Research case study - May 1, 2026
A 360 MW BTM plant cleared. The next expansion hit PSD.
Longhorn Data Center in Abilene is Cliff's first end-to-end air-permit walkthrough. The surprise is not a RICE runtime de-rate. It is a permit-class cliff: standard permit at the first turbine block, issued Title V operating permit at the site, and PSD / GHG PSD review at the next two buildings.
- Main plant
- 360.5 MW
- Permit record
- 177263 / O4721
- Expansion docket
- PSDTX1688
Permit path
Standard permit to PSD in five public records
Aug 2024
Standard Permit 177263
420 MW nominal turbine layout: six Titan 350 at 8,760 hr/yr and six LM2500 at 5,880 hr/yr.
Jan 2025
177263 modified
Nameplate falls to 360.5 MW, but all ten turbines move to 8,760 hr/yr represented availability.
Apr 2025
177262 expanded
Emergency diesel PBR grows to 169.9 MW of nameplate, mostly represented at 150 hr/yr.
Jan 2026
FOP O4721 effective
Issued Title V SOP codifies the site as major for VOC, NOx, and CO.
Nov 2025+
182126 / PSDTX1688
Buildings 9 and 10 generation remains pending in NSR, PSD, and GHG PSD; 182267 fuel-switch filing was withdrawn.
Equipment
The RICE layer exists, but it is not the main plant
The large 360.5 MW block is ten simple-cycle combustion turbines covered by NSPS KKKK. RICE NESHAP and NSPS IIII apply to the emergency diesel generator fleet under PBR 177262, which grew to 169.9 MW of nameplate in an April 2025 revision. Applying a diesel-backup de-rate calculator to the turbine plant would produce the wrong answer.
| Layer | Equipment | Capacity | Permit hours | Federal rule |
|---|---|---|---|---|
| Main plant | 5 x Solar Titan 350 | 190 MW | 8,760 hr/yr | NSPS KKKK |
| Main plant | 5 x GE LM2500 | 170.5 MW | 8,760 hr/yr | NSPS KKKK |
| Emergency | 6 x Cat C175 Tier II | 18 MW | 100-150 hr/yr | NSPS IIII / MACT ZZZZ |
| Emergency | 9 x Cat 3516 Tier IV | 18 MW | 100-150 hr/yr | NSPS IIII / MACT ZZZZ |
| Emergency | 3 x Cat 3516 Tier II | 7.5 MW | 150 hr/yr | NSPS IIII / MACT ZZZZ |
| Emergency | 16 x Cat 3516 Tier IV | 48 MW | 150 hr/yr | NSPS IIII / MACT ZZZZ |
| Emergency | 28 x Baudouin Tier IV | 78.4 MW | 150 hr/yr | NSPS IIII / MACT ZZZZ |
Permit math
The constraint moved from hours to permit class
In the January 2025 modification, GE LM2500 annual hours moved from 5,880 to 8,760 while turbine count fell. That improves firm-equivalent onsite capacity. But the sitewide emissions story then moves into an issued Title V SOP, and Buildings 9 and 10 remain pending in PSD / GHG PSD review.
177263 + Apr PBR PTE
182126 proposed expansion
The 177263 values combine the standard-permit turbine block from the Pinyon modification application and the April 2025 PBR emergency-source revision. The 182126 values are from TCEQ's plain-language summary for the pending Buildings 9 and 10 NSR / PSD / GHG PSD application.
TCEQ status search was rechecked on May 1, 2026: O4721 is effective, 182126 remains pending, and 182267 is withdrawn.
Cliff read
The underwriting question is not just "how many MW?"
A conventional model sees a 24/7 onsite plant and treats it as capacity. The air record says something more useful: 360.5 MW can be standard-permit feasible, but the next building pair can cross into public-notice PSD. The withdrawn 182267 fuel-switch filing also shows that resilience choices can become their own permit surface. The schedule risk is not linear with MW.
That is why Cliff's de-rate work needs two branches. Diesel backup fleets need the RICE NESHAP runtime model. BTM turbine plants need an NSPS KKKK/KKKKa, Title V, PSD, and fuel-switching model. Longhorn is the primary-source proof that both branches matter.
Primary sources
Every claim traces back to TCEQ records
The consultant of record for the 177263 modification was Pinyon Environmental. The same public record shows the issued Title V permit, emergency generator PBR revisions, pending PSD filing, and withdrawn fuel-switch notice.
- TCEQ 177263 technical reviewSource
- Pinyon 177263 modification applicationSource
- TCEQ PBR 177262 technical reviewSource
- TCEQ PBR 177262 April revisionSource
- TCEQ FOP O4721 issued permitSource
- TCEQ FOP O4721 Statement of BasisSource
- TCEQ 182126 plain-language summarySource
- TCEQ 182267 fuel-switch noticeSource
- TCEQ permit status searchSource
- Crusoe Abilene 3 announcementSource
- EPA NSPS KKKKa current ruleSource
Background context: Crusoe announced a separate 900 MW Microsoft AI factory campus in Abilene on March 27, 2026, with an onsite power plant and MV BESS. The pending 182126 notice identifies Longhorn Buildings 9 and 10 at the same TCEQ coordinates, but the public notice itself does not state MW. Read Crusoe's announcement.
Air-permit underwriting
Send a permit number. Get the actual constraint stack.
Cliff reads the permit, equipment list, emissions tables, and interconnection product together.