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EPA’s Newest Target for Clean Air Act Enforcement: Stationary Engines

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The U.S. Environmental Protection Agency (“EPA”) has announced its latest priority for Clean Air Act enforcement: stationary engines. In an enforcement alert, EPA states that it has been finding numerous violations of Clean Air Act requirements by owners and operators of stationary engines. Such engines are used across many industrial sectors, including the energy and mining sectors, to generate electricity, provide primary power, power equipment such as pumps and compressors, and supply emergency power. Failure to comply with applicable Clean Air Act emission limitations; operating limitations; and testing, monitoring, and reporting requirements for stationary engines risks disruptive EPA enforcement requiring payment of substantial penalties. Companies should take steps now to evaluate their compliance with stationary engine regulations in preparation for increased EPA enforcement.

Compliance Concerns

EPA’s concerns regarding noncomplying stationary engines stem from the potential for excess emissions of volatile organic compounds, carbon monoxide, nitrogen oxide, and particulate matter, among other pollutants.

EPA regulations applicable to stationary engines include the National Emission Standards for Hazardous Air Pollutants (“NESHAP”) for Reciprocating Internal Combustion Engines (40 C.F.R. Part 63, Subpart ZZZZ); New Source Performance Standards (“NSPS”) for Stationary Compression Ignition Internal Combustion Engines (40 C.F.R. Part 60, Subpart IIII); and NSPS for Stationary Spark Ignition Internal Combustion Engines (40 C.F.R. Part 60, Subpart JJJJ).

EPA’s alert spotlights the following NESHAP and NSPS violations identified by inspectors in recent investigations:

  1. Failure to retrofit existing engines with necessary pollution controls;
  2. Emergency stationary engines participating in “demand response programs,” thereby voiding the emergency status of the engines; and
  3. Failure to perform required testing following installation of pollution controls.

Recent Enforcement

EPA highlights five recent Clean Air Act settlements involving noncomplying stationary engines. Owners and operators of these engines included an electric utility, the operator of a compressor station, the owner of a sand and gravel plant, and the owner and operator of a metal shredding facility. Beyond civil penalties, these settlements required relief such as retrofitting engines with diesel oxidation catalysts, compliance testing, and additional monitoring and reporting.

Recommended Actions

EPA recommends that owners and operators of stationary engines take steps to:

  1. Review the requirements of potentially applicable NESHAP and NSPS regulations and confirm which apply based on such factors as the age, size, and location of the engine, and the type of fuel used.
  2. Determine the need for an emissions control system.
  3. Determine whether the engine has a Certificate of Conformity from the manufacturer.
  4. Evaluate compliance with emission and operating limitations, as well as recordkeeping and reporting obligations.
  5. Consider replacing older engines with new, cleaner engines or converting to grid power.


EPA’s alert is the latest in a line of enforcement alerts issued against sources that have included storage vessels at oil and natural gas production facilities, natural gas gathering operations, metal recycling facilities, and aftermarket defeat devices. EPA uses these alerts to put owners and operators of specific sources on notice that it is gearing up to increase enforcement. Accordingly, owners and operators of stationary engines should take steps now to confirm their compliance with regulatory requirements. They should also evaluate whether they wish to take advantage of EPA’s Audit Policy, which can offer substantial penalty reduction benefits for self-disclosed violations.

The attorneys at Vinson & Elkins are on the leading edge of helping companies manage and respond to Clean Air Act enforcement risk. We would be delighted to confer with any company that has questions about EPA’s enforcement alert or what to do about it.

This information is provided by Vinson & Elkins LLP for educational and informational purposes only and is not intended, nor should it be construed, as legal advice.