SUPPLEMENTARY INFORMATION:

I. Applicability Determinations, Regulatory Interpretations, and Alternative Monitoring, and Other Requests

The General Provisions of the NSPS in 40 CFR 60.5 and the General Provisions of the NESHAP in 40 CFR 61.06 allow a source owner or operator to request a determination of whether certain intended actions constitute the commencement of construction, reconstruction, or modification. The General Provisions in 40 CFR part 60 also apply to Federal and EPA-approved state plans for existing sources in 40 CFR^[1] . The EPA's written responses to source or facility-specific inquiries on provisions in 40 CFR parts 60, 61 and 62 are commonly referred to as applicability determinations. Although the NESHAP (40 CFR part 63) regulations contain no specific regulatory provision providing that sources may request applicability determinations, the EPA also responds to written inquiries regarding applicability for the 40 CFR part 63 regulations.

The General Provisions in 40 CFR parts 60 and 63 allow sources to seek permission to use monitoring or recordkeeping that is different from the promulgated requirements.^[2] The EPA's written responses to these inquiries are commonly referred to as alternative monitoring decisions.

The EPA responds to written inquiries about the broad range of regulatory requirements in 40 CFR parts 60 through 63 as they pertain a whole source category, e.g., petroleum refineries, printing and coating operations.^[3] These inquiries may concern the type of source subject to the regulation, or the applicable testing, monitoring, recordkeeping, or reporting requirements required by the regulation. The EPA's written responses to these ( printed page 68511) inquiries are commonly referred to as regulatory interpretations.

The EPA posts our responses to questions about compliance determination, alternative monitoring or recordkeeping, and regulatory determination on the CAA Section 111, 112, and 129 Applicability Determination Dashboard (ADD). The ADD is a data system, accessed via the internet, containing all determinations signed after May 2019. The letters and memoranda on the ADD may be located by facility name, affected subpart, or by response date and is searchable by string word searches.

The EPA previously posted EPA-issued NSPS and NESHAP applicability determinations, alternative monitoring decisions, and regulatory interpretations to the Applicability Determination Index (ADI). All previously issued responses (those signed before June 2019) are posted on the ADI data system available on the internet at: cfpub.epa.gov/​adi/​.

This document comprises a list of 39 such documents added to the ADD on September 22, 2026. Table 1 of this document lists the title of each letter or memorandum. Complete copies of these documents may be obtained from the ADD on the internet at: www.epa.gov/​compliance/​resources-and-guidance-documents-compliance-assistance.

II. Broadly Applicable Alternative Test Method

A. Background

This document identifies four broadly applicable alternative test methods the EPA approved between January 1, 2025, and December 31, 2025. Two additional broadly applicable alternative test methods are identified in this notice, one from 2022 and one from 2024, which were inadvertently omitted from the previous annual notices. See Table 2 of this document for the summary of these broadly applicable alternative test methods. Source owners and operators may voluntarily use these broadly applicable alternative test methods in lieu of otherwise required test methods or related testing procedures. Use of these broadly applicable alternative test methods is not intended to and should not change the applicable emission standards.

The Administrator has the authority to approve the use of alternative test methods for compliance with requirements under 40 CFR parts 59, 60, 61, 63, and 65.^[4] The criteria for approval and procedures for submission and review of broadly applicable alternative test methods are explained in 72 FR 4257 (January 30, 2007), which is available at www.epa.gov/​emc/​broadly-applicable-approved-alternative-test-methods. As explained in the 2007 notice, we will announce approvals for broadly applicable alternative test methods at www.epa.gov/​emc/​broadly-applicable-approved-alternative-test-methods as they are issued. We will also publish a notice in the Federal Register that summarizes the previous year's approvals.

We review numerous source-specific requests for alternatives and modifications to test methods and procedures. Based on these reviews, we sometimes find that test method modifications or alternatives would be equally valid and appropriate to apply to other sources within a particular class, category, or subcategory. Therefore, where either a method modification or an alternative method is clearly broadly applicable to a class, category, or subcategory of sources, we will approve its use for all appropriate sources and situations. When appropriate, approval of broadly applicable test methods is both equitable and efficient.

Use of approved alternative test methods is not mandatory but rather permissive. Sources are not required to employ such a method but may choose to do so in appropriate circumstances. However, as specified in 40 CFR 63.7(f)(5), a source owner or operator electing to use an alternative method for 40 CFR part 63 standards must continue to use the alternative method until otherwise authorized. Source owners or operators should, therefore, review the specific broadly applicable alternative method approval decision at www.epa.gov/​emc/​broadly-applicable-approved-alternative-test-methods before electing to employ any alternative method. Source owners or operators choosing to use a broadly applicable alternative should also notify their regulatory agency prior to using the alternative.

B. Approved Alternative Test Methods and Modifications to Test Methods

Table 2 of this notice summarizes the following information for the six broadly applicable alternative test methods: the alternative method designation number; date of approval letter; test methods affected; sources allowed to use the alternative; and method modifications or alternative methods allowed. For more detailed ( printed page 68513) information, please refer to the complete copies of these approval documents available at www.epa.gov/​emc/​broadly-applicable-approved-alternative-test-methods.

The EPA will revisit approvals of alternative test methods in response to written requests or objections indicating that a particular approved alternative test method either should not be broadly applicable or that its use is not appropriate or should be limited in some way. Any objection to a broadly applicable alternative test method, as well as the resolution of that objection, will be announced at www.epa.gov/​emc/​broadly-applicable-approved-alternative-test-methods and in a subsequent Federal Register notice. If we decide to retract a broadly applicable test method, we will likely consider the need for an appropriate transition period for users either to request case-by-case approval or to transition to an approved method.

91 FR 68510