Outer Continental Shelf Air Regulations
Offshore oil and gas platforms, drilling rigs, and other industrial facilities on the Outer Continental Shelf (OCS) generate significant air emissions — engines, flares, process equipment, fugitive emissions — yet they operate beyond state territorial waters, in a legal space where state air pollution rules don't automatically apply. 40 CFR Part 55 fills that gap, extending Clean Air Act requirements to OCS sources and ensuring that offshore operations don't create air quality problems for nearby coastal communities.
Legal Authority
- 42 U.S.C. § 7627 (Clean Air Act § 328) — Directs EPA to establish requirements controlling air pollution from OCS sources to attain and maintain NAAQS and comply with Prevention of Significant Deterioration requirements; the specific statutory mandate for 40 CFR Part 55
- 40 CFR Part 55 — EPA implementing regulation; establishes the 25-mile proximity rule (mirror-state requirements within 25 miles, federal requirements beyond), state consistency update procedures, delegation to adjacent states, fee structure, and state-specific incorporated requirements by state
Key Mechanics
40 CFR Part 55 extends Clean Air Act requirements to Outer Continental Shelf sources — offshore oil and gas platforms, drilling rigs, and other industrial facilities operating beyond state territorial waters (generally beyond 3 miles). The core design principle is geographic proximity: OCS sources within 25 miles of a state's seaward boundary must comply with the adjacent state's applicable air quality requirements as if the facility were located onshore in that state — California platforms face CARB requirements, Louisiana platforms face Louisiana requirements. OCS sources beyond 25 miles are subject only to federal baseline requirements (NAAQS attainment, PSD thresholds, major source standards). EPA maintains the mirror-state relationship through annual consistency reviews that incorporate updated state requirements into § 55.14 by reference. Adjacent state governors may petition to take over OCS enforcement for their coastal waters through delegation agreements, though EPA retains authority over consistency updates regardless. New major OCS sources must undergo PSD pre-construction review (BACT analysis) the same as major onshore sources. The Gulf of Mexico west of 87.5° W longitude operates under a separate state consistency review process.
Current Rule (2026)
| Parameter | Value |
|---|---|
| Citation | 40 CFR Part 55 |
| Issuing agency | EPA |
| Statutory authority | 42 U.S.C. § 7401 (Clean Air Act § 328) |
| Applies to | All OCS sources — offshore platforms, rigs, and facilities on the Outer Continental Shelf (generally beyond 3-mile state territorial limit) |
| Within 25 miles of state boundary | Mirror applicable state and local air quality requirements |
| Beyond 25 miles | Federal requirements (federal reference methods, EPA operating permits) |
| Permit fees | OCS sources pay operating permit fees under 40 CFR Part 71 |
What This Rule Does
Clean Air Act § 328 requires EPA to establish requirements controlling air pollution from OCS sources to attain and maintain national ambient air quality standards (NAAQS) and to comply with Prevention of Significant Deterioration (PSD) requirements. 40 CFR Part 55 implements this directive.
The central design principle is geographic proximity: OCS sources within 25 miles of a state's seaward boundary are subject to the onshore state's air quality requirements — whatever the adjacent coastal state requires of onshore sources applies to the offshore platform as if it were located in that state. This prevents offshore operators from escaping California, Texas, or Gulf State air rules simply by being a few miles offshore. OCS sources beyond 25 miles are subject to federal requirements only.
Key Provisions
- § 55.1 — Statutory authority and scope: establishes that Part 55 implements Clean Air Act § 328(a)(1) (42 U.S.C. § 7627); applies to all OCS sources except those in the Gulf of Mexico west of 87.5 degrees W longitude, which are covered under separate state consistency reviews
- § 55.10 — Fees: OCS sources within 25 miles pay operating permit fees under 40 CFR Part 71 to EPA; EPA collects cost-recovery fees from the state of comparable application; sources beyond 25 miles follow the adjacent state's fee structure where applicable
- § 55.11 — Delegation: adjacent state governors may request authority from EPA to implement and enforce Part 55 requirements within (and in some cases beyond) 25 miles of their seaward boundary; states can take over administration for OCS sources the same way states take over CAA programs onshore; however, EPA retains the authority to implement §§ 55.5, 55.11, and 55.12 (consistency updates) even after delegation
- § 55.12 — Consistency updates: EPA continuously updates Part 55 to incorporate new and revised state air requirements as they are adopted, maintaining the mirror-state relationship; within 25 miles of a state boundary, EPA conducts consistency reviews at least annually to ensure the incorporated state requirements are current; the rule lists each coastal state's applicable requirements by incorporation by reference
- § 55.13 — Federal requirements for all OCS sources: establishes baseline federal requirements (NAAQS attainment, PSD requirements, major source and major modification thresholds) that apply to all OCS sources as a floor; if a state requirement conflicts with a federal requirement and a source cannot comply with both, the more stringent requirement prevails
- § 55.14 — State-specific requirements within 25 miles: the operational core of Part 55 — lists, by state, each set of state air quality regulations incorporated as OCS source requirements; covers all major coastal states (Alaska, California, Gulf states, Atlantic Coast states); an OCS source off Louisiana must comply with Louisiana air quality requirements; an OCS source off California must comply with California's more stringent rules
How It Affects You
Offshore oil and gas operators must identify which state's 25-mile zone they operate in (if any) and comply with that state's air permitting requirements as if they were a land-based facility. An offshore platform off the California coast faces California CARB requirements — some of the most stringent in the country. Platforms in the Gulf of Mexico west of 87.5° W longitude (the Texas/Louisiana OCS) operate under a separate review process tied to Gulf state requirements.
New OCS construction triggering major source thresholds must undergo PSD review (Prevention of Significant Deterioration) — the pre-construction review process requiring best available control technology (BACT) analysis — the same as a new major industrial source onshore.
Air quality management districts and states can negotiate with EPA to take over OCS enforcement for their adjacent waters, giving them direct regulatory authority over the platforms visible from their coastline.
Statutory Authority
This rule implements:
- 42 U.S.C. § 7401 — the Clean Air Act; specifically § 328 directs EPA to establish OCS air pollution control requirements to attain NAAQS and comply with PSD provisions
Recent Rulemakings
- 90 FR 35400 (approx. 2025) — consistency updates incorporating latest state air regulations into § 55.14; EPA routinely updates this section as states revise their programs
- The core framework of Part 55 has been stable since 1992; most updates are consistency amendments reflecting changes to state air quality plans incorporated by reference
Pending Action
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