TITLE 9. ENVIRONMENT
TITLE 9. ENVIRONMENT
STATE AIR POLLUTION CONTROL BOARD
Final Regulation
REGISTRAR'S NOTICE: The State Air Pollution Control Board is claiming an exemption from Article 2 of the Administrative Process Act in accordance with § 2.2-4006 A 4 a of the Code of Virginia, which excludes regulations that are necessary to conform to changes in Virginia statutory law or the appropriation act where no agency discretion is involved. The board will receive, consider, and respond to petitions by any interested person at any time with respect to reconsideration or revision.
Title of Regulation: 9VAC5-50. New and Modified Stationary Sources (adding 9VAC5-50-610, 9VAC5-50-620, 9VAC5-50-630).
Statutory Authority: § 10.1-1308 of the Code of Virginia; §§ 110, 111, 123, 129, 171, 172, and 182 of the Clean Air Act; 40 CFR Parts 51 and 60.
Effective Date: November 4, 2026.
Agency Contact: Julia Wack, Regulatory Analyst, Department of Environmental Quality, 1111 East Main Street, Suite 1400, Richmond, VA 23219, telephone (804) 432-3581, or email julia.n.wack@deq.virginia.gov.
Summary:
Pursuant to Chapter 397 of the 2026 Acts of Assembly, the amendments add a new Article 7 to New and Modified Stationary Sources (9VAC5-50). The sections within Article 7 set emission limits for certain engine-generator sets at data center facilities that submit a permit application on or after July 1, 2026.
Article 7
Emission Standards for Data Center Engine Generator-Sets (Rule 5-7)
9VAC5-50-610. Applicability and designation of affected facility.
A. The affected facility to which the provisions of this article apply is each data center that applies for a permit on or after July 1, 2026.
B. The provisions of this article apply throughout the Commonwealth of Virginia.
9VAC5-50-620. Definitions.
A. For the purpose of applying this article in the context of the Regulations for the Control and Abatement of Air Pollution and related uses, the words or terms in subsection C of this section shall have the meanings provided in subsection C of this section.
B. Unless otherwise required by context, all terms not defined in this section shall have the meanings provided in Permits for Stationary Sources (9VAC5-80), General Definitions (9VAC5-10), or commonly ascribed to them by recognized authorities, in that order of priority.
C. The words or terms, when used in the Regulations for the Control and Abatement of Air Pollution and related uses shall have the following meanings.
"Data center" means the same as that term is defined in § 58.1-3506 A 43 of the Code of Virginia.
"Diesel oxidation catalyst" means a flow-through exhaust device that contains a honeycomb structure covered with a layer of chemical catalyst containing small amounts of precious metal such as platinum or palladium that interact with and oxidize pollutants, including carbon monoxide and unburned hydrocarbons, in the exhaust stream, thereby reducing carbon monoxide emissions.
"Diesel particulate filter" means an emission control technology that reduces particulate matter emissions by trapping the particles in a flow filter substrate and periodically removes the collected particles by either physical action or by oxidizing or burning off the particles in a process called regeneration.
"Engine-generator set" or "gen-set" means the combination of an electrical generator and an engine mounted together to form a single piece of equipment.
"Selective catalytic reduction" means a control device that reduces the exhaust gas concentration of nitrogen oxides by injecting an ammonia solution or urea into the exhaust gas stream, which in the presence of a catalyst reacts with the nitrogen oxides to form nitrogen gas and water vapor.
"Tier 4 equivalent" means a gen-set with a selective catalytic reduction system or equivalent for nitrogen oxides control, a diesel oxidation catalyst system or equivalent for carbon monoxide control, and a diesel particulate filter or equivalent for particulate matter control.
9VAC5-50-630. Standard for engine-generator set emissions.
A. For a data center permit issued by the department, including coverage under any general permit, the department shall not issue such permit unless the emission limit for each gen-set established by such permit is equal to or less than the emissions achieved by a Tier 4 equivalent gen-set.
B. Nothing in this section shall be construed to prevent the department from (i) determining the Best Available Control Technology, Lowest Achievable Emission Rate, Reasonably Available Control Technology, any New Source Performance Standard, or any National Emission Standards for Hazardous Air Pollutants or (ii) establishing in a permit issued by the department pursuant to this chapter more stringent emission limits than those achieved by a Tier 4 equivalent gen-set.
VA.R. Doc. No. R27-8720; Filed September 02, 2026