2024-19600. Air Plan Disapproval; Texas; Control of Air Pollution From Visible Emissions and Particulate Matter

Table 1—The Affected Power Plants, Agreed Order Number, and the Texas County

Affected power plants per August 20, 2020 SIP submittal	Agreed order No.	Texas county
Southwestern Electric Power Company (SWEPCO) H.W. Pirkey Power Plant (See FN 14)	2020-0078	Harrison.
Lower Colorado River Authority (LCRA) Sam Seymour Fayette Power Project	2020-0077	Fayette.
Luminant Generation Company, LLC Martin Lake Steam Electric Station	2020-0076	Rusk.
NRG Texas Power, LLC Limestone Electric Generating Station	2020-0075	Limestone.
San Miguel Electric Cooperative, Inc. San Miguel Electric Plant	2020-0074	Atascosa.
Southwestern Public Service Company (SPS) Harrington Station in Potter County	2020-0073	Potter.
Texas Municipal Power Agency (TMPA) Gibbons Creek Steam Electric Station (See FN 14)	2020-0178	Grimes.
Public Service Company of Oklahoma (PSCO) Oklaunion Power Station (See FN 14)	2020-0072	Wilbarger.

As stated earlier, if approved, this SIP revision would amend the SIP to provide that the sources subject to the 8 AOs in this SIP revision are required to comply with the stated visible (opacity) and PM emissions restrictions of 30 TAC 111.111 and 30 TAC 111.153(b) during all periods of operation except periods of MSS during which time the requirements of the AOs would apply. Any other sources subject to 30 TAC 111.111 and 30 TAC 111.153(b), not addressed with AOs in this SIP revision, would be required to comply with 30 TAC 111.111 and 30 TAC 111.153(b) at all times including during periods of MSS.

Each of the AOs is comprised of two main sections titled Stipulation and Ordering Provisions. The Stipulation section of the AOs describes the State air agency's authority for regulating the quality of the State's air and preparing and developing a general, comprehensive plan for the control of the State's air pollution. It also explains that under 42 U.S.C. 7410, Texas is required to submit SIP revisions to EPA for review and approval and that such SIP revisions cannot interfere with any applicable provision concerning attainment or any other applicable requirement of the CAA. The Ordering Provisions section of the AOs state that emissions from the boiler(s), during each planned MSS, shall comply with the opacity limit in 30 TAC § 111.111(a)(1) and the PM limit in 30 TAC § 111.153(b), or the requirements listed in detail and tailored for planned MSS activities. Each of the AOs is signed by the responsible corporate official and TCEQ representatives.

II. Applicability of Opacity and PM Limitations in 30 TAC 111

As an initial matter, we acknowledge TCEQ's interpretation of its regulations is that the existing SIP approved limitations on opacity and PM contained in 30 TAC 111.111(a)(1) and 30 TAC 111.153(b) do not apply to the sources subject to this SIP revision during periods of planned MSS. However, as written, these rules do not contain exemptions or any other textual indication that they do not apply during periods of MSS. We do note that the ESPs that are the existing control measures for PM on these sources have technical constraints that prohibit safe and effective operations until sufficient temperatures are reached therefore it is highly improbable that these sources could have met the limitations required by the rules during MSS as historically ( print page 71240) configured, over the past fifty years. Texas has employed a number of approaches over the years to address emissions from these sources during MSS events, including discretionary exemptions, affirmative defenses, amending the facility permits to authorize the emissions during MSS events, and now the 2020 SIP submission. While the state's approaches (and explanations) have changed over time, we are not aware of any instance that Texas has taken an explicit action to require companies to meet the requirements set forth in 30 TAC 111.111(a)(1) or 30 TAC 111.153(b) during periods of MSS. In particular, Texas has not taken an enforcement action against these sources for failure to comply with the 30 TAC 111 limits during MSS and that called for any of these sources to upgrade their controls to comply with the limits in the future. EPA has never taken enforcement action with respect to the limitations in 30 TAC 111.111(a)(1) and 30 TAC 111.153(b) for emissions during MSS periods. In the 2020 submission, TCEQ states that these existing SIP approved rules do not apply to emissions during MSS periods but that it now intends to address such emissions through the eight new source specific AOs.

III. Evaluation of Emission Limitations in the SIP Revision

A. SIP Requirements for Emissions Limitations

CAA section 302(k) provides, in relevant part, that “the terms `emission limitation' and `emission standard' mean a requirement established by the State or the Administrator which limits the quantity, rate, or concentration of emissions of air pollutants on a continuous basis, including any requirement relating to the operation or maintenance of a source to assure continuous emission reduction, and any design, equipment, work practice or operational standard promulgated under this chapter.” Further, CAA Section 110(a)(2)(A) requires that SIPs include “enforceable emission limitations and other control measures, means, or techniques (including economic incentives such as fees, marketable permits, and auctions of emissions rights), as well as schedules and timetables for compliance, as may be necessary or appropriate to meet the applicable requirements of this chapter.” In light of these two provisions, EPA's position is, and has been, that emissions limitations contained in SIPs must be continuous. Because emission limitations must be continuous, they cannot include gaps or periods during which sources are not required to limit their emissions and thus, for example, cannot include exemptions for emissions during periods of operation such as MSS. While emission limits need to be continuous, EPA also believes that SIP emission limitations: (i) do not need to be numerical in format; (ii) do not have to apply the same limitation ( e.g., numerical level) at all times; and (iii) may be composed of a combination of numerical limitations, specific technological control requirements and/or work practice requirements, with each component of the emission limitation applicable during a defined mode of source operation.

B. Environ. Comm. Fl. Elec. Power v. EPA, 94 F.4th 77 (D.C. Cir. 2024)

As noted, the SIP submission at issue in this action raises issues related to emissions during MSS. The term MSS has considerable overlap with the events EPA refers to as startup, shutdown, and malfunction (SSM).^[15] Issues associated with SSM are discussed at length in a SIP Call that EPA issued to states in 2015 (the 2015 SSM SIP Action).^[16] A number of parties challenged the 2015 SSM SIP Action on various grounds. On March 1, 2024, the D.C. Circuit Court of Appeals issued a decision in Environ. Comm. Fl. Elec. Power v. EPA, 94 F.4th 77. The case was a consolidated set of petitions for review of the 2015 SSM SIP Action. The Court granted the petitions in part, vacating the 2015 SSM SIP Action with respect to specific SIP provisions that the EPA identified as automatic exemptions, director's discretion provisions, and affirmative defenses that are functionally exemptions, and denied the petitions as to other provisions that the EPA identified as overbroad enforcement discretion provisions or affirmative defense provisions that would preclude or limit a court from imposing relief in the case of violations.

Specific to this action, EPA notes that the Court vacated the 2015 SSM SIP Action with respect to SIP provisions that contain automatic exemptions for emissions during SSM events, and that EPA had considered automatic exemptions for emissions during other modes of operation such as maintenance to pose the same legal deficiency. In the 2015 SSM SIP Action, EPA found that certain SIP provisions were inconsistent with CAA 110(a)(2)(A) and 302(k). CAA 110(a)(2)(A) requires SIPs to “include enforceable emission limitations and other control measures, means, or techniques . . . as may be necessary or appropriate to meet the applicable requirements of this chapter.” Because the automatic exemption provisions excluded applicability of emission limitations during SSM periods, the emission limitations at issue no longer operated on a “continuous basis” as required by CAA 302(k).

Significantly, the Court vacated the 2015 SSM SIP Action as to automatic exemptions, because the Agency did not first determine that the particular SIP provisions at issue were “emissions limitations” as defined by CAA 302(k), or that it was “necessary or appropriate” that these provisions be such an emission limitation under CAA section 110(a)(2)(A). The court's opinion stated that while emission limitations must be continuous, SIPs can contain “other control measures, means, or techniques” per CAA 110(a)(2)(A), and such other measures, means, or techniques do not need to meet the CAA's definition of an “emission limitation,” including the requirement that it apply on a continuous basis. The Court therefore took issue with EPA's SIP call for SIP provisions with automatic SSM exemptions, on the basis that “EPA's rationale breaks down if the measure need not qualify as an `emission limitation' in the first place,” and therefore such measure would need not meet the continuity requirement.^[17]

In light of the court's decision, EPA is evaluating the nature of the SIP provisions at issue in this action. Based on the language of the existing SIP provisions and the SIP submission at issue in this action, EPA finds that 30 TAC 111.111(a)(1) and 30 TAC 111.153(b) are emissions limitations as contemplated under 110(a)(2)(A) and 302(k), and thus are required to be continuous. Texas, in its submittal, confirms that it adopted the AOs for these eight sources to ensure that the SIP provisions are emission limitations that apply continuously. From the SIP submission in the Executive Summary, “[t]he proposed SIP revision would make certain operational limits and work practices for periods of planned MSS at the listed EGUs federally enforceable so that emission limitations apply on a continuous basis (at all times of operation) (see FCAA, § 110(a)(2)(A)—SIP must contain emission limits, measures, etc. and ( print page 71241) § 302(k)—emission limits apply on a continuous basis to assure continuous emission reduction). The SIP revision, through the AOs, would establish a SIP limitation for those periods when the SIP limits for PM and opacity contained in § 111.111 and § 111.153 do not apply due to the technical limitations of the ESPs at the power plants that will be subject to the AOs.” Thus, TCEQ indicated that it specifically submitted the SIP revision with the AOs to ensure that the emission limitations apply on a continuous basis, including during MSS periods. EPA agrees that these SIP limits for PM and opacity are emissions limitations that must be continuous under CAA § 302(k). We also note that the state originally submitted these rules as part of the initial Texas SIP intended to provide for the attainment and maintenance of the NAAQS, and EPA originally approved them for this purpose ( See37 FR 10896), further confirming that these specific rules should be considered emission limitations and “necessary and appropriate to meet the requirements of this chapter,” in this case attainment and maintenance of the NAAQS.

IV. Evaluation of Alternative Emission Limits

A. EPA Recommendations for Development of Alternative Emission Limitations

As previously discussed, Texas has identified 30 TAC 111.111(a)(1) and 30 TAC 111.153(b) as emission limitations, and EPA agrees with this description. Accordingly, the rules must be continuous and cannot have exemptions. The state indicated that it specifically submitted the SIP revision with the AOs to ensure that the emission limitations apply on a continuous basis, including during MSS periods.

The revision submitted by Texas takes the form of new Alternative Emission Limitations (AELs) intended to apply during MSS periods. The EPA interprets the CAA (80 FR 33913, June 12, 2015) to allow SIP provisions to include AELs that apply to sources during specific modes of operation during which the source cannot meet an otherwise applicable emission limitation, such as may be the case during MSS periods. An AEL, whether a numerical limitation, technological control requirement, or work practice requirement, would apply during a specific mode of operation as a component of the continuously applicable emission limitation. All components of the resulting emission limitation must meet the substantive requirements applicable to the type of SIP provision at issue, must meet the applicable level of stringency for that type of emission limitation, and must be legally and practically enforceable.^[18]

EPA has longstanding guidance for AELs, which it reiterated and restated in the 2015 SSM SIP Action. For the AELs to be approvable ( i.e., meet CAA requirements), alternative requirements applicable to the source during MSS should be narrowly tailored and take into account considerations such as the technological limitations of the specific source category and the control technology that is feasible during startup and shutdown.^[19] As articulated in the 2015 SSM SIP Action, the EPA recommends giving consideration to the following seven specific criteria for states when developing AELs in SIP provisions that apply during modes of operation such as MSS: ^[20] (1) The revision is limited to specific, narrowly defined source categories using specific control strategies; (2) Use of the otherwise applicable control strategy for this source category is technically infeasible during specific modes of operation such as startup or shutdown; (3) The AEL requires that the frequency and duration of operation in MSS mode are minimized to the greatest extent practicable; (4) As part of its justification of the SIP revision, the state analyzes the potential worst-case emissions that could occur during MSS based on the applicable AEL; (5) The AEL requires that all possible steps are taken to minimize the impact of emissions during MSS on ambient air quality; (6) The AEL requires that, at all times, the facility is operated in a manner consistent with good practice for minimizing emissions and the source uses best efforts regarding planning, design, and operating procedures; and (7) The AEL requires that the owner or operator's actions during MSS periods are documented by properly signed, contemporaneous operating logs or other relevant evidence.

We also note that AELs applicable during modes of operation such as startup and shutdown cannot allow an inappropriately high level of emissions or an effectively unlimited or uncontrolled level of emissions, as those would constitute impermissible de facto exemptions for emissions during certain modes of operation.^[21] EPA notes that in order to be continuous, an emission limitation cannot have periods during which a source's emissions are uncontrolled, and this would include modes of operation during which the ostensible method of controlling emissions merely consists of imposing a time limit, i.e., an exemption allowing effectively uncontrolled emissions for a shorter period of time remains an exemption.

B. EPA's Evaluation

After reviewing the information in the Texas SIP submittal, EPA has identified the following concerns:

1. No Limit on Frequency of Startup or Shutdown Events

The requirements in the AOs limit the duration of a normal (as opposed to an extended) planned startup or shutdown to a number of hours per event (48 hours for all units with the exception of Martin Lake units which are limited to 24 hours per normal startups) but provides no limit on the frequency of these events. During these times, the only requirements that apply are the work standards concerning placing the ESP in service as soon as practicable during startup or keeping the ESP in service as late as practicable during shutdown. There is no requirement for the sources to limit emissions during such events in any other way. PM emissions during these events can be much higher than normal emissions and there is no limitation on the number of times during the year a boiler can go through a planned startup or shutdown. The SIP provides no discussion on the historical frequency of these events or why there is no limitation on the total number of hours a year, or times per year, these events may occur.^[22] This is of particular concern as utilization of coal-fired power generation has become more variable and planned startup and shutdown events may occur more frequently.^[23] In EPA's view, the approach adopted by the state in the SIP revision would in effect constitute exemptions from the opacity and PM ( print page 71242) limits in the existing rules, by creating periods of time during which the emissions from these sources would be otherwise uncontrolled. The form of work practices that the state has imposed, e.g., that the source operates the ESP in accordance with manufacturer's instructions, does not effectively reduce emissions during such periods.

2. Consideration of Additional Steps and Practices To Minimize Emissions

With respect to factors 5 and 6, AELs should require that all possible steps are taken to minimize the impact of emissions during modes of operation such as MSS on ambient air quality and to require that, at all times, the facility is operated in a manner consistent with good practice for minimizing emissions and the source uses best efforts regarding planning, design, and operating procedures. We propose to find that the Texas SIP submittal and AOs do not address the feasibility or availability of any specific measures to minimize emissions during startup or shutdown. The only requirement is a work practice that consists of placing the ESP into service as soon as practicable or remove the ESP from service as late as possible. Nothing in the August 20, 2020 submittal indicates that technological or economic limitations prevent affected sources from using additional measures to limit emissions during planned MSS events that would address requirements to minimize emissions during such periods and be practically enforceable. This omission is particularly concerning, when planned MSS is an intentional, predictable event and within the control of the source. Because of the predictability of these events, alternative means of limiting emissions appear to be available such as use of natural gas or other cleaner burning fuels as auxiliary fuel to the maximum extent possible during startup operations until the required operating temperatures of the ESP are met and the ESP can be engaged. In addition, the submittal contains no analysis indicating that the use of another control device for PM emissions (for example, fabric filter baghouse) is not feasible, either.

Furthermore, to the extent that these sources already do utilize fuel oil or natural gas in the start-up process, there is no discussion in the SIP submission or requirement in the AOs that addresses the use of alternative fuels during startup and when coal combustion can begin with respect to operation of the ESPs. PM emissions are likely highest when coal is introduced into the boiler but the ESP has not yet been engaged. Utilizing natural gas (or fuel oil when natural gas is not an available fuel) to the maximum extent possible to bring equipment to temperature would serve to minimize emissions during startup and could allow for ESPs to reach necessary conditions for operation at the time coal is introduced into the boilers. In fact, EPA's Mercury and Air Toxics Standards (MATS) rule for power plants published February 16, 2012, and amended on May 7, 2024, contains additional requirements for particulate control for these units. Specific to periods of startup and shutdown, the MATS requirements include work practice standards that requires sources to have sufficient clean fuel capacity to startup and warm the facility to the point where the primary PM controls ( e.g., ESPs) can be brought online at the same time as the addition of the coal to the EGU.

3. Enforceability of the AELs

Clean Air Act Section 110(a)(2)(A) requires that SIPs include enforceable emission limits. As discussed previously, Texas stated that the AELs are designed to provide continuously effective limits on PM and opacity through all modes of operation, with chapter 111 requirements to apply during routine operations and the AELs to apply during MSS periods. SIP provisions, including emission limitations under Section 110(a)(2)(A), must be both legally and practically enforceable.

One EPA concern with the state's approach in the AOs is that it does not provide for adequate monitoring, recordkeeping and reporting. The monitoring and recordkeeping requirements in the AOs are not sufficient to ensure that all the data necessary for demonstrating compliance is recorded and available for review. The AOs require recordkeeping to identify periods of planned MSS, the opacity measured by the continuous opacity monitoring system (COMS) for the duration of the planned MSS activities, and the work practices followed during the planned MSS activities. However, they do not specifically identify and require recordkeeping of the parameters used to identify when startup or shutdown periods end or begin, such as temperature, unit load or ESP operating parameters, nor do they specifically require recordkeeping of the parameters monitored ( e.g. air heater outlet temperature, drum metal temperature, when solid fuel is burned) to determine when the ESP should be placed into or removed from service during these MSS periods. These specific records are necessary to determine compliance with the definitions of when startup and shutdown periods begin or end and compliance with the AO requirements on timing of when the ESPs are placed into or removed from service. In addition, the AOs only require facilities to provide records upon request by the TCEQ or any other air pollution control agency with jurisdiction. The AOs do not require sources to make any other periodic report related to compliance with the AO provisions. EPA cannot determine the enforceability of these rules due to these monitoring, recordkeeping, and reporting gaps. Thus, we are proposing disapproval and taking comment on whether there is other relevant information or analysis that would show that these limits are enforceable notwithstanding the lack of monitoring, recordkeeping, and reporting in the AOs.

EPA also proposes to find that the state's conditions in the AOs are too subjective to provide for practical enforceability. The AELs must be accompanied by appropriate methods and conditions to determine compliance that are fully enforceable (specifying clear, unambiguous, and measurable requirements for which compliance can be practicably determined) and replicable (the procedures for determining compliance which are sufficiently specific and non-subjective so that two independent entities applying the procedures would obtain the same result). Moreover, the work practices that apply during MSS events must be practically enforceable and it must be clear when the units are in MSS mode, and thus not subject to the otherwise applicable numerical limits specified in TAC Ch. 111.

a. Work Practices

The AOs contained in Texas' submittal all include a requirement that the sources must comply with the boiler and ESP manufacturer's operating procedures or the owner/operator's written Standard Operating Procedures (SOP) manual and to operate in a manner consistent with those procedures to minimize opacity.^[24] It is unclear what procedures should be followed if requirements in the SOP are inconsistent with the manufacturer's operating procedures. It is likely that the lengthy operating experience at these units has resulted in the refinement of operating procedures over the many ( print page 71243) years since the manufacturers designed the equipment and developed their recommended operating procedures. Furthermore, as the owner/operator's SOP can be modified over time, the required work practices cannot be considered permanent and enforceable. For a measure to be relied on as an emission limitation, it must be permanent which means it cannot be revised absent following the SIP revision process. Thus, the AOs need to contain more specific conditions to identify what steps must be followed to engage and operate the ESPs during these events.

As summarized in Table 2, the AOs vary in the specificity and conditions for when the ESPs should be placed into service. The Oklaunion AO specifies that the ESP should be placed into service during planned startups “once the outlet gas temperature to the ESP is greater than 300 °F.” This is a clear, unambiguous and measurable requirement and compliance can be verified by reviewing the outlet gas temperature and when the ESP is brought online. The AOs for the other seven facilities lack this level of specificity and are not practically enforceable because they require the ESP to be placed into service “as soon as practical.” For Gibbons Creek, Sam Seymour, Limestone and San Miguel, the ESP is to be placed into service as soon as practical after the air heater outlet temperature is within a specified 100 degree F range. It is unclear why a range is specified rather than a minimum temperature or if there are other measurable parameters, such as flow rate or drum metal temperature, that are being evaluated to determine when it would be “practical” to place the ESP into service. Similarly, the AO for Harrington specifies that the ESP be placed into service as soon as practical after solid fuel is being burned. It is unclear what other measurable parameters, such as ESP inlet temperature, is being evaluated to determine when it would be “practical” to place the ESP into service. Finally, for Martin Lake and Pirkey, there is no additional specification for when the ESP is placed into service other than “as soon as practical.”

The AOs also vary in the specificity and conditions for when the ESPs should be removed from service. For Harrington, the AO specifies that the ESP should be kept in service while the unit is burning solid fuel. For Sam Seymour, San Miguel, Oklaunion and Pirkey, the AOs provide no specificity to the conditions that determine when the ESP should be removed from service and only require that the ESP be removed from service “as late as possible.” For Gibbons Creek, Limestone and Martin Lake, the ESP is to be removed from service as late as possible after the air heater outlet temperature is within a large, specified temperature range. It is unclear why a range is specified rather than a minimum temperature or if there are other measurable parameters, such as flow rate or drum metal temperature, that are being evaluated to determine when the ESP should be removed from service. The AOs for these facilities lack specificity and are not practically enforceable.

Table 2—Summary of Requirements for Placing ESP Into and Removing ESP From Service

Facility	Requirements
Gibbons Creek	placing the ESP into service as soon as practical during planned startups or removing the ESP from service as late as possible during planned shutdowns, once the air heater outlet temperature is between 200 and 300 degrees F, but not longer than the durations during startups identified in Paragraph 12.A.
Harrington	When solid fuel is being burned, place the ESP into service as soon as practical during planned startups, but not longer than the durations identified in Paragraph 12.A. and keep the ESP in service while the unit is burning solid fuel.
Sam Seymour	placing the ESP into service as soon as practical during planned startups once the ESP inlet temperature (air heater outlet temperature) is between 150 and 250 degrees F and removing the ESP from service as late as possible during planned shutdowns, but not longer than the durations identified in Paragraph 12.A.
Limestone	placing the ESP into service as soon as practical during planned startups or removing the ESP from service as late as possible during planned shutdowns, once the air heater outlet temperature is between 200 and 300 degrees F, but not longer than the durations identified in Paragraph 12.A.1.
Martin Lake	placing the Boilers into service as soon as practical during planned startups, but not longer than the durations identified in Paragraph 12.A.1. During shutdown, Luminant will operate in a manner consistent with the Procedures to minimize opacity by removing the ESP from service as late as possible during planned shutdowns, once the air heater outlet temperature is between 180 and 260 degrees F, but not longer than the durations identified in Paragraph 12.A.2.
San Miguel	placing the ESP into service as soon as practical during planned startups once the prime inlet air heater is between 250 and 350 degrees F and removing the ESP from service as late as possible during planned shutdowns, but not longer than the durations identified in Paragraph 12.A.
Oklaunion	placing the ESP into service during planned startups once the outlet gas temperature to the ESP is greater than 300 °F, or removing the ESP from service as late as possible during planned shutdowns.
Pirkey	placing the ESP into service as soon as practical during planned startups or removing the ESP from service as late as possible during planned shutdowns.

b. Duration of Startup

The AO requirements for these facilities provide definitions for when the startup period ends that lack specificity such that it is not clear when the units are in startup mode and when they should be complying with the otherwise applicable numerical emission limitations in TAC Chapter 111. The definitions for when startup ends lack clear, unambiguous and measurable requirements by which compliance could be practicably determined. ( print page 71244)

Table 3—Startup Durations and Definitions in AOs

Facility	Duration of normal startup	Extended startup limitation	Startup begins	Startup ends
Gibbons Creek	2,880 minutes	600 hr/yr	forced draft fans start	boiler reaches the lowest sustainable load (LSL) and maintains that load (or greater load) for 60 consecutive minutes and ESP operations have been optimized.
Harrington	48 hours	300 hr/yr	Fans placed into service	unit reaches a sustained load of 150 megawatts.
Sam Seymour	48 hours	600 hr/yr	fuel oil igniters are started	Boiler is released to the LCRA Generation Desk for automatic dispatch.
Limestone	2,880 minutes	600 hr/yr	forced draft fans start	utility boiler reaches 400 megawatts (MW) and maintains that load (or greater load) for 60 consecutive minutes and ESP operations have been fully optimized.
Martin Lake	24 hours	900 hr/yr (combined on 3 units)	induced draft fans start operation	Boiler reaches stable load and the electrostatic precipitator (ESP) operation has been fully optimized.
San Miguel	2,880 minutes	600 hr/yr	induced draft fans start operation	lowest sustainable load (LSL) and maintains that load (or greater load) for 60 consecutive minutes and ESP operations have been fully optimized.
Oklaunion	2,880 minutes	18,000 minutes	fans are placed in service	lowest sustainable load on lignite for at least 60 consecutive minutes while coal is being fired.
Pirkey	2,880 minutes	18,000 minutes	fans are placed in service	lowest sustainable load on lignite for at least 60 consecutive minutes while coal is being fired.

The AOs for Gibbons Creek and San Miguel define the end of startup as when the “boiler reaches the lowest sustainable load (LSL) and maintains that load (or greater load) for 60 consecutive minutes and ESP operations have been optimized.” The AO for Martin Lake defines the end of startup as when the “[b]oiler reaches stable load and the electrostatic precipitator (ESP) operation has been fully optimized.” However, what constitutes the LSL or stable load is not specified in the requirements. In addition, the startup event does not end until the ESP operations have been optimized, but there is no additional specificity to determine when the ESP would be considered optimized. One can imagine that ESP operations with emissions above the Chapter 111 numerical levels would be considered non-optimized. For Martin Lake, the AO also fails to identify what constitutes a stable load so it is unclear what duration of operation at that load level is considered stable, such that the startup would be deemed to have ended. Similarly, the AOs for Oklaunion and Pirkey define the end of startup as “lowest sustainable load (LSL) on lignite for at least 60 consecutive minutes while coal is being fired” but do not define the LSL. We also note that it is not clear how the LSL “on lignite” applies to the Oklaunion unit that has historically burned subbituminous coal. While the AO for Harrington does define the necessary load level (150 MW) it also does not identify what duration of operation at that load level is to be considered “sustained.” The AO for Limestone specifies both the load level (400 MW) and the duration (60 minutes) but also requires that the ESP operations are “fully optimized” before the startup event is considered ended. The AO for Sam Seymour defines the end of startup as when the “the boiler is released to the LCRA generation desk for automatic dispatch.” The AO provides no additional details to identify the conditions such as sustained load to identify when the boiler would be released for dispatch to demonstrate that this condition is consistent with the goal of minimizing the duration of the event and startup emissions. In addition, while all other AOs define the beginning of startup as when the fans are placed into service, the AO for Sam Seymour defines the beginning of startup when the fuel oil igniters are placed in service. It is not clear what limits the source is required to meet when the fans are brought online before the igniters are placed into service.

c. Duration of Shutdown

The AO requirements for these facilities provide definitions for when the shutdown period begins that lack specificity such that it is not clear when the units are in shutdown mode or when they should be complying with the otherwise applicable numerical emission limitations in TAC Chapter 111. The definitions for when shutdown begins lack clear, unambiguous and measurable requirements by which compliance could be practicably determined.

Table 4—Shutdown Durations and Definitions in AOs

Facility	Duration of normal shutdown	Extended shutdown limitation	Shutdown begins	Shutdown ends
Gibbons Creek	600 minutes	600 hr/yr	load drops below LSL following dispatch request for a shutdown	When the boiler water circulating pump manifold temperature reaches 180 degrees Fahrenheit (F).
Harrington	36 hours		when the generator breaker is opened or at the point of main fuel no longer being fired in the boiler, whichever is earlier.	when the generator breaker is open and main fuel is no longer being fired in the boiler.
( print page 71245)
Sam Seymour	12 hours	600 hr/yr	when the LCRA Generation Desk releases control of the boiler to the plant for the purpose of a shutdown	temperature has been reached that allows personnel to enter the structure and conduct maintenance activities.
Limestone	2,880 minutes	600 hr/yr	when load drops below the lowest sustainable load (LSL) following dispatch request for a shutdown	when the drum metal temperature reaches 200 degrees F.
Martin Lake	24 hours	900 hr/yr (combined on 3 units)	when the ESP is partially or completely de-energized due to reaching its minimum operating temperature	when a temperature has been reached that allows personnel to enter the structure and conduct maintenance activities.
San Miguel	2,880 minutes	600 hr/yr	load drops below the LSL following the permit holder's request to dispatch for a shutdown	ends when the average lower drum metal temperature reaches 200 degrees Fahrenheit (F) or when the induced draft fans are removed from service by the plant operators.
Oklaunion	2,880 minutes		when the Boiler has dropped below the lowest sustainable load for at least 30 consecutive minutes	24 hours after combustion has ceased.
Pirkey	2,880 minutes		when the Boiler has dropped below the lowest sustainable load for at least 30 consecutive minutes	24 hours after combustion has ceased.

The duration of shutdown events are limited in the AOs to a specific amount of time, however, the time periods vary between the facilities from 10 hours to 48 hours. There is no discussion as to how the duration of the allowed shutdown period was determined nor justification for how a shutdown period lasting up to 48 hours is consistent with the goal of minimizing the duration of the event and associated emissions.

The AOs for Gibbons Creek, Limestone and San Miguel define the start of a shutdown as when the “load drops below LSL following dispatch request for a shutdown” and the AOs for Oklaunion and Pirkey define the start of a shutdown as when the boiler “has dropped below the lowest sustainable load for at least 30 consecutive minutes.” However, what constitutes the LSL is not specified in the requirements. For Martin Lake, the AO defines the start of shutdown as “when the ESP is partially or completely de-energized due to reaching its minimum operating temperature” but does not identify the minimum operating temperature. For Sam Seymour, the AO defines shutdown as beginning when the LCRA Generation Desk releases control of the boiler to the plant for the purpose of a shutdown but provides no additional details to identify the conditions such as sustained load to identify when the boiler would be released for shutdown. For Harrington, the AO defines shutdown as beginning when the generator breaker is opened or at the point of main fuel no longer being fired in the boiler, whichever is earlier, but provides no additional details to identify the conditions when the breaker is to be opened. In sum, to be legally and practically enforceable, the AOs should clearly define the moment when the requirements switch from compliance with 30 TAC 111.111(a)(1) and 30 TAC 111.153(b) to compliance with the alternative emission limitations that apply during shutdown in the AOs.

d. EPA's Conclusion on the Enforceability of AELs

In sum, to be legally and practically enforceable, the AOs should contain enforceable limitations on the duration of start-up and shutdown emissions and clearly define the moment when the requirements switch from compliance with the alternative emission limitations for such modes of operation in the AOs to compliance with 30 TAC 111.111(a)(1) and 30 TAC 111.153(b). These AO restrictions as written, however, are not practically enforceable. Instead, the AOs, due to various ambiguities as discussed above, are unclear as to the procedures an operator must follow to be in compliance and at what point in the startup or shutdown process, the facility must switch from compliance with the AO to compliance with 30 TAC 111.111(a)(1) and 30 TAC 111.153(b) as required for routine operation.

4. Planned Offline and Online Maintenance Activities

In addition to the work practices and operational limits for planned startup and shutdown, the AOs contain provisions specific to planned online or offline maintenance activities, such as boiler general maintenance, de-slagging, combustion optimization, and flue gas conditioning.^[25] However, unlike the provisions for startup and shutdown, the AOs do not include any work practices that the sources are required to apply during these periods. For these activities, the AOs “authorize” periods of opacity greater than 20% for a number of hours per year ( e.g., 535 hrs/year for each unit at Martin Lake). The only ostensible requirement during maintenance periods appears to be that the source operate the boiler and its ESP in accordance with good air pollution control practices, safe operating practices, and protection of the facility and associated air pollution control equipment. The generic general duty that an owner or operator shall operate a source consistent with safety and good air pollution control practices for minimizing emissions is not sufficient to identify what these specific practices might be across the range of maintenance activities to which the AOs apply, and thus such general duty clauses are not practically enforceable as a limitation on emissions during these activities.^[26] The AOs and SIP submission contain no discussion of the potential emissions from these activities, or consideration of other forms of alternative emission limitations ( print page 71246) such as alternative numerical opacity limits that could potentially apply during these maintenance periods that would provide for a quantifiable and more practically enforceable limitation. Furthermore, EPA notes that the AOs contain no limitations as to the duration or frequency of individual events, the result being that it is possible that no opacity limitation could apply for a period of several hundred hours.

As stated in EPA's June 12, 2015 SSM policy, states may not create SIP provisions that contain automatic or discretionary exemptions from otherwise applicable emission limitations during periods such as “maintenance,” “load change,” “soot blowing,” “on-line operating changes” or other similar normal modes of operation. Like startup and shutdown, the EPA considers all of these to be modes of normal operation at a source, for which the source can be designed, operated and maintained in order to meet applicable emission limitations and during which the source should be expected to control and minimize emissions. Excess emissions that occur during planned and predicted periods should be treated as violations of applicable emission limitations. Accordingly, exemptions for emissions during these periods of normal source operation are not consistent with CAA requirements.

It may be appropriate for an air agency to establish an alternative numerical limitation or other form of control measure that applies during these modes of source operation, as for startup and shutdown events, but any such alternative emission limitation should be developed using the same criteria that the EPA recommends for alternative emission limitations applicable during startup and shutdown. Similarly, any SIP provision that includes an emission limitation for sources that includes alternative emission limitations applicable to modes of operation such as “maintenance,” “load change,” “soot blowing” or “on-line operating changes” must also meet the applicable level of stringency for that type of emission limitation and be practically and legally enforceable.^[27] So EPA finds that the general duty provisions that apply during Maintenance activities in the AOs are not practically enforceable and thus cannot be approved.

V. Proposed Action

For the reasons discussed in this notice, the EPA is proposing to disapprove a revision to the Texas SIP submitted by TCEQ on August 20, 2020 (concerning opacity and PM emissions during planned MSS activities for certain EGU sources equipped with ESPs as the PM control device). These EGUs are the Southwestern Electric Power Company (SWEPCO) H.W. Pirkey Power Plant; the Lower Colorado River Authority (LCRA) Sam Seymour Fayette Power Project; the Luminant Generation Company, LLC Martin Lake Steam Electric Station; the NRG Texas Power, LLC Limestone Electric Generating Station; the San Miguel Electric Cooperative, Inc. San Miguel Plant; the Southwestern Public Service Company (SPS) Harrington Station; the Texas Municipal Power Agency (TMPA) Gibbons Creek Steam Electric Station; and the Public Service Company of Oklahoma (PSCO) Oklaunion Power Station.

The effect of this disapproval, if finalized, is that the Agreed Orders will not be incorporated into the SIP. There will be no sanctions or FIP clocks started by this action if finalized.

VI. Environmental Justice Considerations

Information on Executive Order 12898 (Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations, 59 FR 7629, February 16, 1994) and how EPA defines environmental justice (EJ) can be found in the section, below, titled “VII. Statutory and Executive Order Reviews.” For informational and transparency purposes only, the EPA is including additional analysis of environmental justice associated with this proposed action for the purpose of providing information to the public.

EPA conducted screening analyses using EJSCREEN, an environmental justice mapping and screening tool that provides EPA with a nationally consistent dataset and approach for combining various environmental and demographic indicators.^[28] The EJSCREEN tool presents these indicators at a Census block group (CBG) level or a larger user-specified “buffer” area that covers multiple CBGs.^[29] An individual CBG is a cluster of contiguous blocks within the same census tract and generally contains between 600 and 3,000 people. EJSCREEN is not a tool for performing in-depth risk analysis, but is instead a screening tool that provides an initial representation of indicators related to environmental justice and is subject to uncertainty in some underlying data ( e.g., some environmental indicators are based on monitoring data which are not uniformly available; others are based on self-reported data).^[30] To help mitigate this uncertainty, we have summarized EJSCREEN data within larger “buffer” areas covering multiple block groups and representing the average resident within the buffer areas surrounding the sources. We present EJSCREEN environmental indicators to help screen for locations where residents may experience a higher overall pollution burden than would be expected for a block group with the same total population. These indicators of overall pollution burden include estimates of ambient particulate matter (PM_2.5 ), ozone, nitrogen dioxide, and diesel particulate matter concentration, a score for traffic proximity and volume, percentage of pre-1960 housing units (lead paint indicator), and scores for proximity to Superfund sites, risk management plan (RMP) sites, and hazardous waste facilities.^[31] EJSCREEN also provides information on demographic indicators, including percent low-income, unemployment, communities of color, linguistic isolation, and education.

The EPA prepared EJSCREEN reports covering a buffer area of approximately 6-mile radius around each affected EGU. Tables 5 and 6 present a summary of results from the EPA's screening-level analysis for the areas surrounding the affected EGUs in Texas compared to the U.S. as a whole. The full, detailed EJSCREEN report is provided in the docket for this rulemaking. ( print page 71247)

Table 5—EJSCREEN Analysis Summary for Affected EGU Facilities Part 1

Variables	Values for buffer areas (radius) for each affected EGU and the U.S. (percentile within U.S. where indicated)
	Fayette	Gibbons Creek	Harrington	Pirkey	U.S.
Pollution Burden Indicators:
Particulate matter (PM 2.5 ), annual average	8.32 μg/m3 (56%ile)	8.38 μg/m3 (58%ile)	5.91 μg/m3 (5%ile)	8.89 μg/m3 (72%ile)	8.45 μg/m3 (—)
Ozone, annual average of the top ten 8-hour daily maximums	61.1 ppb (53%ile)	63.1 ppb (63%ile)	59.6 ppb (46%ile)	56.3 ppb (29%ile)	61.8 ppb (—)
Nitrogen dioxide, annual average	4.9 ppb (22%ile)	4.3 ppb (17%ile)	7.7 ppb (51%ile)	3.7 ppb (11%ile)	7.8 ppb (—)
Diesel particulate matter	0.0603 μg/m3 (12%ile)	0.0553 μg/m3 (10%ile)	0.172 μg/m3 (55%ile)	0.105 μg/m3 (30%ile)	0.191 μg/m3 (—)
Toxic releases to air score *	74 (21%ile)	82 (22%ile)	260 (36%ile)	10000 (93%ile)	4,600 (—)
Traffic proximity and volume score *	27,000 (8%ile)	12,000 (5%ile)	520,000 (40%ile)	110,000 (18%ile)	1,700,000 (—)
Lead paint (percentage pre-1960 housing)	0.26% (54%ile)	0.037% (23%ile)	0.44% (70%ile)	0.17% (45%ile)	0.3% (—)
Superfund proximity score *	0 (0%ile)	0 (0%ile)	0.015 (56%ile)	0.0065 (56%ile)	0.39 (—)
RMP proximity score *	0.12 (36%ile)	0.012 (28%ile)	1.4 (87%ile)	0.19 (43%ile)	0.57 (—)
Hazardous waste proximity score *	0 (0%ile)	0 (0%ile)	0.45 (32%ile)	0.096 (17%ile)	3.5 (—)
Underground storage tank proximity score *	0.073 (32%ile)	0.022 (29%ile)	0.82 (49%ile)	0.27 (39%ile)	3.6 (—)
Wastewater discharge score *	2,400 (80%ile)	64 (51%ile)	0.57 (19%ile)	31 (45%ile)	700,000 (—)
Drinking water noncompliance, points	8.5 (92%ile)	0.15 (74%ile)	0.97 (77%ile)	0.87 (77%ile)	2.2 (—)
Demographic Indicators:
People of color population	15% (30%ile)	19% (36%ile)	72% (79%ile)	26% (44%ile)	40% (—)
Low-income population	15% (27%ile)	17% (32%ile)	55% (86%ile)	29% (53%ile)	30% (—)
Unemployment rate	2% (36%ile)	3% (44%ile)	4% (51%ile)	4% (56%ile)	6% (—)
Linguistically isolated population	0% (0%ile)	2% (62%ile)	10% (85%ile)	7% (79%ile)	5% (—)
Population with less than high school education	4% (30%ile)	10% (58%ile)	35% (94%ile)	12% (64%ile)	11% (—)
Population under 5 years of age	3% (34%ile)	3% (34%ile)	7% (70%ile)	6% (62%ile)	5% (—)
Population over 64 years of age	31% (89%ile)	17% (54%ile)	11% (29%ile)	11% (27%ile)	18% (—)
* The traffic proximity and volume indicator is a score calculated by daily traffic count divided by distance in meters to the road. The Superfund proximity, RMP proximity, and hazardous waste proximity indicators are all scores calculated by site or facility counts divided by distance in kilometers. The underground storage tank proximity indicator is the weighted count within a 1,500-foot block group. The toxic releases to air indicator is the modeled toxicity-weighted concentration. The wastewater discharge indicator is the modeled toxicity-weighted concentrations divided by distance in meters.

Table 6—EJSCREEN Analysis Summary for Affected EGU Facilities Part 2

Variables	Values for buffer areas (radius) for each affected EGU and the U.S. (percentile within U.S. where indicated)
	Limestone	Martin Lake	Oklaunion	San Miguel	U.S.
Pollution Burden Indicators:
Particulate matter (PM 2.5 ), annual average	8.13 μg/m3 (49%ile)	8.8 μg/m3 (69%ile)	6.94 μg/m3 (17%ile)	8.38 μg/m3 (58%ile)	8.45 μg/m3 (—)
Ozone, annual average of the top ten 8-hour daily maximums	61 ppb (53%ile)	56.9 ppb (32%ile)	57.2 ppb (33%ile)	61.7 ppb (56%ile)	61.8 ppb (—)
Nitrogen dioxide, annual average	3.7 ppb (11%ile)	3.2 ppb (8%ile)	3.6 ppb (11%ile)	2.9 ppb (6%ile)	7.8 ppb (—)
Diesel particulate matter	0.0574 μg/m3 (11%ile)	0.0572 μg/m3 (11%ile)	0.0496 μg/m3 (8%ile)	0.0384 μg/m3 (4%ile)	0.191 μg/m3 (—)
Toxic releases to air score *	320 (39%ile)	9400 (92%ile)	32 (14%ile)	92 (23%ile)	4,600 (—)
Traffic proximity and volume score *	12,000 (5%ile)	9,900 (4%ile)	59,000 (13%ile)	28,000 (8%ile)	1,700,000 (—)
Lead paint (percentage pre-1960 housing)	0.061% (29%ile)	0.12% (38%ile)	0.51% (74%ile)	0.08% (32%ile)	0.3% (—)
Superfund proximity score *	0 (0%ile)	0.014 (56%ile)	0 (0%ile)	0 (0%ile)	0.39 (—)
RMP proximity score *	0.14 (39%ile)	0.18 (42%ile)	0.32 (53%ile)	0.084 (30%ile)	0.57 (—)
Hazardous waste proximity score *	0.058 (15%ile)	0.055 (15%ile)	0 (0%ile)	0 (0%ile)	3.5 (—)
Underground storage tank proximity score *	0.022 (29%ile)	0.18 (36%ile)	0.11 (34%ile)	0.000039 (26%ile)	3.6 (—)
( print page 71248)
Wastewater discharge score *	52 (50%ile)	50 (49%ile)	0.35 (18%ile)	14 (38%ile)	700,000 (—)
Drinking water noncompliance, points	2.7 (87%ile)	9.9 (92%ile)	2.2 (87%ile)	0.86 (77%ile)	2.2 (—)
Demographic Indicators:
People of color population	21% (37%ile)	33% (51%ile)	43% (60%ile)	44% (61%ile)	40% (—)
Low-income population	33% (60%ile)	28% (52%ile)	41% (72%ile)	15% (29%ile)	30% (—)
Unemployment rate	3% (45%ile)	4% (55%ile)	5% (62%ile)	9% (79%ile)	6% (—)
Linguistically isolated population	1% (59%ile)	0% (56%ile)	4% (71%ile)	0% (57%ile)	5% (—)
Population with less than high school education	11% (60%ile)	8% (50%ile)	30% (91%ile)	29% (91%ile)	11% (—)
Population under 5 years of age	4% (47%ile)	9% (80%ile)	5% (54%ile)	0% (13%ile)	5% (—)
Population over 64 years of age	27% (83%ile)	17% (53%ile)	17% (55%ile)	35% (92%ile)	18% (—)
* See Table 5 footnote.