# Relationship history for MSHA mine 2500990

Current hierarchy: **Don  Kellogg → Mid-West Bridge & Construction Company → Volkman**

- 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:** Don  Kellogg → Volkman; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kahler Robert → Volkman; 1978-03-09 to 1985-01-13; source msha-controller-operator-history
- **operator_operates_mine:** Kahler Construction Company → Volkman; 1981-04-01 to 1984-04-30; source msha-controller-operator-history
- **controller_controls_operator:** Kahler Robert → Kahler Construction Company; 1981-04-01 to 1984-04-30; source msha-controller-operator-history
- **operator_operates_mine:** Mid-West Bridge & Construction Company → Volkman; 1984-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Don  Kellogg → Mid-West Bridge & Construction Company; 1984-05-01 to current/open; source msha-controller-operator-history