### Questions for Pleasant Prairie

The following questions relate to EPA’s review of the analytical d ata We Energies provided with

comments on the proposed effluent guidelines and in response to EPA’s request for additional data

.

1. Using the process flow diagram included in We Energies’ 2/10/2014 letter, please identify the

location for each sample point associated with data submitted with comments or in response to

EPA’s data request:

a. Data submitted with comments

i. Effluent from FGD Chemical Precipitation W astewater Treatment System

ii. Effluent from FGD Wastewater Treatment System (SP 102)

iii. Effluent from the FGD Chemical Precipitation Wastewater Treatment System

iv. Influent to FGD Chemical Precipitation Wastewater Treatment System

v. Influent to FGD Wastewater Treatme nt System (Reaction Tank #1 Influent)

vi. Influent to FGD Wastewater Treatment System (for Reaction Tank #1 Influent)

vii. Internal Point within the FGD Wastewater Treatment System (Primary Clarifier

Effluent)

viii. Internal p oint within the FGD Wastewater Treatment Syst em (Primary Clarifier

Effluent)

ix. Internal Point within the FGD Wastewater Treatment System (Secondary

Clarifier Effluent)

x. Internal point within the FGD Wastewater Treatment System ( Secondary

Clarifier Effluent)

b. Response to EPA’s data request

i. FGD Purge

ii. Secon dary C larifier

iii. Chem P rep . E ffluent

2. How were samples collected for the secondary clarifier?

3. Are all grab samples single grabs or are there composites of multiple grabs?

4. EPA was not able to verify the RL or d ilution factor in the lab reports

. H ow did Pleasant Prairie

obtain these values?

Anal ytical Data P rovided in C omments

5. Why was arsenic measured using Method 6020A, since it is not included in 40 CFR Part 136 as a

CWA

- approved method? (note that 6020A was also used to analyze samples of secondary

cl arifier effluent, provided in response to EPA’s data request)

6. As noted in the analytical spreadsheet, We Energies provided the average result when multiples

samples were collected from the same sampling location on the same day

.

a. There are several instanc es where the calculated average mercury value should end in a

decimal (i.e., XX.5) , which differs from the spreadsheet entry

. Do you agree the

discrepancy is due to We Energies round ing the value down to the nearest integer (see

Table 1) ?

### b. On a few days

, where multiple samples from the same sampling location were collected

for an analyte, the two samples were averaged together but the MDL for only one of the

individual samples was included in the analytical spreadsheet (see Table 2). Please

explain the re asoning for which MDL was provided in the analytical spreadsheet.

Table 1. Pleasant Prairie A ver aged V alues and E PA C alculated Average V alues

Type of Wastewater Date Analyte Procedure Units Non

Detect

Indicator Amount E PA

Calculated

Average

FGD WWTS Effluent

- SP 102 5/25/2010 Mercury Total ng/L D 374 374.5

FGD WWTS Effluent

- SP 102 6/9/2010 Mercury Total ng/L D 92 92.5

FGD WWTS Effluent

- SP 102 7/7/2010 Mercury Total ng/L D 94 94.5

FGD WWTS Effluent

- SP 102 11/23/2010 Mercury Total ng/L D 56 56.5

FGD WWTS Effluent

- SP 102 12/15/2010 Mercury Total ng/L D 64 64.5

FGD WWTS Effluent

- SP 102 6/21/2011 Mercury Total ng/L D 92 92.5

FGD WWTS Effluent

- SP 102 6/28/2011 Mercury Total ng/L D 68 68.5

FGD WWTS Effluent

- SP 102 7/13/2011 Mercury Total ng/L D 58 58.5

FGD WWTS Effluent

- SP 102 7/26/2011 Mercury Total ng/L D 92 92.5

FGD WWTS Effluent

- SP 102 12/28/2011 Mercury Total ng/L D 88 88.5

FGD WWTS Effluent

- SP 102 12/30/2011 Mercury Total ng/L D 100 100.5

FGD WWTS Effluent

- SP 102 11/13/2012 Mercury Total ng/L D 94 94.5

FGD WWTS Effluent

- SP 102 11/14/2012 Mercury Total ng/L D 88 88.5

FGD WWTS Effluent

- SP 102 4/10/2013 Mercury Total ng/L D 78 78.5

FGD WWTS Effluent

- SP 102 4/24/2013 Mercury Total ng/L D 80 80.5



### Table 2. Pleasant P rairie A veraged V alues with D ifferent MDL s for the Averaged Samples

Type of Wastewater Date Analyte Procedure Units Non

Detect

Indicator Amount MDL in

Data

Table MDL in

Lab

Report

FGD WWTS Effluent

- SP 102 8/5/2008 Mercury Total ng/L D 335 60 1.2, 60

FGD WWTS Effluent

- SP 102 5/24/2010 Mercury Total ng/L D 340 14 14, 15

Primary Clarifier Effluent 6/17/2008 Arsenic Total ug/L < [blank] 4.7 4.7, 2.4

,

2.4

Primary Clarifier Effluent 3/30/2009 Mercury Dissolved ng/L D 3,500 25 12, 25

### 7. There are s everal discrepancies between the MDL values reported in the analytical spreadsheet

compared to the MDL cited in the lab report (see Table 3) . Please confirm which MDL value is

correct for these data samples.

Table 3. Pleasant Prairie MDL V alue D iscrepancies between Analytical S preadsheet and L ab R eports

Type of Wastewater Date Analyte Procedure Units Non

Detect

Indicator Amount MDL in

Data

Table MDL in

Lab

Report

Reaction Tank #1 Influent 12/18/2007 Mercury Dissolved ng/L D 2,400 50 1

Reaction Tank #1 Influent 8/4/2008 Mercury Dissolved ng/L D 2,300 60 1.2

Secondary Clarifier

Effluent * 10/28/2008 Mercury Total ng/L D 530 16 0.63

Secondary Clarifier

Effluent 7/10/2009 Mercury Total ng/L D 340 12 0.5

Secondary Clarifier

Effluent 8/7/2009 Mercury Total ng/L D 410 14 0.57

Secondary Clarifier

Effluent 8/10/2009 Mercury Total ng/L D 470 14 0.57

Secondary Clarifier

Effluent 8/10/2009 Mercury Dissolved ng/L D 47 14 0.57

Primary Clarifier Effluent 11/19/2009 Mercury Dissolved ng/L D 220 25 28

Primary Clarifier Effluent 11/24/2009 Mercury Dissolved ng/L D 260 25 28

Primary Clarifier Effluent 12/21/2009 Mercury Dissolved ng/L D 730 25 28

Primary Clarifier Effluent 4/16/2010 Mercury Dissolved ng/L D 390 25 28

Primary Clarifier Effluent 5/5/2010 Mercury Dissolved ng/L D 440 25 28



### *Dump valve

8. The primary clarifier effluent and secondary clarifier effluent results for mercury from

11/6/2007 through 11/15/2007 and 3/30/2009 through 3/31/2009 note that “Jar testing may

have been conducted on this date.” Do these sample results represent the primary clarifier

effluent or the primary clarifier effluent after additional jar testing?

9. The secondary clarifier effluent results for mercury on 10/28/20 08, 10/29/2008, and 3/16/2009

notes that the sample is “Dump Valve.” What does this sample represent?

10. The secondary clarifier effluent result for mercury on 10/29/2008 notes that the sample is

“Sample Tap.” What does this sample represent?

### Analytical Da ta P rovided in Data Request

11. The total mercury and total mercury field duplicate for the FGD WWTS Effluent

– SP 102 on

8/6/2013 both have a reported MDL of 0.45 ng/L in the lab report . However, according to the

analytical spreadsheet, the MDL is reported as 11 ng/L. Because of the elevated MDL, the

duplicate sample was treated as a J

- value in the calculation of the average

. Which MDL value s

are correct? Should the duplicate sample be considered a J

- value?

12. For t he total m ercury result from the FGD WWTS Effluent

– SP 102 on 10/29/2013 , the native

and duplicate sample were averaged together. However, only the native sample MDL (18 ng/L)

was reported in the spreadsheet. The duplicate sam ple MDL was 0.72 ng/L . Please explain the

reasoning for why the native sample MDL was provided in the analytical spreadsheet.

Additional Questions

13. Pleasant Prairie stated that hydrochloric acid is added to Reaction Tank #2 at a dose

concentration of 0.012 g/L and dosage rate of 1.9 gpd. When did Pleasant Prairie begin adding

hydrochloric acid to Reaction Tank #2? ( EPA’s understanding is that during the initial operation

of the system, the plant was only adding hydrochloric acid downstream of the secondary

clarifier. )

14. Please provide a general timeline for the collection and analysis of the mercury samples that are

analyzed using the in

- plant analyzer (i.e., the DMA 80 Hg Analyzer). Please include enough

detail to answer the following questions:

a. Who collect s the mercury samples (e.g., position title)?

b. What type of handling procedures are used (i.e., are clean hands/dirty hands protocols

used)?

c. Where are the samples taken for analysis?

d. Who performs the analysis (e.g., position title)?

e. What type of experience is required to perform the analysis?

f. How long after the analysis is started are the results available?

g. How long after the sample is collected are the results available?

15. Would pollutant characteristics of the secondary clarifier effluent differ from phys

- chem

effluent (SP

- 102) ?

16. We observed several results at substantially higher concentrations relative to the other effluent

values. What was happening with plant processes, coal sources, treatment system operation?

What actions were taken in response to these observed concentrations?

a. Mercury data for 2007 at highly elevated concentrations

b. 1/31/11 (1440 ng/L) and 2/1/11 (970 ng/L)

– secondary clarifier (compare to data for

2/3 and 2/4)

c. 2/15/11 (78 0 ng/L) and 2/16/11 (615 ng/L)

– CP effluent

d. 3/18/11 (665 ng/L)

– CP effluent

e. 2/3/12 (815 ng/L) and 2/4/12 (705 ng/L)

– CP effluent

f. 6/13/12 (2900 ng/L)

– CP effluent

g. 6/18/12 (8300 ng/L)

– secondary clarifier

### h. 6/28/12 (640 ng/L)

– CP effluent

i. 1/3/13 (360 ng/ L clarifier effluent; 855 ng/L CP effluent)

17. What day did the plant switch from TMT

- 15 to Nalmet?