# Relationship history for MSHA mine 4200998

Current hierarchy: **Scott  Simplot → Simplot Phosphates LLC → Vernal Pit & Mill**

- 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:** Stauffer Chemical Company → Vernal Pit & Mill; 1950-01-01 to 1981-02-22; source msha-controller-operator-history
- **controller_controls_mine:** Unilever United States Inc → Vernal Pit & Mill; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Unilever United States Inc → Stauffer Chemical Company; 1950-01-01 to 1981-02-22; source msha-controller-operator-history
- **operator_operates_mine:** Chevron Chemical Company → Vernal Pit & Mill; 1981-02-23 to 1992-06-29; source msha-controller-operator-history
- **controller_controls_mine:** Chevron Corporation → Vernal Pit & Mill; 1981-02-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Chevron Corporation → Chevron Chemical Company; 1981-02-23 to 1992-06-29; source msha-controller-operator-history
- **operator_operates_mine:** Simplot Phosphates LLC → Vernal Pit & Mill; 1992-06-30 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Simplot J R Company & Farmland Industries → Vernal Pit & Mill; 1992-06-30 to 2003-11-09; source msha-controller-operator-history
- **controller_controls_operator:** Simplot J R Company & Farmland Industries → Simplot Phosphates LLC; 1992-06-30 to 2003-11-09; source msha-controller-operator-history
- **controller_controls_mine:** Scott  Simplot → Vernal Pit & Mill; 2003-11-10 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Scott  Simplot → Simplot Phosphates LLC; 2003-11-10 to current/open; source msha-controller-operator-history