# Relationship history for MSHA mine 1509699

Current hierarchy: **Blair Douglas L → Richland Coal Company → No 2 Surface**

- 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:** Blair Douglas L → No 2 Surface; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Richland Coal Company → No 2 Surface; 1976-04-28 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Blair Douglas L → Richland Coal Company; 1976-04-28 to current/open; source msha-controller-operator-history