# Relationship history for MSHA mine 2500279

Current hierarchy: **CRH PLC → Central Sand & Gravel Company → PORTABLE #7**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Central Sand & Gravel Company → PORTABLE #7; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Ash Grove Cement Company → PORTABLE #7; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Central Sand & Gravel Company; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → PORTABLE #7; 2018-06-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Central Sand & Gravel Company; 2018-06-21 to current/open; source msha-controller-operator-history