Department of Environmental Quality revises air pollution exception for data centers

After opposition during a public hearing and comment period, Virginia regulators are scaling back a proposal to allow data centers in Northern Virginia counties to run diesel generators over a three-month period to alleviate potential electric grid strains.

Initially, the Department of Environmental Quality proposed the temporary lifting of air emission limits, a change known as a variance, for data centers in the counties of Loudoun, Prince William, and Fairfax. But on Monday, DEQ restricted the variance to facilities in Loudoun.

[Read more: Va. regulators propose easing emission limits for data centers over power transmission concerns]

“DEQ takes the public participation process very seriously and is making appropriate revisions to the proposal based on that input,” said DEQ Director Michael Rolband in a statement on the revised variance.

In January, DEQ proposed the short-term change after PJM Interconnection, which operates the regional electric grid, had flagged in its five-year forecast rising electricity demand in Dominion territory due to data center development.

The variance would exempt from short-term air emission limits for those data centers located in areas for which PJM issues a warning that there are acute strains on the transmission system. Those facilities would then be allowed to run their backup generators. The variance would be in effect until July 31.

At a public hearing in Woodbridge on Feb. 27, dozens of residents and groups opposed the temporary change, saying it could have negative health, environmental, and noise impacts.

At the same hearing, Josh Levi, president of the industry group the Data Center Coalition, requested that DEQ narrow the variance to Loudoun.

[Read more: Temporary air pollution exception for data centers sparks opposition in Northern Virginia]

“We recognize that DEQ proposed the variance extend to the counties of Prince William and Fairfax out of an abundance of caution,” Levi stated. “However, given Dominion’s assurance that the impact of the transmission constraint is limited to Eastern Loudoun County, we believe there is an opportunity to be more precise in addressing potential risks.”

The region of Loudoun County, known as Data Center Alley, is home to the world’s largest concentration of data centers. Almost 300 data centers in Northern Virginia support about 70% of the world’s internet traffic.

The revised notice also includes DEQ estimates of how the variance could impact emissions from the approximately 4,151 diesel generators located at data centers in Loudoun County.

A single generator at a Loudoun data center, on average, emits every hour almost 45 pounds of nitrous oxides and non-methane hydrocarbons, 24 pounds of carbon monoxide, and 3 pounds of particulate matter. Particulate matter is tiny particles that, if ingested, can lead to heart and respiratory issues.

A Department of Environmental Quality chart on the estimated emissions from a single generator at a data center in Loudoun County. (Courtesy of DEQ)

DEQ said it does “not anticipate that any data center will need to use this variance.”

“History indicates that those PJM events” that would trigger the variance “are rare, averaging approximately 24 hours per year over the past five years,” the agency wrote.

Along with the Data Center Coalition, a number of commenters also supported the variance, saying it will help facilities maintain the reliability of the internet.

The comment period on the variance has been extended through April 21. Another public hearing will be held on April 6.