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: Belews Creek Sampling Episode Report No. 6558 (June 6-11, 2010)

Dear Mr. Jordan:

Thank you for the opportunity to comment on the draft Sampling Episode Report (SER) for the Belews Creek June 6-11, 2010 sampling event. We have done our best, given the amount of data provided and t he relatively short time fr ame 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. In addition to the comments belo w, please also find attached the SER with minor changes documented with track changes.

Also, in addition to the analytical result s in the SER, Belews Creek supplied four additional samples taken in four separate months: October 2 010, November 2010, December 2010, and Januar y 2011. Examination of the full data set is necessary to reach any general conclusions. For that reason, we urge the EPA to supply the
additional data as soon as r easonably possible, so that we can evaluate the entire data set in the proper context.

According to EPA, the focus of Episode 6 558 was to characterize the purge stream entering the flue gas desulfurization (FGD ) wastewater treatment system and the
influent to and effluent from t he FGD bioreactor treatment syst em. The primary goal of the sampling program is to characterize the untreated FGD wa stewaters and effluent quality from technologies design ed to treat the wastewater. It is our understanding that EPA will utilize the results from the 4-day sampling event conducted at Belews Creek as2 part of its evaluation to determine the best av ailable technology (BAT) for the treatment
of FGD wastewater for the revision to the steam electric effluent guidelines.

We would like to emphasize that the e ffectiveness of the Belews Creek FGD wastewater treatment system can change dramatically bas ed on the constituents within the coal, the effectiveness of the air pol lutant control technology (such as the performance of the FGD scrubber and the electrostatic precipit ator), and other factors. Furthermore, future changes, including combus tion of different coal types and new air pollution control technology, such as additiv es to enhance the removal of contaminants from the flue gas, could considerably affect the performance of t he system. Changes in the performance of the FGD wastewater treatment system could occur suddenly based on operating conditions and depe nding on the sample collectio n day, these changes to
or affects on the wastewater system may not be known. This is evident from the analytical results from the Day 1 sample from the influent to the FGD wastewater system (SP1), in which dissolved mercury was detected at a concentration of 49.3 μ g/l as compared to 0.119 μ g/l and 0.142 μ g/l for the Day 2 and 3 samples, respectively. This is further supported by the results of the self-monito ring data from the bioreactor influent on June 9, July 14 and August 11, 2010, where mercury was detected at
concentrations of 59.3 μ g/l, 49.9 μ g/l, and 47.7 μ g/l, respectively, compared to the mercury concentrations detected on Sept ember 8 and October 7, 2010 of 0.150 μ g/l
and 0.892 μ g/l, respectively. These sampling epi sodes demonstrate that the monitoring
data submitted to EPA does not adequately characterize the performance of the system under all operating scenarios. As EPA moves forward with revisions to the steam electric effluent guidelines, Du ke Energy encourages EPA to consider the variability of the performance of the system to remove all contaminants , but especially mercury.

I. General Comments

FGD Wastewater Treatment System

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

• On page 2-3, Section 2.2.1 Physical/Chemical Separation 1 st paragraph: EPA incorrectly states that reaction t ank 2 was formerly used for organosulfide addition. Organosulfide has never been added to the system. We suggest revising the sentence to read: “From the equalization tank, the wastewater
enters three reaction tanks in series: reac tion tank 1, in which lime is added to increase the pH to between 8.6 and 9.2 S.U.; reaction tank 2, designed for organosulfide addition, but which is only used to provide additional mixing; and reaction tank 3, in which ferric chloride is added.”3 • On page 2-4, Section 2.2.2 Biological Reactors 2 nd paragraph: EPA states “Belews Creek operates the bioreacto rs to achieve a negative oxidation reduction potential (ORP) within the syst em...” We suggest inserting “ideally” prior to “operates” within this sentence. Belews Creek attempts to operate the bioreactors to achieve a negative ORP; the ORP, however, cannot always be
controlled due to the variabilit y of the ORP in the scrub ber purge. The ORP in the scrubber purge can vary dramatica lly based on operating conditions.

Comparison of UWAG and EPA Split Sample Study Data

The data comparisons discussed here are fr om the EPA and Utility Water Act Group (UWAG) four day Split Sample Study (4DSSS) conducted at the Belews Creek facility June 6-10, 2010.

In general, the comments below use four-day av erages of the data. The use of four-day averages is only for the purpose of assessing general trends. In using these averages,
Duke does not mean to endorse their use fo r all purposes. In many instances, data comparison should be done based on comparison of individual data points. We reserve the right to comment on indi vidual data points, as we deem appropriate, in the future.

Data Usability

Duke Energy agrees with EPA’s efforts to identify and flag pot entially erroneous (outlier) data points in the Belews Creek data set. However, the identif ied outliers are still generally included in ca lculating four-day av erages and other analyses. If a value is an outlier, then it should be disca rded 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. Several specific exam ples of qualified EPA
data from Belews Creek that should be excluded from cons ideration are given below.

1. Hexavalent chromium (Cr) samples were not preserved to the 9.3 to 9.5 target range in the field;

2. Some hexavalent Cr samples exceeded the < 6 deg. C. upon receipt; and4 3. Instances where widely variable field d uplicate relative percent differences (RPD) are observed and likely indi cate analytical problems or bias. For example, SP-2 COD (RPD 43%), SP-2 sulfate (RPD 58%), SP-3 COD (RPD 67%) and SP-3 mercury (RPD 185%). Such data shoul d be qualified and excl uded from further use even though there may not be specific a cceptance criteria for field duplicates
in the associated method.

EPA should use the data related comments in this response, based on UWAG split sample data, to confirm those EPA data points that are clearly inaccurate, and to revise
the SER to exclude the err oneous data points from calcul ations in the report and to exclude the erroneous data poin ts from the database used to calculate the new steam electric effluent guidelines.

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 rejecti ng or keeping data, which is useful to ensure that the variability (pre sent in every data set and associated with many sources of uncertainty) in the measur ements is preserved. If su ch 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 informa tion that is very important for a comprehensive understanding of t he analytical results. This in formation is also a 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; and

3. A full description of all types of filter media us ed in the system.5 Some of the above information has been provided to EPA either prior to or during sampling events or through EPA’s Information Collection Request (ICR) . Duke Energy urges EPA to integrate this information into the SER so the data can be understood in the specific context of the Be lews Creek 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 Belews Creek, it does not indicate the actual megawatt output for each day of sampling. There is no way of determining , based on the SER, whether the facility was operatin g at full capacity. Daily actual load information is also important to understanding the sampling event results.

Also, EPA’s study plan should have includ ed 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 chemistry and wa stewater treatment. While EPA gathered
some information about coal constituents dur ing the sampling events, it should have
collected full information about leve ls of sulfur, metals, and chlorides in the coal, as well as the heat value of the coal being 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 reported in units of nanograms per liter (parts per trillion, ppt). This approach is unnecessar ily confusing and gives the reader an initial impression that Hg levels in FGD wastewater s are very high and similar to those of the major cations such as calcium, magnesium and sodium. All metals data, including Hg data, should be reported in t he same ppb units to avoid c onfusing the reader during even a cursory review of the data tables.

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.6 Dissolved metals and mercury data

The accurate measurement of dissolved Hg and other metals in FGD wastewaters is challenging. EPA defines dissolved metals as metals, including Hg, associated with particles ≤ 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.). Hg and other metals associated with colloids (i.e. particles < 1 μ m in size and the vast majority < 0.45 μ m) can be an important frac tion of the elements 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 dissol ved metals or Hg dat a in developing the steam electric effluent guidelines. Differenc es in dissolved metals and Hg between EPA and UWAG split sample data were generally not substantial.

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 revi sed to include basic analytical information that answers the following questions.

1. How the trace metal samples were 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 recover able) 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 the compositing d one physically prior to analysis or was the “compositing” done arit hmetically after the individual analysis of each sample?

4. 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.7 5. 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 used with qualification. However, if the recoveries are significantly below the method acceptance criteria then the data should not be used.

Description of sampl ing points (SP)

Using only the description of a sampling poin t in many of the app endix A tables is unnecessarily confusing. In t he main body (e.g. sections 3, 4 & 5) of the SER, the data tables include both a description of the SP as well as the abbreviation (e.g. SP-2, SP-3, etc.). This minimizes confusing the two SP’s with influent in the description (i.e. influent to wastewater treatment system and influent to bioreactor). It would be helpful if the SP abbreviation were included on the daily data tables in SER Appendix A.

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 characterize 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.

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 lim it was used in the average calculation for all resu lts that were less than the quant itation limit and the result is reported with a less than sign (“<”)” (SER page 4-1). This appr oach 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 originally designed for use with discharges from metal pl ating facilities where cyanide was known to be present. Most of the interferences resu lt 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 t hat can cause false positives under the right conditions are organosulfides, thiosulfates, nitrites and other nitrogen compounds. Some of these8 compounds can actually cause cyanide to be produced during the acid distillation procedure of the method. T he 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 ent irely possible that most if not all of the reported cyanide detections coul d be sample matrix interf erences. Therefore, EPA should use caution when interp reting its cyanide results.

II. Specific Comments

Data comparisons

EPA has posed the following question to Duke Energy, regarding our self-monitoring
data:

“Several mercury results appear in consistent with self-monitoring data Duke Energy has provided for Be lews Creek. Please describe any
unusual conditions that were occu rring with the FGD system or FGD wastewater treatment system at the ti me of sampling, or that may have occurred in the preceding days that ma y have affected sampling results. Please provide all total and dissolved ar senic, mercury, and selenium data for the split samples collected by Du ke Energy/UWAG (on behalf of Duke Energy), for each day and sample point.”

Duke Energy does not believe the results obtained by EPA during the four-day sampling
event are inconsistent with the self-monitori ng data we provided for Belews Creek. As shown in the table below, the results of the self-monitoring conducted during this
timeframe are consistent wit h the results EPA obtained during the four-day sampling event. We are not aware of any unusual conditions with the FG D system or the FGD wastewater treatment system t hat may have occurred at the ti me of sampling or in the preceding days. During this timeframe, a blend of Northern Ap palachian with the Central Appalachian coal was being utiliz ed, which could have been a cause of the increased mercury results as co mpared with data from prior year s. We do believe this is indicative of normal and potential fu ture operations and si mply highlights the variability inherent in the operat ion of many coal-fired elec tric generating facilities.9 TABLE BC-1. Belews Creek Self-monitoring Data

Sample Day FGD Purge Bioreactor Influent (1) Bioreactor Effluent total recoverable mercury (ppb)
06/09/10 114 59.3 0.333

07/14/10 228 49.9 < 1

08/11/10 378 47.7 0.423

09/08/10 197 0.150 0.746

10/07/10 213 0.892 0.442
(1): The bioreactor influent total mercury results for June 9, July 14 and August 11, 2010 were reported incorrectly in the original data submittal. The above provides the correct results.

As requested by the EPA, Table A-1, attached to this response at page 13, is a listing of all arsenic (As), selenium (Se) and merc ury (Hg) data generated by UWAG from the 4DSSS. The UWAG Hg data in Table A-1 were generated as described in section 1 and the As and Se data were generated as de scribed in section 2 below. The data in Table A-1 were used to calculate the averages shown in various tables in this section.

1. Low-level Mercury

Total recoverable and dissolved Hg in UWAG split samples were analyzed by Albion Environmental (AE). Dissolved Hg samp les were filtered at AE under clean room
conditions within 24 hours of collection using a 0.45 μ m membrane filter with 5 μ m prefilter that were approved for Clean Water Ac t use by the EPA Engineering and Analysis Division (EAD, ATP N99-0021 dated 6-7-2000). Samples with elevated solids were allowed to settle and the “clearer” supernat ant was filtered for di ssolved Hg. All Hg samples were subjected to a heated bromine monochloride digestion (i.e. sealed bottles in oven at 50 °C for at least 6 hours) prio r to analysis using a method compliant flowinjection instrument. A com parison of the EPA Hg data su mmarized in the SER and the comparable UWAG split sample data from t he 4DSSS is presented in Table BC-2.10 TABLE BC-2. Comparison of 4-Day Averages of EPA & UWAG Split Sample Mercury Data
Source -> UWAG EPA UWAG EPA Processing -> Total Rec. Total Rec. Diss. Diss.
SP / Parameter -

> Hg (ppb) Hg (ppb) Hg (ppb) Hg (ppb)

SP-1 249 255 11.0 16.5
SP-2 45.7 47.6 39.7 46.2
SP-3 0.292 0.307 0.0200 0.0272

The elevated SP-1 day-one dissolved Hg dat um observed by the EPA (49.3 ppb) was confirmed by the UWAG data (4 2.5 ppb) and dissolved Hg dat a from all four days were used to calculate the averages shown in T able BC-2. A possible explanation for the elevated day-one dissolved Hg concentration is that a much larger portion of the total mercury in day one was present in the dissol ved form due to higher oxidizing conditions in the scrubber, as explained below. The elevated SP-3 day-two to tal recoverable Hg field duplicate (FDUP) observed by the E PA (6.44 ppb) was not confirmed by the UWAG data, and the EPA FDUP data point should be considered an outlier and was, therefore, not used to calcul ate the four-day average show n in Table BC-2. The EPA
and UWAG Belews Creek low-le vel Hg data are generally comparable for all sampling points (SP) with the exception of the one EP A FDUP total recoverable Hg outlier.

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 highly oxidizing the system, the great er the dissolved phase concentrations of mercury will be. Power plant operators are still attempting to understand 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, leve l of sulfur within the coal, pH, and the quality of makeup
water used in the scrubber. Because ORP r outinely fluctuates within scrubbers, the mercury phase within the wastewater exiting the scrubber is variable. Therefore, the level of treatment possible at a given FGD wastewater treatment system can vary considerably over time.

2. Low-level Arsenic

Total recoverable As in UWAG split sample s were analyzed by three laboratories using three different analytical methods. Dissolved As was analyzed by only one lab, Applied Speciation. The methods of As analysis are described below:11 1. Applied Speciation (ASC) using EPA me thod 200.8 modified for dynamic reaction cell ICP-MS (DRC-ICP-MS) on a Perk in Elmer DRC-II mass spectrometer

2. Southern Research Institute (SRI) us ing EPA method 200.8 modified for collision cell ICP-MS (CRC-ICP-MS) on an Agilent 7700 mass spectrometer

3. Ohio State University (OSU) Trace Element Research Laboratory using EPA method 200.8 modified for high resoluti on ICP-MS (HR-ICP-MS) on a ThermoFinnigan Element 2 Inductively Coupled Pl asma Sector Field Mass Spectrometer

Dissolved metals split samples were pum p-filtered in the field using a 0.45 μ m high capacity capsule filter (e.g . Gelman AquaPrep 600). Sample s with elevated solids were allowed to settle and the “clearer” supernat ant was filtered for dissolved metals. All metals samples were preserved in the respective laboratories using ultrapure nitric acid. Total recoverable metals samples were s ubjected to a heated strong acid leach digestion (patterned after EPA method 200.2), ei ther oven heated in the original sample bottle (ASC) or heated block digestions (SRI and OSU). A comparison of arsenic (As)
data from the EPA and UWAG 4DSSS is shown in Table BC-3.

TABLE BC-3. Comparison of 4-Day Averages of EPA & UWAG Split Sample Arsenic Data
Source -> UWAG EPA UWAG EPA Processing -> Total Rec. Total Rec. Diss. Diss.
SP / Parameter -

> As (ppb) As (ppb) As (ppb) As (ppb)

SP-1 252 235 4.19 < 3.28 SP-2 2.33 NQ (4.00) 3.64 NQ (4.00) SP-3 1.25 NQ (4.00) < 2.0 J NQ (4.00)

The EPA and UWAG BC low-level As data are generally comparable for all sampling points.

3. Low-level Selenium

Total recoverable and dissolved Se in UWAG split samples were analyzed by the same three laboratories using the same procedures described abov e. A comparison of Se
data from the EPA and UWAG 4DSSS is shown in Table BC-4.12 TABLE BC-4. Comparison of 4-Day Averages of EPA & UWAG Split Sample Selenium
Data
Source -> UWAG EPA UWAG EPA Processing -> Total Rec. Total Rec. Diss. Diss. SP / Parameter -> Se (ppb) Se (ppb) Se (ppb) Se (ppb)
SP-1 6420 6580 591 665
SP-2 1200 1230 1210 1210
SP-3 16.2 15.7 17.1 14.6

The EPA and UWAG Belews Creek low-level Se data are generally comparable for all sampling points.

4. Total Phosphorus

EPA (TestAmerica, TA) and UWAG (Alabam a Power Company, APC) used similar colorimetric methods to measure total phosphor us in the samples fr om the 4DSSS. TA
used EPA method 365.1 and APC used SM4500P-E. EPA and UWAG phosphorus data were generally comparable except for the SP-1 (see Tabl e BC-5). The comparison suggests that the EPA data underestimates t he total phosphorus concentration at SP-1. Barium, lead, and silver can interfere with th e colorimetric orthophosphate determination by forming insoluble phosphates. Barium and to a lesser extent lead levels in FGD wastewaters (especially SP-1 matrices) are high enough to raise an interference concern for phosphorus analyses. The analytical narrative in Appendix B suggests that the phosphorus data at SP-3 may be biased low and the sit uation appears also to apply
to SP-1.

TABLE BC-5. Comparison of 4-Day Averages of EPA & UWAG Split Sample Phosphorus
Data
Source-> UWAG EPA Processing -> Total Total
SP / Parameter -

> Phosphorus (ppm) Phosphorus (ppm)
SP-1 3.18 < 0.456

SP-2 0.036 NQ (0.05)

SP-3 0.17 < 0.096313 5. Total Dissolved Solids

Accurately measuring total di ssolved solids (TDS) levels in FGD wastewaters is difficult because of the hygroscopic nature of the dissolved solids when dried for weighing.
EPA and UWAG TDS data ar e compared in Table BC-6. The historical range of TDS
concentrations at the Belews Creek plant is 13,000 to 21,000 mg/L. The EPA TDS data overestimates the true TDS levels largely bec ause of several outliers being included in the calculated four-day averages. This situat ion is especially true for the SP-2 and SP-3 sampling points. The TestAmerica (TA) analytical narrative (Appendix B) notes “inconsistent weight calculat ions” and concludes that the “results may be biased high.”
The narrative also notes detec table TDS in two method bl anks and concludes that the
TDS levels in the associated samples were too high (1000 fo ld) to be affected by the
low-level TDS contamination. Howeve r, the data points were still B-flagged for
detectable TDS in the method blanks.

TABLE BC-6. Comparison of 4-Day Averages of EPA & UWAG Split Sample TDS Data

Source-> UWAG EPA Processing -> Total Total
SP / Parameter -> TDS (ppm) TDS (ppm) SP-1 15,600 17,300

SP-2 16,300 20,100

SP-3 16,400 27,300

6. Miscellaneous Issues

In the analytical narrative in Appendix B, Frontier Geosciences (FGS) 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 curv e. 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 Appendix A, the ratio of MDL to ML (repo rting 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 EPA14 method 200.8 MDL/ML’s listed 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?

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, 2011.15 TABLE A-1. UWAG split sample data for arsenic, selenium and mercury from the Belews Creek Sampling Event (Episode 6558 6-11 June 2010)

Date Description Hg AE As ASC As SRI As OSU Se ASC Se SRI Se OSU

SP-1 FGD Influent

6/7/2010 FGD Inf - Day 1 Diss FBlank < 0.002 U <0.0400J

6/7/2010 FGD Inf - Day 1 TR FBlank < 0.002 U < 0.007U

6/7/2010 FGD Inf - Day 1 Diss 42.5 3.88 1110 6/7/2010 FGD Inf - Day 1 TR 260 268 6120 6/8/2010 FGD Inf - Day 2 Diss 0.425 4.20 352 6/8/2010 FGD Inf - Day 2 TR 252 274 6540 6/9/2010 FGD Inf - Day 3 Diss 0.671 4.14 390 6/9/2010 FGD Inf - Day 3 TR 251 242 6280 6/10/2010 FGD Inf - Day 4 Diss 0.395 4.55 513 6/10/2010 FGD Inf - Day 4 TR 233 225 6740 SP-2 Physical/Chemical Effluent

6/8/2010 P/C Eff - Day 1 Diss FBlank < 0.002 U < 0.007U

6/8/2010 P/C Eff - Day 1 TR FBlank < 0.002 U < 0.007U

6/8/2010 P/C Eff - Day 1 Diss 44.7 3.90 1090 6/8/2010 P/C Eff - Day 1 TR 46. 8 3.62 1.90 1.3 1120 1000 1070 6/9/2010 P/C Eff - Day 2 Diss 45.2 3.53 1160 6/9/2010 P/C Eff - Day 2 TR 53. 8 3.71 1.73 2.0 1150 1080 1290 6/10/2010 P/C Eff - Day 3 Diss 36.3 3.40 1220

6/10/2010 P/C Eff - Day 3 Diss FDup 40.0 3.61 1280

6/10/2010 P/C Eff - Day 3 TR 43. 0 3.64 1.67 1.5 1220 1140 1430

6/10/2010 P/C Eff - Day 3 TR FDup 40.7 3.66 1.55 1.7 1210 1150 1260

6/11/2010 P/C Eff - Day 4 Diss 32.4 3.74 1290 6/11/2010 P/C Eff - Day 4 TR 44. 1 3.69 1.75 1.5 1290 1200 1330
SP-3 Bioreactor Effluent

6/8/2010 Bio Eff - Day 1 Diss FBlank < 0.002 U < 0.007U

6/8/2010 Bio Eff - Day 1 TR FBlank < 0.002 U < 0.007U

6/8/2010 Bio Eff - Day 1 Diss 0.0206 <2.00 J 7.18 6/8/2010 Bio Eff - Day 1 TR 0.227 <2.00 J 1.00 0.80 7.15 6.7 <33 6/9/2010 Bio Eff - Day 2 Diss 0.0175 <2.00 J 23.9

6/9/2010 Bio Eff - Day 2 Diss FDup 0.0150 <2.00 J 24.4

6/9/2010 Bio Eff - Day 2 TR 0.262 <2.00 J 1.00 0.76 22.6 22.2 <3316 Note: The UWAG Hg data in Table A-1 were generated as described in section 1 and the As and Se data were generated as described in section 2 above. Date Description Hg AE As ASC As SRI As OSU Se ASC Se SRI Se OSU 6/10/2010 Bio Eff - Day 3 TR 0.335 <2.00 J 0.85 0.81 5.18 4.5 <33 6/11/2010 Bio Eff - Day 4 Diss 0.0210 <2.00 J 25.3 6/11/2010 Bio Eff - Day 4 TR 0.385 <2.00 J 0.91 0.87 26.5 22.9 <33

All Units in ppb

U = Data points below calculated MDL (value provided is the MDL)

J = Data points above the MDL but below the RL (value provide is RL)

AE = Albion Environmental
ASC = Applied Speciation
SRI = Southern Research Institute
OSU = Ohio State University

29142.070312 EMF_US 38592672v5