# Relationship history for MSHA mine 2001618

Current hierarchy: **Alice  Veldkamp → Great Lakes Gravel → Great Lakes Pit & Mill**

- 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:** Great Lakes Gravel Company Inc → Great Lakes Pit & Mill; 1950-01-01 to 1985-08-27; source msha-controller-operator-history
- **controller_controls_mine:** Abercrombie Roy → Great Lakes Pit & Mill; 1950-01-01 to 1985-08-27; source msha-controller-operator-history
- **controller_controls_operator:** Abercrombie Roy → Great Lakes Gravel Company Inc; 1950-01-01 to 1985-08-27; source msha-controller-operator-history
- **operator_operates_mine:** Great Lakes Gravel → Great Lakes Pit & Mill; 1985-08-28 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Alice  Veldkamp → Great Lakes Pit & Mill; 1985-08-28 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Alice  Veldkamp → Great Lakes Gravel; 1985-08-28 to current/open; source msha-controller-operator-history