MEMORANDUM

TO: Steam Electric Rulemaking Record

FROM: Ryan Novak and Deb Bartram, ERG

DATE: 30 September 2015

SUBJECT: Steam Electric Effluent Guidelines Analytical Dataset – UWAG Bottom Ash 

Data – Final Deliverable

1. INTRODUCTION/BACKGROUND

EPA used data collected during the detailed study, industry-supplied data, and publicly 

available data sources, including data received during public comment, to develop the analytical 

dataset used to characterize bottom ash transport water and estimate the industry’s pollutant 

loadings. This memorandum describes the evaluation and use of data submitted by the Utility 

Water Act Group (UWAG).

Throughout the development of the effluent limitations guidelines and standards (ELGs), 

EPA coordinated with UWAG, an industry trade association representing 198 individual energy 

companies and three trade associations of energy companies. As part of this coordination, 

UWAG provided EPA with several bottom ash transport water analytical datasets for EPA’s 

consideration and use in the characterization of bottom ash transport water. The remainder of this 

section further describes these bottom ash transport water data submissions.

1.1 Form 2C Permit Application Data

During the detailed study of the steam electric power generating industry, EPA 

coordinated efforts with UWAG to create a database of selected National Pollutant Discharge 

Elimination System (NPDES) Form 2C data from UWAG’s member companies [UWAG, 2008].

The NPDES Form 2C database, compiled and generated by UWAG and provided to EPA,

contains information about the outfalls from 86 coal-fired power plants that discharge FGD, ash 

handling, or coal pile runoff wastestreams. All source water concentration data and plant outfall 

data were reviewed for possible inclusion in the ash pollutants of concern and loadings analyses.

EPA used information collected in Parts A and D of the Questionnaire for the Steam 

Electric Power Generating Effluent Guidelines (Steam Electric Survey) [U.S. EPA, 2010] to 

calculate the percent contribution of the ash transport water to the total outfall flow rate. EPA 

evaluated all references used to characterize ash impoundment discharge for the final rule and 

reviewed all data against the ash data acceptance criteria for the final rule outlined in Attachment 

1 of this memorandum. EPA included Form 2C data meeting all of these acceptance criteria in 

the bottom ash transport water pollutants of concern and pollutant loadings analyses for the final 

rule.
Memorandum

30 September 2015

Page 2

1.2 Data Submitted During Public Comment

As part of its public comment submission in September 2013, UWAG provided a table 

presenting bottom ash transport water data for samples collected from 21 plants [UWAG, 

2013a]. The UWAG samples date from 2001 to 2013, with samples from 17 of the plants 

collected between 2010 and 2013. In some cases, UWAG also provided source water data 

collected on the same sample day as the bottom ash transport water samples. As part of their 

public comment submission, UWAG also provided a report prepared by URS Corporation with 

2013 sampling data for sulfides (as well as some other parameters) at nine plants. UWAG 

masked the identity of all plants included in the bottom ash transport water database and sulfides 

report.

On December 30, 2013, EPA requested additional information and clarification from 

UWAG in order to properly interpret, validate, and evaluate the data to determine if these data 

met EPA’s acceptance criteria for inclusion in the pollutants of concern and pollutant loadings 

analyses. Specifically, EPA requested UWAG to provide more information about the identity of 

the sampled plants, the sample collection location and methods used, the selection criteria used 

by UWAG when developing their dataset, information on how nondetect values were handled

when calculating average concentrations, total suspended solids results associated with the 

samples, and other plant-specific information. In this request, EPA reminded UWAG that the 

Agency is operating with a deadline for taking final action on the steam electric ELGs and thus 

requested “additional information you provide in response to this letter be received by EPA no 

later than January 24, 2014” [U.S. EPA, 2013].

UWAG did not respond to EPA’s December 2013 information request until August 4, 

2014, more than six months after the EPA deadline. Although much later than the deadline, EPA 

was able to fully take these data into account for the analyses and evaluated the data submitted 

by UWAG against the acceptance criteria listed in Attachment 1 of this memorandum.

Consistent with EPA’s ash transport water acceptance criteria [ERG, 2015b], EPA used the data 

submitted by UWAG in the loadings analysis unless:

 Effluent from the ash impoundment sampled was comprised of less than 75 percent 

ash transport water by volume.

 Data were duplicative of other data accepted in the analytical database.

 Plants were not identified. For such plants, EPA could not confirm whether the 

samples met all the acceptance criteria because it did not have sufficient information 

about the sources and volumes of wastewater managed by the impoundment (i.e., 

EPA could not verify that the effluent to the ash impoundment sampled was at least 

75 percent ash transport water). Additionally, the lack of plant identification 

precluded EPA from evaluating whether the UWAG data were for impoundments 

already included in EPA’s Steam Electric Analytical Database.

 Samples did not represent actual effluent from an impoundment. EPA excluded data 

submitted by UWAG that attempted to simulate impoundment effluent, using samples 
Memorandum

30 September 2015

Page 3

that were collected prior to the ash pond and settled in a sampling container prior to 

analysis for a subset of the plants [UWAG, 2013b; UWAG, 2014a].

1

Where data were confirmed to represent ash impoundment effluent samples and the ash 

contribution was at least 75 percent of the contribution by volume to the impoundment, EPA 

included these data in the ash impoundment effluent concentrations data set and further reviewed 

the data against the acceptance criteria. EPA determined that the “simulated effluent” data were 

not wholly representative of ash impoundment discharges; therefore, these data were instead 

used in a sensitivity analysis. The Incremental Costs and Pollutant Removals for the Final 

Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point 

Source Category report [ERG. 2015c] further describes the use of data from UWAG’s public 

comment submission in the loadings analyses and sensitivity analyses and the results of these 

analyses.

1.3 November 2014 Bottom Ash Data

At UWAG’s request, on September 10, 2014, EPA met with representatives from UWAG 

to discuss the use of the bottom ash transport water data submitted by UWAG in public 

comments. During this meeting, UWAG indicated that it had collected additional bottom ash 

transport water characterization data. EPA stated that no further data were needed for EPA’s 

evaluation of bottom ash transport water [U.S. EPA, 2014].

On November 25, 2014, more than two months following the meeting with EPA on 

September 10, 2014, UWAG sent additional bottom ash transport water data and asked EPA to 

consider it for the final steam electric ELGs [UWAG, 2014b].

2 The late data included bottom ash 

transport water characterization data collected from six steam electric power plants. UWAG 

provided plant information sheets containing background and operational data regarding each of 

the plants sampled, analytical laboratory and quality control documentation for each sample, and 

the results of UWAG’s analysis of the results.

By November 25, 2014, EPA had already completed analysis of available ash 

characterization data for use in the rulemaking, completed development of the Steam Electric 

Analytical Database [ERG, 2015a], and finalized the ash loadings model used to generate 

pollutant loadings estimates. Therefore, EPA did not incorporate UWAG’s November 2014 data 

into the Ash Data Review Matrix, the pollutants of concern analyses, or official loadings analysis

[ERG, 2015b]. However, EPA did conduct a sensitivity analysis of the late data that were known 

to meet EPA’s acceptance criteria, as described further in Section 2.

 

1 UWAG presented a comparison of settled sluice pipe samples to near-effluent discharge point samples at each of 

the six plants sampled as part of the November 2014 submission. UWAG acknowledge that “whether viewed from 

the individual facility perspective or as averaged across the six facilities, it is clear that the settled bottom ash sluice 

pipe samples substantially overestimate bottom ash effluent pollutant loadings” [UWAG 2014b].

2 These data were received 10 months after the January 2014 deadline established by EPA’s December 30, 2013 

letter. This was 14 months after the September 2013 close of the comment period for the proposed rule (more than 

17 months after EPA publicly released a pre-publication version of the Federal Register notice for the proposed 

rule, soliciting additional pollutant characterization data). 
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30 September 2015

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2. SENSITIVITY ANALYSIS OF NOVEMBER 2014 UWAG DATA

As described in Section 1, EPA had sufficient time and information to evaluate and 

incorporate the Form 2C permit application data and bottom ash transport water data submitted 

in public comments (including those data submitted by UWAG) into the ash transport water 

loadings analyses. However, because UWAG’s late data were not sent to EPA until November 

2014, and due to the additional time that would have been needed to fully evaluate the late data 

and revise the pollutant removal analyses and other related analyses for the ELGs (e.g., 

environmental assessments), the late data could not be fully incorporated into the loadings

analyses. Nevertheless, EPA was able to conduct an abbreviated evaluation of the late data to 

determine the effect the late data could have on the loadings analyses [ERG, 2015d]. 

Based on the information submitted by UWAG with the November 2014 data and 

information submitted with previous data, EPA was able to confirm data from three of the six 

plants of UWAG’s November 2014 dataset came from impoundments that EPA had previously 

confirmed that contained ash transport water contributions of at least 75 percent, by volume 

(consistent with EPA’s acceptance criteria outlined in Attachment 1). 

3 EPA elected to further 

evaluate the data from these three plants against the acceptance criteria, compile it and use it in a 

sensitivity analysis, in combination with the datasets used in the loadings calculations, to 

determine the impact these data could have if factored into the industry-level bottom ash 

transport water loadings.

EPA did not fully evaluate or include data from the remaining three plants represented in 

UWAG’s November 2014 data set due to the unsolicited data being submitted well after the 

close of the comment period, limitations on time precluding EPA from evaluating whether the 

data met the acceptance criteria, and because the bottom ash transport water data were 

determined to be comparable to the analytical dataset used by EPA.

The results of the sensitivity analysis are presented in Table 1. This table illustrates the 

impact of including these late data on the total baseline industry loadings, accounting for the 

Coal Combustion Residuals (CCR) rule.

4

 

3

In prior submissions, UWAG provided information on Kammer, Kyger Creek Station, and Frank E. Ratts 

Generating Station that enabled EPA to readily ascertain the ash contribution for their impoundments. 

4 EPA conducted this sensitivity analysis on a previous version of the pollutant load estimates. EPA recalculated the 

industry loadings for fly ash transport water and bottom ash transport water for the final rule and determined that the 

difference between the final industry baseline loadings and the previous version of the pollutant loadings estimates 

is less than 1 percent in terms of pounds per year. Because the magnitude of this revision to the baseline loadings is 

very small and the sensitivity analyses also show little change in pollutant loadings/removals, EPA concluded that it 

was not necessary to update the sensitivity analysis with the revised baseline loadings because they would still show 

that there would be little change in the pounds of pollutants in the baseline loadings or removals.
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30 September 2015

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Table 1. Sensitivity Analysis Results for Total Industry Loadings Based on Inclusion of 

Late Submission UWAG Data Excluding BOD, COD, TSS, and TDS

Sensitivity Analysis

Total Industry Baseline Loadings

Pounds/Year Percent Difference (%)

Bottom Ash Transport Water Baseline Loadings 354,000,000 NA

Inclusion of Late Submission UWAG Bottom Ash Data a 347,000,000 (1.93%)

Source: ERG, 2015d; ERG, 2015e

Note: Excludes loadings for pollutants not identified as POCs and for BOD, COD, TSS, and TDS.

Note: Loadings are rounded to three significant figures.

Note: EPA completed this sensitivity analyses with a previous version of the ash analytical data set. Since the 

completion of this sensitivity analysis, EPA recalculated the industry loadings for fly ash transport water and bottom 

ash transport water and determined they are less than 1 percent different in terms of pounds per year for both waste 

streams. EPA determined that this 1 percent reduction in loadings, coupled with the approximately 2 percent change 

from inclusion of the late submission UWAG bottom ash data, was not significant enough to warrant reanalysis and 

the results of the sensitivity analysis would be comparable to the analysis presented.

a – EPA included results from three plants from the November 2014 data set where EPA had previously confirmed 

those ash contributions are at least 75 percent of the contribution, by volume, to the impoundment.

The sensitivity analysis demonstrates that including UWAG’s November 2014 data 

would have little impact on both the unweighted (pounds/year) pollutant loadings/removal 

estimates and other related analyses. Including the subset of the November 2014 data decreased 

the estimated unweighted pollutant loadings for bottom ash transport water by approximately 2

percent.

5 Because of the very small impact on bottom ash transport water loadings associated 

with this sample of late data, EPA concluded that the late data would not have a significant 

impact on the overall loadings, pollutant removal estimates, and related analyses for purposes of 

the final steam electric ELGs.

3. REFERENCES

1. ERG. 2015a. Eastern Research Group, Inc. Analytical Database for Final Rule. (30 

September). DCN SE05359.

2. ERG. 2015b. Eastern Research Group, Inc. “Ash Analytical Data Review 

Memorandum.” (30 September). DCN SE05567.

 

5 Error! Reference source not found. shows that including the November 2014 data reduces the estimated 

pollutant loadings that take the CCR rule into account by less than 2 percent. EPA also estimated pollutant loadings 

using an alternative approach that takes the effect of the Clean Power Plan (CPP) into account (see the Incremental 

Costs and Pollutant Removals for Final Effluent Limitation Guidelines and Standards for the Steam Electric Power 

Generating Point Source Category [ERG, 2015c]). Because the same pollutant concentration datasets are used for 

both sets of pollutant loadings/reduction estimates, the estimated pollutant loadings that take the CPP into account 

would be equally affected by incorporating the November 2014 data (i.e., unweighted loadings reduced by less than 

2 percent).
Memorandum

30 September 2015

Page 6

3. ERG. 2015c. Eastern Research Group, Inc. Incremental Costs and Pollutant Removals 

for the Final Effluent Limitations Guidelines and Standards for the Steam Electric Power 

Generating Point Source Category. (30 September). DCN SE05851.

4. ERG. 2015d. Eastern Research Group, Inc. “Draft Ash Loadings Model, Accounting for 

CCR – UWAG Late Submission Sensitivity Analysis.” (30 September). DCN SE05625.

5. ERG. 2015e. Eastern Research Group, Inc. “Draft Ash Loadings Model, Accounting for 

CCR – Sensitivity Analysis Comparison.” (30 September). DCN SE06418.

6. U.S. EPA. 2010. U.S. Environmental Protection Agency. Questionnaire for the Steam 

Electric Power Generating Effluent Guidelines. OMB Approval Number: 2040-0281. 

Washington, DC. (2 June). DCN SE00402-SE 00402A09.

7. U.S. EPA. 2013. U.S. Environmental Protection Agency. Post Proposal Data Request to 

UWAG – Bottom Ash Data Submitted in Public Comment. (30 December). DCN 

SE04711.

8. U.S. EPA. 2014. U.S. Environmental Protection Agency. Meeting Notes for the Steam 

Electric Rulemaking Record, September 10, 2014 Meeting with Utility Water Act Group 

(UWAG) Regarding Proposed Steam Electric ELGS. (10 September). DCN SE05578.

9. UWAG. 2008. Utility Water Act Group. UWAG Form 2C Effluent Guidelines Database. 

(30 June). DCNs SE02918 and SE02918A1.

10. UWAG. 2013a. Utility Water Act Group. Comments on EPA’s Proposed Effluent 

Limitations Guidelines and Standards for the Steam Electric Power Generating Point 

Source Category. (7 June). EPA-HQ-OW-2009-0819-4655.

11. UWAG. 2013b. Utility Water Act Group. UWAG Bottom Ash Transport Water 

Sampling Protocol. DCN SE04360A22.

12. UWAG. 2014a. Utility Water Act Group. UWAG Response to Post Proposal Information 

Request. (1 August). DCN SE04717.

13. UWAG. 2014b. Utility Water Act Group. Additional Bottom ash Transport Water Data. 

(25 November). DCN SE05597.
Memorandum

30 September 2015

Attachment 1

Attachment 1. Ash Transport Water Acceptance Criteria for Use of Data in Ash Loadings 

Analysis

ERG used the following data acceptance criteria to review and evaluate analytical data 

used to characterize ash transport water discharged from surface impoundments. Each dataset 

was specifically reviewed and flagged as acceptable for EPA’s ash effluent loadings calculations 

based on the following: 

 Sample locations must be unambiguous and clearly described such that it can be 

categorized by type (e.g., bottom ash impoundment effluent rather than 

impoundment effluent with no further definition) and level of treatment (e.g., 

untreated, partially treated).

 Sample must comprise at least 75% by volume ash transport water.

 Sample must be representative of actual ash impoundment effluent (not simulated 

effluent). 

 Analytical data must represent individual sample results or plant-level average 

sample concentrations rather than average results representing multiple plants.

 For biphasic samples (i.e., those with solids content >1%), sample analysis must 

provide results for both phases.

 Data must not be from an ash settling test conducted in a column (i.e., a simulated 

sample of partially treated wastewater).

 Sample must be representative of full-scale, typical plant operations.

 Sample analysis must be completed using accepted analytical methods.

6

 Data must not be duplicative of other accepted data.7

 Sample data must provide sufficient information to identify units.

 Non-detect results were not accepted if no limit (e.g., DL, QL) was provided.

 Sample results must represent total (i.e., dissolved results were not accepted 

except for TDS).

 

6 Methods prescribed in 40 CFR Part 136; Methods 200.7, 200.8, or 1638 for Metals analysis; and Methods 1631 

and/or 245.7 for Mercury (Method 245.1 is not acceptable because it is not sufficiently sensitive to measure 

concentrations of mercury in impoundment effluent).

7 Duplicate data were submitted by associations representing individual plants (e.g., UWAG). In such cases, EPA 

used the data submitted by the individual plant.