# Relationship history for MSHA mine 4502919

Current hierarchy: **Martin  Drollinger; William  Douglas → Valley Ready Mix Concrete Company → SO HAPPY PIT & PLANT**

- 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:** Martin  Drollinger  et al → SO HAPPY PIT & PLANT; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Valley Ready Mix Concrete Company → SO HAPPY PIT & PLANT; 1981-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin  Drollinger  et al → Valley Ready Mix Concrete Company; 1981-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** William  Douglas  et al → Valley Ready Mix Concrete Company; 1981-05-01 to current/open; source msha-controller-operator-history