Notice of Proposed Rulemaking for Maricopa County Air Quality Department Rule 324 affecting stationary reciprocating IC engines (RICE)

January 6, 2021

The Maricopa County Air Quality Department (MCAQD) is proposing to amend Rule 324 (Stationary Reciprocating Internal Combustion Engines (RICE)).

On January, 2019, the MCAQD submitted a Letter of Commitment for Conditional Approval which was followed with a supplemental commitment letter to address additional rule approvability comments that MCAQD received according to a December 16, 2020 Trinity Consultants report.

Based on the commitment letters, the EPA published a proposed conditional approval of Rule 324 in the Federal Register on December 30, 2019. EPA’s final conditional approval was published on July 20, 2020, and the proposed effective date of this rulemaking is April 7, 2021.

This proposed rulemaking will directly affect facilities in Maricopa County that have stationary reciprocating internal combustion engines with a rated brake horsepower (rated bhp) of:

  • Greater than 125, if the stationary RICE is not located at a major source of NOx emissions,
  • Greater than 50, if the stationary RICE is not located at a major source of NOx emissions and the maximum aggregated rated bhp of all stationary RICE at the stationary source is more than 125 when all engines with a rated bhp of more than 50 are aggregated,
  • Greater than 50, if the stationary RICE is located at a major source of NOx emissions, an
  • Any nonroad engine, with a rated bhp of greater than 125, that is located at a stationary source that emits or has the potential to emit any regulated air pollutant greater than permitting thresholds defined in Rule 100.

Two of the major deficiencies identified by EPA regarding Rule 324 are summarized below:

  • Rule 324 does not outline a RACT limit for NOx and VOC emissions from all applicable IC engines
  • The submitted rule only applied to engines rated greater than 250 bhp, and to engines greater than 50 bhp when operating at a facility whose units sum to greater than 250 bhp.

Two of the major remedies proposed by MCAQD in answer to the deficiencies to Rule 324 are as follows:

  • The MCAQD is proposing to restructure Rule 324 to clarify applicability and emission limits
  • The MCAQD is proposing to lower the applicability threshold to 50 bhp for stationary RICE located at a major source of NOx.

The MCAQD has published this Notice of Proposed Rulemaking/Notice of Expedited Rulemaking on its website. Please see the Proposed Rulemaking Notice for a complete list of deficiencies and remedies as well as detailed red-lined changes to the rule.

What this means to you
Maricopa County Air Quality Department (MCAQD) is proposing to amend Rule 324 (Stationary Reciprocating Internal Combustion Engines (RICE)). This proposed rulemaking will directly affect facilities in Maricopa County that have stationary reciprocating internal combustion engines over a specific range of rated brake horsepower.

MIRATECH can help
CONTACT MIRATECH for stationary engine emission solutions in Arizona.