, associated withparticles ≤ 0.45 μ m or ionic that wil l pass through a 0.45 μ m filter. This definition is an operational definition and t here are many types of filters rated at 0.45 μ m (e.g. capsule, flat membrane, etc.). Metals, including Hg, associated with colloids (i.e. particles < 1

μ m in size and the vast majority < 0.45 μ m) can be an important fraction of the element present in FGD wastewaters. The fraction of < 0.45 μ m colloids removed (retained) during filtrations varies according to the ty pe of filter used. The phenomenon is called colloidal trapping. Capsule filters tend to retain a larger fraction of the < 0.45 μ m colloids than do other f ilter types. This situation can lead to significant differences in “dissolved” metals and Hg dat a depending on the filter used. The EPA should consider this fact when evaluating and using dissolved metals data, including Hg, in developing

the steam electric e ffluent guidelines.

Analytical methods descriptions

The analytical descriptions in section 4 and the analytical narratives omit some basic

information that should be included and woul d be helpful in making data evaluations and comparisons. Section 4 should be revis ed to include basic analytical that answers the following questions:

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 used? Were the metals samples preserved to pH < 2 at least 24 hours prior to digestion (total recoverable) or analysis (dissolved)?

2. How were the Hg sample s digested? Was the bromi ne monochloride digestion done at room temperature? Was it heat ed by method 1631E appendix A? Was

some other method used?

3. Were individual grab samples for Hg and some other paramet ers flow-proportion composited? If so, was t he compositing done physically prior to analysis or was the “compositing” done arit hmetically after the individual analysis of each sample?

4. How were the dissolved Hg samples filtered?

5. How were biphasic solids samples digested and analyzed for metals and Hg?

6. How were biphasic solids analy zed for classical parameters?

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

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

8. More information is needed in the analyti cal narratives for matr ix spikes and MS 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 usedwith qualification. However, if the recoveries are significantly below the method acceptance criteria then the data should not be used.

Qualification (Flagging) of Calculat ed (Reconstructed) Biphasic Data

The EPA SP-1 MF samples were analyzed usin g biphasic separations. The samples were separated into solid and liquid phases by centrifugation (Hg) or pressure filtration (classicals and metals). The two phases were analyzed separately and a single total aqueous concentration was calculated (reconstr ucted) using formula 4.1 (SER page 4- 2). For many classical parameters and some metals, the data for one or both phases of a sample were qualified as estimates based on a variety of quality control (QC) issues including exceeding analytical holding time (H-Flag), exceeding the preservation holding time (P-Flag), parameter detec ted in the method blank (B-Fl ag), etc. In the summary

data tables in section 4 and also in the dat a appendix A, the calculated total data point is listed with no qualification (flags) even th ough one or both of the component (parent) phase samples were qualified. A good example is Table A-5 and Table 4-1. For SP-1 day one both phase components samples for ni trate/nitrite and TK N are qualified as estimates with various flags. However, the to tal (calculated) nitrat e/nitrite (71.7 mg/L) and TKN (40.5 mg/L) data points show no data flags in either the top of Table A-5 or at all in table 4-1. This presentation approa ch is not correct and gives the mistaken impression that the final tota l data points have no associated QC issues (qualifications). Any data qualifications (flags ) associated with either of the parent (phase) samples

should be carried forward and also shown with t he associated total (calculated) value. The SER should be revised to correct this oversight.

Calculating Averages

EPA has chosen to calculate four-day averages of the major constituents throughout the SER. We question the validity of using four-day averages to characteri ze the data. For purposes of setting limits, the use of four-day aver ages would not be appropriate

because it would minimize the variability among the data points. At best, the use of the four-day averages only provides a "snapshot" of general trends. For all other purposes, we urge EPA to avoid av eraging the data points.

The EPA uses the following approach when calcul ating averages: “If at least one result was above the quantitation limit, then 1⁄2 the quant itation limit was used in the average

calculation for all results that were less than the quantitation limit and the result is reported with a less than sign (“<”)” (SER page 4- 1). This approach is not justified because it introduces arbitrarily estimated data into the calculations. A more consistent, justifiable and conservative approach would be to use the quantitation limit in the

calculations as is done when all result s are below the quantitation limit.

Cyanide Interferences

All of the 40 CFR Part 136 approved cyani de methods are subject to numerous interferences, especially in complex sample matrices. The methods were originallydesigned for use with discharges from metal pl ating facilities where cyanide was known to be present. Most of the interferences result in false positives, and many of these are caused by sulfide and other reduced sulfur compounds which may be present in FGD wastewater. Other compounds that can cause false positives under the right conditions are organosulfides, thiosulfates, nitrites and other nitrogen compounds. Some of these compounds can actually cause cyanide to be produced during the acid distillation procedure of the method. The procedures for removing interferences provided in the methods are often not effective, and comple x samples, such as FGD wastewater, may also contain unknown interferences. It is entirely possible that most -- if not all -- of the reported cyanide detections co uld be sample matrix inte rferences. Therefore, EPA should use caution when interp reting its cyanide results.

The cyanide results reported by EPA for Miam i Fort could be biased high due to the organosulfide addition in the chemical treat ment system. The organosulfide compound used for treatment may not be detected in the sulfide inte rference check by the usual method procedures. In addition, these com pounds will break down into simple sulfide during the acid digestion and cause an interf erence. It may be not eworthy that there was very little cyanide detected in the Belews Creek and Alle n FGD wastewaters. These facilities do not use organosulfide a ddition in their physical/chemical treatment system. Therefore, analytical results showing that cya nide is present in FGD wastewaters may be a false positive due to interferences.

II. Specific Comments

1. Low-level Mercury

The EPA unfiltered SP-1 data exhibit a high degree of variability, i.e. RSD 53%. The unfiltered mercury data cannot be properly evaluated with the information given in the SER. The Frontier Geosciences (FGS) analytic al narrative (Appendix B) only lists EPA method 1631E which is not approved for the analys is of solids. No mention is made of how the biphasic solids were digested or analyzed. Without this information, including the associated QC data, an appropriate ev aluation cannot be conducted. The SER should be revised to include a description of the solids Hg digestion and analytical procedures.

The dissolved Hg results, especially SP-1, could be affected by colloidal trapping depending on how the EPA samples were filtered. The SER, however, does not include a discussion on how the EPA samples were filt ered; a proper evaluatio n, therefore, of the Hg data cannot be made. The SER s hould be revised to include a description of the type of filter and procedur e used by FGS to filter t he EPA dissolved Hg samples.

Recent studies of mercury chemistry withi n FGD scrubbers may provide some insight into why mercury may routinely change phas es and thus why FGD wastewater systems may have variable mercury treatment resu lts. Based on data from 15 different scrubbers, when the oxidation reduction potential (ORP) withi n the scrubber is high, more mercury tends to be in the dissolved phase (Allen et al., 2011). The more highlyoxidizing the system, the great er the dissolved phase concentrations of mercury will be. Power plant operators are still attempting to understand and control ORP within their scrubbers. There appear to be many factors that may affect ORP, including, but not limited to, the presence of an SCR, load, level of sulfur within the coal, pH, and the quality of makeup water used in the scrubber. Because ORP routinely fluctuates within individual scrubbers (and varies between scr ubbers of different des igns), the mercury phase within the wastewater exiting the scrubber is variable. Therefore, the level of treatment possible at a giv en FGD wastewater treatment system can vary extensively

over time.

2. Low-level Selenium

The EPA TestAmerica (TA) analytical narra tive raises concerns about potential analytical bias in the EPA SP-2 dissolved Se data. For example, “the dissolved selenium result of 530 μg/L for sample 71748 FGD Effluent Day 4 (280-5438-1) is greater than the total selenium value of 480 μg/L reported fo r the same sample.” Also

the EPA SP-2 dissolved Se MS/MSD was in valid (Flagged 4). The TA analytical narrative only states that for such invalid spikes “many spike recoveries were outside

the method control limits of 70–130%.” It would be helpful to know the percent

recoveries of the EPA SP-2 di ssolved Se MS/MSD spikes. If the spike recoveries were > 130% it could indicate a pot ential analytical overestimation of the dissolved Se data. Finally, a post digestion Se spike failed (69 % recovery) on the day 3 SP-2 sample (not stated if total recoverable or dissolved). This is another indication of potential analytical

bias in the EPA SP-2 Se data.

3. Nitrogen Related Parameters

The EPA laboratory (TestAmerica, TA) performed separate nitrogen analyses on biphasically separated filtrate and solids ph ases. The EPA (TA) used the two separate phase data to calculate a single “reconstruc ted” value for ammonia, nitrogen and TKN in each sample. The three nitrogen methods used (i.e. EPA methods 350.1, 353.2 and 351.2) are all aqueous methods. There is no description of how the solid phase samples were prepared for analysis. Presumably TA used some sort of aqueous extraction (elutriate type) procedure to pr oduce an aqueous extract of the solids that could then be analyzed by the various methods . This procedure should be described briefly in SER section 4.1. Also all SP-1 aqueous and solid ph ase nitrogen species samples were qualified as es timated values for exceeding holding times (H-Flag), exceeding preservation time (P -Flag) and blank issues for some (B-Flag). However, that flagging is absent from the summary tabl e 4-1 and in Appendix A data tables A-5 to

A-8 for the reconstructed tota l values. This is a mistake which should be corrected in the SER. The flags associated with the com ponent samples should also be associated with any calculated total va lues derived from those co mponent (phase) samples.

Because all the EPA SP-1 nitr ogen data are considered estimates, the EPA should use the SP-1 total (reconstructed) nitr ogen species data with caution.4. Miscellaneous Issues

In the analytical narrative in Appendix B, Frontier Geosciences (F GS) validates their EPA method 1631E calibration using a linear r egression correlation factor criterion of > 0.995. This statement is misleading becaus e method 1631E does not allow for a linear regression calibration curve. Rather method 1631E uses a mean calibration factor (CFm), which is a simple arithmetic mean of the five or more individual calibration factors. The acceptance criteria for the method 1631E calibration are an RSD of < 15% for the five or more CF’s and recovery bet ween 75-125% at the met hod reporting limit of 0.5 ppt. FGS may want to revise the analytic al narrative to clarify this situation.

In the SER data Appendix A, the ratio of MDL to ML (reporting limit) for EPA method 200.7 averages ~ 20 with a range of approximately 3 to 55. The expected ratio is 3-5 as

shown for EPA method 200.8 MDL/ML’s list ed in the SER. The reason for this

aberration is not clear. Are the MDL’s too low or the ML’s too high for the elements with

elevated ratios?

Many of the EPA chromium (Cr) data in the SER tables are qualif ied (flagged) “^” with the statement “ICV, CCV, ICB, CCB, ISA, ISB, CRI, or MRL standard: Instrument
related QC exceeds the control limits.” However, the Test America (TA) EPA method 200.8 analytical narrative (Appe ndix B) makes no mention of any quality control (QC) issues associated with the Cr analyses. Sh ould the Cr data be fla gged or not? If there are quality control concerns, t hen certainly these data may not be relied upon or used for any purpose.

The Appendix A data tables for the SP-1 biphas ic separation (i.e. Tables A-1, A-2, A-3 and A-4) contain a concentration units erro r for the aqueous metals data. The aqueous

metals data listed in those tables are in mi crograms per liter (parts per billion, ppb) and not milligrams per liter (parts per million, ppm) as indicated at the top of the table. It appears that the solid phase metals data units are correctly listed as ppm. However, when listing solids metals data it is im portant to indicate whether the solids concentrations are on a wet or dry weight basis. The simplest correction for the affected Appendix A tables would be to change the “Total Metals” sub-heading to read “Total recoverable metals (aqueous and total result in ug/L and solid results in mg/kg dry weight).”

Sources

Allen, Jonathan O., Eggert, De rek, and Tyree, Corey A. Effect of FGD Chemistry on Wastewater Composition , presented at Air Quality V II Conference, Arlington VA, October 25, 2011.

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