# Relationship history for MSHA mine 2501117

Current hierarchy: **K & B Gravel Company → K & B Gravel Company → K & B Gravel Company**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** K & B Gravel Company → K & B Gravel Company; 1989-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** K & B Gravel Company → K & B Gravel Company; 1989-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** K & B Gravel Company → K & B Gravel Company; 1989-11-01 to current/open; source msha-controller-operator-history