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Applicability Determination Index

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The Environmental Protection Agency (EPA) currently issues over 100 letters or memoranda per year on Clean Air Act (CAA) applicability or monitoring issues under the New Source Performance Standards (NSPS, 40 CFR Part 60) and the National Emission Standards for Hazardous Air Pollutants (NESHAP, 40 CFR Parts 61 and 63) programs. These written responses are broadly termed “applicability determinations”. The general provisions of 40 CFR Parts 60 and 61 provide that a source owner or operator may request a determination of whether certain intended actions constitute the commencement of construction, reconstruction, or modification (“applicability determinations”); or seek permission to use monitoring or record keeping which is different from the promulgated NSPS and NESHAP standards (“alternative monitoring”). EPA issues applicability determinations to a particular source pursuant to 40 CFR Part 63, even though the general provisions do not contain a specific provision under which source owners or operators may request determinations.

To ensure national consistency in implementing the NSPS and NESHAP programs, EPA Headquarters has maintained a compilation of such letters and memoranda since they were first issued. This compilation is currently available on the Applicability Determination Index (ADI) database Web site. The ADI also contains “regulatory interpretations” which are written responses that apply to the broad range of NSPS and NESHAP regulatory requirements as they pertain to a whole source category; and applicability determinations issued pursuant to the chlorofluorocarbons (CFC) regulations, cited in 40 CFR Part 82.

The ADI, a computerized database of such letters and memoranda, allows users to search by date, office of issuance, subpart, citation, control number, or string word searches. The Office of Enforcement and Compliance Assurance (OECA), Compliance Assessment and Media Programs Division (CAMPD) maintains the ADI database and provides guidance (PDF) (107 pp, 1.51 MB, About PDF) (February 1999) on how to review and issue CAA applicability determinations.

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