Off-Road Diesel Engines (SOON Program)


The application period for the 2023 Carl Moyer Program (Program Announcement PA2023-04) closed on May 9, 2023 at 11:59 PM.

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What is the SOON Program?

Title 13, Section 2449 of the California Code of Regulation (CCR), "Regulation for In-Use Off-Road Diesel-Fueled Fleets (Off-Road Regulation) Link to external website." was adopted by the California Air Resources Board (CARB) in July 2007 and requires off-road diesel vehicle fleets to achieve NOx and PM2.5 reductions by meeting NOx and PM fleet average standards.

A provision of the Off-Road Regulation (Title 13, CCR, Section 2449.2) allows air districts to opt-in and require the largest fleets to apply for funds to meet more stringent NOx targets.  As a result, the South Coast Air Quality Management District’s Surplus Off-Road Opt-In for NOx (SOON) Program was developed in 2008.  The SOON Program is designed to achieve additional NOx reductions above those that would be obtained from the State In-Use Off-Road Vehicle Regulation. These reductions are critical to meeting the PM2.5 and ozone ambient air quality standards in the South Coast Air Basin.

The SOON Program provides funding assistance to large fleets for the purchase of commercially-available low-emission heavy-duty engines to achieve near-term reduction of NOx emissions from in-use off-road diesel vehicles.  Fleets that participate in the SOON Program can apply for funding for NOx exhaust retrofits, repowers or equipment replacements.

What's New

Funding is from state SB 1107 and AB 923 funds. Project awards are contingent upon receiving these funds from CARB. Additional sources of funding may become available and added to the SOON Program.

Eligible projects must meet a maximum cost-effectiveness limit of $34,000 per ton of emissions reduced and any additional South Coast AQMD criteria as stated in the PA (the cost-effectiveness limit may be changed depending on the demand for program funds). For advanced technology projects that are zero-emission, or alternatively meet the cleanest certified optional standard applicable, South Coast AQMD may apply a cost-effectiveness limit of up to $522,000 per weighted ton, for the incremental emission reductions that go beyond current emission standards. Projects exceeding the cost-effectiveness limit may receive partial funding up to the cost effectiveness limit. Except where otherwise stated, projects must meet the requirements of the CMP program guidelines.

Applications submitted in response to this PA will be evaluated according to the approved 2017 CMP Guidelines.

Who is Eligible for Funding?

  • All large fleets with a total statewide equipment horsepower over 20,000 hp must apply for funding.
  • Fleets below 20,000 hp may voluntarily participate in this program.

How Do I Apply for SOON Funding?

NEW!  South Coast AQMD will no longer accept paper applications for funding consideration and only online application submissions will be accepted.  To apply online using the Carl Moyer Online Application System, please visit or click here to get started.

SOON Program Compliance Plan

Projects funded by SOON monies must result in emission reductions that are surplus to those that would be realized by fleets complying with the base rule. Fleets are required to submit a compliance plan in electronic format to demonstrate how they comply with both the base rule as well as the SOON provision of the rule. Fleet owners, at a minimum, must provide the following information for each year, 2010 through 2023 inclusive:

  • A vehicle list which includes, but is not limited to, vehicle type, manufacturer, model, model year, and whether the equipment is included in the base or SOON fleet for each piece of equipment in the fleet.
  • Information including, but not limited to, calculations, fleet information, etc., showing compliance with the base rule fleet target levels or compliance with the BACT turnover and retrofit requirements. Either the CARB calculator (individual tabs for each future year available at or the Excel SOON fleet calculator spreadsheet below may be used.
  • Information including, but not limited to, calculations, fleet information, etc., showing whether the vehicles funded by the SOON program are in compliance with the SOON NOx fleet average target levels.

For your convenience, you may view and download SOON Compliance Plan documents listed below:

Useful Links and Resources:

For additional questions on the SOON Program, please contact Alyssa Yan at (909) 396-2024 ( or Darren Ha at (909) 396-2548 (

To sign-up for vehicle funding program updates, please click here.

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