EPA
ACID RAIN
PROGRAM
2001
PROGRESS
REPORT
November 2002
-------
This Progress Report replaces the Compliance Report and the Emissions Scorecard used in pre-
vious years to report on the results of the Acid Rain Program. All data and results from the Acid
Rain Program are now compiled in a single document that reports information on:
4 emission levels
4 compliance with the SO2 and NOx components of the program
4 SO2 allowance prices
4 emissions monitoring
4 air quality and deposition monitoring
4 environmental and human health effects and benefits
This Progress Report will be published annually by EPA to update the public on the status of
implementation of the Acid Rain Program and our progress towards achieving our environmental
goals. Detailed unit-level emissions data are available on our website at http://www.epa.gov/air-
markets/emissions/index. Our new query tool that provides access to a variety of EPA emissions
data is available at http://cfpub.epa.gov/gdm. For more information on the Acid Rain Program,
including information on SO2and NOX emissions, acid deposition monitoring, and the environ-
mental effects of acid deposition, you can visit our website at http://www.epa.gov/airmarkets.
EPA Acid Rain Program
2001 Progress Report
EPA-430-R-02-009
Clean Air Markets Program
Office of Air and Radiation
U.S. Environmental Protection Agency
November, 2002
\NAIR
MARKET PROGRAMS
ppcrtf
Photo credits (clockwise, from upper left): USDA; SoftKey International; VTweb.com; Rick Webb; SoftKey International; SoftKey Internation-
al; Photodisc.com (center)
-------
Table of Contents
Introduction 1
An Innovative Cap and Trade Program for 862 2
The NOX Program 2
Why Worry about Acid Rain? 3
The S02 Program 5
Emissions 5
Compliance 7
Geographic Trends in S02 Emissions 9
S02 Allowance Market 12
The NOX Program 14
Emissions 14
Emission Limits 16
Compliance 18
Geographic Trends in NOX Emissions 18
Monitoring Results 22
Emission Monitoring 22
Air Quality and Deposition in 2001 23
Clean Air Mapping and Analysis Program (C-MAP) 27
Freshwater Monitoring 27
Environmental Improvement and Trends 29
Improved Air Quality and Reduced Acid Deposition 29
Visibility 34
Human Health Benefits 35
Ecological Effects of Reduced Acid Deposition 35
Freshwater 35
Forests 37
Coastal Waters 37
Materials and Structures 38
Summary 39
For Further Information 41
-------
-------
ntroduction
The Acid Rain Program was established under Title IV of the 1990 Clean Air
Act Amendments. The program requires major reductions of sulfur dioxide
(SO2) and nitrogen oxides (NOx) emissions, the pollutants that cause acid
rain. Using an innovative market-based or "cap and trade" approach to environ-
mental protection, the program sets a permanent cap on the total amount of SO2
that may be emitted by electric power plants nationwide. The cap is set at about
one half of the amount of SO2 emitted in 1980, and the trading component allows
flexibility for individual fossil fuel-fired combustion units to select their own meth-
ods of compliance. The program also sets NOx emission limitations (in pounds
per million British thermal units or Ib/mmBtu) for certain coal-fired electric utility
boilers, representing about a 27% reduction from 1990 levels. The Acid Rain Pro-
gram was implemented in two phases. Phase I applied primarily to the largest
coal-fired sources from 1995 through 1999 for SO2 and from 1996 through 1999
for NOX. Phase II for both pollutants began in 2000 and applies to thousands of
combustion units (see Figure 1). In 2001, there were 2,792 units affected by the
SO2 provisions of the Acid Rain Program. Additionally, 1,046 of these units were
required to meet a NOX emissions limit in 2001 under the Acid Rain Program pro-
visions1. The Acid Rain Program has significantly reduced emissions of SO2 and
• Phase I
• Phase II
Source: EPA
Figure 1. Sources
Affected by the
SO2 Require-
ments of Title IV
(the Acid Rain
Program) of the
1990 Clean Air
Act, 2001
Most Phase I
sources (the
largest, highest-
emitting sources)
were in the Mid-
west; in Phase II
sources nation-
wide are affected
by the Acid Rain
Program.
1 Sources affected by the Acid Rain Program are tracked for compliance purposes at the unit level. A single source (power plant) may have
many units (combustion devices).
page 1
-------
Acid Rain Program Annual Progress Report, 2001
NOX from electric power plants and resulted in substantial environmental and
human health benefits.
An Innovative Cap and Trade Program for SO2
The SO2 component of the Acid Rain Program represents a dramatic departure
from traditional command and control regulatory approaches that establish
source-specific emissions limitations. Instead, the program uses an overall emis-
sions cap for SO2 that ensures emissions reductions are achieved and main-
tained and a trading system that facilitates lowest-cost emissions reductions. The
program features tradeable SO2 emissions allowances, where one allowance is a
limited authorization to emit one ton of SO2. A fixed number of allowances are
issued by the government, and they may be bought, sold, or banked for future use
by utilities, brokers, or anyone else interested in holding them. Existing units are
allocated allowances for each year; new units do not receive allowances and must
buy them. At the end of the year all participants in the program are obliged to sur-
render to EPA the number of allowances that correspond to their annual SO2
emissions.
Affected sources must demonstrate compliance with the SO2 provisions of the
Acid Rain Program at the end of each year. Sources are granted a 60-day grace
period during which additional SO2 allowances may be purchased, if necessary,
to cover each unit's emissions for the year. At the end of the grace period (the
Allowance Transfer Deadline), the allowances a unit holds in its Allowance Track-
ing System (ATS) account must equal or exceed the unit's annual SO2 emissions
for the previous year. The Acid Rain Program requires affected sources to moni-
tor emissions continuously and to report their emissions regularly. Failure to sur-
render sufficient allowances results in significant automatic penalties that include
fines as well as a reduction in the number of allowances allocated in the following
year. Any remaining SO2 allowances may be sold and/or banked for future use.
The NOX Program
The NOX component of the Acid Rain Program, using a more traditional regulato-
ry approach, establishes an emission rate limit for certain types of coal-fired boil-
ers. However, sources are provided a degree of flexibility through emissions aver-
aging provisions, whereby a company can meet the standard emission limitations
by averaging the emissions rates of two or more boilers. This allows sources to
over-control at units where it is technically easier to control emissions, thereby
achieving emissions reductions at a lower cost. Additionally, certain Phase II units
elected to become subject to Phase I limits beginning in 1997. These early elec-
tion units are not subject to the more stringent Phase II limits until 2008.
Sources affected by the NOx portion of the Acid Rain Program must also demon-
strate that they have complied with the NOx provisions at the end of the year.
Sources demonstrate compliance with the NOX program by achieving an annual
emission rate at or below mandated levels.
page 2
-------
Acid Rain Program Annual Progress Report, 2001
Why Worry about Acid Rain?
Acid deposition, more commonly known as acid rain, occurs when emissions of
SO2 and NOX react in the atmosphere (with water, oxygen, and oxidants) to form
various acidic compounds. These acidic compounds then fall to earth in either a
wet form (rain, snow, and fog) or a dry form (gases and particles). Prevailing
winds transport the acidic compounds hundreds of miles, often across state and
national borders. The acidic compounds (including small particles such as sul-
fates and nitrates) cause many negative environmental effects. These pollutants
impair air quality and damage public health, acidify lakes and streams, harm sen-
sitive forest and coastal ecosystems, degrade visibility, and accelerate the decay
of building materials, paints, and cultural artifacts such as buildings, statues, and
sculptures nationwide.
Some places and people are more susceptible or sensitive to these impacts than
others. Areas where acid deposition damages ecosystems or gases and particles
impair visibility are called "sensitive receptors." Sensitive ecological receptors
include lakes and streams throughout the Appalachian Mountains; forests in the
Appalachian Mountains, the Colorado Front Range, and West Coast coastal
mountain ranges; and many East and Gulf coast estuaries and coastal waters.
Many national parks and wilderness areas, including Great Smoky National Park,
Acadia National Park, and Grand Canyon National Park have impaired visibility
due in part to emissions of SO2 and NOX from power generation sources. Many
people (especially children, the elderly and those with existing respiratory or car-
diovascular conditions) are also adversely impacted by fine particles formed from
Cas
San Bernardino ana
San Gabriel Mountain
Nitrogen-Saturated Forests
Class 1 areas such as national parks and wilderness areas
Acidic surface waters in surveyed regions
Figure 2. Sensi-
tive Ecological
Receptors
Areas sensitive
to acid deposi-
tion, nitrogen-
overenrichment,
and visibility
impairment
occur nation-
page 3
-------
Acid Rain Program Annual Progress Report, 2001
SO2 and NOX emissions and ozone formed from NOx emissions from power gen-
eration sources.
The pollutants that cause acid rain often cause human health and environmental
impacts hundreds of miles from where they are emitted. This long-range transport
makes it critical to reduce all emissions that cause acid rain, even those that occur
far from sensitive receptors or population centers. The Acid Rain Program's ulti-
mate objective is to protect the environment and improve human health by reduc-
ing SO2 and NOX emissions from power generation sources. These emission
reductions benefit the nation by:
4 Improving air quality and protecting public health
4 Restoring acidified lakes and streams so they can once again support
fish and other aquatic life
4 Improving visibility, especially at scenic vistas in national parks
4 Reducing the damage to sensitive forests, such as those along the
Appalachian Mountains and in the Colorado Front Range
4 Reducing the damage to nitrogen-sensitive coastal waters along the East
and Gulf Coasts
4 Protecting our historic buildings and monuments from degradation
page 4
-------
he SO2 Program
There were 2,792 units2 used to produce electric power that were subject to
the SO2 provisions of the Acid Rain Program in 2001 (that is, they operat-
ed, submitted emissions data for SO2, and were subject to annual recon-
ciliation of allowable emissions with actual emissions in 2001). Acid Rain Program
sources reduced their combined SO2 emissions in 2001 by 39% from 1980 levels
(33% from 1990 levels). All but two of the 2,792 units complied with the require-
ment to hold sufficient allowances. There were no significant geographic shifts in
emissions. The price of an SO2 allowance ranged from $135 to $210/ton in 2001,
a price range that is comparable to allowance prices in previous years.
Emissions
In 2001, the second year of Phase II, Acid Rain Program sources achieved a total
reduction in SO2 emissions of about 39% compared to 1980 levels (33% com-
pared to 1990 levels). Compared to 2000 levels, these sources reduced their SO2
emissions by 5% or 569,000 tons. Figure 3 shows the trend in SO2 emissions
18
16
14
J 10 -
17.30
1&
-------
Acid Rain Program Annual Progress Report, 2001
since 1980 for all affected sources.
The electric utility industry is by far the largest single source of sulfur dioxide
emissions, accounting for approximately 65% of total SO2 emissions nationwide.
In addition to the significant reductions from the electric power generation sector,
reductions in SO2 emissions from other sources, including smelters and sulfuric
acid manufacturing plants, and use of cleaner fuels in residential and commercial
burners, have also contributed to the 50% decline of SO2 emissions from all
sources since 1980 (National Air Quality and Emissions Trends Report, 1999).
There were 2,792 units that underwent annual reconciliation for SO2 in 2001.
(These units, as well as an additional 273 units which were retired or not yet oper-
ating, are listed in Appendix A of this Report. Appendix A is available on our web-
site at www.epa.gov/airmarkets/cmprpt/arp01/index.htmr).
The allowances (i.e., authorizations to emit SO2) allocated in a particular year to
each source are determined by several provisions of the Clean Air Act. For the
year 2001, a total of 9.55 million allowances were granted. Adding these 9.55 mil-
lion allowances to the unused allowances carried over (or banked) from prior
years, a total of 19.93 million allowances were available for use in 2001. Sources
emitted 10.63 million tons in 2001, 1.08 million tons more than the allowances
granted in 2001 but far less than the allowable level. For the second year in a row
the number of allowances in the bank declined. As shown in Figure 4, the bank
shrank by 1.08 million allowances in 2001. Over time the bank is expected to con-
tinue to be depleted as sources use these banked allowances to comply with the
Figure 4. Allocat-
ed, Used,and
Banked SO2
Allowances
The bank was
built up during
Phase I with
early reductions
and is now
being drawn
down under
Phase II.
25
20
D Allowances allocated that year
• Unused allowances from previous years (bank)
^^ Emissions from affected sources
1995
1996 1997 1998 1999 2000 2001
Source: EPA
page 6
-------
Acid Rain Program Annual Progress Report, 2001
Type of Allowance
Allocation
Initial Allocation
Allowances for
Substitution Units
Allowance Auctions
Opt-in Allowances
TOTAL 2001
ALLOCATION
Banked Allowances
Conservation and
Renewable Energy
Allowances
TOTAL 2001
ALLOWABLE
Number of
Allowances
9,190,9223
13,547
250,000
99,188
9,553,657
10,376,426
3,528
19,933,611
Explanation of Allowance Allocation
Type
Initial Allocation is the number of
allowances granted to units based on the
product of their historic utilization and
emissions rates (performance standards)
specified in the Clean Air Act.
A lawsuit settlement allowed for a small
amount of allowances to be allocated for
Substitution Units in 2001 instead of an
earlier year during Phase I.
Allowance Auctions provide allowances to
the market that were set aside in a Special
Allowance Reserve when the initial
allowance allocation was made.
Opt-in Allowances are provided to units
entering the program voluntarily. There
were 1 1 opt-in units in 2001 .
Banked Allowances are those held over
from 1995 through 2000 which can be used
for compliance in 2001 or any future year.
These allowances come from a special
reserve set aside when the initial allowance
allocation was made. They are awarded to
utilities that undertake efficiency and
renewable energy measures. These are
year 1999 allowances that were allocated in
year 2001 .
3 The total year 2001 initial allocation was 9,191,897. Fifty-four allowances were deducted as offsets dur-
ing year 2000 reconciliation, and 921 allowances were surrendered as part of an enforcement action
prior to the 2001 reconciliation.
Source: EPA
Figure 5. Origin
of 2001 Allow-
able Emissions
Level
There were
9.55 million
allowances allo-
cated in 2001;
an additional
10.38 million
allowances had
been banked in
previous years
and were avail-
able for use.
stringent Phase II requirements. Figure 5 explains in more detail the origin of the
allowances available for use in 2001.
Compliance
A total of 10.6 million allowances were deducted from sources' accounts in 2001.
Two units were short a total of 11 allowances to cover their emissions for the 2001
compliance year. Eleven year 2002 allowances were taken from these units as
page 7
-------
Acid Rain Program Annual Progress Report, 2001
"offsets" and are included in the total number of used allowances for 2001. In
addition to the offsets, the operators of these units were assessed an automatic
monetary penalty totaling $30,514.4 Figure 6 displays these allowance deduc-
tions, as well as the remaining bank of 1995 through 2001 allowances.
During the compliance process, the number of allowances surrendered at an indi-
vidual unit is equal to the number of tons emitted at the unit, except where the unit
shared a common stack with other units. For the purposes of surrendering
allowances for emissions at a common stack, the source was allowed to choose
the proportion of allowances deducted from each unit sharing the stack, as long
as enough allowances were surrendered to cover the total number of tons emit-
ted. If no such apportionment was made, EPA deducted allowances equally
among the units sharing the stack to cover total emissions reported by the stack.
The deductions for emissions at each unit after the common stack apportionment
was made can be found in Appendix A of this Report. Appendix A is available on
our website at www.epa.gov/airmarkets/cmprpt/arp01/index.html. Units sharing a
common stack are listed directly under the entry for their common stack.
Total Allowances Held in Accounts as of 3/1/2002
(1995 through 2001 Vintages)5
Unit Accounts
General Accounts6
Allowances Deducted for Emissions (1995 through
2001)
2002 Penalty Allowances Deducted
Banked Allowances
Unit Accounts
General Accounts6
19,933,611
14,749,028
5,184,583
10,633,035
11
9,300,576
4,115,993
5,184,583
5 The number of allowances held in the Allowance Tracking System (ATS) accounts equals the number of
2001 allowances allocated (see Figure 5) plus the number of banked allowances. March 1, 2002 repre-
sents the Allowance Transfer Deadline, the point in time at which unit accounts are frozen and after
which no transfers of 1995 through 2001 allowances will be recorded. The freeze on these accounts is
removed when annual reconciliation is complete.
6 General accounts can be established in the ATS by any utility, individual or other entity.
Source: EPA
4 A source that does not hold enough allowances in its unit account to cover its annual SO2 emis-
sions has "excess emissions" and must pay a $2,000 per ton automatic penalty in 1990$. The
$2,000 penalty is adjusted annually for inflation, so the year 2001 penalty was $2,774.
page 8
-------
Acid Rain Program Annual Progress Report, 2001
Geographic Trends in SO2 Emissions
Total sulfur dioxide emissions from power generation have decreased significant-
ly since the Acid Rain Program was authorized by Congress in 1990, and they
continued to decline in 2001, the second year of Phase II. The geographic distri-
bution of SO2 emissions did not change significantly between 1990 and 2001. Fig -
ure 7 displays bar graphs comparing state SO2 emission trends from power gen-
eration before the Acid Rain Program (1990), during Phase I (1995-1999 aver-
age), and in Phase II to date (2000-2001 average).
Several geographic trends are evident:
4 The bar graphs on the map in Figure 7 illustrate that the area with the
highest emissions-the Midwest-also had the largest reductions;
4 SO2 emission reductions during Phase I occurred predominantly in
approximately a dozen states in the Eastern U.S. (Phase I affected the
larger, higher emitting utilities in the Eastern half of the country);
4 The 24 shaded states represent states where SO2 emissions in Phase
II (2000-2001) were lower than both 1990 levels and the 1995-1999
Phase I average. Unlike the SO2 emission reductions achieved during
Phase I, these Phase II reductions are geographically more wide-
spread, occurring in a larger number of Southeastern and some West-
ern states.
In several states, average SO2 emissions during Phase 1 were higher than they
had been in 1990. This is due to the large number of Phase II sources in these
states that were not required to control for SO2 until 2000. In the 2000-2001 peri-
od (Phase II) these emissions declined to levels below what was emitted in 1990.
In general, because SO2 emissions are capped, there will be pressure to contin-
ue to reduce SO2 emissions by installing add-on controls.
Figure 8 illustrates the geographic distribution by state of SO2 emissions from
power generation before implementation of the Acid Rain Program (1990), during
Phase I (1995-1999 average), and in Phase II (2000-2001 average).
In 2001, Title IV sources achieved a 33% reduction from 1990 SO2 levels nation-
wide. SO2 emissions in Texas did increase in Phase I; however, SO2 emissions in
the state decreased in Phase II when the Acid Rain Program requirements took
effect for Texas sources. Although most SO2 emissions still occur in the Midwest-
ern U.S., it is important to note that, over time, this same region has also seen the
most significant decrease in SO2 emissions in the country. The highest SO2 emit-
ting states in 1990 (Ohio, Indiana, and Pennsylvania), reduced emissions 40% in
2001 (49%, 47%, and 22%, respectively) compared to 1990 levels. Other states
in the region show similar trends since 1990. SO2 emissions decreased 59% in
Illinois, 41% in Kentucky, 70% in Missouri, 55% in Tennessee, and 49% in West
Virginia.
page 9
-------
Acid Rain Program Annual Progress Report, 2001
page •
-------
Acid Rain Program Annual Progress Report, 2001
Power Plant SO2 Emissions
(thousand tons)
I| 0-150
150-650
650-1150
1150-1650
>1650
Phase I Average
Figure 8. Geo-
graphic Distribu-
tion of Average
SO2 Emissions
from Acid Rain
Sources by
State, 1990-2001
Since 1990 the
most significant
emissions
reductions have
taken place in
the highest
emitting states.
There have been
no significant
geographic
shifts in emis-
sions since
Phase 11 Average
Source: EPA
page 11
-------
Acid Rain Program Annual Progress Report, 2001
SO2 Allowance Market
The flexibility provided by the Acid Rain Program enabled the 2,792 units subject
to the SO2 requirements in 2001 to pursue a variety of compliance options.
Sources met their SO2 reduction obligations by installing scrubbers, switching
fuels, changing practices or procedures to improve energy efficiency, and buying
allowances. The presence of the allowance market has given some sources the
incentive to reduce their SO2 emissions below the level of their allowance alloca-
tion in order to bank their allowances for use in future years. Other sources have
been able to postpone or reduce expenditures for control by purchasing
allowances from sources that controlled below their allowance allocation level.
The flexibility in compliance options is possible because strict monitoring require-
ments for all affected units ensure one allowance is surrendered for every ton of
SO2 emitted. The program's flexibility significantly reduces the cost of achieving
these emissions reductions as compared to the cost of a technological mandate
or fixed emission rate.
The marginal cost of compliance—the cost of reducing the next ton of SO2 emit-
ted from the utility sector-is reflected in the price of an allowance. Emission
reductions continue to cost less than anticipated when the Clean Air Act Amend-
ments were enacted and this is reflected in the price of allowances. The cost of
an allowance was initially estimated at $400-1,000/ton in 1990 dollars ($500-
1,200/ton in 2001 dollars). As shown in Figure 9, actual prices have been signifi-
cantly lower than predicted. During 2001, SO2 allowances ranged in price from
$135-$210/ton. At the time of the annual allowance auction in April 2001,
allowances were approximately $170/ton. The price rose through the summer,
peaking at $210/ton in late August/early September. During the last quarter of
2001, prices dropped back to around $170/ton and then stabilized. Some market
observers believe lower-than-expected allowance prices during the first several
Figure 9. SO2
Allowance Price
Index
The cost of
allowances in
2001 did not
change substan-
tially from the
previous few
years and
remains far lower
than estimated in
S250
S200
S150
S100
S50
SO r
1/95 186
1/98 1/99 1/00 1/01
1«3
Source: Monthly price reports from Cantor Fitzgerald Environmental Brokerage Services
page 12
-------
Acid Rain Program Annual Progress Report, 2001
Source: EPA
1994 1995 1995 1997 1998 1999 2000 2001
Between economically related organizations
Between economically unrelated organizations
Figure 10. SO2
Allowances
Transferred
under the Acid
Rain Program
The number of
official transfers
between eco-
nomically unre-
lated organiza-
tions has
increased since
years of the program were due primarily to lower than expected compliance costs
and larger than expected emissions reductions, which increased the supply of
allowances and put downward pressure on prices. Additionally, the more stringent
limits in Phase II most likely resulted in higher average prices in 2001 than in 2000
as sources realized they would have to continue to withdraw from the bank and
employ further controls to comply in future years.
The level of activity in the allowance market created under the Acid Rain Program
increased fairly steadily through 2000 and then dropped off somewhat in 2001,
the second year of Phase II. However, the number of official transfers in 2001 was
still higher than in any year of Phase I.
In 2001, 4,900 allowance transfers that affected over 22 million allowances (of
past, current, and future vintages) were recorded in the Allowance Transfer Sys-
tem, the accounting system developed to track holdings of allowances. Of the
allowances transferred, 12.6 million, or 55%, were transferred in economically
significant transactions (i.e., between economically unrelated parties). Figure 10
shows the volume of SO2 allowances transferred under the Acid Rain Program
since official recording of transfers began in 1994. The majority of the allowances
transferred in economically significant transactions were acquired by utilities.
Trades between unrelated organizations accounted for approximately 12 million
allowances in 2001. In December 2001, trading parties began to use the On-line
Allowance Tracking System (OATS). By the end of 2001, OATS recorded 211
transfers electronically over the internet.
All official allowance transactions, as well as data on account balances and own-
ership, are posted and updated daily on the Clean Air Markets Division's website
(www.epa.gov/airmarkets) in order to better inform trading participants of the sta-
tus of the market. Cumulative market statistics and analysis are also available.
page 13
-------
NOX Program
All sources affected by the Acid Rain Program NOX requirements reduced
their combined NOX emissions by 25% from 1990 levels in 2001. All but
one of the 1,046 NOX program affected units complied with their NOx
emission rate limitation. There were no significant shifts in the geographic distri-
bution of emissions due to use of the emissions averaging compliance option.
Emissions
Title IV of the 1990 Clean Air Act requires the Acid Rain Program NOx program
to achieve a 2 million ton reduction from projected NOx emissions levels in 2000.
Total NOX emissions from all Acid Rain Program affected units surpassed that
goal by 1 million tons in 2000 (see Figure 11). Emissions from those sources in
2001 were even less - 3.4 million tons (over 40%) below projected 2000 emis-
sions without the Acid Rain Program. For all 2,792 Title IV affected units, total
Figure 11. NOX
Emissions from
Acid Rain
Sources, 1990-
2001
NOX emissions
have decreased
since 1990, par-
ticularly in
preparation for
and during
Phase II of the
Acid Rain Pro-
gram. Reduc-
tions since 1999
are also due in
part to imple-
mentation of the
Ore NOX Bud-
get Trading Pro-
gram and the
NO, SIP call.
5.97
1990 1995 1996 1997 1998 1999 2000 2001
| NOx Program affected sources
[] Title IV sources not affected for NOx
• • Projected emissions without Title IV
Source: EPA
page 14
-------
Acid Rain Program Annual Progress Report, 2001
- I- ]~ ^t
L p, i *.• *<
page 15
-------
Acid Rain Program Annual Progress Report, 2001
NOX mass emissions in 2001 were 2 million tons lower than emissions in 1990.
Emissions from the 1,046 NOX program affected sources in 2001 were 1.4 million
tons lower than in 1990 and 8% lower than in 2000.
These reductions have been achieved while the amount of fuel burned to produce
electricity, as measured by heat input, increased 28% since 1990. As illustrated
in Figure 12, many states with increasing electricity production have also
decreased total NOX emissions in 2001, as compared to 1990 levels. Without fur-
ther reductions in emissions rates or institution of a cap on NOX emissions, how-
ever, NOx emissions from power plants would have been expected to rise with
increased use of fossil fuels in most areas of the country.
NOX emissions come from a wide variety of sources including those affected by
the Acid Rain Program. NOX emissions from electric utilities account for approxi-
mately 20% of NOx emissions from all sources. NOX emissions from transporta-
tion sources are 55% of NOx emissions from all sources. Nationally, NC^ emis-
sions have increased 5% between 1990 and 1999. This is primarily due to an
increase of 17% in NOX emissions from transportation sources, particularly heavy
duty vehicles, since 1990. That increase has been offset to some extent by the
emissions decreases from electric utilities and other fuel combustion sources due
to a variety of federal and state emission reduction programs (including the Acid
Rain Program, the Ozone Trading Commission NOX Budget Trading Program,
and anticipation of the NOx SIP call) and federal enforcement actions (National
Air Quality and Emissions Trends Report, 1999).
Emission Limits
Instead of using allowance trading to facilitate NOX emissions reductions, the Acid
Rain Program establishes NOx emission limitations (Ib/mmBtu NOx) for coal-fired
electric generation units.
The Acid Rain Program NOX regulation (40 CFR part 76), establishes NC^ limits
for Group 1 boilers (dry bottom wall-fired and tangentially fired boilers), as well as
Group 2 boilers (cell burner, cyclone, vertically-fired, and wet bottom boilers).
Figure 13 shows the number of NOx affected units by boiler type and the emis-
sions limit for each boiler type.
There were 1,046 units subject to NC^ emissions limitations in 2001. The owners
and operators of a NOx affected unit must choose at least one NOX compliance
plan (described below) to indicate how the unit will comply with its NOx 'in*
4 Standard Limitation. A unit with a standard limit simply meets the appli-
cable individual NOX limit prescribed for its boiler type under 40 CFR
76.5, 76.6, or 76.7.
4 Early Election. Under this compliance option, a Phase II Group 1
page 16
-------
Acid Rain Program Annual Progress Report, 2001
affected unit met a less stringent Phase I NOX limit beginning in 1997,
three years before it would normally be subject to an Acid Rain NOx limit.
In return for accepting a NOX limit three years earlier than would normally
be required, an early election unit does not become subject to the more
stringent Phase II NOx limit until ^OS-
Emissions Averaging. A company can meet its NOx emissions reduc-
tion requirements by choosing to make a group of NOx affected boilers
subject to a group NOx 'imit rather than meeting individual NOx limits for
each unit. The group limit is established at the end of each calendar
year, and the group rate for the units must be less than or equal to the
Btu-weighted rate at which the units would have been limited had each
been subject to an individual NOX limit.
Alternative Emission Limitation (AEL). A utility can petition for a less
stringent AEL if it properly installs and operates the NOX emissions
reduction technology prescribed for that boiler but is unable to meet its
standard limit. EPA determines whether an AEL is warranted based on
analyses of emissions data and information about the NOx control equip-
ment.
Coal-Fired Boiler Type7
Phase I Group"! Tangentially-fired
Phase I Groupl Dry Bottom Wall-fired
Phase II Group 1 Tangentially-fired
Phase II Group 1 Dry Bottom Wall-fired
Cell Burners
Cyclones > 155 MW
Wet Bottom > 65 MW
Vertically-fired
Standard
Emission
Limit
(Ib/mmBtu)
0.45
0.50
0.40
0.46
0.68
0.86
0.84
0.80
Total
Number of
Units
135
130
304
312
37
56
31
41
1,046
7 All coverage for boilers > 25 MW unless otherwise noted.
Source: EPA
page 17
-------
Acid Rain Program Annual Progress Report, 2001
Figure 14. Com-
pliance Actions
in the NOX Pro-
gram, 2001
The primary
method of com-
pliance with the
NOX program
was emissions
averaging.
Compliance Option
Standard Emission Limitation
Early Election
Emissions Averaging
Alternative Emission Limitation
TOTAL
Number of Units
140
274
638
27
1,0798
8 The total does not equal 1,046 because 28 units have both early election and emissions averaging
compliance plans, and 5 units have both AELs and emissions averaging plans.
Source: EPA
Compliance
In 2001, 1,045 NOX units met their NOX emissions limits through compliance with
their respective NOX compliance plans. Only one unit failed to meet its NOX emis-
sions limit in 2001. That unit had excess NOX emissions of 60 tons and was
assessed a monetary penalty of $166,440 (60 tons x $2,774 per ton penalty).
Detailed compliance information by unit can be found in Appendices B1 and B2.
These appendices are available on our website at www.epa.gov/airmarkets/
cmprpt/arpOI/index. Figure 14 summarizes the compliance options chosen for
NOX affected units in 2001. Averaging was the most widely chosen compliance
option; 54 averaging plans involving 638 units were in place in 2001.
Geographic Trends in NOX Emissions
Total nitrogen oxide emissions from all NOx affected Acid Rain Program sources
have decreased 25% since 1990. Figure 15 displays bar graphs illustrating rela-
tive state NOX emission trends from power generation sources affected by the
NOX program before the Acid Rain Program (1990), during Phase I (1996-1999
average), and in Phase II (2000-2001 average). NOX emissions reductions since
1999 are due in part to implementation of the OTC NOx Budget Trading Program,
the NOX SIP call, and several state reduction programs as well as the Acid Rain
Program.
Several geographic trends are evident:
The bar graphs illustrate that NOx emissions were lower in 35 states in
2001 compared to 1990 levels, with the greatest reduction occurring in
the Eastern United States;
The shaded states had lower NOX emissions in 2001 compared to both
1990 levels and the 1996-1999 Phase I average. NOX reductions
page 18
-------
Acid Rain Program Annual Progress Report, 2001
page 19
-------
Acid Rain Program Annual Progress Report, 2001
Power Plant NOX Emissions
(thousand tons)
| | 0-50
J 50-150
150 - 250
250 - 350
350 - 450
>450
Phase I Average
Phase II Average
page 20
-------
Acid Rain Program Annual Progress Report, 2001
occurred predominantly in the Northeastern U.S. during Phase I; in
Phase II, NOx reductions are geographically more extensive and occur
in a larger number of Southern and Midwestern states.
In several states, average NOX emissions during Phase I were higher than they
had been in 1990. This is due to the large number of Phase II sources in these
states that were not required to control NOX emissions until 2000. In the 2000-
2001 period (Phase II) emissions in these states have declined to levels below
what was emitted in 1990. There are also several states where average Phase II
NOX emissions were higher than emissions in 1990 and/or the Phase I average.
This is because while the Acid Rain Program limits the rate at which coal-fired
power plants may emit NOx, it does not limit total emissions of NOX the way total
emissions of SO2 are limited. Since heat input (or fuel use) increased in those
states, overall NOX emissions also increased.
As illustrated in Figure 16, in 1990, the highest NOx emissions occurred in the
Midwestern and Southern regions of the U.S. By 2001, emissions in many of
these states had been significantly reduced from 1990 levels. The states with the
highest emissions in 1990 (Ohio, Texas, and Pennsylvania), achieved an average
reduction of 40% (38%, 31%, and 52%, respectively) in 2001. Other states in the
region are showing similar trends since 1990. NOX emissions decreased 27% in
Indiana, 33% in Kentucky, 34% in Tennessee, and 39% in West Virginia.
page 21
-------
onitoring Results
The Acid Rain Program relies on several types of monitoring to implement
and assess the effectiveness of Title IV. Each affected source is required
to install and maintain Continuous Emissions Monitoring Systems (GEMS)
or approved compatible alternatives to accurately measure the amount of SO2
and NOX emitted. The Acid Rain Program also assesses the results of the emis-
sions reductions by collaborating with other organizations to measure acid depo-
sition nationwide. Wet acid deposition is monitored by the National Atmospheric
Deposition Program (NADP). Dry deposition is monitored by the Clean Air Status
and Trends Network (CASTNet). The impacts of acid deposition on lakes and
streams are monitored by the Long-Term Monitoring (LTM) and Temporally-Inte-
grated Monitoring of Ecosystems (TIME) ecological monitoring programs.
Emissions Monitoring
Emissions monitoring is necessary in order to verify the reductions of SO2 and
NOX emissions mandated under the Act and to support the SO2 allowance trad-
ing program. A fundamental objective of the Acid Rain Program is to ensure con-
sistent and accurate accounting of emissions from all affected boilers and tur-
bines. To implement this objective, concentrations and mass emissions of SO2
and NOX from each affected unit are measured and recorded using Continuous
Emissions Monitoring Systems (CEMS) or an approved alternate measurement
method and reported to EPA on a quarterly basis. Daily, quarterly, and annual
quality assurance (QA) tests must be performed by each source to ensure that its
monitors continuously meet the high accuracy standards of the Acid Rain Pro-
gram.
SO2 mass emissions are determined using CEMS to measure SO2 concentration
and stack gas flow rate. NOx mass emissions are determined by coupling NOx
concentration data with flow, diluent (i.e., CO2 or O2) concentrations, or fuel feed
rates. Whatever method is selected, all monitors are required to meet strict initial
and on-going performance standards to demonstrate the accuracy, precision, and
timeliness of their measurement capabilities. The monitors used in the Acid Rain
Program have achieved an unparalleled level of performance with respect to all
of these criteria.
One measure of the accuracy of a CEMS is the relative accuracy test audit
(RATA), which is required for initial certification of a CEMS and on at least an
annual basis thereafter. The RATA ensures that the installed monitor measures
the "true" value of a pollutant by comparing the monitor to a reference method
which simultaneously measures the stack gas pollutant. All monitoring systems
page 22
-------
Acid Rain Program Annual Progress Report, 2001
must meet a relative accuracy standard allowing no more than ten percent devi-
ation from the true value in order to continue to be used for emissions reporting.
Further, if the CEMS is biased low compared to the true value, a bias adjustment
factor must be applied to all future data from that monitoring system to ensure
there is no underreporting. This "self correcting" provision, coupled with daily
quality assurance testing requirements, creates a strong disincentive to allowing
any deterioration in monitor performance.
In 2001, data submitted on monitoring systems indicate that over 96% of the SO2
concentration monitors and 99% of all flow monitors met this relative accuracy
standard. In fact, most sources achieved much better results as the median rel-
ative accuracies for all of these monitors were 3% and 2.5%, respectively.
Air Quality and Deposition in 2001
The Acid Rain Program also works with many partners to monitor the effects of
emissions changes on air quality, deposition of pollutants, and water quality. The
National Atmospheric Deposition Program (NADP) is a nationwide network of pre-
cipitation monitoring sites designed to measure regional levels of atmospheric
deposition. The network is a consortium of many different groups, including uni-
versities, state, local and federal government agencies, and other interested part-
ners. The NADP National Trends Network (NADP-NTN) measures wet acid dep-
osition (deposition that occurs in rain, snow, or sleet) weekly at about 250 moni-
toring stations throughout the U.S. The data are subject to strict quality assurance
isi
Figure 19. Loca-
tion of NADP/NTN
and CASTNet
Deposition Moni-
toring Sites, 2001
NADP/NTN has
monitoring sites
throughout the
country; CASTNet
is concentrated in
the East and has
not yet completed
its expansion into
the Great Plains
and Western
states.
Source: NADP and CASTNet
page 23
-------
Acid Rain Program Annual Progress Report, 2001
and completeness screening in the field, in the laboratory, and during analysis. All
NADP data can be accessed online from the NADP website at
http://nadp.sws.uiuc.edu/. The Clean Air Status and Trends Network (CASTNet)
is a nationwide network of over 70 sites that measures ambient air concentrations
of pollutants, including ozone. CASTNet also measures dry deposition (the
process through which particles and gases are deposited in the absence of pre-
cipitation) of acidic compounds. CASTNet data are also subject to strict quality
assurance and completeness criteria. Figure 19 displays a map of the NADP-NTN
and CASTNet deposition monitoring sites (the dots on the maps in Figures 20, 21,
and 22 also indicate the location of monitoring sites). All CASTNet data can be
accessed online from the CASTNet website at http://www.epa.gov/castnet.
Figure 20 shows the sulfate (SO42-) concentrations (a primary component of fine
particles in the Eastern U.S.) in the atmosphere. Concentrations are highest in the
Midwest, mid-Atlantic, and parts of the South. Figure 21 shows the wet sulfate
and total (wet and dry) sulfur deposition in the continental U.S. during 2001. Wet
sulfate deposition is highest in the Midwest. Total sulfur deposition is highest in
the Eastern U.S. Most sites in the Eastern U.S. have a dry/wet ratio of about 1:1,
meaning that wet and dry deposition make up roughly equal portions of the total
deposition amount. In general, dry deposition is a larger percentage of total dep-
osition in those areas nearest to SO2 emission sources.
Figure 20. East-
ern Regional Air
Quality, 2001:
Sulfate Concen-
trations
The highest
regional concen-
trations of sul-
fate (SO42-) in the
atmosphere are
in or downwind
of the areas
where SO2 emis-
sions are high-
Source: CASTNet
Notes:
1) Data are presented for
the Eastern U.S. only
because there are not
enough. CASTNet monitor-
ing sites in the West to
support this type of analy-
sis.
2) The dots on the map
represent the locations of
monitoring sites.
3) Map colors represent
relative concentrations and
do not imply ecological or
human health status.
page 24
-------
Acid Rain Program Annual Progress Report, 2001
Wet Sulfate Deposition
^ • — « J' w l-fr
C <3c'^r
Notes:
1) The dots on the map represent
the locations of monitoring sites.
2) Map colors represent relative
concentrations and do not imply
ecological or human health status.
Source: NADP
Figure 21. Sulfur
Deposition,
2001: Wet Sul-
fate and Total
Sulfur Deposi-
tion
The highest lev-
els of wet sul-
fate (SO42-) dep-
osition are in
the areas where
emissions are
highest and in
areas down-
Total Sulfur Deposition
e '
-
i
Total 5 (kg/ha)
20
•0
2.5
Source: CASTNet
Note: The size of the "pies" indicates the total magni-
tude of deposition; the colors indicate the percentage
of wet and dry deposition.
Wet and dry sul-
fur (S) deposi-
tion make up
roughly the
same percent-
age of total sul-
fur deposition in
the Midwest; in
most other
areas wet depo-
sition makes up
a greater per-
centage of the
page 25
-------
Acid Rain Program Annual Progress Report, 2001
Figure 22. 2001
Nitrogen Deposi-
tion: Wet and
Total Nitrogen
Deposition
The highest lev-
els of wet nitro-
gen (N) deposi-
tion are in the
Midwest and in
agricultural
areas in the
Great Plains.
Wet Nitrogen Deposition
Notes:
1) The dots on the map represent
the locations of monitoring sites.
2) Map colors represent relative
concentrations and do not imply
ecological or human health status
Source: NADP
Total Nitrogen Deposition
Wet deposition
makes up most
of the total depo-
sition load at
most of the mon-
itoring sites in
the Eastern U.S.;
in southern Cali-
fornia dry depo-
sition makes up
a greater per-
centage of the
Total N (kg/ha)
15
10
2.6
:
DryN
WetN
Source: CASTNet
Note: The size of the "pies" indicates the total magni-
tude of deposition; the colors indicate the percentage
of wet and dry deposition.
page 26
-------
Acid Rain Program Annual Progress Report, 2001
Figure 22 shows the wet and total (wet plus dry) nitrogen (N) deposition in the
continental U.S. during 2001. Wet nitrogen deposition is highest in the Midwest
and in heavily agricultural areas of the Plains. Total nitrogen deposition is highest
in the Eastern U.S., although several monitoring stations in the West also show
relatively high levels of total nitrogen deposition. As is the case with sulfur, dry
deposition of nitrogen makes up a larger part of the total amount of deposition in
those areas nearest to the sources of NOx emissions. In some areas of southern
California, for example, the ratio of dry to wet deposition is approximately 4:1.
Clean Air Mapping and Analysis Program (C-MAP)
EPA has developed a mapping and analysis tool that can help users conduct
assessments of regional and national environmental changes. C-MAP takes
advantage of geographic mapping techniques to assess the environmental ben-
efits of sulfur dioxide and nitrogen oxide emission reduction programs, including
the Acid Rain Program. Using a Geographic Information System (GIS), C-MAP
allows users to view a series of national and regional maps in the "Map Gallery"
section, and then download the data used to generate the maps in the "GIS Data
Download" section. The maps display information showing how changes in
emissions result in changes in air quality indicators, acid deposition, and sensi-
tive ecosystems. The GIS database provides an extensive inventory of nation-
al/regional level emissions, environmental effects, and demographic data avail-
able for download, including air quality, surface water quality, acid deposition,
forest health, and sensitive ecosystem data. The data behind many of the graph-
ics in this Progress Report, as well as many of the graphics themselves, are
available for download and analysis at http://www.epa.gov/airmarkets/cmap.
Freshwater Monitoring
The Temporally Integrated Monitoring of Ecosystems (TIME) and Long-Term
Monitoring (LTM) projects were initiated in the early 1990s by EPA's Office of
Research and Development to determine whether emissions reductions have had
the intended effect of reducing acidity in the environment. Currently all the
TIME/LTM sites are in the Northeast and mid-Atlantic (see Figure 23); additional
sites in acid sensitive regions of the Southeast and West would make more com-
plete assessments possible. TIME/LTM measures a variety of important chemical
characteristics in a regional population of lakes and streams, including acid neu-
tralizing capacity, pH, sulfate, nitrate, several cations (e.g., calcium and magne-
sium), and aluminum. Its central objectives are to detect trends of these charac-
teristics in regional populations of lakes or streams.
TIME/LTM utilizes a hybrid sampling design. Lakes or streams in the TIME net-
work are measured annually; the results from these sites are used to infer region-
al changes in chronic acidification. The LTM sites are a non-random group of
lakes or streams sampled on a frequent schedule (8-16 times per year) in order
to characterize both long-term (over years) and short-term (over weeks) variation
in their acid-base chemistry. LTM sites have been chosen to represent the sub-
populations of lakes and streams most sensitive to acidic deposition effects.
page 27
-------
Acid Rain Program Annual Progress Report, 2001
Researchers use these data to model the episodic behavior of the sites, so that
the models can be applied to TIME data. This approach allows the proportion of
lakes and streams that undergo episodic acidification (short-term highly acidic
pulses) to be estimated as an adjunct to the information on chronic acidification
provided by the TIME results. Data collected in this network is used to assess
trends in acidification and recovery as shown in Figure 29.
Figure 23. Loca-
tion of TIME/LTM
Surface Water
Monitoring Sites
Long-term moni-
toring sites for
acid rain are
critical to
assess whether
lakes and
streams are
recovering from
acidification.
Source: EPA
page 28
-------
E
nvironmental
Improvement and Trends
The emission reductions achieved under the Acid Rain Program have led to
important environmental and public health benefits. These include
improvements in air quality with significant benefits to human health,
reductions in acid deposition, the beginnings of recovery in surface waters,
improvements in visibility, and less damage to forests, coastal waters, and mate-
rials and structures.
Improved Air Quality and Reduced Acid Deposition
To evaluate the impact of emissions reductions on the environment, scientists and
policymakers use data collected from long-term national monitoring networks
such as NADP and CASTNet. Deposition and air quality monitoring data from
these and other air quality monitoring networks, such as the Interagency Moni-
toring of PROtected Visual Environments (IMPROVE) and the State/Local/Nation-
al Air Monitoring Stations, can be accessed on or through the CASTNet website
at http://www.epa.gov/castnet.
Data collected from these networks show that the decline in SO2 emissions from
the power industry has decreased acidic deposition and improved air quality. The
decline in NOx emissions has not been as large and the environmental improve-
ments are not as widespread.
Analyses of CASTNet data show that concentrations of SO2 in the atmosphere
have decreased up to 8 micrograms per cubic meter (ug/m3' in the Northeast and
mid-Atlantic from 10-20 ug/m3 in 1990 (see Figure 24). These reductions are pri-
marily due to the significant decrease in SO2 emissions from power plants under
the Acid Rain Program.
Sulfate concentrations in the atmosphere, a primary component of fine particulate
matter in the East, have also decreased significantly since 1990 (see Figure 25).
Sulfate concentrations have decreased up to 3 ug/m3 in most of the Eastern
U.S. from levels of 5-8 ug/m3 in 1990. These reductions are also primarily due
to the significant decrease in SO2 emissions from power plants under the Acid
Rain Program.
Wet sulfate deposition has decreased more than 8 kilograms/hectare (kg/ha; 1
kg/ha is equivalent to 0.89 pounds/acre) from 30-40 kg/ha/year in 1990 in much
page 29
-------
Acid Rain Program Annual Progress Report, 2001
Figure 24.
Trends in Sul-
fur: Average
Yearly Sulfur
Dioxide Concen-
trations, 1989-91
vs. 1999-2001
Sulfur dioxide
(SO2) concentra-
tions have
decreased sub-
stantially in
most of the Mid-
west and North-
east since 1989-
Sulfur Dioxide Concentration
Average of 1989-1991
Sulfur Dioxide Concentration
Average of 1999-2001
12
14
It
18
>20
Source: CASTNet
Notes:
1) Data is presented for
the Eastern U.S. only
because there are not
enough CASTNet moni-
toring sites in the West to
support this type of
analysis.
2) Map colors represent
relative concentrations
and do not imply ecologi-
cal or human health sta-
tus.
page 30
-------
Acid Rain Program Annual Progress Report, 2001
Sulfate Concentration
Average of 1989-1991
Sulfate Concentration
Average of 1999-2001
Source: CASTNet
Notes:
1) Data is presented for
the Eastern U.S. only
because there are not
enough CASTNet moni-
toring sites in the West to
support this type of
analysis.
2) Map colors represent
relative concentrations
and do not imply ecologi-
cal or human health sta-
tus.
Figure 25.
Trends in Sul-
fur: Average
Yearly Sulfate
Concentrations,
1989-91 vs.
1999-2001
Sulfate (S042-)
concentrations
in air, a primary
component of
fine particles in
the East, have
decreased sub-
stantially in
most of the East
since 1989-1991.
page 31
-------
Acid Rain Program Annual Progress Report, 2001
Figure 26.
Trends in Sul-
fur: Average
Yearly Wet Sul-
fate Deposition,
1989-91 vs.
1999-2001
Wet sulfate
(SO42-) deposi-
tion has
decreased sub-
stantially
throughout the
Midwest and
Northeast since
1989-1991.
Wet Sulfate Deposition
Average of 1989-1991
Wet SO42-
Wet Sulfate Deposition
Average of 1999-2001
Wet SO4?
-30
M36
L>4Q
Source: NADP Note: Map colors represent relative concentrations and do not imply ecological or
human health status.
page 32
-------
Acid Rain Program Annual Progress Report, 2001
Wet Nitrogen Deposition
Average of 1989-1991
Wet Nitrogen Deposition
Average of 1999-2001
•
-3
-4
-5
-5
Figure 27.
Trends in Nitro-
gen: Average
Yearly Wet
Nitrogen Depo-
sition and Nitric
Acid Concentra-
tions, 1989-91
vs. 1999-2001
Nitrogen (N)
deposition
decreased
slightly in areas
of the Eastern
U.S. since 1990;
increases
occurred in
areas with sig-
nificant agricul-
tural activity
(e.g., the Plains
and coastal
North Carolina).
-> 10
Source: NADP Note: Map colors represent relative concentrations and do not imply ecological or
human health status.
page 33
-------
Acid Rain Program Annual Progress Report, 2001
of the Ohio River Valley and Northeastern U.S. (see Figure 26). The greatest
reductions have occurred in the mid-Appalachian region. Important reductions
have also occurred in the Northeast, portions of the southern Appalachians, and
the Midwest.
There have been no dramatic regional changes in wet nitrate deposition (see Fig-
ure 27). This reflects the fact that total nitrogen emissions from sources other than
power plants (e.g., automobiles, trucks, non-road vehicles, and agricultural activ-
ities) have increased since 1990. Wet nitrate deposition has in fact increased up
to 3 kg/ha in many areas since 1990. These increases occurred in the Plains and
eastern North Carolina, where there is significant agricultural activity, and in
southern California where motor vehicles are the predominant source of
emissions.
Visibility
In the atmosphere, SO2 and NOX gases are transformed into fine particles of sul-
fates and nitrates. Sulfate and nitrate particles scatter and absorb light, impairing
visibility and contributing to haze. In the East, sulfate particles account for more
than 50 percent of visibility impairment. The haziest days in the East reduce the
visual range to 20-24 km (12-15 miles). The visual range under naturally-occur-
ring conditions is 128-144 km (77-86 miles).
The Interagency Monitoring of PROtected Visual Environments (IMPROVE) net-
work monitors visibility in the nation's national parks and wilderness areas. From
1992-1999, visibility in the ten eastern Class I area trend sites improved 1.5
Figure 28. Trends
in Visibility in the
Eastern U.S.
Class 1 Areas
Although visibili-
ty has only
improved slightly
in the Eastern
U.S. since the
early 1990s,
significant visi-
bility benefits are
expected when
the Acid Rain
Program is fully
implemented.
30
25
15
10
5
n
A Worst Visibility
-*• * A A A ,
Mid-Range
Best Visibility
92 93 94 95 96 97 98 99
Year
Worst visibility range is 20-24 km
Mid-range visibility is 44-50 km
Best visibility range is 83-94 km
Source: Latest Findings on National Air Quality: 2000 Status and Trends, EPA 2001
page 34
-------
Acid Rain Program Annual Progress Report, 2001
deciviews since 1992 on the haziest days (see Figure 28). A deciview is a meas-
ure of human perception of visibility; an improvement of 1 deciview is a percepti-
ble change. On typical days in the East, visibility improved 1 deciview since 1992.
Visibility in the East is still significantly impaired in national parks and wilderness
areas, especially on the haziest days. Further reductions in fine particle concen-
trations will be necessary to restore visibility to natural levels.
Human Health Benefits
SO2 and NOx emissions react in the atmosphere to form fine particles and ozone.
These gases and fine particles are associated with a number of significant health
effects in sensitive populations. High SO2 concentrations can result in temporary
breathing impairments in sensitive populations, including asthmatics and those
who are active outdoors. A large number of epidemiological studies over the past
10-20 years show an association between ambient fine particle concentrations
and health effects, such as increased numbers of hospital admissions and emer-
gency room visits for heart and lung disease, increased incidences of respiratory
disease and symptoms (such as asthma), decreased lung function, and even pre-
mature death. Children, the elderly, and individuals with existing cardiovascular or
lung conditions, such as asthma, are especially vulnerable to the effects of parti-
cles. The Acid Rain Program has reduced the amount of fine particles in the air
(see Figure 25) by lowering SO2 and NOX emissions, achieving significant human
health benefits nationwide. It is expected that the Acid Rain Program will achieve
further benefits as SO2 emissions continue to decrease to the level of the cap.
NOX emissions react with volatile organic compound gases in the atmosphere in
the presence of sunlight to form ozone. The scientific literature shows associa-
tions between ozone and a number of effects on the respiratory system, including
aggravation of asthma, increased susceptibility to respiratory illnesses like pneu-
monia and bronchitis, and permanent lung damage. Children, the elderly, people
with existing respiratory problems, and those exercising or working outside during
the ozone season are most vulnerable to the health effects of ozone. Additional
health benefits have been achieved under the Acid Rain Program due to NOx
reductions that reduce ozone concentrations.
Ecological Effects of Reduced Acid Deposition
Freshwater
Acid deposition causes acidification of surface waters. In the 1980s, acid rain was
found to be the dominant cause of acidification in 75% of the acidic lakes and
50% of acidic streams. Areas especially sensitive to acidification include portions
of the Northeast (particularly Maine and the Adirondack and Catskill Mountains)
and Southeastern streams. Some high elevation Western lakes, particularly in the
Rocky Mountains, have become acidic, especially during snowmelt. However,
although many Western lakes and streams are sensitive to acidification, they are
not subject to continuously high levels of acid deposition and so have not become
chronically acidified.
page 35
-------
Acid Rain Program Annual Progress Report, 2001
Whether surface waters can resist acidification depends on the ability of the water
and watershed soil to neutralize the acid deposition it receives. This quality, called
Acid Neutralizing Capacity (ANC), depends largely on the watershed's physical
characteristics such as geology, soils, and size. Waters that are sensitive to acid-
ification tend to be located in small watersheds that have few alkaline minerals
and shallow soils. Conversely, watersheds that contain alkaline minerals, such as
limestone, tend to have waters with a high ANC.
As acidity increases, aluminum leached from the soil flows into lakes and streams
and can be toxic to aquatic species. The lower pH levels and higher aluminum
levels that result from acidification can make it difficult for fish and other aquatic
species to grow, reproduce, and survive. In some waters, the number of species
of fish able to survive has been directly correlated to water acidity. Acidification
can also decrease fish population density and individual fish size.
Figure 29 indicates that since the beginning of the Acid Rain Program, sulfate
concentrations in lakes and streams have declined significantly in all monitored
regions of the Eastern United States, except Virginia. The type of soils present in
Figure 29.
Trends in Acidity
of Sensitive
Waters, 1990-
2000
In Pennsylvania
and the Adiron-
dacks, acid neu-
tralizing capaci-
ty (ANC) has
begun to
increase, an
indication of the
beginning of
recovery.
decreasing
concentrations
increasing
concentrations
sulfate
nitrate
ANC
base cations
-1012
Slope of Trend
* = not significant
Maine lakes (n=11)
Vermont lakes (n=11)
Adirondack lakes (n=50)
Catskill streams (n=4)
Pennsylvania streams (n=5)
Virginia streams (n=74)
Source: Recovery of Surface Water Chemistry in the Northern and Eastern U.S.: Effectiveness of the
Clean Air Act Amendments of 1990, EPA/620/R-02/004
page 36
-------
Acid Rain Program Annual Progress Report, 2001
Virginia make decreases in sulfate concentrations there unlikely for some time.
Nitrate concentrations have decreased significantly in the Catskills, Adirondacks,
and Vermont since 1990. Recovery, as shown by increasing Acid Neutralizing
Capacity (ANC), is occurring, especially in the Adirondacks and Pennsylvania. In
several regions, including the Adirondacks, recovery has begun in the past few
years (circa 1995). However, levels of base cations, including calcium, magne-
sium, and potassium, are not increasing; in fact, they are decreasing. This reduc-
tion in base cation levels over the same period is believed to slow the onset of
recovery. The sulfate reductions achieved by the Acid Rain Program are project-
ed to spur the recovery of lakes and streams in the East.
In spite of declining sulfate concentrations, some lakes and streams have been
slow to recover. Their recovery is slowed by continuing acid deposition, the pres-
ence of nitrate in surface waters, the loss of the soil's ability to neutralize excess
acidity, the contribution of naturally occurring acid sources, and a lengthy lag time
between deposition reduction and ecosystem recovery.
Full recovery of damaged watersheds will be a lengthy process, especially since
acidic deposition is still occurring, albeit to a lesser extent. Although conditions
would have been worse without the Acid Rain Program, full recovery of some sur-
face waters requires additional reductions in sulfur and nitrogen emissions.
Forests
Acid deposition, especially combined with other pollutants and natural stresses,
can also damage forest ecosystems. Sulfates and nitrates from acid deposition
leach nutrients from forest soils, reducing the forest's capacity to buffer further
acidification and removing elements essential for tree growth. Acidification also
leads to the mobilization of naturally-occurring aluminum, which may interfere
with the uptake of calcium by roots in forest soils. In addition, exposure to tro-
pospheric ozone (a product of NOX emissions) has direct toxic effects on plant
leaves. The combined effects of depletion of soil nutrients, mobilization of alu-
minum, and exposure to ozone make trees more susceptible to drought, temper-
ature extremes, and diseases.
There is currently less stress on forest ecosystems compared to what it would
have been without the Acid Rain Program. The timeframe for full recovery, how-
ever, is uncertain. Leached nutrients must first be restored through weathering of
the bedrock and soilwater aluminum concentrations must be reduced. Even after
soil chemistry is restored, full recovery of sensitive forests is not expected to
occur for decades because of the extensive recovery time of trees and the time
required to re-establish forest floor ecosystems (soil biota, microbes, and roots).
Coastal Waters
The nitrogen component of acid deposition is a significant source of nitrogen to
many estuaries and coastal waters in the Eastern U.S. Excessive nitrogen loads
from a variety of sources, including atmospheric deposition, causes many of
page 37
-------
Acid Rain Program Annual Progress Report, 2001
those estuaries and coastal waters to periodically become eutrophic. Eutrophic
conditions include algal blooms (some of which may be harmful) and low levels of
dissolved oxygen in the water (hypoxia or anoxia) which can stress or kill fish and
shellfish.
The Acid Rain Program has reduced nitrogen deposition in some places com-
pared to what it would have been without Title IV (see Figure 27). However, in
many sensitive coastal waters there has been little or no reduction in nitrogen
deposition since 1990. Additional reductions from the power generation sector, as
well as reductions from other atmospheric sources of nitrogen, such as automo-
biles and trucks, and other land-based sources such as septic systems and urban
runoff, may be needed before coastal waters can recover from eutrophication.
Materials and Structures
SO2, NOX, and many of the pollutants they form can also corrode materials, par-
ticularly those made of limestone or marble. Monuments and historic buildings,
outdoor structures such as bridges and buildings, and automotive paints and fin-
ishes are all susceptible to damage by acidic pollutants. Studies have shown that
air pollution has been responsible for more deterioration of carbonate buildings
and statues than other weathering processes. Structures made of limestone and
marble are particularly sensitive to acidic deposition. Most damage appears to
come from dry deposition. However, in rural areas and in areas where buildings
and monuments remain wet for long periods of time, wet deposition can be a sig-
nificant or primary cause of damage.
Weathering due to acid deposition may harm cultural assets (e.g., statues and
monuments) more than purely operational resources (e.g., bridges and buildings).
This is because the appearance of cultural resources, where much of their value
lies, is particularly vulnerable to damage. There are also historic and emotional
values attached to cultural assets, which increase the value of their preservation.
The Acid Rain Program has reduced the risk of damage to sensitive buildings and
materials by reducing the amount of SO2 and NOX emitted into the atmosphere
and the amount of dry sulfur deposition reaching sensitive structures. Therefore,
on-going monetary costs and cultural losses due to acid gases, particles, and
deposition are also expected to be declining under Title IV.
page 38
-------
s
ummary
The Acid Rain Program continued to be successful in substantially reducing emis-
sions of SO2 and NOX from electric power plants during the second year of Phase
II. Sources continue to close in on the goal of reducing power plant SO2 emissions
from 1980 levels by 50% (8.5 million tons) in 2010 as required by the 1990 Clean
Air Act. Sources have also exceeded the goal of a two million ton reduction in NOx
emissions from projected 2000 levels as required by the 1990 Clean Air Act.
Sources in both the more conventional NOX program and the cap and trade
approach for SO2 have demonstrated a high level of compliance and their efforts
have achieved measurable environmental results. The flexibility for sources inher-
ent in the cap and trade approach has been successful at reducing compliance
costs and has not resulted in any significant geographic shifts in SO2 emissions.
The Acid Rain Program has:
Established and maintained a robust infrastructure to ensure compliance with
the program and expanded our ability to assess its environmental benefits,
including:
4 A sound compliance tracking system;
4 A high quality emissions monitoring system at every source;
4 An expanded national dry deposition monitoring network to com-
plement the nationwide wet deposition monitoring network.
Reduced emissions of SO2 and NC^ substantially from the power generation
sector at a significantly lower cost than expected:
4 In 2001, SO2 emissions were 10.6 million tons, 33% lower than
1990 emissions and 5% lower than 2000 emissions.
4 In 2001, NOX emissions were 4.10 million tons, 25% lower than
1990 emissions and 8% lower than 2000 emissions.
Contributed to measurable improvements in air quality, reductions in deposi-
tion, and recovery of acid-sensitive waters:
4 SO2 concentrations in the atmosphere (a precursor to fine particles
and acid deposition) have decreased since 1990. In 2001, con-
centrations in the Northeast and Mid-Atlantic were 8-12 ug/m3, as
much as 8 ug/m3 lower than in 1990.
4 Sulfate concentrations in the atmosphere (a major component of
fine particles, especially in the East) have decreased since 1990.
In 2001, concentrations in most of the East were 2-3 ug/m3, as
much as 3 ug/m3 lower than in 1990.
page 39
-------
Acid Rain Program Annual Progress Report, 2001
4 Wet sulfate deposition, a major component of acid rain, has also
decreased since 1990. In 2001, deposition in the Northeast and
Midwest was 20-30 kg/ha/yr, as much as 12 kg/ha/yr lower than it
was in 1990.
4 Wet nitrate deposition has not decreased regionally because of the
relatively small NOx reduction from power plants and the large con-
tribution from other sources of NOX.
4 Visibility has improved in the Eastern U.S.
4 Acid neutralizing capacity, a major indicator of recovery in acidified
lakes and streams, is beginning to rise in streams in the Northeast,
including the Adirondacks. This is an indicator that recovery from
acidification is beginning in those areas.
4 Reductions in fine particles due to reductions in emissions of SO2
and NOX are expected to continue to benefit human health by
reducing the incidence of respiratory and cardiovascular illnesses.
For more information on the EPA Acid Rain Program, visit our website at
http://www.epa.gov/airmarkets. For additional detailed emissions data see
http://www. epa.gov/airmarkets/emissions/index.
page 40
-------
F
or Further Information
The following publications are suggested as a starting point for those who want
additional information on any of the topics discussed in this Progress Report.
Additional information on emissions, air quality and deposition trends can be
found at http://www.epa.gov/airtrends and http://www.epa.gov/castnet. Additional
published scientific literature on emissions trading, acid rain, and benefits
assessments can be found at http://www.epa.gov/airmarkets/articles/index.
Emissions and Air Quality
A Ten-Year Spatial and Temporal Trend of Sulfate Across the United States,
Malm, Schichtel, Ames and Gebhart, Journal of Geophysical Research-Atmos-
pheres, in press
Latest Findings on National Air Quality: 2000 Status and Trends, EPA 2001
EPA 454/K-02-001
National Air Quality and Emissions Trends Report, 1999
EPA 454/R-01-004
Environmental Effects of Acid Rain
Acidic Deposition in the Northeastern United States, BioScience 51(3):180-198,
2001
National Acid Precipitation Assessment Program Biennial Report to Congress:
an Integrated Assessment, National Science and Technology Council
Committee on Environment and Natural Resources, 1998
Recovery of Surface Water Chemistry in the Northern and Eastern U.S.: Effec-
tiveness of the Clean Air Act Amendments of 1990, Stoddard, J. L, J. S. Kahl,
F. A. Deviney, D. R. DeWalle, D. C.T., A. T. Herlihy, J. H. Kellogg, P. S. Mur-
doch, J. R. Webb, and K. E. Webster, in press
Health Benefits Assessment
Reanalysis of the Harvard Six Cities Study and the American Cancer Society
Study of Particulate Air Pollution and Mortality; Health Effects Institute, 2000
Air Quality Criteria for Particulate Matter, volumes l-lll, EPA 1996
EPA /600/P-95/001af-cf
Human Health Benefits from Sulfate Reduction Under Title IV of the 1990 Clean
Air Act Amendments, EPA 1995
EPA 430-R-95-010
page 41
-------
-------
-------
Office of Air and Radiation
Clean Air Market Programs
EPA-430-R-02-009
1200 Pennsylvania Ave, NW
(6204N)
Washington, DC 20460
www.epa.gov/airmarkets
November 2002
------- |