9.8-mile natural gas trunk crossing Galveston Bay between Bayport (refinery shoreline) and Bolivar Peninsula. Subsidence zones marked along the subsea midcrossing and shoreline approaches.
Galveston Bay subsea crossing is impacted by active subsidence with high displacement rate at the midcrossing and refinery-side shoreline. Planned mitigation should be advanced in the next maintenance window.
| Operator | Enterprise Products |
|---|---|
| Commodity | Natural Gas |
| Diameter | 24 in |
| Length | 9.8 mi |
| HCA Proximity | 1.4 mi |
| Geohazard Classification | subsidence |
| Screening Result | Escalate to targeted Tier 2 monitoring |
| Period (days) | Samples | Mean Displacement (mm) | Max Velocity (mm/yr) | Min Velocity (mm/yr) | Mean Coherence |
|---|---|---|---|---|---|
| 365 | 30 | -18.5 | -24.3 | -8.1 | 0.72 |
Velocity Trends: Observed range -8.1 to -24.3 mm/yr across monitoring windows. Consistent subsidence signal over 12 months.
Acceleration Flags: No elevated acceleration flag. Acceleration contribution is 0.15.
high confidence — 30 observations over 365 days, mean coherence 0.72, uncertainty ±1.8 mm.
| Risk Factor | Weight | Contribution |
|---|---|---|
| Acceleration | 0.15 | 15% |
| Displacement Rate | 0.25 | 25% |
| Criticality | 0.22 | 22% |
| Condition | 0.10 | 10% |
| Geology | 0.18 | 18% |
| Context | 0.10 | 10% |
Mitigation Recommendations: Schedule right-of-way survey confirmation, run geodetic tie checks, and prioritize block-valve segment review for areas with peak subsidence rates.
| Section | Severity | Description | Location | Date |
|---|---|---|---|---|
| MP 3.5–5.6 | Warning | Subsidence rate exceeds 20 mm/yr along the subsea midcrossing | Segment TX-GC-SEG-0089 | 2026-02-18 |
| Source | Frames | Date Range | Processing |
|---|---|---|---|
| Sentinel-1 C-band InSAR | F38239 | 2025-03-05 to 2026-03-05 | OPERA DISP-S1 v1.1 (NASA/JPL via ASF) |