EPA Proposes Clean Air Act Standards for Reciprocating Internal Combustion Engine Rule

Kelley Drye Client Advisory


EPA has recently proposed Clean Air Act (“CAA”) Section 112 standards for existing stationary reciprocating internal combustion engines (“RICE”) located at area sources of hazardous air pollutants (“HAP”).1 Any facility with either emergency or non-emergency generators should be aware of the implications of this wide-reaching proposal, which may require retrofits of existing generators.

RICE Source Categories

EPA has divided the RICE source category into numerous subcategories and has proposed separate standards for each of the following relevant subcategories:

  • Stationary RICE less than 50 HP
  • Compression Ignition (Diesel) greater than or equal to 50 HP
    • Emergency
    • Non-Emergency
  • Spark Ignition RICE greater than or equal to 50 HP
    • Emergency
    • Non-Emergency
      • 2-stroke lean burn (2SLB) < 250 HP
      • 2SLB ≥ 250 HP
      • 4-stroke lean burn (4SLB) < 250 HP
      • 4SLB ≥ 250 HP
      • 4-stroke rich burn (4SRB)

Non-emergency engines above 250 HP (300 HP for diesel engines, 50 HP for 4SRB ) would be subject to stringent beyond the floor” Maximum Achievable Control Technology (“MACT”) numeric emissions limitations requiring add-on controls such as oxidation catalysts or non selective catalytic reduction (“NSCR”). For emergency engines used more sparingly (less than 100 hours per year), less stringent numeric limits based upon MACT alone apply for engines rated above 500 HP. The MACT standards would regulate either formaldehyde or carbon monoxide as a surrogate for all HAP. Sources below those thresholds would be subject to management practices that include maintenance and inspection requirements.

Compliance Requirements

An initial performance test would be required for all engines subject to numeric emission limitations. Owners and operators of existing non-emergency stationary RICE subject to numerical limitations, with the exception of stationary RICE less than 100 HP, must also comply with the NESHAP General Provisions and submit an initial notification, notification of performance test, and a notification of compliance for each affected stationary RICE.

Owners and operators of non-emergency engines greater than 500 HP would be required to perform a subsequent performance test every three years or 8,760 hours of operation. Engines greater than 500 HP must also operate within specified temperature and pressure ranges and must continuously monitor and record catalyst inlet temperatures. Owners and operators of units subject to management practices must develop a maintenance plan and maintain records demonstrating compliance with the plan.

Owners and operators of emergency engines would be required to maintain records of operation and install a non-resettable hour meter on the engine.

In addition, the rule would require non-emergency diesel engines above 300 HP and with a displacement of less than 30 liters per cylinder to operate on ultra-low sulfur diesel fuel with a 15ppm sulfur content, which is the current fuel requirement for highway diesel vehicles.

Startup, Shutdown, Malfunction (“SSM”)

Pursuant to the recent D.C. Circuit opinion invalidating the SSM exemption, EPA has proposed several options for regulating emissions during SSM events. First, a single emissions limit could apply at all times regardless of SSM events. Under this option, numerical emissions standards could be higher to account for variation in operation. A second option would be to have a second less stringent numerical standard for engines relying on catalytic controls that would apply during startup (when a catalyst is not warm enough to operate effectively) or during malfunction. However, under this option the primary standard would continue to apply during shutdown as EPA does not believe that catalyst operation would be diminished during shutdown.


EPA requests comment on many aspects of the RICE proposal, including the appropriateness of the proposed regulatory thresholds and management practices. Comments on the RICE proposal are due by June 3, 2008.

Kelley Drye & Warren LLP

Kelley Drye’s Environmental Law Practice Group specializes in providing comprehensive solutions to complex problems. We provide both advice and representation for clients participating in rule-making and policy-making activities by federal regulatory agencies, including the U.S. Environmental Protection Agency and the Occupational Safety & Health Administration, and similar state agencies.

For more information about this Client Advisory, please contact:

John L. Wittenborn
(202) 342-8514

Joseph J. Green
(202) 342-8849


1See National Emission Standards for Hazardous Air Pollutants for Reciprocating Internal Combustion Engines, Proposed Rule, 74 Fed. Reg. 9,698 (March 5, 2009). EPA has also proposed new regulations for existing RICE less than 500 HP at major sources and updated regulations existing RICE larger than 500 HP. However, this alert focuses on existing RICE at area sources because these have not previously been regulated by EPA.