# Relationship history for MSHA mine 3101715

Current hierarchy: **Sanford Grading Company → Sanford Grading Company → Thomas Farm Gravel**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Sanford Grading Company → Thomas Farm Gravel; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Sanford Grading Company → Thomas Farm Gravel; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Sanford Grading Company → Sanford Grading Company; 1950-01-01 to current/open; source msha-controller-operator-history