docket for this regulatory action: [Please check the appropriate information.] 

(1) A copy of the information that was provided to OIRA for review under the E.O. 

rn (2) Documentation of any substantive changes made to the draft regulatory text that was 

submitted to OIRA when compared with what was subsequently made publicly available. 

The documentation is provided on the pages following this form. Changes made at the 

suggestion or recommendation of OIRA, if any, are clearly identified through attribution to 

OIRA. EPA has used one or more of the following methods to note changes: [Select the 

appropriate option(s).] 

(a) Redline-Strikeout -A copy of the draft regulatory action submitted, using redlinestrikeout to show the substantive changes that were made. 

g (b) Hand Markup - A copy of the draft regulatory action submitted, using handwritten notes 

to show the substantive changes that were made. 

(c) Note to the file - A document that identifies the substantive changes that were made, 

with page and paragraph references to the draft regulatory action that was submitted. 

If you have any questions about this regulatory action or this documentation, please call the 

contact: r-- -. -- - - - - - . . - - . . --- . - - . - - . , -. - . - . . - . . . . -. . -. . . 

Name: iLynorae Benjamin 1 Email: penjamin.lynoraerI Phone: b04-562-9040 

L - - . J . - - - .- - . . ... ..z -. . . -. . . . . - .- .* . .. . . -- .. 

Revised 05/05/2010 
Documentation of Changes Made During E.O. 12866 – Review for Alabama Visible Emissions Rulemaking 

February 10, 2011 

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Part 52 

[EPA-R04-OAR-2005-AL-0002-201047; FRL- ] 

Approval and Promulgation of Implementation Plans: 

Alabama: Final Disapproval of Revisions to the Visible Emissions Rule 

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

SUMMARY: EPA is taking final action to amend an October 15, 2008, final rulemaking on two 

State Implementation Plan (SIP) revisions regarding the State of Alabama’s rules for visible 

emissions from certain stationary sources. EPA has now determined upon reconsideration that 

Alabama’s SIP revisions, dated September 11, 2003, and August 22, 2008, are not approvable 

pursuant to the Clean Air Act (CAA or Act) section 110(l). Accordingly, EPA is disapproving 

the two SIP revisions provided to EPA by the State of Alabama, through the Alabama 

Department of Environmental Management (ADEM), dated September 11, 2003 and August 22, 

2008 (Submittals). No further action is required by Alabama because the SIP revisions were not 

required by the CAA. As a result of this action, Alabama’s visible emissions rule that was in the 

SIP prior to the October 15, 2008, final action will be the “current” SIP-approved rule as of the 

effective date of this action. EPA urges Alabama to undertake rulemaking that will bring its 

State-effective rule into conformance with its SIP-approved rule. 
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February 10, 2011 

2 

EFFECTIVE DATE: This rule will be effective [insert 30 days after date of publication in the 

Federal Register]. 

ADDRESSES: EPA has established a docket for this action under Docket Identification No. 

EPA-R04-OAR-2005-AL-0002. All documents in the docket are listed on the 

www.regulations.gov index. Although listed in the index, some information is not publicly 

available, i.e., Confidential Business Information (CBI) or other information whose disclosure is 

restricted by statute. Certain other material, such as copyrighted material, is not placed on the 

Internet and will be publicly available only in hard copy form. Publicly available docket 

materials are available either electronically through www.regulations.gov or in hard copy at the 

Regulatory Development Section, Air Planning Branch, Air, Pesticides and Toxics Management 

Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth Street, SW, Atlanta, 

Georgia 30303-8960. EPA requests that, if at all possible, you contact the person listed in the 

FOR FURTHER INFORMATION CONTACT section to schedule your inspection. The 

Regional Office’s official hours of business are Monday through Friday, 8:30 to 4:30, excluding 

federal holidays. 

FOR FURTHER INFORMATION CONTACT: Ms. Lynorae Benjamin, Chief, Regulatory 

Development Section, Air Planning Branch, Air, Pesticides and Toxics Management Division, 

Region 4, U.S. Environmental Protection Agency, 61 Forsyth Street, SW, Atlanta, Georgia 

30303-8960. The telephone number is (404) 562-9040. Ms. Benjamin can also be reached via 
Documentation of Changes Made During E.O. 12866 – Review for Alabama Visible Emissions Rulemaking 

February 10, 2011 

3 

electronic mail at benjamin.lynorae@epa.gov. 

SUPPLEMENTARY INFORMATION:

Table of Contents 

I. What is the Background for this Action? 

II. What Action is EPA Taking and What is EPA’s Rationale for Disapproving the 

Submittals? 

III. Response to Comments 

IV. Final Action 

V. Statutory and Executive Order Reviews 

I. What is the Background for this Action? 

This action follows three key EPA actions regarding Alabama’s request for approval of 

the two visible emissions SIP revisions. The first was an October 15, 2008, final rule (73 FR 

60957) approving revisions to the Alabama SIP embodied in two submittals dated September 11, 

2003, and August 22, 2008 (Submittals). The second was an April 3, 2009, action granting a 

February 25, 2009, petition for reconsideration on the October 15, 2008, final action which had 

approved the SIP revisions. The third was an October 2, 2009, proposed rule (74 FR 50930) 

identifying two alternative options being considered by EPA as part of the reconsideration 

process (the alternative proposals were either to affirm the October 15, 2008, rulemaking, 

thereby approving Alabama’s Submittals or to amend the October 15, 2008, rulemaking, thereby 

disapproving Alabama’s Submittals). EPA has now determined that Alabama’s Submittals are 
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February 10, 2011 

4 

not approvable pursuant to CAA section 110(l). Detailed background information for this action 

is available in the proposed rulemaking published on October 2, 2009. 74 FR 50930. 

In relevant but brief part, on September 11, 2003, ADEM submitted a voluntary1 request 

for EPA approval of a SIP revision (2003 Submittal) containing proposed revisions to the 

existing EPA-approved visible emissions portion of the Alabama SIP, found at Alabama 

Administrative Code (AAC) 335-3-4-.01, “Visible Emissions,” and pertaining to sources of 

particulate matter (PM) emissions.2

 In an action published on April 12, 2007 (72 FR 18428), 

EPA proposed to approve the 2003 Submittal contingent upon the State of Alabama submitting a 

revised SIP submittal addressing EPA’s concerns regarding impacts of the rule changes on 

attainment of the National Ambient Air Quality Standards (NAAQS), as set forth in 72 FR 

18428-18434. EPA’s proposal notice explained that the State would have to provide EPA with a 

revised SIP submittal consistent with certain changes described by EPA in the April 12, 2007, 

notice of proposed rulemaking before EPA could approve the revisions. The proposal notice 

also described EPA’s rationale for requesting the additional submittal. Specifically, EPA noted 

that the 2003 Submittal was not approvable because the revision “would allow a source to emit at 

a higher allowable average opacity percent level (as measured by a COMS – Continuous Opacity 

Monitoring System – in six-minute increments) on a quarterly basis as well as allowing higher 

short term excursions than the current approved SIP allows.” 72 FR at 18430/3. EPA further 

explained that “in the absence of a supporting demonstration of compliance with the CAA 

 

1

 The request was “voluntary” because it was not specifically required by the CAA or its implementing regulations, 

rather, ADEM chose to revise its rules and submit the SIP revision. 2

 PM with particles with having an aerodynamic diameter equivalent of 10 microns or less than or equal to a 

nominal 10 micrometers is are referred to as PM10; PM with particles with having an aerodynamic diameter 

equivalent of 2.5 microns or less than or equal to a nominal 2.5 micrometers is are referred to as PM2.5. As a general 

matter, the term “PM” refers to particulate matter of unspecified size range and includes both PM10 and PM2.5. 
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5 

requirements from the State, we believe that the 2003 SIP submittal is not approvable as 

submitted.” Id. 

 On August 22, 2008, Alabama, through ADEM, provided EPA with an amended 

submittal (2008 Submittal). After further evaluation, EPA determined that it could approve the 

Submittals (i.e., the 2003 Submittal as amended by the 2008 Submittal). On October 15, 2008, 

EPA took final action to incorporate into the Alabama SIP, the revisions to Alabama’s visible 

emissions rule included in the Submittals. 73 FR 60957. EPA’s rationale for its approval is 

discussed in that final action. In order to approve the Submittals in 2008, EPA relied on two 

main findings: “(1) the revision would not increase the allowable average opacity levels; and (2) 

the relationship between changes in opacity and increases or decreases in ambient PM2.5 levels 

cannot be quantified readily for the sources subject to this SIP revision, and 

is particularly uncertain for short-term analyses.” 73 FR 60959/2. The October 15, 2008, final 

action was effective on November 14, 2008 (by its terms, the Alabama rule change became 

effective, and thus applicable to sources, on May 14, 2009). 

 Following the October 2008 final action, EPA received two petitions for reconsideration 

submitted on behalf of the Alabama Environmental Council (AEC) and other parties 

(Petitioners), one on December 12, 2008, and one on February 25, 2009. EPA considered these 

petitions under section 553(e) of the Administrative Procedures Act (APA) and the CAA. The 

first petition for reconsideration raised procedural and substantive concerns with EPA’s October 

15, 2008, final action.3

 EPA denied the December 12, 2008, petition via letter on January 15, 

 

3

 The Petitioners raised eight main issues: (1) EPA was arbitrary and capricious in failing to reopen the public 

comment period when ADEM made changes to the rule after the close of the public comment period; (2) EPA was 
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6 

2009. The second petition incorporated by reference the issues raised in the first petition and 

also identified additional substantive and procedural concerns not included in the first petition.4 

EPA granted the Petitioners’ second request for reconsideration of the October 15, 2008, final 

action via letter on April 3, 2009. In that letter, EPA explained that it anticipated initiating a new 

rulemaking process to provide additional opportunities for public comment. 

 On December 12, 2008, Petitioners filed a lawsuit in the Eleventh Circuit Court of 

Appeals challenging EPA’s October 15, 2008, final action. EPA and the appellants subsequently 

jointly stayed the litigation pending the conclusion of EPA’s reconsideration process. EPA’s 

October 2, 2009, proposed rule was EPA’s initiation of a new rulemaking process to reconsider 

its prior action on the Submittals. In that proposal, EPA articulated two alternative options and 

sought public comment on both. One option was to affirm the October 15, 2008, final action 

(thus approving the Submittals) and the other was to amend the October 15, 2008, final action 

(thus disapproving the Submittals). The bases for each alternative were described in detail in the 

October 2, 2009, proposed rulemaking. 74 FR at 50932-50934. The responses to the comments 

 arbitrary and capricious in deviating from rulemaking policy regarding documentation of post-comment period 

meetings between EPA and ADEM and failing to meet with Petitioners in addition to ADEM; (3) EPA was arbitrary 

and capricious in proposing to approve a SIP revision before the rule had even been developed at the State level; (4) 

EPA failed to comply with rulemaking procedures by failing to complete the docket prior to finalizing the 

rulemaking package; (5) The rule should not have been approved because it does not represent reasonably available 

control technology requirements for SIPs because Alabama has nonattainment areas for PM2.5; (6) EPA’s approval 

of the rule is not consistent with either Section 110(l) or 193 of the CAA due to likely increases in short-term 

particulate matter emissions; (7) EPA’s final action is not consistent with EPA policies on excess emissions and 

director’s discretion; and (8) The final rule does not comply with 40 CFR Part 51 because it is not an “appropriate” 

visible emission limitation. 

4

 The Petitioners specifically highlighted two new issues: (1) the DC Circuit’s decision in Sierra Club v. EPA, 551 

F.3d 1019 (D.C. Cir. 2008) (SSM MACT decision) made the Agency’s action on the SIP revision untenable; and (2) 

new documents added to the docket show that throughout the consideration of this matter, EPA acted in an arbitrary 

and duplicitous manner in failing to re-notice the rulemaking for public comment given the differences between 

what EPA required of Alabama in the April 12, 2007, proposal and what Alabama actually submitted for approval in 

its August 22, 2008, submittal. 
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7 

EPA received on the October 2, 2009, proposed action are summarized in section III of this 

rulemaking. 

II. What Action is EPA Taking and What is EPA’s Rationale for Disapproving the 

Submittals? 

EPA is now taking final action to amend its October 15, 2008, final action and to 

disapprove Alabama’s 2003 and 2008 SIP Submittals regarding its visible emissions rule. As 

EPA explained in its October 2, 2009, proposed rulemaking, the primary issue for resolution is 

whether approval of the Submittals is consistent with the requirements of the CAA, specifically, 

the requirements of section 110(l). If the approval were appropriate under section 110(l), EPA 

would need to consider whether it would also meet the requirements of section 193, given that 

the visible emissions rules in question were in effect prior to November 15, 1990, and apply to 

some sources that are located in areas designated nonattainment for one or more NAAQS. In 

light of the fact that this SIP revision would apply statewide, including nonattainment areas, EPA 

has concluded that it cannot approve the SIP revision under section 110(l) if it would worsen air 

quality by allowing increased emissions of criteria pollutants or precursors to such criteria 

pollutants. In particular, if the revision would result in increases in emissions of pollutants for 

which an area is designated nonattainment, specifically PM2.5, EPA considersbelieves that 

allowing increased emissions of such pollutants would interfere with the area’s ability to attain 
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8 

the NAAQS.5

 See, e.g., 70 FR 53 (January 3, 2005); 70 FR 28429 (May 18, 2005) (previous 

rulemaking actions addressing section 110(l)). 

In this particular circumstance, the analysis of whether the Submittals satisfy the CAA is 

made more difficult by the uncertainty in the precise relationship between the opacity of a stack 

emission stream and the mass of PM in the same emission stream at the affected sources. After 

consideration of all the issues raised by the Petitioners in their February 2009 petition for 

reconsideration, as well as comments received on the October 2, 2009, proposed rulemaking 

from many industry groups, individual companies, state agencies, and other non-governmental 

organizations, EPA has concluded that disapproving the 2003 and 2008 Submittals results in the 

interpretation of the CAA that is most consistent with the plain text and legislative history of the 

CAA, as well as the air quality goals set forth in the CAA. What follows is EPA’s explanation 

of its analysis, which involves a discussion of the following: (1) the role of visible emissions in 

NAAQS attainment and maintenance; (2) the history of Alabama’s visible emissions rule; (3) 

consideration of CAA section 110(l); (4) comparison of the original rule to the revised SIPapproved rule; (5) the role of uncertainty in EPA’s analysis; and (6) the types of information that 

would be particularly useful in developing a visible emissions SIP revision.

1. Role of Visible Emissions in NAAQS Attainment and Maintenance 

 

5

 With respect to attainment areas, section 110(l) requires that an approvable SIP revision not interfere with 

maintenance of the NAAQS or any other requirement of the CAA. In some circumstances, allowing increases in 

criteria pollutants may not interfere with maintenance of the NAAQS. EPA has not analyzed whether this SIP 

revision would be approvable with respect to attainment areas only because the Submittals included rules that 

applied throughout Alabama, which includes both attainment and nonattainment areas, and the State did not make a 

showing that emissions from such sources would not interfere with maintenance of the NAAQS in attainment areas 

and with attainment of the NAAQS in nearby nonattainment areas. Similarly, EPA is not basing this decision on 

section 193 because the Submittals are not approvable under section 110(l); however, section 193 would have to be 

addressed before EPA could consider approval of the revisions.
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9 

Opacity may be defined as the degree to which emissions reduce the transmission of light 

and obscure the view of an object in the background. 40 CFR 60.2. Opacity is important 

because it provides information regarding pollutants visible to the eye leaving an emissions 

source. In general, the more that opaque particles that pass through an emissions point, the more 

light will be blocked, thus increasing the opacity percentage. However, variables such as the 

size, number, and composition of the particles in the emissions can result in variations in the 

percentage of opacity. 

Historically, visible emissions have been an important tool for implementation of PM 

NAAQS and, in particular, for the implementation and enforcement of PM limits on sources to 

help attain the NAAQS. Visible emissions have been a useful tool to indicate overall operation 

and maintenance (O & M) of a facility and its emissions control devices even before modern 

instruments that measure PM on a direct, continuous basis existed. The observation of greater 

than normal visible emissions, particularly on a recurring basis, has served as an indication that 

incomplete combustion or other changes to the process and/or the control device had or were 

occurring; such changes frequently led to increased PM emissions. Although opacity is not a 

criteria pollutant, opacity standards continue to be used as an indicator of the effectiveness of 

emission controls for PM emissions, or to assist with implementation and enforcement of PM 

emission standards for purposes of attaining PM NAAQS. Opacity EPA believes that opacity 

measurements can serve as an indicator of a well-maintained, well-operated source and that such 

sources should be able to achieve visible emissions that comply with opacity limits. For 

example, data submitted by one commenter show routine source operation with opacity of about 
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10 

five percent.6

 Conversely, visible emissions at much higher percentages (such as those allowed 

by Alabama’s revised rules), particularly on a recurring basis, may indicate that a source is in 

violation of applicable SIP or permit mass limits as well. 

Many commenters agreed that the precise relationship between opacity and PM 

emissions was uncertain. Despite this uncertainty, EPA also believes that there is a general 

relationship between opacity and particulate matter mass emissions. As a result, increases in 

opacity can be indicative of changes in emissions control device performance or source 

operation, which in turn can lead to increases in mass emissions. 

Furthermore, based on the information contained in the record for this action and a 

general lack of opacity and corresponding PM emissions data received to date, it is apparent that 

EPA believes that changes in the mass of emissions based on short-term increases in opacity 

cannot be quantified readily for each of the 19 sources affected by the SIP revisions in the 

Alabama Submittals.7 There are several contributors to the uncertainties associated with relating 

mass emissions to increases in opacity, including: (1) differences between combustion 

technology characteristics and fuel components; (2) differences in control technology types, 

temperatures at which they operate, and load characteristics; (3) the recognition that both opacity 

and mass emissions are subject to significant variability over short periods of time and 

 

6

 Alabama Power Company in Attachment T from the docket shows that over a three-year period its units did not 

exceed 5 percent opacity for 55.4 percent of the operating time, 10 percent opacity for 89 percent of the operating 

time, and 15 percent opacity for 97.6 percent of the operating time. In addition, the U.S. District Court for the 

Northern District of Alabama found in 2009 that at TVA’s Plant Colbert, Units 1-4 typical baseline opacity 

measured about 5-8 percent during normal unit operation, and Unit 5 was projected to operate below 5 percent 

opacity even with a partially malfunctioning control device and below 10 percent “under extreme conditions that are 

unlikely to ever occur.” Sierra Club v. TVA, 592 F. Supp. 2d 1357, 1367 (N.D. AL 2009). 7

 EPA specifically requested that commenters provide any available concurrent data showing the PM mass 

emissions and opacity for sources affected by the SIP revision at issue, but no commenter supplied this information. 

74 FR 50934. 
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fluctuations such that one may act independently of the other; and (4) differences between the 

mass of particles that exists at the point of opacity measurement by the COMS (e.g., in the stack) 

and the direct PM2.5 that forms immediately upon exiting the stack (that are related to fuel 

components more than to control technology). 

2. History of Alabama’s Visible Emissions Rule 

 EPA first approved Alabama’s visible emissions rules into the Alabama SIP in 1972. 37 

FR 10842, 10847 (May 31, 1972). The State submitted the visible emissions rules as part of its 

SIP for attainment and maintenance of the total suspended particulates (TSP) NAAQS (the 

predecessor to the PM NAAQS). The State has revised these rules three times in support of 

those goals. 

Historically, Alabama has had areas with attainment problems for the various PM 

NAAQS. Originally, EPA designated some areas in Alabama as nonattainment for the TSP 

NAAQS. In 1987, EPA replaced the TSP NAAQS with the PM10 NAAQS, and all areas of 

Alabama were designated as attainment for those NAAQS. 56 FR 11101 and 58 FR 67734. All 

areas of Alabama remain designated attainment for the PM10 NAAQS. In 1997, EPA 

promulgated new annual and 24-hour particulate matter NAAQS, using PM2.5 as the indicator. 

Effective April 5, 2005, EPA designated portions of Alabama, in the Birmingham and 

Chattanooga areas, as nonattainment for the 1997 PM2.5 NAAQS. 70 FR 944. In 2006, EPA 

promulgated new PM2.5 NAAQS, significantly tightening the 24-hour standards. Effective 

December 14, 2009, the Birmingham area was designated nonattainment for the 24-hour PM2.5

NAAQS, as revised in 2006. The Birmingham area remains designated as nonattainment for 

both the 2006 24-hour and 1997 annual PM2.5 NAAQS. Chattanooga remains designated as 
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12 

nonattainment for the 1997 annual PM2.5 NAAQS. Alabama’s visible emissions rules continue 

to be a part of the Alabama SIP for attainment and maintenance of the PM NAAQS. 

The SIP revision at issue affects the applicable visible emissions limits at approximately 

19 stationary source facilities.8 These 19 facilities include older coal-fired utilities, cement 

manufacturing facilities, and pulp and paper facilities, among others. Five of these facilities are 

located in or near nonattainment areas for the current PM2.5 NAAQS. Specifically, Cheney Lime 

and Cement Company (Allgood), Ernest C. Gaston Electric Generating Plant (Alabama Power 

Company (APC)), and William Crawford Gorgas Electric Generating Plant (APC) are located 

within the Birmingham nonattainment area for the 1997 annual and 2006 24-hour PM2.5

NAAQS; Bowater Incorporated (Westover) is located near that area. In addition, Widows Creek 

Fossil Plant (Tennessee Valley Authority (TVA)) is located in the Chattanooga nonattainment 

area for the 1997 annual PM2.5 NAAQS. Other facilities affected by these visible emissions rules 

may also impact these or other nonattainment areas. 

The geographic location of affected sources covered by the visible emission rules in the 

EPA-approved SIP is relevant. This is because (as is discussed more fully below) EPA interprets 

section 110(l) to prohibit approval of SIP revisions that would increase emissions of pollutants 

for which an area is designated nonattainment, in the absence of offsetting emission reductions 

or an attainment demonstration addressing the rule changes at issue. 

Opacity remains an important tool that states and EPA rely upon in establishing and 

enforcing PM-related standards for SIPs and other standards promulgated under the CAA (such 

 

8

 At this time, it is EPA’s understanding that the rules at issue apply to 19 facilities. Due to the applicability 

portions of the rule, the rule could apply to fewer facilities over time, but will not likely apply to any more.
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13 

as New Source Performance Standards (NSPS) and National Emission Standards for Hazardous 

Air Pollutants). For example, opacity measurements can serve as an indicator for compliance 

with PM emissions between PM stack tests. The Submittals would provide sources with the 

flexibility to allow for visible emissions of up to 100 percent opacity (previous maximum opacity 

was 40 percent) for up to 2.4 consecutive hours per day9 (previous consecutive maximum time 

for “exempt” periods per day was 6 minutes). This change, like all SIP revisions, must be 

consistent with section 110(l). 

3. Consideration of CAA Section 110(l)10

In considering whether to approve the SIP revision at issue in this action, EPA must 

evaluate the changes embodied in the Submittals from the State in light of the requirements of 

section 110(l). Section 110(l) of the CAA provides, in relevant part, that: 

...The Administrator shall not approve a revision of a plan if the revision would 

interfere with any applicable requirement concerning attainment and reasonable 

further progress (as defined in section 7501 of this title), or any other applicable 

requirement of this chapter. 

Congress added section 110(l) during the 1990 amendments to the CAA as support for 

the cornerstone of the SIP program in the CAA – the attainment and maintenance of the 

NAAQS. 101 Stat. 2404 (101 P.L. 549) (November 15, 1990). The provision was added as part 

 

9

 The Submittals allow up to 2.4 hours per day of operation at opacity levels in excess of 20 percent, provided that 

the total of such periods did not exceed 2 percent of operating time in a quarter, excluding periods of startup, 

shutdown, load change and rate change (or other short intermittent periods upon terms approved by ADEM’s 

Director and included in a State-issued permit).

10 EPA’s evaluation of this SIP revision focused on section 110(l). If EPA were to find the revision approvable 

under section 110(l) it would have to consider other issues raised by the commenters, including whether it is 

approvable under section 193. Further, section 110(l) applies with respect to all NAAQS in effect, even where EPA 

has not yet made designations.
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14 

of general revisions to section 110 to address EPA actions on SIP revisions, in part responding to 

court cases such as a Ninth Circuit Court of Appeals case, Abramowitz v. EPA, 832 F.2d 1071 

(9th Cir. 1987), which discussed Train v. NRDC, 421 US 60 (1975) (both cases addressed EPA 

consideration of SIP revisions in light of some evaluation of whether the revision at issue would 

affect the NAAQS, i.e., the impacts upon attainment or maintenance of the NAAQS). S. Rep. 

No. 101-228 (Report of the Committee on Environment and Public Works, United States Senate) 

(1990 CAA Legis. Hist. 8338, 8360-8363). 

By its plain language, section 110(l) applies to every SIP revision submitted by a state. 

In evaluating whether a given SIP revision would interfere with attainment or maintenance, as 

required by section 110(l), EPA generally considers whether the SIP revision will allow for an 

increase in actual emissions into the air over what is allowed under the existing EPA-approved 

SIP. EPA has not requireddoes not believe that a state must produce a new complete attainment 

demonstration in order to make every revision to its SIP, provided that the status quo air quality 

is preserved. For the Submittals at issue in this action, EPA’s view has been that if the SIP 

revision does not interfere with attainment or maintenance of the NAAQS, then it is unlikely to 

interfere with other applicable requirements. For example, if EPA concludes that emissions of 

PM allowed under the SIP are not increasing as a result of the SIP revision, then no additional 

control requirements would be required under section 193. 

EPA has historically interpreted section 110(l) as requiring the Administrator to have 

some basis on which to conclude that a SIP revision would not interfere with attainment and 

maintenance of the NAAQS, or any other applicable requirement, before EPA could approve the 

SIP revision. EPA has regularly requested such information from the state to support a revision, 
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15 

particularly where there was some uncertainty regarding the impacts of the SIP revision. For 

example, in 2005, the State of North Carolina submitted a SIP revision that raised issues similar 

to the Alabama proposal. After considerable discussion between EPA and North Carolina about 

what revisions would be consistent with the requirements of section 110(l), the State submitted a 

SIP revision that addressed key issues. The rules in the revision retained the same number of 

total minutes and maximum levels of opacity allowed during excursion periods as under the 

revised SIP as under the prior EPA-approved SIP (i.e., the four hourly six minute exceedance 

periods allowed under the existing North Carolina SIP could occur at any time, including 

consecutively, during a 24-hour period, but the allowable maximum opacity levelslevel of 40 

percent during these periods was not increased). In particular, EPA did not adopt an “average 

daily opacity” approach for North Carolina, which would have allowed extended periods of high 

opacity (in excess of 40 percent). See 70 FR 61556 (October 25, 2005). Similarly, EPA has 

proposed to disapprove a visible emissions SIP revision for Ohio in which that state sought to 

relax limitations on the number of occasions of excess opacity per hour, potentially allowing 

entire days with elevated opacity. The revision was submitted without a section 110(l) showing 

that the relaxation in opacity requirements would not reflect increased emissions that would 

interfere with attainment and maintenance of the NAAQS or other requirements of the CAA. 70 

FR 36901 (June 27, 2005). 

EPA recognizes that 110(l) analyses are case-specific and that the scope and nature of the 

analysis will vary, depending on the factual details of the SIP revision at issue. See, e.g., Hall v. 

EPA, 273 F.3d 1146 (9th Cir. 2001) and Kentucky Resources Council, Inc., v. EPA, 467 F.3d 986 

(6th Cir. 2006); see also, 61 FR 16,050, 16,051 (April 11, 1996) (actions on which the Kentucky 
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16 

Resources Council case were based).11 However, in the absence of a full attainment or 

maintenance demonstration, EPA has consistently required a sufficient basis in the record for 

concluding that the SIP revision would not interfere with attainment and maintenance of the 

NAAQS, or any other applicable CAA requirement.12

4. Comparison of the Original Rule to the Revised Rule 

The substantive starting point for evaluating any SIP revision is to consider the 

differences between the current EPA-approved SIP rule and the revised rules being proposed by 

the state in the revision. Many of these differences were highlighted by the Petitioners, and other 

parties during the public comment process on both the April 2007 proposal and the October 2, 

2009, reconsideration proposal. 

In this case, we began our analysis by comparing the rule in effect in the Alabama SIP at 

the time of EPA’s April 2007 proposed action (hereafter “the previous rule”) with the 2003 and 

2008 Submittals (hereafter “the current rule”). Under both rules, the maximum number of 

exempt six- minute periods13 allowed per day is the same—24; the maximum “allowable average 

quarterly opacity”14 is approximately the same—22 percent under the previous rule, and 21.6 

percent under the current rule; and the maximum “allowable average daily opacity” is the same 

 

11 EPA’s action today is consistent with both these 9th and 6th Circuit cases addressing 110(l). 12 As is discussed below, EPA’s previous approval of the Submittals was a departure from this approach. 13 Unless otherwise noted, this notice refers to exempt periods other than those provided by the previous rule for 

startup, shutdown, load change and rate change (or other short intermittent periods upon terms approved by 

ADEM’s Director and included in a State-issued permit), which were part of the existing SIP-approved rule and 

remained unchanged under the October 15, 2008 final action rule. 

14 “Allowable average quarterly opacity” is not a traditional measurement used by states or EPA for monitoring 

opacity or for opacity standard-setting purposes. Rather, EPA first used this approach, which allows sources to 

“average out” periods of very high opacity with periods of lower opacity, in the notice proposing to approve the 

Submittals, if the rules were changed to limit allowable average quarterly opacity. See 72 FR 18432 (providing 

instructions for calculating “allowable average quarterly opacity levels.”) Subsequently, in the notice approving the 

Submittals, EPA also used the concept of “allowable average daily opacity.” 73 FR 60958. 
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under both rules—22 percent.15 However, there are two significant differences16 between the 

previous rule and the current rule. The first is that the current rule allows for maximum visible 

emissions of 100 percent opacity during the exempt periods, while the previous rule allowed for 

maximum visible emissions of only 40 percent opacity during such periods. AAC 335–3–4–

.01(4) (current rule). The second is that the current rule allows exceedances of the 20 percent 

SIP standard for intervals of up to 2.4 consecutive hours (i.e., up to 24 consecutive six-minute 

periods per calendar day), while the previous rule allowed exceedances of the 20 percent SIP 

standard for intervals of only 0.1 consecutive hours (i.e., one six-minute period per hour).17 

Thus, the two key differences are that the current rule allows for opacity to increase up to 100 

percent and allows up to 2.4 consecutive hours of opacity at that level (i.e., the “bundling” of 

high opacity periods) per day. A critical question, therefore, is whether the significant increase 

of the maximum allowable opacity from 40 percent to 100 percent for such extended periods 

could result in more PM emissions were sources to take advantage of the changed limits. 

 In EPA’s original approval notice, we adopted a limited analytical framework for 

addressing this question. We did not conclude that the proposed change in the SIP would not 

result in increased PM emissions. Rather, we established a new metric of “average daily 

opacity” (and “average quarterly opacity”) and concluded that section 110(l) did not prohibit 

approval of a SIP revision that allowed significantly increased opacity levels for longer 

consecutive periods of time because the revision would not increase the allowable average 

 

15 See previous rule AAC 335–3–4–.01(1)(b) and current rule AAC 335–3–4–.01(4) and 335–3–4–.01(5). 

16 One of the technical support documents (TSDs) provided for this action explains in detail the differences between 

the current and prior visible emissions rules. EPA considered all the differences in reaching its decision today. EPA 

is simply identifying two significant differences that are particularly relevant to the analysis of the submittal.

17 See previous rule AAC. 335–3–4–.01(1)(b) and current rule AAC 335–3–4–.01(4). 
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opacity levels (on either a quarterly or daily basis). This analysis was focused on opacity and 

operational conditions regarding opacity as opposed to a focus on the relationship between 

opacity and PM mass emissions, in part because EPA did not have any useful source-specific 

data regarding the relationship between opacity and PM mass emissions at the affected facilities. 

EPA also concluded that the relationship between changes in opacity and increases or 

decreases in ambient PM2.5 levels could cannot be quantified readily for the sources subject to 

the SIP revision, and was is particularly uncertain for short-term analyses and. EPA concluded

that the level of uncertainty about whether increased opacity levels allowed under the revision 

would allow increased mass emissions was sufficiently high that, in the absence of additional 

information to confirm a change in emissions one way or the other, section 110(l) did not 

prohibit approval of the SIP revision. 

 After reconsideration, however, EPA’s position is EPA believes that both of the findings 

that provided the foundation for its initial approval of the SIP revision were not strong enough to 

support approval under the CAA. EPA concludes that, as it was described in the Submittals,does 

not believe the concept of “average daily opacity” is not a useful tool for evaluating whether the 

Submittals are likely to maintain current air quality, particularly given the lack of other 

limitations on opacity exceedances in the Submittals. One of the primary purposes of opacity 

limits is to ensure that PM control devices are operating within normal parameters. Thus, larger 

and longer exceedances of an opacity limit (e.g., 100 percent opacity or other high opacity levels 

over a longer period of time such as 2.4 consecutive hours), which may indicate problems with a 

control device or other significant changes in emissions, are more significant than shorter and 

smaller exceedances. Under the approach of the revised rule, a control device could temporarily 
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shutdown or malfunction, potentially resulting in 100 percent opacity, for an hour or two and the 

source could still be in compliance with the 22 percent average daily limit. By contrast, an 

opacity limit that requires consistent compliance at 20 percent, and allows only one excursion of 

six minutes per hour to 40 percent opacity will limit larger and longer excursions. 

In addition, an opacity limit that requires consistent compliance at 20 percent, and allows 

only one excursion of six minutes per hour to 40 percent opacity helps ensure that sources and 

their control devices are properly maintained, operated, and controlled. In EPA’s experience, a 

source that is properly maintained, operated and controlled should be capable of meeting the 

opacity requirements of the Alabama SIP without this revision. EPA is concerned that the 

allowance of higher levels and longer consecutive durations of opacity exceedances, even with 

an “average daily opacity” cap, would undermine an important purpose of the opacity limit, to 

ensure proper O & M of sources and their control devices. 

After reviewing the issues raised in the petition for reconsideration and additional 

information received during the reconsideration public comment period, EPA concludes that the 

approach utilized to evaluate the Submittals in the October 15, 2008, rulemaking resulted in a 

fundamentally incomplete analysis. Requiring a source to maintain an average daily opacity of 

22 percent does not provide assurance that the source will generally achieve the same level of 

PM control (and emissions) as a source which meets a limit of 20 percent opacity, except for one 

six-minute period per hour at 40 percent. Accordingly, the approach of the prior notice, which 

focused solely on maintaining an overall average daily (and quarterly) opacity does not provide 

an adequate framework for assessing the impact of the Submittals on emissions and air quality, 

which is the touchstone of the analysis required under section 110(l). 
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EPA did receive modeling from a variety of sources (which is discussed in the Response 

to Comments portion of today’s action, beginning with Comment 19) which attempt to show the 

impact on air quality from the changes to the opacity requirements in the Submittals. In addition 

to EPA’s discussion in the Response to Comments section, EPA’s Technical Support Document 

addressing the modeling identifies the information gaps that prevented EPA from conducting the 

type of source-specific analysis that would be necessary for completion of an adequate 110(l) 

evaluation. For example, elements that are missing from the submitted modeling include: data 

from all the sources and source categories affected by the Alabama Submittals; a demonstration 

of the relationship between PM emissions and opacity at a particular facility and sourcecategory; consideration of emissions from other sources in the air shed; condensable PM data; 

explanation for background PM levels used in the evaluation; and an explanation of the use of 

PM10 as a surrogate for PM2.5; among other concerns. As EPA noted in its evaluation of 

modeling submitted during the first comment period:

Although source-specific correlations between opacity and mass emissions can be 

established for some sources, none have been for the sources subject to this SIP revision 

and therefore assumptions must be made about how a change in the opacity rule might 

affect the level of PM mass emissions being modeled. These assumptions made about the 

relationship drive model results and, thus, are important in evaluating the result of the 

modeling exercise.

73 FR 60961. EPA has carefully reviewed all of the modeling submitted and has concluded that 

without source-specific data on the mass-opacity relationship, there is not an adequate basis to 
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model the impact of the revisions to the opacity rules on PM mass emissions. Therefore, the 

models are insufficient and too inaccurate to provide a basis for concluding that the Submittals 

satisfy the requirements of section 110(l). As discussed below, EPA would need additional data 

and information before it could conclude that this approach would not result in an increase of 

nonattainment pollutants that would interfere with attainment and maintenance of the NAAQS.

5. The Role of Uncertainty in EPA’s Analysis 

As was noted earlier, a key issue in evaluating the Submittals is the element of 

uncertainty in the relationship between opacity and PM mass emissions. Many SIP submittals 

involve some level of uncertainty. EPA has never, and does not now, take the position that a 

small possibility that an attainment SIP might turn out not to result in attainment of the NAAQS, 

a violation of the NAAQS, or that a SIP revision might worsen air quality, necessitates denial of 

a SIP revision. EPA recognizes that attainment planning generally requires a high degree of 

technical judgment, and often involves some degree of uncertainty. In EPA’s prior approval, we 

concluded that the level of uncertainty concerning the impact of the SIP revisions on emissions 

of PM from sources was so great that EPA could not make a technical judgment as to whether or 

not approval of the Submittals would likely interfere with attainment and maintenance of the 

NAAQS or any other applicable requirements. In the face of such uncertainty, EPA concluded 

that section 110(l) did not prohibit the approval of the revisions at issue. After reconsideration, 

EPA has concluded that its traditional, and more precautionary, approach to interpreting section 

110(l) is appropriate.

There is a general relationship between opacity and PM emissions such that an increase 

in opacity means the concentration of smaller particles, larger particles, or both, increases. See, 
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e.g., Malm, William C., “Introduction to Visibility,” Cooperative Institute for Research in the 

Atmosphere, May 1999 at Chap. 2, p. 8. However, because increases in the quantity of smaller 

particles may be accompanied by decreases in the quantity of larger particles, and vice versa, 

changes in opacity do not necessarily reflect corresponding changes in the mass of PM 

emissions. While source-specific relationships between opacity and PM emissions may be 

obtained through testing, they can be influenced by a variety of circumstances such as fuel 

compositions and types of equipment malfunction that may occur. Therefore, while changes in 

opacity generally indicate changes in PM emissions, there is uncertainty about quantifying the 

specific level of PM emissions associated with varying levels of opacity. 

 EPA has previously explained the elements of that uncertainty in its proposed 

reconsideration action. 74 FR at 50933. One key element is the recognition that both opacity 

and mass emissions are subject to significant variability of short periods of time and fluctuations 

such that one may act independently of the other. Id. Thus, EPA concludes (and many 

commenters also acknowledged) that there is a relationship between opacity and PM such that 

periods of high opacity can result in increased PM emissions, which in turn can cause or 

contribute to a PM NAAQS violation. We can say with certainty that periods of high opacity 

would cause interference with the PM NAAQS in some circumstances. What EPA does not 

know is precisely when such changes in opacity would cause the interference, particularly for a 

variety of source types. This is the unknown element discussed in detail in EPA’s proposal and 

this final action. 

After reconsideration, EPA has concluded that its traditional, and more precautionary, 

approach to interpreting section 110(l) is appropriate. Section 110(l) was intended to allow SIP 
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revisions in the absence of full attainment demonstrations, but EPA’s view is that Congress 

would not have wanted EPA to approve SIP revisions where EPA lacked not only an attainment 

demonstration but also any basis for concluding that the SIP revision would not interfere with 

attainment or maintenance of the NAAQS, and other applicable requirements. Accordingly, 

consistent with our past practice in considering SIP revisions, EPA concludesbelieves that there 

must be either a contemporaneous attainment demonstration or some other basis for concluding 

that a SIP revision will not interfere with attainment, and that uncertainty alone is not a sufficient 

basis for approving a SIP revision. Moreover, EPA has also concluded, following 

reconsideration, that there is a sufficient likelihood that the SIP revision at issue in this action 

could allow increased mass emissions over what would have been allowed under the previously 

approved SIP rule and that, in the absence of additional information or limitations, the revision is 

not approvable under section 110(l). As noted by commenters during the reconsideration 

process, although a precise correlation between mass emissions and opacity for an individual 

source can be difficult to ascertain, the changes contemplated in the Submittals are such that 

changes in emissions, including increases, are possible under the opacity levels allowed by the 

SIP revision. Given the location of affected sources within nonattainment areas, EPA has 

concluded that additional emissions from such sources would interfere with attainment and 

maintenance of the NAAQS in these areas. 

EPA recognizes that there are circumstances in which a source will record opacity levels 

in excess of a 20 percent standard without necessarily increasing its mass emissions, but there are 

also many circumstances where increased opacity levels are associated with increased mass 

levels. The Submittals would provide sources with the flexibility to allow for visible emissions 
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of up to 100 percent opacity for up to 2.4 consecutive hours per day. The degree of operational 

flexibility associated with the Submittals is such that EPA concludesbelieves that the opacity 

limits in the Submittals are likely overall to allow increased PM emissions. Even though every 

instance of operation at greater than 20 percent opacity may not result in increased emissions, 

and though EPA cannot precisely quantify the effect of approving the Submittals on the 

information in the record, it is reasonably foreseeable that approving the Alabama Submittals 

would allow increased mass emissions, for at least some sources and under at least some 

conditions, over the PM emission levels that would have been allowed under the previously 

approved SIP rule. Given this situation, EPA believes section 110(l) requires disapproval of the 

Submittals absent additional limitations which would significantly diminish the likelihood that 

mass emissions increases will occur. The result of the disapproval is simply that Alabama’s 

previous EPA-approved visible emissions rule will become the federally-enforceable rule in the 

SIP (although EPA urges that Alabama take any regulatory action necessary to avoid having a 

State-effective rule that is different from the SIP-approved rule).

6. Information Regarding Development of Visible Emissions SIP Revisions

 In EPA’s October 2, 2009, reconsideration proposal following reconsideration, EPA 

included a section entitled, “III. What Additional Information Would EPA Like To Receive?”.” 

74 FR 50934. EPA specifically requested information on the nature of the relationship between

opacity and PM mass emissions over both the short and long term and when the opacity and PM 

mass emissions may have a predictable relationship to one another. Id. EPA also requested 

source-specific data from Alabama facilities affected by the Submittals. EPA also included a 

bulleted list of more specific types of information that could assist in conducting an analysis on 
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the impacts of a SIP revision on the air quality of the affected area (i.e., a 110(l) analysis). Id. 

Providing guidance on development of a general visible emissions SIP revision is difficult

because opacity and visible emissions are most easily evaluated in a source-specific context. 

However, states may consider the following information useful.

As a general matter, states may find it instructive to look at visible emissions SIP 

revisions that EPA has approved. An example is the North Carolina approval previously 

referenced in this rulemaking. 70 FR 61556. As was noted earlier in this rulemaking, there are 

two key differences between the North Carolina action and the Alabama Submittals now being 

disapproved. First, the North Carolina action did not allow additional minutes of opacity 

exceptions. Second, the North Carolina action did not change the percentage of opacity allowed 

during the exception periods. 

More generally, EPA expects that providing assurance that a source will comply with a 

rule that allows no more than one 6-minute exceedance per hour and opacity readings no greater 

than 40 percent clearly requires more effective control equipment and/or operating procedures 

than it takes to assure a source will comply with a rule that allows longer consecutive periods of 

exempt opacity excursions and at higher opacity levels. Opacity and PM emissions are related 

closely enough that control equipment effective enough to meet the more stringent opacity 

standard (in terms of the number of consecutive excursions allowed and the level of opacity 

excursions allowed) will also provide a greater level of PM emissions control. Due to the 

importance of first understanding the relationship between opacity and PM emissions at the 

affected sources, source-specific SIP revisions have historically been used by most states in 

developing different visible emissions standards for a source, particularly when those standards 
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are less stringent than existing standards. Source-specific SIP revisions allow for the ability to 

analyze the PM/opacity relationship and establish an appropriate opacity limit that will not 

impact the NAAQS. The technical analysis for such rule changes would likely involve 

collection of parallel mass and opacity data for the source in question. If that information 

indicates that there will be increases in PM mass emissions or opacity, then further analysis 

would be required to ensure that the increased emissions associated with the increased opacity 

(or rule change at issue) will not interfere with attainment, reasonable further progress, or any 

other applicable requirement of the CAA (the 110(l) factors), for that particular source and 

locale. Further, a more definitive modeling assessment of the effect of any proposed rule would 

include representative range of emission rates and/or conditions producing 100 percent opacity 

for each type of source affected by the rule.

When source-specific information is available, the uncertainty about the relationship 

between opacity and mass, and the implication of the changes in opacity on PM emissions, is 

reduced and there may be a basis upon which to make an informed judgment about the impacts 

of the change with respect to section 110(l). Further, source-specific actions are much more 

discrete since they typically apply at a particular unit of a particular facility, thus eliminating the 

need to evaluate the statewide impact of the change. EPA has undertaken source-specific 

opacity revisions. See, e.g., 66 FR 33027 (June 20, 2001) (approving a source-specific revision 

affecting 14 units in Alaska). Similarly, a focus on a particular source category may also allow 

for more specific understanding regarding the relationship between opacity and PM emissions at 

the affected facilities and the rule’s overall impact to air quality. 73 FR 36485 (June 27, 2008) 
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(proposing disapproval of source-category specific revision; notice explains how a sourcecategory revision may be developed). 

EPA is not suggesting that every revision to an opacity standard requires source-specific 

analyses. If a submission provides a sufficient basis for EPA to conclude that changes to a 

visible emissions requirement will not result in increased PM emissions in a nonattainment area 

over what would have been allowed under the previously approved SIP rule (or otherwise 

interfere with any applicable requirement of the CAA), then EPA anticipates that it would be 

approvable under section 110(l). Ultimately, the key issue that must be addressed in any 110(l)

analysis of an opacity SIP revision is an evaluation regarding the impact of that revision on PM 

emissions and the NAAQS. As was noted earlier, because Alabama’s Submittals were voluntary 

revisions to the SIP and not mandated, Alabama has no obligation to develop another visible 

emissions revision.

III. Response to Comments

The following are EPA’s responses to the significant adverse comments on EPA’s 

October 2, 2009, proposal. EPA is obligated to respond to adverse comments received and thus, 

has reviewed the comments that were adverse to a disapproval of the State’s SIP revisions, and 

EPA is now responding to those comments. Many of the comments overlapped or were 

redundant, so in order to assist with readability of the responses, we have organized the 

comments and responses into subject-matter groupings identified below. 

1. Basis for Reconsidering the 2008 Final Action 

2. Relationship Between Opacity and PM Emissions 

3. Modeling 
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4. Relative Stringency of Previous Rule (Pre-2008 Final Action) to Current Rule (Post-2008 

Final Action) 

5. Attainment and Maintenance of the PM NAAQS (PM10 and PM2.5) and Data Submitted 

in Response to October 2009 Reconsideration Proposal 

6. Impact of Uncertainty in these SIP Revisions 

7. Applicability of CAA Sections 110(l) and 193 to this Action 

8. CAA Section 110(l) “Demonstration” of Non-interference with the NAAQS and Other 

Requirements 

9. Use of COMS and Need for Exemptions 

10. Relationship of SIP Revisions to 40 CFR section 51.212 

11. Relationship of SIP Revisions to the Compliance Assurance Monitoring (CAM) Rule 

12. Relationship of SIP Revisions to Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), 

and the Vacatur of Certain Provisions in 40 CFR part 63 

13. Relationship of SIP Revisions to Reasonably Available Control Technology (RACT) 

14. Other Exemptions in the Alabama SIP Related to Visible Emissions 

1. Basis for Reconsidering the 2008 Final Action 

 Comment 1. Commenters argued that because EPA’s October 2, 2009, reconsideration 

proposal notice did not select an option, or at least disclose to the public which option EPA 

preferred, EPA’s interpretation of the relevant CAA provisions and their application to the 

situation here will be entitled to no deference upon judicial review. Also, the commenters 

asserted that their ability to comment on the proposal is hamstrung by EPA’s failure to articulate 
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which option EPA would choose. 

Response 1. EPA does not agree with commenters’ characterization of the October 2, 

2009, proposed rulemaking. That proposal described two alternative actions in detail – including 

the technical, legal, and policy bases for each of the respective actions. EPA provided sufficient 

information for each alternative for commenters to participate meaningfully and for either 

alternative proposal to be finalized, depending upon what additional information was developed 

as a result of the reconsideration. EPA has previously used the alternative proposal option when 

dealing with a particularly complex rulemaking (see, e.g., proposal regarding California-Imperial 

Valley Planning Area, 66 FR 42187 (August 10, 2001)). In this case, EPA’s interest in ensuring 

public comment on the two primary options was best achieved through the alternative proposals. 

There is no indication of any commenter being unable to provide meaningful comments. 

Numerous commenters provided substantive comments on both of the two proposals. The 

substance of the commenters’ own comments reflect that they were on notice of the factual and 

legal issues relevant to the reconsideration. 

 Comment 2. Commenters asserted that there is no new record evidence provided by 

EPA, Petitioners, or other interested parties in order to support the second petition for 

reconsideration of EPA’s approval of the SIP revision in the October 2008 final action. 

Response 2. EPA’s authority to reconsider a SIP rulemaking derives from both the 

Administrative Procedures Act (APA) section 553(e) as well as authority in the CAA. The APA 

provides the opportunity for any person to “petition for the issuance, amendment, or repeal of a 

rule.” 5 USC 553(e). The APA does not explicitly limit this right based on new evidence or any 

other limitations alleged by commenter. Even if there were such a limitation, EPA disagrees that 
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the second petition for reconsideration did not raise issues that warranted reexamination of the 

factual and legal basis for the October 2008 action. 

 Comment 3. Commenters argued that the CAA does not authorize EPA to continue to 

entertain petitions for reconsideration “indefinitely” after a specific CAA process has been 

followed and reconsideration has been denied. According to the commenters, the CAA allows 

EPA to “call” an approved State SIP for legal deficiencies, but does not allow EPA to continue to 

reconsider its actions on a state-submitted SIP revision after the revision is approved. 

Commenters also argued that EPA lacks authority to reverse its approval of the SIP revisions 

because EPA may only change its standard for review of SIP revisions under section 110(l) 

prospectively -- i.e., EPA may only apply an allegedly new reading of section 110(l) to new state 

requests for SIP revision. The commenters further argued that any request for reconsideration of 

a final SIP approval must follow the procedures identified in CAA section 110(k)(5) for seeking 

a change to a previously approved SIP revision (noting that section 307 does not apply and 

section 553(e) of the APA cannot be used to bypass 110(k)). 

Response 3. EPA disagrees with the commenters’ views of EPA’s authority to reconsider 

rulemakings under these circumstances. An administrative agency has the authority to 

reconsider its decisions, unless Congress specifically limits the agency’s discretion to do so. See, 

e.g., Gun South, Inc. v. Brady, 877 F.2d 858, 862 (11th Cir. 1989) (holding that agencies have 

implied authority to reconsider and rectify errors even though the applicable statute and rules do 

not provide expressly for such reconsideration). The D.C. Circuit Court recently affirmed this 

authority in New Jersey v. EPA, 517 F.3d 574 (D.C. Cir. 2008), where it explained that an 

agency normally can change its position and reverse a prior decision but that in the case before it, 
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Congress limited EPA’s ability to remove sources from the list of hazardous air pollutant source 

categories, once listed, by requiring EPA to follow the specific delisting process at CAA section 

112(c)(9). See also, e.g., Trujillo v. General Electric Co., 621 F.2d 1084, 1086 (10th Cir. 1980) 

(“Administrative agencies have an inherent authority to reconsider their own decisions, since the 

power to decide in the first instance carries with it the power to reconsider”). EPA recently 

applied this approach in connection with California conformity SIPs. EPA had approved the 

SIPs based on a mobile source model that was current at the time of EPA’s approval. EPA 

proceeded to update the mobile source model, but under the previous SIP approvals, conformity 

decisions would continue to be made on the basis of those previous SIP approvals, and would not 

take into account the updates to the mobile source model. To remedy this problem, EPA 

conducted a rulemaking that revised the previous SIP approvals so that they were limited to the 

period before States submitted, and EPA found adequate, the mobile source budgets in new SIPs 

based upon the update of the mobile source model. See 74 FR 55292, 55342 (October 27, 2009) 

(discussing EPA’s inherent authority to reconsider SIP actions). See also 73 FR 21528 (August 

22, 2008) (EPA final action on reconsideration of previous Georgia SIP action). 

The commenters questioned EPA’s authority to reconsider a SIP action and appear to 

suggest that EPA’s authority is limited to only a SIP “call” under section 110(k)(5) of the CAA. 

The SIP call process, however, is a distinct and separate authority that Congress has given to 

EPA for use when EPA determines that a current SIP is substantially inadequate to attain or 

maintain compliance with the CAA requirements. See, e.g., Sierra Club v. Georgia Power 

Company, 443 F.3d 1346, 1348 (11th Cir. 2006) (describing the separate revision provisions 

under the CAA and the SIP call process generally). The SIP call process was not intended to be 
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the sole means of revising the SIP and does not displace EPA’s authority to reconsider its 

approval.18 While the two processes may be complementary, the authority to reconsider an 

action and the authority to issue a SIP call are not mutually exclusive, and one or the other may 

be appropriate in different circumstances. 

As the commenters correctly noted, EPA’s approval of a SIP revision is not subject to the 

rulemaking requirements of the CAA section 307(d) because it does not fall within the 

enumerated categories in section 307(d)(1) of the CAA. Section 307(b)(1), to which a SIP 

revision rulemaking is subject, contemplates the “filing of a petition for reconsideration by the 

Administrator of any otherwise final rule or action.” 42 USC 7607(b)(1). Courts have also 

found that EPA must follow the rulemaking requirements of the APA when evaluating a SIP 

submission (see, e.g., Hall, 273 F.3d at 1161), including section 553(e). Finally, the very nature 

of a SIP is that it is not a static document; it is regularly revised to account for new EPA 

standards and new emissions reduction technologies. 42 USC 7410(a)(2)(H). 

Furthermore, EPA notes that the SIP revision at issue did not take effect by its own terms 

until after the date on which EPA granted the second petition for reconsideration. No sources 

affected by the revisions to the Alabama SIP should have been required to alter their facilities or 

their operations in reliance on the prior EPA approval. EPA’s view isEPA believes that a source 

that is properly maintained, operated and controlled should have no difficulty complying with 

either the pre-existing or the revised version of visible emissions rules in the SIP, or even 

complying simultaneously with both versions of the SIP, which suggests that the reconsideration 

 

18 In addition to its SIP call provisions, the CAA also includes provisions for the correction of errors in the SIP. See 

CAA section 110(k)(6). EPA notes that the process it has used for reconsidering and disapproving this SIP revision 

is entirely consistent with the process required under section 110(k)(6).
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process should not have been disruptive for any source. In the present case, EPA concluded that 

reconsideration of its approval of the Submittals was necessary to ensure that the final decision 

was consistent with the plain text and legislative history, and air quality goals of the CAA, given 

the facts at issue in this situation. While the result of EPA’s action today is that Alabama’s 

Submittals are disapproved, the effective date for such disapprovals will be the effective date of 

this final action. Thus, there is nothing retroactive about today’s final action. 

 Comment 4. Commenters argued that if EPA reverses its approval of the Submittals now, 

that would be arbitrary, contrary to EPA’s statutory authority and its responsibility to implement 

the CAA, and in violation of EPA’s “delegation commitment” to Alabama under the CAA. 

Response 4. As a point of clarification, Alabama is authorized to implement certain 

portions of the CAA through its SIP. Commenters do not explain the “delegation commitment” 

reference. Such terminology is inapposite as the majority of CAA programs are “authorized,” 

not “delegated,” particularly with regard to those embodied in a SIP. Some CAA programs, such 

as section 112, are routinely “delegated” by EPA to states; however, section 112 programs are 

not SIP programs. EPA’s responsibility to implement the CAA extends to ensuring that its 

decisions are based in the CAA and its implementing regulations. In the instant action, EPA is 

reversing a previous approval decision because after reconsideration, EPA has concluded that a 

disapproval based on known technical information (as opposed to uncertainty) and an 

interpretation of section 110(l) that is most consistent with the plain text and legislative history 

of the CAA, as well as the air quality goals set forth in the CAA. As was explained above, 

EPA’s reconsideration process is well grounded in statutory authority. 

 Comment 5. Commenters asserted that EPA’s reconsideration proposal notice does not 
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provide any information about the legal authority that the Agency believes justifies its action. 

The commenters further argued that it is incumbent upon the Agency to disclose the legal basis 

upon which it proposes to act and to provide the public with the opportunity to comment on that 

asserted basis, and that without such an explanation from EPA, the October 2, 2009, proposal 

notice is deficient and does not provide an adequate basis upon which the Agency can lawfully 

take action. 

Response 5. EPA does not agree with commenters’ assessment. The October 2, 2009, 

reconsideration proposal includes two alternative options for final action – both based upon 

application of section 110(l) of the CAA. Section 110(l) applies to all SIP revisions and limits 

EPA’s legal authority to approve revisions to existing EPA-approved SIP provisions. The 

reconsideration proposal notice explained the alternative proposed actions as well as the 

interpretation of section 110(l) that would support each of the alternatives. The substance of the 

comments reflects that the commenters were in fact on notice of the factual and legal issues that 

EPA raised for reconsideration. 

 Comment 6. Commenters asserted that certain documents received in response to a 

Freedom of Information Act (FOIA) request do not support the reopening of the public comment 

period. 

Response 6. As was explained earlier, there is no prohibition on EPA’s authority to 

review a final action and allow for a new public comment period on that action. EPA has 

provided the basis of the reconsideration of the October 15, 2008, final rule – the CAA and the 

APA. Whether documents obtained through a FOIA support EPA’s reconsideration, in the 

opinion of the commenter, is not relevant.
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 Comment 7. Commenters asserted that EPA appears to be considering a “policy change” 

in how it interprets and applies section 110(l) in the reconsideration process. Commenters 

argued that if EPA wants the State to amend its approved SIP to reflect revised EPA policy on 

section 110(l), EPA must act under section 110(k)(5) of the CAA and not through a “unilateral” 

notice and comment process. Commenters asserted that they are aware of no other situation 

where EPA has proposed to act in this manner to “withdraw” a final approval of a SIP revision.19

Response 7. EPA’s interpretation of 110(l) that is outlined in this final action is 

consistent with EPA’s historic interpretation of 110(l), the plain text of the CAA, and the 

legislative history of the CAA (as well as court opinions that have considered 110(l)). EPA’s 

decision is based on its re-evaluation of the likelihood that approval of the Submittals will result 

in increases of allowable PM emissions. In amending its previous action, EPA is placing greater 

weight on the technical aspects of the SIP Submittals that are known to have the potential for 

adverse impacts on the NAAQS as a result of allowing greater levels and durations of opacity 

exceedances. This change does not represent a policy shift, but rather, an analytical 

reconsideration of what decision is most supported by the CAA, given the facts at issue in this 

rulemaking. Moreover, EPA’s reconsideration process in this action was far from “unilateral.” 

By reopening the rulemaking for additional public comment, and setting forth the legal, 

technical, and policy bases for that alternative outcomes in the reconsideration process, EPA 

sought to ensure that the public had an opportunity to comment and review the possible options. 

Ironically, if anything, the SIP call process apparently preferred by commenters is more 

 

19 EPA notes APC’s request that should EPA take final acting disapproving Alabama’s SIP revisions, that EPA 

stay its disapproval action pending litigation (APC Comments, pp. 10, footnote 2). EPA is not acting on this request 

through this final action. 
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“unilateral” in that such a process is initiated after EPA has concerns that an existing SIP is 

substantially inadequate and often requires a state to take action to revise its SIP following 

EPA’s final action on the SIP call. Here, EPA’s disapproval will result in a rule coming back 

into effect that was in effect for years. Alabama will not be required to submit a revised SIP 

revision. Further, as explained above, EPA has used the alternative proposal approach in the 

past. While the approach is not appropriate in all regulatory actions, it serves an important 

purpose of seeking public comment in the unusual circumstance in which two potentially 

supportable decisions exist and additional information or input from the public may be helpful to 

EPA in making a final decision. 

 Comment 8. Commenters stated that EPA’s prior analysis of the SIP revision remains 

sound and that there is no basis for reversing the conclusions of that analysis. According to the 

commenters, the rigors of the prior SIP revision process insured that the concerns raised by the 

Petitioners have already been heard and considered by both ADEM and EPA multiple times. 

The commenters argued that the petition for reconsideration raised no issues that were not or 

could not have been raised during the prior rulemaking process. Therefore, the commenters 

argued that reversing the prior approval of Alabama’s Submittals at this point and in this manner 

would not only be an abuse of EPA’s authority under the CAA, it would be the height of 

arbitrary and capricious Agency action. 

Response 8. EPA does not agree with the commenters’ assessment. For the reasons 

described in this final notice, EPA has determined that reconsidering its prior approval and 

seeking additional notice and comment on the factual and legal issues raised by the Petitioners 

was an appropriate action. In reversing its prior approval, EPA has concluded that disapproval is 
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necessary pursuant to the plain text of the CAA, its legislative history, and the air quality goals 

described therein. EPA appreciates that there has been substantial discussion about the merits of 

the Submittals, including various opportunities for public comment. Ultimately, however, when 

weighing alternatives, EPA’s final decision must be the one that is most consistent with the 

CAA, even if that decision is reached through a reconsideration process. EPA has already 

addressed its authority to review the October 15, 2008, final action in response to comments 

above. 

 Comment 9. Commenters asserted that in granting the second petition for reconsideration 

and re-opening the rulemaking for further public comment, EPA ignores the lack of a legal basis 

for reconsideration, its earlier rejection of AEC’s arguments for reconsideration on the merits, 

and its thorough review and technical analysis of the effect of these SIP revisions during the 

earlier rulemaking itself. According to the commenters, reconsidering a SIP approval sets a poor 

precedent and undermines regulatory certainty and the integrity of EPA’s rulemaking processes. 

Response 9. EPA does not agree with commenters’ assessment. To the contrary, the 

reconsideration process has ensured that EPA has left no issue unconsidered in its analysis of the 

Submittals. EPA’s final action on the Submittals, while amended from its previous action, is 

strongly grounded in the CAA, the APA, and sound science. This action furthers the purposes of 

the CAA, is based on the substantive requirements of the CAA, and follows the rulemaking 

requirements of the CAA and the APA. Thus, the action supports regulatory certainty and the 

integrity of SIP process. See, e.g. 73 FR 21528 (August 22, 2008) (EPA reconsideration of 

Georgia SIP action). Indeed, the fact that the CAA and the APA provide bases for reconsidering 

regulatory decisions demonstrates that Congress expected EPA to take necessary action to revise 
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its actions when a party raises factual or legal issues that the Agency findsbelieves justify 

reconsidering such actions. 

 Comment 10. Commenters questioned why EPA granted the petition for reconsideration 

of the approval of Alabama’s Submittal because the Petitioners have provided no new 

information. 

Response 10. As was discussed above, the APA does not restrict EPA’s authority to 

reconsider a rule to a specific record or timeframe. EPA was petitioned for reconsideration of a 

rule and EPA granted that reconsideration because it concluded that the petition raised factual 

and legal issues that justified further evaluation. The second petition for reconsideration raised 

numerous reasons why EPA’s October 15, 2008, final action should be reconsidered, including 

several reasons not identified in the first petition for reconsideration. Thus, commenters’ 

characterization of the second petition for reconsideration as providing no new information is 

also not correct.

2. Relationship Between Opacity and PM Emissions 

 Comment 11. Commenters asserted that data submitted to EPA show that there is no 

reliable or direct correlation between opacity and PM emissions. In addition to several sources 

of uncertainty in the relationship between changes in opacity and increases or decreases in PM2.5

levels cited by EPA in the April 12, 2007, proposal notice, the commenters argued that other 

variables affecting the relationship of opacity and PM mass emissions include stack diameter, 

stack gas temperature, particle density (a function of coal type), and flue gas water vapor content. 

The commenters argued that many, if not most, of these variables are beyond the control of 

source operators. Therefore, the commenters stated that while opacity can serve as an indicator 
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of whether the boiler and related pollution control equipment at a specific source are wellcontrolled and well-operated, changes to opacity of emissions, including changes to the SIP 

limits applicable to opacity in a SIP, cannot be presumed to have any direct effect on ambient 

concentrations of PM. 

Response 11. EPA generally agrees with commenters that there is inherent uncertainty in 

the precise relationship between opacity and ambient concentrations of PM, although we note 

that some variables are less likely to vary during a single source’s operation (as opposed to 

among different sources). EPA also agrees (as a general matter) with commenters’ statements 

that opacity is useful as an indicator of a source’s operations and control technology. Moreover, 

opacity can be a reliable indicator of PM emissions when appropriate source-specific testing is 

carried out and correlations are established for the particular source, operating characteristics, 

and fuel supply. 

EPA disagrees, therefore, that increases in opacity of emissions per se could not reflect 

any increases in mass emissions under any circumstances, in particular in the case of the 

significant increases in the percentage opacity and the duration of excursion time at issue in these 

SIP revisions. This comment highlights the importance of ensuring that the final decision made 

by EPA to approve a SIP revision is based on a reasoned application of that knowledge within 

the confines of the CAA.

 Comment 12. Commenters argued that available data continue to demonstrate there is no 

reliable, generally applicable relationship between opacity and the PM NAAQS. The 

commenters asserted that previous technical studies submitted by APC in the rulemaking 

confirm this lack of correlation. The commenters referred to prior comments for the assertion 
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that: “Because opacity is dependent on so many factors, there is no general relationship between 

opacity and particulate loading.” 

Response 12. EPA agrees that opacity data from different individual sources are very 

specific to the source and to the manner in which it is being operated for the period over which 

data is collected. In other words, source operation affects data produced by the source. Thus, 

EPA and others must consider not only the data on opacity and PM, but also the details regarding 

the facility and its operating characteristics as part of developing an opacity/PM correlation. As 

a result, such data from one facility may be of limited value in extrapolating reliable conclusions 

about emissions from another facility. However, EPA expectsbelieves that sufficiently high 

increases in opacity up to 100 percent for extended periods can represent some impact on PM 

emissions from the sources affected by the rules at issue in the Alabama SIP revisions. As noted 

by comments received through the reconsideration process, although the precise correlation 

between the mass and opacity of emissions may vary, significant increases in opacity to its 

highest measurable level at the same source are likely to result in additional PM emissions from 

that source. Given that several sources are located in and near nonattainment areas, such 

additional emissions are inconsistent with the prohibition of section 110(l) on SIP revisions that 

will interfere with attainment and maintenance of the NAAQS.

 Comment 13. One commenter asserted that EPA’s prior conclusion that greater opacity 

does not necessarily mean greater PM emissions is entirely reasonable. 

Response 13. EPA appreciates commenters’ position on this issue – the uncertainty 

inherent in the relationship between opacity and PM is discussed at length in this final action. 

While EPA agrees that greater opacity does not necessarily (in all circumstances) mean greater 
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PM emissions, EPA does expectbelieve that some periods of greater opacity (particularly of high 

opacity for longer periods of time) are likely in at least some circumstances to be accompanied 

by greater PM emissions. 

 Comment 14. A commenter agreed that it is difficult to accurately characterize 

differences in direct PM2.5 emissions attributable to short-term increases in opacity and further 

commented that: (1) the type of event causing the short-term increase in opacity will most 

probably have an effect on any direct PM2.5 emissions differences associated with the event, and 

(2) based on the cumulative size distribution table in AP-42 (Compilation of Air Pollutant 

Emission Factors), any increase in PM emissions associated with short-term increases in opacity 

would most likely occur in particle sizes larger than direct PM2.5. 

Response 14. Commenter appears to refer to Table 1-1.6, “Cumulative Particle Size 

Distribution and Size-Specific Emission Factors for Dry Bottom Boilers Burning Pulverized 

Bituminous and Subbituminous,” which is found in Chapter 1 of EPA’s AP-42, Compilation of 

Air Pollutant Emission Factors (http://www.epa.gov/ttn/chief/ap42/). This table suggests that 

for units having pollutant emissions controlled by electrostatic precipitators (ESPs), PM2.5

accounts for only 29 percent of total PM emissions. EPA agrees the type of event causing an 

increase in opacity of emissions may have an effect on the size distribution of PM emissions. 

However, EPA disagrees that increases in PM emissions associated with increases in opacity 

would most likely occur in particle sizes larger than 2.5 micrometers in aerodynamic equivalent 

diameter, since the circumstance that causes an opacity increase could occur while a PM control 

device is operating properly, as described by the value contained in the AP-42 table, or while a 

PM control device is not operating properly, a condition not described in the AP-42 table. The 
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uncertainty regarding the impact of opacity increases on PM emissions is further complicated 

because particles approximately 1.0 micrometer in diameter have greater potential for increasing 

opacity than larger particles. See, e.g., Malm, William C., “Introduction to Visibility,” 

Cooperative Institute for Research in the Atmosphere, May 1999 at Chap. 2, p.8. Thus, for the 

increases in opacity contemplated in the SIP revisions at issue in this rulemaking, EPA is 

concerned that this increased opacity would probably include additional particles of the very 

types that would be problematic for purposes of attaining and maintaining the PM2.5 NAAQS.

 Comment 15. Commenters argued that with regard to EPA’s request for additional 

information addressing the relationship between opacity and PM emissions generally, the 

commenter asserted that only the relationship between opacity and direct PM2.5 would be 

relevant to the situation at hand, and that this information would be virtually impossible to obtain 

due to the inclusion of larger particles which are an inevitable part of any effluent gas stream. 

Response 15. EPA agrees that information concerning the relationship between opacity 

and PM2.5 emissions from a facility would be most relevant for purposes of evaluating impacts 

on the PM2.5 NAAQS, but EPA notes that no commenter provided such data, despite EPA’s 

specific request for such specific data. 74 FR 50934 (October 2, 2009). EPA disagrees that this 

information would be virtually impossible to obtain. By way of example, some sources are 

obtaining and reporting these data as part of the current electrical utility maximum available 

control technology (MACT) rule information collection request. Also, under section 110(l) of 

the CAA, EPA may not approve revisions to SIP if the revisions would interfere with any 

applicable requirement concerning attainment and reasonable further progress (RFP), or any 

other applicable requirement of the CAA. Because there are also NAAQS for PM10, states and 
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EPA must also consider potential impacts of increases of larger particles if increased opacity 

were to include the emissions of larger particles from a source as the commenter asserted. For 

110(l) purposes, analysis of a SIP revision must include all of the current NAAQS, to the extent 

that the changes in the SIP revision could affect such NAAQS. With respect to this action, EPA 

has only focused on the potential impacts of the SIP revision on the PM2.5 NAAQS because those 

are the standards that EPA anticipatesbelieves are most implicated by the increases in opacity at 

issue.

 Comment 16. Commenters argued that although an increase in opacity can be a good 

indication that PM emissions at the stack also are increasing, the magnitude of mass emissions 

relative to any one opacity value and the increase in mass emissions relative to increase in 

opacity generally are not quantifiable. Accordingly commenters asserted that an increase in 

opacity would provide no information regarding emission levels of PM2.5, as opposed to PM10 or 

total PM, and argued that any correlation between opacity and PM would have to be source 

specific, and even then, uncertainties remain. The commenters also criticized EPA’s information 

on opacity and PM, noting that the charts included in the docket do not contain sufficient 

information to evaluate the relationship between opacity and PM. 

Response 16. EPA agrees that an increase in opacity can be a good indication that PM 

emissions at the stack also are increasing. It is for this reason that we are disapproving the SIP 

revision embodied in the Submittals, even though the magnitude of mass emissions relative to 

any one opacity value and the increase in mass emissions relative to increase in opacity generally 

are not quantifiable. EPA also agrees with the commenters that a correlation between mass and 

opacity can be derived at a specific source, and EPA has in the past approved SIP revisions 
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allowed reliance on such correlations with sufficient technical analysis. 

EPA disagrees, however, that information about opacity increases provides no 

information regarding PM2.5 emissions specifically. Rather, information about opacity increases 

without concurrent PM2.5 emissions data or an established correlation between opacity and PM2.5

emissions cannot be expected to yield definitive information concerning increases in PM2.5

emissions. The memorandum in the docket, EPA-R04-OAR-2005-AL-0002-0064, provides the 

information known to EPA about the charts referenced by the commenter, EPA-R04-OAR-2005-

AL-0002-0045 and EPA-R04-OAR-2005-AL-0002-0047. Further, the charts provided in the 

docket demonstrate the inherent uncertainty in the relationship between opacity and filterable 

PM mass emissions by showing a range of mass emission rates associated with a single opacity 

value and a range of opacity values associated with a single mass emissions rate. However, 

uncertainty about the precise correlation between mass and opacity as a general matter, does not 

mean that opacity increases never represent concurrent increases in the mass of PM emissions 

from a source. To the contrary, given the large increases in maximum allowable opacity and for 

the periods of time at issue in the SIP revision contemplated in the Submittals, EPA 

expectsbelieves that it is likely that there could be increases in mass emissions. 

Comment 17. Commenter disputed the relationship between opacity and PM mass 

emissions based upon EPA statements in an unrelated rulemaking. The commenter asserted that 

despite providing the option for use of PM continuous emissions monitoring system (CEMS) as a 

compliance method for PM mass limits in revised NSPS Subparts D and Da, EPA also recently 

suggested it had concerns regarding the accuracy of PM CEMS measurements above 0.030 

pounds per million British Thermal unit (lb/mmBtu). As a result, the commenter argued that 
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EPA declined to exempt units operating above that level from the NSPS opacity standard even 

when such sources install PM CEMS. 74 FR 5070 (January 28, 2009). Commenter requested, to 

the extent EPA relies on data from PM CEMS above 0.030 lb/mmBtu in this proceeding, that the 

Agency explain how it resolved those concerns. 

Response 17. EPA disagrees with the commenter’s conclusions regarding PM CEMS 

measurement accuracy above 0.030 lbs/mmBtu. As mentioned in the cited Federal Register

notice, the contribution of filterable PM to opacity at these emission levels (less than 0.030 

lb/mmBtu) is generally negligible, and sources with mass limits at this level or less will operate 

with little or no visible emissions (i.e. less than 5 percent opacity). As a result, EPA 

expectsbelieves that an opacity standard is no longer necessary for such sources because the PM 

mass emission rate standard is substantially tighter, and the use of PM CEMS with continuous 

monitoring of PM emissions is more effective than opacity monitoring in these circumstances. 

This comment is also not germane to today’s action because the SIP revisions at issue did 

not include the requirement that the affected sources install PM CEMS as a precondition to the 

revision of the applicable opacity standard. As noted above, opacity standards serve an 

important role in assuring compliance with PM limits, for example by alerting regulators to 

problems with source operation or control measures that would not otherwise be noted except 

during a stack test for PM emissions, which occur only periodically. In some circumstances, 

opacity is the emission standard that is the subject of an enforcement case. 

Comment 18. A commenter articulated the position that its facilities are operating in 

compliance with PM limits in the title V permits and as a result, the opacity rule is not likely to 

impact PM compliance. The commenter further opined that ADEM should address any PM 
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nonattainment issues separately from this rulemaking. 

Response 18. EPA disagrees with the assessment that opacity is unlikely to have any 

effect on PM emissions for all the reasons explained in this final action regarding that 

relationship. Further, Alabama’s visible emissions rule is a part of Alabama’s plan to attain and 

maintain the PM NAAQS. Even though it has been in the SIP for some time, the rule was 

originally included for that purpose. Thus there is nothing separate about this action and 

Alabama’s PM nonattainment issues – the rule at issue here is part of Alabama’s overall plan to 

address the PM NAAQS. Further, if a source is in compliance with the opacity and PM limits, 

then this disapproval action should have little effect on that source. 

3. Modeling 

 Comment 19. Commenters argued that modeling is not required to demonstrate that 

changes to Alabama’s opacity rule will not implicate the NAAQS. Nonetheless, commenters 

argued that ADEM performed a modeling analysis demonstrating that even earlier versions of 

the SIP revision (predating the Submittals that EPA approved in October 2008) would not 

adversely affect air quality attainment or RFP under very conservative assumptions about the 

relationship between opacity and PM emissions. In addition, commenters argued that updated 

modeling from a consultant, ENSR (now known as AECOM), updated ADEM’s 2003 modeling 

in 2007 using AERMOD (an atmospheric dispersion modeling system and EPA’s preferred 

model since 2005) and confirmed ADEM’s earlier modeling results. Commenters argued that 

APC and TVA have performed subsequent modeling that also supported the conclusion that the 

increased opacity permitted by the SIP revisions in the Submittals would not interfere with 

attainment and maintenance of the NAAQS or other requirement of the CAA. Commenters 
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asserted that these modeling results show no problem with the NAAQS even under unrealistic, 

worst-case conditions. APC also discussed modeling done at APC Plants Barry and Greene and 

TVA Plant Colbert which APC believes supports affirming EPA’s 2008 final action approving 

the Alabama SIP revisions. Commenters further noted that ADEM performed a modeling 

analysis demonstrating that the SIP revisions would not affect air quality attainment under very 

conservative assumptions about a relationship between opacity and PM emissions. According to 

the commenters, modeling performed by TVA confirms that particulate emissions from the 

Colbert facility would not interfere with maintenance of the PM10 or PM2.5 NAAQS, even for the 

unrealistic scenario in which the ESPs are shut down for 10 percent of the time every day of the 

year. 

Response 19. EPA disagrees with the commenter’s assertions. As discussed in 73 FR 

60961 (October 15, 2008), all modeling results are predicated on a known or assumed correlation 

between opacity and PM mass emissions. Because this correlation can differ for each source and 

operating condition, modeling that does not use source-specific correlations does not and cannot 

demonstrate with certainty the impact of changes in opacity on PM NAAQS. With respect to the 

modeling described by the commenters, the models do not demonstrate that the Submittals would 

not interfere with attainment or maintenance of the NAAQS because the models do not appear to 

have included condensable PM or background analyses, to have assessed the impact of nearby 

PM emissions sources, or to have assessed the impact of secondary PM formation. Generally, 

however, the utility of modeling would still be limited because the precise relationship between 

opacity levels and PM mass emissions is not known. The docket for this action includes a 

technical support document (TSD) summarizing the modeling that EPA received and some of the 
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key assumptions and other issues that impacted the utility of the modeling. 

Comment 20. Commenters argued that EPA has routinely approved SIP demonstrations 

based on the use of air models, rightly concluding in such matters that the use of the air models 

leads to a reasonable demonstration of compliance with the NAAQS. 

Response 20. As a general matter, EPA agrees that modeling can be a useful tool in 

appropriate circumstances. In this case, the modeling provided did not reduce uncertainty 

regarding the relationship between opacity and PM emissions sufficiently to support approval of 

the Submittals. Further, the modeling did not conclusively demonstrate that there would be no 

impact on the NAAQS. Thus, EPA could not conclude that the modeling submitted supported 

approval of the Submittals under section 110(l). EPA’s modeling TSD provides more 

information on the modeling submitted to EPA as part of this action. 

Comment 21. Commenters stated that monitoring data show a decline in ambient PM2.5

and PM10 levels at monitors that could potentially be impacted by TVA’s Colbert and Widows 

Creek Plants. 

Response 21. EPA acknowledges that ambient PM levels have been improving in many 

parts of the country as a result of rigorous state and EPA efforts to control emissions from many 

sources of various types. EPA wants to maintain these improvements and to support further 

improvements for protection of public health as many areas are still designated nonattainment for 

the NAAQS. Indeed, this is among the reasons why reviewing SIP revisions pursuant to section 

110(l) is such an important exercise. 

4. Relative Stringency of Previous Rule (Pre-2008 Final Action) to Current Rule (Post 

2008 Final Action) 
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 Comment 22. Commenters argued that Petitioners’ claims regarding “bundling” or other 

potential ways of “using” Alabama’s visible emissions revisions to somehow reduce control 

efforts while still meeting permit requirements are misplaced. According to the commenters, it is 

extremely difficult to achieve continuous or near-continuous compliance with the opacity rules, 

so there is absolutely no incentive to try to “game” the system by trying to achieve less than 

maximum opacity control at any one time. Further, commenters argued that facility procedures 

aimed at minimizing opacity levels at all times in order to avoid non-exempted exceedances 

insofar as practicable remain intact after the rule revisions went into effect January 1, 2009. 

Response 22. The commenters’ argument appears to be that even though “bundling” 

could occur, it will not, because sources are diligently striving to minimize their opacity levels. 

While EPA certainly expects that sources are seeking to minimize their opacity levels, EPA’s 

analysis of the revision considered what the two versions of the Alabama rules allowed – and not 

necessarily how sources were operating under each rule scenario. As with the modeling 

submitted by many commenters, the primary problem associated with their conclusions about the 

amount of PM emissions during longer periods of elevated opacity is the reliance on an assumed 

relationship between opacity and PM emissions that has not been established for the specific 

source. As mentioned previously, this relationship is unknown for each source and operating 

condition, absent sufficient evaluation. EPA disagrees that the “bundling” of periods of high 

opacity could never reflect higher PM mass emissions. 

EPA understands the difficulties associated with operating older facilities, but disagrees 

that continuous compliance with opacity rules can be achieved only through extreme difficulty. 

The Alabama SIP opacity limits in effect following this disapproval should generally be capable 
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of being met by a source that is properly maintained, operated and controlled. ThereEPA 

believes that there are control technologies and operational paradigms that allow older facilities 

to comply with Alabama’s pre-October 15, 2008, opacity rules (this was recognized by the court 

in the TVA Colbert case, Sierra Club v. TVA, 592 F. Supp. 2d 1357 (N.D. Ala. 2009)).. 

 Comment 23. Commenter explained that to attempt to bundle six-minute opacity 

exceedances would necessitate a purposeful “turn-down” of the unit’s ESP and, thus, result in 

non-compliance with two provisions of the commenter’s Lowman Plant’s major source operating 

permit (title V permit): (1) that “all air pollution control devices ...be...operated at all times in a 

manner so as to minimize the emissions of air contaminants,” and (2) once the emissions exceed 

a six-minute average opacity of 20 percent, corrective actions must be taken within two hours. 

Response 23. EPA’s analysis of the SIP revisions at issue is governed by, among other 

provisions, section 110(l) of the CAA. In that context, as was explained previously, EPA must 

compare the existing SIP and the proposed SIP revision. While affected sources may have 

permit limits that are more stringent than the applicable SIP regulations, EPA’s analysis must 

focus on what the SIP itself would allow. Permits may be revised from time to time, depending 

on applicable requirements. As a result, the type of analysis completed by the commenter based 

on the applicable permits might be changed over time. Further, while EPA would, of course, be 

concerned by a purposeful “turn-down” of any control device, EPA expectsbelieves that there are 

other circumstances under which extended periods of consecutive exemptions would allow high 

opacity levels (and mass emissions) that would not occur in a well-operated, well-controlled, and 

well-maintained plant. EPA appreciates PowerSouth Energy Cooperative’s (PSEC’s) analysis, 
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which demonstrates that this disapproval action should have little effect on the vast majority of 

sources. 

 Comment 24. Commenters provided data in three attachments provided by PSEC 

showing emissions during the period of January 1, 2009, thru September 30, 2009, clearly 

indicate that no “bundling” occurred. For example, Attachment 1 shows that of the total of 90 

six-minute periods of excess opacity (i.e., six-minute averages of opacity greater than 20 

percent), including startup/shutdown and load change periods, there were 40 occurrences of 

isolated six-minute periods of excess opacity; 14 occurrences of two consecutive six-minute 

periods of excess opacity; four occurrences of three consecutive six-minute periods of excess 

opacity; one occurrence of four consecutive six-minute periods of excess opacity; and one 

occurrence of six consecutive six-minute periods of excess opacity. 

Response 24. EPA appreciates the submission of operating data. One of the difficulties 

with the technical analysis regarding opacity is that details regarding facility operation can 

impact both opacity and PM in different ways. Further, EPA must consider the effect of the 

Submittals on how a facility may be allowed to operate, not just how the facility actually has 

been operating. With these considerations in mind, the operating data were informative, but not 

determinative, because even if a facility currently operates as the commenters describe, the 

facility would be allowed to operate otherwise under Alabama’s proposed SIP revisions. 

 Comment 25. Commenters suggested that this 22 percent limit ensures that the average 

daily opacity under the revised SIP is no greater than under the previous SIP. The commenters 

asserted that this fully responds to AEC’s hypothesis of the “bundling of high opacity periods” 

and concerns about the elimination of the “40 percent cap” under the revised SIP. Further the 
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commenters explained the use of a daily opacity limit to establish short-term equivalency is 

appropriate because a calendar day is the shortest period over which compliance with the PM 

NAAQS is measured. The commenters stated that AEC provides no supporting data on the 

bundling and operating data provided that demonstrates that bundling has not occurred. 

Response 25. The Commenters’ statements are incomplete. While the 22 percent limit 

does serve the purpose of ensuring subject sources are constrained by the same maximum 

allowable average daily opacity as under the previously approved SIP (as explained in EPA’s 

2008 final notice), these SIP revisions would allow opacity levels of up to 100 percent during 

exempt periods and for multiple consecutive exempt periods, neither of which was previously 

authorized under the SIP. The prior version of the visible emissions rule capped maximum 

opacity at 40 percent and limited the time at such level to only six minutes per hour. Further, 

whether “bundling” in fact has occurred in the past is not the focus of EPA’s analysis for 

purposes of section 110(l).20 As part of this reconsideration, EPA has had to re-evaluate the 

concept of the “22 percent daily cap” supported by the commenter. EPA has concluded that 

even with an “average daily opacity” cap, these SIP revisions undermine the purpose and 

effectiveness of the opacity standard by allowing extended periods of high opacity. Such high 

opacity can be indicative of problems with control device operation or other circumstances 

potentially leading to increased mass emissions. Given that some sources affected by the opacity 

limits at issue in the SIP revisions are located within designated nonattainment areas, EPA 

concludesbelieves that this likelihood of increased emissions renders the Submittals 

 

20 The SIP revisions at issue have been under reconsideration since before the changes to Alabama’s visible 

emissions rule now being disapproved went into effect; thus, the data submitted in public comments may not be a 

representative random sampling of the long-term effects of the rule.
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unapprovable under section 110(l). 

 Comment 26. Commenters argued that the equivalency between the previous and revised 

SIPs, with respect to the short-term and long-term emission rates, will ensure that there will be 

no interference with NAAQS notwithstanding the bundling of high opacity periods. Further, the 

commenters mentioned that in approving the North Carolina SIP revision for visible emissions, 

EPA concluded that such bundling through the “elimination of the current restriction of no more 

than one six minute exception period per hour” does not “pose a problem for purposes of Section 

110(l).” Commenters cite to 70 FR at 61558 for support. 

Response 26. As EPA explained earlier in this final action, the North Carolina opacity 

revisions are not analogous to Alabama’s opacity revisions for the main reason that Alabama’s 

revisions allow for periods of opacity up to 100 percent, whereas the North Carolina revision 

retained the same maximum opacity of 40 percent. The allowance for this high opacity level, 

along with the lengthy time allowed for elevated opacity (up to 2.4 consecutive hours), was not 

present in the North Carolina case. 

 Comment 27. Commenters argued that plant operating data confirm that the bundling of 

high opacity periods does not occur in practice. Further, the 22 percent cap resolves any 

concerns regarding the bundling were it to occur. 

Response 27. EPA appreciates commenters’ information on actual operations; however, 

as explained previously EPA’s analysis under section 110(l) focuses on what the revised SIP 

rules would allow. Further, as discussed above, the 22 percent cap does not resolve EPA’s 

concerns about extended periods of very high opacity.

 Comment 28. Commenters argued that the rule really has nothing to do with air quality, 
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and that if it did, EPA would have to justify and explain why it is proposing to condemn an 

opacity rule that is numerically more stringent and that has fewer exemptions than many other 

states’ opacity rules. 

Response 28. EPA does not agree with commenters’ statements. Alabama’s visible 

emissions rule is part of Alabama’s EPA-approved SIP, and part of its plan to attain and maintain 

the PM NAAQS. As a result, any revision of the EPA-approved opacity rules is subject to 

evaluation under section 110(l) of the CAA. Furthermore, the extended consecutive periods of 

opacity exemptions allowed renders this standard uniquely less stringent than any other EPAapproved opacity rule. 

 Comment 29. Commenters argued that the daily opacity limit is neither necessary for 

approval nor unlawful. According to the commenters, because EPA’s proposed approval was 

not based on a finding that the rule would not allow any more PM during a 24-hour period than 

the old rule, it is not necessary for the daily limit to meet such a criterion. 

Response 29. EPA disagrees that the potential for more PM emissions as a result of 

elevated opacity is not germane to this action. EPA’s prior approval of the SIP revisions was 

based on uncertainty about whether the revisions to the opacity standard would allow more PM 

emissions during a 24-hour period. EPA would not have previously proposed approval if the 

record clearly demonstrated thatit believed the rule would have resulted in increased PM in 

nonattainment areas. After reviewing public comment and the State’s revised submissions, EPA 

based its prior approval in part on the average daily opacity limit included in the revision. At 

that time, EPA accepted certain assumptions, including that believed that the inclusion of the 22 

percent daily opacity limit would serve to lessen the potential for elevated emissions of PM 
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associated with the increases in opacity. Following EPA’s reconsideration and review of 

information submitted to EPA,Given that EPA no longer accepts thatbelieves the average daily 

opacity limit is an appropriate or effective tool for evaluating the impact of the Submittals on PM 

emissions. Given EPA’s position, and given EPA’s decision that there is a sufficient likelihood 

of increased PM emissions associated with the elevated opacity allowed under the SIP revisions, 

EPA no longer believes the Submittals are not approvable under 110(l). 

5. Attainment and Maintenance of the PM NAAQS (PM10 and PM2.5) and Data 

Submitted in Response to October 2009 Reconsideration Proposal 

 Comment 30. Commenter argued that the Clean Air Fine Particle Implementation Rule 

requires that direct PM2.5 emissions be addressed in PM2.5 attainment demonstration SIPs, the 

primary thrust of the regulation is the control of precursor compounds and not direct PM2.5

emissions. According to the commenters, if the Alabama attainment plans are similar to those of 

Tennessee in that sulfates are identified as the main contributor to fine particulate matter and 

reliance is being placed on reductions of sulfur dioxide (SO2) to demonstrate compliance, with 

no measure specified for stationary direct PM2.5, then the Petitioners’ assertion that approval of 

the Alabama SIP revisions would adversely affect PM2.5 attainment or RFP has no merit and 

should be rejected. The commenters explained that if this is the case then the Petitioner’s 

assertion that approval of the Alabama SIP revisions would not be consistent with sections 110(l) 

and 193 of the CAA should also be rejected as having no merit unless it can be demonstrated that 

a fixed source of direct PM2.5 is a significant contributor to a nonattainment area. Additionally, 

according to the commenters, this should be an adequate affirmative demonstration that the 

requirements of sections 110(l) and 193 of the Act are not an issue. Further, the commenters 
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asserted that even for areas achieving conformance with the PM2.5 ambient standard, for which 

no SIP would be required, the effect of the reductions of PM2.5 precursors would be so dominant 

as to negate any changes to direct PM2.5 emissions. 

Response 30. As was explained earlier, given that ADEM did not submit a full 

attainment demonstration specifically addressing this rule and did not propose any offsetting 

reductions to compensate for emission increases in nonattainment areas, EPA’s analysis is 

necessarily focused on the comparison between the previous EPA-approved version of the 

visible emissions rules and the revisions that the State seeks, in order to ensure that the revision 

would not allow an increase in emissions of pollutants that would interfere with attainment or 

maintenance of the NAAQS, or with other requirements of the CAA. A primary consideration, 

therefore, is whether the revisions could result in increases in emissions of a type for which the 

area where the source is located is designated nonattainment. In this context, EPA must evaluate 

the relative stringencies of the two versions of the opacity rules, as was explained earlier. 

EPA notes that the commenter’s arguments here are premised upon what might or might 

not be appropriate in the context of a nonattainment SIP for certain pollutants in an area. EPA 

does not agree that the implementation regulations for the 1997 PM2.5 NAAQS are designed or 

intended to ignore direct PM2.5 emissions from sources, and evaluation of controls for such 

emissions a required element of such a SIP. While it may be correct that a nonattainment SIP in 

a particular area might be designed to focus upon emissions of SO2 and nitrogen oxides, or other 

PM2.5 precursors, as an attainment strategy, it does not follow that emissions of PM2.5 from the 

sources subject to Alabama opacity rule do not impact attainment and maintenance of these 

NAAQS. Considerations mentioned by the commenters might be relevant in the evaluation of 
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the attainment demonstration accompanying a nonattainment SIP for the 1997 PM2.5 NAAQS, 

but they are not relevant in the context of a section 110(l) analysis. 

 Comment 31. Commenters argued that Alabama’s revised SIP for visible emissions is a 

small piece in the overall PM attainment puzzle. According to the commenter, any incremental 

primary PM2.5 emissions increase as a result of revising the SIP, assuming for purposes of 

argument that such an increase occurs, would be an inconsequential contributor to the PM2.5

attainment status against the background of the significantly greater secondary PM2.5 (sulfate and 

nitrate) contributions. The commenter asserted that viewed in this broader context, EPA could 

reasonably conclude, based on the equivalency demonstration, that the revised SIP is consistent 

with the earlier SIP. 

Response 31. The comment fails to appreciate EPA’s limitations in reviewing SIP 

revisions, as described in section 110(l). In addition, EPA did not receive an “equivalency 

demonstration” from ADEM that addressed all the elements in section 110(l). Further, an 

increase of PM emissions by any increment would make it more difficult for areas in Alabama to 

attain and maintain the NAAQS. EPA has considered the SIP as a whole, and concludes that the 

potential increase renders the revisions not approvable. 

 Comment 32. Commenters explained that following new data collected under the current 

SIP confirms that EPA’s prior analysis was sound: 

A. New data collected under the current SIP shows there is no “bundling;” 

B. New data collected under the current SIP shows that daily opacity has improved; and 

C. New data collected under the current SIP shows why the rule makes sense. 

Response 32. EPA appreciates the submission of these data. EPA disagrees, however, 
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with the conclusions that the commenters draw from the data. The commenters’ focus on what is 

actually happening with respect to “bundling” and opacity levels fails to consider what could 

happen under the SIP revision. EPA’s analysis pursuant to section 110(l) must focus on the 

differences between the two versions of the visible emissions rules in terms of what they would 

allow and not on the choices individual facilities may have made to date in terms of opacity and 

PM emissions. Thus, EPA does not agree that the data presented by commenters support 

approval of the Submittals. The commenters did not, unfortunately, submit data to establish 

what the PM mass emissions were during periods of elevated opacity at these sources. 

 Comment 33. Commenter saw no basis for the supposition that Alabama’s opacity rule 

revisions will affect PM NAAQS compliance. The commenterscommnters asserted that as 

indicated in the attachments, PSEC’s Lowman Unit 1’s opacity compliance continues to be very 

good. Additionally, the commenters explained that annual particulate emission testing in 2008 

and 2009 indicate PM emissions well below the standard and show no difference before and after 

the opacity rule revisions. 

Response 33. EPA acknowledges that some facilities affected by the SIP revisions may 

be operating at opacity levels below those required by the Alabama SIP. Indeed, EPA believes a 

source that is well-controlled, well-maintained, and well-operated could achieve opacity levels 

well below 20 percent. However, EPA’s obligation under section 110(l) is to consider how a 

facility could operate under the new rule – not how it typically operates or has historically 

operated. Moreover, EPA notes that annual PM testing offers valuable but limited information 

about mass emissions because the testing occurs only once per year for a limited period of time. 

The question not addressed by the comments is what the PM mass emissions would be, were a 
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source to be operating at the 100 percent opacity for 2.4 hours contemplated by the SIP revision 

at issue. 

 Comment 34. Commenters asserted that there are no new data that would support EPA’s 

withdrawal of its approval of the rule. 

Response 34. As was discussed previously, EPA’s authority to reconsider a SIP revision 

is not limited only to circumstances where there are new data. EPA has already explained in 

today’s action whybelieves its prior approval was not consistent with the purposes of section 

110(l), and that reconsideration and disapproval is appropriate. Notably, , particularly 

considering that the reconsideration was initiated before the revised rule went into effect and that 

sources should be capable of complying with either rule or both rules simultaneously. 

 In addition, EPA disagrees that no new information supports this disapproval. A number 

of commenters have submitted data and information that, while not directly addressing the 

questions that EPA posed, nevertheless help to illustrate the problems with the SIP revisions. 

For example, information submitted by AEC suggests that at least some sources, under some 

conditions, could have increased PM emissions during the longer periods of higher opacity that 

would be permissible under the revised visible emissions rules in the Submittals. See Comment 

Letter from George E. Hays and attachments (on behalf of Alabama Environmental Council, 

among others), Docket No. EPA-R04-OAR-2005-AL-0002-0089.1. Moreover, many of the 

commenters during the reconsideration process submitted comments in which their analysis 

suggested that there is a relationship between PM mass emissions and opacity, even if the precise 

correlation cannot be established without much more rigorous testing and evaluations on a 

source specific basis. See Modeling TSD. As was noted earlier, even some of the commenters 
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opposing EPA’s disapproval action identified the uncertainty in the relationship between opacity 

and PM mass emissions, and the possibility of the SIP revisions resulting in emission increases. 

See, e.g., Comment Letter from Lauren E. Freeman (on behalf of the Utility Air Regulatory 

Group) at 4, Docket No. EPA-R04-OAR-2005-AL-0002-0086.1.

 Comment 35. Commenter noted that with regard to EPA’s request for information on 

condensable PM, COMS do not measure condensable PM, which is in a gaseous form at stack 

conditions. 

Response 35. EPA acknowledges the response, which underscores one component of the 

uncertainty inherent in the relationship between opacity and PM emissions. 

6. Impact of Uncertainty in these SIP Revisions 

Comment 36. Commenters asserted that while EPA has consistently (and correctly) 

noted the uncertain relationship between opacity and PM for short-term analysis, any question 

regarding how this uncertainty might impact PM, in this case, has now been eliminated entirely 

with the addition of the 22 percent daily average requirement. Commenters further stated that 

ADEM’s August 2008 submittal remedied any “uncertainty” question with respect to 24-hour 

PM by including an additional restriction on daily average opacity, so that the average daily 

opacity allowed under the revision is now no greater than under the previous SIP. 

Response 36. EPA has shown through calculations, that the maximum allowable average 

daily opacity under both the previous rule and the revised rule is 22 percent. However, as 

discussed above, the revised visible emissions rule at issue in the SIP revisions would allow 

sources to operate in a manner they could not under the previous rule – including increases in 

opacity concentrations up to 100 percent for an extended period of time. As a result, under the 
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revised rule, sources may now be permitted to cause much more opacity to levels that would 

have been a violation under the previous EPA-approved SIP rules. Such emissions include very 

high concentrations of excess opacity for extended periods. EPA has thus concluded that the 

“average daily opacity” cap provides no assurance against increased mass emissions. Indeed, as 

discussed above, EPA has concluded that there is a sufficient likelihood of increased mass 

emissions under the revisions so as to make it unapprovable under section 110(l). 

 Comment 37. Commenters stated that there is always some uncertainty when attainment 

or interference with a NAAQS is considered in a SIP process because it involves an element of 

prediction and reliance on modeling. Further, commenters explain their positions that section 

110(l) does not require absolute certainty and EPA should not substitute “could” for “would” in 

the 110(l) context. 

Response 37. EPA agrees the Act does not require attainment demonstrations or other 

technical analysis of impacts on attainment or maintenance of the NAAQS to an “absolute 

certainty.” However, to make a determination that the NAAQS will not be adversely impacted, 

EPA must at least be able to reach the conclusion that this is most likely the case. In this action, 

EPA is relying on what is known about the relationship between opacity and PM emissions to 

conclude that the State’s revised visible emissions rules in the Submittals is less stringent than 

the previous EPA-approved rule, and that the likely increases in emissions of PM at affected 

sources would be inconsistent with section 110(l). Under the revised rule, a source could exceed 

its 20 percent opacity limit for well over an hour (up to 100 percent opacity). In contrast, the 

previous SIP-approved rule allowed only one occurrence per hour of a 6-minute average opacity 

above 20 percent (and only up to 40 percent). ControlEPA believes control equipment that is 
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effective enough to avoid a second occurrence of 6-minute average opacity above 20 percent will 

make even the first occurrence an infrequent event. Likewise,EPA also believes control 

equipment and operating procedures that are effective enough to enable a unit to meet the 

requirements of the previous SIP will also allow a lesser quantity of PM emissions than control 

equipment and operating procedures that are sufficient to comply with the current SIP revision 

but do not necessarily enable a unit to comply with the previous SIP rule. 

 In addition, contrary to the commenters’ belief, this is not dependent upon replacing the 

word “would” with the word “could.” EPA’s conclusion is that available evidence indicates that 

some of the affected sources would have increases in PM emissions, and that these emissions 

would occur in locations where such increased emissions would interfere with attainment and 

maintenance of the NAAQS. Commenters evidently misconstrue “uncertainty” about the precise 

amount of such likely emissions increases as evidence that no such increases could occur. 

Comment 38. Commenters raised concerns regarding PM CEMS technology, and the 

representativeness of PM emissions data obtained during Performance Specification (PS) 11 

testing. See 40 CFR part 60, Appx. B. Briefly, the commenters asserted that PS 11 correlation 

testing, which requires disabling of PM control devices under artificial conditions in order to 

obtain sufficient variability in PM emissions to satisfy the PS 11 statistical criteria, rarely 

provide data representative of actual operations or control device malfunctions. Commenters 

also noted that it would not make sense to require sources to spend money to install PM CEMS 

or to perform periodic performance tests in order to develop a source-specific correlation 

between opacity and PM. 

Response 38. EPA disagrees with the commenter’s views regarding PM CEMS 
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technology and PS 11 testing, especially in the context of evaluating the SIP revisions at issue 

here. The procedures of PS 11 are conducted to develop a source-specific PM emissions 

correlation for an individual source operating over a range of PM emissions conditions through 

comparison of results from PM emissions testing and PM CEMS. Note that PS-11 does not 

require PM control devices to be disabled. Those PM measurement and testing correlation 

procedures differ from an opacity and PM emissions correlation, which is the fundamental issue 

requiring resolution for addressing the visible emissions rules revision in Alabama’s Submittals. 

EPA also disagrees that use of PM CEMS or periodic performance testing could be 

“nonsensical” in determining a source-specific correlation between opacity and PM emissions. 

Indeed, as EPA has previously explained, source-specific approaches such as concurrent opacity 

and PM emissions measurements may be one way to determine “...any useful and definitive 

relationships between stack particulate mass emissions values and their corresponding opacity 

levels...” 73 FR 60962 (October 15, 2008). 

 EPA agrees that data obtained over a range of operating and control device conditions 

would be necessary to develop a site-specific correlation between opacity and PM emissions and 

that a single, site-specific correlation should not be extrapolated to other sources. Retaining 

Alabama’s original visible emissions rule (the pre-October 15, 2008, final rule) relieves ADEM 

(and affected sources) from performing an assessment of increased source opacity on PM 

emissions. 

 Comment 39. Commenters suggested that the source-specific nature of the opacity/PM 

relationship does not mean that the uncertain impact of a particular change in an opacity rule can 

be resolved by requiring source-specific testing. 
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Response 39. EPA agrees that a well-designed data collection program should be able to 

reduce to acceptable levels, if not eliminate, most of the uncertainty associated with the 

relationship between PM emissions and opacity resulting from changing opacity limits. 

However, as the commenters themselves argue, the variability in the relationship between PM 

emissions and opacity limits is such that, absent the use of PM CEMS, source specific evaluation 

would be one way to determine the impacts of the change at a given source. EPA through this 

disapproval is not determining that the only means to revise an opacity standard is through 

source by source evaluation, nor is EPA requiring that with today’s action. 

 Comment 40. Commenters argued that to the extent that EPA seeks information on PM 

compliance methods in order to assess the costs of requiring Alabama to impose more sourcespecific PM testing in order to evaluate the impact of its revised opacity rule, commenters 

disagree that such an evaluation is required under CAA 110(l). 

Response 40. EPA agrees that an assessment of the cost of a potential requirement for 

source-specific testing is not necessary pursuant to section 110(l). In order to fully provide the 

public with an opportunity to comment on the proposed action, EPA sought specific information, 

including costs, to assist the public in identifying what information might be useful to EPA. 

EPA has already explained how it considered the SIP revisions and the basis for its final action.

7. Applicability of CAA Sections 110(l) and 193 to this Action 

Comment 41. Commenters stated that because EPA correctly found the revisions would 

not interfere with the attainment or maintenance of the NAAQS or any other requirement of the 

CAA, section 110(l) concerns are not implicated. The commenters stated that as long as a SIP 

revision does not “interfere with” air quality (i.e., make it worse), EPA must approve it. 
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According to the commenter, Alabama’s rule is consistent with the development of an overall 

plan for attainment, in that all of the sources subject to the Rule are also subject to various other 

programs and requirements that EPA has approved to ensure the NAAQS are protected.

Response 41. Commenters’ focus on “air quality” is a good point – and was EPA’s 

primary concern as well. EPA’s action in this case focuses on the known differences between 

the previous EPA-approved SIP rules and the SIP revisions in the Submittals, and what is known 

regarding the technical aspects of the relationship between opacity and PM mass emissions. 

Specifically, that the revised rule allows extended periods of much higher opacity that were not 

previously authorized. EPA has concluded that available evidence indicates that the revised rule 

could result in more emissions, and thus interfere with attainment and maintenance of the 

NAAQS, to use the commenters’ term, “make it worse.” Further, for older facilities (such as the 

ones subject to the visible emissions rule at issue), particularly those that are less controlled, 

opacity can be an important indicator of operation and control device performance, which, in 

turn, can affect air quality. In this context, and lacking reliable scientific correlations between 

opacity emissions and PM NAAQS violations, EPA has concluded that the rule changes 

described in the Submittals are not approvable under section 110(l). 

With respect to the commenters’ argument that other regulatory programs exist to help 

insure attainment and maintenance of the NAAQS, EPA agrees. However, for the sources 

affected by the visible emissions rules at issue, the opacity standards provide an important tool to 

assure compliance with these other measures. The mere existence of a regulatory framework to 
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provide for the attainment of the NAAQS does not negate the need for effective tools to assure 

that the framework succeeds.

Comment 42. Commenters stated that unless ADEM relied upon the opacity standard to 

comply with the PM NAAQS, section 110(l) considerations do not come into play. The 

commenters further stated that in this case, Alabama did not rely on the opacity standard to 

demonstrate attainment of the PM NAAQS. 

Response 42. Alabama’s visible emissions rule is part of Alabama’s plan to attain and 

maintain the NAAQS, and it is in the EPA-approved SIP (and has been for a long time). Any 

revision to the SIP is subject, by the plain text of the CAA, to the requirements of section 110(l).

 Comment 43. Commenters stated that EPA’s October 2008 approval applied and 

satisfied the correct CAA section 110(l) standard. According to the commenters, EPA is not 

required to re-examine the adequacy of the level of reductions provided in a plan that has already 

achieved attainment, or speculate how a requested SIP revision might fit into the mix of controls 

that may be chosen by the state to support a future attainment demonstration with respect to a 

new standard. The commenters argued that EPA’s review under CAA section 110(l) only needs 

to address whether the revision would affect the status quo. EPA could have (and in 

commenters’ view, should have) limited its review to whether the revision interfered with the 

requirement to assess good O&M of PM control equipment between PM stack tests. Further the 

commenters asserted that because Alabama did not rely on a short-term opacity/PM relationship 

to support its previously approved PM attainment demonstration, EPA was not required to 

analyze changes in the opacity standard for equivalency under section 110(l). 
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Response 43. EPA does not agree with commenters’ characterization of EPA’s 

obligation under section 110(l). As a point of clarification, Alabama has several nonattainment 

areas, including PM2.5 nonattainment areas. The State’s visible emissions rule applies to a group 

of stationary sources Statewide – it does not apply only in designated attainment areas. Thus, 

EPA does not agree with commenters’ argument that because Alabama is currently attaining 

some NAAQS, EPA’s consideration under section 110(l) should be different. Further, as was 

noted earlier, in the absence of an attainment demonstration regarding the rules at issue, EPA can 

approve a SIP revision for a nonattainment area only if EPA findsbelieves that it will not worsen 

air quality by increasing emissions of a nonattainment pollutant, and it is otherwise consistent 

with attainment and maintenance of the NAAQS. Even accepting the commenters’ argument 

that the opacity standard is intended to be a gauge of good O &M of a source, the SIP revisions 

contemplated in the Submittals raise concerns because the revisions allow facilities to emit up to 

100 percent opacity for extended periods of time – which is hard to square with the need to 

assure good source operation. Indeed, other commenters have asserted that opacity at such levels 

is the equivalent to turning off any relevant control device for an extended period of time. Even 

under what EPA understands commenters’ argument to be, the SIP revisions present serious 

concerns about good O & M and would not be approvable. 

Comment 44. Commenters explained their view that 110(l) does not impose on states a 

requirement to “demonstrate” that each proposed revision will not interfere with attainment or 

require EPA to reject each revision that presents “some remote possibility for interference.” 

Commenters cited to Kentucky Resources Council (KRC), Inc. v. EPA, 467 F.3d 986, 994-95 (6th
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Cir. 2006) for support. 

Response 44. SectionEPA believes that section 110(l) prohibits any SIP revision that 

would have the effect of interfering with attainment or maintenance of the NAAQS, RFP, or any 

other requirements of the CAA. Typically, states elect to provide the requisite information 

necessary to establish that their intended SIP revisions would not have any of these effects. EPA 

often works with states to evaluate the effects of a given SIP revision. In the final analysis, 

however, EPA is not authorized to approve any SIP revision that has such effects. 

When, as here, available information indicates that the SIP revision at issue could result 

in the increase in PM emissions at some sources located in or near designated PM nonattainment 

areas, EPA has concluded that the SIP revision is not approvable and that residual uncertainty 

about the precise amount of additional PM emissions that would be associated with the dramatic 

increases in opacity does not render the revision approvable. 

Commenters’ citation to KRC, 467 F.3d 986, is misplaced because the case supports 

EPA’s disapproval action. In that case, the Sixth Circuit considered an EPA action approving 

revisions to the Kentucky SIP regarding Kentucky’s inspection and maintenance (I/M) program 

that removed the requirement from the active portion of Kentucky’s SIP. The Court explained 

that Congress did not intend for EPA to “reject each and every SIP revision that presents some 

remote possibility for interference. Thus, where the EPA does not find that a SIP revision would 

interfere with attainment, approval of the revision does not do violence to the statute.” KRC at 

994. The Court upheld EPA’s view that: 

As long as actual emissions in the air are not increased, EPA believes that equivalent (or 

greater) emissions reductions will be acceptable to demonstrate non-interference. EPA 
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does not believe that areas must wait to produce a complete attainment demonstration to 

make any revisions to the SIP, provided the status quo air quality is preserved. 

KRC at 995 (quoting a prior SIP action, 70 FR 28,429, 28,430 (May 18, 2005)). During the 

course of the SIP revision at issue in that case, EPA informed Kentucky of the need to 

demonstrate equivalent offsetting reductions due to the existing nonattainment areas in 

Kentucky. Kentucky responded by adopting additional control requirements into its SIP 

programs which were sufficient to offset the increased emissions anticipated as a result of 

removing the I/M program from the active SIP. This type of equivalency analysis was not 

provided by Alabama and we cannot conclude in this case that the status quo air quality will be 

maintained. Rather, in the case of Alabama, EPA judgesbelieves that there is more than a remote 

possibility for increased emissions under the SIP revision and that our current action is consistent 

with the KRC case. 

Comment 45. Commenters make a distinction between attainment and nonattainment 

areas for purposes of a 110(l) analysis. Commenters appear to suggest that because Alabama had 

no outstanding nonattainment plans due in the time frame of the October 15, 2008, final rule, that 

the 110(l) analysis should address whether the revision would affect the status quo. 

Response 45. EPA agrees that the 110(l) analysis for a nonattainment area should, in the 

absence of an attainment demonstration, assure at least that the status quo is maintained. Thus, 

EPA will generally not approve a SIP revision that allows additional emissions of pollutants for 

which an area is designated nonattainment in the absence of offsetting reductions. Because EPA 

now concludesbelieves that Alabama’s SIP revisions are likely to result in an increase in PM 

emissions, for which parts of Alabama are designated nonattainment, it cannot be approved 
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consistent with section 110(l).21 While EPA has previously required a more robust 110(l) 

analysis for nonattainment areas, there is still an analysis required for attainment areas. Section 

110(l) applies to all SIP revisions, regardless of whether the revision is impacting attainment 

areas or nonattainment areas. Alabama’s visible emissions rule at issue is part of Alabama’s plan 

to attain and maintain the NAAQS. The analysis under 110(l) does not depend on what SIP 

revisions are currently due, although 110(l) requires EPA to consider other applicable 

requirements in the SIP. 

Comment 46. Commenters explained that because they believe that there is no 

relationship between opacity and PM, the inquiry as to 110(l) could end there. Commenters also 

argued against substituting the words “could interfere” for “would interfere” in 110(l). 

Response 46. EPA does not agree that there is no relationship between opacity and PM 

emissions. Rather, EPA concludesbelieves that there is a general relationship between opacity 

and PM emissions, but for a specific source and its operating characteristics, there is uncertainty 

about whether increases in opacity are accompanied by increases in PM emissions without 

examination of each source at issue. In addition, EPA does not substitute the words “could 

interfere” for “would interfere” in interpreting and applying 110(l). For any given source at any 

given time, it is accurate to say that increased opacity could be accompanied by increased PM 

emissions. However, in evaluating what would be allowed under the Submittals across all 

sources and circumstances, EPA concludesbelieves it is likely that the increased opacity allowed 

by the Submittals would result in increased PM emissions. EPA judgesbelieves the significant 

 

21 As was discussed above, EPA also concludes that even if the uncertainty about the impact of the SIP revision on 

PM emissions were so great that EPA could make no technical judgment at all about the net effect of this SIP 

revision on PM emissions, the revision would still not be approvable under section 110(l). 
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increase in the flexibility in the opacity exemptions allowed to sources under the revised rule is 

great enough that, absent a convincing demonstration otherwise, the Agency may only conclude 

the revised rule hinders (i.e., “would interfere” with) efforts to attain and maintain compliance 

with the PM NAAQS. 

Comment 47. Commenters explained that changes to Alabama’s Visible Emission Rule 

do not affect compliance with PM limits. According to the commenter, Alabama has not relied 

on opacity limits to demonstrate attainment with the PM NAAQS. Thus, the commenter argued 

that section 110(l) does not apply here at all. 

Response 47. Section 110(l) applies, by its plain text, to all SIP revisions including 

Alabama’s 2003 and 2008 Submittals. Contrary to the commenter’s belief, the State has 

historically included the visible emissions rules in its SIP for purposes of attainment and 

maintenance of the PM NAAQS. The fact that the State may not have sought specific SIP credit 

attributable to the opacity limits (not to be confused with SIP credit for the PM limits that such 

opacity limits are designed to assure compliance with) does not mean that the opacity limits are 

not part of the SIP.

Comment 48. Commenters explained that 110(l) does not require absolute certainty 

regarding interference with attainment and maintenance of the NAAQS. According to the 

commenters, EPA has never taken that position and it would be a departure from Agency 

practice to take such a position. Commenters cited to KRC v. EPA, 467 F.3d 986 (6th Cir. 2006) 

and Galveston-Houston Ass’n for Smog Prevention (GHASP) v. EPA, 289 Fed. Appx. 745 (5th

Cir. 2008). Commenters concluded that EPA cannot rely on mere uncertainty as a basis for 

disapproving a SIP revision. 
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Response 48. EPA agrees that section 110(l) does not require absolute certainty. EPA’s 

decision today relies on certainties concerning the impacts of the revisions to Alabama’s visible 

emissions rules in the Submittals. These certainties include that the Alabama rule would allow 

for increase of maximum opacity from 40 percent to 100 percent and would allow such increases 

for up to 2.4 hours at a time, instead of for only six minutes per hour. EPA is disapproving the 

revision because while there are uncertainties—such as precisely when PM mass emissions 

would increase or by what precise amount —EPA expectsbelieves that it is likely in at least some 

circumstances to result in increases in PM mass emissions. EPA generally, absent an attainment 

demonstration or offsetting emission reductions, will not approve a SIP revision that results in 

increases in emissions of a pollutant for which an area is designated nonattainment pursuant to 

the requirements of section 110(l). EPA has already discussed the KRC case in a previous 

response. The EPA believes the GHASP case also supports EPA’sits position in this action 

because that was another case where the court upheld EPA’s interpretation that section 110(l) 

requires that a SIP revision must at least maintain status quo air quality to be approvable. 

9. CAA Section 110(l) “Demonstration” of Non-interference with the NAAQS and 

Other Requirements 

 Comment 49. Commenters argued that it is not clear what EPA means when it says that 

“Alabama has not provided EPA with an affirmative demonstration that the [Rule] will not 

interfere with the attainment and maintenance of the NAAQS” (74 Fed. Reg. at 50933), since, in 

the commenters’ view, that is exactly what the 2008 revision adding the 22 percent daily average 

cap ensures. Commenters further stated that to require Alabama to provide more than the 

modeling of its 2003 submittal would be contrary to what the CAA requires and would be 
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essentially asking for the impossible given the acknowledged uncertainty between opacity and 

PM, particularly for short-term analysis. 

Response 49. EPA does not agree with the commenters’ interpretation of 110(l) or 

characterization of what was provided to EPA. As was explained above, EPA has concluded that 

the interpretation of 110(l) that is most consistent with the plain text, legislative history, and air 

quality goals of the CAA is that in order to approve the SIP revision, there must be some 

reasonable basis for concluding that the SIP revision will not interfere with attainment or 

maintenance of the NAAQS, consistent with the requirements of 110(l). As commenters 

acknowledged, the evaluation for this particular SIP revision is challenging due to the inherent 

uncertainty in the relationship between opacity and PM mass emissions at a given source. For 

this reason, it is even more important that the demonstration be sufficient to ensure that EPA is 

complying with section 110(l). 

A EPA believes that a fundamental purpose of 110(l) is to allow SIP revisions in the 

absence of a full attainment demonstration provided that such revisions are consistent with 

continued attainment and maintenance of the NAAQS. To the extent that emission increases of a 

particular SIP revision cannot be modeled with some level of certainty regarding impact on the 

NAAQS, section 110(l) may bar that SIP revision, absent equivalent offsetting emissions 

reductions and in the absence of an attainment or maintenance demonstration. In EPA’s 

judgment, the analysis submitted in connection with the SIP revisions at issue here fails to 

provide a reasonable basis on which to conclude that the changes would not interfere with 

attainment and maintenance of the NAAQS. EPA concludes that the CAA prohibits this SIP 

revision because air emissions could be allowed to increase and thus, worsen air quality in 
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nonattainment areas. 

 Comment 50. Commenters argued that there is no basis for reversing EPA’s prior 

analysis because the current SIP ensures opacity will be equal to or lower than that allowed 

under the previous SIP. Commenters further stated that EPA demonstrated mathematically that 

both the suggested changes in its 2007 proposal to approve the Rule and in Alabama’s 2008 

revisions as submitted are at least as stringent as Alabama’s existing SIP and even more stringent 

than the 2003 revisions.

Response 50. As discussed above, EPA has concluded after reconsideration that it is not 

appropriate to measure the stringency of the SIP revisions in the Submittals using an “average 

daily limit.” Alabama’s revised rule allows for extended periods of operation at high levels of 

opacity that were not previously authorized. Absent a showing that a source’s PM emissions 

would not be elevated if it was permitted to have opacity at up to 100 percent for up to 2.4 hours 

a day, EPA has concluded that the SIP revisions would be inconsistent with section 110(l). 

 Comment 51. Commenters argued that Alabama has made an affirmative demonstration 

that the visible emissions standards in the previous SIP and the revised SIP are equivalent. 

Alabama’s previous visible emissions rule allowed opacity of up to 40 percent for one six-minute 

period per hour. The revised rule allows the same maximum time of higher opacity in a single 

day (up to 144 minutes per day), but eliminates the 40 percent cap. To assure equivalency with 

the previous rule, the revised SIP limits the daily average opacity to less than 22 percent. The 

basis for derivation of the 22 percent limit was clearly set out in EPA’s final rule. 73 FR at 

60958-59 (October 15, 2008). 

Response 51. As explained above, as a result of this reconsideration EPA disagrees that 
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the two versions of the visible emissions rules could be equivalent, as explained in detail in the 

Rule Comparison TSD included in the docket. Ultimately, if the impacts of the two versions 

were actually equivalent, there would be no reason for Alabama to seek the SIP revisions. The 

practical reality is that the revised rule allows for opacity increases not previously authorized 

(both in concentration and quantity of time). Furthermore, the rule at issue specifically affects 

facilities which for one reason or another are not subject to any other opacity limit – and thus this 

opacity limit is particularly important both for air quality and as an indicator of facility O & M. 

While EPA understands the commenters’ concerns, EPA does not agree that the two versions of 

the visible emissions rules are equivalent. 

 Comment 52. One commenter stated that EPA’s approval was entirely consistent with 

section 110(l). According to the commenter, EPA made an “appropriate inquiry” under section 

110(l) to protect the NAAQS because it made an equivalency determination and did not rely 

solely on uncertainty as a basis for the approval. This commenter believes that any uncertainty is 

erased by the 22 percent cap. 

Response 52. EPA’s October 15, 2008, final action relied heavily on the uncertainty 

inherent in the relationship between opacity and PM mass emissions. The October 15, 2008, 

action was different from other 110(l) analyses previously completed by EPA for that reason. 

EPA agrees that this rule presents particularly complex technical issues but has ultimately 

decided that heavy reliance on uncertainty as a basis for approval is not the decision most 

consistent with the CAA. Section 110(l) is intended to preclude SIP revisions that could have 

adverse consequences for public health, and accordingly EPA thinks that it should continue to 

interpret the provision using a precautionary principle to ensure such public health protection in 
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the face of uncertainty about the impacts of a SIP revision. 

Comment 53. Commenters drew comparisons between Ohio’s recent opacity proposal 

and North Carolina’s previous opacity proposal and concluded that Alabama’s opacity limits are 

far below those of other states (specifically, North Carolina and Georgia). 

Response 53. EPA does not agree with commenters’ assessment of opacity requirements 

in other states. Alabama’s revised rule was unique in that it allows opacity of up to 100 percent 

opacity (not allowed under the recent North Carolina revisions) – and it allows such opacity for 

up to 2.4 consecutive hours. Opacity revisions, by nature, require detailed case-by-case analyses. 

Due to the specific circumstances of a state (i.e., attainment status, affected facilities, 

topography, etc...), it is difficult to directly compare opacity rules from state to state (or SIP to 

SIP). While previous opacity decisions are informative, no other state presents a circumstance 

totally analogous to Alabama’s circumstances. In addition, EPA has proposed to disapprove 

comparable revisions to the visible emissions rules in the Ohio SIP for reasons comparable to 

those described in this final action. 

9. Use of COMS and Need for Exemptions 

 Comment 54. One commenter argued that without a regulatory mechanism to address 

excess emissions reported from COMS, such as that used by Alabama, sources are vulnerable to 

enforcement actions for short term opacity excursions that have negligible environmental effects. 

Response 54. The EPA believes the environmental effect of individual “short-term” 

opacity excursions depends upon the duration and level of such exceedances, as well as the 

relationship between opacity and PM emissions at the source where they occur. This is one 

reason why EPA has concluded that use of an “average daily opacity” cap, in which longer 
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excursions at higher levels are allowed to be “averaged out” with periods of normal operation at 

lower opacity levels, does little to help reduce PM emissions. Therefore, an “average daily 

opacity cap” is not a sufficient basis to approve the proposed SIP revisions. Frequent recurrence 

of such events may reflect the need to improve source operation or emission controls in order to 

comply with the opacity limit, but that would be masked by the averaging effect of an average 

daily opacity standard. 

In the case of the visible emissions rule changes at issue in these SIP revisions, some 

sources may have to take action to improve their opacity performance in order to comply with 

the previous SIP rule. Finally, today’s action does not impede the State’s ability to exercise its 

own enforcement discretion in the event that it decides a given opacity violation does not warrant 

such action. 

 Comment 55. Commenters explained that when utilizing COMS that yield opacity data 

for nearly 100 percent of source operating time, given the extremely short data averages utilized 

for opacity data (six-minute data averages), time periods of excess occur from even the best 

operated sources. 

Response 55. EPA acknowledges that some sources may have difficulty in complying 

with 20 percent opacity limits 100 percent of the time, especially when events out of the source’s 

control occur, but EPA expectsbelieves that all sources can comply with the pre-existing version 

of the visible emissions rule that will be in place as a result of today’s disapproval action. EPA 

expects that any unusual difficulties for specific sources would ease as sources subject to 

Alabama’s visible emissions rule take steps to improve their opacity performance. 

 Comment 56. One commenter explained that 40 CFR section 60.284(e) is the recognition 
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by EPA that some type of exemption time period is necessary when opacity regulations are 

enforced by a continuous in-stack monitoring system and that this regulation is probably the 

basis of the Alabama SIP revisions. The commenter further explained its view that the preamble 

to both the NSPS (40 CFR 60.7(c)) and the maximum available control technology (40 CFR 

63.10(e)(3)) both state that sources required to submit reports of excess emissions from 

continuous in-stack monitoring systems are only required to submit summary reports of the 

excess emissions data and not detailed reports, provided that the total duration of excess is less 

than one percent of the total operating time of the monitored source for the operating time period 

and that the monitor downtime is less than five percent of the total operating time of the 

monitored source for the reporting time period. The commenter considered these two regulations 

as a “de facto” recognition by EPA of [the need for] exemption time periods similar to that 

proposed in the Alabama SIP revisions. 

Response 56. EPA disagrees with the premise of the comment, as it misses the mark 

concerning what is relevant in the context of a SIP revision for purposes of section 110(l). The 

NSPS and SIPs serve different purposes under the CAA. The NSPS are industry-specific 

nationally uniform air emission standards that limit the amount of emissions allowed from new 

sources or from modified existing sources. They are technology-based standards, meaning that 

they contain industry-specific limitations based on the best available technology. Under section 

111 of the CAA, a standard of performance must reflect the degree of emission limitation and the 

percentage reduction achievable through application of the best technological system of 

continuous emission reduction that the Administrator determines has been adequately 

demonstrated. Such determinations take into consideration the cost of achieving such emission 
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reduction and any non-air quality health and environmental impact and energy requirements. 

The fact that such standards contain various reporting requirements about excess emissions does 

not address the issues relevant to an analysis to support a SIP revision. 

 SIPs are EPA-approved state plans for the establishment, regulation, and enforcement of 

air pollution standards – the NAAQS. Under section 110 of the Act, each state must adopt a plan 

to provide for implementation, maintenance, and enforcement of the primary and secondary 

NAAQS within the state. Because SIPs serve a different purpose than the NSPS, EPA evaluates 

them differently. For example, the NSPS provide exemptions from compliance during brief 

periods such startup, shutdown, and malfunctions (SSM). Such automatic exemptions are not 

appropriate for SIP rules because SIPs are ambient-based standards and any emissions above the 

allowable may cause or contribute to violations of the NAAQS. Generally, because SIPs must 

provide for attainment and maintenance of the NAAQS and the achievement of prevention of 

significant deterioration increments, EPA’s policy is that all periods of excess emissions must be 

considered violations. SIPs can contain regulations with affirmative defenses for violations that 

occur due to events not reasonably within the control of the source, but they should not contain 

automatic exemptions. EPA’s policy with respect to appropriate SIP provisions is contained in 

the 1999 memorandum entitled “State Implementation Plans (SIPs): Policy Regarding Excess 

Emissions During Malfunctions, Startup, and Shutdown.” 

Comment 57. Commenters explained that despite its best efforts, continuous compliance 

with the 20 percent opacity limit is an unachievable goal, and imposing penalties for failing to 

achieve an unattainable goal does not promote continuous, long term environmental 

improvement. 
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Response 57. EPA’s final action does not impose penalties or implicate any specific 

enforcement actions. Rather, it simply finds that Alabama’s revisions to its visible emissions 

rule are not approvable under section 110(l) of the CAA. EPA encourages the commenter to 

discuss specific compliance concerns with ADEM. Sources should generally be capable of 

complying with the Alabama opacity rule, but we remain open to considering further SIP 

revisions that provide greater assurance that PM emissions will not increase as a result. 

10. Relationship of SIP Revisions to 40 CFR Section 51.212 

 Comment 58. Commenters argued that the visible emissions rule in the revised SIP is 

appropriate under 40 CFR 51.212(b). Some commenters also discussed that the “indirect” use of 

COMS for compliance determinations adopted by Alabama and many other states is based on the 

approach adopted by EPA under the NSPS, which also specify Method 9 as the compliance 

method but require reporting of COMS data as an indicator of good control device O&M. The 

commenters asserted that because ADEM’s rule continues to use COMS data as an indicator of 

good O&M, but now simply provides an option for its use “directly . . . for compliance 

determinations,” respecting the independently enforceable opacity limit as allowed under 

Appendix P, the rule continues to meet EPA’s criteria. Other commenters highlighted the 

position that 51.212 provides states with discretion and the Alabama rule enhances enforcement 

through use of COMS. 

Response 58. In the present action, EPA is not evaluating the approvability of the SIP 

revision to Alabama’s visible emission rule revisions in light of the requirements of 40 CFR 

51.212. While EPA agrees that this provision requires states to have SIPs with appropriate 

methods to assure compliance with emissions limits, EPA is not here addressing whether the 
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revisions at issue would or would not meet those requirements. EPA’s analysis for the present 

action focused on the section 110(l) limitations on EPA’s authority to approve a SIP revision. 

Even if Alabama’s revised visible emissions rule were consistent with section 51.212, this would 

not alleviate the concerns that EPA has with respect to section 110(l). 

Comment 59. Commenters stated that ADEM’s two percent criterion is consistent with 

policies developed by EPA in the 1980s to support the use of continuous monitors. Commenters 

noted that there is no national standard on visible emissions and ADEM’s use of a flexible 

approach is consistent with part 51. 

Response 59. In the present rulemaking, EPA is not articulating a position on ADEM’s 

enforcement discretion or policies regarding enforcement discretion, although EPA is aware of 

the fairly recent Eleventh Circuit Court’s opinion addressing ADEM’s enforcement discretion in 

a visible emissions context. As was explained earlier, EPA acknowledges the various comments 

that support ADEM’s Submittals by citing to other federal requirements. However, EPA’s 

analysis was focused on its authority under section 110, and the review of ADEM’s Submittals 

that is most supported by the CAA.

11. Relationship of SIP Revisions to Compliance Assurance Monitoring (CAM) Rule 

 Comment 60. Commenters explained that although Alabama’s visible emissions rule 

may have some role in evaluating long-term PM control device operation, it is no longer the 

primary means by which major sources assure compliance with SIP limits on PM. Commenters 

believe that this role is now filled by EPA’s CAM rule at 40 CFR part 64. 

Response 60. EPA’s present action is not dependent upon whether the State’s visible 

emissions rule is the “primary” means for evaluating compliance with PM limits, although that 
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has been and continues to be a legitimate reason for such opacity limits in SIPs. EPA’s present 

action is based primarily on its obligation under section 110(l) not to approve SIP revisions that 

would interfere with attainment or maintenance of the NAAQS or other applicable requirements 

of the CAA. EPA agrees that the CAM rule provides additional support for evaluation of control 

device operation; however, CAM applicability and methodologies vary from facility-to-facility. 

The CAM rule is designed to provide reasonable assurance of ongoing compliance with 

applicable emissions limits, such as the PM emission limits of the SIP. But CAM requirements 

are in addition to the requirements of Alabama’s visible emissions rule; as a result, the 

commenters’ statements do not resolve whether the revisions to the visible emissions rule satisfy 

section 110(l). 

12. Relationship of SIP Revisions to Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), 

and the Vacatur of Certain Provisions in 40 CFR part 63 

 Comment 61. Commenters explained that the D.C. Circuit Court’s vacatur of 40 CFR 

part 63 provisions pertaining to SSM and its impact on the opacity SIP revision are irrelevant. 

Further, commenters noted that SSM provisions are not at issue in the instant SIP revision. 

Response 61. EPA does not agree with the blanket statement that SSM provisions are not 

at issue in the instant SIP revision. As part of EPA’s 110(l) evaluation, EPA may consider the 

SIP as a whole – including other provisions, such as SSM provisions, that may further affect the 

consequences of a given SIP revision. In this case, EPA’s analysis focused primarily on the 

provisions of the visible emissions rule that the State actually sought to change in the Submittals. 

However, EPA may consider the entirety of a rule, and the SIP, in completing a 110(l) analysis. 

13. Relationship of SIP Revisions to Reasonably Available Control Technology (RACT) 
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Comment 62. Commenters explained that the Submittals on opacity are not required to 

comply with RACT and that there is no requirement for EPA to review “unrelated SIP revisions 

requests” for future RACT compliance. Moreover, commenters stated that when Alabama does 

submit a SIP revision to address RACT, EPA is not compelled to require that revision to 

establish any particular opacity standard. Another commenter stated that Alabama’s revised SIP 

imposes the proper opacity RACT standard. Several commenters noted that the Petitioners will 

have separate opportunity to challenge RACT determinations is RACT-specific rulemaking. 

Response 62. RACT refers to equipment and practices that reduce pollutant emissions 

that are reasonably available and both technologically and economically feasible. RACT usually 

applies to existing sources in nonattainment areas. Since EPA has concluded that this revision is 

not approvable under section 110(l) for the reasons already stated, it is not necessary to 

determine whether Alabama has relied on opacity limits to meet its RACT obligations. 

Notably, section 172 of the Act, Nonattainment plan provisions in general, requires 

nonattainment plans “shall provide for the implementation of all reasonably available control 

measures as expeditiously as practicable (including such reductions in emissions from existing 

sources in the area as may be obtained through the adoption, at a minimum, of reasonably 

available control technology) and shall provide for attainment of the national primary ambient air 

quality standards.” Section 172 requirements, including RACT, are applicable requirements of 

the CAA which section 110(l) evaluations may consider. 

Section 110(l) requires that EPA consider whether the revision at issue would interfere 

with the NAAQS, and any other applicable requirement concerning attainment and RFP. Thus, 

EPA is authorized to consider whether the revision would interfere with an area’s ability to 
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comply with RACT or other requirements in the SIP. In this case, however, EPA’s review was 

primarily focused on interference with the NAAQS. While some applicable requirements may 

be subject to separate SIP revisions, as was noted by several commenters, that does not mean that 

EPA is prohibited from considering whether revision of a rule at issue may implicate another 

applicable requirement. RACT issues are likely to also be addressed separately in other SIP 

revisions. 

14. Other Exemptions in Alabama SIP Related to Visible Emissions 

Comment 63. Commenters noted that EPA’s final action was not inconsistent with EPA 

policies on excess emissions and director’s discretion. 

Response 63. As was previously noted by EPA in the 2007 proposal and the October 

2008, action, the director’s discretion provisions under Alabama rule 335–3–4–.01(1)(c) and (d) 

are unchanged by the SIP revisions. As a result, periods of excess emissions allowed in a permit 

pursuant to those provisions remain unchanged under Alabama’s rules. EPA did, however, 

consider Alabama’s provisions for excess emissions in evaluating the rule as a whole and 

comparing it with the previous EPA-approved SIP rule. These types of details become relevant, 

particularly when parties compare Alabama’s visible emissions rules with those in other states. 

In this action, EPA is not taking any action on Alabama’s existing SIP-approved rules that 

implicate director’s discretion and excess emissions. 

IV. Final Action 

EPA is taking final action to amend an October 15, 2008, final rulemaking on two SIP 

revisions regarding the State of Alabama’s rules for visible emissions from certain stationary 

sources. EPA has now determined upon reconsideration that Alabama’s SIP revisions, dated 
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September 11, 2003, and August 22, 2008, are not approvable pursuant to CAA section 110(l). 

Accordingly, EPA is now disapproving the revisions submitted by the State of Alabama on 

September 11, 2003, and August 22, 2008. As a result of this action, Alabama’s visible 

emissions rule that was in the SIP prior to the October 15, 2008, final action will be the “current” 

SIP-approved rule. Alabama is urged to undertake rulemaking in order to conform its SIPapproved rule with its State-effective rule. 

V. Statutory and Executive Order Reviews 

A. Executive Order 12866, Regulatory Planning and Review 

This final action has been determined to be a “significant regulatory action” subject to 

review by the Office of Management and Budget (OMB) under Executive Order 12866 (58 FR 

51735, October 4, 1993). Accordingly, EPA submitted this action to the Office of Management 

and Budget (OMB) for review under Executive Order 12866 and any changes made in response 

to OMB recommendations have been documented in the docket for this action.

B. Paperwork Reduction Act 

This action does not impose an information collection burden under the provisions of the 

Paperwork Reduction Act, 44 U.S.C. 3501 et seq., because these SIP disapprovals under section 

110 will not in-and-of itself create any new information collection burdens but simply 

disapproves certain State requirements for inclusion into the SIP. Burden is defined at 5 CFR 

1320.3(b). 

C. Regulatory Flexibility Act (RFA)

The RFA generally requires an agency to conduct a regulatory flexibility analysis of any 

rule subject to notice and comment rulemaking requirements unless the agency certifies that the 
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rule will not have a significant economic impact on a substantial number of small entities. Small 

entities include small businesses, small not-for-profit enterprises, and small governmental 

jurisdictions. For purposes of assessing the impacts of today's rule on small entities, small entity 

is defined as: (1) a small business as defined by the Small Business Administration’s 

regulations at 13 CFR 121.201; (2) a small governmental jurisdiction that is a government of a 

city, county, town, school district or special district with a population of less than 50,000; and (3) 

a small organization that is any not-for-profit enterprise which is independently owned and 

operated and is not dominant in its field. This rule will not have a significant impact on a 

substantial number of small entities because EPA understands that only one small entity will be 

affected by this rule. Furthermore, even if additional small entities were affected by this rule, 

this rule would not have a significant economic impact on any small entity because it simply 

restores a long-standing requirement of the Alabama SIP concerning visible emissions. 

Therefore, after considering the economic impacts of today's rulemaking on small 

entities, I certify that this action will not have a significant economic impact on a substantial 

number of small entities. 

D. Unfunded Mandates Reform Act

This action contains no Federal mandates under the provisions of Title II of the Unfunded 

Mandates Reform Act of 1995, 2 U.S.C. 1531-1538 “for State, local, or tribal governments or the 

private sector.” EPA has determined that the disapproval action does not include a Federal 

mandate that may result in estimated costs of $100 million or more to either State, local, or tribal 

governments in the aggregate, or to the private sector. This Federal action determines that preexisting requirements under State or local law should not be approved as part of the Federally 
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approved SIP. It imposes no new requirements. Accordingly, no additional costs to State, local, 

or tribal governments, or to the private sector, result from this action. 

E. Executive Order 13132, Federalism

Executive Order 13132, entitled “Federalism” (64 FR 43255, August 10, 1999), requires 

EPA to develop an accountable process to ensure “meaningful and timely input by State and 

local officials in the development of regulatory policies that have Federalism implications.” 

“Policies that have Federalism implications” is defined in the Executive Order to include 

regulations that have “substantial direct effects on the States, on the relationship between the 

national government and the States, or on the distribution of power and responsibilities among 

the various levels of government.” 

This action does not have Federalism implications. It will not have substantial direct 

effects on the States, on the relationship between the national government and the States, or on 

the distribution of power and responsibilities among the various levels of government, as 

specified in Executive Order 13132, because it merely disapproves certain State requirements for 

inclusion into the SIP and does not alter the relationship or the distribution of power and 

responsibilities established in the CAA. Thus, Executive Order 13132 does not apply to this 

action. 

F. Executive Order 13175, Coordination With Indian Tribal Governments

This action does not have tribal implications, as specified in Executive Order 13175 (59 

FR 22951, November 9, 2000), because the SIP EPA is disapproving would not apply in Indian 

country located in the State, and EPA notes that it will not impose substantial direct costs on 

tribal governments or preempt tribal law. This final rule does not have tribal implications, as 
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specified in Executive Order 13175. It will not have substantial direct effects on tribal 

governments, on the relationship between the Federal government and Indian tribes, or on the 

distribution of power and responsibilities between the Federal government and Indian tribes. 

This action does not involve or impose any requirements that affect Indian Tribes. Thus, 

Executive Order 13175 does not apply to this action. 

G. Executive Order 13045, Protection of Children From Environmental Health Risks and Safety 

Risks

EPA interprets Executive Order 13045 (62 FR 19885, April 23, 1997) as applying only to 

those regulatory actions that concern health or safety risks, such that the analysis required under 

section 5-501 of the Executive Order has the potential to influence the regulation. This action is 

not subject to Executive Order 13045 because it is not an economically significant regulatory 

action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 

1997). This SIP disapproval under section 110 will not in-and-of itself create any new rules but 

simply disapproves certain State requirements for inclusion into the SIP. 

H. Executive Order 13211, Actions That Significantly Affect Energy Supply, Distribution, or Use

This action is not a “significant energy action” as defined in Executive Order 13211 (66 

FR 28355 (May 22, 2001)), because it is not likely to have a significant adverse effect on the 

supply, distribution, or use of energy. We have concluded this rule is not likely to have a 

significant adverse effect on the supply, distribution or use of energy because this rule applies 

only to 19 facilities in Alabama and simply restores a long-standing rule concerning visible 

emissions. 

I. National Technology Transfer and Advancement Act (NTTAA)
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Section 12(d) of the NTTAA of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 

U.S.C. 272 note) directs EPA to use voluntary consensus standards (VCS) in its regulatory 

activities unless to do so would be inconsistent with applicable law or otherwise impractical. 

VCS are technical standards (e.g., materials specifications, test methods, sampling procedures, 

and business practices) that are developed or adopted by VCS bodies. NTTAA directs EPA to 

provide Congress, through the OMB, explanations when the Agency decides not to use available 

and applicable VCS. 

EPA believes that this action is not subject to requirements of Section 12(d) of NTTAA 

because application of those requirements would be inconsistent with the CAA. Today’s action 

does not require the public to perform activities conducive to the use of VCS. 

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority 

Populations and Low-Income Populations

Executive Order 12898 (59 FR 7629, (February 16, 1994)) establishes Federal executive 

policy on environmental justice. Its main provision directs Federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental justice part of their mission by 

identifying and addressing, as appropriate, disproportionately high and adverse human health or 

environmental effects of their programs, policies, and activities on minority populations and lowincome populations in the United States. 

EPA lacks the discretionary authority to address environmental justice in this action. In 

reviewing SIP submissions, EPA’s role is to approve or disapprove State choices, based on the 

criteria of the CAA. Accordingly, this action merely disapproves certain State requirements for 

inclusion into the SIP under section 110. Accordingly, it does not provide EPA with the 
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discretionary authority to address, as appropriate, disproportionate human health or 

environmental effects, using practicable and legally permissible methods, under Executive Order 

12898. 

K. Congressional Review Act

The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the Small Business 

Regulatory Enforcement Fairness Act of 1996, generally provides that before a rule may take 

effect, the agency promulgating the rule must submit a rule report, which includes a copy of the 

rule, to each House of the Congress and to the Comptroller General of the United States. EPA 

will submit a report containing this rule and other required information to the U.S. Senate, the 

U.S. House of Representatives, and the Comptroller General of the United States prior to 

publication of the rule in the Federal Register. A major rule cannot take effect until 60 days after 

it is published in the Federal Register. This action is not a "major rule" as defined by 5 U.S.C. 

804(2). This rule will be effective [FEDERAL REGISTER OFFICE: insert date 30 days from

date of publication of this document in the Federal Register]. 

L. Petitions for Judicial Review 

Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be 

filed in the United States Court of Appeals for the appropriate circuit by [FEDERAL REGISTER 

OFFICE: insert date 60 days from date of publication of this document in the Federal Register]. 

Filing a petition for reconsideration by the Administrator of this final rule does not affect the 

finality of this rule for the purposes of judicial review nor does it extend the time within which a 

petition for judicial review may be filed, and shall not postpone the effectiveness of such rule or 
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action. This action may not be challenged later in proceedings to enforce its requirements. See

CAA section 307(b)(2). 
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List of Subjects in 40 CFR Part 52

 Environmental protection, Air pollution control, Carbon monoxide, Incorporation by 

reference, Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, Particulate matter, 

Reporting and recordkeeping requirements, Sulfur oxides, Volatile organic compounds. 

Dated: __________________________________ 

 

 Regional Administrator, 

 Region 4. 
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40 CFR part 52 is amended as follows: 

PART 52-[AMENDED] 

1. The authority citation for part 52 continues to read as follows: 

Authority: 42 U.S.C. 7401 et seq. 

Subpart B – Alabama 

2. Section 52.50(c) is amended by revising the entry for “Section 335-3-4-.01” to read as 

follows:

§52.50 Identification of plan.

* * * * * 

 (c) * * * 

EPA Approved Alabama Regulations 

State citation Title/subject State effective 

date 

EPA approval 

date 

Explanation 

** ** * * * 

Section 335-3-4-

.01 

Visible 

Emissions 

10/15/1996 [Insert 

date of 

publication 

in Federal 

Register] 

[Insert citation of 

publication] 

** ** * * * 

* * * * *