Washington State’s Department of Ecology (Ecology) has released a draft area-specific general order for data centers. The general order covers data centers that use diesel-fired emergency generators that meet certain key requirements and are located in areas near East Wenatchee, Malaga, or Quincy, WA.

The rapid growth of AI infrastructure and cloud computing industries around the country require the expansion of data centers in the US. The primary source of power for these data centers often comes from the local electrical grid, with emergency back-up power provided by diesel-fired emergency generators on site. While emissions from these emergency generators are relatively low in practice, the potential emissions from the facility result in an air permitting process that can be very complex. Air permitting is frequently a key hurdle to developing a data center, particularly when complex air dispersion modeling is required.

Ecology regulates data centers in the cities included in the draft general order, and air permits for these data centers frequently require extensive air dispersion modeling and health impact assessment for Washington Toxic Air Pollutants (TAPs), including diesel particulate matter.

This draft general order would, when finalized, provide data center companies with a more streamlined air permitting process for developing data centers in Washington. There are numerous requirements included in the draft order, including but not limited to the following:

• All engines must be compliant with the emission limits set forth in EPA’s Tier 4 standards for non-road diesel engines.
  • Note that the engines do not necessarily need to be certified for the Tier 4 standards, so Tier 2 engines with additional emissions controls that meet the Tier 4 engine standards would be covered under the general order.
• All engines must be located at least 591 feet from the nearest secure access facility property line.
• The general order covers up to 21 generators, with a maximum per-engine power of 4,423 bhp.
• Fuel consumption and hour-per-year limits are included in the draft order, with the specific hour limits determined based on the proximity of the facility to nearby residential properties.
• Maintenance and testing operations would be restricted to one engine at a time, and the operations would need to take place between 7:00 am and 7:00 pm.
  • Engine testing must be coordinated with other data centers in the area to minimize overlap of maintenance and testing operations.
• Specific exhaust stack dimension requirements must be met as part of the proposed general order.

Ecology has scheduled a tentative public hearing date of September 23, 2025 at 6:00 pm PT. If you are interested in submitting comments on the draft order, the comments are due by September 28, 2025 and can be submitted by mail or online.

If you have any questions about the draft order and how this may impact your operations, Trinity is here to help. For assistance reviewing the draft order, understanding its impacts to your current and future data center operations in Washington, or preparing comments, please contact Sam Najmolhoda by email or at 253.867.5600.