Research note (plain English) - May 1, 2026
For any Texas land parcel, what air-pollution permits does an onsite data-center power plant need?
There is no single answer. Building an onsite gas-turbine power plant in Texas pulls in roughly a dozen state and federal rules at once: how clean the local air already is, what equipment is being installed, how much pollution it could emit at full output, which Texas pre-build permit track applies, whether the public has to be formally notified, whether atmospheric dispersion modeling is required, and which of the federal Clean Air Act's equipment-specific rulebooks each piece of gear lives under. This page walks that decision tree in plain English and runs it against two real Texas data-center builds whose filings are already on the public record.
- State agency
- Texas (TCEQ)
- Federal layer
- EPA Clean Air Act
- Worked demos
- Longhorn + Goodnight
Glossary
The terms used on this page
Quick reference for the Texas and federal air-permit acronyms that appear in the decision graph, the route table, and the worked demos below.
- TCEQ
- Texas Commission on Environmental Quality, the state agency that reviews and issues air permits in Texas.
- NSR (New Source Review)
- The federal Clean Air Act's pre-construction permit program. Texas runs its own version through TCEQ. There are several tracks ranging from fast (Permit by Rule) to slow (PSD).
- PBR (Permit by Rule)
- Fast Texas pre-construction track for equipment that fits a pre-approved template, usually no public notice. Common for emergency diesel generators.
- Standard Permit
- Templated Texas permit for specific equipment classes (including a dedicated one for electric generating units). Faster than case-by-case NSR but stricter than PBR.
- Case-by-case NSR
- Texas pre-construction permit written specifically for one project when no template fits. Usually requires public notice and an emissions impact analysis.
- PSD (Prevention of Significant Deterioration)
- The slower, federally-mandated permit for major new sources of air pollution in clean-air areas. Adds public comment, atmospheric modeling, and a 12-24 month review surface.
- Nonattainment NSR (NNSR)
- The PSD equivalent for areas already failing federal air-quality standards (Houston, DFW, Beaumont). Stricter than PSD; requires emission offsets.
- Title V / Part 70
- Federal operating permit issued to major air-pollution sources. Once a site has one, every future expansion is measured against the stricter PSD thresholds.
- NSPS KKKK / KKKKa
- EPA emission standards for stationary combustion gas turbines. KKKKa is the 2024 update; turbines ordered after December 13, 2024 fall under it.
- NSPS IIII
- EPA emission standards for new stationary diesel (compression-ignition) engines, including the emergency backup generators on a typical data-center campus.
- MACT ZZZZ (RICE NESHAP)
- EPA hazardous-air-pollutant standards for stationary reciprocating internal combustion engines. Often satisfied automatically when new diesel emergency engines comply with NSPS IIII.
- BACT (Best Available Control Technology)
- The pollution-control test required in PSD permits. The applicant must justify that the controls chosen are the best available given cost and feasibility.
- PTE (Potential to Emit)
- The maximum amount of pollution a facility could legally emit at full allowed operating hours. Permits evaluate PTE, not actual emissions.
- BTM (behind-the-meter)
- Onsite power generation that does not flow through the public grid; used here for data centers that build their own power plant on the same parcel.
- GHG PSD / Part 98
- The greenhouse-gas branch of PSD permitting and the EPA greenhouse-gas reporting rule. Triggered when CO2-equivalent emissions cross 75,000 - 100,000 metric tons per year.
- RMP / Part 68
- Risk Management Plan rules for facilities that store regulated chemicals over threshold quantities. Often triggered by anhydrous ammonia tanks used in turbine NOx scrubbing.
Decision graph
The permit answer is set before anyone runs an emissions number
Counties around Dallas-Fort Worth, Houston, and Beaumont are "nonattainment" areas (the local air already exceeds federal standards for some pollutant), so the same equipment built there gets a stricter permit track than identical equipment built in a clean-air rural county like Armstrong. Federal turbine standards also have a cutoff date: a turbine ordered after December 13, 2024 falls under a newer, tighter EPA rule (NSPS KKKKa) than one already covered under the older version (KKKK). Location and order date drive the answer before a single emissions calculation is run.
Locate the parcel
County, coordinates, local air program, attainment status, nearby receptors, Class I distance, alternative-language and PIP screen.
Attainment branch, notice branch, modeling inputs
Normalize the stack
Every turbine, engine, tank, SCR ammonia system, refrigerant source, fuel, control, hour cap, startup/shutdown event, and owner/operator grouping.
Facility inventory and common-control boundary
Calculate PTE
Hourly and annual criteria pollutant, HAP, GHG, ammonia, sulfuric-acid mist, fugitive, tank, and MSS emissions with enforceable limits separated from assumptions.
PBR, standard-permit, minor NSR, PSD/NNSR, Title V thresholds
Select Texas NSR route
De minimis, PBR, standard permit, case-by-case minor NSR, PSD, nonattainment NSR, or GHG PSD.
Forms, fees, public notice, modeling, BACT or LAER package
Overlay federal rules
Title V, NSPS for turbines or engines, RICE MACT, GHG reporting, RMP for ammonia, and equipment-specific non-applicability statements.
Operating-permit forms and compliance matrix
Decision tree
Pick the Texas NSR route by walking the gates in order
Each gate is a yes/no test against the calculated potential-to-emit. The first “yes” lands the project at a Texas NSR route. Title V is a federal overlay independent of the route below.
- Gate 1 of 5
Are all sources below TCEQ de minimis limits?
Cumulative facility-wide PTE (criteria + HAP + GHG) under the de minimis screening cutoffs.
Yes lands hereDe minimis · no NSR filing
Internal records · usually no public notice · no modeling
NoProject exceeds de minimis → - Gate 2 of 5
Does every unit fit a 30 TAC Ch. 106 PBR?
Each unit (turbines, RICE, tanks, SCR ammonia, fugitives) inside its category-specific PBR limits.
Yes lands herePermit by Rule (PBR)
PI-7 / PI-7-CERT · Core Data · usually no public notice
NoProject outside PBR limits → - Gate 3 of 5
Does a TCEQ standard permit cover the equipment?
EGU Standard Permit, oil & gas standard permits, etc. — and project not classified as major NSR.
Yes lands hereStandard permit
PI-1S · permit-specific checklist · PIP if notice attaches
NoNo standard permit fits, and project below major NSR → - Gate 4 of 5
Above PBR / standard-permit, but below major NSR?
Above de minimis / PBR / standard-permit thresholds, below PSD significance and below NNSR major-mod.
Yes lands hereCase-by-case minor NSR
PI-1 · BACT · NORI / NAPD · minor-NSR modeling or tox review
NoProject crosses a major-NSR significance threshold → - Gate 5 of 5
Major source or major modification on at least one pollutant?
PSD significance for criteria pollutants, GHG significance, NNSR offset triggers — by attainment status.
Terminal routePSD / NNSR / GHG PSD
PI-1 + major-NSR tables · BACT or LAER · public comment · AERMOD modeling · 12–24 month review
Federal overlay (any route above)
Title V Federal Operating Permit applies whenever the site is a major source — 100 tpy of any criteria pollutant, 10/25 tpy HAP, lower in nonattainment, or any listed Part 70 hook. NSPS KKKK / KKKKa, NSPS IIII, NESHAP ZZZZ, Part 98 GHG reporting, and Part 68 RMP all attach equipment-by-equipment regardless of which Texas route the project lands at.
Texas state layer
Texas separates the build permit from the operating permit
TCEQ (the Texas Commission on Environmental Quality, the state air regulator) issues two distinct kinds of permits. The first is a pre-construction authorization that says "you may build this equipment"; the second is an operating permit that consolidates every ongoing compliance obligation once the site is running. A single data-center campus often needs several pre-construction permits at once, one for the emergency diesel generators (under a fast-track called Permit by Rule), one for the gas turbines (either a templated Standard Permit or a slower case-by-case New Source Review), public notice if the chosen track requires it, and then a separate federal Title V operating permit later when the site crosses major-source thresholds.
| Texas route | Trigger | Forms | Notice | Modeling |
|---|---|---|---|---|
| De minimis / no NSR filing | Only if every source stays below TCEQ de minimis eligibility. | Internal record, or TCEQ de minimis form if a written filing is made. | No public notice in the normal case. | Usually none; keep enough calculations to defend the screen. |
| Permit by Rule | Fits 30 TAC Chapter 106 general limits plus each unit-specific PBR, such as emergency engines or tanks. | PI-7 or PI-7-CERT, Core Data, APD-CERT if certifying limits. | Usually no public notice for data-center emergency-generator PBRs. | Usually none, unless the project needs a health or impacts screen. |
| Standard permit | A standard permit fits the equipment class and does not authorize a major NSR project. | PI-1S, Core Data, fee, emission calculations, permit-specific checklist. | Depends on the standard permit; public-notice PIP may attach if notice is required. | Permit-specific. The EGU standard permit requires written approval first. |
| Case-by-case NSR | The project emits above de minimis/PBR/standard-permit coverage but below major NSR, or no standard route fits. | PI-1 general application, tables, BACT, process description, plot plan, emission calculations. | NORI and possibly NAPD; PIP Form 20960 if the application requires notice. | Minor NSR modeling or toxicology review when TCEQ requires impacts analysis. |
| PSD / GHG PSD / NNSR | Major source or major modification thresholds by pollutant, attainment status, and GHG significance. | PI-1 plus major NSR summary tables, BACT or LAER, offsets if NNSR, GHG PSD analysis. | Public notice, comment, possible contested-case path for non-GHG portions. | Protocol, AERMOD package, NAAQS and PSD increment demonstration. |
| Title V / Federal Operating Permit | Major source status, Acid Rain/CSAPR category, or another Part 70 applicability hook. | OP-1, OP-CRO1, OP-REQ1/2/3, OP-UA, OP-MON, OP-ACPS, OP-PBRSUP as needed. | Title V public announcement/comment for applicable projects. | No new construction authorization; incorporates NSR and federal requirements. |
Federal layer
On top of Texas, the EPA rules are equipment-by-equipment
Each piece of equipment lands in a specific federal rulebook based on what it is. Diesel backup generators fall under NSPS IIII (new emission limits for diesel engines) and MACT ZZZZ (also called RICE NESHAP, hazardous-air-pollutant limits for engines). Gas-fired turbines fall under NSPS KKKK or its newer 2024 sibling KKKKa. The federal Title V operating permit covers the whole site at once. SCR ammonia tanks (used to scrub NOx out of turbine exhaust), greenhouse gas reporting, and nonattainment-area status each add their own checklist before a permit packet is complete.
40 CFR Part 70
Trigger
100 tpy regulated pollutant, HAP 10/25 tpy, lower nonattainment thresholds, or listed program hooks.
Output
Initial SOP/GOP, revisions, renewals, annual certifications, deviation reports.
NSPS Subpart KKKK / KKKKa
Trigger
Stationary combustion turbines. KKKKa checks construction, modification, or reconstruction after Dec. 13, 2024.
Output
NOx/SO2 standards, CEMS or parameter monitoring, performance testing, fuel records.
NSPS Subpart IIII
Trigger
Stationary compression-ignition engines, including diesel backup and firewater engines.
Output
Certified engines, ULSD, non-resettable hour meters, records and reports.
NESHAP Subpart ZZZZ
Trigger
Stationary RICE at major or area HAP sources.
Output
Operating limits and MACT records, often satisfied through NSPS IIII for new emergency CI engines.
40 CFR Part 98
Trigger
Stationary fuel combustion GHG reporting when heat-input and 25,000 metric ton CO2e tests are met.
Output
Annual EPA GHG report, calculation method, monitoring plan, records.
40 CFR Part 68
Trigger
Regulated substances over threshold quantities, often anhydrous ammonia for SCR systems.
Output
Risk Management Plan screen, hazard assessment, prevention and emergency-response duties.
Cliff read
The product is not a checklist. It is a cited map from regulation to the actual filing.
A useful answer has to name the actual paperwork that goes in the envelope: PI-7 (the Permit-by-Rule registration), PI-1S (the Standard Permit application), PI-1 (the case-by-case NSR application) and its emission tables, the operating-permit OP forms, the Public Involvement Plan if the application class requires public outreach, the dispersion-modeling protocol, the BACT analysis (Best Available Control Technology, the test that justifies the chosen pollution controls), an emissions inventory, greenhouse-gas reporting paperwork, and a Risk Management Plan screen for ammonia. That is why the input Cliff needs is a specific land parcel plus a specific generation stack, not a generic "data center" tag.
The hard part is not finding one rule. It is carrying the Texas pre-construction track, the federal equipment-order dates, the county's attainment status, and the sitewide aggregation (multiple buildings on one parcel can be treated as one big source) through to a single auditable answer.
Worked demos
Two real Texas data-center builds produce very different permit stacks
Longhorn (Crusoe's Abilene site) shows a campus that cleared the fast Texas Standard Permit for its first 360 MW of behind-the-meter turbines, then crossed into the slower federal PSD (Prevention of Significant Deterioration) review when it tried to add two more buildings. Goodnight is the all-at-once version: TCEQ project 404507 is already a case-by-case NSR plus PSD plus greenhouse-gas PSD application, with a full atmospheric dispersion modeling protocol, because the proposed plant is nearly a gigawatt from day one.
Abilene / Taylor County, Texas
Longhorn Data Center
Issued standard permit + PBR + Title V; expansion pending PSD
Generation stack
- 360.5 MW natural-gas simple-cycle turbines under Standard Permit 177263
- 169.9 MW emergency diesel fleet under PBR 177262 after the April 2025 revision
- Buildings 9 and 10 pending under 182126 / PSDTX1688 / GHGPSDTX263
Required stack
- Texas: PI-1S standard-permit route for first turbine block, PBR route for emergency engines/tanks, Title V SOP O4721, PSD/GHG PSD for the expansion.
- Federal: NSPS KKKK for existing turbines, KKKK/KKKKa date check for new turbine work, NSPS IIII and MACT ZZZZ for emergency RICE, Part 70 Title V.
Public emissions signal
The first 360 MW can look cleanly authorizable, while the next two buildings turn into public-notice PSD. The risk is permit class, not only runtime.
Claude / Armstrong County, Texas
Goodnight Data Center
Pending initial NSR, PSD, and GHG PSD application
Generation stack
- 20 x 46.645 MW natural-gas turbines: 13 ProEnergy LM6000 and 7 Aero DT46
- 170 x 3 MW Cat 3516 emergency backup generators plus 10 black-start generators
- SCR, oxidation catalyst, ammonia tank, diesel and lube-oil tank systems
Required stack
- Texas: case-by-case initial NSR 182880 with PSDTX1698 and GHGPSDTX268, public notice, expedited-program flag, modeling protocol and BACT package.
- Federal: KKKKa for new turbines, IIII and ZZZZ for diesel RICE, Part 70 FOP expected, Part 98 GHG reporting, Part 68 ammonia RMP screen.
Public emissions signal
This is the all-at-once version of the Longhorn expansion cliff: a parcel in attainment territory still lands in PSD and GHG PSD because the generation stack is nearly a gigawatt.
Primary sources
Every step of the tree is anchored in TCEQ, EPA, and eCFR records
TCEQ's pending-notice page lists every air permit currently in public review. EPA's Green Book is the official list of which US counties are in attainment for each pollutant. eCFR (the Electronic Code of Federal Regulations) is the live, official text of the federal rules referenced above.
Goodnight status was checked through TCEQ's permit-status search for permit 182880: pending, project 404507, received January 30, 2026, in Armstrong County. The Longhorn permit history is walked through step by step in the Longhorn walkthrough.
Air-permit underwriting
Send a parcel and a list of generators. Get back the actual permit file.
Cliff maps the Texas pre-construction track, the federal equipment rules, the required forms, public notice, dispersion modeling, and operating-permit obligations against the primary regulatory sources.