# Relationship history for MSHA mine 4702552

Current hierarchy: **Dennis L  Nordstrand → Yellow River Supply Corp → Robarge Pit**

- 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:** Milton D  Ostermann → Robarge Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** H & W Sand & Gravel Company → Robarge Pit; 1978-03-09 to 1979-05-08; source msha-controller-operator-history
- **controller_controls_mine:** Hantsman Lester Et Al → Robarge Pit; 1978-03-09 to 1979-05-08; source msha-controller-operator-history
- **controller_controls_operator:** Hantsman Lester Et Al → H & W Sand & Gravel Company; 1978-03-09 to 1979-05-08; source msha-controller-operator-history
- **operator_operates_mine:** Ostermann Sand & Gravel Inc → Robarge Pit; 1979-05-09 to 1984-02-16; source msha-controller-operator-history
- **controller_controls_operator:** Milton D  Ostermann → Ostermann Sand & Gravel Inc; 1979-05-09 to 1984-02-16; source msha-controller-operator-history
- **operator_operates_mine:** Yellow River Supply Corp → Robarge Pit; 1984-02-17 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Dennis L  Nordstrand → Robarge Pit; 1984-02-17 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dennis L  Nordstrand → Yellow River Supply Corp; 1984-02-17 to current/open; source msha-controller-operator-history