In June 2024, the Utah Division of Air Quality (UDAQ) released a new version of the UDAQ Emissions Impact Assessment Guidelines. This release formally documents the increased modeling authority that UDAQ has established in recent years. Exceedances of the National Ambient Air Quality Standards (NAAQS) allow UDAQ to use modeling to require more stringent control technologies than even Best Available Control Technology (BACT) analyses in some cases.
The updated UDAQ Emissions Assessment Guidelines state that UDAQ can perform “in-house” modeling at their discretion. The guidance states, “If in-house modeling shows a problem meeting the NAAQS, the model inputs will be adjusted in an attempt to show compliance, and the results will be provided to the applicant for further refinement as necessary to demonstrate compliance with the NAAQS.” However, the “model inputs” adjusted during UDAQ’s in-house modeling will not necessarily consider the operating constraints of your facility. For example, equipment operating times may be restricted, stack heights increased, or specific control technologies mandated, potentially rendering your project more complex and elongating timelines.
Emergency generators and data centers are specifically identified as sources likely to require modeling. Previously, the unspoken threshold for emergency generators was 10 tons per year of nitrogen oxides (NOX). The new guidance lowers this threshold to 2 tons per year of NOX – a level that larger engines can usually only achieve with add-on control technologies.
This increased exercise of authority is a response to ongoing nonattainment issues in Utah. Modeling is anticipated to have a growing impact on permitting and control requirements, particularly in areas with worsening ozone nonattainment like Salt Lake County, which is expected to be redesignated as serious nonattainment next year.
Modeling continues to drive regulation development and permitting in Utah and across the United States. The changes to UDAQ’s guidance indicate that an increasing number of sources and applications will require modeling. Trinity Consultants has decades of experience in modeling and is ready to assist you with your next project.
If you would like to discuss modeling in Utah and how it may impact your facility, please contact Trinity’s Salt Lake City office.
