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The “Relevant Guidance” index includes a collection of documents issued by EPA organized by topic area. These documents include memoranda, letters, orders, and other types of EPA actions that may provide guidance in one or more forms, such as an adjudication, statement of policy, interpretation of statutes or regulations, or technical information. Each collection is intended to be representative of EPA statements on the topic, but it may not be a complete listing of such statements. The collection does not reflect topic-specific statements that have been expressed by EPA though published rule preambles and Title V petition orders, nor does it include EAB decisions. Each document in the collection speaks for itself, and the inclusion or exclusion of a document in the collection is not intended by EPA to communicate anything more than what is expressed within each document. EPA makes no independent representations on this website as to the extent to which any document in the collection reflects EPA’s current views on the topic, is a final action by EPA, or has any legal effect or precedential weight. Readers are advised to review the documents in the collection and conduct their own assessment of such considerations based on the content of each document and other documents in the collection. Some of the information or views included in the documents may be affected by subsequent changes to the referenced statutory or regulatory language or by court decisions. In addition, many of the statements in these documents are based upon the federal regulations which may differ from rules that govern federally-approved programs. Permitting authorities are advised to consult with their EPA Regional Offices if there is a question as to the relevance of a particular statement to their NSR program.