MEMORANDUM

TO: Bill Swietlik, EPA

FROM: Jill Lucy, ERG

DATE: September 30, 2015

SUBJECT: Loadings Analysis for the Steam Electric ELGs Environmental Assessment

(DCN SE04446)

ERG supported the 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). As part of the environmental assessment 

(EA), ERG evaluated the environmental impact of pollutant loadings released under current (i.e., 

baseline) discharge practices and assessed the potential environmental improvement from 

pollutant loading removals associated with the regulatory options (Options A, B, C, D, and E).

1

The results of this analysis 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). ERG calculated 

pollutant loadings and removals under two separate industry baseline scopes: 

1. The “With CCR” scope accounts for the Coal Combustion Residuals (CCR) rulemaking. 

See the EA Report for the results of the analyses under this scope.

a. 222 immediate receiving waters included in the environmental assessment (195 

steam electric power plants).

2

b. 209 immediate receiving waters included in the IRW model used for the EA (188 

steam electric power plants).

2. The “With CCR and CPP” scope accounts for both 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.

 

1 During development 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.

2 EPA also calculated loadings for indirect discharges to publicly owned treatment works. Four of the 195 steam 

electric power plants discharge both directly and indirectly. There are also seven additional steam electric power 

plants that discharge indirectly only.
Memorandum

September 30, 2015

Page 2

a. 172 immediate receiving waters included in the environmental assessment (148 

steam electric power plants). 

b. 163 immediate receiving waters included in the IRW model used for the EA (143 

steam electric power plants).

This memorandum provides a summary of the data and calculations performed as part of 

the EA loadings analysis and includes the following sections: 

 Section 1: Background on Pollutant Loadings Methodology.

 Section 2: Industry Pollutant Loadings.

 Section 3: Comparison of Steam Electric Power Plant Pollutant Loadings to Publicly 

Owned Treatment Works Loadings.

 Section 4: Pollutant Loadings to Sensitive Environments.

 Section 5: Pollutant Removals Associated with the Regulatory Options.

 Section 6: References.

ERG developed the MS ExcelTM spreadsheet, EA Loadings Analyses (With CCR) (DCN 

SE04464) and the MS ExcelTM spreadsheet, EA Loadings Analyses (With CPP) (DCN 

SE04473), to support this analysis and perform the calculations. Results of the EA loadings 

analysis are presented in the EA Report.

1.0 BACKGROUND ON POLLUTANT LOADINGS METHODOLOGY

ERG calculated pollutant loadings on a plant-by-plant basis for all steam electric power 

plants that discharge one of the evaluated wastestreams and would achieve pollutant removals 

under the final ELGs. The evaluated wastestreams include flue gas desulfurization (FGD) 

wastewater, fly ash transport water, bottom ash transport water, and combustion residual 

leachate. The loadings methodology and calculations are documented in Section 10 of the EPA 

report, Technical Development Document for Effluent Limitations Guidelines and Standards for 

the Steam Electric Power Generating Point Source Category (TDD) (EPA-821-R-15-007) and 

the EPA report, Incremental Costs and Pollutant Removals for the Final Effluent Limitations 

Guidelines and Standards for the Steam Electric Power Generating Point Source Category 

(Costs and Loads Report) (DCN SE05831). The ERG memorandum, “Pollutant Loadings 

Supporting Documentation” (DCN SE04515), lists the resources developed to complete the EA 

loadings analysis.

Pollutant loadings are presented in the TDD, Costs and Loads Report, and the EA Report 

in two ways: pounds per year (lbs/yr) and toxic-weighted pound equivalents (TWPE) per year 

(lb-equivalent/yr). EPA developed TWPE to account for differences in toxicity across pollutants 

and provide the means to compare mass loadings of different pollutants on the basis of their toxic 

potential. To calculate TWPE, ERG multiplied the mass loading of each pollutant in pounds per 

year by its pollutant-specific toxic weighting factor (TWF). See the ERG memorandum “Review 

of Toxic Weighting Factors in Support of the Final Steam Electric Effluent Limitations 
Memorandum

September 30, 2015

Page 3

Guidelines and Standards” (DCN SE04479) for further details on TWFs and the use of TWPE in 

ELG development.

Table 1-1 presents the pollutants included in the loadings methodology. For the EA, ERG 

considered a subset of these pollutants. Specifically, ERG considered presence of the pollutant in 

the evaluated wastestreams; documented elevated levels of the pollutant in surface waters or 

wildlife from exposure to steam electric power plant wastewater; and magnitude of the pollutant 

loadings to receiving waters. 
Memorandum

September 30, 2015

Page 4

Table 1-1. Pollutants Included in the Steam Electric ELG Pollutant Loadings Analysis 

and EA Loadings Analyses

Pollutant

Associated Waste Streams Evaluated in EA

FGD 

Wastewater

Bottom Ash 

Transport 

Water

Fly Ash 

Transport 

Water

Combustion 

Residual 

Leachate

Included in EA Loadings Analyses

Aluminum X X X X

Arsenic X X X X

Boron X X X X

Cadmium X X X X

Chromium (VI) X X

Copper X X X X

Iron X X X X

Lead X X X

Manganese X X X X

Mercury X X X X

Nickel X X X X

Selenium X X X X

Thallium X X X X

Vanadium X X X X

Zinc X X X X

Chloride X X X X

Total dissolved solids (TDS) X X X X

Phosphorus, total X X X

Nitrate / Nitrite as N a X X X

Nitrogen, Total Kjeldahl a X X

Not Included in EA Loadings Analyses

Ammonia

See Section 10 of the TDD

Antimony

Barium

Beryllium

Biochemical oxygen demand

Calcium

Chemical oxygen demand

Chromium

Cobalt

Cyanide, total

Magnesium

Molybdenum

Silver

Sodium

Tin

Titanium

Total suspended solids

a – Included in analysis as total nitrogen. Total nitrogen is equal to nitrate/nitrite + Total Kjeldahl Nitrogen 

(TKN).
Memorandum

September 30, 2015

Page 5

2.0 POLLUTANT LOADINGS TO IMMEDIATE RECEIVING WATERS 

As discussed in Section 1.0 of this memorandum, the EA loadings analysis included only 

a subset of the pollutants included in the pollutant loadings calculations completed for the steam 

electric power generating point source category ELGs. To calculate the annual pollutant loadings 

(lbs/yr), ERG performed the following steps for the “With CCR” scope:

1. Calculated total loadings by pollutant and evaluated wastestream (in grams per day

(g/day)) as presented in Final Steam EA Loads Model (CCR) (DCN SE05620). 3

2. Converted the loadings from g/day to lbs/yr using the following conversion factor: 

[(lb/453.59 g) x (365 day/yr)].

3. Calculated total nitrogen loadings by adding nitrate/nitrite as N loadings and TKN 

loadings together.

4. Summed the evaluated wastestream loadings by pollutant to determine total steam 

electric power plant loadings for each pollutant.

Following calculation of the pollutant loadings for steam electric power plants (industry 

total), ERG multiplied each pollutant loading by the pollutant-specific TWF. This resulted in the 

annual TWPE (lb-eq/yr).

Section 3 (Table 3-2) of the EA Report presents the baseline annual pollutant loadings 

discharged in the evaluated wastestreams for select pollutants considered for analysis in the EA

(with CCR scope). The total industry loadings included in the table is based on pollutant loadings 

presented in Section 10 of the TDD.

To calculate the annual pollutant loadings (lbs/yr), ERG performed the following steps 

for the “With CCR and CPP” scope:

1. Calculated total loadings by pollutant and evaluated wastestream (g/day) as presented 

in Final Steam EA Loads Model (CPP) (DCN SE05622).

4

2. Converted the loadings from g/day to lbs/yr using the following conversion factor: 

[(lb/453.59 gram) x (365 day/yr)].

3. Calculated total nitrogen loadings by adding nitrate/nitrite as N loadings and TKN 

loadings together.

4. Summed the evaluated wastestream loadings by pollutant to determine total steam 

electric power plant loadings for each pollutant.

 

3

For the pollutant loadings and removals presented in this memorandum, ERG included indirect dischargers to 

protect confidential business information.

4

For the pollutant loadings and removals presented in this memorandum, ERG included indirect dischargers to 

protect confidential business information.
Memorandum

September 30, 2015

Page 6

Following calculation of the pollutant loadings for steam electric power plants (industry 

total), ERG multiplied each pollutant loading by the pollutant-specific TWF. This resulted in the 

annual TWPE (lb-eq/yr).

Appendix I (Table I-3) of the EA Report presents the baseline annual pollutant loadings 

discharged in the evaluated wastestreams for select pollutants considered for analysis in the EA 

(with CCR and CPP scope). The total industry loadings presented in the table are based on 

pollutant loadings presented in Section 10 of the TDD.

Comparison of Pollutant Loadings from Steam Electric Power Plants to Other Direct 

Dischargers

To provide perspective on the environmental impacts, ERG compared the TWPE 

loadings from the evaluated wastestreams at steam electric power plants to the other top point 

source category dischargers. Section 3 (Table 3-3) and Appendix I (Table I-4) of the EA Report

present the calculated TWPE loadings from the steam electric power industry under the baseline 

scopes, “with CCR” and “with CCR and CPP,” respectively.

ERG also compared the TWPE loadings from the evaluated wastestreams at steam 

electric power plants to other industrial discharges reported under NPDES permits. The TWPE 

discharges from the evaluated wastestreams from steam electric power plants totaled 2.68 

million lb-eq/yr (“with CCR” scope) and 2.14 million lb-eq/yr (“with CCR and CPP” scope). To 

determine pollutant loadings from non-steam electric industrial dischargers operating under 

NPDES permits, ERG used the loadings calculated by EPA as part of its 2012 Effluent 

Guidelines Program Plan and 2010 Effluent Guidelines Program Plan (see 

http://water.epa.gov/lawsregs/lawsguidance/cwa/304m/ for more details on this program). The 

source of the data for the 2012 Effluent Guidelines Program Plan was the discharge monitoring 

report (DMR) database, DMRLoadsAnalysis2009_v02.mdb (the database with tables and queries 

used for the steam electric ELGs is included in the record as DCN SE01961). The ERG 

memorandum, “Comparison of Steam Electric Industry Toxic Loadings to Other Industrial 

Dischargers” (DCN SE02155) presents the calculation of total TWPE from non-steam electric 

industrial sources reporting discharges under NPDES permits, which totals 5.3 million lb-eq/yr

[ERG, 2013a].

To calculate the contribution of steam electric power plants to toxic discharges from 

industrial point sources reporting under NPDES permits, ERG completed the following 

calculations:

1. Calculate total TWPE from all industrial sources reporting discharges under NPDES 

permits:

“With CCR” Scope

2.68 million lb-eq/yr (steam electric) + 5.3 million lb-eq/yr (non-steam electric) = 7.98 million lb-eq/yr
Memorandum

September 30, 2015

Page 7

“With CCR and CPP” Scope

2.14 million lb-eq/yr (steam electric) + 5.3 million lb-eq/yr (non-steam electric) = 7.44 million lb-eq/yr

2. Calculate percentage of TWPE (i.e., toxic discharges) accounted for by steam electric 

power plants:

“With CCR” Scope

2.68 million lb-eq/yr = 34 percent

7.98 million lb-eq/yr

“With CCR and CPP” Scope

2.14 million lb-eq/yr = 29 percent

7.44 million lb-eq/yr

3.0 COMPARISON OF EVALUATED WASTESTREAM LOADINGS FROM STEAM 

ELECTRIC POWER PLANTS TO THOSE FROM POTWS

ERG completed the following analyses to evaluate the pollutant loadings from evaluated 

wastestreams discharging from steam electric power plants:

1. Compared pollutant loadings to those from publicly owned treatment works 

(POTWs).

2. Compared average pollutant loadings by wastestream from a steam electric power 

plant to pollutant loadings discharged by a “typical” POTW.

The ERG memorandum, “Loadings Analysis for the Steam Electric ELGs Environmental 

Assessment” (DCN SE01956), presents the calculation of average discharge flow rate from a 

typical POTW (3 to 5 million gallons per day) and calculation of pollutant loadings from 

POTWs that discharge between 3 and 5 million gallons per day. ERG used the same POTW 

pollutant loadings but adjusted the TWPE for seven pollutants with whose TWFs had been 

revised since the memorandum was developed. Table 3-1 presents the POTW pollutant loadings 

from DCN SE01956 and the adjustment made to incorporate the revised TWFs.
Memorandum

September 30, 2015

Page 8

a – See the ERG memorandum, “Loadings Analysis for the Steam Electric ELGs Environmental Assessment” (DCN 

SE01956).

b – See the ERG memorandum, “Review of Toxic Weighting Factors in support of the Final Steam Electric Effluent 

Limitations Guidelines and Standards” (DCN SE04479).

Table 3-1. Revised Average POTW TWPE

Pollutant TWF (2013)

Average POTW 

Discharge 

(lb-eq/yr)a

Updated TWF

(Sept. 2015) b

Revised Average 

POTW Discharge 

(lb-eq/yr)

Aluminum 0.0647 215

Arsenic 4.04 186 3.47 159

Boron 0.00834 12.8

Cadmium 23.1 81.9 22.8 80.6

Chromium VI 0.517 9.02

Copper 0.635 97.0 0.623 95.3

Iron 0.00560 14.2

Lead 2.24 109

Manganese 0.070 24.8 0.103 36.1

Mercury 117 372,000 110 350,000

Nickel 0.109 3.06

Selenium 1.12 20.7

Thallium 1.03 10.1 2.85 28.2

Vanadium 0.0350 No data 0.280 No data

Zinc 0.0469 18.1

Nitrogen, total No value Not applicable

Phosphorus, total No value Not applicable

Chloride 2.435E-05 39.3

Total dissolved solids (TDS) No value No data
Memorandum

September 30, 2015

Page 9

3.1 Results of Comparison

To compare the total annual loadings from the evaluated wastestreams at the 195 steam 

electric power plants included in the EA loadings analysis to total annual loadings from POTWs, 

ERG determined the number of typical POTWs that would discharge the equivalent of the 

evaluated wastestreams for the 195 steam electric power plants. To calculate this, ERG divided 

the annual pollutant-specific loadings from the steam electric power plants by the annual 

pollutant-specific loadings of a typical POTW.5

For example, steam electric power plants (with CCR) discharge 140,000 pounds of 

selenium per year [see Section 3.2 (Table 3-2) of the EA Report]. A typical POTW discharges

18.5 pounds of selenium per year. The number of typical POTWs whose discharge of selenium is 

equivalent to the steam electric plant discharges is:

140,000 lb/yr = 7,570 POTWs (compared to 195 steam electric power plants)

18.5 lb/yr

Because TWPEs are calculated using the same TWF regardless of industry, the number 

of typical POTWs discharging the same TWPE as the 195 steam electric power plants is also 

7,570 POTWs. 

ERG completed the comparison using the MS ExcelTM spreadsheets, EA Loadings 

Analyses (With CCR) (DCN SE04464) and EA Loadings Analyses (With CPP) (DCN 

SE04473). Results of the POTW comparison are included in Section 3.2 (Table 3-5) and 

Appendix I (Table I-6) of the EA Report for the “with CCR” and “with CCR and CPP” scopes, 

respectively.

3.2 Comparison of Average Steam Electric Waste Stream Loadings to Typical POTW 

Loadings

ERG compared loadings for the evaluated wastestreams to those of a typical POTW. The 

evaluated wastestreams include FGD wastewater, fly ash transport water, bottom ash transport 

water, and combustion residual leachate. Error! Reference source not found.The EA Report 

presents average pollutant loadings for the evaluated wastestreams from a steam electric power 

plant and the annual pollutant loadings from a typical POTW.

 

5 Pollutant loadings for the EA analysis are included in the databases, Final Steam EA Loads Model (CCR) (DCN SE05620) and 

Final Steam EA Loads Model (CPP) (DCN SE05622). 
Memorandum

September 30, 2015

Page 10

Example calculation: The average FGD wastewater discharge of selenium equals 1,410

pounds per year from a single steam electric power plant. A typical POTW discharges 18.5

pounds of selenium per year. The number of POTWs whose discharge is equivalent to the 

average FGD wastewater discharge from a steam electric power plant (of selenium) is:

1,410 lb/yr = 76 POTWs (compared to 1 steam electric power plant)

 18.5 lb/yr

Because TWPEs are calculated using the same TWF regardless of industry, the number 

of typical POTWs discharging the same TWPE as the average FGD wastewater discharge from a 

steam electric power plant (of selenium) is also 76 POTWs.

ERG completed the comparison using the MS ExcelTM spreadsheets DCN SE04464 and 

DCN SE04473. See Section 3.2 (Table 3-4) of the EA Report for the “with CCR” results and 

Appendix I (Table I-5) of the EA Report for the “with CCR and CPP” results.

4.0 LOADINGS TO SENSITIVE ENVIRONMENTS

ERG evaluated pollutant loadings from evaluated waste streams that discharge to two 

sensitive watersheds, the Chesapeake Bay (an estuary) and the Great Lakes. For both watersheds, 

ERG identified steam electric power plants discharging the evaluated wastestreams to the 

watershed and their pollutant loadings at baseline. The ERG memorandum, “Proximity Analysis 

Methodology” (DCN SE04448) identifies the steam electric power plants and immediate 

receiving waters discharging to the watersheds. Pollutant loadings for the two watersheds are 

included in the following databases:

 Final Steam EA Proximity Analysis - Great Lakes and Chesapeake Bay Loads (CCR) 

(DCN SE04551) for the “with CCR” scope.

 Final Steam EA Proximity Analysis - Great Lakes and Chesapeake Bay Loads (CPP) 

(DCN SE05622) for the “with CCR and CPP” scope. 

The MS ExcelTM spreadsheets, DCN SE04464 and DCN SE04473, calculate the 

summation of the pollutant loadings presented in the EA Report. The baseline pollutant loadings 

for the two watersheds are included in the EA Report:

 Section 3.4.1 (Table 3-10) presents the baseline pollutant loadings to the Great Lakes 

watershed (with CCR). 

 Section 3.4.2 (Table 3-11) presents the baseline pollutant loadings to the Chesapeake 

Bay watershed (with CCR). 

 Appendix I (Table I-8) presents the baseline pollutant loadings to the Great Lakes 

watershed (with CCR and CPP). 

 Appendix I (Table I-9) presents the baseline pollutant loadings to the Chesapeake Bay 

watershed (with CCR and CPP).
Memorandum

September 30, 2015

Page 11

Pollutant removals for the Great Lakes watershed under the regulatory options and 

pollutant removals for the Chesapeake Bay watershed under the final rule are presented in 

Section 7.4.4 of the EA Report.

ERG also calculated pollutant removals from impaired waters. The ERG memorandum, 

“Proximity Analysis Methodology” (DCN SE04448) documents how ERG identified impaired 

waters. ERG used the databases, Final Steam EA IRW Model - Miscellaneous Calculations for 

EA Report (CCR) (DCN SE04604) and Final Steam EA IRW Model - Miscellaneous 

Calculations for Preamble and EA Report (CPP) (DCN SE04608), to identify the pollutant 

loadings to impaired waters under baseline and under the regulatory options. The MS ExcelTM 

spreadsheet, Pollutant Loadings to Impaired Waters (DCN SE06518) documents the analysis and 

calculations performed. Results are presented in Section 7.4.1 (Table 7-12) of the EA Report for 

“with CCR” scope and Appendix I (Table I-31) for the “with CCR and CPP” scope.

5.0 POLLUTANT REMOVALS ASSOCIATED WITH THE REGULATORY OPTIONS

To calculate the pollutant removals associated with the regulatory options, ERG 

performed the following steps 

1. Calculated total loadings by pollutant and evaluated wastestream (g/day) as presented 

in Final Steam EA Loads Model (CCR) (DCN SE05620) and Final Steam EA Loads 

Model (CPP) (DCN SE05622) for the treatment technologies.

2. Converted the loadings from g/day to lbs/yr using the following conversion factor: 

[(lb/453.59 g) x (365 day/yr)].

3. Summed the evaluated wastestream loadings by pollutant to determine total steam 

electric power plant loadings for each pollutant. The pollutant loadings used varied by 

option:

a. Option A: FGD wastewater (pollutant loadings based on chemical precipitation); 

fly ash transport water (dry option); bottom ash transport water (pollutant 

loadings equal to baseline); combustion residual leachate (pollutant loadings 

equal to baseline).

b. Option B: FGD wastewater (pollutant loadings based on biological treatment); fly 

ash transport water (dry option); bottom ash transport water (pollutant loadings 

equal to baseline); combustion residual leachate (pollutant loadings equal to 

baseline).

c. Option C: FGD wastewater (pollutant loadings based on biological treatment); fly 

ash transport water (dry option); bottom ash transport water (Option C treatment 

technology

6

); combustion residual leachate (pollutant loadings equal to baseline).

 

6 Dry handling/closed loop (for units >400 MW); impoundment (equal to BPT) for units ≤400 MW.
Memorandum

September 30, 2015

Page 12

d. Option D: FGD wastewater (pollutant loadings based on biological treatment); fly 

ash transport water (dry option); bottom ash transport water (dry option/closed 

loop); combustion residual leachate (pollutant loadings equal to baseline).

e. Option E: FGD wastewater (pollutant loadings based on biological treatment); fly 

ash transport water (dry option); bottom ash transport water (dry option/closed 

loop); combustion residual leachate (pollutant loadings based on chemical 

precipitation).

4. Calculated total nitrogen loadings by adding nitrate/nitrite as N loadings and TKN 

loadings together.

5. Multiplied by the TWFs to calculation TWPE per year for each option.

6. Calculated the pollutant removals for each option (baseline pollutant loadings minus 

Option pollutant loadings.

7. Calculated the percent reduction in pollutant loadings for each option compared to 

baseline.

ERG completed these calculations in the MS ExcelTM spreadsheets, DCN SE04464 and 

DCN SE04473. The results are presented in the EA Report:

 Section 7.1 (Table 7-3 and Table 7-4) presents the pollutant removals and percent 

reduction based on the regulatory options (with CCR). 

 Appendix I (Table I-22 and Table I-23) presents the pollutant removals and percent 

reduction based on the regulatory options (with CCR and CPP). 

6.0 REFERENCES

ERG. 2013a. “Comparison of Steam Electric Industry Toxic Loadings to Other Industrial 

Dischargers.” DCN SE02155.

ERG. 2013b. “Loadings Analysis for the Steam Electric ELGs Environmental Assessment.” 

DCN SE01956.

ERG. 2015a. EA Loadings Analyses (with CCR). MS ExcelTM spreadsheet. (July 24). DCN 

SE04464. 

ERG. 2015b. EA Loadings Analyses (with CPP). MS ExcelTM spreadsheet. (August 13).

DCN SE04473. 

ERG. 2015c. “Review of Toxic Weighting Factors in support of the Final Steam Electric 

Effluent Limitations Guidelines and Standards.” DCN SE04479.

U.S. EPA. 2010. Discharge Monitoring Report (DMR) Pollutant Loading Tool: 2010 Data. 

Available online at: http://cfpub.epa.gov/dmr/. DCN SE01959.
Memorandum

September 30, 2015

Page 13

U.S. EPA. 2011. Technical Support Document for the 2010 Effluent Guidelines Program Plan. 

EPA 821-R-09-006. Washington, DC. (October). DCN SE07320.

U.S. EPA. 2013. DMRLoadsAnalysis2009_v02.mdb: Tables and Queries Used for the Steam 

Electric Industry ELGs. DCN SE01961.