Mercury/Air Toxics Standard NESHAP for Coal and Oil-Fired Electric Utility Steam Generating Units: National Association of Clean Air Agencies Comments on U.S. EPA Proposed Rule

The National Association of Clean Air Agencies (“NACAA”) submitted June 22nd comments to the United States Environmental Protection Agency (“EPA”) in its docket addressing Proposed National Emission Standards for Hazardous Air Pollutants: Coal and Oil-Fired Electric Utility Steam Generating Units Review of the Residual Risk and Technology Review (“Proposed Rule”). See Docket I.D. NO. EPA-HQ-OAR-2018-0794.

NACAA describes itself as the national, non-partisan, non-profit association of air pollution control agencies in 40 states, including 117 local air agencies, the District of Columbia, and five territories.

EPA’s proposed rule addresses the National Emission Standards for Hazardous Air Pollutants (“NESHAP”) for coal and oil-fired electric steam generating units (“EGUs”). It is commonly denominated the Mercury and Air Toxics Standards (“MATS”) for power plants.

The proposed rule is stated to reflect EPA’s position that developments in control technologies in the performance of power plants requires it to reevaluate the NESHAP.

Examples of key elements of the proposed rule include:

• Further emission limits of non-mercury hazardous air pollutant (“HAP”) metals from existing coal-fired power plants by reducing the emission standard for filterable particulate matter
• Tightening the emission limit for mercy for existing lignite-powered power plants by 70%
• Mandate more stringent emissions monitoring and compliance by requiring coal-fired EGUs to comply with the fPM standard using PM continuous emission monitoring systems
• Revising startup requirements in MATS

The proposed rule was published on April 23, 2023. See 88 Fed. Reg. 24872.

NACAA’s initial comments note that:

. . . coal- and oil-fired EGUs remain the largest domestic emitter of Hg [mercury] and many other HAP, including many of the non-Hg HAP metals and HCl [hydrogen chloride]. . . As EPA’s proposed measures show, further reduction is necessary and possible.

An additional argument is that:

. . . public health from reducing HAPs, especially mercury, are well-established.

Consequently, the organization states its supports for EPA to make what it describes as “improvements to the existing MATs.” Nevertheless, additional points raised include:

• More Stringent Filterable Particulate Matter Standard (Described as reasonable and achievable.)
• Even More Stringent Filterable Particulate Matter Standard (Should only be considered if strategies are developed that would help some of the hardest-hit areas work through difficulties with the tighter standard.)
• Continuous Emissions Monitors (Concern is expressed about their accuracy and reliability with the current level of technology for demonstrating compliance with the stringent fPM standard.)
• Standards for Lignite-Fired EGUs (Supports proposal to require lignite-fired EGUs to meet the same mercury emission standard being met by non-lignite EGUs.)
• Standards for Non-Lignite-Fired EGUs (Encourages EPA to continue to investigate options for technological advances to further reduce mercury emissions.)
• Amended Definition of “Startup” to Remove Work Practice Standards (Supports the change and agrees that it is achievable with little to no additional expenditure.)
• Compliance Period (One-year time period is deemed sufficient and supports retaining a three-year compliance deadline.)

A copy of the comments can be downloaded here.