# Identification of plan.
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Final rule.
**SUMMARY:**
The Environmental Protection Agency (EPA) is approving the Idaho regional haze State Implementation Plan (SIP) revision submitted on August 5, 2022, supplemented on September 27, 2024, and clarified on August 12, 2025, as satisfying applicable requirements under the Clean Air Act and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. The Idaho SIP revision addressed the requirement to make reasonable progress toward the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility in certain national parks and wilderness areas.
**DATES:**
This final rule is effective October 6, 2025.
**ADDRESSES:**
The EPA has established a docket for this action under Docket ID No. EPA-R10-OAR-2024-0545 at *https://www.regulations.gov.* Although listed in the index, some information is not publicly available, *e.g.,* Confidential Business Information or other information the disclosure of which is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available at *https://www.regulations.gov,* or please contact the person listed in the *FOR FURTHER INFORMATION CONTACT* section for additional availability information.
**FOR FURTHER INFORMATION CONTACT:**
John Chi, EPA Region 10, 1200 Sixth Avenue, Suite 155, Seattle, WA 98101, at (206) 553-1185 or *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document, the use of “we” and “our” means “the EPA.”
**Table of Contents**
I. Background
II. EPA Responses to Comments Received
A. The National Parks Conservation Association, the Coalition To Protect America's National Parks, and the Sierra Club
1. Additional Facilities Considered
2. Low Cost-Effectiveness Threshold
3. Clearwater Paper Corporation
4. ITAFOS Conda LLC
5. J.R. Simplot—Don Siding Pocatello
6. TASCO Paul
7. Clearwater Paper Corporation Low Sulfur Fuel Oil Requirement
B. The Amalgamated Sugar Company
1. Inclusion of Site-Specific Permit Conditions
2. Condition 4.6 Is Redundant in Permit T1-2019-0020
C. The Idaho Association of Commerce and Industry
III. Final Action
IV. Incorporation by Reference
V. Statutory and Executive Order Reviews
**I. Background**
On March 24, 2025, the EPA proposed to approve the regional haze State Implementation Plan (SIP) revision submitted by Idaho on August 5, 2022, supplemented on September 27, 2024, and clarified on August 12, 2025, as satisfying applicable requirements under the Clean Air Act and the EPA's Regional Haze Rule (RHR) for the program's second implementation period (90 FR 13516).
The public comment period for our notice of proposed rulemaking (NPRM) closed on April 23, 2025. We received six comments. We determined two of the comments were not germane to our action. One commenter requested that, “the EPA and the Idaho Department of Environmental Quality [“IDEQ” or “DEQ”] consider a program to install supplemental catalytic converters on older gasoline cars to reduce NO <sub>X</sub> , VOCs, and CO emissions.” The commenter further stated that the commenter's company has developed supplemental catalytic converters to reduce tailpipe emissions. This comment is outside the scope of this action. The revisions to Idaho's SIP addressed in this action do not relate to control of motor vehicle emissions in general, or the control of tailpipe emissions using supplemental catalytic converters. Rather, this action primarily addresses stationary source industrial emissions that may impact visibility in Class I areas in Idaho. In addition, the commenter did not indicate that the EPA approval of the Idaho regional haze plan submission is inconsistent with the Clean Air Act.
A second commenter recommended not approving the plan until Idaho attains clean air standards. The commenter also stated that “Idaho will need to degrowth, contract and regulate more to provide clean air for Idahoans health and safety.” This action addresses the Clean Air Act visibility protection requirements of sections 169A and 169B, not the Clean Air Act's health-based air quality standards, such as the national ambient air quality standards. Therefore, this comment is outside the scope of this action.
We also received one comment in support of this action. The commenter conveyed overall support for our NPRM, stating, “I am very happy and proud of the EPA for proposing this influential rule that will help in Idaho. However, seeing that Idaho has an average AQI of 62 which many other states are well above 70 I think similar rules to these should be implemented in other areas of our nation.” The EPA acknowledges the commenter's support.
We received germane, adverse comments from a coalition of conservation groups (the National Parks Conservation Association, the Coalition to Protect America's National Parks, and the Sierra Club), the Amalgamated Sugar Company (TASCO), and the Idaho Association of Commerce and Industry (IACI). The full text of the comments may be found in the docket for this action. We have reprinted in relevant part or summarized the comments and provided our responses in section II of this preamble.
**II. EPA Responses to Comments Received**
**A. The National Parks Conservation Association, the Coalition To Protect America's National Parks, and the Sierra Club**
**1. Additional Facilities Considered**
*Comment:* “[W]e believe DEQ should have considered additional facilities to strengthen their SIP Revision Package.”
*Response:* The RHR does not require a State to evaluate all sources of emissions, nor does it list factors that a State must or may consider when selecting sources. Rather, the RHR requires that a State's submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.” [^1] The State must also appropriately document the technical basis for source selection, which may include methods for quantifying potential visibility impacts such as emissions divided by distance metrics, trajectory analyses, residence time analyses, and/or photochemical modeling.
[^1] 40 CFR 51.308(f)(2)(i).
As detailed in the submission and described in our NPRM, Idaho used the source selection methodology developed by the Western Regional Air Partnership (WRAP) for western States. [^2] The WRAP's approach used the Q/d method, where Q is the sum of visibility impairing pollutants (NO <sub>X</sub> , SO <sub>2</sub> and PM <sub>10</sub> ), and d is the distance (kilometers) to the boundary of the nearest Class I area. The Idaho DEQ screened sources as described in the following steps: [^3]
[^2]*See* the WRAP Technical Support System (TSS) at *www.wrapair2.org.*
[^3] Idaho 2022 plan submission, page 54.
1. Identify those facilities with total facility-wide emissions of visibility impairing pollutants (NO <sub>X</sub> , SO <sub>2</sub> and PM <sub>10</sub> ) greater than 25 tons per year (tpy) based on 2014 National Emissions Inventory (NEI) data.
2. Calculate the distance from each facility identified in Step 1 to the nearest Class I area boundary (including those in other States) in kilometers (km). Facilities greater than 400 km from the nearest Class I area were considered to have minimal impact on visibility and were excluded.
3. Identify those facilities with a Q/d greater than the State-defined threshold. Idaho used a relatively low Q/d threshold of 2.0 because the State estimated that the threshold captured 70% to 80% of emissions from Idaho facilities.
4. Refine the Q/d analysis using more recent 2017 NEI data to screen out sources that have a Q/d less than the State-defined threshold for 2017 emissions.
Idaho's initial source screening used 2014 emissions inventory data to identify 14 facilities in Idaho with Q/d greater than 2.0. [^4] Idaho refined the Q/d analysis using 2017 emissions inventory data and screened out three additional facilities from the original 14 (Idaho Forest Group LLC-Riley Creek-Moyie Springs, Plummer Forest Group, Inc-Post Falls, and Rexburg Facility of Basic American Foods). [^5] Idaho also screened out a facility outside of the State's regulatory purview (Boise Airport), as well as a facility near Sawtooth Wilderness Area (Northwest Pipeline—Mountain Home) because the facility primarily emitted NO <sub>X</sub> and WRAP modeling found anthropogenic contributions to NO <sub>X</sub> at SAWT1 were negligible. [^6] This screening process yielded nine Idaho facilities with Q/d greater than 2.0.
[^4]*Id.,* page 55. *See* table 22 as updated by Idaho 2024 supplemental submission.
[^5]*Id.*
[^6]*Id.,* page 56. *See* also figure 11.
Idaho also used the WRAP's weighted emissions potential (WEP) to further inform source selection. [^7] The WEP is a screening tool used to identify sources contributing to visibility impairment in the 2014-2018 period and still operating in 2028 that have the potential to contribute to haze formation at Class I areas. [^8] The rank point analysis consists of facility-level 2028 emissions for NO <sub>X</sub> or SO <sub>2</sub> sources overlaid with the corresponding extinction-weighted residence time for ammonium nitrate or ammonium sulfate. [^9] Ultimately, Idaho determined that the sources it selected for review under the four statutory factors captured the sources potentially contributing to visibility impairment in Class I areas in other States. Importantly, Idaho noted that all the sources it reviewed had greater visibility impacts on Idaho Class I areas. Specifically, the 2028OTBa2 State-level source apportionment results indicated that Idaho facilities had the most significant impact on visibility impairment at Class I areas within the State. Thus, Idaho reasoned, and the neighboring States agreed, that addressing visibility impairment in Idaho's Class I areas would adequately capture Idaho sources' contribution to visibility impairment in Class I areas outside the State.
[^7]*Id.,* pages 61-62.
[^8]*Id.*
[^9]*Id.*
Furthermore, Idaho identified 27 Class I areas in five neighboring States (Montana, Nevada, Oregon, Washington, Wyoming) that could potentially be affected by emissions from sources within Idaho. However, applying the same source screening analysis yielded no additional Idaho facilities beyond the nine already selected for four-factor analysis. [^10] Those nine facilities were ultimately selected for further evaluation by Idaho.
[^10]*Id.,* tables 24-28.
As explained in the NPRM, the RHR preamble, and in the response to the conservation group comments above, the RHR does not require States to consider controls for all sources, all source categories, or any or all sources in a particular source category. This is addressed on page 9 of the 2019 Regional Haze Guidance [^11] as follows “Instead, a state may reasonably select a set of sources for an analysis of control measures. The guidance that an analysis of control measures is not required for every source in each implementation period is based on CAA section 169A(b)(2).” Rather, the States have discretion to choose any source selection methodology or threshold that is reasonably calculated to evaluate and determine the emission reduction measures necessary to make reasonable progress, provided that the choices they make are reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that a State's SIP submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.” The technical basis for source selection, which may include methods for quantifying potential visibility impacts such as emissions divided by distance metrics, trajectory analyses, residence time analyses, and/or photochemical modeling, must also be appropriately documented, as required by 40 CFR 51.308(f)(2)(iii).
[^11] Guidance on Regional Haze State Implementation Plans for the Second Implementation Period. The EPA Office of Air Quality Planning and Standards, Research Triangle Park (August 20, 2019), page 38 (EPA 2019 Guidance), available in the docket for this action and at *https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period.*
On that basis, we find that Idaho included adequate information and an explanation of its source selection methodology in its regional haze plan submission and that the information submitted supports a finding that Idaho examined a reasonable set of sources for the second implementation period.
**2. Low Cost-Effectiveness Threshold**
*Comment:* “DEQ evaluated potential reasonable progress measures for its sources using an unreasonably low cost-effectiveness threshold. DEQ's average cost-effectiveness threshold for evaluating controls was just $6,100. DEQ should have used a higher cost-effectiveness threshold, similar to that employed by other states like Colorado, Nevada, and New Mexico, all of which used a $10,000 per ton threshold.”
*Response:* As the EPA stated in the NPRM, the EPA did not establish a cost-effectiveness threshold for the second implementation period. Rather, the EPA's 2019 Guidance clarified that States had the flexibility to decide a reasonable approach to evaluating costs. [^12] Further, the RHR does not provide a specific cost effectiveness threshold. The fact that Idaho used a cost-effectiveness threshold that is lower than another State's threshold is not, by itself, an adequate basis for disapproving a State's regional haze plan.
[^12] Guidance on Regional Haze State Implementation Plans for the Second Implementation Period. The EPA Office of Air Quality Planning and Standards, Research Triangle Park (August 20, 2019), page 38 (EPA 2019 Guidance), available in the docket for this action and at *https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period.*
In developing its regional haze plan for the second implementation period, Idaho established a cost-effectiveness threshold of $6,100 per ton by adjusting the $5,000 per ton best available retrofit technology (BART) cost-effectiveness threshold (used during the first implementation period) for inflation. [^13] Idaho then analyzed potential control measures using the four statutory factors for specific units at selected facilities. Control measures that would cost over $6,100 per ton were considered too costly for purposes of the second implementation period. While there is no threshold for percentage of emissions captured for analysis, Idaho's approach is well reasoned and therefore we continue to find that Idaho documented a reasonable approach to evaluating costs and met its obligations under 40 CFR 51.308(f)(2)(i).
[^13] Idaho 2022 plan submission, pages 64 and 65.
Additionally, although Nevada did set a $10,000 per ton cost-effectiveness threshold in its second planning period regional haze SIP, the EPA disagrees with commenters' assertion that both New Mexico and Colorado also set $10,000 per ton thresholds. Colorado only mentioned the possibility of a $10,000 per ton threshold in its prehearing statement and in early drafts of its SIP revision for the second implementation period. However, this threshold was not carried over into the final SIP revision submitted to the EPA. Also, as of the time this comment was submitted, New Mexico has not yet submitted their SIP revision for the second implementation period. Although New Mexico's draft SIP revision references a $10,000 per ton threshold in its analysis, New Mexico has yet to submit a formal SIP revision to the EPA.
**3. Clearwater Paper Corporation**
*Comment:* “DEQ evaluated control measures for Clearwater Paper Corporation and determined that the figure of $9,556/ton for selective catalytic reduction (SCR) was greater than the threshold of $6,100/ton that DEQ set. DEQ then failed to propose SCR controls at No. 4 Power Boiler based on cost-effectiveness. In their SIP comments to Idaho's 2024 submission, NPS encouraged DEQ to evaluate whether requiring SCR to control NO <sub>X</sub> emissions from the No. 4 Power Boiler would be reasonable. The Conservation Organizations support that recommendation and urge EPA to ensure SCR controls at No. 4 Power Boiler are included in its final proposal.”
*Response:* We disagree with the commenters. In the 2024 submission, Idaho assessed the feasibility and costs of retrofitting the No. 4 Power Boiler with additional NO <sub>X</sub> controls, including low-NO <sub>X</sub> burners (LNB), Ultra-low NO <sub>X</sub> burners (ULNB), selective non-catalytic reduction (SNCR), selective catalytic reduction (SCR), and low-temperature oxidation (LoTOx). [^14] Idaho determined that ULNB and flue gas recirculation were technologically infeasible. For the remaining, feasible controls, Idaho concluded that the cost to install LNB, SNCR, SCR, and LoTOx would exceed the State's established cost-effectiveness threshold. [^15] For SCR specifically, Idaho estimated that add-on controls would cost $9,556 per ton of NO <sub>X</sub> removed. Idaho used vendor quotes and the EPA's Control Cost Manual to estimate this cost. [^16] As discussed above, Idaho reasonably explained the basis for its cost effectiveness threshold of $6,100/ton reduced. States may evaluate the cost factor using a cost threshold and use that threshold to provide a reasonable justification for four-factor analysis outcomes. Thus, Idaho was reasonable to reject SCR as too costly based on this threshold.
[^14] Idaho 2022 plan submission, Appendix B. Four-Factor Analyses and Reviews. Clearwater Paper Corp.—Pulp and Paperboard Division.
[^15]*Ibid.* Idaho determined that installing a low NO <sub>X</sub> burner would have a cost effectiveness nor >$10,000 per ton reduced; SNCR $11,600 per ton reduced; and LoTOx $21,132 per ton reduced.
[^16] Idaho 2024 supplemental submission, appendix H, DEQ Responses to Public Comments (Replace), page 41.
**4. ITAFOS Conda LLC**
*Comment:* “[T]he NPS recommended that a wet packed scrubber would likely be cost-effective to reduce SO <sub>2</sub> emissions from the East Sulfuric Acid Plant. In the SIP Supplement, DEQ updated the information provided in appendix B including a new facility Four-Factor Analysis and DEQ's review of the analysis. In its review, DEQ provided an adjusted cost effectiveness for wet flue gas desulfurization or hydrogen peroxide scrubbing of about $8,000/ton SO <sub>2</sub> removed. While the cost exceeds DEQ's cost threshold of $6,100/ton of SO <sub>2,</sub> given the facility's impact on Class I areas, we support NPS's recommendation on the SIP Supplement to require SO <sub>2</sub> scrubbing in this planning period.”
*Response:* We disagree with this comment. As discussed above, the EPA finds that Idaho was reasonable in using a cost effectiveness threshold of $6,100 to evaluate whether controls are necessary in the second implementation period. Idaho was thus reasonable to reject controls with projected costs in excess of this threshold. This was the case with all of the controls Idaho evaluated for the East Sulfuric Acid Plant.
To the extent the comment contests Idaho's cost estimates, we also disagree. With respect to cost calculations, the EPA recommended in the 2019 Guidance that States follow the EPA's Control Cost Manual recommendations to ensure consistent cost calculations across controls and sources. [^17] The EPA also recommended that States explain any deviations from those methods or alternative approaches. [^18] Finally, the Control Cost Manual provides for generic cost estimates using a consistent methodology but recommends that States obtain facility-specific vendor cost quotes when practical. [^19]
[^17] EPA 2019 Guidance, page 37 (“We anticipate that the outcome of the decision-making process by a state regarding a control measure may most often depend on how the state assesses the balance between the cost of compliance and the visibility benefits, with the other three statutory factors either being subsumed into the cost of compliance or not being major considerations.”).
[^18]*Id.*
[^19]*Id.*
In evaluating the cost of WFGD, a hydrogen peroxide scrubber, and DSI, Idaho obtained cost information from equipment vendors. [^20] Idaho conducted subsequent evaluations of its initial cost estimates to ensure the cost estimates took into consideration all the ancillary equipment necessary and site-specific complexities. Idaho adequately explained its cost calculation methodology, its use of the Control Cost Manual, and its rationale for adjusting initial vendor estimates based on site-specific information. Therefore, the EPA's position remains that Idaho adequately considered cost, along with the other three factors in 40 CFR 51.308(f)(2), in determining the controls necessary for reasonable progress at the East Sulfuric Acid Plant and the State was reasonable in rejecting controls with costs above $6,100 per ton reduced.
[^20] Idaho 2024 supplemental submission, appendix B Four Factor Analysis and Review (Append), page 5-10.
**5. J.R. Simplot—Don Siding Pocatello**
*Comment:* “the NPS explained that because the Itafos analysis included a vendor quote for a packed tower wet scrubber using hydrogen peroxide and caustic soda as scrubbing reagents and the Simplot plants have higher permitted production capacity but are similar to the Itafos facility plant, the NPS used the Itafos vendor quote PEC and the “six-tenths” rule to apply these costs to the Simplot plants. The NPS explained that it detailed all analysis assumptions in the written documentation. The NPS's cost-effectiveness figures demonstrate that scrubbers on the Simplot sulfuric acid plants are cost effective for Plants No. 300 and 400, reducing emissions by 98% or roughly 733 tons per year. Thus, the EPA must ensure that Four-Factor Analyses are conducted and emission controls are included for these plants in the final action. Although the SIP Supplement concludes that existing permit conditions for both sulfuric acid plants are sufficient and that no Four-Factor Analysis or additional SO <sub>2</sub> controls are needed this planning period, we agree with NPS's recommendation that a wet packed-tower scrubber is still likely cost-effective for Plants No. 300 and 400 and should be required in this planning period.”
*Response:* We disagree with the commenters that four-factor analyses are required for evaluating retrofit SO <sub>2</sub> controls on the Don Siding Plant sulfuric acid plants. In our NPRM, we proposed to approve the Idaho DEQ's determination that the Don Siding sulfuric acid plants were already subject to BACT-level SO <sub>2</sub> limits per a 2015 Federal consent decree to resolve PSD applicability issues and that those limits constituted existing effective controls. <sup>21</sup> In our NPRM we stated that in the EPA 2019 Guidance, the EPA acknowledged that a control technology review under the four regional haze factors was unlikely to find feasible, cost-effective controls for sources that recently went through PSD BACT. [^22] In this instance, both plants are subject to 2015 BACT limits imposed through a Federal consent decree with the EPA. Consistent with the EPA 2019 Guidance, and based on the submitted information, the EPA agreed with Idaho that additional control technology review under the four regional haze factors would be unlikely to find feasible, cost-effective controls. [^23]
[^21] See *https://www.epa.gov/enforcement/consent-decree-j-r-simplot-company/.* For the No. 300 Sulfuric Acid Plant, SO <sub>2</sub> emissions are limited to 2.5 lb/ton of 100% sulfuric acid produced on a rolling 3-hour average basis, except during periods of startup, shutdown, or malfunction, and 1.5 lb/ton 100% sulfuric acid produced on a rolling 365-day average basis including periods of startup, shutdown, or malfunction. For the No. 400 Sulfuric Acid Plant, SO <sub>2</sub> emissions are limited to 2.5 lb/ton of 100% sulfuric acid produced on a rolling 3-hour average basis, except during periods of startup, shutdown, or malfunction, and 1.6 lb/ton 100% sulfuric acid produced on a rolling 365-day average basis including periods of startup, shutdown, or malfunction.
[^22] 2019 EPA Guidance, pages 22-23.
[^23]*Ibid.*
As background, it is helpful to review the technology already in place on the plants to control SO <sub>2</sub> emissions. The No. 300 Sulfuric Acid Plant is already equipped with scrubber technology to reduce SO <sub>2</sub> emissions, specifically a DynaWave reverse-jet wet gas scrubber and an Ammsox packed bed ammonium scrubber in series. The No. 400 Sulfuric Acid Plant uses a double contact/double absorption (DCDA) process and makes use of a high-efficiency catalyst to maximize conversion of SO <sub>2</sub> to SO <sub>3</sub> , which in turn reduces SO <sub>2</sub> emissions. In an SO <sub>2</sub> BACT analysis conducted in 2013, Simplot determined the No. 400 plant could meet BACT-level SO <sub>2</sub> limits based on DCDA technology and high-efficiency catalysts alone. [^24] In its research for the BACT analysis, Simplot found that wet scrubbing is not typically used in combination with DCDA technology for SO <sub>2</sub> emissions control and that the use of a wet scrubber in combination with a high-efficiency catalyst would provide only marginal SO <sub>2</sub> reductions at significant cost. [^25]
[^24] Simplot Don Siding Permit to Construct application, July 2013, pages 53 through 60 (section 4.7).
[^25]*Ibid.*
We continue to find that Idaho's decision was reasonable—that additional control technology review under the four regional haze factors would be unlikely to find additional feasible, cost-effective retrofit SO <sub>2</sub> controls on the Simplot sulfuric acid plants. Therefore, we concur with Idaho that the existing consent decree limits constitute existing effective controls for purposes of the regional haze second implementation period.
**6. TASCO Paul**
*Comment:* “NPS recommended removing coal as a fuel for the pulp dryers at the TASCO-Paul facility to further reduce SO <sub>2</sub> and NO <sub>X</sub> emissions. In the SIP Supplement, DEQ found that eliminating coal from the north and south pulp dryers at the Paul facility is the most cost-effective option with the greatest emission reductions. However, no additional controls were required for this planning period due to the Foster-Wheeler boiler fuel conversion at the TASCO-Twin Falls facility. We agree with NPS in their 2024 SIP Supplement that emission reductions at one facility do not justify bypassing cost-effective controls at another. We support NPS's recommendation to remove coal as a fuel for the pulp dryers at the TASCO-Paul facility to reduce haze-causing emissions in this planning period.”
*Response:* In its submission, Idaho selected controls to achieve emissions reductions at the TASCO Nampa and Twin Falls facilities over the TASCO Paul facility because doing so would achieve greater overall emissions reductions and because the Nampa and Twin Falls facilities have greater visibility impacts on Class I areas. The RHR does not prohibit States from maximizing emissions reductions across multiple facilities impacting the same Class I area. We continue to find that Idaho's approach is consistent with the RHR.
**7. Clearwater Paper Corporation Low Sulfur Fuel Oil Requirement**
*Comment:* “The Conservation Organizations echo the recommendation of NPS to require the use of low-sulfur fuel oil as an alternative fuel in the No. 4 Power Boiler at this facility to ensure short-term changes in emissions.”
*Response:* In our NPRM we stated that we concur with Idaho's assessment that it is not feasible to require the facility to fire lower sulfur fuel oil in the No. 4 Power Boiler at this time. Information in the 2024 submission stated that the No. 4 Power Boiler fires hog fuel and natural gas primarily, and while being permitted to fire higher sulfur fuel oil, the facility must limit the amount of fuel oil fired due to operational requirements and to ensure compliance with the current 100 ton per year SO <sub>2</sub> emission limit. [^26]
[^26] Idaho 2024 supplemental submission, appendix B, Clearwater power boiler fuel oil analysis.
**B. The Amalgamated Sugar Company**
**1. Inclusion of Site-Specific Permit Conditions**
*Comment:* “The IDEQ Air Permits and the site-specific permit conditions included in the proposed approval are federally enforceable through state delegated and EPA approved air quality programs, specifically New Source Review (and related Permits to Construct) and Title V (known as Tier I permits). While the IDEQ Air Permits included in the Idaho SIP contain conditions acceptable to ASC when the Idaho SIP was developed, economic and operational changes can and frequently do prompt necessary revisions. Revisions to federally enforceable permits issued by IDEQ are governed by state law and the applicable Federal framework incorporated by reference into state law. If the Idaho SIP is approved as proposed, with inclusion of specific permit conditions, then those included permit conditions are also subject to Federal processes to revise the Code of Federal Regulations (CFR) when circumstances at a facility change. This approach is impractical, creates delay and drains resources of ASC, IDEQ, and EPA.”
*Response:* The visibility requirements of the Clean Air Act and 40 CFR 51.308(f)(2) require each applicable implementation plan to contain such emission limits, schedules of compliance and other measures as may be necessary to make reasonable progress toward meeting the national goal of preventing and remedying visibility impairment in class I areas. See Clean Air Act 169A(b)(2). Consistent with these requirements, Idaho submitted for incorporation into its SIP permit conditions detailing emission limits, fuel requirements, monitoring, recordkeeping and reporting requirements, and compliance schedules that Idaho determined were necessary for reasonable progress. Accordingly, the EPA proposed to approve and incorporate by reference into the SIP these enforceable requirements. We acknowledge the commenter is concerned about future, potential necessary changes to permit conditions. The EPA commits to working collaboratively with Idaho on any future revisions to these permit conditions to ensure the revisions meet Clean Air Act requirements and to minimize processing delays.
**2. Condition 4.6 Is Redundant in Permit T1-2019-0020**
*Comment:* “Permit T1-2019-0020 issued November 5, 2021, to ASC's Paul facility, includes many conditions proposed to be incorporated into the Idaho SIP. Specifically, conditions 4.4, 4.6, and 4.7, among others, limit utilization of the boilers at the ASC Paul facility, with some of the conditions overlapping others. ASC plans to request a permit revision from IDEQ to remove condition 4.6 to allow for greater flexibility in the facility's boiler utilization. Future operations may need to run three boilers simultaneously to achieve preferred load distribution and steam generation. Federally enforceable condition 4.4 limits the emissions generated by the facility boilers annually and condition 4.7 limits the amount of total energy consumed by the facility boilers annually (in therms). These conditions sufficiently limit the annual emissions of pollutants subject to regulation under the regional haze program. The facility's compliance with conditions 4.4 and 4.7, makes condition 4.6 redundant and unreasonably limits operational flexibility of the boiler system at the facility. ASC requests that EPA disapprove Idaho SIP inclusion of condition 4.6 of Permit T1-2019-0020 issued November 5, 2021, because it is redundant and unnecessary for reasonable further progress.”
*Response:* The Idaho Department of Environmental Quality withdrew condition 4.6 of Permit T1-2019-0020 via a letter sent on August 12, 2025, because the State determined that this condition is not necessary for reasonable progress during the second planning period. The EPA agrees with the State. The EPA reviewed Idaho's 2022 and 2024 submissions and confirmed that condition 4.6 is not needed to sufficiently limit emissions from these specific boilers for purposes of the regional haze second implementation period. As discussed in the NPRM and in section II.A.6. of this preamble, Idaho determined that controls on TASCO Paul were not necessary for reasonable progress for the second implementation period because of the surplus emissions reductions at the TASCO Twin-Falls facility.
Therefore, our final action is not incorporating condition 4.6 by reference into the SIP.
**C. The Idaho Association of Commerce and Industry**
*Comment:* “IACI urges the restructuring of the Regional Haze Program to simplify and streamline future permit revisions by deferring to federally enforceable actions of state permitting agencies that comply with the provisions of the Clean Air Act and applicable Federal regulations to avoid additional EPA process and delay and IACI urges EPA to revise the Regional Haze Program with sanity and purpose. This proposed action, incorporating existing and already enforceable site-specific permit conditions into the CFR, will result in impractical and unreasonable layers of process to revise permit conditions that support future economic growth in local communities and manifest the Great American Comeback. Additional processes also erode the cooperative federalism framework under the Clean Air Act and will add to the persistent SIP backlog.”
*Response:* The EPA acknowledges IACI's concerns with the current RHR and support for revising the rule. On March 12, 2025, Administrator Zeldin announced the EPA's intention to review the RHR and to restore sanity and purpose to the program. [^27] We encourage IACI to participate in any future regional haze rulemaking effort. This review of the RHR is separate from the EPA's actions on regional haze SIPs for the second planning period. The EPA's position remains that Idaho's regional haze plan for the second implementation period meets the requirements of Clean Air Act section 169A and 40 CFR 51.308(f).
[^27] See Administrator Zeldin Begins Restructuring Regional Haze Program, March 12, 2025, available at *https://www.epa.gov/newsreleases/administrator-zeldin-begins-restructuring-regional-haze-program.*
Please see the EPA's response to the Amalgamated Sugar Company at section II.B.1. of this preamble for an explanation of the need to adopt source-specific enforceable emission limits into the SIP.
Regarding IACI's concern about economic growth, the EPA notes that adoption of existing emission limits into the SIP does not impact nor limit construction of new stationary sources or emission units within existing stationary sources. New construction will be governed by Idaho's existing minor and major new source review permit programs.
With respect to IACI's comment regarding the timing of the EPA's NPRM, the EPA notes that it is subject to a Consent Decree obligation to finalize action on Idaho's regional haze plan by August 28, 2025 (originally May 30, 2025, before the Court granted the EPA's motion for extension). The EPA must publish proposed actions in sufficient time for the public to comment prior to finalization. Additionally, with respect to the commenter's concern about the SIP backlog, there are currently no backlogged Idaho SIP submissions, except this regional haze plan on which we are taking final action.
**III. Final Action**
For the reasons stated in our NPRM (90 FR 13516, March 24, 2025) and in section II. of this preamble, we are approving the Idaho SIP revision submitted on August 5, 2022, supplemented on September 27, 2024, and clarified on August 12, 2025, as satisfying the regional haze requirements for the second implementation period contained in 40 CFR 51.308. Idaho submitted the SIP revision to meet visibility protection requirements pursuant to Clean Air Act sections 169A and 169B and the EPA's implementing regulations at 40 CFR 51.308.
We are approving the SIP revision as meeting the following requirements:
• Identification of Class I area requirements of 40 CFR 51.308(f);
• Calculation of baseline, current, and natural visibility conditions; progress to date; and uniform rate of progress requirements of 40 CFR 51.308(f)(1);
• Long-term strategy requirements of 40 CFR 51.308(f)(2);
• Reasonable progress goal requirements of 40 CFR 51.308(f)(3);
• Reasonably attributable visibility impairment requirements of 40 CFR 51.308(f)(4);
• Monitoring strategy and other plan requirements of 40 CFR 51.308(f)(6);
• 5-year progress report requirements of 40 CFR 51.308(f)(5) and (g); and
• State and Federal Land Manager coordination requirements of 40 CFR 51.308(i).
We are also approving and incorporating by reference into the Idaho SIP at 40 CFR 52.670(d), *EPA approved source-specific requirements,* the following source-specific control requirements as part of Idaho's long-term strategy for regional haze:
| Name of source | Permit or compliance agreement No. | State | Explanations |
| --- | --- | --- | --- |
| Clearwater Paper Corp, Lewiston, Idaho | Permit T1-2020.0024 | 3/30/2023 | Permit conditions 5.4, 5.5, 5.6, 5.7, 5.10, 5.11, 5.12, 5.13, 5.14, 5.15, 7.1, 7.4, 7.9, 7.10, 8.1, 8.6, 9.1, 9.2, 9.6, 9.11, 26.22, 26.23, 26.26, 26.27, 26.28, and 26.29 only. |
| ITAFOS Conda, LLC, Soda Springs, Idaho | Permit T1-2016.0015 | 3/2/2022 | Permit conditions 5.1, 5.4, 5.5, 5.11, 16.22, and 16.23 only. |
| Northwest Pipeline LLC, Soda Springs, Idaho | Compliance Agreement Schedule Case No. E-2023.0011 | 9/1/2023 | |
| P4 Production, LLC, Soda Springs, Idaho | Compliance Agreement Schedule Case No. E-2023.0013 | 11/27/2021 | |
| P4 Production LLC, Soda Springs, Idaho | Permit T1-2020.0029 | 12/23/2021 | Permit conditions 4.2, 4.4, 4.5, 4.6, 4.7, 4.19, 4.20, 4.21, 13.22, and 13.33 only. |
| J.R. Simplot, Pocatello, Idaho | Permit T1-2017.0024 | 3/29/2023 | Permit conditions 15.9, 15.10, 15.11, 15.19, 15.20, 15.21, 15.22, 15.25, 15.27, 16.6, 16.9, 16.10, 16.19, 16.20, 16.21, 16.22, 16.26, 16.27, 18.22, and 18.23 only. |
| Tamarack Mill LLC, New Meadows, Idaho | Permit T1-2019-0024 | 10/17/2022 | Permit conditions 5.2, 5.3, 5.5, 5.8, 5.17, 10.22, and 10.23 only. |
| The Amalgamated Sugar Company LLC—Nampa Factory, Nampa, Idaho | Permit P-2018.0011 | 2/15/2023 | Permit condition 4.8 only. |
| The Amalgamated Sugar Company LLC—Paul Factory, Paul, Idaho | Permit T1-2019-0020 | 11/5/2021 | Permit conditions 4.3, 4.4, 4.5, 4.7, 4.9, 4.10, 4.11, 4.12, 4.15, 4.16, 4.18, 11.22, and 11.23 only. |
| The Amalgamated Sugar Company LLC—Twin Falls Factory, Twin Falls | Permit T1-2016.0017 | 1/21/2022 | Permit condition 4.9 and 5.2 only. |
**IV. Incorporation by Reference**
In this document, the EPA is finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is finalizing the incorporation by reference of the regulatory provisions described in section III. of this preamble. The EPA has made, and will continue to make, these materials generally available through *https://www.regulations.gov* and at the EPA Region 10 Office (please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section of this preamble for more information). Therefore, these materials have been approved by the EPA for inclusion in the SIP, have been incorporated by reference by the EPA into that plan, are fully federally enforceable under sections 110 and 113 of the Clean Air Act as of the effective date of the final rule of the EPA's approval, and will be incorporated by reference in the next update to the SIP compilation. [^28]
[^28] 62 FR 27968 (May 22, 1997).
**V. Statutory and Executive Order Reviews**
Under the Clean Air Act, the Administrator is required to approve a SIP submission that complies with the provisions of the Clean Air Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to approve State choices, provided that they meet the criteria of the Clean Air Act. 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 action:
• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);
• Is not subject to Executive Order 14192 (90 FR 9065, February 6, 2025) because SIP actions are exempt from review under Executive Order 12866;
• 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 subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001); and
• 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 Clean Air Act.
In addition, this final action is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the rule does not have tribal implications and will not impose substantial direct costs on Tribal Governments or preempt tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000). Consistent with EPA policy, the EPA contacted four Tribes, specifically the Coeur d'Alene Tribe, the Shoshone Bannock Tribes of the Fort Hall Reservation, the Nez Perce Tribe, and the Kootenai Tribe of Idaho, and offered an opportunity to consult on a government-to-government basis in letters dated July 22, 2022. We received no consultation or coordination requests. The letters may be found in the docket for this action.
This action is subject to the Congressional Review Act, and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action is not a “major rule” as defined by 5 U.S.C. 804(2).
Under section 307(b)(1) of the Clean Air Act, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by November 4, 2025. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this action for the purposes of judicial review nor does it extend the time within which a petition for judicial review may be filed and shall not postpone the effectiveness of such rule or action. This action may not be challenged later in proceedings to enforce its requirements. See section 307(b)(2).
**List of Subjects in 40 CFR Part 52**
Environmental protection, Air pollution control, Incorporation by reference, Intergovernmental relations, Ozone, Particulate matter, Reporting and recordkeeping requirements, Sulfur oxides, Volatile organic compounds.
Dated: August 22, 2025.
Emma Pokon,
Regional Administrator, Region 10.
For the reasons set forth in the preamble, 40 CFR part 52 is amended as follows:
**PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS**
**40 CFR Part 52**
1. The authority citation for part 52 continues to read as follows:
**Authority:**
42 U.S.C. 7401 *et seq.*
**Subpart N—Idaho**
**40 CFR Part 52**
2. In § 52.670:
a. Amend paragraph (d), Table 4 by adding ten entries to the end of the table; and
b. Amend paragraph (e), Table 6 by adding the entry “Regional Haze SIP Revision for the Second Implementation Period” to the end of the table.
The additions read as follows:
§ 52.670
(d) * * *
| Name of source | Permit No. | State | EPA approval date | Explanation |
| --- | --- | --- | --- | --- |
| | | | | |
| * * * * * * * | | | | |
| Clearwater Paper Corp, Lewiston, Idaho | T1-2020.0024 | 3/30/2023 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit conditions 5.4, 5.5, 5.6, 5.7, 5.10, 5.11, 5.12, 5.13, 5.14, 5.15, 7.1, 7.4, 7.9, 7.10, 8.1, 8.6, 9.1, 9.2, 9.6, 9.11, 26.22, 26.23, 26.26, 26.27, 26.28, and 26.29 only. |
| ITAFOS Conda LLC, Soda Springs, Idaho | T1-2016.0015 | 3/2/2022 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit conditions 5.1, 5.4, 5.5, 5.11, 16.22, and 16.23 only. |
| Northwest Pipeline LLC, Soda Springs, Idaho | Compliance Agreement Schedule Case No. E-2023.0011 | 9/1/2023 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | |
| P4 Production LLC, Soda Springs, Idaho | Compliance Agreement Schedule Case No. E-2023.0013 | 11/27/2021 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | |
| P4 Production LLC, Soda Springs, Idaho | T1-2020.0029 | 12/23/2021 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit conditions 4.2, 4.4, 4.5, 4.6, 4.7, 4.19, 4.20, 4.21, 13.22, and 13.33 only. |
| J.R. Simplot, Pocatello, Idaho | T1-2017.0024 | 3/29/2023 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit conditions 15.9, 15.10, 15.11, 15.19, 15.20, 15.21, 15.22, 15.25, 15.27, 16.6, 16.9, 16.10, 16.19, 16.20, 16.21, 16.22, 16.26, 16.27, 18.22, and 18.23 only. |
| Tamarack Mill LLC, New Meadows, Idaho | T1-2019-0024 | 10/17/2022 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit conditions 5.2, 5.3, 5.5, 5.8, 5.17, 10.22, and 10.23 only. |
| The Amalgamated Sugar Company LLC—Nampa Factory, Nampa, Idaho | P-2018.0011 | 2/15/2023 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit condition 4.8 only. |
| The Amalgamated Sugar Company LLC—Paul Factory, Paul, Idaho | T1-2019-0020 | 11/5/2021 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit conditions 4.3, 4.4, 4.5, 4.7, 4.9, 4.10, 4.11, 4.12, 4.15, 4.16, 4.18, 11.22, and 11.23 only. |
| The Amalgamated Sugar Company LLC—Twin Falls, Twin Falls, Idaho | T1-2016.0017 | 1/21/2022 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Permit condition 4.9 and 5.2 only. |
(e) * * *
| Name of SIP provision | Applicable | State submittal date | EPA approval date | Explanations |
| --- | --- | --- | --- | --- |
| | | | | |
| * * * * * * * | | | | |
| Regional Haze SIP Revision for the Second Implementation Period | State-wide | 8/5/2022, supplemented 5/8/2024 | 9/5/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | |