Microsoft Faces Proposed Penalty Over Leesburg Data Center Air Pollution
Virginia environmental regulators have proposed a record $2.5 million civil penalty against Microsoft for exceeding air pollution limits at its Leesburg data center. The violations occurred during a five-day power outage in 2025 when backup generators ran continuously, surpassing permitted emissions and fuel use. The proposed consent order is currently open for public comment.
Virginia's Department of Environmental Quality (DEQ) has proposed a record $2.5 million civil penalty against Microsoft, the largest in the department's history, for significant air pollution violations at its Leesburg data center. The proposed consent order, now open for public comment, stems from a five-day power outage from June 27 to July 1, 2025, which forced the data center at 19515 Compass Creek Parkway to rely on backup diesel generators.
During this period, Microsoft's facility exceeded its annual permit limits for nitrogen oxides, particulate matter, volatile organic compounds, and fuel throughput. DEQ calculated emissions of approximately 102 tons of nitrogen oxides against a 94.67-ton limit, and fuel usage of 1.19 million gallons compared to a 665,850-gallon limit. Microsoft has disputed DEQ's emissions calculations but stated it has invested $31 million in systems to prevent future extended outages and is working with the state towards a resolution, emphasizing its commitment to responsible development.
The incident highlights broader environmental concerns surrounding data centers in Virginia, which hosts a significant portion of U.S. data centers. Northern Virginia alone has over 4,000 diesel generators, and statewide, roughly 9,000 backup generators exist, with nearly half concentrated in Loudoun County. Research indicates these generators contribute to air pollution, with one study equating their public health impact to five large gas-fired power plants even with minimal operation. This context is further complicated by Northern Virginia's ozone non-attainment designation.
In response to growing concerns, lawmakers are expected to consider legislation limiting or banning diesel generators at data centers during the 2026 General Assembly session. Furthermore, starting July 1, 2026, new air permit applications for diesel generators will generally require Tier 4-equivalent emissions controls. The DEQ is also evaluating guidance regarding planned utility outages and emissions compliance.