## MEMORANDUM

TO: Steam Electric Point Source Category ELG Rulemaking Record

FROM: Jill Lucy , ERG

DATE: September 29, 2015

SUBJECT: Water Quality Module Supporting Documentation ( DCN SE 0 4451 )

1.0 S UMMARY OF 

### S UPPORTING 

### D OCUMENTATION


### ERG supported t he U.S. Environmental Protection Agency (EPA) in the development of final effluent limitations guidelines and standards (ELGs) for the Steam Electric Power Generating Point Source Category (40 CFR Part 423). ERG developed the following resources to calcula te pollutant concentrations in the water column and sediment of the immediate receiving water and evaluate the impacts that receiving water concentrations pose to aquatic life and human health under current ( i.e. , baseline) discharge practices and potentia l improvement s associated with the r egulatory options (Options A, B, C, D, and E)

. 1



###  Immediate Receiving Water (IRW) Model: Water Quality Mod ule.

 IRW Model: Water Quality Module Comparisons Database.

 IRW Model: Water Quality Module Summary Tables Database

.

 IRW Model: Water Quality Module Summary Tables Spreadsheet.

The results of these analyses are presented in the Environmental Assessment for the Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (EA Report), Document No. EPA

- 821

- R

- 15

- 006 (DCN SE04527)

. The methodology of the IRW model: water quality module is presented in the following documentation:

 Water Quality Mod ule : Plant and Receiving Water Characteristics (DCN SE0 4513 )

– This memorandum specifies the methodology used to identify the characteristics of the immediate receiving waters evaluated in the water quality mod ule

.

 Pollutant Loadings Supporting Documentation (DCN SE 0 4515 )

– This memorandum identifies the supporting documentation used to calculate the pollutant loadings evaluated in the water quality mod ule

.

1 During develop ment of the final rule, EPA decided not to base the final rule on Option F for existing sources due primarily to the high cost of that Option, particularly in light of the costs associated with other rulemakings expected to impact the steam electric power generating industry (see Section VIII.C.1 of the preamble). As a result, EPA chose not to conduct particular analyses for Option F to the same extent that it did for some of the other options considered.

### Mem

orandum September 29, 2015 Page 2

 EA Report

, Section 5.1.1 ( Water Quality Module)

– This section provides an

overview of the water quality module

.

 EA Report, Appendix C (W ater Quality Model Methodology)

– This appendix presents the model equations, input values, pollutant benchmarks, and methodology limitations/assumptions

. ERG completed modeling under two separate industry baseline scopes:

1. The “With CCR ” scope accounts for the Coal Co mbustion Residuals (CCR) rulemaking. See the EA Report for the results of the analyses under this scope: 209 immediate receiving waters included in th e IRW model used for the EA (188 steam electric power plants).
2. The “With CCR and CPP” scope accounts for b oth the CCR rulemaking and the Clean Power Plan [Clean Air Act Section 111(d)]. See Appendix I of the EA Report for the results of the analyses under this scope: 163 immediate receiving waters included in the IRW model used for the EA (143 steam electric p ower plants)

.
The results of the IRW model: water quality mod ule are presented in the following sections of the EA Report :

 Section 6.1 (Water Quality Impacts)

.

 Section 7 .2 (Key Environmental Improvements)

.

 Section 7 .3 (Pollutant

- Specific Improvements)

.

 Section 9 (Conclusions)

.

 Appendix H ( Additional Model Results).

 Appendix I (Analysis for Alternate Scenario with Clean Power Plan).

Table 1 presents a comprehensive listing of the IRW model: water quality module supporting documentation for the “With CCR” scope

. Table 2 presents a comprehensive listing of the IRW model: water quality module supporting documentation for the “With CCR and CPP”
scope. Th e table s provide the doc ument control number (DCN), title, and description of each record item, and identif

y wh ether the record item contains C onfidential Business Information (CBI).

Table 1

. IRW Model: Water Quality Module Record Items

– With CCR

DCN Title (Date) Description CBI a
SE04552 Final Steam EA IRW

Model

- Water Quality Module

- Baseline (CCR) (050615) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under baseline conditions. Generates inputs for the wildlife and human health module. This version accounts for the CCR rulemaking. Yes

### Mem

orandum September 29, 2015 Page 3

Table 1

. IRW Model: Water Quality Module Record Items

– With CCR

DCN Title (Date) Description CBI a
SE04552A1 Final Steam EA IRW

Model

- Water Quality Module

- Option A (CCR) (050615) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under Option A. Generates inputs for the wildlife and human health module. This version accounts for the CCR rulemaking

. Yes

SE04552A2 Final Steam EA IRW

Model

- Water Quality Module

- Option B (CCR) (050615) Database used to calculate the total and dissolved receiving water concentrations a nd total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immedia te discharge zone under Option B . Generates inputs for the wildlife and human health module. This version accou nts for the CCR rulemaking

. Yes

SE04552A3 Final Steam EA IRW

Model

- Water Quality Module

- Option C (CCR) (050615) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pol lutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under Option C . Generates inputs for the wildlife and human health module. This version accounts for the CCR rulemaking

. Yes

SE04552A4 Final Steam EA IRW

Model

- Water Quality Module

- Option D (CCR) (050615) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for
aqu atic life and human health in the immedia te discharge zone under Option D . Generates inputs for the wildlife and human health module. This version accounts for the CCR rulemaking

. Yes

SE04552A5 Final Steam EA IRW

Model

- Water Quality Module

- Option E (CCR) (050615) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immedia te discharg e zone under Option E . Generates inputs for the wildlife and human health module. This version accounts for the CCR rulemaking

. Yes

SE04553A1 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option A (CCR) (050615) Database used to compare the water quality module results between baseline and Option A. Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR rulemaking. Yes

SE04553A2 Final Steam EA IRW

Model

- Water Quality Mod ule

- Comparison Database

- Option B (CCR) (050615) Database used to compare the water quality module resul ts between baseline and Option B . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR rulemaking

. Yes

SE04553A3 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option C (CCR) (050615) Database used to compare the water quality module resul ts between baseline and Option C . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR rulemaking. Yes

### Mem

orandum September 29, 2015 Page 4

Table 1

. IRW Model: Water Quality Module Record Items

– With CCR

DCN Title (Date) Description CBI a
SE04553A4 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option D (CCR) (050615) Database used to compare the water quality module resul ts between base line and Option D . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR rulemaking. Yes

SE04553A5 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option E (CCR) (050615) Database used to compare the water quality module resul ts between baseline and Option E . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR rulemaking. Yes

SE04554A1 Final Steam EA IRW

Model

- Water Qu ality Module

- Summary Table Generator (CCR) (050615) Database used to summarize the water quality module results for baseline and regulatory options. Generates the Water Quality Model Summary Tables spreadsheet. This version accounts for the CCR rulemakin g. No

SE04554A2 Final Steam EA IRW

Model

- Water Quality Module

- Summary Tables (CCR) (050615) Spreadsheet that summarizes the water quality module results for baseline and regulatory options. This version accounts for the CCR rulemaking. No

a

– Record items containing CBI have b een removed from the public re cord

.



### Table 2

. IRW Model: Water Quality Module Record Items

– With CCR and CPP

DCN Title (Date) Description CBI a
SE04568 Final Steam EA IRW

Model

- Water Quality Module

- Baseline (CPP) (061515) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under baseline conditions. Generates inputs for the wildlife and human health module. This version accounts for the CCR and CPP rulemakings. Yes

SE04568A1 Final Steam EA IRW

Model

- Water Quality Module

- Option A (CPP) (061515) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under Option A. Generates i nputs for the wildlife and human health module. This version accounts for the CCR and CPP rulemakings. Yes

SE04568A2 Final Steam EA IRW

Model

- Water Quality Module

- Option B (CPP) (061515) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immedia te discharge zone under Option B . Generates inputs for the wildlife and human health mod ule. This version accounts for the CCR and CPP rulemakings. Yes

### Mem

orandum September 29, 2015 Page 5

Table 2

. IRW Model: Water Quality Module Record Items

– With CCR and CPP

DCN Title (Date) Description CBI a
SE04568A3 Final Steam EA IRW

Model

- Water Quality Module

- Option C (CPP) (061515) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under Opti on C . Generates inputs for the wildlife and human health module. This version accounts for the CCR and CPP rulemakings. Yes

SE04568A4 Final Steam EA IRW

Model

- Water Quality Module

- Option D (CPP) (061515) Database used to calculate the total and di ssolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immediate discharge zone under Option D . Generates inputs for the wildlife and human health module. This version accounts for the CCR and CPP rulemakings. Yes

SE04568A5 Final Steam EA IRW

Model

- Water Quality Module

- Option E (CPP) (061515) Database used to calculate the total and dissolved receiving water concentrations and total sediment concentrations and to identify pollutant concentrations that exceed benchmarks for aquatic life and human health in the immedia te discharge zone under Option E . Generates inputs for the wildlife and human health module. This version accounts for the CCR and CPP rulemakings. Yes

SE04569A1 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option A (CPP) (061515) Database used to compare the water quality module results between baseline and Option A. Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR and CPP rulemakings. Yes

SE04569A2 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option B (CPP) (061515) Database used to compare the wat er quality module results between baseline and Option B . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR and CPP rulemakings. Yes

SE04569A3 Final Steam EA IRW

Model

- Water Quality Module

- Comp arison Database

- Option C (CPP) (061515) Database used to compare the water quality module results between baseline and Option C . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR and CPP rulemakings. Yes

SE04569A4 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option D (CPP) (061515) Database used to compare the water quality module results between baseline and Option D . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR and CPP rulemakings. Yes

SE04569A5 Final Steam EA IRW

Model

- Water Quality Module

- Comparison Database

- Option E (CPP) (061515) Database used to compare the water quality module results bet ween baseline and Option E . Generates inputs for the Water Quality Module Summary Table Generator. This version accounts for the CCR and CPP rulemakings. Yes

### Mem

orandum September 29, 2015 Page 6

Table 2

. IRW Model: Water Quality Module Record Items

– With CCR and CPP

DCN Title (Date) Description CBI a
SE04570A1 Final Steam EA IRW

Model

- Water Quality Module

- Summary Table Generator (CPP) (061515) Database used to summarize the water quality module results for baseline and regulatory options. Generates the Water Quality Model Summary Tables spreadsheet. This version accounts for the CCR and CPP rulemakings. No

SE04570A2 Final Steam EA IRW

Model

- Water Quality Module

- Summary Tables (CPP) (061515) Spreadsheet that summarizes the water quality module results for baseline and regulatory options. This version accounts for the CCR and CPP rulemakings. No

a

– Record items containing CBI have b een removed from the public re cord.



### 2.0 CORRECTIONS TO THE IRW MODEL

As an outcome from the public review and comment process, ERG incorporate d the following correction to the IRW model: water quality module :

 ERG corrected the water quality module partition coefficients for each of the ten modeled pollutants, which are presented in Table C

- 4 of Appendix C to the EA Report. These coefficients were selected from EPA’s Partition Coefficients for Metals in Surface Water, Soil, and Waste (Final) (EPA

- 600

- R

- 05

- 074) ( DCN SE01892 ) , which presents the coefficients in logarithmic form ( i.e. , the values presented are the logarithm of the partition coefficient). The water quality module incorporated these values without fir st converting them from logarithmic form to linear form. This resulted in an underestimate of the amount of pollutant sorbed to suspended sediment and bottom sediment and an overestimate of dissolved pollutant concentrations in the water column. ERG correc ted this error by converting the coefficients to linear form prior to incorporation into the water quality module

.