# Relationship history for MSHA mine 4606015

Current hierarchy: **Halstead P J → Rio Coal Company Inc → River Dredge**

- 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:** Ferrellsburg Sand & By-Products Inc → River Dredge; 1979-06-01 to 1984-03-21; source msha-controller-operator-history
- **controller_controls_mine:** Crum Joe Jr → River Dredge; 1979-06-01 to 1984-03-21; source msha-controller-operator-history
- **controller_controls_operator:** Crum Joe Jr → Ferrellsburg Sand & By-Products Inc; 1979-06-01 to 1984-03-21; source msha-controller-operator-history
- **operator_operates_mine:** Rio Coal Company Inc → River Dredge; 1984-03-22 to 1987-06-23; source msha-controller-operator-history
- **controller_controls_mine:** Koogler David → River Dredge; 1984-03-22 to 1987-06-23; source msha-controller-operator-history
- **controller_controls_operator:** Koogler David → Rio Coal Company Inc; 1984-03-22 to 1987-06-23; source msha-controller-operator-history
- **operator_operates_mine:** Rio Coal Company Inc → River Dredge; 1987-06-24 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Halstead P J → River Dredge; 1987-06-24 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Halstead P J → Rio Coal Company Inc; 1987-06-24 to current/open; source msha-controller-operator-history