U.S. EPA Finalizes Revisions to Appendix W Modeling Guidelines

On November 20, 2024, the United States Environmental Protection Agency (U.S. EPA) published the final rule revising 40 CFR Part 51 Appendix W: Guideline on Air Quality Models (Appendix W). Appendix W outlines the U.S. EPA preferred models for air quality modeling as well as the recommended approaches for using the models for regulatory permit applications. The revisions proposed in Appendix W were around four main areas:

• Changes to modeling procedures for mobile sources of emissions
• Addition of another Tier 3 screening technique for Nitrogen Dioxide (NO₂)
• Incorporation of the Coupled Ocean-Atmosphere Response Experiment (COARE) algorithm into AERMET for use in overwater air quality modeling
• Updates to the guidance for developing background concentrations

The revisions to Appendix W include adding a new source type in AERMOD called RLINE. The RLINE model was originally developed as a standard-alone model and was incorporated into AERMOD in 2019 as a “BETA” option. The change to Appendix W is to remove the BETA tag, thus making the RLINE source type available for regulatory modeling of mobile sources. As part of the revisions U.S. EPA will still allow mobile sources to be modeled using the AREA, LINE or VOLUME source types, giving projects flexibility in selecting the source type for regulatory modeling.

U.S. EPA has also revised Appendix W to include an additional Tier 3 screening technique for NO₂. The three-tiered approach for NO₂ modeling addresses the conversion of emissions oxides of nitrogen (NO_x) to NO₂, and includes the following:

Tier 1 – assuming that all emitted NO_x from a source is converted to NO_2.

Tier 2 – uses the Ambient Ratio Method 2 (ARM2), which applies a ratio converting a portion of NO_x to NO₂

Tier 3 – apply the Ozone Limiting Method (OLM) or Plume Volume Molar Ratio Method (PVMRM), which incorporate ozone data and source-specific NO₂ to NO_x in-stack ratios.

As part of the revision, U.S. EPA is including the Generic Reaction Set Method (GRSM) as a third regulatory non-default Tier 3 screening option. GRSM differs from OLM and PVMRM as it considers the travel time and chemical reaction time of the plume. GRSM requires ozone and NO_x concentrations from a nearby representative monitor as a required input and also allows NO₂ concentrations as an optional input. The revision effectively installs GRSM as another available option when modeling NO₂ in regulatory permit applications. As a reminder, use of any Tier 3 option requires consultation with the appropriate U.S. EPA Regional Office and the reviewing authority.

The third revision to Appendix W incorporates the COARE algorithm into AERMET as a non-default option for use in overwater environments. The current preferred model for overwater air modeling analyses is the Offshore Coastal Dispersion (OCD) model. OCD was developed in the 1980s and has not been replaced by AERMOD because AERMOD is not able to handle shoreline fumigation or platform downwash. However, OCD has many limitations that make it difficult to use for overwater modeling analyses (e.g., construction and operation of offshore wind farms) and as a result many permit applicants were seeking to use AERMOD instead of OCD. In order to use AERMOD in an overwater environment, applicants used the COARE algorithms to help develop the meteorological inputs reflective of overwater meteorology. The COARE algorithms were implemented via a stand-alone program that had not been updated since 2012.

The revisions to Appendix W incorporate the COARE algorithms into AERMET, the meteorological preprocessor to AERMOD. This change will help maintain the algorithms so they stay compatible with the most recent version of AERMOD and will eliminate the alternative model demonstration requirements for using AERMOD in overwater situations when shoreline fumigation and platform downwash effects are adequately accounted for in the modeling demonstration.

The final revision to Appendix W focused on refining the recommendations around background concentrations. Appendix W previously recommended that when background concentrations do not adequately include the impacts of nearby sources, that sources that cause a “significant concentration gradient” in the vicinity of the source under consideration should be included in the air quality modeling analysis. However, there was no guidance or recommended approach for determining what a significant concentration gradient was. The revisions to Appendix W help to clarify this; in addition, U.S. EPA released a separate guidance document entitled “Guidance on Developing Background Concentrations for Use in Modeling Demonstrations”. This guidance document details the framework that should be used to help sources select a credible and representative background concentration for regulatory air modeling analyses. As it is guidance and not part of the Appendix W rule itself it could possibly be revised without going through a formal rulemaking, making it easier to update.

Lastly, U.S. EPA updated AERMOD along with several of the other programs used to develop inputs for AERMOD. U.S. EPA updated:

• AERMOD (v24142),
• AERMET (v24142),
• AERMAP (v24142) (the terrain preprocessor for AERMOD),
• AERSURFACE (v24142) (a processer that determines surface characteristics for AERMET)
• AERPLOT (v24142) (tool for plotting results in Google Earth Format)
• MMIF (v4.1.1) (a tool for converting prognostic meteorological data for AERMOD)

Overall, the revisions to Appendix W are relatively minor, focusing on more specialized regulatory modeling applications, and remain largely unchanged from the draft revisions proposed roughly a year ago. U.S. EPA published the revisions in the Federal Register on November 27, 2024. The effective date for this action is January 28, 2025, with a 1-year transition period. Because the rule falls into the Congressional Review Act lookback period, the rule could potentially be delayed, revised, or even withdrawn completely should the new congress decide to take up such a review.

ALL4 has a team of experienced air dispersion modelers with experience across many source types, from simple sites to offshore wind farms to complex manufacturing facilities. We are well versed in federal and state air dispersion modeling requirements for criteria pollutants and air toxics. Should you have any questions on how these revisions may impact your facility or have an upcoming project that involves air quality modeling, please contact Joe Sabato (jsabato@all4inc.com) or (774)293-8009 to discuss how we can help.

U.S. EPA Releases TANKS 5.1

On October 9, 2024, United States Environmental Protection Agency (U.S. EPA) released version 5.1 of their TANKS software in conjunction with updates to Section 7.1 – Organic Liquid Storage Tanks of the AP-42 Compilation of Air Pollutant Emission Factors. TANKS 5.1 utilizes the formulas in AP-42 Section 7.1 to calculate routine and non-routine losses of volatile organic compounds (VOC) and organic hazardous air pollutants (HAP) from various types of storage tanks. Because the formulas in AP-42 are fairly complex, TANKS 5.1, as with earlier versions of TANKS, is intended to help users quantify organic emissions from tanks more easily. However, U.S. EPA stopped supporting the previous version of TANKS, version 4.09d, several years ago, so the release of TANKS 5.1 is welcome news for anyone who needs to quantify organic emissions from storage tanks.

Those familiar with earlier versions of TANKS will notice some obvious changes in TANKS 5.1, the first and foremost being that TANKS 5.1 is now a web-based program rather than software installed on a computer. Data entered into TANKS 5.1 will generally remain available unless the user clears their browser cache, but it can also be downloaded (and conversely, uploaded). In addition to 100 organic liquids to choose from, the user can also enter custom liquids and mixtures. Meteorological data is available for 250 U.S. cities, but custom meteorological data can be entered as well. While organic emissions calculations were previously limited to routine standing and working losses, TANKS 5.1 can calculate non-routine losses for floating roof landing and tank cleaning events. The program does not calculate the maximum hourly emissions, however.

TANKS 5.1 supports the following types of tanks: vertical and horizontal fixed roof tanks, internal and external floating roof tanks, and domed external floating roof tanks. After selecting the type of tank, the user can enter identifying information (e.g., name, location), physical characteristics (e.g., tank type, size, condition; shell characteristics; roof characteristics; breather vent settings; and control device settings), and contents (e.g., liquid, annual throughput). While intended to simplify the process of carrying out AP-42 Section 7.1 calculations, the user is still required to have detailed information about the tank available, and may need to calculate intermediate values to enter into TANKS 5.1, particularly for custom liquids and mixtures.

TANKS 5.1 generates an Excel workbook with the results of the calculations, which can include speciated data for various compounds. The results for routine losses provide results for intermediate calculations and specify losses from deck fittings, deck seams, and rim seals; however, the results for non-routine losses are not as detailed, providing only the overall loss values. Hopefully, the report will improve in a subsequent version.

A beta version of TANKS 5.0 was available for comment over the summer, and U.S. EPA received many comments identifying errors and suggested improvements. U.S. EPA incorporated many of those comments into version 5.1, but there are many that were designated as possible future enhancements. U.S. EPA’s responses to comments are available on the TANKS website.

As with any software, as TANKS 5.1 begins to be more widely utilized, it’s possible that users will encounter other bugs, issues, or have more suggestions for improvements. If you have any questions about TANKS 5.1 or encounter an issue, feel free to reach out to Lindsey Kroos at lkroos@all4inc.com or your ALL4 project manager.

U.S. EPA Finalizes Revisions to the Secondary NAAQS

On December 10, 2024, the United States Environmental Protection Agency (U.S. EPA) issued its finalized revisions to the secondary National Ambient Air Quality Standards (NAAQS). The relatively minor proposed changes, first proposed in April 2024, only affect the secondary standards for sulfur dioxide (SO₂), retaining the secondary standards for nitrogen dioxide (NO₂) and particulate matter (PM). Primary NAAQS are designed to protect public health, while secondary NAAQS protect public welfare, protecting damage to crops, vegetation, and animals, as well as decreased visibility.

The finalized changes:

In the original proposal, U.S. EPA recommended replacing the previous secondary NAAQS for SO₂, which was set at 500 parts per billion (ppb) or 1,310 micrograms per cubic meter (µg/m³) averaged over a three-hour daily maximum, with a new secondary standard based on an annual average in the range of 10 to 15 ppb (26-39 µg/m³) averaged over three years. In the final rule, U.S. EPA chose the low end of the range, 10 ppb, or 26 µg/m³.

Additionally, while U.S. EPA had proposed to retain the current secondary NAAQS for NO₂ and PM, they requested comment on potentially lowering the secondary annual NO₂ NAAQS from 53 ppb down to a range of 35 to 40 ppb, and the secondary annual PM NAAQS from 15 to 12 µg/m³. Ultimately however, U.S. EPA chose to retain those secondary NAAQS as they are.

Also, as was indicated in the proposed revisions, U.S. EPA concluded that no new emissions reductions would be necessary under the revised annual SO₂ secondary NAAQS, after an air quality analysis performed by U.S. EPA using monitored ambient SO₂ data from 2017 to 2023 concluded that those monitors in compliance with the primary one-hour SO₂ NAAQS would already comply with the new secondary annual NAAQS, and that for those monitors showing an exceedance in the one-hour primary NAAQS, the emission reductions necessary to bring the monitor into compliance with the primary NAAQS would also ensure compliance with the new secondary NAAQS.

Finally, while U.S. EPA is not making changes to the New Source Review (NSR) permitting program, it issued a Prevention of Significant Deterioration (PSD) memorandum describing an alternative approach to directly modeling against the new secondary NAAQS, that involves preparing a technical analysis that will provide a justification for relying on the demonstration of compliance with the one-hour primary SO₂ NAAQS as sufficient to comply with the new annual secondary NAAQS. As a result, the burden from an air dispersion modeling perspective is actually lessened by the revision of the secondary NAAQS: rather than having to model both one-hour and three-hour SO₂, an applicant would now model just one-hour SO₂ and reference the memorandum to justify that compliance with the secondary NAAQS was satisfied.

The revised standard will take effect 30 days after publication in the federal register, which has not happened yet as of this writing. It should be noted that the finalized rule falls within the look back period of the Congressional Review Act (CRA), so the new administration will have the ability to review and potentially stay and reverse or revise the rule.

What are the impacts of the final rule?

As was discussed in our blog on the proposed rule in April, the finalized rule is a disappointment to environmentalists who sought to use the reconsideration of secondary NAAQS to circumvent the timing of the review of the corresponding primary NAAQS for these pollutants and install more restrictive standards. Some groups were pushing for secondary NAAQS that were more stringent than the primary NAAQS, something that has never occurred and would potentially complicate implementation of the revised NAAQS.

And, although the final rule selected the lower end of the range it sought comment on for the revision to the secondary SO₂ NAAQS, the final rule is less stringent than what was recommended by U.S. EPA staff, and considerably weaker than what was suggested by the Clean Air Scientific Advisory Committee (CASAC). Not only had CASAC suggested significantly lower levels, but also potentially a new approach where the limits would be based on deposition in waterbodies, which again would have complicated compliance demonstrations as no previous NAAQS has ever taken that form.

What do these proposed revisions mean?

Ultimately the final rule, if it survives review under the CRA, will have a limited impact on industry and require little or no action to show compliance with the revised secondary NAAQS.

If you have concerns about the potential implications of the revisions, feel free to contact your ALL4 Project Manager or Rich Hamel. We’ll continue to monitor NAAQS-related developments and report as news develops.

Final Amendments to National Emission Standards for Hazardous Air Pollutants: Rubber Tire Manufacturing

The U.S. Environmental Protection Agency (U.S. EPA) has published final amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Rubber Tire Manufacturing (40 CFR 63, Subpart XXXX) to establish emissions standards for the rubber processing subcategory. The proposed rule was initially published last year on November 16, 2023 and the final rule was published on November 29, 2024.

The Final Amendments

This rule applies to rubber tire manufacturing plants that are major sources of hazardous air pollutants (HAPs), and the changes establish new requirements for the “rubber processing” subcategory, which is defined as “the collection of all rubber mixing processes (e.g., banburys and associated drop mills) that either mix compounds or warm a rubber compound before the compound is processed into components of rubber tires” (89 FR 94886 Section V.A). Simply put, any rubber mixer at your HAP major source facility will be affected by the rule. Any existing source at the time of the proposed rule (i.e., sources that commenced construction or reconstruction on or before November 16, 2023) is required to comply with the new standards by November 29, 2027. Any source that commenced construction or reconstruction after November 16, 2023 must comply with the new standards by November 29, 2024 or upon startup, whichever is later.

Emissions Standards

The U.S. EPA has set limits on total hydrocarbons (THC) and filterable particulate matter (fPM) (or alternatively metal HAPs) to regulate HAP emissions from rubber processing. THC is being used as a surrogate for organic HAP and fPM is being used as a surrogate for metal HAPs. U.S. EPA has set the THC standard for both new and existing sources at 64 grams (g)/megagram (Mg) of rubber processed (1.3×10^5 pound (lb)/million ton (Mton) of rubber processed) which is equivalent to three times the representative detection level (3XRDL). Sources must comply with this limit on a 15-day rolling average basis.

Sources may comply with either an fPM limit as a surrogate for metal HAPs or a metal HAP limit. The standard for metal HAPs is 5.4×10^-2 g/Mg of rubber processed (110 lb/Mton of rubber processed) and the standard for fPM is 3.0 g/Mg of rubber processed (6.0×10³ lb/Mton of rubber processed).

Initial and Continuous Compliance Requirements

Initial compliance with the new emissions limits is to be demonstrated via performance testing within 180 days of startup for new sources and by November 29, 2027 for existing sources. Sources are required to conduct subsequent performance tests every five years. Additionally, U.S. EPA is requiring that a THC continuous emissions monitoring system (CEMS) must be installed at each control device or uncontrolled mixer exit to continuously monitor THC emissions using a monitor that is set with a range of 0 to 50 parts per million by volume (ppmv). Exhaust flow rate measured during the performance test would be used to convert ppmv THC to mass of THC. Sources must also continuously monitor the daily mass of the mixed rubber compound in each mixer. Sources can demonstrate compliance with the 15-day rolling average THC standard in one of three ways:

• For each mixer separately;
• For a group of mixers routed to the same control device or stack; or
• On a facility-wide average basis.

U.S. EPA is also requiring that facilities install and operate a bag leak detection system (BLDS) on any fabric filters used to control fPM/metal HAP emissions from rubber mixing. Additionally, each emissions capture system or enclosure and closed vent system on each rubber processing mixer must be inspected annually to ensure that each system or enclosure vents capture emissions through a closed vent system, except that dilution air may be added to emissions streams for temperature control in a fabric filter. Compliance reports and notifications will be submitted electronically through U.S. EPA’s Compliance and Emissions Data Reporting Interface (CEDRI).

What’s Different from the Proposed Amendments?

Several things have changed between the proposed and final rule, including emissions averaging across mixers, subcategories, and reporting requirements.

Emissions averaging across mixers was introduced in the final rule to account for various mixer and thermal oxidizer configurations. If a facility routes multiple mixers to the same stack or RTO, this newly allowed emissions averaging will help simplify the compliance demonstration.

The standards did change as a result of U.S. EPA’s consideration of additional data. Specifically, the subcategories for silica and non-silica THC standards have been removed and the standards are now equivalent for new sources and existing sources. The THC limit has been raised to 64 g/Mg for all sources from 9.4 g/Mg for existing silica sources, 45.4 g/Mg existing non-silica sources, 2.1 g/Mg new silica sources, and 17.2 g/Mg new non-silica sources. The metal HAP standard dropped from 0.37 g/Mg to 5.4×10^-2 g/Mg and fPM rose from 1.70 g/Mg to 3.0 g/Mg.

The requirement to continuously monitor the firebox temperature and maintain the temperature above the level established during the performance test on a daily average basis for facilities that use a thermal oxidizer was removed from the final rule by U.S. EPA.

U.S. EPA also updated the electronic reporting requirement at 40 CFR §63.6009(k) and §63.6010(g) and (h) to provide an email address to which sources can electronically transmit confidential business information (CBI) to U.S. EPA when submitting compliance reports.

Conclusion

Each HAP major source facility with rubber mixers will need to determine what new standards and requirements apply and develop a compliance plan. Because the standards are quite low, facilities are likely to need additional controls for organic HAP emissions and may need upgraded fabric filters for PM control. ALL4 can assist facilities with understanding these new regulatory requirements, planning for compliance, preparing emissions test plans, reviewing emissions test data, obtaining vendor quotes for new emissions control or monitoring systems, setting up new monitoring systems, establishing electronic compliance systems, and compliance reporting. If you have any questions, feel free to reach out to me at bjohnson@all4inc.com or (502) 874-4500 or to Philip Crawford at pcrawford@all4inc.com or (984) 777-3119.

U.S. EPA Issues Memo on Adjusting Condensable PM Test Results

On November 21, 2024, the U.S. Environmental Protection Agency (EPA) issued a short Memorandum entitled: Condensable PM Adjustment for Ammonium Sulfate Formation in M202 Test Results. The actual correction method is provided by OTM-59, Method for the Correction of Residual Ammonia in Condensable Particulate Matter Samples Collected according to Method 202. The following sections provide background and explain why the memo was needed and what it means.

Background

Method 202 is used to quantify condensable particulate matter (CPM), that is, any material that passes through the heated filter and then condenses within the chilled impinger section or “back-half” of the sampling train. CPM results are then used with filterable PM emissions data to develop emissions rates for total particulate matter (TPM) as well as PM less than 10 microns in diameter (PM₁₀) and PM less than 2.5 microns in diameter (PM_2.5). Like all PM test methods, the actual measurement is gravimetric, meaning that the weight gain in the gas sample (i.e., “front-half” catch, including the filter catch and probe/nozzle rinsate and/or “back-half” impinger catch) is divided by the sample volume collected to derive the results.

The Issue

Ammonia and sulfur dioxide are typically gaseous at stack conditions; both pass through the heated filter, and both can be captured in the water in the back-half chilled impingers. Neither of these gases should be counted as particulate matter but through the miracle of chemistry, once they are dissolved into the impinger water, and a few electrons and protons do their thing, the liquid now contains dissolved ammonium sulfate. When the liquid is recovered, and the water is evaporated, ammonium sulfate, if present, will be part of the resulting solids, with the CPM results biased high due to the presence of ammonia and sulfur dioxide in the stack gas. Now that the annual PM_2.5 National Ambient Air Quality Standard (NAAQS) is very close to the background value in many areas of the country, any high bias in PM test methods is important to resolve and remove.

The Solution

To make the correction, the CPM residue (what’s left after the evaporation step) is first re-dissolved and then analyzed for ammonium and sulfate ions. The amount of ammonium sulfate in the residue is then determined using some quick chemistry and stoichiometry. The final correction is made by subtracting the mass of ammonium sulfate from the gravimetric CPM determination. Voilà, the CPM values are now corrected for ammonia and sulfur dioxide bias.

The Fine Print

U.S. EPA has included a couple of details and prerequisite conditions that must be met for use of the correction:

• The presence of ammonia and sulfur dioxide must be confirmed using independent measurements (Method 320 or other ammonia slip methodology).
• Ammonia must be measured concurrent with the M202 CPM measurement.
• If the presence of ammonia is associated with ammonia injection for NO_X control using selective catalytic reduction (SCR), the ammonia feed rate and SCR inlet and outlet NO_X concentrations must be provided.
• Clarifications regarding applicability:
  • The U.S. EPA memo says: This adjustment is not appropriate for determining compliance with emission limitations that were derived without applying this adjustment methodology. Where this adjustment is sought for a new source, the process … may be applied to an existing similar source, at the discretion of the permitting authority.
  • The new method says: The procedures included in this method and adjustments to CPM measurements described in this method are only intended for use in the context of New Source Review (NSR) permitting on a prospective basis, such as 1) to determine applicability or NSR permitting requirements, 2) support a permit application, or 3) derive emissions limitations in a permit.

The Bottom Line

U.S. EPA acknowledges Method 202 biases under conditions where ammonia and sulfur dioxide are present. In response, they have provided a methodology to correct this bias. This correction can only be used under certain conditions.   Because the final guidance is fairly recent, there has not been much discussion regarding its potential use beyond what U.S. EPA has identified. Given the prerequisites provided by EPA, our initial interpretation regarding use of the ammonium sulfate bias CPM correction is provided below:

	Good to Go	Unclear	Not Allowed
Compliance with Existing NSR PM10/PM2.5 Limit Derived from M202 Uncorrected Data			❌
Compliance with NSPS or NESHAP PM10/PM2.5 Standard			❌
Compliance with NSR Limit Derived from Corrected M202 Data	✔️
Compliance with a PM10/PM2.5 Limit Established using Dispersion Modeling
Compliance with a State Implementation Plan (SIP) PM10/PM2.5 Limit or Standard
Correcting M202 PM10/PM2.5 Data in a Visibility or NAAQS Modeling demonstration
Establishing an NSR PM10/PM2.5 Limit Derived from Corrected M202 Data	✔️

ALL4 can help you design and manage a stack test program, evaluate results, develop emissions factors and emissions inventories, and demonstrate compliance with air quality regulations and standards. If you have any questions or concerns about Method 202, or other aspects of PM measurement, feel free to contact Roy Rakiewicz (rrakiewicz@all4inc.com) or Gene Youngerman (eyoungerman@all4inc.com).

References and More Information

The memo summarized herein: Condensable PM Adjustment for Ammonium Sulfate Formation in M202 Test Results; FROM: Richard A. Wayland, Director, Air Quality Assessment Division; TO: Air Division Directors; 21 November 2024

OTM-59, Method for the Correction of Residual Ammonia in Condensable Particulate Matter Samples Collected according to Method 202; Undated

U.S. EPA Releases Proposed Updates to Stationary Combustion Turbines NSPS

On November 22, 2024, U.S. Environmental Protection Agency (EPA) proposed the first of what is expected to be three new or revised rules related to the emissions of criteria pollutants, air toxics, and greenhouse gasses (GHG) for stationary combustion turbines. The proposed update to the New Source Performance Standards (NSPS) for Stationary Gas and Combustion Turbines (40 CFR Part 60, Subparts GG and KKKK and the proposed new KKKKa) lowers the standards for the emissions of nitrogen oxides (NO_X) for most new, modified, and reconstructed stationary combustion turbines, while keeping the current standards for sulfur dioxide (SO₂) emissions the same.

What Sources are Subject to the Proposed Rules?

The new and revised Part 60 rules would apply to all stationary combustion turbines with a base load rating of greater than 10 million British thermal units per hour (MMBtu/hr) heat input, except for those classified as emergency combustion turbines, including emergency-standby combustion turbines, military combustion turbines, and firefighting combustion turbines. The standards of performance codified in 40 CFR Part 60, Subpart KKKKa, once promulgated, would be directly applicable to affected sources that begin construction, modification, or reconstruction after the date of publication of the proposed standards in the Federal Register. The proposed updates to Subparts GG and KKKK would apply to the sources covered by those rules immediately upon promulgation.

Proposed Changes to Subparts GG and KKKK

U.S. EPA is proposing two changes to Subparts GG and KKKK:

• Exemptions for turbines subject to more stringent standards (e.g., stationary combustion turbines at refineries subject to Subpart J or Ja).
• Allowing turbines subject to Subpart GG or KKKK to petition the Administrator to comply with Subpart KKKKa.

Proposed New Subpart KKKKa

The proposed new Subpart KKKKa reflects the following:

• Development of a new structure for subcategories, some of which mirror the subcategories for combustion turbines in Subpart TTTTa.
• Determination that the use of combustion controls with the addition of post-combustion selective catalytic reduction (SCR) is the best system of emissions reduction (BSER) for most combustion turbines.
• Lower the NO_X standards of performance for several subcategories based on the application of SCR as BSER.
• More protective NOx standards for affected new sources that plan to fire or cofire hydrogen, ensuring that these units have the same level of control for NOx emissions as sources firing natural gas or non-natural gas fuels.

U.S. EPA is also proposing to revise the definition of stationary combustion turbine. This change would affect the determination of whether a unit is new or reconstructed. The new language would clarify that the test for determining if an affected facility is a new source would be based on whether the combustion turbine portion of the affected facility is entirely replaced. The reconstruction determination would be based on whether the fixed capital cost of the replacement of the combustion turbine engine portion exceeds 50% of the fixed capital cost that would be required to install only a comparable new combustion turbine engine portion of the affected facility. This change excludes the heat recovery steam generator (HSRG) and duct burner at combined cycle (CC) and combined heat and power (CHP) facilities. U.S. EPA’s reasoning is that the combustion turbine engine itself is the primary source of emissions and that it is appropriate that when CC and CHP facilities undertake major capital investments in the combustion turbine engine portion of the facility, they should invest in emissions control equipment as well.

Subcategorization of Gas-Fired Stationary Combustion Turbines

U.S. EPA is proposing revised NO_X emissions limits based on three size-based subcategories that reflect consideration of the performance of different combustion turbine designs and current NOx control technologies. Those categories are:

• Large combustion turbines: units with a base load heat input rating > 850 MMBtu (approximately 85+ megawatt or MW)
• Medium combustion turbines: units with a base load heat input rating > 250 MMBtu and < 850 MMBtu (approx. 25 to 85 MW)
• Small combustion turbines: units with a base load heat input rating < 250 MMBtu (less than 25 MW)

These sources would then be further subcategorized by low, intermediate, or high loads, based on a 12-month capacity factor, similar to the approach taken in 40 CFR Part 60, Subpart TTTTa (standards of performance for greenhouse gas emissions for new and reconstructed combustion turbine electric generating units):

• High load: capacity factor > 40 percent
• Intermediate load: capacity factor > 20 percent and < 40 percent
• Low load: capacity factor of < 20 percent

While U.S. EPA is proposing to determine that SCR is BSER for most turbines, the proposed rule recognizes that for smaller turbines and those turbines that operate at lower capacities, SCR may not be cost effective and thus proposes non-SCR based emissions rates for certain turbine subcategories, including:

• Small combustion turbines that operate at low and intermediate loads
• Medium combustion turbines that operate at low loads
• Large combustion turbines that operate at low loads

There are also additional subcategories for units running alternative fuel mixes including hydrogen, operating above the Arctic Circle (primarily related to Alaskan oilfield operations), operating at an ambient temperature below 0^o F, and other special operating conditions.

Revised NO_X Emission Limits for Gas-Fired Turbines

U.S. EPA is proposing input-based NO_X standards in the form of pounds per MMBtu (lb/MMBtu) for the new Subpart KKKKa, with compliance determined based on a four-hour rolling average. No changes to the SO₂ standards are proposed and no PM or CO standards were deemed necessary. The following are the proposed BSER and NO_X emissions standards for Subpart KKKKa:

  Table 1—Proposed BSER and NO_X Emissions Standards*

*Review of New Source Performance Standards for Stationary Combustion Turbines and Stationary Gas Turbines – Table 1, Page 66

Note that although U.S. EPA has retained the low load limit of 96 ppm, they are taking comment on whether they should limit the part load standard only to those hours when a combustion turbine is in startup or shutdown. This requirement would impact turbines that are turned down to low loads to either accommodate facility standby conditions or to accommodate an influx of solar energy to the grid.

What Are the Implications of the Proposed Rule?

Based on the lowered emissions rates presented in Table 1 (especially for turbines with a capacity factor greater than 20%), and the establishment of SCR as BSER for several subcategories, in most cases if you are planning a project that will involve the construction, modification, or reconstruction of a combustion turbine, you should expect to either deploy SCR for NO_X control or take permit limits that will significantly limit the amount of operation of the turbine. Either path may significantly increase the capital and/or operating costs of your project above and beyond what would have been necessary in the past.

What about the Administration Change?

The public comment period will begin once the proposed rule is published in the Federal Register and last 90 days, so at this point it will extend into the second Trump administration prior to being finalized. Given that timing, the final rule could be significantly altered to be less stringent, though at this point it could be hard to argue that SCR is not BSER for most large gas-fired turbines with high capacity factors, given its widespread use. The other two gas-turbine rules that are not expected to be proposed until 2025 involve emissions of toxics and GHG.  The GHG proposal is on much more uncertain ground and may never be proposed given the expected deregulatory position of the next U.S. EPA, but some proposed changes to the Part 63 toxics rule are likely, given the data that U.S. EPA has collected recently.

Summary

U.S. EPA believes that the proposed changes to Subparts GG and KKKK and new Subpart KKKKa would result in a reduction of 198 tons of NO_X in 2027 and 2659 tons in 2032, equating to net benefits to society of an estimated $340 million. However, with the administration change, the final rule may look significantly different than the version that has just been proposed.

ALL4 will continue to track this and all regulatory developments closely as the new administration takes over in 2025. If you have questions or concerns about implications of this rule to your project or fleet of stationary combustion turbines, feel free to contact your ALL4 Project Manager or Rich Hamel. We can also help you develop comments on the proposed rule, evaluate permitting risks, and develop a strategy to make the permitting of your project as efficient as possible.

New Lead Regulations in California: A Closer Look at Changes to the California Lead Standard

With new lead standards approved by the California Occupational Safety and Health Standards Board (Cal/OSHA) on February 15, 2024, California is moving toward greater protections for employees exposed to lead. These changes, set to take effect on January 1, 2025, are intended to significantly reduce occupational exposure to lead, enhancing safety protocols across various industries.

Key Changes in the Regulation

The updated regulations for Construction and General Industry, Title 8, Section 1532.1 and 5198 respectively, introduce several critical changes:

• Reduction to the Action Level (AL): The threshold at which an employer is subject to the standard has been drastically lowered by 93%, from 30 micrograms per cubic meter (µg/m³ ) to 2 µg/m³, as an eight-hour time-weighted average.
• Reduction to the Permissible Exposure Limit (PEL): The PEL has been reduced by 80%, from 50 µg/m³ to 10 µg/m³ as an eight-hour time-weighted average.

The key provisions of the regulations are summarized below.

Exposure Assessment and Monitoring: Employers who do not perform an employee exposure assessment and determine actual employee exposure must provide interim protection that consists of respiratory protection, protective clothing and equipment, medical surveillance, training, and posted warning signs. Exposure levels dictate the frequency of monitoring.

New Medical Surveillance and Removal Conditions: If employees may be or are exposed to or above the AL, the employer must institute a medical surveillance program. All medical examinations and procedures required by the program will be provided at no cost to employees, and at a time and place that is reasonable and convenient for employees.

Blood testing is required prior to assignment to work where lead is or is reasonably expected to be present. Monitoring is required every two months for the first six months, then every six months thereafter. If an employee’s blood lead level exceeds 10 micrograms of lead per deciliter of whole blood (µg/dL) on any blood level test, routine or otherwise; the employer is required to conduct further evaluations monthly.

During the monthly evaluation period, medical removal from workplace exposures to lead is required if an employee’s blood lead level (BLL) meets or exceeds any of the following conditions.

• A single BLL above 30 µg/dl (the current standard is 40 µg/dl)
• Two consecutive BLL results above 20 µg/dl
• The average BLL across all tests over a six-month period are greater than 20 µg/dl

Return to work is not allowed until the employee’s BLL result returns to below 20 ug/dl and the average BLL across all tests over a six-month period are below 20.

Workplace Hygiene and other Requirements

General hygiene requirements apply to all employees exposed to lead at or above the new action level, regardless of whether they exceed the PEL. These include:

• Respiratory protection
• Protective clothing and equipment
• Change areas
• Showers
• Eating facilities
• Restricted access to regulated areas
• Institute hygiene and housekeeping practices
• Providing training Maintain monitoring records for 40 years, or the duration of the employment plus 20 years whichever is longer.

The overarching goal of these standards is a target of employee’s blood lead levels below 10 µg/dL , or four times lower than the current federal standard.

Who Will Be Affected by This Change in Regulations?

These changes will impact a wide range of California employees. Industries or activities can include:

• Battery Manufacturers
• Metals Fabrication Employees
• Scrap Industry Employees
• Smelting and Melting Operations
• Welding Professionals
• Automotive Employees
• Material Manufacturing Employees
• Construction Employees

Adoption by Federal OSHA

As California sets pace with these new regulations, many are curious about how Federal OSHA will respond. While federal regulations typically follow a different process, California’s stringent standards may serve as a benchmark. OSHA could consider adopting similar measures, especially if the California model proves successful in reducing lead exposure and enhancing worker safety. However, any federal changes will involve a comprehensive review process, which can take time.

In summary, the new regulations under Title 8, Section 1532.1 and 5198 represent a significant advancement in lead safety standards in California, emphasizing the state’s commitment to protecting its employees. As we approach the implementation date, affected industries should begin preparing for these major changes to ensure compliance and to safeguard employee health.

How ALL4 Can Help

As industries prepare for the changes to California’s lead regulations, ALL4 is here to assist organizations in navigating these updates. We offer a range of services to help you achieve compliance and ensure worker safety:

• Permitting Assistance: Environmental permits may be required or may be in need of modification for new or modified engineering controls necessary to meet the new standard.

• Audit/Gap Analysis: Qualitative analysis to identify processes that may be subject to the standard and comprehensive environmental, health, and safety (EHS) compliance.

• Industrial Hygiene: Qualitative and quantitative analysis to identify and measure workplace hazards through air quality assessments, sound surveys, and contaminant samplings of workplace exposures, including lead.
• Professional Services Support: We offer training programs focused on lead safety and hygiene practices. We can work with your team to develop effective health and safety protocols that align with and address the standard.

Our goal is to support you in adapting to these changes while prioritizing the health and safety of your workforce. If you are interested in learning more about how we can assist, please reach out to pjohnson@all4inc.com or vsparks@all4inc.com.

U.S. EPA Releases Draft Interim Framework for Advancing Consideration of Cumulative Impacts

On November 21, 2024, the U.S. Environmental Protection Agency (U.S. EPA) published the long awaited draft Interim Framework for Advancing Consideration of Cumulative Impacts. This document, while perhaps meant to fulfill the main priority for the Biden administration to present a way to address environmental justice (EJ) issues on projects, has been repeatedly delayed over struggles about potential scientific and legal issues such an analysis would face. These concerns extend all the way back to 2022 when the Science Advisory Board (SAB) was asked to review and report on gaps and barriers in the science and research to executing a cumulative impact analysis (CIA) and implementing EJ in U.S. EPA programs in general.

Much like the draft Guidelines for Cumulative Risk Assessment Planning and Problem Formulation published by U.S. EPA in June of 2023, The document (which was published jointly by the U.S. EPA Office of Environmental Justice and External Civil Rights and the Office of Land and Emergency Management) does not provide specific steps for an agency to use in a CIA. Instead, the document “provides a shared reference point … as they (regulating agencies) determine when and how to analyze and consider cumulative impacts. The framework is not intended to provide detailed instructions on how to consider cumulative impacts in specific contexts, nor does it set the expectation that the principles and approaches to considering cumulative impacts will be applied in every programmatic context.”

The framework is summarized in the Fact Sheet U.S. EPA provided along with the document. The draft framework describes six principles for U.S. EPA to consider related to EJ:

• Centering cumulative impacts work on improving human health, quality of life, and the environment in all communities.
• Focusing on the disproportionate and adverse burden of cumulative impacts.
• Applying a fit-for-purpose approach to assessing and addressing cumulative impacts.
• Engaging communities and incorporating their lived experience.
• Using available data and information to make decisions and take action.
• Operationalizing and integrating ways to consider and address cumulative impacts.

The stated goals for projects adhering to these principles include:

• Communities are safe, healthy, and thriving.
• All people are protected from disproportionate and adverse environmental health effects and hazards, including cumulative impacts of environmental and other burdens.
• No community bears a disproportionate share of adverse environmental and public health impacts.

U.S. EPA offices and programs are to incorporate the framework “as appropriate, feasible and consistent with applicable law, in ways that reflect programmatic and context-specific needs.” The publication of the document opened a 90-day public comment period, which will extend into the second Trump administration, ending on February 19, 2025.

Ultimately, the framework is not likely to survive the arrival of the incoming Trump administration, which seems likely to gut funding for EJ at the federal level, but it remains to be seen if the states that are most active in EJ adopt some of the recommendations in the document into their state-level EJ programs.

Summary

Overall, the draft Interim Framework for Advancing Consideration of Cumulative Impacts provides a broad description of approaches that a regulating agency might take in order to assess the overall impact of a project on a potentially affected community but does not prescribe direct steps that would be required in such an assessment. While it was expected that the framework would lack specifics, agencies will no doubt still have questions as to whether their approaches are appropriate and whether they will stand up to legal challenges.

ALL4 continues to track developments in EJ closely and will continue to do so as the new administration takes over in 2025 as the focus on EJ programs and policies is likely to transition to the states more so than U.S. EPA. If you have questions or concerns about the EJ policies and requirements in your state, feel free to contact your ALL4 Project Manager or Rich Hamel. We’ll continue to monitor EJ guidance from the states and the tools available to evaluate EJ concerns as they develop. We can also help you evaluate permitting risks, from EJ concerns to regulatory issues, and assist in developing a strategy to make the permitting of your project as efficient as possible.