wa-26-20-005: Ecology, Department of — WSR 26-20-005

WSR 26-20-005 (26-20)WSR 26-20-005PROPOSED RULESDEPARTMENT OF ECOLOGY[Order 25-06—Filed September 24, 2026, 7:41 a.m.]Original Notice.Preproposal statement of inquiry was filed as WSR 25-23-111.Title of Rule and Other Identifying Information: The department of ecology (ecology) is proposing amendments to chapter 173-476 WAC, Ambient air quality standards; and chapter 173-400 WAC, General regulations for air pollution sources.For more information on this rule making, visit https://ecology.wa.gov/regulations-permits/laws-rules-rulemaking/rulemaking/wac-173-476-400.Hearing Location(s): On November 10, 2026, at 10:00 a.m., via webinar. Register and see instructions at https://waecy-wa-gov.zoom.us/meeting/register/qptkzNj3SUSmk_oHAE2o6Q#/registration; or join by phone 253-205-0468, Meeting ID 846 0699 5925.Date of Intended Adoption: February 17, 2027.Submit Written Comments to: Linda Kildahl, Department of Ecology, Air Quality Program, 300 Desmond Drive S.E., Lacey, WA 98503, email linda.kildahl@ecy.wa.gov, beginning September 24, 2026, at 12:00 a.m., by November 17, 2026, at 11:59 p.m.Assistance for Persons with Disabilities: Contact Linda Kildahl, phone 360-706-3038, Washington relay service or TTY call 711 or 877-833-6341, email linda.kildahl@ecy.wa.gov, by November 2, 2026.Purpose of the Proposal and Its Anticipated Effects, Including Any Changes in Existing Rules: Chapter 173-476 WAC: This proposal aligns the state ambient air quality standards in the rule with the strengthened national ambient air quality standards (40 C.F.R. Part 50) for fine particulate matter (PM2.5) and sulfur dioxide (SO2) adopted by the Environmental Protection Agency (EPA) in 2024. Additionally, the proposal removes two less protective SO2 standards that were revoked by EPA in 2010.Chapter 173-400 WAC: This rule making updates the cause or contribute threshold values, also known as significant impact levels (SILs), and associated provisions used in the permitting of proposed new or modified sources of air pollution. The amendments align the impact levels in the rule with updated impact levels recommended by EPA. Reasons Supporting Proposal: Chapter 173-476 WAC: Amendments are needed to align the state ambient air quality standards with the national ambient air quality standards (40 C.F.R. Part 50) for PM2.5 and SO2. In March 2024, EPA lowered the maximum allowable annual level of PM2.5 from 12 micrograms per cubic meter of air to nine micrograms per cubic meter of air. The new primary PM2.5 standard better protects human health. For SO2, amendments are needed to reflect a new secondary annual standard of 10 parts per billion adopted by EPA in December 2024. The new secondary SO2 standard better protects ecosystems and welfare. Amendments are also needed to remove two outdated primary SO2 standards that were revoked by EPA in 2010 and no longer apply in Washington. Chapter 173-400 WAC: EPA has revised recommended SILs for several pollutants since ecology adopted the impact levels into rule and now amendments are needed to align the rule with the EPA recommendations. Amending the provisions associated with SILs will also remove a conflict with language in the rule and the outcome of a federal court decision on the use of SILs in permitting decisions.Statutory Authority for Adoption: Chapter 70A.15 RCW, Washington Clean Air Act.Statute Being Implemented: Chapter 70A.15 RCW, Washington Clean Air Act.Rule is necessary because of federal law and federal court decision, 42 U.S.C. Chapter 85; Sierra Club v. EPA, 705 F.3d 458 (D.C. Cir. 2013).Name of Proponent: Department of ecology, governmental.Name of Agency Personnel Responsible for Drafting: Linda Kildahl, Lacey, 360-706-3038; Implementation: MengChiu Lim, Lacey, 360-995-3448; and Enforcement: Philip Gent, Lacey, 360-918-6922.A school district fiscal impact statement is not required under RCW 28A.305.135.A cost-benefit analysis is required under RCW 34.05.328. A preliminary cost-benefit analysis may be obtained by contacting Linda Kildahl, 300 Desmond Drive S.E., Lacey, WA 98503, phone 360-706-3038, email linda.kildahl@ecy.wa.gov.This rule proposal, or portions of the proposal, is exempt from requirements of the Regulatory Fairness Act because the proposal: Is exempt under RCW 19.85.061 because this rule making is being adopted solely to conform and/or comply with federal statute or regulations. Citation of the specific federal statute or regulation and description of the consequences to the state if the rule is not adopted: The rules are being updated to reflect 2024 revisions to the United States Clean Air Act, 42 U.S.C. § 7401 et seq., national ambient air quality standards. Rule amendments also reflect the District of Columbia circuit court's ruling in Sierra Club v. EPA, 705 F.3d 458 (D.C. Cir. 2013) regarding treatment of new or modified sources with modeled emissions below SILs.Is exempt under RCW 19.85.025(3) as the rules only correct typographical errors, make address or name changes, or clarify language of a rule without changing its effect; and rule content is explicitly and specifically dictated by statute.Is exempt under RCW 19.85.025(4).Explanation of exemptions: Ecology baselines are typically complex, consisting of multiple requirements fully or partially specified by existing rules, statutes, or federal laws. For detailed discussion of the baseline, proposed rule amendments, and impacts of the proposed amendments, see the preliminary regulatory analyses, Publication 26-02-022, for this rule making.Baseline for this rule making: The baseline for our analysis generally consists of existing laws and rules. This is what allows us to make a consistent comparison between the state of the world with and without the proposed rule amendments. Our baseline includes, but is not limited to:•The federal Clean Air Act (42 U.S.C. § 7401 et seq.).•EPA guidance on SILs and cumulative analyses (https://www.epa.gov/nsr/significant-impact-levels-sils-cumulative-analyses. We note that guidance is not typically part of a regulatory baseline beyond being a way that regulations are implemented, but in this state-federal context, federal guidance plays a role in maintaining Washington's delegated authority to enforce the Clean Air Act.).•Court rulings interpreting the law: Sierra Club v. EPA (705 F.3d 458 (D.C. Cir. 2013)).•The Washington Clean Air Act (chapter 70A.15 RCW).•The existing ambient air quality rule (chapter 173-476 WAC, Ambient air quality standards).•The existing new source rule (WAC 173-400-113 New sources in attainment or unclassifiable areas—Review for compliance with regulations. Note that this rule making is not proposing to amend other sections of chapter 173-400 WAC, General regulations for air pollution sources).The proposed rule amendments would:•Update ambient air quality standards for:oPM2.5oSO2•Update "cause or contribute" threshold values for:oPM2.5oSO2oNitrogen dioxideoOzone•Remove automatic exemption below "cause or contribute" values to align with court rulings.•Specify when additional analysis may be required when modeled emissions are below "cause or contribute" values.•Make minor edits for clarity and consistency, without material change to requirements.Relevant exemptions: Exemptions under RCW 19.86.061 and 19.85.025(3): For major sources, the proposed amendments align with baseline requirements (chapter 70A.15 RCW) to comply with federal national ambient air quality standards under the federal Clean Air Act (42 U.S.C. § 7401 et seq.; EPA guidance on SILs and cumulative analyses; and Sierra Club v. EPA (705 F.3d 458 (D.C. Cir. 2013))) to retain delegated authority under the federal Clean Air Act. The rule amendments also make wording changes to clarify rule language without material impact to requirements.Exemption under RCW 19.85.025(4): For minor sources, which are covered under the baseline (chapters 173-476 and 173-400 WAC), ecology used its discretion in developing the proposed rule amendments, but identified that no existing businesses would incur compliance costs as a result of the proposed rule amendments; only one large business is likely to incur any future costs.Impact on businesses: We analyzed the compliance costs of the adopted rule amendments in chapter 3 of the preliminary regulatory analyses for this rule making. Based on past new source applications, we estimated that one facility every two years would need to perform additional analysis (cumulative impact analysis) under the parts of the proposed rule within ecology's discretion. Other impacts would come from federal law with which we are required to comply under RCW 70A.15.1005. In analyzing new source application data, we identified that new emissions sources with attributes similar to a single facility in our dataset (that would have needed to perform additional cumulative impact analysis if the proposed amendments had been in force when that facility submitted its application) would need to undergo this additional analysis. The existing business that owns and runs this facility employs more than 50 people and moreover does not need to undergo any additional analysis itself as an existing source. (Only new sources or modifications would incur these additional analytic costs.) As future affected facilities would likely have similar attributes, it is likely they would employ similar numbers of employees. This rule making is therefore exempt from further analysis under the Regulatory Fairness Act, per RCW 19.85.025(4), as the proposed rule amendments do not impose compliance costs on existing businesses and are not likely to affect small businesses in the future.Scope of exemption for rule proposal:Is fully exempt.September 24, 2026Heather R. BartlettDeputy DirectorRDS-7360.1AMENDATORY SECTION(Amending WSR 25-05-042, filed 2/12/25, effective 3/15/25)WAC 173-400-113Requirements for new sources in attainment or unclassifiable areas—Review for compliance with regulations.WAC 173-400-110, 173-400-111, 173-400-112, and ((173-400-113))this section apply statewide except where a permitting authority has adopted its own new source review regulations. The permitting authority that is reviewing an application to establish a new source or modification in an attainment or unclassifiable area shall issue an order of approval if it determines that the proposed project satisfies each of the following requirements:(1) The proposed new source or modification will comply with all applicable new source performance standards, national emission standards for hazardous air pollutants, national emission standards for hazardous air pollutants for source categories, emission standards adopted under chapter 70A.15 RCW and, for sources regulated by an authority, the applicable emission standards of that authority.(2) The proposed new source or modification will employ BACT for all pollutants not previously emitted or whose emissions would increase as a result of the new source or modification.(3) Allowable emissions from the proposed new source or the allowable increase in emissions from the proposed modification will not cause or contribute to a violation of any ambient air quality standard.(a) If the modeled concentrations of allowable emissions from the proposed new source or the increase in emissions from the proposed modification ((are below))exceed the levels in Table 4a of this section, ((the proposed source does not contribute to a violation of an ambient air quality standard))a cumulative impact analysis must be provided.(b) If the cumulative impact analysis in (a) of this subsection indicates that a violation of an ambient air quality standard will occur, the proposed new source or modification will be considered to cause or contribute to a violation of that standard.(c) A permitting authority may require a cumulative impact analysis even if modeled values do not exceed the values in Table 4a of this section if there is information that indicates the impact of the proposed new source or modification could result in a violation of an ambient air quality standard when added to the impact of nearby sources or existing background concentrations.(4)(a) If the projected impact of the allowable emissions from the proposed new major stationary source (as defined in WAC 173-400-810) or ((the projected impact of)) the allowable emissions increase ((in allowable emissions)) from the proposed major modification (as defined in WAC 173-400-810) at any location within a nonattainment area ((does not exceed the following levels))exceeds the values in Table 4a of this section for the pollutants for which the area has been designated nonattainment, ((then)) the proposed new source or modification will ((not)) be considered to cause or contribute to a violation of an ambient air quality standard:Table 4a:Cause or Contribute Threshold Values ((for Nonattainment Area Impacts))PollutantAnnual Average24-Hour Average8-Hour Average3-Hour Average1-Hour AverageCO---0.5 mg/m3- 2 mg/m3SO21.0 µg/m35 µg/m3-25 µg/m3((30))7.86 µg/m3PM101.0 µg/m35 µg/m3---PM2.5((0.3))0.13 µg/m31.2 µg/m3---NO21.0 µg/m3---((-))7.5 µg/m3O3--1.0 ppb--(b) If the projected impact of the allowable emissions from the proposed new major stationary source (as defined in WAC 173-400-810) or ((the projected impact of the increase in)) allowable emissions increase from the proposed major modification (as defined in WAC 173-400-810) results in a projected impact at any location inside a nonattainment area above the appropriate value in Table 4a of this section, the owner or operator may use ((an)) offsetting emission reductions or other method identified in 40 C.F.R. Part 51 Appendix S, Sections III and IV.A which reduce the projected impacts to the ((above)) values in Table 4a or less.(c) If the owner or operator of the proposed new major stationary source or proposed major ((source proposed to be modified))modification is unable to reduce emissions or obtain offsetting emissions reductions adequate to reduce modeled impacts ((below))to the values in Table 4a of this section or less, ((then)) the permitting authority shall deny approval to construct and operate the proposed new major stationary source or major modification.(5) If the proposal is a new major stationary source or a major modification as defined in WAC ((173-400-720))173-400-710, then it must also comply with WAC 173-400-700 through 173-400-750.RDS-7361.1AMENDATORY SECTION(Amending WSR 16-12-099, filed 5/31/16, effective 7/1/16)WAC 173-476-020Applicability.(1) The provisions of this chapter apply to all areas of the state of Washington.(2) All federal regulations referenced in this regulation are adopted as they exist on ((January 1, 2016))December 31, 2024.AMENDATORY SECTION(Amending WSR 13-24-010, filed 11/21/13, effective 12/22/13)WAC 173-476-110Ambient air quality standards for PM-2.5.(1) Standards for PM-2.5.(a) The three-year average of the annual arithmetic mean concentration of PM-2.5 must not exceed ((12.0))9.0μg/m3.(b) The three-year average of the ((ninety-eighth))98th percentile ((twenty-four))24-hour average concentration of PM-2.5 must not exceed 35 μg/m3.(2) Measurement method. The levels of PM-2.5 in the ambient air must be measured by:(a) A FRM based on 40 C.F.R. Part 50, Appendix L and designated according to 40 C.F.R. Part 53; or(b) A FEM designated according to 40 C.F.R. Part 53.(3) Interpretation method. The interpretation method found in 40 C.F.R. Part 50, Appendix N must be used.AMENDATORY SECTION(Amending WSR 13-24-010, filed 11/21/13, effective 12/22/13)WAC 173-476-130Ambient air quality standards for sulfur oxides (sulfur dioxide).(1) Standard for sulfur oxides (measured as sulfur dioxide).(a) Annual. The annual average concentration for sulfur oxides in the ambient air must not exceed ((0.02 ppmv))10 ppbv in a calendar year.(b) ((Twenty-four-hour. The twenty-four-hour average concentration for sulfur oxides in the ambient air must not exceed 0.14 ppmv more than once per calendar year. The twenty-four-hour averages must be determined from successive nonoverlapping twenty-four-hour blocks starting at midnight each calendar day.(c))) Three-hour. The three-hour average concentration for sulfur oxides in the ambient air must not exceed 0.5 ppmv more than once per calendar year. The three-hour averages must be determined from successive nonoverlapping three-hour blocks starting at midnight each calendar day.(((d)))(c) One-hour. The three-year average of the annual ((ninety-ninth))99th percentile of the daily maximum one-hour average concentrations for sulfur oxides in the ambient air must not exceed 75 ppbv.(2) Measurement method. The levels of sulfur oxides must be measured as sulfur dioxide by:(a) A FRM based on 40 C.F.R. Part 50, Appendix A-1 or A-2; or(b) A FEM designated according to 40 C.F.R. Part 53.(3) Interpretation methods.(a) The annual arithmetic mean is based on the average of hourly data. To be used in calculating the annual average, the hourly data must be at least ((seventy-five))75 percent complete in each calendar quarter of the year.(b) The interpretation method for the ((twenty-four))24-hour average found in 40 C.F.R. Part 50.4(d) must be followed.(c) The interpretation method for the three-hour average found in 40 C.F.R. Part 50.5(c) must be followed.(d) The interpretation method for the one-hour average found in 40 C.F.R. Part 50, Appendix T must be followed.(4) Rounding of values.(a) The annual arithmetic mean and ((twenty-four))24-hour averages must be rounded to two decimal places. Fractional parts equal to or greater than 0.005 ppmv must be rounded up.(b) The three-hour standard averages must be rounded to one decimal place. Fractional parts equal to or greater than 0.05 ppmv must be rounded up.(((5) Sunset provision. The ambient standards in WAC 173-476-130 (1)(a) and (b) are no longer applicable in a specific area one year after the effective date of the EPA's designation of attainment status of that area for the standard in WAC 173-476-130 (1)(d) and 40 C.F.R. 50.17.))