water use associated with wet sluicing BA operating systems. The 2015
rule baseline requires zero discharge of pollutants in BA transport
water, and because the use of other wastewater could significantly
increase the necessary purge flow to maintain water chemistry, the EPA
estimated the increase in water use for BA handling associated with
Options 1, 2, 3, and 4 compared to baseline as equal to the BA purge
flow.
    Two of the three technology bases for FGD wastewater included in
the regulatory options in today's proposal, chemical precipitation and
chemical precipitation plus LRTR, are not expected to reduce or
increase the amount of water use. Facilities that install a membrane
filtration system for FGD wastewater treatment under Option 2 or 3 as
part of the VIP option, or under Option 4, are assumed to decrease
water use compared to baseline by recycling all permeate back into the
FGD system, which would avoid costs of pumping or treating new makeup
water. Therefore, the EPA estimated this reduction in water use
resulting from membrane filtration treatment based on the estimated
volume of the permeate stream from the membrane filtration system.
Table X-6 sums the changes for FGD wastewater and BA transport water
and shows the net change in water use, compared to baseline, for the
proposed regulatory options.

  Table X-6--Estimated Incremental Changes to Water Use Associated With Regulatory Options Compared to Baseline
----------------------------------------------------------------------------------------------------------------
                                                    Changes to water use associated with regulatory options
          Non-water quality impact           -------------------------------------------------------------------
                                                  Option 1         Option 2         Option 3         Option 4
----------------------------------------------------------------------------------------------------------------
Changes in Water Use (gallons/year).........       3,370,000       21,100,000          613,000       -9,380,000
----------------------------------------------------------------------------------------------------------------

XI. Environmental Assessment

A. Introduction

    The EPA conducted an environmental assessment for this proposed
rule. The environmental assessment reviewed currently available
literature on the documented environmental and human health impacts of
steam electric power facility FGD wastewater and BA transport water
discharges and conducted modeling to determine the impacts of pollution
from the universe of steam electric facilities to which the steam
electric ELGs apply. For the reasons described in Section VIII of this
preamble, in conducting these analyses, the baseline appropriately
evaluates environmental and human health impacts of achieving the 2015
rule requirements as the EPA is analyzing the impact resulting from any
changes to those requirements compared to the 2015 rule (the same
baseline used to evaluate costs). More specifically, the EPA considered
the change in impacts associated with the regulatory options presented
in Table VII-1 in relation to those projected under the baseline.
    Information from the EPA's review of the scientific literature and
documented cases of impacts of steam electric power facility FGD
wastewater and BA transport water discharges on human health and the
environment, as well as a description of the EPA's modeling methodology
and results, are provided in the Supplemental Environmental Assessment
(Supplemental EA). The Supplemental EA contains information on
literature that the EPA has reviewed since the 2015 rule, updates to
the modeling methodology and modeling results for each of the
regulatory options in today's proposal. The 2015 EA provides
information from the EPA's earlier review of the scientific literature
and documented cases of the full spectrum of impacts associated with
the wider range of steam electric power facility wastewater discharges
addressed in the 2015 rule on human health and the environment, as well
as a full description of the EPA's modeling methodology.
    Current scientific literature indicates that untreated steam
electric power facility wastewaters, such as FGD wastewater and BA
transport water, contain large amounts of a wide range of pollutants,
some of which are toxic and bioaccumulative, and which cause
detrimental environmental and human health impacts. For additional
information, see Section 2 of the Supplemental EA. The EPA also
considered environmental and human health effects associated with
changes in air emissions, solid waste generation, and water
withdrawals. Sections X and XII discuss these effects.

B. Updates to the Environmental Assessment Methodology

    The environmental assessment modeling for today's proposed rule
consisted of the steady-state, national-scale immediate receiving water
(IRW) model that was used to evaluate the direct and indirect
discharges from steam electric facilities in the 2015 final ELG rule
and 2015 final CCR rule.\92\ The model focused on impacts within the
immediate surface waters where the discharges occur (approximately 0.5
to 6 miles from the outfall). The EPA also modeled receiving water
concentrations downstream from steam electric power facility discharges
using a downstream fate and transport model (see Section XII of this
preamble).
---------------------------------------------------------------------------

    \92\ These rules modeled the same waterbodies for which the
model was peer reviewed in 2008.
---------------------------------------------------------------------------

    The environmental assessment also incorporates changes to the
industry profile outlined in Section V of this preamble. Additionally,
the EPA updated and improved several input parameters for the IRW
model, including receiving water boundaries and volumetric flow data
from National Hydrography Dataset Plus (NHDPlus) Version 2, updated
national recommended water quality criteria (WQC) for cadmium and
selenium, updated benchmarks for ecological impacts in benthic
sediment, and an updated bioconcentration factor for cadmium.

C. Outputs From the Environmental Assessment

    The EPA estimates small environmental and ecological changes
associated with changes in pollutant loadings for the regulatory
options presented in Table VII-1 as compared to the baseline, including
small changes in impacts to wildlife and humans. More specifically, in
addition to other unquantified environmental changes, the environmental
assessment evaluated changes in (1) surface water quality, (2) impacts
to wildlife, (3) number of receiving waters with potential human health
cancer risks, (4) number of receiving waters with potential to cause
non-cancer human health effects, and (5) nutrient impacts.
    The EPA focused its quantitative analyses on the changes in
environmental and human health impacts associated with exposure to
toxic bioaccumulative pollutants via the surface water pathway. The EPA
modeled changes in discharges of toxic, bioaccumulative pollutants from
both FGD wastewater and BA transport water into rivers and streams and
lakes and ponds, including reservoirs. The EPA addressed environmental
impacts from nutrients in a separate analysis discussed in Section XII
of this preamble.
    The environmental assessment concentrates on impacts to aquatic
life based on changes in surface water quality; impacts to aquatic life
based on changes in sediment quality within surface waters; impacts to
wildlife from consumption of contaminated aquatic organisms; and
impacts to human health from consumption of contaminated fish and
water. The Supplemental EA discusses, with quantified results, the
estimated environmental changes projected within the immediate
receiving waters due to the estimated pollutant loading changes
associated with the regulatory options in today's proposal compared to
the 2015 rule. All of the modeled changes are small in magnitude.

XII. Benefits Analysis

    This section summarizes the EPA's estimates of the changes in
national environmental benefits expected to result from potential
changes in steam electric facility wastewater discharges described in
Section IX of this preamble, and the resultant environmental effects,
summarized in Section XI. The Benefit Cost Analysis

(BCA) report provides additional details on the benefits methodologies
and analyses, including uncertainties and limitations. The analysis
methodology for quantified benefits is generally the same as that used
by the EPA for the 2015 rule, but with revised inputs and assumptions
that reflect updated data. The EPA has updated the methodology from the
Stage 2 Disinfection Byproduct Rule for estimating benefits of reducing
bladder cancer incidence related to bromide discharges from steam
electric facilities and associated brominated disinfection by-product
formation at drinking water treatment facilities.

A. Categories of Benefits Analyzed

    Table XII-1 summarizes benefit categories associated with the
proposed regulatory options and notes which categories the EPA was able
to quantify and monetize. Analyzed benefits fall into six broad
categories: Human health benefits from surface water quality
improvements, ecological conditions and effects on recreational use
from surface water quality changes, market and productivity benefits,
air-related effects, and changes in water withdrawal. Within these
broad categories, the EPA was able to assess changes in the benefits
projected for the regulatory options in today's proposal with varying
degrees of completeness and rigor. Where possible, the EPA quantified
the expected changes in effects and estimated monetary values. However,
data limitations, modeling limitations, and gaps in the understanding
of how society values certain environmental changes prevent the EPA
from quantifying and/or monetizing some benefit categories. In the
following discussion, positive benefit values represent improvements in
environmental conditions and negative values represent forgone benefits
of the proposed options compared to the baseline.

 Table XII-1--Summary of Benefits Categories Associated With Changes in Pollutant Discharges From Steam Electric
                                                   Facilities
----------------------------------------------------------------------------------------------------------------
                                                                 Quantified but not      Neither quantified nor
         Benefit category           Quantified and monetized          monetized                 monetized
----------------------------------------------------------------------------------------------------------------
                            Human Health Benefits from Surface Water Quality Changes
----------------------------------------------------------------------------------------------------------------
Changes in incidence of bladder     [check].................  ........................  ........................
 cancer from exposure to total
 trihalomethanes (TTHM) in
 drinking water.
Changes in incidence of cancer      [check].................  ........................  ........................
 from arsenic exposure via fish
 consumption.
Changes in incidence of             ........................  ........................  [check]
 cardiovascular disease from lead
 exposure via fish consumption.
Changes in incidence of other       ........................  [check].................  [check]
 cancer and non-cancer adverse
 health effects (e.g.,
 reproductive, immunological,
 neurological, circulatory, or
 respiratory toxicity) due to
 exposure to arsenic, lead,
 cadmium, and other toxics from
 fish consumption or drinking
 water.
Changes in IQ loss in children      [check].................  ........................  ........................
 from lead exposure via fish
 consumption.
Changes in need for specialized     [check].................  ........................  ........................
 education for children from lead
 exposure via fish consumption.
Changes in in utero mercury         [check].................  ........................  ........................
 exposure via maternal fish
 consumption.
Changes in health hazards from      ........................  ........................  [check]
 exposure to pollutants in waters
 used recreationally (e.g.,
 swimming).
----------------------------------------------------------------------------------------------------------------
            Ecological Conditions and Effects on Recreational Use from Surface Water Quality Changes
----------------------------------------------------------------------------------------------------------------
Benefits from changes in surface    [check].................  ........................  ........................
 water quality, including: Aquatic
 and wildlife habitat; water-based
 recreation, including fishing,
 swimming, boating, and nearwater
 activities; aesthetic benefits,
 such as enhancement of adjoining
 site amenities (e.g., residing,
 working, traveling, and owning
 property near the water; \a\ and
 non-use value (existence, option,
 and bequest value from improved
 ecosystem health) \a\.
Benefits from protection of         ........................  [check].................  ........................
 threatened and endangered
 species.
Changes in sediment contamination.  ........................  ........................  [check]
----------------------------------------------------------------------------------------------------------------
                                        Market and Productivity Benefits
----------------------------------------------------------------------------------------------------------------
Changes in impoundment failures.    ........................  ........................  [check]
Changes in water treatment costs    ........................  ........................  [check]
 for municipal drinking water,
 irrigation water, and industrial
 process.
Changes in commercial fisheries     ........................  ........................  [check]
 yields.
Changes in tourism and              ........................  ........................  [check]
 participation in water-based
 recreation.
Changes in property values from     ........................  ........................  [check]
 water quality changes.
Changes in ability to market coal   ........................  ........................  [check]
 combustion byproducts.
Changes in maintenance dredging of  [check].................  ........................  ........................
 navigational waterways and
 reservoirs due to changes in
 sediment discharges.
----------------------------------------------------------------------------------------------------------------
                                               Air-Related Effects
----------------------------------------------------------------------------------------------------------------
Human health benefits from changes  ........................  [check].................  ........................
 in morbidity and mortality from
 exposure to NOX, SO2 and
 particulate matter (PM2.5).
Avoided climate change impacts      [check].................  ........................  ........................
 from CO2 emissions.
----------------------------------------------------------------------------------------------------------------
                                           Changes in Water Withdrawal
----------------------------------------------------------------------------------------------------------------
Changes in the availability of      [check].................  ........................  ........................
 groundwater resources.
Changes in impingement and          ........................  ........................  [check]
 entrainment of aquatic organisms.

Changes in susceptibility to        ........................  ........................  [check]
 drought.
----------------------------------------------------------------------------------------------------------------
\a\ These values are implicit in the total willingness-to-pay (WTP) for water quality improvements.

    The following section summarizes the EPA's analysis of the benefit
categories that the Agency was able to quantify and/or monetize
(identified in the second and third columns of Table XII-1,
respectively). Benefits are a function of not only the changes in
pollutant loadings under the various options, but also the timing of
those options. For example, although loadings increase more under
Option 1, treatment technologies are in place sooner, resulting in
fewer forgone lead, mercury, and arsenic-related human health benefits
under Option 1 than under more stringent options that may be installed
in the future. The regulatory options would also affect additional
benefit categories that the Agency was not able to monetize. The BCA
Report further describes some of these additional nonmonetized
benefits.

B. Quantification and Monetization of Benefits

1. Changes in Human Health Benefits From Changes in Surface Water
Quality
    Changes in pollutant discharges from steam electric facilities
affect human health benefits in multiple ways. Exposure to pollutants
in steam electric power facility discharges via consumption of fish
from affected waters can cause a wide variety of adverse health
effects, including cancer, kidney damage, nervous system damage,
fatigue, irritability, liver damage, circulatory damage, vomiting,
diarrhea, brain damage, IQ loss, and many others. Exposure to drinking
water containing brominated disinfection by-products could cause
adverse health effects such as cancer and reproductive and fetal
development issues. Because the regulatory options in this proposal
would change discharges of steam electric pollutants into waterbodies
that receive or are downstream from these discharges, they may alter
incidence of associated illnesses, even if by small amounts. These
analyses, which are detailed in Chapters 4 and 5 of the BCA, find that
the incremental changes in exposure between the baseline and regulatory
options are minimal compared to the absolute changes for those same
pollutants evaluated in the 2015 rule.
    Due to data limitations and uncertainties, the EPA is able to
monetize only a subset of the changes in health benefits associated
with changes in pollutant discharges from steam electric facilities
resulting from the regulatory options in this proposal as compared to
the baseline. The EPA monetized these changes in human health effects
by estimating the change in the expected number of individuals
experiencing adverse human health effects in the populations exposed to
steam electric discharges and/or altered exposure levels for the
regulatory options relative to the baseline, and valuing these changes
using different monetization methods for different benefit endpoints.
    The EPA estimated changes in health risks from the consumption of
contaminated fish from waterbodies within 50 miles of households. The
EPA used Census Block population data and state-specific average
fishing rates to estimate the exposed population. The EPA used cohort-
specific fish consumption rates and waterbody-specific fish tissue
concentration estimates to calculate potential exposure to steam
electric pollutants. Cohorts were defined by age, sex, race/ethnicity,
and fishing mode (recreational or subsistence). The EPA used these data
to quantify and monetize changes in the following five categories of
human health effects, which are further detailed in the BCA Report:
     Changes in IQ Loss in Children Aged Zero to Seven from
Lead Exposure via Fish Consumption.
     Changes in Need for Specialized Education for Children
from Lead Exposure via Fish Consumption.
     Changes in In Utero Mercury Exposure via Maternal Fish
Consumption and Associated IQ Loss.
     Changes in Incidence of Cancer from Arsenic Exposure via
Fish Consumption.
    Table XII-2 summarizes the monetary value of changes in all
estimated health outcomes associated with consumption of contaminated
fish tissue for the ELG options compared to the baseline. Chapter 5 of
the BCA provides additional detail on the methodology. The EPA solicits
comment on the assumptions and uncertainties included in this analysis.

  Table XII-2--Estimated Total Monetary Values of Changes in Human Health Outcomes for ELG Options (Millions of
                                          2018$) Compared to Baseline a
----------------------------------------------------------------------------------------------------------------
                                                                      Reduced
                                                   Reduced lead       mercury     Reduced cancer
        Discount rate (%)             Option       exposure for    exposure for     cases from         Total
                                                   children \b\      children         arsenic
----------------------------------------------------------------------------------------------------------------
3...............................               1           $0.00          -$0.31           $0.00          -$0.31
                                               2           -0.01           -2.84            0.00           -2.85
                                               3            0.00           -2.85            0.00           -2.85
                                               4            0.00           -1.49            0.00           -1.49
7...............................               1            0.00           -0.06            0.00           -0.06
                                               2            0.00           -0.57            0.00          -0.575
                                               3            0.00           -0.58            0.00           -0.58
                                               4            0.00           -0.30            0.00           -0.30
----------------------------------------------------------------------------------------------------------------
\a\ Negative values represent forgone benefits.
\b\ ``$0.00'' indicates that monetary values are greater than -$0.01 million but less than $0.00 million.
  Benefits to children from exposure to lead range from -$9.1 to $0.7 thousands per year, using a 3 percent
  discount rate, and from -$2.1 to $0.2 thousands, using a 7 percent discount rate.

    The EPA also estimated changes in bladder cancer incidence from the
use and consumption of drinking water contaminated with total
trihalomethanes (TTHMs) derived from changes in pollutant loadings of
bromide associated with the four regulatory options in today's proposal
relative to the baseline. This qualitative relationship between bladder
cancer and bromide demonstrates the relative size of the benefit to
other benefits associated with this proposal. Should this analysis be
used to justify an economically significant rulemaking, the EPA intends
to peer review the analysis consistent with OMB's Information Quality
Bulletin for Peer Review. That review would include robust examination
of the strengths and limitations of the methods and an exploration of
the sensitivity of the results to the assumptions made. If the analysis
is designated a highly influential scientific assessment (HISA), one
way the EPA may seek such a review is via the EPA's Science Advisory
Board (SAB), which is particularly well suited to provide a peer review
of HISAs. The EPA's SAB is a statutorily established committee with a
broad mandate to provide advice and recommendations to the Agency on
scientific and technical matters.
    The EPA estimated changes in cancer risks within populations served
by drinking water treatment facilities with intakes on surface waters
influenced by bromide discharges from steam electric facilities. The
EPA used Safe Drinking Water Information System (SDWIS) and US Census
data to estimate the exposed population. The EPA used estimates of
changes in waterbody-specific bromide concentrations and estimates of
drinking water treatment facility-specific TTHM concentrations to
calculate potential changes in exposure to TTHM and associated adverse
health outcomes.
    The TTHM MCL is set higher than the health-based trihalomethane
Maximum Contaminant Level Goals (MCLGs) in order to balance protection
from human health risks from DBP exposure with the need for adequate
disinfection to control human health risks from microbial pathogens.
Actions that reduce TTHM levels below the MCL can therefore further
reduce human health risk. The EPA's analysis quantifies the human
health effects associated with incremental changes between the MCL and
the MCLG. Recent TTHM compliance monitoring data indicate that the
drinking water treatment facilities contributing most significantly to
the total estimated benefits for the regulatory options have TTHM
levels below the MCL but in excess of the MCLGs for trihalomethanes.
    Table XII-3 summarizes the estimated monetary value of estimated
changes in bromide-related human health outcomes from modeled surface
water quality improvements under Options 2, 3, and 4 or degradation
under Option 1. As described in Chapter 4 of the BCA Report,
approximately 90 percent of these benefits derive from a small number
of steam electric facilities (6 facilities under Option 2, 7 facilities
under Option 3, and 17 facilities under Option 4). Bromide reduction
benefits under Options 2 and 3 derive from estimated facility
participation in the VIP.
    The formation of TTHM in a particular water treatment system is a
function of several site-specific factors, including chlorine, bromine,
organic carbon, temperature, pH and the system residence time. The EPA
did not collect site-specific information on these factors at each
potentially affected drinking water treatment facility. Instead, the
EPA conducted a site-based analysis which only addresses the estimated
site-specific changes in bromides. To account for the changes in TTHM,
and subsequently bladder cancer incidence, using only the estimated
site-specific changes in bromides, the EPA used the national
relationship from Regli et al (2015).\93\ Using this relationship the
analysis held all of the other site-specific factors constant at the
measured values at the approximately 200 drinking water treatment
facilities in that study. Thus, while the national changes in TTHM and
bladder cancer incidence given estimated changes in bromide are the
EPA's best estimate on a nationwide basis, the EPA cautions that for
any specific drinking water treatment facility the estimates could be
over- or underestimated. The EPA solicits comment on the extent to
which uncertainty surrounding site-specific estimated benefits
associated with bromides reductions impact the national estimates
presented in this analysis, as well as data that would assist the EPA
in evaluating this uncertainty. Additional details and uncertainties of
this analysis are provided in Chapter 4 of the BCA Report.
---------------------------------------------------------------------------

    \93\ Regli, S., Chen, J., Messner, M., Elovitz, M.S.,
Letkiewicz, F.J., Pegram, R.A., Pepping, T.J., Richardson, S.D.,
Wright, J.M., 2015. Estimating potential increased bladder cancer
risk due to increased bromide concentrations in sources of
disinfected drinking waters. Environmental Science & Technology,
49(22), 13094-13102.

    Table XII-3--Estimated Human Health Benefits of Changing Bromide
          Discharges Under the ELG Options Compared to Baseline
        [Million of 2018$, three and seven percent discount rate]
------------------------------------------------------------------------
                                              Annualized human health
                                              benefits over 27 years
                                          (millions of 2018$, discounted
            Regulatory option                      to 2020) \a\
                                         -------------------------------
                                            3% Discount     7% Discount
                                               rate            rate
------------------------------------------------------------------------
Option 1................................          -$0.36          -$0.23
Option 2................................           37.61           24.21
Option 3................................           42.57           27.48
Option 4................................           84.32           54.30
------------------------------------------------------------------------
\a\ The analysis accounts for the persisting health effects (up until
  2121) from changes in TTHM exposure during the period of analysis
  (2021-2047).

2. Changes in Surface Water Quality
    The EPA evaluated whether the regulatory options in today's
proposal would alter aquatic habitats and human welfare by changing
concentrations of harmful pollutants such as arsenic, cadmium,
chromium, copper, lead, mercury, nickel, selenium, zinc, nitrogen,
phosphorus, and suspended sediment relative to the baseline. As a
result, the usability of some of the waters for recreation relative to
baseline discharge conditions could change under each option, thereby
affecting recreational users. Changes in pollutant loadings can also
change the attractiveness of waters usable for recreation by making
recreational trips more or less enjoyable. The regulatory options may
also change nonuse values stemming from bequest, altruism, and
existence motivations. Individuals may value water quality maintenance,
ecosystem protection, and healthy species populations independent of
any use of those attributes.
    The EPA uses a water quality index (WQI) to translate water quality
measurements, gathered for multiple parameters that are indicative of
various aspects of water quality, into a single numerical indicator
that reflects achievement of quality consistent with the suitability
for certain uses. The WQI includes seven parameters: Dissolved oxygen,
biochemical oxygen demand, fecal coliform, total nitrogen, total
phosphorus, TSS, and one aggregate subindex for toxics. The EPA modeled
changes in four of these parameters, and held the remaining parameters
(dissolved oxygen, biochemical oxygen demand, and fecal coliform)
constant for the purposes of this analysis. Table XII-4 summarizes
water quality change ranges relative to the baseline under the four
regulatory options. Under Options 1 through 3, 78 to 84 percent of
potentially affected reaches have a negative change in the WQI. Another
16 to 22 percent of reaches show no change under these options. Under
Option 4, 61 percent of reaches would experience a negative change in
the WQI, and another 12 percent of reaches show no change.

      Table XII-4--Estimated Ranges of Water Quality Changes Under Regulatory Options Compared to Baseline
----------------------------------------------------------------------------------------------------------------
                                                                                [Delta]WQI
                Regulatory option                     Minimum         Maximum         Median       interquartile
                                                  [Delta]WQI \a\    [Delta]WQI      [Delta]WQI         range
----------------------------------------------------------------------------------------------------------------
Option 1........................................           -5.29            0.00        -0.00102         0.01000
Option 2........................................           -2.95            1.30        -0.00047         0.00168
Option 3........................................           -2.95            1.30        -0.00023         0.00078
Option 4........................................           -2.62            1.31        -0.00002         0.00125
----------------------------------------------------------------------------------------------------------------
\a\ Negative changes in WQI values indicate degrading water quality.

    The EPA estimated the change in monetized benefit values using the
same meta-regressions of surface water valuation studies used in the
benefit analysis for the 2015 rule. The meta-regressions quantify
average household WTP for incremental improvements in surface water
quality. This WTP is the maximum amount of money a person is willing to
give up to obtain an improvement in water quality. Chapter 6 of the BCA
provides additional detail on the valuation methodology. Overall,
Option 1 results in water quality degradation, which is reflected in
negative annual household WTP values ranging from -$0.11 to -$0.62.
Under Options 2, 3, and 4, the net water quality improvements
(accounting for all increases and decreases of pollutant loadings)
result in positive net benefits to households affected by water quality
changes from the regulatory options proposed. The estimated annual
household WTP for water quality changes ranges from $0.10 to $0.56 for
Option 2, $0.16 to $0.87 for Option 3, and $0.19 to $1.04 for Option 4.
    Table XII-5 presents annualized total WTP values for water quality
changes associated with modified metal (arsenic, cadmium, chromium,
copper, lead, mercury, zinc, and nickel), non-metal (selenium),
nutrient (phosphorus and nitrogen), and sediment pollutant discharges
to the approximately 10,393 reach miles affected by the regulatory
options in this proposal. An estimated 85 million households reside in
Census block groups within 100 miles of affected reaches. The central
tendency estimate of the total annualized benefits of water quality
changes for Option 2 range from $14.3 million (7 percent discount rate)
to $16.7 million (3 percent discount rate).

                    Table XII-5--Estimated Total Willingness-To-Pay for Water Quality Changes (Millions 2018$) Compared to Baseline a
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Number of              3% Discount rate                       7% Discount rate
                                                                 affected  -----------------------------------------------------------------------------
                      Regulatory option                         households
                                                                (millions)      Low        Central        High         Low        Central        High
--------------------------------------------------------------------------------------------------------------------------------------------------------
Option 1.....................................................         85.2       -$10.0       -$12.5       -$55.5        -$8.6       -$10.9       -$48.1
Option 2.....................................................         86.9         11.8         16.7         65.6         10.1         14.3         56.1
Option 3.....................................................         84.6         16.3         22.5         90.7         14.0         19.4         77.8
Option 4.....................................................         86.5         19.8         27.3        110.2         17.0         23.6         94.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Negative values represent forgone benefits and positive values represent realized benefits.

3. Effects on Threatened and Endangered Species
    To assess the potential for impacts on T&E species (both aquatic
and terrestrial) relative to the 2015 baseline, the EPA analyzed the
overlap between waters expected to change their wildlife WQC exceedance
status under a particular option and the known critical habitat
locations of high-vulnerability T&E species. The EPA examined the life
history traits of potentially affected T&E species and categorized them
by potential for population impacts due to surface water quality
changes. Chapter 7

of the BCA Report provides additional detail on the methodology. The
EPA determined that there are 24 species whose known critical habitat
overlaps with surface waters that may be affected by the proposed
options when compared to the baseline, including three fish species,
two amphibian and reptile species, one bird species, 17 clam and mussel
species, and one snail species. Six of these species have known
critical habitat overlapping surface waters that are expected to see
reduced exceedances of NRWQC under proposed Options 2, 3, or 4, while
23 species (including 5 species that may see reduced exceedances of
NRWQC under proposed Options 2, 3, or 4, depending on habitat location)
have known critical habitat overlapping surface waters that may see
increased exceedances of NRWQC under one or more of the proposed
options. Under Option 2, there are two species whose known critical
habitat overlaps with surface waters that may see reduced exceedances
of NRWQC, and 12 species whose known critical habitat overlaps with
surface waters that may see increased exceedances of NRWQC. Option 1 is
expected to result in increased exceedances of NRWQC across all habitat
locations. Principal sources of uncertainty include the specifics of
how these proposed options will impact threatened and endangered
species, exact spatial distribution of the species, and additional
species of concern not considered.
4. Changes in Benefits From Marketing of Coal Combustion Residuals
    The proposed rule options could affect the ability of steam
electric facilities to market coal combustion byproducts for beneficial
use by converting from wet to dry handling of BA. In particular, the
EPA evaluated the potential effects from changes in marketability of BA
as a substitute for sand and gravel in fill applications. Among the
regulatory options considered for this proposal, EPA estimates that
only Option 2 would affect the quantity of BA handled wet when compared
to the baseline, and for that option the estimated increase in BA
handled wet is small (total of 310,671 tons per year at 20 facilities).
Given these small changes and the uncertainty associated with
projecting facility-specific changes in marketed ash, the EPA chose not
to monetize this benefit category in the analysis of the proposed
regulatory options. See Chapter 2 in the BCA report for additional
details.
5. Changes in Dredging Costs
    The proposed regulatory options would affect discharge loadings of
various categories of pollutants, including TSS, thereby changing the
rate of sediment deposition to affected waterbodies, including
navigable waterways and reservoirs that require dredging for
maintenance.
    Navigable waterways, including rivers, lakes, bays, shipping
channels and harbors, are an integral part of the United States
transportation network. They are prone to reduced functionality due to
sediment build-up, which can reduce the navigable depth and width of
the waterway. In many cases, costly periodic dredging is necessary to
keep them passable. Reservoirs serve many functions, including storage
of drinking and irrigation water supplies, flood control, hydropower
supply, and recreation. Streams can carry sediment into reservoirs,
where it can settle and cause buildup of silt layers over time.
Sedimentation reduces reservoir capacity and the useful life of
reservoirs unless measures such as dredging are taken to reclaim
capacity. Chapter 10 of the BCA provides additional detail on the
methodology.
    The EPA expects that Option 4 would provide cost savings ranging
from $0.48 million (7 percent discount rate) to $0.72 million (3
percent discount rate) by reducing required dredging maintenance for
both navigable waterways and reservoirs. Estimated increases in
sediment loadings under Options 1, 2, and 3 would result in cost
increases. Cost increases range from $0.05 million to $0.09 million for
Option 1, $0.12 million to $0.21 million for Option 2, and $0.04
million to $0.07 million for Option 3.
6. Changes in Air-Related Effects
    The EPA expects the proposed options to affect air pollution
through three main mechanisms: (1) Changes in auxiliary electricity use
by steam electric facilities to operate wastewater treatment, ash
handling, and other systems that the EPA predicts facilities would use
under each proposed option; (2) changes in transportation-related air
emissions due to changes in trucking of CCR waste to landfills; and (3)
change in the profile of electricity generation due to the relatively
higher or lower costs to generate electricity at steam electric
facilities incurring compliance costs under the proposed options.
    Changes in the electricity generation profile can increase or
decrease air pollutant emissions because emission factors vary for
different types of electric boilers. For this analysis, the changes in
air emissions are based on the change in dispatch of generation units
as projected by IPM V6 given the overlaying of costs for complying with
the proposed options onto steam electric boilers' production costs. As
discussed in Section VIII of this preamble, the IPM V6 analysis
accounts for the effects of other regulations on the electric power
sector.
    The EPA evaluated potential effects resulting from net changes in
air emissions of three pollutants: NOX, SO2, and
CO2. NOX and SOX are precursors to
fine particles sized 2.5 microns and smaller (PM2.5), this
air pollutant causes a variety of adverse health effects including
premature death, non-fatal heart attacks, hospital admissions,
emergency department visits, upper and lower respiratory symptoms,
acute bronchitis, aggravated asthma, lost work days, and acute
respiratory symptoms. CO2 is a key greenhouse gas linked to
a wide range of domestic effects.\94\
---------------------------------------------------------------------------

    \94\ U.S. EPA. Integrated Science Assessment (ISA) for
Particulate Matter (Final Report, Dec 2009). U.S. Environmental
Protection Agency, Washington, DC, EPA/600/R-08/139F, 2009.
---------------------------------------------------------------------------

    The EPA used domestic social cost of carbon estimates to value
changes in CO2 emissions (SC-CO2). The Agency
quantified changes in emissions of PM2.5 precursors,
NOX, and SO2. To map those emission changes to
air quality changes across the country, air quality modeling is needed.
Prior to this proposal, the EPA's modeling capacity was fully allocated
to supporting other regulatory and policy efforts.
    Table XII-6 shows the changes in emissions of NOX,
SO2, and CO2 based on the estimated increases in
electricity generation (see Table VIII-3) for options 2 and 4 (the two
regulatory options that the EPA analyzed for these increased emission
effects). Table XII-7 shows the total annualized monetary values
associated with changes in emissions of CO2 for options 2
and 4. All total monetary values are negative, indicating that the
proposed rule results in net forgone CO2-related benefits
when compared to the baseline. While not monetized, additional forgone
benefits associated with PM2.5 would also occur. The
majority of the forgone benefits are due to changes in the profile of
electricity generation. Smaller shares of the changes in total benefits
are attributable to changes in energy use to operate wastewater
treatment systems. Benefits from changes in trucking emissions are
negligible. The EPA did not analyze benefits from changes in air
emissions for Options 1 and 3 but instead extrapolated values by
scaling air-related benefits under Option 2 in

proportion to the total social costs of each option. Chapter 8 of the
BCA Report provides additional details on the analysis of air-related
benefits.

                     Table XII-6--Estimated Changes in Air Emissions Compared to Baseline a
----------------------------------------------------------------------------------------------------------------
                                                                    CO2 (metric
           Regulatory option              Category of emissions     tons/year)      NOX (tons/      SO2 (tons/
                                                                                year)           year)
----------------------------------------------------------------------------------------------------------------
Option 2..............................  Electricity generation b       5,656,000           4,650           4,930
                                         c.
                                        Trucking................            -490               0               0
                                        Energy use b c..........         -44,080             -32             -54
                                                                 -----------------------------------------------
                                           Total \d\............       5,611,000           4,620           4,870
rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
Option 4..............................  Electricity generation b       1,244,000           1,900           1,020
                                         e.
                                        Trucking................           1,440               1               0
                                        Energy use b e..........          59,320              31              20
                                                                 -----------------------------------------------
                                           Total \d\............       1,305,000           1,940           1,040
----------------------------------------------------------------------------------------------------------------
\a\ Negative values represent emission reductions.
\b\ Estimated changes in emissions shown for 2028-2032 based on the estimated increase in electricity generation
  of 0.3% for Option 2 and 0.1% for Option 4.
\c\ Option 2 estimates are based on the IPM sensitivity analysis scenario that includes the ACE rule in the
  baseline (IPM-ACE).
\d\ Values may not sum to the total due to independent rounding.
\e\ Option 4 estimates are based on IPM analysis scenario that does not include the ACE rule in the baseline.

   Table XII-7--Estimated Annualized Benefits From Changes in CO2 Air Emissions (Millions; 2018$) Compared to
                                                   Baseline a
----------------------------------------------------------------------------------------------------------------
                                                                                3% Discount     7% Discount
               Regulatory option                      Category of emissions            rate            rate
----------------------------------------------------------------------------------------------------------------
Option 2......................................  Electricity generation \b\......          -$32.0           -$5.2
                                                Trucking........................             0.0             0.0
                                                Energy use \b\..................             0.4             0.1
                                                                                -------------------------------
                                                   Total \c\....................           -31.6            -5.2
                                                                                -------------------------------
Option 4......................................  Electricity generation \d\......            -4.3            -0.8
                                                Trucking........................             0.0             0.0
                                                Energy use \d\..................            -0.5             0.0
                                                                                -------------------------------
                                                   Total \c\....................            -4.8            -0.9
----------------------------------------------------------------------------------------------------------------
\a\ Negative values represent forgone benefits.
\b\ Option 2 estimates are based on the IPM sensitivity analysis scenario that includes the ACE rule in the
  baseline (IPM-ACE).
\c\ Values may not sum to the total due to independent rounding.
\d\ Option 4 estimates are based on IPM analysis scenario that does not include the ACE rule in the baseline.

7. Benefits From Changes in Water Withdrawals
    Steam electric facilities use water for handling BA and operating
wet FGD scrubbers. By reducing water used in sluicing operations or
prompting the recycling of water in FGD wastewater treatment systems,
Option 4 is expected to reduce water withdrawals from surface waters,
whereas proposed Options 1, 2, and 3 are expected to increase water
withdrawals from surface waterbodies. Option 2 is also expected to
increase water withdrawal from aquifers. Using the same methodology
used for the 2015 rule, the EPA estimated the monetary value of
increased ground water withdrawals based on increased costs of ground
water supply. For each relevant facility, the EPA multiplied the
increase in ground water withdrawal (in gallons per year) by water
costs of about $1,192 per acre-foot. Chapter 9 of the BCA Report
provides the details of this analysis. The EPA estimates the changes in
annualized benefits of increased ground water withdrawals are less than
$0.2 million annually. Due to data limitations, the EPA was not able to
estimate the monetary value of changes in surface water withdrawals.
Chapter 9 of the BCA Report and Section 7 of the Supplemental TDD
provide additional details on the estimated changes in surface water
withdrawals.

C. Total Monetized Benefits

    Using the analysis approach described above, the EPA estimated the
total monetary value of annual benefits of the proposed rule for all
monetized categories. Table XII-8 and Table XII-9 summarize the total
annualized monetary value of social welfare effects using 3 percent and
7 percent discount rates, respectively. The total monetary value of
benefits under Option 2 range from $14.8 million to $68.5 million using
a 3 percent discount rate and from $28.4 million to $74.4 million using
a 7 percent discount rate.

                                             Table XII-8--Summary of Total Annualized Benefits at 3 Percent
                                                                   [Millions; 2018$] a
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Option 1                      Option 2                   Option 3                   Option 4
           Benefit category            -----------------------------------------------------------------------------------------------------------------
                                           Low        Mid        High      Low      Mid      High     Low      Mid      High     Low      Mid      High
--------------------------------------------------------------------------------------------------------------------------------------------------------
Human Health \d\......................               -$0.7
                                                     $34.8
                                                     $39.7
                                                     $82.8
    Changes in IQ losses in children
     from exposure to lead \b\........                <0.0
                                                      <0.0
                                                      <0.0
                                                      <0.0
    Changes in IQ losses in children
     from exposure to mercury.........                -0.3
                                                     -2.84
                                                     -2.85
                                                     -1.49
    Reduced cancer risk from DBPs in
     drinking water...................                -0.4
                                                      37.6
                                                      42.6
                                                      84.3
                                       -----------------------------------------------------------------------------------------------------------------
Ecological Conditions and Recreational     -$10.0     -$12.5     -$55.5    $11.8    $16.7    $65.6    $16.3    $22.5    $90.7    $19.8    $27.3   $110.2
 Uses Changes.........................
    Use and nonuse values for water         -10.0      -12.5      -55.5     11.8     16.7     65.6     16.3     22.5     90.7     19.8     27.3    110.2
     quality changes..................
Market and Productivity \d\...........       -0.1       -0.1       -0.1     -0.2     -0.2     -0.2     -0.1     -0.1     -0.1      0.6      0.6      0.7
    Changes in dredging costs.........       -0.1       -0.1       -0.1     -0.1     -0.2     -0.2     -0.1     -0.1     -0.1      0.6      0.6      0.7
                                       -----------------------------------------------------------------------------------------------------------------
    Reduced water withdrawals \b\.....                $0.0
                                                     <$0.0
                                                      $0.0
                                                      $0.0
Air-related effects...................               -30.3
                                                     -31.6
                                                     -20.9
                                                      -4.8
    Changes in CO2 air emissions \c\..               -30.3
                                                     -31.6
                                                     -20.9
                                                      -4.8
                                       -----------------------------------------------------------------------------------------------------------------
        Total \d\.....................     -$41.0     -$43.6     -$86.6    $14.8    $19.6    $68.5    $35.1    $41.3   $109.4    $98.4   $105.9   $188.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Negative values represent forgone benefits and positive values represent realized benefits.
\b\ ``<$0.0'' indicates that monetary values are greater than -$0.1 million but less than $0.00 million.
\c\ The EPA estimated the air-related benefits for Option 2 using the IPM sensitivity analysis scenario that includes the ACE rule in the baseline (IPM-
  ACE). EPA extrapolated estimates for Options 1 and 3 air-related benefits from the estimate for Option 2 that is based on IPM-ACE outputs. The values
  for Option 4 air-related benefits were estimated using the IPM analysis scenario that does not include the ACE rule in the baseline.
\d\ Values for individual benefit categories may not sum to the total due to independent rounding.

                                             Table XII-9--Summary of Total Annualized Benefits at 7 Percent
                                                                   [Millions; 2018$] a
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Option 1                      Option 2                   Option 3                   Option 4
           Benefit category            -----------------------------------------------------------------------------------------------------------------
                                           Low        Mid        High      Low      Mid      High     Low      Mid      High     Low      Mid      High
--------------------------------------------------------------------------------------------------------------------------------------------------------
Human Health \d\......................               -$0.3
                                                     $23.6
                                                     $26.9
                                                     $54.0
    Changes in IQ losses in children
     from exposure to lead \b\........                <0.0
                                                      <0.0
                                                      <0.0
                                                      <0.0
    Changes in IQ losses in children
     from exposure to mercury.........                -0.1
                                                      -0.6
                                                      -0.6
                                                      -0.3
    Reduced cancer risk from DBPs in
     drinking water...................                -0.2
                                                      24.2
                                                      27.5
                                                      54.3
                                       -----------------------------------------------------------------------------------------------------------------
Ecological Conditions and Recreational      -$8.6     -$10.9     -$48.1    $10.1    $14.3    $56.1    $14.0    $19.4    $77.8    $17.0    $23.6    $94.6
 Uses Changes.........................
    Use and nonuse values for water          -8.6      -10.9      -48.1     10.1     14.3     56.1     14.0     19.4     77.8     17.0     23.6     94.6
     quality changes..................
Market and Productivity \d\...........       -0.1       -0.1       -0.1     -0.1     -0.2     -0.2      0.0     -0.1     -0.1      0.5      0.5      0.7
    Changes in dredging costs.........       -0.1       -0.1       -0.1     -0.1     -0.1     -0.2      0.0     -0.1     -0.1      0.5      0.5      0.7
                                       -----------------------------------------------------------------------------------------------------------------
    Reduced water withdrawals \b\.....                $0.0
                                                     <$0.0
                                                      $0.0
                                                      $0.0
Air-related Effects...................                -4.8
                                                      -5.2
                                                      -3.7
                                                      -0.9
    Changes in CO2 air emissions \c\..                -4.8
                                                      -5.2
                                                      -3.7
                                                      -0.9
                                       -----------------------------------------------------------------------------------------------------------------
        Total \d\.....................     -$13.7     -$16.0     -$53.3    $28.4    $32.6    $74.4    $37.1    $42.5   $100.9    $70.6    $77.2   $148.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Negative values represent forgone benefits and positive values represent realized benefits.
\b\ ``<$0.0'' indicates that monetary values are greater than -$0.1 million but less than $0.00 million.
\c\ The EPA estimated the air-related benefits for Option 2 using the IPM sensitivity analysis scenario that includes the ACE rule in the baseline (IPM-
  ACE). EPA extrapolated estimates for Options 1 and 3 air-related benefits from the estimate for Option 2 that is based on IPM-ACE outputs. The values
  for Option 4 air-related benefits were estimated using the IPM analysis scenario that does not include the ACE rule in the baseline.
\d\ Values for individual benefit categories may not sum to the total due to independent rounding.

D. Unmonetized Benefits

    The monetary value of the proposed rule's effects on social welfare
does not account for all effects of the proposed options because, as
described above, the EPA is unable to monetize some categories.
Examples of effects not reflected in these monetary estimates include
health and other effects from changes in NOX and
SO2 air emissions; changes in certain non-cancer health
risks (e.g., effects of cadmium on kidney functions and bone density);
impacts of pollutant load changes on threatened and endangered species
habitat; and ash marketing changes. The BCA Report discusses changes in
these effects qualitatively, indicating their potential magnitude where
possible.

XIII. Development of Effluent Limitations and Standards

A. FGD Wastewater

    The proposed rule contains new numeric effluent limitations and
pretreatment standards that apply to discharges of FGD wastewater at
existing sources.\95\ The EPA is

proposing several sets of effluent limitations and pretreatment
standards for FGD wastewater discharges; the specific set of
limitations that would apply to any particular facility are determined
by which subcategory the facility falls within, or whether it chooses
to participate in the voluntary incentives program. The EPA developed
the numeric effluent limitations and pretreatment standards in this
proposed rule using long-term average effluent values and variability
factors that account for variations in performance at well-operated
facilities that employ the technologies that constitute the bases for
control. The EPA's methodology for derivation of limitations in ELGs is
longstanding and has been upheld in court. See, e.g., Chem. Mfrs. Ass'n
v. EPA, 870 F.2d 177 (5th Cir. 1989); Nat'l Wildlife Fed'n v. EPA, 286
F.3d 554 (D.C. Cir. 2002). The EPA establishes the final effluent
limitations and standards as ``daily maximums'' and ``maximums for
monthly averages.'' Definitions provided in 40 CFR 122.2 state that the
daily maximum limitation is the ``highest allowable `daily discharge'
'' and the maximum for monthly average limitation is the ``highest
allowable average of `daily discharges' over a calendar month,
calculated as the sum of all `daily discharges' measured during a
calendar month divided by the number of `daily discharges' measured
during that month.'' Daily discharges are defined to be the ``
`discharge of a pollutant' measured during a calendar day or any 24-
hour period that reasonably represents the calendar day for purposes of
sampling.''
---------------------------------------------------------------------------

    \95\ Effluent limitations for boilers with nameplate capacity of
50 MW or smaller and for boilers that will retire by December 31,
2028, are not discussed in this section. The proposed limitations
for these generating units are based on the previously established
BPT limitations on TSS.
---------------------------------------------------------------------------

1. Overview of the Limitations and Standards
    The EPA's objective in establishing daily maximum limitations is to
restrict the discharges on a daily basis at a level that is achievable
for a facility that designs and operates its treatment to achieve the
long-term average performance that the EPA's statistical analyses show
the BAT/PSES technology can attain (i.e., the mean of the underlying
statistical distribution of daily effluent values). The EPA recognizes
that variability around the long-term average occurs during normal
operations. This variability means that facilities occasionally may
discharge at a level that is higher than the long-term average, and at
other times will discharge at a level that is lower than the long-term
average. To allow for these possibly higher daily discharges and
provide an upper bound for the allowable concentration of pollutants
that may be discharged, while still targeting achievement of the long-
term average, the EPA has established the daily maximum limitation. A
facility consistently discharging at a level near the daily maximum
limitation would be symptomatic of a facility that is not operating its
treatment to achieve the long-term average. Targeting treatment to
achieve the daily limitation, rather than the long-term average, is not
consistent with the capability of the BAT/PSES technology basis and may
result in values that periodically exceed the limitations due to
routine variability in treated effluent.
    The EPA's objective in establishing monthly average limitations is
to provide an additional restriction to help ensure that facilities
target their average discharges to achieve the long-term average. The
monthly average limitation requires dischargers to provide ongoing
control, on a monthly basis, that supplements controls imposed by the
daily maximum limitation. In order to meet the monthly average
limitation, a facility must counterbalance a value near the daily
maximum limitation with one or more values well below the daily maximum
limitation.
2. Criteria Used To Select Data
    In developing effluent limitations guidelines and standards for any
industry, the EPA qualitatively reviews all the data before selecting
data that represents proper operation of the technology that forms the
basis for the limitations. The EPA typically uses four criteria to
assess the data. The first criterion requires that the facilities have
the model treatment technology identified as a candidate basis for
effluent limitations (e.g., chemical precipitation with LRTR) and
demonstrate consistently diligent and optimal operation. Application of
this criterion typically eliminates any facility with treatment other
than the model technology. The EPA generally determines whether a
facility meets this criterion based upon site visits, discussions with
facility management, and/or comparison to the characteristics,
operation, and performance of treatment systems at other facilities.
The EPA reviews available information to determine whether data
submitted were representative of normal operating conditions for the
facility and equipment. As a result of this review, the EPA typically
excludes the data in developing the limitations when the facility has
not optimized the performance of its treatment system.
    A second criterion generally requires that the influents and
effluents from the treatment components represent typical wastewater
from the industry, without incompatible wastewater from other sources.
Application of this criterion results in the EPA selecting those
facilities where the commingled wastewaters did not result in
substantial dilution, unequalized slug loads resulting in frequent
upsets and/or overloads, more concentrated wastewaters, or wastewaters
with different types of pollutants than those generated by the
wastestream for which the EPA is proposing effluent limitations and
pretreatment standards.
    A third criterion typically ensures that the pollutants are present
in the influent at sufficient concentrations to evaluate treatment
effectiveness. If a data set for a pollutant shows that the pollutant
was not present at a treatable concentration at sufficient frequency
(e.g., the pollutant was below the level of detection in all influent
samples), the EPA excludes the data for that pollutant at that facility
when calculating the limitations.
    A fourth criterion typically requires that the data are valid and
appropriate for their intended use (e.g., the data must be analyzed
with a sufficiently sensitive method). Also, the EPA does not use data
associated with periods of treatment upsets because these data would
not reflect the performance from well-designed and well-operated
treatment systems. In applying the fourth criterion, the EPA may
evaluate the pollutant concentrations, analytical methods and the
associated quality control/quality assurance data, flow values, mass
loading, facility logs, test reports, and other available information.
As part of this evaluation, the EPA reviews the process or treatment
conditions that may have resulted in extreme values (high and low). As
a consequence of this review, the EPA may exclude data associated with
certain time periods or other data outliers that reflect poor
performance or analytical anomalies by an otherwise well-operated site.
    The fourth criterion also is applied in the EPA's review of data
corresponding to the initial commissioning period for treatment systems
(and startup periods for pilot test equipment). Most industries incur
commissioning periods during the adjustment period associated with
installing new treatment systems. During this acclimation and
optimization process, the effluent concentration values tend to be
highly variable with occasional extreme values (high and low). This
occurs because the treatment system typically requires

some ``tuning'' as the facility staff and equipment and chemical
vendors work to determine the optimum chemical addition locations and
dosages, vessel hydraulic residence times, internal treatment system
recycle flows (e.g., filter backwash frequency, duration and flow rate,
return flows between treatment system components), and other
operational conditions including clarifier sludge wasting protocols. It
may also take time for treatment system operators to gain expertise on
operating the new treatment system, which also contributes to treatment
system variability during the commissioning period. After this initial
adjustment period, the systems should operate at steady state with
relatively low variability around a long-term average over many years.
Because commissioning periods typically reflect one-time operating
conditions unique to the first time the treatment system begins
operation, the EPA generally excludes such data in developing the
limitations.\96\
---------------------------------------------------------------------------

    \96\ Examples of conditions that are typically unique to the
initial commissioning period include operator unfamiliarity or
inexperience with the system and how to optimize its performance;
wastewater flow rates that differ significantly from engineering
design, altering hydraulic residence times, chemical contact times,
and/or clarifier overflow rates, and potentially causing large
changes in planned chemical dosage rates or the need to substitute
alternative chemical additives; equipment malfunctions; fluctuating
wastewater flow rates or other dynamic conditions (i.e., not steady
state operation); and initial purging of contaminants associated
with installation of the treatment system, such as initial leaching
from coatings, adhesives, and susceptible metal components. These
conditions differ from those associated with the restart of an
already-commissioned treatment system, such as may occur from a
treatment system that has undergone either short or extended
duration shutdown.
---------------------------------------------------------------------------

3. Data Used To Calculate Limitations and Standards
    The Supplemental TDD provides a description of the data and
methodology used to develop long-term averages, variability factors,
and limitations and standards for this proposed rule. The effluent
limitations and pretreatment standards for the low utilization
subcategory and high flow subcategory are based on chemical
precipitation. The derivation of the limitations for these
subcategories and the data used are described in Section 13 of the 2015
TDD. The new limitations and pretreatment standards proposed today for
facilities not in those subcategories and for the voluntary incentives
plan were derived from a statistical analysis of effluent data
collected by facilities during extended testing of the LRTR technology
and membrane filtration technology, respectively. The duration of the
test programs at these facilities spanned from approximately one month
for membranes to more than a year for LRTR, enabling the EPA to
evaluate long-term performance of these technologies under conditions
that can contribute to influent variability, including varying power
demand, changes in coal suppliers, and changes in operation of the air
pollution control system. The tests occurred over different seasons of
the year and demonstrate that the technologies operate effectively
under varying climate conditions.
    During the development of these new limitations and pretreatment
standards, the EPA identified certain data that warranted exclusion
because: (1) The samples were analyzed using a method that is not
sensitive enough to reliably quantify the pollutants present (e.g., use
of EPA Method 245.1 to measure the concentration of mercury in effluent
samples); (2) the analytical results were identified as questionable
due to quality control issues associated with the laboratory analysis
or sample collection, or were analytical anomalies; (3) the samples
were collected prior to steady-state operating condition and do not
represent BAT/PSES level of performance; (4) the samples were collected
during a period where influent composition did not reflect the FGD
wastewater (e.g., untreated FGD wastewater was mixed with large volume
of non-FGD wastewater prior to the treatment system); (5) the treatment
system was operating in a manner that does not represent BAT/PSES level
of performance; or (6) the samples were collected from a location that
is not representative of treated effluent.
4. Long-Term Averages and Effluent Limitations and Standards for FGD
Wastewater
    Table XIV-1 presents the proposed effluent limitations and
standards for FGD wastewater. For comparison, the table also presents
the long-term average treatment performance calculated for each
parameter. Due to routine variability in treated effluent, a power
facility that targets discharging its wastewater at a level near the
values of the daily maximum limitation or the monthly average
limitation may periodically experience values exceeding the
limitations. For this reason, the EPA recommends that facilities design
and operate the treatment system to achieve the long-term average for
the model technology. In doing so, a system that is designed and
operated to achieve the BAT/PSES level of control would meet the
limitations.
    The EPA expects that facilities will be able to meet their effluent
limitations or standards at all times. If an exceedance is caused by an
upset condition, the facility would have an affirmative defense to an
enforcement action if the requirements of 40 CFR 122.41(n) are met.
Exceedances caused by a design or operational deficiency, however, are
indications that the facility's performance does not represent the
appropriate level of control. For these proposed limitations and
pretreatment standards, the EPA proposes to determine that such
exceedances can be controlled by diligent process and wastewater
treatment system operational practices, such as regular monitoring of
influent and effluent wastewater characteristics and adjusting dosage
rates for chemical additives to target effluent performance for
regulated pollutants at the long-term average concentration for the
BAT/PSES technology. Additionally, some facilities may need to upgrade
or replace existing treatment systems to ensure that the treatment
system is designed to achieve performance that targets the effluent
concentrations at the long-term average. This is consistent with the
EPA's costing approach and its engineering judgment, developed over
years of evaluating wastewater treatment processes for steam electric
facilities and other industrial sectors. The EPA recognizes that some
dischargers, including those that are operating technologies
representing the technology basis for the proposed rule, may need to
improve their treatment systems, process controls, and/or treatment
system operations in order to consistently meet the proposed effluent
limitations and pretreatment standards. This is consistent with the
CWA, which requires that BAT/PSES discharge limitations and standards
reflect the best available technology economically achievable.
    See Section 8 of the Supplemental TDD for more information about
the calculation of the limitations and pretreatment standards presented
in the tables below.

   Table XIV-1--Long-Term Averages and Effluent Limitations and Pretreatment Standards for FGD Wastewater for
                                          Existing Sources (BAT/PSES) a
----------------------------------------------------------------------------------------------------------------
                                                                                Monthly
              Subcategory                       Pollutant            Long-term    Daily  maximum      average
                                                                      average        limitation     limitation
----------------------------------------------------------------------------------------------------------------
Requirements for all facilities not in  Arsenic ([mu]g/L).......             5.1              18               9
 the VIP or subcategories specified     Mercury (ng/L)..........            13.5              85              31
 below (BAT & PSES).                    Nitrate/nitrite as N (mg/            2.6             4.6             3.2
                                         L).
                                        Selenium ([mu]g/L)......            16.6              76              31
Voluntary Incentives Program for FGD    Arsenic ([mu]g/L).......         \b\ 5.0           \c\ 5           (\d\)
 Wastewater (BAT only).                 Mercury (ng/L)..........             5.1              21               9
                                        Nitrate/nitrite as N (mg/            0.4             1.1             0.6
                                         L).
                                        Selenium ([mu]g/L)......             5.0              21              11
                                        Bromide (mg/L)..........            0.16             0.6             0.3
                                        TDS (mg/L)..............              88             351             156
Low utilization subcategory--AND--High  Arsenic ([mu]g/L).......            5.98              11               8
 flow subcategory (BAT & PSES).         Mercury (ng/L)..........             159             788             356
----------------------------------------------------------------------------------------------------------------
\a\ BAT effluent limitations for boilers with nameplate capacity of 50 MW or smaller, and boilers that will
  retire by December 31, 2028, are based on the previously established BPT limitations on TSS and are not shown
  in this table. The BAT effluent limitations for TSS for these retiring boilers is daily maximum of 100 mg/L;
  monthly average of 30 mg/L.
\b\ Long-term average is the arithmetic mean of the quantitation limitations since all observations were not
  detected.
\c\ Limitation is set equal to the quantitation limit for the data evaluated.
\d\ Monthly average limitation is not established when the daily maximum limitation is based on the quantitation
  limit.

    The EPA notes that while some limitations are higher than
corresponding limits in the 2015 rule, in other cases limitations of
additional pollutants or lower limitations for pollutants regulated in
the 2015 rule have also been calculated. The EPA solicits comment on
the demonstrated ability or inability of existing systems to meet the
limitations in this proposal, the costs associated with modifying
existing systems or with modifying the operation of existing systems to
meet these limits, and whether any existing systems with demonstrated
issues meeting these limits would be best addressed through FDF
variances or through subcategorization. Furthermore, should the EPA
determine subcategorization of facilities with existing FGD treatment
systems is warranted, the EPA solicits comment on what limitations
should apply to those facilities, including whether the 2015 rule
limits would be appropriate for such facilities.

B. BA Transport Water Limitations

1. Maximum 10 Percent 30-Day Rolling Average Purge Rate
    In contrast to the limitations estimated for specific pollutants
above, the EPA is proposing a pollutant discharge allowance in the form
of a maximum percentage purge rate for BA transport water. To develop
this allowance, the EPA first collected data on the discharge needs of
the model treatment technology (high recycle rate systems) to maintain
water chemistry or water balance.\97\ EPRI (2016) presents discharge
data from seven currently operating wet BA transport water systems at
six facilities. These facilities were able to recycle most or all BA
transport water from these seven systems, resulting in discharges of
between zero and two percent of the system volume. The EPA's goal in
establishing the proposed purge rate was to provide an allowance to
address the challenges that would be incorporated in the EPRI (2016)
data, as well as infrequent precipitation and maintenance events, the
EPA also needed a way to account for such infrequent events. While EPRI
(2016) noted that infrequent discharges happened at some facilities, it
did not include such events in its discharge calculations. As a result,
EPA looked to EPRI (2018), which presents hypothetical maximum
discharge volumes and the estimated frequency associated with such
infrequent events for currently operating wet BA systems.\98\ Since
these calculations are only estimates, the EPA solicits data on actual
precipitation and maintenance-related discharges. For purposes of
calculating the allowance percentage associated with such infrequent
events, the EPA divided the discharge associated with an estimated
maintenance and precipitation event by the volume of the system, and
then averaged the resulting percent over 30 days.
---------------------------------------------------------------------------

    \97\ Although the technology basis includes dry handling, the
limitation is based on the necessary purge volumes of a wet, high
recycle rate BA system.
    \98\ Although presented in EPRI (2018), the EPA did not consider
events such as pipe leaks, as these would not be reflective of
proper system operation (see DCN SE06920).
---------------------------------------------------------------------------

    Finally, the EPA added each reported regular discharge percent from
EPRI (2016) to the averaged infrequent discharge percent under four
scenarios: (1) With no infrequent discharge event, (2) with only a
precipitation-related discharge event, (3) with only a maintenance-
related discharge event, and (4) with both a precipitation-related and
maintenance-related discharge event. These potential discharge needs
are reported in Table XIV-2 below. Consistent with the statistical
approach used to develop limitations and pretreatment standards for
individual pollutants, the EPA selected a 95th percentile of 10 percent
of total system volume as representative of the 30-day rolling
average.\99\
---------------------------------------------------------------------------

    \99\ While there were further decimal points for the actual
calculated 95th percentile, the EPA notes that 10 percent is two
significant digits, consistent with the limitations for FGD
wastewater pollutants. Furthermore, a 10 percent volumetric limit
will be easier for implementation by the permitting authority as it
results in a simple decimal point movement for calculations.

                                  Table XIV-2--30-Day Rolling Average Discharge Volume as a Percent of System Volume a
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Infrequent discharge needs as estimated in EPRI (2018)     Regular discharge needs to maintain water chemistry and/or water balance as characterized
--------------------------------------------------------------                                       in EPRI (2016)
                                                     30-Day   ------------------------------------------------------------------------------------------
       Type of infrequent discharge event           rolling                                                                     Facility F-- Facility F--
                                                    average     Facility A   Facility B   Facility C   Facility D   Facility E    System 1     System 2
                                                          (%)          (%)          (%)          (%)          (%)          (%)          (%)          (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       0.1          0.0          1.0          0.0          0.8          2.0          2.0
Neither Event...................................          0.0          0.1          0.0          1.0          0.0          0.8          2.0          2.0
Precipitation Only..............................          5.4          5.5          5.4          6.4          5.4          6.2          7.4          7.4
Maintenance Only................................          3.3          3.4          3.3          4.3          3.3          4.1          5.3          5.3
Both Events.....................................          8.7          8.8          8.7          9.7          8.7          9.5         10.7         10.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ These estimates sum actual/reported, facility-specific regular discharge needs with varying combinations of hypothetically estimated, infrequent
  discharge needs.

    The EPA recognizes that some facilities may need to improve their
equipment, process controls, and/or operations to consistently meet the
zero discharge standard established by the 2015 rule. However, with the
discharge allowance included in this proposed rule, the EPA expects
that facilities would be able to avoid these costs in most
circumstances. For example, in the table above, only when the Facility
F systems experience both high-end precipitation- and maintenance-
related discharge events could the required discharge potentially
exceed the 30-day rolling average of 10 percent. This is consistent
with the CWA, which requires that BAT/PSES discharge limitations and
standards reflect the best available technology economically
achievable. For further discussion of costs associated with managing a
fully-closed-loop system, see Section 5 of the Supplemental TDD.
2. Best Management Practices Plan
    As described in Section VII of this preamble, one of the regulatory
options presented in today's proposed rule would require a subcategory
of facilities discharging BA transport water and having low MWh
production to develop and implement a BMP plan to recirculate BA
transport water back to the BA handling system (see Section VII of this
preamble for more details).
    The proposed BMP provisions would require applicable facilities to
develop a plan to minimize the discharge of pollutants by recycling as
much BA transport water as practicable back to the BA handling system.
For example, if a facility could recycle 80 percent of its BA transport
water for a few thousand dollars, but recycling 81 percent would
require the installation of a multi-million dollar system, the former
would be practicable, but the latter would not.\100\ After determining
the amount of BA transport water that could be easily recycled and
developing a facility-specific BMP plan, facilities are required to
implement the plan and annually review and revise the plan as
necessary.
---------------------------------------------------------------------------

    \100\ The limit of what is practicable at a facility may change
drastically after making changes to comply with the CCR rule. For
instance, if a facility closes its unlined surface impoundment and
installs a remote MDS, the recycle rate that is practicable may
approach that of the high recycle systems that the EPA used to
establish BAT for units not falling into this subcategory.
---------------------------------------------------------------------------

XIV. Regulatory Implementation

A. Implementation of the Limitations and Standards

    The requirements in this rule apply to discharges from steam
electric facilities through incorporation into NPDES permits issued by
the EPA or by authorized states under Section 402 of the Act, and
through local pretreatment programs under Section 307 of the Act.
Permits or control mechanisms issued after this rule's effective date
must incorporate the ELGs, as applicable. Also, under CWA section 510,
states can require effluent limitations under state law as long as they
are no less stringent than the requirements of this rule. Finally, in
addition to requiring application of the technology-based ELGs in this
rule, CWA section 301(b)(1)(C) requires the permitting authority to
impose more stringent effluent limitations, as necessary, to meet
applicable water quality standards.
1. Timing
    The direct discharge limitations proposed in this rule would apply
only when implemented in an NPDES permit issued to a discharger. Under
the CWA, the permitting authority must incorporate these ELGs into
NPDES permits as a floor or a minimum level of control. The proposed
rule would allow a permitting authority to determine a date when the
new effluent limitations for FGD wastewater and BA transport water will
apply to a given discharger. As proposed, the permitting authority
would make these effluent limitations applicable on or after November
1, 2020. For any final effluent limitation that is specified to become
applicable after November 1, 2020, the specified date must be as soon
as possible, but in no case later than December 31, 2023, for BA
transport water, or December 31, 2025, for FGD wastewater. For
dischargers choosing to meet the voluntary incentives program effluent
limitations for FGD wastewater, the date for meeting those limitations
is December 31, 2028.
    For FGD wastewater and BA transport water from boilers retiring by
2028, the proposed BAT limitations would apply on the date that a
permit is issued to a discharger. The proposed rule does not build in
an implementation period for meeting these limitations, as the BAT
limitation on TSS is equal to the previously promulgated BPT limitation
on TSS. Pretreatment standards are self-implementing, meaning they
apply directly, without the need for a permit. As defined by the
statute, the pretreatment standards for existing sources must be met by
three years after the effective date of any final rule.
    Regardless of when a facility's NPDES permit is ready for renewal,
the EPA recommends that each facility immediately begin evaluating how
it intends to comply with the requirements of any final rule. In cases
where significant changes in operation are appropriate, the EPA
recommends that the facility discuss such changes with its permitting
authority and evaluate appropriate steps and a timeline for the changes
as soon as a final rule is issued, even prior to the permit renewal
process.
    In cases where a facility's final NPDES permit is issued before
these ELGs are finalized, and includes limitations for BA transport
water and/or FGD wastewater from the 2015 rule, EPA recommends such a
permit be reopened as soon as practicable, and modified consistent with
any new rule provisions.
    For permits that are issued on or after November 1, 2020, the
permitting

authority would determine the earliest possible date that the facility
can meet the limitations (but in no case later than December 31, 2023,
for BA transport water or December 31, 2025, for FGD wastewater), and
apply the proposed limitations as of that date (BPT limitations or the
facility's other applicable permit limitations would apply until such
date).
    As proposed, the ``as soon as possible'' date determined by the
permitting authority is November 1, 2020, unless the permitting
authority determines another date after receiving facility-specific
information submitted by the discharger.\101\ EPA is not proposing to
revise the specified factors that the permitting authority must
consider in determining the as soon as possible date. Assuming that the
permitting authority receives relevant, site-specific information from
each discharger, in order to determine what date is ``as soon as
possible'' within the implementation period, the factors established in
the 2015 rule are:
---------------------------------------------------------------------------

    \101\ Information in the record indicates that most facilities
should be able to complete all steps to implement changes needed to
comply with proposed BA transport water requirements within 15-23
months, and the FGD wastewater requirements within 26 to 34 months.
---------------------------------------------------------------------------

    (a) Time to expeditiously plan (including to raise capital),
design, procure, and install equipment to comply with the requirements
of the final rule.\102\
---------------------------------------------------------------------------

    \102\ Cooperatives and municipalities presented information to
the EPA suggesting that obtaining financing for these projects can
be more challenging than for investor-owned utilities. Under this
factor, permitting authorities may consider whether the type and
size of owner and difficulty in obtaining the expected financing
might warrant additional flexibility up to the ``no later than''
date.
---------------------------------------------------------------------------

    (b) Changes being made or planned at the facility in response to
greenhouse gas regulations for new or existing fossil fuel-fired
facilities under the Clean Air Act, as well as regulations for the
disposal of coal combustion residuals under subtitle D of the Resource
Conservation and Recovery Act.
    (c) For FGD wastewater requirements only, an initial commissioning
period to optimize the installed equipment.
    (d) Other factors as appropriate.
    The EPA proposes to clarify that the discharger must provide
relevant, site-specific information for consideration of these factors
by the permitting authority. Environmental groups informed the EPA that
facilities had filed permit applications for, and states had granted,
delayed applicability dates based on information about a facility other
than the one being permitted. This was not the intent of the 2015 rule,
and the EPA solicits comment on other potential misunderstandings of
the factors presented in the 2015 rule that may have caused confusion
or led to misunderstandings.
    As specified in factor (b), the permitting authority must also
consider scheduling for installation of equipment, which includes a
consideration of facility changes planned or being made to comply with
certain other key rules that affect the steam electric power generating
industry. As specified in factor (c), for the FGD wastewater
requirements only, the permitting authority must consider whether it is
appropriate to allow more time for implementation in order to ensure
that the facility has appropriate time to optimize any relevant
technologies.
    The ``as soon as possible'' date determined by the permitting
authority may or may not be different for each wastestream. The
permitting authority should provide a well-documented justification of
how it determined the ``as soon as possible'' date in the fact sheet or
administrative record for the permit. If the permitting authority
determines a date later than November 1, 2020, the justification should
explain why allowing additional time to meet the proposed limitations
is appropriate, and why the discharger cannot meet the effluent
limitations as of November 1, 2020. In cases where the facility is
already operating the proposed BAT technology basis for a specific
wastestream (e.g., dry FA handling system), operates the majority of
the proposed BAT technology basis (e.g., FGD chemical precipitation and
biological treatment, without sulfide addition), or expects that
relevant treatment and process changes would be in place prior to
November 1, 2020 (for example due to the CCR rule), it would not
usually be appropriate to allow additional time beyond that date.
Regardless, in all cases, the permitting authority would make clear in
the permit by what date the facility must meet the proposed
limitations, and that date, as proposed, would be no later than
December 31, 2023, for BA transport water, or December 31, 2025, for
FGD wastewater.
    Where a discharger chooses to participate in the VIP and be subject
to effluent limitations for FGD wastewater based on membranes, the
permitting authority must allow the facility up to December 31, 2028,
to meet those limitations. Again, the permit must make clear that the
facility must meet the limitations by December 31, 2028.
2. Implementation for the Low Utilization Subcategory
    The EPA is proposing to establish a new subcategory for low
utilization boilers with net generation below 876,000 MWh per year. The
EIA defines net generation as, ``The amount of gross generation less
the electrical energy consumed at the generating station(s) for station
service or auxiliaries. Note: Electricity required for pumping at
pumped-storage plants is regarded as electricity for station service
and is deducted from gross generation.'' \103\ Unlike other
subcategories, which often require that a facility possess some static
characteristic (e.g., less than 50 MW nameplate capacity), the proposed
low utilization subcategory is based on the fluctuating net generation
reported annually to the EIA. Thus, the EPA is clarifying how
permitting authorities can determine whether a facility qualifies for
this subcategorization, and how limitations for boilers in this
subcategorization are to be implemented.
---------------------------------------------------------------------------

    \103\ See EIA Glossary, available online at: https://www.eia.gov/tools/glossary/index.php?id=N.
---------------------------------------------------------------------------

a. Determining Boiler Net Generation
    When a facility seeks to have limitations for one or more
subcategorized boilers incorporated into its permit, the EPA is
proposing that the facility provide the permitting authority its
calculation of the average of the most recent two calendar years of net
generation for that boiler(s). A facility wishing to seek this
subcategory, must operate below this threshold before the latest
implementation dates, but a permitting authority should also refrain
from establishing a ``no later than date'' which would restrict a
facility from demonstrating two years of reduced net generation. This
average should primarily be collected and calculated using data
developed for reporting to the EIA, since using net generation
information already collected for the EIA will both eliminate the
potentially unnecessary paperwork burden of a separate information
gathering and calculations and allow the permitting authority to more
easily verify the accuracy of the reported values. If it is necessary
for a facility to apportion facility-wide energy consumption not
specifically attributable to individual boilers, the facility must
apportion this consumption proportionally, by boiler nameplate
capacity, unless it adequately documents a sufficient rationale for an
alternate apportionment. The use of a two-year average will ensure that
a low utilization boiler responding to a single extreme demand event in
one year (e.g.,

unexpectedly high peak demand in summer or winter) can still qualify
for this subcategory if its average net generation over the two years
remains below 876,000 MWh. Furthermore, the facility must annually
provide the permitting authority an updated two-year average net
generation for each subcategorized boiler within 60 days of submitting
annual net generation information to the EIA.
b. Tiering Limitations
    In cases where a facility seeks to have limitations for this
subcategory incorporated into its permit, the EPA is proposing that a
permitting authority incorporate two additional features. First, the
EPA is proposing that the limitations for this subcategory be included
as the first of two sets of limitations. The second set of limitations
would be those applicable to the rest of the steam electric generation
point source category. Second, the EPA is proposing that these tiered
limits have a two-year timeframe to be implemented for a facility
exceeding the two-year net generation requirements as measured per
calendar year. For example, if a facility reported it exceeded a two-
year average net generation of 876,000 MWh for a unit, it would have
two years before discharges of FGD wastewater and BA transport water
would henceforth be subject to the second tier of limitations.\104\
Application of the second tier would preclude future use of the low
utilization subcategory.
---------------------------------------------------------------------------

    \104\ Once a facility installs the capital equipment needed to
meet the second tier of limitations, O&M costs will be proportional
to the utilization of the boiler, and thus would no longer result in
disproportionate costs.
---------------------------------------------------------------------------

    These tiered limitations would ensure that, if a boiler that
qualified for this subcategorization changes its operation such that it
no longer qualifies, it would be automatically subject to the second
set of limitations. An automatic feature makes sense for several
reasons. Tiered limitations are beneficial to the regulated facility
because they provide certainty that the facility would not be
considered in violation of its permit initially, when exceeding the
required net generation, nor subsequently, during the two-year
timeframe over which it has to meet the second tier of effluent
limitations. Two years is also consistent with the engineering
documents provided to the EPA for the installation of the appropriate
technologies. Tiered limitations are beneficial to the state because
they avoid the potentially onerous permit modification process and its
burden to the permitting authority. Finally, tiered limitations are
beneficial to the environment because they ensure a timely transition
to more stringent limitations as soon as the reason for the less
stringent limitations (disproportionate cost) is gone. The EPA solicits
comment on the inclusion of tiered limitations.
3. Addressing Withdrawn or Delayed Retirement
    Since the 2015 rule, the EPA has learned of several instances when
facilities have withdrawn or delayed retirement announcements for coal-
fired boilers and facilities. These instances can be grouped into two
categories. First, some delays were involuntary, resulting from orders
issued by the Department of Energy (DOE) or Public Utility Commissions
(PUCs). The remaining announcements were withdrawn or delayed
voluntarily due to changed circumstances. While both the voluntary and
involuntary changes to announced retirements were infrequent, the EPA
acknowledges that such changes will necessarily impact a facility's
status with regard to some of the new subcategories in today's
proposal. These situations are discussed below. For further information
on announced retirements, see DCN SE07207.
a. Involuntary Retirement Delays
    At least five facilities with announced retirement dates had those
dates involuntarily delayed as a result of the DOE issuing orders under
Section 202(c) of the Federal Power Act, or a PUC issuing a reliability
must-run agreement. Such involuntary operations have raised questions
about the conflict between legal obligations to produce electricity and
legal obligations under environmental statutes.\105\ Today's proposal
would subcategorize low utilization boilers and boilers retiring by
2028, subjecting those subcategories to less stringent limitations.
However, both utilization and retirement could be impacted by
involuntary orders and agreements. Thus, the EPA proposes a savings
clause that would be included in all permits where a facility seeks
limitations under one of these two subcategories. Such a savings clause
would protect a facility which involuntarily fails to qualify for the
subcategory for low utilization or retiring boilers, and would allow
that facility to prove that, but for the order or agreement, it would
have qualified for the subcategory. The EPA solicits comment on whether
the proposed savings clause is broad enough to address all scenarios
that may result in a mandatory order to operate a boiler.
---------------------------------------------------------------------------

    \105\ Moeller, James. 2013. Clean air vs. electric reliability:
The case of the Potomac River Generating Station. September.
Available online at: https://scholarlycommons.law.wlu.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1077&context=jece.
---------------------------------------------------------------------------

b. Voluntary Retirement Withdrawals and Delays
    Units at five facilities with announced retirement dates had those
dates voluntarily withdrawn or delayed due to changed situations,
including market conditions, unavailability of natural gas pipelines,
changes in environmental regulations, and sale of the facility. Like
the involuntary retirement delays discussed in the section above, these
situations could impact a facility's qualification for the proposed
subcategories for low utilization boilers and boilers retiring by 2028.
Unlike the involuntary retirement delays, these voluntary delays and
withdrawals can be accounted for through the normal integrated resource
planning process. Thus, the EPA does not propose a similar savings
clause for such units. Instead, a facility should carefully plan its
implementation of the ELGs.

B. Reporting and Recordkeeping Requirements

    This proposal includes five new reporting and recordkeeping
standards. First, the EPA is proposing a reporting and recordkeeping
standard for facilities operating high recycle rate BA systems. The EPA
is proposing that such facilities submit the calculation of the primary
active wetted BA system volume, which means the maximum volumetric
capacity of BA transport water in all piping (including recirculation
piping) and primary tanks of a wet bottom ash system, excluding the
volumes of installed spares, redundancies, maintenance tanks, other
secondary bottom ash system equipment, and non-bottom ash transport
systems that may direct process water to the bottom ash system. This
ensures that the permitting authority can verify the volume of
discharge allowed for a high recycle rate system. The EPA solicits
comment on the specific components of the BA transport water system
that should be included and/or excluded from the calculation of primary
active wetted BA system volume.
    Second, the EPA is proposing a reporting and recordkeeping
requirement for facilities seeking subcategorization of low utilization
boilers. The EPA is proposing that, as part of any permit renewal or
re-opening, such facilities submit a calculation of the two-year
average net generation for each applicable boiler to

the permitting authority, including underlying information. Once any
limitations of this subcategory are applicable, the EPA is proposing
that such a facility annually recertify that the boiler continues to
meet the requirements of this subcategory, along with an updated two-
year average net generation calculation and information for each
applicable boiler. As proposed, if a boiler exceeds the MWh
requirements of this subcategory, no further recordkeeping or reporting
would be required, as this boiler would be treated the same as the rest
of the steam electric point source category after the necessary
treatment equipment was installed and operational at the end of two
years.
    Third, as described in Section VII.C.2, facilities with boilers
that qualify for the low-utilization subcategory and that discharge BA
transport water, would be required to develop and implement a BMP plan
to minimize the discharge of pollutants by recycling as much BA
transport water as practicable back to the BA handling system. As part
of any permit renewal or any re-opening, such facilities would need to
submit their facility-specific plan (certified that it meets the
proposed requirements of 40 CFR 423.13(k)(3)) along with a
certification that the plan is being implemented. For each permit
renewal, the plan and PE certification should be updated and provided
to the permitting authority.
    Fourth, the EPA is proposing reporting and recordkeeping
requirements for facilities seeking subcategorization for a boiler(s)
retiring by December 31, 2028. The EPA is proposing that, as part of
the permit renewal or re-opening, which are when a facility would make
this request, such facilities submit a one-time certification to the
permitting authority stating the date of expected retirement from the
combustion of coal, and provide a citation to any filing, integrated
resource plan, or other documentation in support of that date. This
citation is meant to provide the permitting authority further evidence
that a boiler will, in fact, cease the production of electricity by
that date.
    Finally, the EPA is proposing reporting and recordkeeping
requirements for facilities invoking the proposed savings clause. The
EPA is proposing that such facilities must demonstrate that a boiler
would have qualified for the subcategory at issue, if not for the
emergency order issued by the DOE under Section 202(c) of the Federal
Power Act or PUC reliability must-run agreement. Furthermore, the EPA
is proposing to require a copy of such order or agreement as an
attachment to the submission.

C. Site-Specific Water Quality-Based Effluent Limitations

    The EPA regulations at 40 CFR 122.44(d)(1) require that each NPDES
permit shall include any requirements, in addition to or more stringent
than effluent limitations guidelines or standards promulgated pursuant
to sections 301, 304, 306, 307, 318 and 405 of the CWA, necessary to
achieve water quality standards established under section 303 of the
CWA, including state narrative criteria for water quality. Furthermore,
those same regulations require that limitations must control all
pollutants, or pollutant parameters (either conventional,
nonconventional, or toxic pollutants) which the Director determines are
or may be discharged at a level which will cause, have the reasonable
potential to cause, or contribute to an excursion above any state water
quality standard, including state narrative criteria for water quality.
    Bromide was discussed in the preamble to the 2015 rule as a
parameter for which water quality-based effluent limitations may be
appropriate. The EPA stated its recommendation that permitting
authorities carefully consider whether water quality-based effluent
limitations on bromide or TDS would be appropriate for FGD wastewater
discharges from steam electric facilities upstream of drinking water
intakes. The EPA also stated its recommendation that the permitting
authority notify any downstream drinking water treatment plants of the
discharge of bromide.
    The EPA is not proposing additional limitations on bromide for FGD
wastewater beyond the removals that might be accomplished by facilities
choosing to implement the VIP limitations, though the EPA is soliciting
comment on the three potential bromide-specific sub-options presented
in Section VII of this preamble. The record continues to suggest that
state permitting authorities should consider establishing water
quality-based effluent limitations that are protective of populations
served by downstream drinking water treatment facilities. As described
in Section XII, the analysis of changes in human health benefits
associated with changes in bromide discharges are concentrated at a
small number of sites. This supports the EPA's determination that
potential discharges are best addressed using site-specific, water
quality-based effluent limitations established by permitting
authorities for the small number of steam electric facilities that may
impact downstream drinking water treatment facilities.

XV. Related Acts of Congress, Executive Orders, and Agency Initiatives

A. Executive Orders 12866 (Regulatory Planning and Review) and 13563
(Improving Regulation and Regulatory Review)

    This proposed rule is an economically significant regulatory action
that was submitted to the Office of Management and Budget (OMB) for
review. Any changes made in response to OMB recommendations have been
documented in the docket. The EPA prepared an analysis of the potential
social costs and benefits associated with this action. This analysis is
contained in Chapter 13 of the BCA, available in the docket. The
analysis in the BCA builds on compliance costs and certain other
assumptions regarding compliance years discussed in the RIA to estimate
the incremental social costs and benefits of the four proposed options
relative to the baseline. Analyzing the options against the baseline
enables the Agency to characterize the incremental impact of ELG
revisions proposed by this action.
    Table XV-1 presents the annualized value of the social costs and
benefits over 27 years and discounted using a three percent discount
rate as compared to the updated baseline. Table XV-2 presents
annualized values using a seven percent discount rate. In both tables,
negative costs indicate avoided costs (i.e., cost savings) and negative
benefits indicate forgone benefits.

            Table XV-1--Total Monetized Annualized Benefits and Costs of Proposed Regulatory Options
                                [Million of 2018$, three percent discount rate] a
----------------------------------------------------------------------------------------------------------------
                                                                          Total monetized benefits c d e
                Regulatory option                  Total social  -----------------------------------------------
                                                      costs b      Low estimate    Mid estimate    High estimate
----------------------------------------------------------------------------------------------------------------
Option 1........................................         -$130.6          -$41.0          -$43.6          -$86.6
Option 2........................................          -136.3            14.8            19.6            68.5

Option 3........................................           -90.1            35.1            41.3           109.4
Option 4........................................            11.9            98.4           105.9           188.9
----------------------------------------------------------------------------------------------------------------
\a\ All social costs and benefits were annualized over 27 years using a 3% discount rate. Negative costs
  indicate avoided costs and negative benefits indicate forgone benefits. All estimates are rounded to one
  decimal point, so figures may not sum due to independent rounding.
\b\ Total social costs are compliance costs to facilities accounting for the timing those costs are incurred.
\c\ Total monetized benefits exclude other benefits discussed qualitatively.
\d\ The EPA estimated the air-related benefits for Option 2 using the IPM sensitivity analysis scenario that
  includes the ACE rule in the baseline (IPM-ACE). EPA extrapolated estimates for Options 1 and 3 air-related
  benefits from the estimate for Option 2 that is based on IPM-ACE outputs. The values for Option 4 air-related
  benefits were estimated using the IPM analysis scenario that does not include the ACE rule in the baseline.
  See Chapter 8 in the BCA for details). The EPA estimated air-related benefits for Options 1 and 3 by
  multiplying the total costs for each option by the ratio of [air-related benefits/total social costs] for
  Option 2. The EPA did not monetize benefits of changes in NOX and SO2 emissions and associated changes in
  PM2.5 levels for any option.
\e\ The EPA estimated use and nonuse values for water quality improvements using two different meta-regression
  models of WTP. One model provides the low and high bounds while a different model provides a central estimate
  (included in this table under the mid-range column). For this reason, the mid benefit estimate differs from
  the midpoint of the benefits range. For details, see Chapter 5 in the BCA.

            Table XV-2--Total Monetized Annualized Benefits and Costs of Proposed Regulatory Options
                                [Million of 2018$, seven percent discount rate] a
----------------------------------------------------------------------------------------------------------------
                                                                          Total monetized benefits c d e
                Regulatory option                  Total social  -----------------------------------------------
                                                     costs \b\     Low estimate    Mid estimate    High estimate
----------------------------------------------------------------------------------------------------------------
Option 1........................................         -$154.0          -$13.7          -$16.0          -$53.3
Option 2........................................          -166.2            28.4            32.6            74.4
Option 3........................................          -119.5            37.1            42.5           100.9
Option 4........................................           -27.3            70.6            77.2           148.4
----------------------------------------------------------------------------------------------------------------
\a\ All social costs and benefits were annualized over 27 years using a 7% discount rate. Negative costs
  indicate avoided costs and negative benefits indicate forgone benefits. All estimates are rounded to one
  decimal point, so figures may not sum due to independent rounding.
\b\ Total social costs are compliance costs to facilities accounting for the timing those costs are incurred.
\c\ Total monetized benefits exclude other benefits discussed qualitatively.
\d\ The EPA estimated the air-related benefits for Option 2 using the IPM sensitivity analysis scenario that
  includes the ACE rule in the baseline (IPM-ACE). EPA extrapolated estimates for Options 1 and 3 air-related
  benefits from the estimate for Option 2 that is based on IPM-ACE outputs. The values for Option 4 air-related
  benefits were estimated using the IPM analysis scenario that does not include the ACE rule in the baseline.
  See Chapter 8 in the BCA for details). The EPA estimated air-related benefits for Options 1 and 3 by
  multiplying the total costs for each option by the ratio of [air-related benefits/total social costs] for
  Option 2. The EPA did not monetize benefits of changes in NOX and SO2 emissions and associated changes in
  PM2.5 levels for any option.
\e\ The EPA estimated use and nonuse values for water quality improvements using two different meta-regression
  models of WTP. One model provides the low and high bounds while a different model provides a central estimate
  (included in this table under the mid-range column). For this reason, the mid benefit estimate differs from
  the midpoint of the benefits range. For details, see Chapter 5 in the BCA.

B. Executive Order 13771 (Reducing Regulation and Controlling
Regulatory Costs)

    The proposed regulatory options would be an Executive Order 13771
deregulatory action. Details on the estimated cost savings of the
regulatory options are located in the RIA, and in Tables XV-1 and XV-2
above.

C. Paperwork Reduction Act

    OMB has previously approved the information collection requirements
contained in the existing regulations 40 CFR part 423 under the
provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and
has assigned OMB control number 2040-0281. The OMB control numbers for
the EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    The EPA estimated small changes in monitoring costs at steam
electric facilities under the regulatory options presented in today's
proposal relative to the baseline. As proposed, these changes would
apply to facilities for which the proposed subcategories are
applicable. In some cases, in lieu of these monitoring requirements,
facilities would have additional paperwork burden such as that
associated with certifications and applicable BMP plans. See Section
VII of this preamble. However, some facilities would also realize
savings, relative to the baseline, by no longer monitoring pollutants
for some subcategories of boilers (and because their applicable
limitations and standards are based on less costly technologies). The
EPA projects that the burden associated with the new proposed paperwork
requirements would be largely off-set by the reduced burden associated
with less monitoring; therefore, the Agency projects that the proposal
would have no net effect on the burden of the approved information
collection requirements. With respect to permitting authorities, based
on the information in its record, the EPA also does not expect any of
the regulatory options in today's proposal to increase or decrease
their burden. The proposed options would not change permit application
requirements or the associated review; they would not affect the number
of permits issued to steam electric facilities; nor would the options
change the efforts involved in developing or reviewing such permits.
Accordingly, the EPA estimated no net change (i.e., no increase or
decrease) in the cost burden to federal or state governments or
dischargers associated with any of the regulatory options in this
proposed rule.

D. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice-and-comment

rulemaking requirements under the Administrative Procedure Act or any
other statute, unless the agency certifies that the rule will not have
a significant economic impact on a substantial number of small
entities. Small entities include small businesses, small organizations,
and small governmental jurisdictions.
    The Agency certifies that this action will not have a significant
economic impact on a substantial number of small entities under the
RFA. The basis for this finding is documented in Chapter 8 of the RIA,
included in the docket and summarized below.
    The EPA estimates that 243 to 478 entities own steam electric
facilities to which the regulatory options would apply, of which 79 to
127 are small. These small ownership entities own a total of 139 steam
electric facilities. The EPA considered the impacts of the regulatory
options presented in this proposal on small businesses using a cost-to-
revenue test. The analysis compares the cost of implementing controls
for BA and FGD wastewater under the four regulatory options to those
under the baseline (which reflects the 2015 rule as explained in
Section V of this preamble). Small entities estimated to incur
compliance costs exceeding one or more of the one percent and three
percent impact thresholds were identified as potentially incurring a
significant impact. The EPA's analysis shows that four small entities
(municipalities) are expected to incur costs equal to or greater than
one percent of revenue to meet the 2015 rule; for two of these
municipalities, the costs to meet the 2015 rule exceed three percent of
revenue. Cost savings provided under the regulatory options reduce the
impacts on these small entities to varying degrees. Option 2 has the
greatest mitigating effect on small entities, reducing to 2 the number
of small entities incurring costs equal to or greater than one percent
of revenue, and to 1 the entities with costs greater than three percent
of revenue. Options 1, 3, and 4 have similar mitigating effects, with
one fewer small entity incurring costs equal to or greater than one
percent of revenue. The number of small entities exceeding either the
one or three percent impact threshold in the baseline is small in the
absolute and represents small percentages of the total estimated number
of small entities; the cost savings provided by the regulatory options
further support the EPA's finding of no significant impact on a
substantial number of small entities (No SISNOSE).

E. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2
U.S.C. 1531-1538, requires federal agencies, unless otherwise
prohibited by law, to assess the effects of their regulatory actions on
state, local, and tribal governments, and the private sector. An action
contains a federal mandate if it may result in expenditures of $100
million or more (annually, adjusted for inflation) for state, local,
and tribal governments, in the aggregate, or the private sector in any
one year ($160 million in 2018).
    The EPA finds that this action is not subject to the requirements
of UMRA section 203 because the expenditures are less than $160 million
or more in any one year. As detailed in Chapter 9 of the RIA, for its
assessment of the impact of potential changes in compliance
requirements on small governments (governments for populations of less