## MEMORANDUM

DATE: November 18 , 201 2

SUBJECT: Assessment of Effluent Limitations and Standards w ith No Baseline Substitution for the Steam Electric Rulemaking

TO: Steam Electric Rulemaking Record , USEPA

FROM: Ronald Jordan and Cuc Schroeder

, USEPA

Cc: John Rogers, Westat

Section 13 of the Technical Development Document ( TDD ) explains EPA’s procedure for calculating effluent limitations and standards (hereafter referred to as limitations ) . This

memo randum ad dresses the sensitivity of the l imitations to the substitution of certain low
concentration values with pollutant

- specific “ baseline ” values (i.e., baseline substitution )

. For each pollutant proposed to be regulated for each treatment technology option 1 

### for flue gas desulfurization (FGD ) wastewater 2 

### and gasification wastewater, t his memorandum provides a comparison between what the limitations would be using all valid reported results without
baseline substitution and the limitations calculated with baseline substitution incorporated

.

In developing the limitations for the s team e lectric r ulemaking , EPA used the detected
values or sample

- specific detection limit in the case where the pollutant was non

- detected 3



### . However

, there were instances where EPA substituted a baseline value for a detected value or sample

- specific detection limit. EPA used t he baseline value in the statistical ana lysis to
account for the possibility that certain detected results may be at concentration s that are lower than can be reliably measured when the analytical method(s) is performed by experienced staff

in a well

- operated laborator y

. 4

1 The option long

- term average and option variability factors in this memorandum refer to the treatment technology option rather than the regulatory options presented in Section 8 of the T DD

. 

### This approach is consistent with the way EPA ha s calculated
limitations in previous effluent guidelines. See, for example , the rulemakings for the Meat and

Pou ltry Products ELG and the Iron and Steel ELG.

2 Since EPA is proposing to establish limitations for combustion residual leachate based on transferring limitations calculated for FGD wastewater treatment technology option(s), the evaluation of baseline substi tution on FGD wastewater limitations similarly applies to the proposed limitations for combustion residual leachate. For brevity,
combustion residual leachate is referred to in this memorandum as leachate.

3 The term “non

- detected” refers to values that are below the method detection limit (MDL) and those measured by the laboratory as being between the MDL and the quantitation limit (QL) in the original data (before adjusting for baseline).

4 A well

- operated laboratory is a laboratory that routinely moni tors performance through quality control analyses, control charts, and other measures to rapidly identify and correct deteriorating or poor performance, and with analysts experienced with method sample preparation, analysis, and detection procedures.

### Page 2 

### EPA performed the baseline substitution as follows: EPA examined the data used to
calculate the limitations for each technology option and compared each reported result to a
bas eline value. When ever a detected value was lower than the baseline value, EPA used the
baseline value inst ead and classified the value as non

- detected even though the actual reporte d
result was a detected value

. Similarly, whenever a non

- detected value had a sample

- specific
de tection limit lower than the applicable baseline value, EPA used the baseline value inst ead
and continued to classif y the value as non

- detected

. The bullets below present the baseline
values that w e re used for each pollutant in this steam electric rulemaki ng :

o ar senic: 2 ug/L

o mercury: 0.5 ng/L

o nitrate

- nitrite as N: 0.05 mg/L

o selenium 5 ug/L

o TDS: 10 mg/L

EPA determined t he baseline values for mercury, nitrate

- nitrite as N, and TDS using the minimum levels (MLs) established by the analytical methods used to obtain the reported values or a comparable analytical method where an ML was not specified by the method. 5 

### The
baseline values for arsenic and selenium are based on the results of m eth od d etection l imit ( MDL ) studies conducted by well

- operated commercial laboratories using EPA Method 200.8 to analyze samples of synthetic FGD wastewater (for a detail discussion, see DCN SE03835).

EPA considers this historical approach of incorporating baseline substitution to be similarly appropriate for the steam electric ELG rulemaking. N evertheless, EPA conducted an
assessment to determine how the use of baseline substitution affected the calculation of the
limitations.

Appendix B of the TDD explains how EPA accounts for autocorrelation when calculating
limitations. A lso, a s explained in detail in Section 13 of the TDD , for all technology options except the biological treatment technology option for FGD wastewater, EPA was unable to
obtain re liable estimates for the autocorrelations since there were too few observations
available

, and t hus the autocorrelation value was set to zero

. For the biological treatment technology option for FGD wastewater, s ince several years of data were available

, EPA was able
to obtain an autocorrelation value for situations when either baseline substitution is or is not incorporated

. The autocorrelation values obtained with or without baseline substitution were used in calculating the limitations presented in tab les below . See DCN SE02001 for the
autocorrelation values used for each pollutant for these two cases; see DCN SE02002 for a list

5 Th e baseline values for mercury and nitrate

- nitrite as N are equal to the MLs specified in EPA Methods 1631E and

353.2 , respectively. The method EPA used to analyze for TDS (Standard Method 2540C) does not explicitly state a

MDL or ML. However, EPA Method 16 0.1 is similar to S tandard M ethod 2540C and the lower limit of its measurement range is 10 mg/L (i.e., the nominal quantitation limit ). Thus, EPA used 10 mg/L as the baseline value

for TDS

.

### Page 3 

### of data that were used to calculate the limitations ; and see Appendix B of the TD D for the
statistical model used to obtain t he long

- term average, v ariability factors, and limitations

.

Table 1 below presents the limitations obtained when incorporating baseline
substitution for detected and non

- detected values reported below the pollutant

- specific
baseline values shown in the bullets above. The limitations presented in Table 1 are the limitations proposed for this rulemaking , or calculated for other technology options considered for BAT/NSPS/PSES/PSNS

.

### Page 4 

### Table 1. Summary of the O ption Long

- Term Average s and Va riab ility Factor s T ogether with the

L imitations for Each of the FGD, Gasification, and Leachate Technology Options When Using
Baseline S ubstitution.

Treatment Technology Pollutant Option Long

- Term

Average Option Daily Variability

Factor Option Monthly Variability

Factor Daily

Maximum
Limitation 4 Monthly Average
Limitation 4

Chemical Precipitation
for FGD Arsenic (ug/L) 4.483 1.741 1.223 8 6 Mercury (ng/L) 75.404 3.209 1.570 242 119

Chemical Precipitation
and Biological

Treatment
for FGD Arsenic (ug/L) 1 4.483 1.741 1.223 8 6 Mercury (ng/L) 1 75.404 3.209 1.570 242 119

Nitrate

- nitrite as N (mg/L) 0.110 1.499 1.157 0.17 0.13

Selenium (ug/L) 7.455 2.145 1.321 16 10

Chemical Precipitation
and Evaporation for

FGD Arsenic (ug/L) 4.0 2

-- 3

-- 3 4 5

-- 6
Mercury (ng/L) 17.788 2.192 1.338 39 24 Selenium (ug/L) 5.0 2

-- 3

-- 3 5 5

-- 6
TDS (mg/L) 14.884 3.341 1.572 50 24

Vapor

- Compression Evaporation for
Gasification Arsenic (ug/L) 4.0 2

-- 3

-- 3 4 5

-- 6
Mercury (ng/L) 1.075 1.632 1.194 1.76 1.29
Selenium (ug/L) 146.780 3.083 1.545 453 227
TDS (mg/L) 15.209 2.483 1.389 38 22

Chemical Precipitation
for Leachate Arsenic (ug/L) 1 4.483 1.741 1.223 8 6 Mercury (ng/L) 1 75.404 3.209 1.570 242 119

1 : Option long

- term average , option variability factors, and limitations were transferred from chemical precipitation technology option for FGD wastewater.

2 : Long

- term average is the arithmetic mean since all observations were non

- detected.

3 : All observations were non

- detected, so variability factors could not be calculated.

4 : Limitations less than 1.0 are rounded up to the next highest hundredths decimal place. Limitations greater than 1.0 have been rounded upward to the next highest integer, except for limitations for

mercury in gasification wastewater based on the vapor

- compression evaporation treatment technology option which have been rounded up to the next highest hundredths decimal place.

5 : Limitation is set equal to the detection limit.

6 : Monthly average limitation is not established when the daily maximum limitation is based on the detection limit.



### Table 2 below presents what the limitations would be if the limitations are calculated using all valid reported results (i.e., no baseline substitution is made for values below the
baseline ) for each pollutant for each treatment technology option. Upon comparison of Tables
1 and 2

, the limitations calculated using baseline substitution are identi cal to the limitations calculated when baseline substitution is not used, except for nitrate

- nitrite as N and selenium in
FGD wastewater based on the biological and gasification wastewater based on the vapor

compression evaporation treatment technology opt ions

. The baseline affects the nitrate

- nitrite

### Page 5 

### as N limitation only because the baseline affects the selenium measurements and correlation and the selenium correlation is used for calculating the limitation for nitrate

- nitrite as N. T he
limitations for al l other pollutants are unaffected by baseline substitution since all values for these pollutants were above their respective baseline values. However, for completeness, thi s document presents the limitations for all pollutants considered for regulation under the various technology options for the rulemaking

.

Table 2. Summary of the O ption Long

- Term Average s and Va riab ility Factor s T ogether with the

L imitations for Each of the FGD, Gasification, and Leachate Technology Option s When Using No
Baseline S ubstitution

.

Treatment Technology Pollutant Option Long

Term Average Option Daily Variability

Factor Option Monthly Variability

Factor Daily

Maximum
Limitation

4 Monthly Average
Limitation

4
Chemical Precipitation

For FGD Arsenic (ug/L) 4.48 3 1.7 41 1.22 3 8 6 Mercury (ng/L) 75.4 04 3.2 09 1.57 0 242 119

Chemical Precipitation

and Biological

Treatment For FGD Arsenic (ug/L) 1 4.483 1.741 1.223 8 6 Mercury (ng/L) 1 75.404 3.209 1.570 242 119

Nitrate Nitrite as N (mg/L) 0.1 10 1.5 0 0 1.1 57 0.1 7 0.13

Selenium (ug/L) 6.992 2.927 1.510 21 11

Chemical Precipitation and Evaporation for

FGD Arsenic (ug/L) 4 .0 2

-- 3

-- 3 4 5

- - 6
Mercury (ng/L) 17.7 88 2.192 1.338 39 24 Selenium (ug/L) 4 .0 2

-- 3

-- 3 4 5

- - 6

TDS (mg/L) 14.88 4 3.34 1 1.57 2 50 24

Vapor

- Compression Evaporation for
Gasification Arsenic (ug/L) 4 .0 2

-- 3

-- 3 4 5

- - 6
Mercury (ng/L) 1.075 1.632 1.194 1.76 1.29
Selenium (ug/L) 146. 48 0 2.222 1. 331 326 195
TDS (mg/L) 15.209 2.483 1.389 38 22

Chemical Precipitation
for Leachate Arsenic (ug/L) 1 4.483 1.741 1.223 8 6 Mercury (ng/L) 1 75.404 3.209 1.570 242 119

1 : Option long

- term average , option variability factors, and limitations were transferred from chemical precipitation technology option for FGD wastewater.

2 : Long

- term average is the arithmetic mean since all observations were non

- detected.

3 : All observations were non

- detected, so variability factors could not be calculated.

4 : Limitations less than 1.0 are rounded up t o the next highest hundredths decimal place. Limitations greater than 1.0 have been rounded upward to the next highest integer, except for limitations for mercury based on the vapor

- compression evaporation treatment technology option for gasification waste water which have been rounded up to the next highest hundredths decimal place.

5 : Limitation is set equal to the detection limit.

6 : Monthly average limitation is not established when the daily maximum limitation is based on the detection limit.