Research note - May 1, 2026
Given any Texas parcel, what air permits does the power stack need?
The answer is not a single permit name. It is a decision graph: parcel status, equipment, emissions potential, Texas NSR route, public notice, modeling, Title V, and federal equipment rules. The demos below run that graph against two public Texas data-center builds.
- State layer
- TCEQ NSR + Title V
- Federal layer
- Part 70 + NSPS + MACT
- Demos
- Longhorn + Goodnight
Decision graph
The permit answer starts before emissions math
A parcel in Dallas-Fort Worth, Houston-Galveston-Brazoria, Beaumont-Port Arthur, or another nonattainment branch can produce a different answer than the same stack in Armstrong County. A turbine ordered after December 13, 2024 can produce a different federal answer than one already covered under NSPS KKKK. The model has to carry those facts through the whole file.
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 output
Forms, notice, and modeling are determined by the NSR route
TCEQ separates preconstruction authorization from operating permits. The same project can need a PBR for emergency engines, a standard permit or case-by-case NSR for turbines, public notice if the application class requires it, and a separate Title V filing after the site becomes a Part 70 source.
| 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 overlay
The federal rules are equipment-specific
Diesel backup is the NSPS IIII / MACT ZZZZ branch. Combustion turbines are the KKKK or KKKKa branch. The Title V branch is sitewide. SCR ammonia, GHG reporting, and nonattainment status add their own checks before a 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 rule-to-file map.
A useful answer has to name the missing attachments: PI-7 or PI-1S, PI-1 tables, OP forms, PIP, public notice verification, modeling protocol, BACT analysis, emissions inventory, GHG reporting, and RMP screen. That is why the input is a parcel plus a generation stack, not a generic "data center" label.
The hard part is not finding one rule. It is keeping the Texas preconstruction route, federal equipment dates, county attainment status, and sitewide aggregation in one auditable answer.
Worked demos
Two Texas data-center builds produce different permit stacks
Longhorn proves that a site can clear an initial BTM turbine block and still hit Title V / PSD at expansion. Goodnight is the larger front-door case: TCEQ project 404507 is already an initial NSR, PSD, and GHG PSD application with a modeling protocol.
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
The tree is anchored in TCEQ, EPA, and eCFR
TCEQ's pending-notice page supplies the live public records. EPA's Green Book supplies attainment status. eCFR supplies the current federal rule text.
Goodnight status was checked through TCEQ's NSR/FOP search for permit 182880: pending, project 404507, received January 30, 2026, Armstrong County. Longhorn status is detailed in the Longhorn walkthrough.
Air-permit underwriting
Send a parcel and a stack. Get the required permit file.
Cliff maps the Texas NSR route, federal rules, forms, public notice, modeling, and Title V obligations against primary sources.