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: Pleasant Prairie Sampling Episode Report No. 6559 (June 20-25, 2010)

Dear Mr. Jordan: 

Thank you for the opportunity to comment on the draft Sampling Episode Report (SER) for the 

June 20-25, 2010 sampling event at Pleasant Prairie Power Plant. We Energies worked closely 

with the Utility Water Act Group (UWAG) to develop the following comments.

I. GENERAL COMMENTS

Incorporation of Additional Data Collected

In addition to the analytical results in the SER, Pleasant Prairie supplied four additional sets of 

samples taken in four separate months: September 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 EPA to supply the additional data as soon as reasonably 

possible, so that we can evaluate the entire data set in the proper context.

Data Usability

We Energies agrees with EPA’s efforts to identify and flag potentially erroneous (outlier) data 

points in the Pleasant Prairie 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 inaccuracy (bias) in the associated 

data. 

We Energies

231 W. Michigan St.

Milwaukee, WI 53203

www.we-energies.com
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Inadequate Treatment System Design and Operations Information

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

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

1. daily retention times for each stage of the treatment system; and

2. dimensions and water volume sizes for all individual components of the treatment 

system, including each holding tank, reaction tank, and clarifier.

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). We Energies urges EPA to 

integrate this information into the SER so that the data can be understood in the specific context 

of the Pleasant Prairie treatment system.

System Operations Information

In addition, EPA should provide information on the facility’s load on each of the sampling days. 

While the SER states the design megawatt capacity of Pleasant Prairie, 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 significant impact 

on flue gas desulfurization (FGD) system 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 

heating value of the coal being burned during the relevant period for the sampling event.

Dissolved Metals and Mercury Data

The accurate measurement of dissolved mercury (Hg) and metals in FGD wastewaters is 

challenging. EPA defines dissolved as metals or Hg associated with particles ≤ 0.45 m or ionic 

that will pass through a 0.45 m filter. This definition is an operational definition and there are 

many types of filters rated at 0.45 m (e.g. capsule, flat membrane, etc.). Metals and Hg 

associated with colloids (i.e. particles < 1 m in size and the vast majority < 0.45 m) can be an 

important fraction of the element present in FGD wastewaters. The fraction of < 0.45 m 

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 m colloids than do other filter types. This situation can lead to significant differences in 
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“dissolved” metals and Hg data depending on the filter used. EPA should consider this fact 

when evaluating and using dissolved metals or Hg data in developing the steam electric effluent 

guidelines.

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 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 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, heated, by method 1631E appendix A, etc.?

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

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 were the dissolved Hg samples filtered?

5. Was a bubbler-based 1631E approach used by EPA’s Hg laboratory?

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 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.

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.
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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 introduces arbitrarily estimated data into 

the calculations. A more consistent 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 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

Corrections

A handful of edits and corrections are marked within the body of the draft SER (attached). The 

most notable corrections are as follows:

 In Section 2. Facility Overview, the capacity should be stated as 594 MW net for each of 

the two generating units.

 In Section 2.1 FGD Scrubber System, the unit of measure for the rate of gypsum 

generation should be pounds per hour instead of tons per hour.

 In Section 2.2.1 Physical/Chemical Separation, the draft report incorrectly states that 

treated effluent was transferred to the Metal Cleaning Basin. While it is possible to send 

treated effluent to that basin, it has not been done. The effluent was instead directed to 

the filtrate sump to be recirculated to the scrubber.

Flow Data

A footnote below Table 3-3 requested that we provide the flow rate for the influent to the FGD 

wastewater treatment system from the secondary hydrocyclone as well as the hourly average 

flow rates for the effluent from the FGD wastewater treatment system. Accordingly, the hourly 

average flow rates for the effluent are provided in the attached Excel document. The influent 

flow rate is only available as an estimate of 60 gpm based on changes in the equalization tank 
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level during the sampling episode. These flow rates have been entered into Table 3-3 in the 

attached copy of the draft SER. 

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 comparable for SP2 but not SP-1 (see Table P4-1). The comparison suggests that the EPA data underestimates 

the total phosphorus concentration at SP-1. The analytical narrative in Appendix B indicates 

detectable phosphorus in the method blank for SP-1 samples but no MS/MSD analysis was 

performed on any of the SP-1 samples. The MS/MSD analysis on the EPA SP-2 sample 

produced low percent recoveries (i.e. 62% and 65%) indicating possible low bias caused by 

matrix interference and the sample was qualified as a minimum value. It is possible that a 

similar matrix interference was present in the EPA SP-1 samples and was responsible for the 

apparent underestimation of total phosphorus.

TABLE P4-1. 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 5.42 < 0.347

SP-2 0.05 < 0.0506

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 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 the SER data Appendix A, the ratio of QL (reporting limit) to MDL (detection limit) for EPA 

method 200.7 averages ~ 20 with a range of range ~ 3 to 55. The expected ratio is 3-5 as 

shown for EPA method 200.8 QL/MDL’s listed in the SER. The reason for this situation is not 

clear. Are the MDL’s too low or the QL’s too high for the elements with elevated ratios? 
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Many of the EPA chromium (Cr) data in the SER tables are qualified (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 (Appendix B) makes no mention of any quality control (QC) issues associated with the 

Cr analyses. Should the Cr data be flagged or not? 

We appreciate your consideration of our comments. Please contact me at (414) 221-2158 or by 

e-mail (David.Lee@we-energies.com) if you have any questions regarding our comments or 

attachments.

Sincerely,

David M. Lee, P.E.

Manager – Water Quality

Attachments:

1) We Energies Mark-up of SER

2) Excel Spreadsheet for Treatment Facility Flow Data