# Relationship history for MSHA mine 2902092

Current hierarchy: **Richard A  Alexander → Mesa Gravel Inc → Portable #1**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Mesa Gravel Inc → Portable #1; 1992-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Richard A  Alexander  et al → Portable #1; 1992-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Richard A  Alexander  et al → Mesa Gravel Inc; 1992-04-01 to current/open; source msha-controller-operator-history