The Colossus data center operated by xAI outside of Memphis is now at the center of a legal and environmental dispute over natural gas turbines used to power the site.
The Southern Environmental Law Center (SELC), acting on behalf of the NAACP, submitted a letter to xAI that serves as a notice of intent to sue for alleged violations of the Clean Air Act. The issue is whether xAI installed and operated a large fleet of combustion turbines and other air pollution sources without first obtaining the permits required before construction and operation.
What the notice alleges
SELC says xAI installed and operated at least 35 combustion turbines and other sources of air pollution at the Colossus site over the past year without obtaining the necessary preconstruction or operating air permits.
The letter is not just a complaint. Under the Clean Air Act, organizations must send this kind of notice 60 days before filing a lawsuit. That makes the document a formal step toward litigation, not simply a public statement.
The legal group also alleges that xAI failed to obtain permits required by both federal and local regulators before installing the generators. It further claims the company was not operating them with proper air pollution controls.
At one point, according to SELC, xAI had enough turbines at the site to generate 421 megawatts of electricity. The turbines have the potential to emit more than 2,000 tons of NOx per year, a group of chemicals that contribute to smog.
Why Memphis air quality is part of the dispute
The legal arguments are tied closely to local air conditions. SELC notes that Memphis already “had some of the worst air quality in the region.” The group also points to asthma as a central concern for residents near the site and across the city.
In 2024, Memphis was deemed an asthma capital of the nation by the Asthma and Allergy Foundation of America due to high rates of emergency room visits and deaths from asthma. That fact gives the dispute a broader public health context, because the turbines are alleged sources of air pollution in an area SELC describes as already burdened.
The potential emissions figure matters because the turbines are not being discussed as small auxiliary machines. SELC describes a large collection of combustion turbines placed around a major data center, with generation capacity measured in hundreds of megawatts.
The core concern is straightforward: if equipment can emit pollutants at that scale, regulators and affected communities need clarity on what is operating, what permits apply, and what pollution controls are in place.
How the turbines were documented
The Shelby County Health Department (SCHD), which oversees local air pollution compliance, had previously told reporters that xAI’s turbines were exempt from permitting. SELC says SCHD had not publicly disclosed what xAI was operating on the site or the legal basis for that exemption.
To understand what was happening at Colossus, SELC paid an aerial photographer to capture images of the facility in March. Those photos showed 35 turbines installed around the perimeter of the data center at that time.
Thermal images taken about a month later showed that at least 33 of them were operational, according to SELC. Those images became an important part of the group’s argument because they moved the dispute from general concern to specific equipment counts and operating evidence.
After those images were taken, the Greater Memphis Chamber, a local economic development agency, said xAI had removed some of the turbines. The organization said the temporary natural gas turbines used to power the Phase I GPUs before grid connection were being demobilized and would be removed from the site over the next two months.
The Memphis Chamber also said about half of the operating turbines would remain until a second substation completed the data center’s connection to the grid. Once that substation was complete, the organization said, the turbines would serve as backups.
What remained on site
SELC says a flight on June 15 showed that at least 26 turbines remained at the Colossus site. That count included three new turbines installed since the April flight.
The total generating capacity was around 407 megawatts, according to SELC. That was just 14 megawatts below the earlier amount described in the source article.
For SELC, the remaining capacity undercuts the idea that the turbine issue had largely disappeared. Even after some equipment was reportedly removed, the group says the site still had a substantial number of turbines and nearly the same overall generating capacity.
The legal theory depends on permitting obligations. SELC states that new sources of criteria and other air pollutants in Tennessee must obtain preconstruction approval in the form of an air permit, as well as a permit to operate and emit pollutants, with very few exceptions.
What the case is really about
The dispute is about more than whether xAI used temporary power while waiting for a grid connection. It is about whether a fast-moving data center buildout can rely on large natural gas turbines without first clearing the air permitting process that SELC says applies.
The facts in the notice point to several unresolved questions:
- Whether xAI obtained the required preconstruction and operating air permits.
- Whether any permitting exemption applied to the turbines at Colossus.
- Whether the turbines were operated with proper air pollution controls.
- How many turbines remained on site after some were reportedly removed.
- Whether the remaining turbines were temporary power sources, backup sources, or something else under applicable permitting rules.
The notice gives xAI advance warning before a potential lawsuit. It also places the Colossus data center, its power strategy, and its air pollution footprint under closer public scrutiny.
For Memphis residents, the dispute now centers on transparency and enforcement. For xAI, the immediate issue is whether its turbine operations can withstand a Clean Air Act challenge from SELC and the NAACP.