# Relationship history for MSHA mine 2501180

Current hierarchy: **Glenn D Olmstead → Overton Sand & Gravel → Johnson Sand Pit**

- 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

- **controller_controls_mine:** Glenn D Olmstead et al → Johnson Sand Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Overton Sand & Gravel → Johnson Sand Pit; 1998-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Glenn D Olmstead et al → Overton Sand & Gravel; 1998-07-01 to current/open; source msha-controller-operator-history