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 & Analysis 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 the relatively short time frame for review, to thoroughly 

review the data within the report. However, these comments should be considered 

preliminary, as we may, upon further consideration of the data, have additional 

comments. In addition to the comments below, please also find attached the SER with 

minor changes documented with track changes. 

Also, in addition to the analytical results in the SER, Belews Creek supplied four 

additional samples taken in four separate months: October 2010, November 2010, 

December 2010, and January 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 reasonably possible, so that we can evaluate the entire data 

set in the proper context. 

According to EPA, the focus of Episode 6558 was to characterize the purge stream 

entering the flue gas desulfurization (FGD) wastewater treatment system and the 

influent to and effluent from the FGD bioreactor treatment system. The primary goal of 

the sampling program is to characterize the untreated FGD wastewaters and effluent 

quality from technologies designed to treat the wastewater. It is our understanding that 

EPA will utilize the results from the 4-day sampling event conducted at Belews Creek as 
2

part of its evaluation to determine the best available technology (BAT) for the treatment 

of FGD wastewater for the revision to the steam electric effluent guidelines. 

We would like to emphasize that the effectiveness of the Belews Creek FGD 

wastewater treatment system can change dramatically based on the constituents within 

the coal, the effectiveness of the air pollutant control technology (such as the 

performance of the FGD scrubber and the electrostatic precipitator), and other factors. 

Furthermore, future changes, including combustion of different coal types and new air 

pollution control technology, such as additives to enhance the removal of contaminants 

from the flue gas, could considerably affect the performance of the system. Changes in 

the performance of the FGD wastewater treatment system could occur suddenly based 

on operating conditions and depending on the sample collection 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 μg/l 

as compared to 0.119 μg/l and 0.142 μg/l for the Day 2 and 3 samples, respectively. 

This is further supported by the results of the self-monitoring data from the bioreactor 

influent on June 9, July 14 and August 11, 2010, where mercury was detected at 

concentrations of 59.3 μg/l, 49.9 μg/l, and 47.7 μg/l, respectively, compared to the 

mercury concentrations detected on September 8 and October 7, 2010 of 0.150 μg/l 

and 0.892 μg/l, respectively. These sampling episodes 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, Duke 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 Energy requests the follow change to be made: 

• On page 2-3, Section 2.2.1 Physical/Chemical Separation 1st paragraph: EPA 

incorrectly states that reaction tank 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: reaction 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 2nd paragraph: EPA states 

“Belews Creek operates the bioreactors to achieve a negative oxidation 

reduction potential (ORP) within the system...” 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 variability of the ORP in the scrubber purge. The ORP in 

the scrubber purge can vary dramatically based on operating conditions. 

Comparison of UWAG and EPA Split Sample Study Data 

The data comparisons discussed here are from 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 averages 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 for all purposes. In many instances, data 

comparison should be done based on comparison of individual data points. We reserve 

the right to comment on individual data points, as we deem appropriate, in the future. 

Data Usability 

Duke Energy agrees with EPA’s efforts to identify and flag potentially erroneous (outlier) 

data points in the Belews Creek data set. However, the identified outliers 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 electric effluent guidelines. 

For example, data points flagged B, Est, F and T indicate potentially significant 

inaccuracies (bias) in the associated data. Several specific examples of qualified EPA 

data from Belews Creek that should be excluded from consideration 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; and 
4

3. Instances where widely variable field duplicate relative percent differences (RPD) 

are observed and likely indicate 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 should be qualified and excluded from further 

use even though there may not be specific acceptance 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 erroneous data points from calculations in the report and to 

exclude the erroneous data points from the database used to calculate the new steam 

electric effluent guidelines. 

Furthermore, statistical methods are available to systematically identify “outliers” which 

may then be excluded from a data set before further 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 associated with many sources 

of uncertainty) in the measurements is preserved. If such methods will not be applied 

here, then a clear and consistent narrative for how questionable data points are 

indentified and either considered or rejected during data interpretation, summaries, etc. 

should be provided. 

Inadequate Treatment System Design and Operational Descriptions and Data 

The SER lacks some basic technical information that is very important for a 

comprehensive understanding of the analytical results. This information 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 minimum, the following information: 

1. Daily retention times for each 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 used 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 Belews 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 the 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 operating at full capacity. Daily actual load information is also 

important to understanding the sampling event results. 

Also, EPA’s study 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 chemistry and wastewater treatment. While EPA gathered 

some information about coal constituents during the sampling events, it should have 

collected full information about levels 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 data are reported in units of micrograms per liter (parts per 

billion, ppb), except mercury (Hg) data reported in units of nanograms per liter (parts per 

trillion, ppt). This 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 calcium, magnesium and sodium. All metals data, including Hg 

data, should be reported in the same ppb units to avoid confusing 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 referred 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 misleading 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 μm or ionic that will pass through a 0.45 μm filter. This definition is an 

operational definition and there are many types of filters rated at 0.45 μm (e.g. capsule, 

flat membrane, etc.). Hg and other metals associated with colloids (i.e. particles < 1 μm 

in size and the vast majority < 0.45 μm) can be an important fraction of the elements 

present in FGD wastewaters. The fraction of < 0.45 μm colloids removed (retained) 

during filtrations varies according to the type of filter used. The phenomenon is called 

colloidal trapping. Capsule filters tend to retain a larger fraction of the < 0.45 μm 

colloids than do other filter types. This situation can lead to significant differences in 

“dissolved” metals and Hg data depending on the filter used. The EPA should consider 

this fact when evaluating and using dissolved metals or Hg data in developing the 

steam electric effluent guidelines. Differences 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 would be helpful in making data evaluations 

and comparisons. Section 4 should be revised 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 preserved to pH < 2 at least 24 hours prior 

to digestion (total recoverable) or analysis (dissolved)? 

2. How were the Hg samples digested? Was the bromine monochloride digestion 

done at room temperature? Was it heated by method 1631E appendix A? Was 

some other method used? 

3. Were individual grab samples for Hg and some other parameters flow-proportion 

composited? If so was the compositing done physically prior to analysis or was 

the “compositing” done arithmetically 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 analytical narratives for matrix 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 sampling points (SP) 

Using only the description of a sampling point in many of the appendix A tables is 

unnecessarily confusing. In the 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 averages 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 averaging 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 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 results are below the quantitation limit. 

Cyanide Interferences 

All of the 40 CFR Part 136 approved cyanide methods are subject to numerous 

interferences, especially in complex sample matrices. The methods were originally 

designed for use with discharges from metal plating 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 
8

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 complex samples, such as FGD wastewater, may 

also contain unknown interferences. It is entirely possible that most if not all of the 

reported cyanide detections could be sample matrix interferences. Therefore, EPA 

should use caution when interpreting 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 inconsistent with self-monitoring data 

Duke Energy has provided for Belews Creek. Please describe any 

unusual conditions that were occurring with the FGD system or FGD 

wastewater treatment system at the time of sampling, or that may have 

occurred in the preceding days that may have affected sampling results. 

Please provide all total and dissolved arsenic, mercury, and selenium data 

for the split samples collected by Duke 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-monitoring data we provided for Belews Creek. As 

shown in the table below, the results of the self-monitoring conducted during this 

timeframe are consistent with the results EPA obtained during the four-day sampling 

event. We are not aware of any unusual conditions with the FGD system or the FGD 

wastewater treatment system that may have occurred at the time of sampling or in the 

preceding days. During this timeframe, a blend of Northern Appalachian with the 

Central Appalachian coal was being utilized, which could have been a cause of the 

increased mercury results as compared with data from prior years. We do believe this 

is indicative of normal and potential future operations and simply highlights the 

variability inherent in the operation of many coal-fired electric 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 mercury (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 described 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 samples were filtered at AE under clean room 

conditions within 24 hours of collection using a 0.45 μm membrane filter with 5 μm prefilter that were approved for Clean Water Act 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” supernatant was filtered for dissolved 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) prior to analysis using a method compliant flowinjection instrument. A comparison of the EPA Hg data summarized in the SER and the 

comparable UWAG split sample data from the 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 datum observed by the EPA (49.3 ppb) was 

confirmed by the UWAG data (42.5 ppb) and dissolved Hg data from all four days were 

used to calculate the averages shown in Table 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 dissolved form due to higher oxidizing conditions 

in the scrubber, as explained below. The elevated SP-3 day-two total recoverable Hg 

field duplicate (FDUP) observed by the EPA (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 calculate the four-day average shown in Table BC-2. The EPA 

and UWAG Belews Creek low-level Hg data are generally comparable for all sampling 

points (SP) with the exception of the one EPA FDUP total recoverable Hg outlier. 

Recent studies of mercury chemistry within FGD scrubbers may provide some insight 

into why mercury may routinely change phases and thus why FGD wastewater systems 

may have variable mercury treatment results. Based on data from 15 different 

scrubbers, when the oxidation reduction potential (ORP) within the scrubber is high, 

more mercury tends to be in the dissolved phase (Allen et al., 2011). The more highly 

oxidizing the system, the greater 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, level of sulfur within the coal, pH, and the quality of makeup 

water used in the scrubber. Because ORP routinely 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 samples 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 method 200.8 modified for dynamic reaction 

cell ICP-MS (DRC-ICP-MS) on a Perkin Elmer DRC-II mass spectrometer 

2. Southern Research Institute (SRI) using 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 resolution ICP-MS (HR-ICP-MS) on a ThermoFinnigan Element 2 Inductively Coupled Plasma Sector Field Mass Spectrometer 

Dissolved metals split samples were pump-filtered in the field using a 0.45 μm high 

capacity capsule filter (e.g. Gelman AquaPrep 600). Samples with elevated solids were 

allowed to settle and the “clearer” supernatant was filtered for dissolved metals. All 

metals samples were preserved in the respective laboratories using ultrapure nitric acid. 

Total recoverable metals samples were subjected to a heated strong acid leach 

digestion (patterned after EPA method 200.2), either 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 above. 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 (Alabama Power Company, APC) used similar 

colorimetric methods to measure total phosphorus in the samples from 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 Table BC-5). The comparison 

suggests that the EPA data underestimates the total phosphorus concentration at SP-1. 

Barium, lead, and silver can interfere with the 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 situation 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 < 0.0963 
13

5. Total Dissolved Solids

Accurately measuring total dissolved 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 are 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 because of several outliers being included in 

the calculated four-day averages. This situation is especially true for the SP-2 and SP-3 

sampling points. The TestAmerica (TA) analytical narrative (Appendix B) notes 

“inconsistent weight calculations” and concludes that the “results may be biased high.” 

The narrative also notes detectable TDS in two method blanks and concludes that the 

TDS levels in the associated samples were too high (1000 fold) to be affected by the 

low-level TDS contamination. However, 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 regression correlation factor criterion of > 

0.995. This statement is misleading because 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 between 75-125% at the method reporting limit of 

0.5 ppt. FGS may want to revise the analytical narrative to clarify this situation. 

In 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 
14

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, Derek, and Tyree, Corey A. Effect of FGD Chemistry on 

Wastewater Composition, presented at Air Quality VII 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 <33 
16

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