2023-14645. Air Plan Approval; Pennsylvania; Liberty Borough Area Second 10-Year PM10 Limited Maintenance Plan

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to approve the Liberty Borough area second 10-year maintenance plan submitted by the Commonwealth of Pennsylvania Department of Environmental Protection (PADEP or Commonwealth) on behalf of the Allegheny County Health Department (ACHD). This plan addresses the second 10-year maintenance period after redesignation for particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM₁₀). A limited maintenance plan (LMP) is used to meet the Clean Air Act (CAA or the Act) requirements for formerly designated nonattainment areas that meet certain qualification criteria. EPA is proposing to determine that ACHD's second maintenance plan meets applicable CAA requirements. The plan relies upon control measures contained in the attainment plan and the first 10-year maintenance plan and the determination that the Liberty Borough area currently monitors PM₁₀ levels well below the PM₁₀ national ambient air quality standards (NAAQS or standard).

DATES:

Written comments must be received on or before August 11, 2023.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA–R03–OAR–2023–0219 at www.regulations.gov, or via email to [e-mail]. For comments submitted at Regulations.gov, follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from Regulations.gov. For either manner of submission, EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be confidential business information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. EPA will generally not consider comments or comment contents located outside of the primary submission ( i.e., on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit www.epa.gov/​dockets/​commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT:

Ellen Schmitt, Planning & Implementation Branch (3AD30), Air & Radiation Division, U.S. Environmental Protection Agency, Region III, Four Penn Center, 1600 John F. Kennedy Boulevard, Philadelphia, Pennsylvania 19103. The telephone number is (215) 814–5787. Ms. Schmitt can also be reached via electronic mail at [e-mail].

SUPPLEMENTARY INFORMATION:

On July 21, 2021, EPA received from PADEP, on behalf of ACHD, a revision to the Commonwealth's state implementation plan (SIP) for the Liberty Borough area.^[1] The Liberty Borough area is comprised of the Boroughs of Liberty, Lincoln, Port Vue, and Glassport and the City of Clairton in Allegheny County, Pennsylvania. This action is expected to ensure that the Commonwealth of Pennsylvania meets CAA requirements. There is no information on the record indicating that this action is expected to have disproportionately high or adverse human health or environmental effects on a particular group of people.

I. Background

On July 1, 1987, EPA promulgated two primary standards for PM₁₀ : A 24-hour standard of 150 micrograms per cubic meter (µg/m^[3] ) and an annual standard of 50 µg/m^[3] . EPA also promulgated secondary PM₁₀ standards that were identical to the primary standards.^[2] Effective December 18, 2006, EPA revoked the annual PM₁₀ standards but retained the 24-hour standards.^[3] In this document, references to the PM₁₀ NAAQS or PM₁₀ standard refer to the 24-hour average standard of 150 µg/m³ , unless otherwise noted. Because they are identical, we refer to the primary and secondary 24-hour standards using the single term, NAAQS.

On November 15, 1990, amendments to the CAA were enacted, and pursuant to section 107(d)(4)(B) of the Act, the Liberty Borough area was designated nonattainment by operation of law.^[4] To support an attainment demonstration, ACHD and the Commonwealth submitted to EPA several SIP revisions that included permanent and enforceable pollution controls in the Liberty Borough area, resulting in reduced ambient air quality concentrations.^[5]

On September 8, 1998 (63 FR 47493), EPA finalized a determination that the Liberty Borough area had attained the PM₁₀ NAAQS based on 1995–1997 air quality data. In that same action, EPA approved the attainment demonstration and contingency measures for the area, concluding that the Liberty Borough area attainment plan was sufficient to help the Liberty Borough area attain and maintain the NAAQS.

On October 28, 2002, the Commonwealth, on behalf of ACHD, submitted to EPA a redesignation request and maintenance plan for the Liberty Borough area. EPA redesignated the Liberty Borough area from nonattainment to attainment for the PM₁₀ NAAQS and approved the maintenance plan for this first 10-year maintenance period on September 11, 2003 (68 FR 53515).^[6] The first 10-year maintenance period ended in 2013 and the second 10-year maintenance plan, which is the subject of this proposed rulemaking, extends through 2023.

Since the redesignation request in 2002, ACHD has been operating an ambient PM₁₀ monitoring network with monitors at four sites within the Liberty Borough area, in accordance with 40 Code of Federal Register (CFR) part 58. The Liberty Borough area PM₁₀ monitors are the Lincoln monitor (air quality system (AQS) site ID 42–003–7003), the Liberty monitor (AQS site ID 42–003–0064),^[7] the Glassport monitor (AQS site ID 42–003–3006), and the Clairton monitor (AQS site ID 42–003–3007). The Lincoln, Liberty, and Glassport monitors are Federal Equivalent Method (FEM) continuous monitors for PM₁₀ . Liberty is also considered a multi-pollutant site with monitors for other air pollutants at the same site, including a Federal Reference Method (FRM) filter-based monitor for PM₁₀. The Clairton site has an FRM filter-based monitor.

II. Limited Maintenance Plan Option for PM 10 Areas

A. Requirements for the Limited Maintenance Plan Option

Section 175A of the CAA sets forth the elements for maintenance plans. Under section 175A, a state or locality must submit a maintenance plan to demonstrate continued attainment of the applicable NAAQS for at least ten years after an area is redesignated to attainment. Eight years into the first maintenance period, the applicable state or local agency must submit a second maintenance plan demonstrating that the area will continue to attain for the following 10-year period. On September 4, 1992, EPA issued guidance on the content of a maintenance plan (Memorandum from John Calcagni, Director, Air Quality Management Division, entitled “Procedures for Processing Requests to Redesignate Areas to Attainment,” (Calcagni Memo)).^[8] The Calcagni Memo states that a maintenance plan should include the following provisions: (1) an attainment emissions inventory; (2) a maintenance demonstration showing maintenance for 10 years; (3) a commitment to maintain the existing monitoring network; (4) verification of continued attainment; and (5) a contingency plan to prevent or correct future violations of the NAAQS.

On August 9, 2001, EPA issued guidance on streamlined maintenance plan provisions for certain moderate PM₁₀ nonattainment areas (see Memorandum from Lydia Wegman, Director, Air Quality Standards and Strategies Division, entitled “Limited Maintenance Plan Option for Moderate PM₁₀ Nonattainment Areas” (LMP Option Memo).^[9] The LMP Option Memo contains a statistical demonstration air agencies can use to show that areas are meeting certain air quality criteria with a high degree of probability, and therefore will maintain the standard ten years into the future. By providing this statistical demonstration, EPA can consider the maintenance demonstration requirement of the CAA to be satisfied for the moderate PM₁₀ nonattainment area meeting these air quality criteria. If the tests described in section IV of the LMP Option Memo are met, EPA will treat that as a demonstration that the area will maintain the NAAQS. Consequently, the state or local agency is not required to submit in its SIP certain future year emission inventories for these areas nor some of the standard transportation conformity analyses.

To qualify for the LMP option, the applicable state or local agency must demonstrate that the area meets the following criteria. First, the area should have attained the PM₁₀ NAAQS. Second, the most recent five years of air quality data at all monitors in the area, referred to as the 24-hour average design value, should be at or below 98 µg/m³ . Third, the applicable state or local agency should expect only limited growth in on-road motor vehicle PM₁₀ emissions and should have passed a motor vehicle regional emissions analysis test. Lastly, the LMP Option Memo identifies core provisions that must be included in all limited maintenance plans. These provisions include an attainment year emissions inventory, assurance of continued operation of an EPA-approved air quality monitoring network, and contingency provisions.

B. Conformity Under the Limited Maintenance Option

The transportation conformity rule and the general conformity rule (set forth in 40 CFR parts 51 and 93) apply to nonattainment areas and maintenance areas covered by an approved maintenance plan. Under either conformity rule, an acceptable method of demonstrating that a Federal action conforms to the applicable SIP is to demonstrate that expected emissions from the planned action are consistent with the on-road mobile emissions budget for the area.

While EPA's LMP option does not exempt an area from the need to affirm conformity, it explains that the area may demonstrate conformity without conforming to an emissions budget. Under the LMP option, emissions budgets are treated as essentially not constraining for the length of the maintenance period because it is unreasonable to expect that the qualifying areas would experience so much on-road mobile source emissions growth in that period that a violation of the PM₁₀ NAAQS would result. For transportation conformity purposes, EPA would conclude that emissions in these areas need not be capped for the maintenance period and therefore a regional emissions analysis would not be required.

While areas with maintenance plans approved under the LMP option are not subject to the budget test (see 40 CFR 93.109(e)), those areas remain subject to the other transportation conformity requirements of 40 CFR part 93, subpart A. Thus, the metropolitan planning organization (MPO) in the area or the state must document and ensure that:

a. Transportation plans and projects provide for timely implementation of SIP transportation control measures (TCMs) in accordance with 40 CFR 93.113;

b. Transportation plans and projects comply with the fiscal constraint element as set forth in 40 CFR 93.108;

c. The MPO's interagency consultation procedures meet the applicable requirements of 40 CFR 93.105;

d. Conformity of transportation plans is determined no less frequently than every four years, and conformity of plan amendments and transportation projects is demonstrated in accordance with the timing requirements specified in 40 CFR 93.104;

e. The latest planning assumptions and emissions model are used as set forth in 40 CFR 93.110 and 40 CFR 93.111;

f. Projects do not cause or contribute to any new localized carbon monoxide or particulate matter violations, in accordance with procedures specified in 40 CFR 93.123; and

g. Project sponsors and/or operators provide written commitments as specified in 40 CFR 93.125.

If EPA approves the second 10-year LMP, the Liberty Borough area will continue to be exempt from performing a regional emissions analysis, but must meet project-level conformity analyses as well as the transportation conformity criteria described previously.

III. Review of the SIP Submittal

A. Qualifying for the Limited Maintenance Plan Option

As discussed in Section II.A. of this preamble, the LMP Option Memo outlines the requirements for an area to qualify for an LMP. First, the area should be attaining the PM₁₀ NAAQS. The PM₁₀ NAAQS is attained when the expected number of days per calendar year with a 24-hour average concentration above 150 µg/m^[3] is equal to or less than one (40 CFR 50.6). EPA has evaluated recent ambient air quality data and the Liberty Borough area continues to attain the 24-hour standard for PM₁₀ , not exceeding the standard on any day at any of the four monitoring sites for over ten years (2011–2021).^[10] Table 1, in this document, shows the highest and second highest 24-hour PM₁₀ concentrations measured at the five Liberty Borough area monitors from 2011–2021, all of which are consistently below the NAAQS of 150 µg/m³ .

Table 1—Highest/Second Highest Annual 24-Hour PM ₁₀ Concentrations (µ g / m³ ) at the Clairton, Glassport, Liberty, and Lincoln Monitors, 2011–2021 ^a

Year	Clairton (FRM)	Glassport (FEM)	Liberty (FEM)	Liberty (FRM)	Lincoln (FEM)
2011	37/37	83/74	70/70	93/72	115/94
2012	34/32	91/72	71/66	73/72	84/75
2013	25/25	60/57	49/48	59/47	76/65
2014	39/32	64/52	63/50	64/55	70/56
2015	41/34	91/56	78/61	64/59	85/79
2016	46/27	68/49	65/63	70/62	93/84
2017	29/28	68/68	87/58	106/61	108/93
2018	27/21	57/48	54/53	50/50	83/67
2019	26/22	105/86	74/68	72/71	75/57
2020	31/24	46/45	49/48	39/38	73/71
2021	24/24	58/54	57/54	Shutdown 11/11/20	Shutdown 12/31/20
a  Data provided by EPA's Air Quality System (AQS).

The second criteria for the PM₁₀ LMP option is that the 24-hour average design value for the most recent five years of monitoring data must be at or below 98 µg/m^[3] .^[11] ACHD calculated the design values for the Liberty Borough area as the 3-year averages of the yearly second-highest 24-hour PM₁₀ concentration at each monitoring site, which was provided through 2020 in Table A–10 in its July 2021 LMP SIP submittal.^[12 13] EPA looked at the most recent five years of 3-year averages from that table (2016–2020) ^[14] and determined that the Lincoln monitor showed the uppermost second-highest design value with a value of 85 µg/m³ , well below the LMP Option Memo threshold of 98 µg/m³ .

EPA used the table look-up procedure as one of the acceptable approaches for determining appropriate 24-hour PM₁₀ design concentrations.^[15] The Agency calculated the 5-year average design value for the Liberty Borough based on PM₁₀ monitoring data from 2017 through 2021, the most recently available certified data from the Liberty Borough area monitoring sites.

For the tabular approach for the 24-hour PM₁₀ standard, EPA first determined the total number of 24-hour PM₁₀ concentrations at each monitoring site and the number of available 24-hour concentrations to determine which of the highest concentrations is chosen as the design concentration. Table 2, in this document, which is the tabular estimation taken from EPA's PM₁₀ SIP Development Guideline, specifies which rank value corresponds to the probable annual maximum value.^[16]

Table 2—Tabular Estimation of PM ₁₀ Design Concentrations

Number of daily values	Data point used for design concentration
≤ 347	Highest Value.
348–695	Second Highest Value.
696–1042	Third Highest Value.
1043–1390	Fourth Highest Value.
1391–1738	Fifth Highest Value.
1739–2086	Sixth Highest Value.
2087–2434	Seventh Highest Value.
>2345	Eighth Highest Value.

With multiple monitoring sites, the highest PM₁₀ concentrations at each site would have to be considered and a design concentration established for each location and the “controlling” design concentration for an area with multiple sites would be the highest values. For routine model applications with five full years of 24-hour concentration estimates, the PM₁₀ design concentration of critical interest becomes the highest of the sixth-highest concentrations for the entire receptor network.

Tables 3, 4, and 5, in this document, provide the average design values based on the tabular estimation method for the three Liberty Borough area monitors that remained in operation through 2021. EPA averaged the design values two ways for each of these monitors. First, we conducted the 5-year design value by looking at the five years as a whole set. For example, we counted the number of samples that occurred between January 1, 2017 and December 31, 2021. Then, as guided by in Table 2, in this document, we found the appropriate data point from amongst the 5-year data set.

Alternatively, EPA also conducted the same process of reviewing the number of samples and finding the appropriate data point, but with each 3-year design value period for the following five years: 2017, 2018, 2019, 2020, and 2021. We then calculated the average of the five 3-year design values. The results can be found in Tables 3 through 5, in this document.

Table 3—PM ₁₀ Average Design Value for the Clairton Monitor (FRM), Tabular Estimation Method

Design value years	Number of daily samples	Data point used for design concentration	Limited maintenance plan  average design value (µg/m3 )
2017–2021	290	Highest Value	31
2015–2017	167	Highest Value	46	36.6
2016–2018	170	Highest Value	46
2017–2019	173	Highest Value	29
2018–2020	175	Highest Value	31
2019–2021	177	Highest Value	31

Table 4—PM ₁₀ Average Design Value for the Glassport (FEM) Monitor, Tabular Estimation Method

Design value years	Number of daily samples	Data point used for design concentration	Limited maintenance plan  average design value (µg/m3 )
2017–2021	1797	Sixth Highest Value	59
2015–2017	1084	Fourth Highest Value	68	62.6
2016–2018	1082	Fourth Highest Value	59
2017–2019	1080	Fourth Highest Value	68
2018–2020	1079	Fourth Highest Value	59
2019–2021	1080	Fourth Highest Value	59

Table 5—PM ₁₀ Average Design Value for the Liberty (FEM) Monitor, Tabular Estimation Method

Design value years	Number of daily samples	Data point used for design concentration	Limited maintenance plan  average design value (µg/m3 )
2017–2021	1799	Sixth Highest Value	57
2015–2017	1051	Fourth Highest Value	63	59.6
2016–2018	1055	Fourth Highest Value	62
2017–2019	1071	Fourth Highest Value	60
2018–2020	1083	Fourth Highest Value	56
2019–2021	1086	Fourth Highest Value	57

As shown in Tables 3 through 5, in this document, all of the average design values determined using the table look-up method through 2021 are below the LMP option design value criteria of 98 µg/m³ . The highest average values obtained using EPA's method were at the Glassport monitor (as seen in Table 4 in this document), but both methods of calculating average design value provided results well below 98 µg/m³ . Therefore, EPA finds that the Liberty Borough area meets the design value criteria outlined in the LMP Option Memo.

Third, the area must meet the motor vehicle regional emissions analysis test described in the LMP Option Memo. The Commonwealth and ACHD submitted an analysis showing that growth of on-road mobile PM₁₀ emissions was minimal and would not threaten the assumption of maintenance that underlies the LMP policy. Using EPA's methodology, ACHD calculated total projected growth in on-road motor vehicle PM₁₀ emissions through 2031 ^[17] for the Liberty Borough area. This calculation is derived using Attachment B of the EPA's LMP Option Memo, where the projected percentage increase in vehicle miles traveled over the next ten years (VMT_pi) is multiplied by the on-road mobile portion of the attainment year inventory (DV_mv), including re-entrained road dust. This test is met when (VMT_pi × DV_mv) plus the design value for the most recent five years of quality assured data is below the margin of safety (MOS) for the relevant PM₁₀ standard in µg/m³ for a given area. This MOS value can be 98 µg/m³ , as ACHD chose to use, or a site-specific value computed from data collected at the site of interest using methods outlined in Attachment A of the LMP Option Memo.

ACHD used the motor vehicle regional analysis methodology with the average design value of 85 µg/m^[3] for the Liberty Borough area using the highest 3-year design value for 2015, 2016, and 2017. Additionally, for the motor vehicle regional analysis calculation, ACHD used a VMT_pi of 3.6 percent and a DV_mv of 4.3 µg/m^[3] . ACHD's motor vehicle regional emissions test analysis indicated a resulting value of 85.2 µg/m^[3] , which is below the MOS of 98 µg/m^[3] .^[18] EPA reviewed the calculations in the Liberty Borough area LMP SIP submission and the Agency proposes to find that the area meets the motor vehicle regional emissions analysis test.

As described previously, the Liberty Borough area PM₁₀ maintenance area meets the qualification criteria set forth in the LMP Option Memo and accordingly qualifies for the LMP option. To ensure these requirements continue to be met, ACHD commits to recalculating the design value on an annual basis through the end of 2023. The motor vehicle emissions test will also be recalculated annually using the updated maximum design value over the past five years for the area. If the test cannot be met ( i.e., the equation shows a value above the MOS), ACHD will submit a full maintenance plan for the area according to CAA 175A requirements within one year after the determination of the updated design values.

B. Attainment Inventory

Pursuant to the LMP Option Memo, an LMP SIP submission should include an emissions inventory, which can be used to demonstrate attainment of the relevant NAAQS. The inventory should represent emissions during the same 5-year period associated with air quality data used to determine whether the area meets the applicability requirements of the LMP option.

The redesignation request and first 10-year maintenance plan for the Liberty Borough area included a 1994 emissions inventory.^[19] The inventory focused on stationary sources in Allegheny County and surrounding counties, as well as wood burning, public roads, and fugitive sources without permitted limits. Since the initial maintenance plan and redesignation request, many of the sources have lowered their permitted emissions rates of PM₁₀ due to the installation of controls, equipment upgrades, fuel switches, as well as other factors, including shutting down. In the LMP SIP submittal, ACHD noted several of the emission reductions from over the years, including several modifications at the United States Steel Corporation (USS) Mon Valley Works (MVW) Clairton Plant,^[20] representing an overall reduction of 268 tons per year (tpy) of PM₁₀ from the previous allowable inventory, as well as shutdowns at several large sources outside of the area that provided over 3,000 tpy of PM₁₀ reductions from the previous allowable inventory.^[21]

According to ACHD, the total reductions in permitted allowable rates since the initial redesignation request represent an almost 13,000 tpy overall reduction of PM₁₀ allowable emissions. This is approximately 55 percent lower than the allowable inventory from the first 10-year maintenance period.

To illustrate the current emissions in the Liberty Borough area, ACHD's current LMP SIP submission included an inventory of actual emissions using base year 2017. ACHD refers to this as the “Liberty Borough area maintenance emissions inventory.” ACHD used the 2017 national emissions inventory (NEI), which was the most recent comprehensive inventory that was available to ACHD at the time it was preparing the LMP for the Liberty Borough area. The 2017 NEI is representative of the typical emissions during which continued attainment has occurred since the end of the Liberty Borough area's first 10-year maintenance plan period in 2013.^[22] Table 6 includes the following four main categories from the 2017 inventory: Stationary point sources, area (nonpoint) sources, nonroad mobile sources, and on-road mobile sources.^[23] Stationary point sources contribute the largest amount of primary PM₁₀ emissions (82 percent) and its precursors (87 percent),^[24] within the Liberty Borough area. Among all the stationary sources in the Liberty Borough area, the USS MVW Clairton Plant contributes the most PM₁₀ primary and precursor emissions.

Table 6—Liberty Borough Area 2017 Emissions Inventory

[tpy] ^a

Liberty borough area	PM 10c	SO 2	NO X	VOCs	NH 3
Stationary Point Sources b	877.93	1,129.86	2,626.26	184.45	118.87
Area (Nonpoint) Sources d	175.07	4.01	95.80	275.23	9.85
Nonroad Mobile Sources d	4.33	0.10	37.83	33.19	0.09
Onroad Mobile Sources d	10.48	0.83	94.11	57.41	3.60
Total	1,067.81	1,134.80	2,854.00	550.28	132.41
a Taken from ACHD's PM10 LMP for the Liberty Borough area.
b Inventoried stationary sources within the Liberty Borough area include USS MVW Clairton Plant, Tech Met, Inc., Koppers Inc., and AKJ Steel Industries.
c Total primary PM 10 .
d Since NEI emissions are located to the county-level, ACHD used the U.S. Census's estimates for the 2017 population percentage of the Liberty Borough area to scale down emissions from the total Allegheny County population.

1. Expected Emissions

In the July 21, 2021, second maintenance plan SIP submission, ACHD noted that there is little growth in emissions expected for the Liberty Borough area through the end of the maintenance period in 2023. ACHD attributes the lack of potential for emissions growth through 2023 to several factors, including a 2019 settlement agreement and order with USS MVW Clairton Plant that requires the facility to conduct upgrades and work practice enhancements through 2023.^[25] ACHD provides additional information in their LMP submission regarding other programs and actions that will help to maintain or lower PM₁₀ emissions in the Liberty Borough area.

2. PM₁₀ SIP Controls

In accordance with the CAA, areas seeking to use the LMP approach for maintenance must have an attainment plan that has been approved by EPA. That LMP should clearly indicate that all controls that were relied on to demonstrate attainment will remain in place. The July 21, 2021, LMP SIP submission identifies the control strategies approved into the Liberty Borough area's attainment plan to bring the area into compliance. These controls were approved into the Pennsylvania SIP as permanent and enforceable measures and assisted the Liberty Borough area in attaining the PM₁₀ NAAQS.^[26] These controls are to remain in place for the duration of the second maintenance period.

The July 21, 2021 SIP submission meets EPA guidance for purposes of an attainment emissions inventory, and the emissions inventory data supports ACHD's conclusions that the existing control measures will continue to protect and maintain the PM₁₀ NAAQS.

C. Maintenance Demonstration

ACHD provided a maintenance demonstration for the Liberty Borough area in the first 10-year maintenance plan, which EPA approved on September 11, 2003 (68 FR 53515). According to EPA's 2001 PM₁₀ LMP Option Memo, if an area qualifies for the LMP option, EPA will treat that as a demonstration that the area will maintain the NAAQS and that, consequently, there is no need to model projected emissions over the maintenance period. Therefore, the Liberty Borough area is exempt from projecting emissions levels through the end date of the second 10-year maintenance plan.

D. Air Quality Monitoring Network

Once an area is redesignated, the applicable state or local agency must continue to operate an appropriate air monitoring network in accordance with 40 CFR part 58 to verify the attainment status of the area. ACHD has operated PM₁₀ monitors according to 40 CFR part 58 requirements at four sites within the Liberty Borough area since submittal of the redesignation request in 2002. A description, as well as a map, of the four Liberty Borough area PM₁₀ monitors can be found in ACHD's LMP plan.^[27] On December 21, 2022, ACHD submitted its 2021 Annual Monitoring Network Plan, which EPA approved on February 24, 2023.^[28] ACHD indicated in the Liberty Borough area second 10-year maintenance plan that it will continue to operate the air monitoring network in accordance with 40 CFR part 58 to verify the attainment status of the area, with no changes to the existing network unless preapproved by EPA.

E. Verification of Continued Attainment

The level of the PM₁₀ NAAQS is 150 µg/m^[3] , 24-hour average concentration. The NAAQS is attained when the expected number of days per calendar year with a 24-hour average concentration above 150 µg/m^[3] is equal to or less than one.^[29] As stated in the previous section of this preamble, ACHD plans to continue to operate a regulatory monitoring network and will continue to track the attainment status of the Liberty Borough area for the PM₁₀ NAAQS by reviewing monitored air quality concentrations during the maintenance period through 2023. ACHD will also continue to operate the air monitoring network in accordance with 40 CFR part 58 to verify the attainment status of the area, with no changes to the existing network unless pre-approved by EPA. Included in its second 10-year maintenance plan SIP submission, ACHD evaluated the complete, quality-assured, maximum 24-hour PM₁₀ concentrations at each Liberty Borough area monitor from 2001–2020 to verify continued attainment of the standard.

F. Contingency Provisions

Section 175A of the CAA states that a maintenance plan must include contingency provisions, as necessary, to ensure prompt correction of any violation of the NAAQS which may occur after redesignation of the area to attainment. As explained in the LMP Option Memo and the Calcagni Memo, these contingency provisions are an enforceable part of a federally approved SIP. The maintenance plan should clearly identify the events that would “trigger” the adoption and implementation of a contingency provision, the contingency provision(s) that would be adopted and implemented, and the schedule indicating the time frame by which the state and/or locality would adopt and implement the provision(s). The LMP Option Memo and the Calcagni Memo state that EPA will determine the adequacy of a contingency plan on a case-by-case basis. At a minimum, it must require that the applicable state or local agency implement all measures contained in the CAA part D nonattainment plan for the area prior to redesignation.

In the Liberty Borough area PM₁₀ LMP, ACHD indicated that the contingency provisions for the second 10-year maintenance plan are identical the contingency measures included in the area's attainment plan that was approved on September 8, 1998 (63 FR 47434). The contingency provisions include a requirement that the USS MVW Clairton Plant improve the capture of pushing emissions from its coke batteries. Within 60 days after determination of a violation of the 24-hour PM₁₀ NAAQS at any Liberty Borough area monitor, the contingency measures will be implemented. No contingency provisions or measures have been triggered at any time since the attainment plan SIP was approved in 1998.

EPA proposes to determine that the contingency provisions submitted in the Liberty Borough area PM₁₀ LMP are adequate to meet CAA section 175A requirements and the contingency provisions as outlined in the LMP Option Memo.

III. Proposed Action

EPA is proposing to approve the second 10-year PM₁₀ limited maintenance plan for the Liberty Borough area. EPA has reviewed the air quality data for this area and determined that it continues to show attainment of the PM₁₀ NAAQS and meets all the LMP requirements as described in this action. EPA is soliciting public comments on the issues discussed in this document. These comments will be considered before taking final action. If finalized, EPA's approval of this LMP will satisfy the section 175A CAA requirements for PM₁₀ for the second 10-year maintenance period for the Liberty Borough area.

IV. Statutory and Executive Order Reviews

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this action merely approves state law as meeting Federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this proposed action:

• Is not a “significant regulatory action” subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.);

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104–4);
• Does not have Federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
• Is not an economically significant regulatory action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 1997);
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);
• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA; and

• Executive Order 12898 (Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations, 59 FR 7629, February 16, 1994) directs Federal agencies to identify and address “disproportionately high and adverse human health or environmental effects” of their actions on minority populations and low-income populations to the greatest extent practicable and permitted by law. EPA defines environmental justice (E.J.) as “the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.” EPA further defines the term fair treatment to mean that “no group of people should bear a disproportionate burden of environmental harms and risks, including those resulting from the negative environmental consequences of industrial, governmental, and commercial operations or programs and policies.”

The ACHD did not evaluate environmental justice considerations as part of its SIP submittal; the CAA and applicable implementing regulations neither prohibit nor require such an evaluation. EPA did not perform an E.J. analysis and did not consider E.J. in this proposed rulemaking. Due to the nature of the proposed action being taken here, this proposed rulemaking is expected to have a neutral to positive impact on the air quality of the affected area.

In addition, this proposed rulemaking, regarding the second 10-year maintenance plan for the Liberty Borough PM₁₀ area, does not have tribal implications as specified by Executive Order 13175 (65 FR 67249, November 9, 2000), because the SIP is not approved to 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.

List of Subjects in 40 CFR Part 52

• Environmental protection
• Air pollution control
• Incorporation by reference
• Particulate matter
• Reporting and recordkeeping requirements

Adam Ortiz,

Regional Administrator, Region III.

Footnotes

1.  In its SIP submission, ACHD refers to the area at issue as the Liberty-Clairton area. In this proposed rulemaking, EPA refers to this area as the Liberty Borough area to distinguish it from the Liberty-Clairton fine particulate matter (PM_2.5) area and to be consistent with what the Agency called the area in our approval of the first 10-year maintenance plan and attainment plan. See 63 FR 47343 (September 8, 1998) and 68 FR 53515 (September 11, 2003).

2.  52 FR 24634 (July 1, 1987).

3.  71 FR 61144 (October 17, 2006).

4.  On August 7, 1987 (56 FR 56694), EPA designated portions of Allegheny County as a PM₁₀ nonattainment area due to measured violations of the 24-hour PM₁₀ NAAQS (52 FR 29383). The publication announcing the nonattainment designation upon enactment of the 1990 CAA Amendments was published on March 15, 1991 (56 FR 11101). On November 6, 1991, the area was subsequently classified as moderate nonattainment under sections 107(d)(4)(B) and 188(a) of the CAA.

5.  61 FR 29664 (June 12, 1996). 63 FR 47434 (September 8, 1998). 63 FR 32126 (June 12, 1998).

6.  Effective on October 14, 2003.

7.  The Liberty monitor site has two monitors, one is filter-based and the other is continuous.

8.  The Memorandum from the EPA's Air Quality Management Division Director to EPA Regional Air Directors entitled “Procedures for Processing Requests to Redesignate Areas to Attainment,” dated September 4, 1992 (Calcagni Memo) can be found at www.epa.gov/​sites/​default/​files/​2016-03/​documents/​calcagni_​memo_​-_​procedures_​for_​processing_​requests_​to_​redesignate_​areas_​to_​attainment_​090492.pdf.

9.  The “Limited Maintenance Plan Option for Moderate PM₁₀ Nonattainment Areas” can be found at www3.epa.gov/​ttn/​naaqs/​aqmguide/​collection/​cp2/​20010809_​wegman_​lmp_​moderate_​pm10_​naa.pdf and in the docket for this proposed rulemaking.

10.  There are four monitoring sites within the Liberty Borough area, three sites with one monitor each and one site with two monitors.

11.  While the 2001 PM₁₀ LMP Option Memo refers to a June 1987 “PM₁₀ SIP Development Guideline” document for methods in calculating design values for PM₁₀, neither document provides specific information on how to calculate a design value using five years of air quality data. In October 2022, after ACHD submitted its PM₁₀ LMP for the Liberty Borough area, EPA gave further clarification of how to compute a design value using five years of air quality data in a document titled “Guidance on the Limited Maintenance Plan Option for Moderate PM_2.5 Nonattainment Areas and PM_2.5 Maintenance Areas.”

12.  ACHD took this method from EPA's NetAssess2020 tool for monitored network assessments. https://sti-r-shiny.shinyapps.io/​EPA_​Network_​Assessment/​.

13.  See Table A–10 of ACHD's July 21, 2021 LMP SIP located in the docket for this proposed rulemaking.

14.  The 3-year design values for 2016–2020 include the following years: 2014–2016 (2016 3-year design value); 2015–2017 (2017 3-year design value); 2016–2018 (2018 3-year design value); 2017–2019 (2019 3-year design value); and 2018–2020 (2020 3-year design value).

15.  The methods for calculating design values for PM₁₀ are presented in a document entitled the “PM₁₀ SIP Development Guideline,” EPA–450/2–86–001, June 1987.

16.  The look-up procedure is a tabular technique for determining what point on the empirical frequency distribution corresponds to a frequency of 1/365. By construction, the table look-up procedure tends to provide a design concentration slightly lower than would be derived using a continuous curve representing a theoretical frequency distribution for PM₁₀ values. Additional explanation regarding the use of tabular estimation can be found in EPA's PM₁₀ SIP Development Guideline document.

17.  Although this LMP applies to maintenance through 2023, ACHD still used ten years as the vehicle miles traveled (VMT) projection to be conservative. An interpolation of 2025 and 2035 VMT projections was calculated to project for the year 2031. Projections for Allegheny County were used to represent the area, since there are no projections specific to the Liberty Borough area.

18.  Additional information on the data and calculations used for ACHD's analysis can be found in ACHD's SIP submission which is located in the docket for this proposed rulemaking.

19.  The inventory was updated in 1999.

20.  Mon Valley Works—Clairton Plant “is an integrated steelmaking operation that includes four separate facilities: Clairton Plant, Edgar Thomson Plant, Irvin Plant and Fairless Plant.” Taken from www.ussteel.com/​about-us/​locations.

21.  See the PADEP/ACHD's July 21, 2021 SIP submission, located in the docket for this proposed rulemaking, for additional changes to the initial emissions allowable inventory.

22.  Additional information on ACHD's actual inventory can be found in the SIP submission located in the docket for this proposed action.

23.  A more detailed version of the inventory can be found in Appendix A of PADEP/ACHD's July 2021 SIP submission.

24.  Precursors for PM₁₀ include sulfur dioxide (SO₂), nitrogen oxides (NO_X), volatile organic compounds (VOCs), and ammonia (NH₃).

25.  Allegheny County Health Department Air Quality Program. Settlement Agreement and Order #19060.

26.  61 FR 29664 (June 12, 1996) and 63 FR 32126 (June 12, 1998).

27.  Located in the docket for this proposed rulemaking. Docket No. EPA–R03–OAR–2023–0219, www.regulations.gov.

28.  EPA's approval letters for ACHD's past several Annual Monitoring Network Plans are included in the docket for this proposed rulemaking.

29.  See 40 CFR 50.6.