DEQ Proposes to Allow more Frequent Operation of Backup Generators

A bad idea is once more being considered. The Virginia Department of Environmental Quality (DEQ) proposes to allow backup diesel generators to operate more often, particularly at data centers in Northern Virginia. This would lead to significant increases in air pollution, noise, and environmental impacts in the region, especially to residential communities and schools.

There are 4,000 MW of backup generation (primarily diesel) in the Potomac River Basin is concentrated in Northern Virginia, with an estimated 9,000 permitted diesel generators across the state, many of which serve data centers in Loudoun and Prince William counties (Source 1,2,8).

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Air and Health Impacts

The core issue is that these generators are generally Tier II or unrated diesel engines (designed only for emergency use) and are a highly polluting energy source (Source 1.2, 3.3). Increased operation would directly increase the emission of harmful air pollutants, posing a significant public health burden.

• Particulate Matter (PM): Diesel generators emit diesel particulate matter (DPM), a known carcinogen (Source 1.1). Increased use would raise the concentration of PM2.5 (fine particulate matter), which can penetrate deeply into the lungs and bloodstream, exacerbating asthma, bronchitis, and other respiratory and cardiovascular diseases (Source 1.8).
• Ozone Precursors (NOx): The generators emit large amounts of nitrogen oxides, which react with volatile organic compounds (VOCs) to form ground-level ozone (smog) (Source 3.3). Allowing generators to run during anticipated disruptions often coincides with peak summer heat and grid stress, which are already the highest ozone-forming conditions (Source 1.2).
• Cumulative Health Costs: The Joint Legislative Audit and Review Commission (JLARC) and related studies estimate that even a fraction of the permitted emissions could result in an annual public health cost of $190–260 million in Virginia and surrounding states (Source 1,8).

Impact on Schools and Residential Areas:

Children are especially vulnerable to air quality impacts. Proximity of generator clusters to sensitive receptors—such as schools, hospitals, and residential areas—is a key concern, as increased operation would directly expose these communities to higher levels of toxic emissions (Source 1,2).

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Noise Impacts

The allowance for more frequent operation, especially for non-emergency reasons like planned maintenance or grid support, would lead to chronic noise pollution in adjacent communities.

• Disruptive Decibel Levels: Diesel generators are extremely loud. When multiple units run simultaneously, they produce a constant, industrial-grade humming and droning noise (Source 3,2).
• Quality of Life: Residents near data centers already report that the noise from cooling equipment and routine testing disrupts sleep, conversation, and the ability to use outdoor spaces (Source 3,2). Extending the permitted operating time beyond brief emergency tests would make this noise pollution a pervasive, ongoing issue.
• Increased Frequency: The proposal is designed to allow use during "planned outage events" or grid constraints (Source 1,2). This shifts the use from unpredictable, rare emergencies to foreseeable, planned operations, increasing the overall frequency and duration of loud generator operation (Source 3,2).

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Environmental and Regulatory Impacts

• Climate Change (GHG): Increased burning of diesel fuel for non-emergency grid support directly increases greenhouse gas emissions, making it more difficult for Virginia to meet its climate goals, such as the Virginia Clean Economy Act (VCEA) targets (Source 1,1).
• Cumulative Emissions: The total number of permitted generators is enormous (nearly 9,000 across the state, with thousands concentrated in Northern Virginia) (Source 1.8). The concern is that DEQ has not publicly estimated the potential cumulative impact of thousands of these generators operating together for extended periods, effectively using them as a temporary, polluting power plant (Source 1,2).
• Regulatory Precedent: Environmental groups oppose the change, fearing it sets a "slippery slope" precedent that allows generators, which are permitted only for emergency use, to be used for demand response—where data centers are paid to reduce grid usage by running their polluting backup power (Source 1,2).

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Sources

1. PEC Web Map, "Data Centers, Diesel Generators and Air Quality"
2. PEC Virginia, "Proposed Increase to Data Center Diesel Generator Use"
3. Bay Journal, "Virginia regulators consider letting data centers regularly use fossil-fuel power for part of the year"
4. Trinity Consultants, "Virginia Department of Environmental Quality Releases Three Air Permitting Guidance Documents for Data Centers"
5. Virginia Conservation Network, "ADDRESSING DATA CENTER IMPACTS & ENSURING TRANSPARENCY"
6. JLARC, "Data Centers in Virginia"
7. McGuireWoods, "Virginia DEQ Withdraws Proposed Rule Allowing Extended Backup Generator Use"
8. Virginia Regulatory Town Hall, View Comments on Proposed Rule