# Relationship history for MSHA mine 3002816

Current hierarchy: **Zahn'S Sand & Gravel → Zahn'S Sand & Gravel → Zahn'S Sand And 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: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** Zahn'S Sand & Gravel → Zahn'S Sand And Gravel; 1987-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Zahn'S Sand & Gravel → Zahn'S Sand And Gravel; 1987-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Zahn'S Sand & Gravel → Zahn'S Sand & Gravel; 1987-10-01 to current/open; source msha-controller-operator-history