EXPLAINER: Maricopa County aims to revise Rule 338 with spotlight on one polluting semiconductor facility
Phoenix, Arizona: The Maricopa County Air Quality Department (MCAQD) has announced proposed revisions to Rule 338 (see primer below), aimed at further limiting emissions from the semiconductor manufacturing industry. Originally established to curb volatile organic compound (VOC) emissions, Rule 338 will now incorporate additional controls for nitrogen oxide (NOx) emissions.
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What is Rule 338?
Rule 338 (Semiconductor Manufacturing) is a regulation implemented by the Maricopa County Air Quality Department (MCAQD) with the primary objective of limiting emissions of volatile organic compounds (VOCs) from the semiconductor manufacturing industry.
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The US Environmental Protection Agency (EPA) had previously approved Rule 338 into the Arizona State Implementation Plan (SIP) in 1998, recognizing it as meeting the required reasonably available control technology (RACT) standards for VOCs. The last significant update to Rule 338 occurred in 1999.
In light of recent developments, MCAQD is proposing new revisions to ensure that the rule continues to align with modern environmental standards. The initiative comes after the EPA reclassified parts of Maricopa County as a moderate nonattainment area for the 2015 8-hour ozone National Ambient Air Quality Standard as of November 7, 2022.
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What is a Moderate Nonattainment Area?
A moderate nonattainment area is a designation given by the EPA to regions that do not meet the National Ambient Air Quality Standards (NAAQS) for certain pollutants, but whose air quality is closer to meeting the standards than areas classified as serious, severe, or extreme nonattainment. The classification system is part of the Clean Air Act. Parts of Maricopa County were reclassified as a moderate nonattainment area for the 2015 8-hour ozone NAAQS. This means that the county must implement RACT and other required measures to reduce ozone pollution and work towards meeting the national standards. The proposed revisions to Rule 338 are part of this effort to improve air quality by limiting emissions from the semiconductor manufacturing industry.
What is the 8-hour Ozone Standard?
The 8-hour ozone standard measures the concentration of ozone in the air over an 8-hour period. This standard is designed to reflect the potential health impacts of prolonged exposure to elevated ozone levels. As of the latest revision in 2015, the 8-hour ozone standard is set at 70 parts per billion (ppb). This means that the average concentration of ozone over any 8-hour period should not exceed 70 ppb
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Under the Clean Air Act (CAA), areas classified as moderate or higher nonattainment are required to implement RACT for all sources covered by an EPA Control Techniques Guideline (CTG) and for all major sources of VOCs or NOx not covered by a CTG. In response to this reclassification, MCAQD has reviewed non-CTG major sources of NOx and VOCs in the county.
This review identified a significant semiconductor manufacturing facility with major emissions of both VOCs and NOx. These emissions are regulated under a Title V permit that adheres to stringent standards, such as the lowest achievable emissions rate (LAER) and best available control technology (BACT), which are considered stricter than RACT.
However, the VOC and NOx emission regulations for this facility are not currently incorporated into the Arizona SIP. As per Sections 182(b)(2) and 182(f) of the CAA, these RACT requirements must be included in the SIP for non-CTG major sources in moderate nonattainment areas. Consequently, MCAQD is revising Rule 338 to ensure it implements RACT controls for both VOC and NOx emissions.
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What are Sections 182(b)(2) and 182(f) of the CAA?
Both sections aim to reduce ozone pollution by controlling emissions from significant sources of VOCs and NOx in nonattainment areas.
Nonattainment Classification: They specifically target areas that do not meet the NAAQS for ozone, with requirements becoming more stringent as the nonattainment classification increases from moderate to extreme.
Reasonably Available Control Technology (RACT): These sections mandate that states identify and implement RACT for both VOC and NOx sources, ensuring that major emitters use technology and practices that effectively limit emissions.
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Additional proposed revisions to Rule 338 include
Broadening the rule's applicability to process tool operations.
Removing exemptions to maintain stringency in the Arizona SIP version of the rule.
Eliminating definitions of terms no longer used in the rule.
Updating and clarifying language in Section 301 regarding VOC emissions control from semiconductor manufacturing.
Enhancing requirements for solvent cleaning stations and cleaning solvent specifications.
Adding operating and recordkeeping requirements for Point-Of-Use (POU) Combustion Devices.
Updating Emission Control System (ECS) requirements to align with other recently revised rules.
Introducing compliance schedule timeframes for ECS installation, modifications, and good combustion plan submissions.
How dangerous are Nitrogen oxides (NOx)?
Nitrogen oxides (NOx), primarily consisting of nitrogen dioxide (NO2) and nitric oxide (NO), are harmful pollutants that pose several health risks.
Respiratory Effects
Airway Inflammation
Reduced Lung Function
Aggravation of Asthma
Cardiovascular Effects
Heart Disease
Blood Vessel Damage
Other Health Effects
Increased Susceptibility to Infections
Premature Death